Fibrin(ogen) engagement of S. aureus promotes the host antimicrobial response and suppression of microbe dissemination following peritoneal infection.

The blood-clotting protein fibrin(ogen) plays a critical role in host defense against invading pathogens, particularly against peritoneal infection by the Gram-positive microbe Staphylococcus aureus. Here, we tested the hypothesis that direct binding between fibrin(ogen) and S. aureus is a component of the primary host antimicrobial response mechanism and prevention of secondary microbe dissemination from the peritoneal cavity. To establish a model system, we showed that fibrinogen isolated from FibγΔ5 mice, which express a mutant form lacking the final 5 amino acids of the fibrinogen γ chain (termed fibrinogenγΔ5), did not support S. aureus adherence when immobilized and clumping when in suspension. In contrast, purified wildtype fibrinogen supported robust adhesion and clumping that was largely dependent on S. aureus expression of the receptor clumping factor A (ClfA). Following peritoneal infection with S. aureus USA300, FibγΔ5 mice displayed worse survival compared to WT mice coupled to reduced bacterial killing within the peritoneal cavity and increased dissemination of the microbes into circulation and distant organs. The failure of acute bacterial killing, but not enhanced dissemination, was partially recapitulated by mice infected with S. aureus USA300 lacking ClfA. Fibrin polymer formation and coagulation transglutaminase Factor XIII each contributed to killing of the microbes within the peritoneal cavity, but only elimination of polymer formation enhanced systemic dissemination. Host macrophage depletion or selective elimination of the fibrin(ogen) ß2-integrin binding motif both compromised local bacterial killing and enhanced S. aureus systemic dissemination, suggesting fibrin polymer formation in and of itself was not sufficient to retain S. aureus within the peritoneal cavity. Collectively, these findings suggest that following peritoneal infection, the binding of S. aureus to stabilized fibrin matrices promotes a local, macrophage-mediated antimicrobial response essential for prevention of microbe dissemination and downstream host mortality.

Coagulase-negative staphylococci from bovine milk: Antibiogram profiles and virulent gene detection.

BACKGROUND: Coagulase-negative Staphylococcus species are an emerging cause of intramammary infection, posing a significant economic and public health threat. The aim of this study was to assess the occurrence of coagulase-negative Staphylococcus species in bovine milk and dairy farms in Northwestern Ethiopia and to provide information about their antibiotic susceptibility and virulence gene profiles. METHODS: The cross-sectional study was conducted from February to August 2022. Coagulase-negative Staphylococcus species were isolated from 290 milk samples. Species isolation and identification were performed by plate culturing and biochemical tests and the antimicrobial susceptibility pattern of each isolate was determined by the Kirby-Bauer disc diffusion test. The single-plex PCR was used to detect the presence of virulent genes. The STATA software version 16 was used for data analysis. The prevalence, proportion of antimicrobial resistance and the number of virulent genes detected from coagulase-negative Staphylococcus species were analyzed using descriptive statistics. RESULTS: Coagulase-negative Staphylococcus species were isolated in 28.6%, (95% CI: 23.5-34.2) of the samples. Of these, the S. epidermidis, S. sciuri, S. warneri, S. haemolyticus, S. simulans, S. chromogens, S. cohnii, and S. captis species were isolated at the rates of 11, 5.2, 3.4, 3.1, 3.1, 1, 1, and 0.7% respectively. All the isolates showed a high percentage (100%) of resistance to Amoxicillin, Ampicillin, and Cefotetan and 37.5% of resistance to Oxacillin. The majority (54.2%) of coagulase-negative isolates also showed multidrug resistance. Coagulase-negative Staphylococcus species carried the icaD, pvl, mecA, hlb, sec, and hla virulent genes at the rates of 26.5%, 22.1%, 21.7%, 9.6%, 9.6% and 8.4% respectively. CONCLUSION: The present study revealed that the majority of the isolates (54.2%) were found multidrug-resistant and carriage of one or more virulent and enterotoxin genes responsible for intramammary and food poisoning infections. Thus, urgent disease control and prevention measures are warranted to reduce the deleterious impact of coagulase-negative species. To the best of our knowledge, this is the first study in Ethiopia to detect coagulase-negative Staphylococcus species with their associated virulent and food poisoning genes from bovine milk.

Occurrence, antimicrobial susceptibility, and resistance genes of Staphylococcus aureus in milk and milk products in the Arsi highlands of Ethiopia.

BACKGROUND: In Ethiopia, milk production and handling practices often lack proper hygiene measures, leading to the potential contamination of milk and milk products with Staphylococcus aureus (S. aureus), including methicillin-resistant strains, posing significant public health concerns. This study aimed to investigate the occurrence, antimicrobial susceptibility profiles and presence of resistance genes in S. aureus strains isolated from milk and milk products. METHODS: A cross-sectional study was conducted in the Arsi highlands, Oromia, Ethiopia from March 2022 to February 2023. A total of 503 milk and milk product samples were collected, comprising 259 raw milk, 219 cottage cheese, and 25 traditional yogurt samples. S. aureus isolation and coagulase-positive staphylococci enumeration were performed using Baird-Parker agar supplemented with tellurite and egg yolk. S. aureus was further characterized based on colony morphology, Gram stain, mannitol fermentation, catalase test, and coagulase test. Phenotypic antimicrobial resistance was assessed using the Kirby-Bauer disc diffusion method, while the polymerase chain reaction (PCR) was employed for confirming the presence of S. aureus and detecting antimicrobial resistance genes. RESULTS: S. aureus was detected in 24.9% of the milk and milk products, with the highest occurrence in raw milk (40.9%), followed by yogurt (20%), and cottage cheese (6.4%). The geometric mean for coagulase-positive staphylococci counts in raw milk, yogurt, and cottage cheese was 4.6, 3.8, and 3.2 log10 CFU/mL, respectively. Antimicrobial resistance analysis revealed high levels of resistance to ampicillin (89.7%) and penicillin G (87.2%), with 71.8% of the isolates demonstrating multidrug resistance. Of the 16 S. aureus isolates analyzed using PCR, all were found to carry the nuc gene, with the mecA and blaZ genes detected in 50% of these isolates each. CONCLUSION: This study revealed the widespread distribution of S. aureus in milk and milk products in the Arsi highlands of Ethiopia. The isolates displayed high resistance to ampicillin and penicillin, with a concerning level of multidrug resistance. The detection of the mecA and blaZ genes in selected isolates is of particular concern, highlighting a potential public health hazard and posing a challenge to effective antimicrobial treatment. These findings highlight the urgent need to enhance hygiene standards in milk and milk product handling and promote the rational use of antimicrobial drugs. Provision of adequate training for all individuals involved in the dairy sector can help minimize contamination. These measures are crucial in addressing the threats posed by S. aureus, including methicillin-resistant strains, and ensuring the safety of milk and its products for consumers.

Atopic dermatitis pediatric patients show high rates of nasal and intestinal colonization by methicillin-resistant Staphylococcus aureus and coagulase-negative staphylococci.

BACKGROUND: Atopic dermatitis (AD) patients have high rates of colonization by Staphylococcus aureus, which has been associated with worsening of the disease. This study characterized Staphylococcus spp isolates recovered from nares and feces of pediatric patients with AD in relation to antimicrobial susceptibility, staphylococcal cassette chromosome mec (SCCmec) type, presence of pvl genes and clonality. Besides, gut bacterial community profiles were compared with those of children without AD. RESULTS: All 55 AD patients evaluated had colonization by Staphylococcus spp. Fifty-three (96.4%) patients had colonization in both clinical sites, whereas one patient each was not colonize in the nares or gut. Staphylococcus aureus was identified in the nostrils and feces of 45 (81.8%) and 39 (70.9%) patients, respectively. Methicillin-resistant Staphylococcus spp. isolates were found in 70.9% of the patients, and 24 (43.6%) had methicillin-resistant S. aureus (MRSA). S. aureus (55.6%) and S. epidermidis (26.5%) were the major species found. The prevalent lineages of S. aureus were USA800/SCCmecIV (47.6%) and USA1100/SCCmecIV (21.4%), and 61.9% of the evaluated patients had the same genotype in both sites. Additionally, gut bacterial profile of AD patients exhibits greater dissimilarity from the control group than it does among varying severities of AD. CONCLUSIONS: High rates of nasal and intestinal colonization by S. aureus and methicillin-resistant staphylococci isolates were found in AD patients. Besides, gut bacterial profiles of AD patients were distinctly different from those of the control group, emphasizing the importance of monitoring S. aureus colonization and gut microbiome composition in AD patients.

Incidence of uterine infections, major bacteria and antimicrobial resistance in postpartum dairy cows in southern Ethiopia.

BACKGROUND: Uterine infections, primarily caused by bacterial pathogens, pose a significant problem for dairy farmers worldwide, leading to poor reproductive performance and economic losses. However, the bacteria responsible for uterine infections have not been adequately studied, nor has the antibiotic susceptibility of the causative bacteria been frequently tested in Ethiopia. This study aims to estimate the cumulative incidence of uterine infections in postpartum dairy cows, identify bacterial causes and determine antimicrobial susceptibility profile of the isolated bacteria. METHODS: A prospective cohort study was conducted in which 236 cows from 74 dairy farms were monitored biweekly from calving to 90 days postpartum for metritis, endometritis and other disorders. Aseptic uterine swab samples were collected from 40 cows with uterine infections. The samples were cultured, and the isolated bacteria were tested for antimicrobial susceptibility using the disk diffusion method. RESULTS: Out of 236 cows monitored during the postpartum phase, 45 (19.1%) were found to have contracted uterine infection. The cumulative incidence of metritis was 11.4% (n = 27), while the cumulative incidence of endometritis was 7.6% (n = 18). Of the 40 cultured swab samples, 29 (72.5%) had one or more bacteria isolated. The most commonly isolated bacteria were Escherichia coli (45%), coagulase-positive staphylococci (30%), and Klebsiella spp. (22.5%). Other bacterial spp, including Arcanobacterium pyogenes (12.5%), Fusobacterium spp. (12.5%), Enterobacter aerogenes (12.5%), coagulase-negative staphylococci (12.5%), Streptococcus spp. (7.5%), Salmonella spp, (5%) Proteus spp (5%) and Pasteurella spp (2.5%) were also isolated. All of the isolated bacteria demonstrated resistance to at least one of the antimicrobials tested. Multidrug resistance was observed in E. coli, Klebsiella spp., A. pyogenes, and Fusobacterium spp. Gentamicin was found to be the most effective antimicrobial against all bacteria tested, while tetracycline was the least effective of all. CONCLUSION: The study found that a significant proportion of cows in the population were affected by uterine infections and the isolated bacteria developed resistance to several antimicrobials. The study emphasizes the need for responsible use of antimicrobials to prevent the emergence of antimicrobial resistance. It also highlights the importance of raising awareness among dairy farmers to avoid the indiscriminate use of antibiotics and its consequences.

Comparing ethanol lock therapy versus vancomycin lock in a salvation strategy for totally implantable vascular access device infections due to coagulase-negative staphylococci (the ETHALOCK study): a prospective double-blind randomized clinical trial.

OBJECTIVES: Little is known about efficacy and safety of ethanol lock therapy (ELT) to treat totally implantable venous access device (TIVAD) infections. The objective of this trial was to evaluate the effectiveness and safety profile of a local treatment with ELT without removal for TIVAD infection due to coagulase-negative staphylococci. METHODS: We performed a prospective, multicenter, double-blind, randomized clinical trial comparing the efficacy of 40% ELT versus vancomycin lock therapy (VLT) in TIVAD infections due to coagulase-negative staphylococci, complicated or not by bloodstream infection. RESULTS: Thirty-one patients were assigned to the ELT group and 30 to the VLT arm. Concomitant bacteremia was present in 41 patients (67.2%). Treatment success was 58.1 % (18 of 31) for the ELT arm and 46.7% (14 of 30) for the VLT arm (p = 0.37). The overall treatment success was 52.5% (32). The risk of treatment failure due to uncontrolled infections, superinfections, and mechanical complications did not differ significantly between participants receiving ELT (13 out of 31 [42%]) and those receiving VLT (16 out of 30 [53%]) with a hazard ratio of 0.70 (p = 0.343; 95% CI [0.34-1.46], Cox model). Catheter malfunctions were significantly more frequent in the ELT arm (11 patients versus 2 in the VLT group, p = 0.01). CONCLUSIONS: We found an overall high rate of treatment failure that did not differ between the ELT arm and the VLT arm. TIVAD removal must be prioritized to prevent complications (uncontrolled infections, superinfections, and catheter malfunctions) except in exceptional situations.

Characterization of linezolid- and methicillin-resistant coagulase-negative staphylococci in a tertiary hospital in China.

BACKGROUND: Recently, linezolid-resistant staphylococci have become an emerging problem worldwide. Understanding the mechanisms of resistance, molecular epidemiology and transmission of linezolid-resistant CoNS in hospitals is very important. METHODS: The antimicrobial susceptibilities of all isolates were determined by the microdilution method. The resistance mechanisms and molecular characteristics of the strains were determined using whole-genome sequencing and PCR. RESULTS: All the strains were resistant to oxacillin and carried the mecA gene; 13 patients (36.1%) had prior linezolid exposure. Most S. epidermidis and S. hominis isolates were ST22 and ST1, respectively. MLST typing and evolutionary analysis indicated most linezolid-resistant CoNS strains were genetically related. In this study, we revealed that distinct CoNS strains have different mechanisms of linezolid resistance. Among ST22-type S. epidermidis, acquisition of the T2504A and C2534T mutations in the V domain of the 23 S rRNA gene, as well as mutations in the ribosomal proteins L3 (L101V, G152D, and D159Y) and L4 (N158S), were linked to the development of linezolid resistance. In S. cohnii isolates, cfr, S158Y and D159Y mutations in the ribosomal protein L3 were detected. Additionally, emergence of the G2576T mutation and the cfr gene were major causes of linezolid resistance in S. hominis isolates. The cfr gene, G2576T and C2104T mutations, M156T change in L3 protein, and I188S change in L4 protein were found in S. capitis isolates. CONCLUSION: The emergence of linezolid-resistant CoNS in the environment is concerning because it involves clonal dissemination and frequently coexists with various drug resistance mechanisms.

Anti-virulence potential of iclaprim, a novel folic acid synthesis inhibitor, against Staphylococcus aureus.

Infections caused by Staphylococcus aureus pose a significant global public problem. Therefore, new antibiotics and therapeutic strategies are needed to combat this pathogen. This investigation delves into the effects of iclaprim, a newly discovered inhibitor of folic acid synthesis, on S. aureus virulence. The phenotypic and genotypic effects of iclaprim were thoroughly examined in relation to virulence factors, biofilm formation, and dispersal, as well as partial virulence-encoding genes associated with exoproteins, adherence, and regulation in S. aureus MW2, N315, and ATCC 25923. Then, the in vivo effectiveness of iclaprim on S. aureus pathogenicity was explored by a Galleria mellonella larvae infection model. The use of iclaprim at sub-inhibitory concentrations (sub-MICs) resulted in a reduction of α-hemolysin (Hla) production and a differential effect on the activity of coagulase in S. aureus strains. The results of biofilm formation and eradication assay showed that iclaprim was highly effective in depolymerizing the mature biofilm of S. aureus strains at concentrations of 1 MIC or greater, however, inhibited the biofilm-forming ability of only strains N315 and ATCC 25923 at sub-MICs. Interestingly, treatment of strains with sub-MICs of iclaprim resulted in significant stimulation or suppression of most virulence-encoding genes expression. Iclaprim did not affect the production of δ-hemolysin or staphylococcal protein A (SpA), nor did it impact the total activity of proteases, nucleases, and lipases. In vivo testing showed that sub-MICs of iclaprim significantly improves infected larvae survival. The present study offered valuable insights towards a better understating of the influence of iclaprim on different strains of S. aureus. The findings suggest that iclaprim may have potential as an anti-virulence and antibiofilm agent, thus potentially mitigating the pathogenicity of S. aureus and improving clinical outcomes associated with infections caused by this pathogen. KEY POINTS: • Iclaprim effectively inhibits α-hemolysin production and biofilm formation in a strain-dependent manner and was an excellent depolymerizing agent of mature biofilm • Iclaprim affected the mRNA expression of virulence-encoding genes associated with exoproteins, adherence, and regulation • In vivo study in G. mellonella larvae challenged with S. aureus exhibited that iclaprim improves larvae survival.

Host fibrinogen drives antimicrobial function in Staphylococcus aureus peritonitis through bacterial-mediated prothrombin activation.

The blood-clotting protein fibrinogen has been implicated in host defense following Staphylococcus aureus infection, but precise mechanisms of host protection and pathogen clearance remain undefined. Peritonitis caused by staphylococci species is a complication for patients with cirrhosis, indwelling catheters, or undergoing peritoneal dialysis. Here, we sought to characterize possible mechanisms of fibrin(ogen)-mediated antimicrobial responses. Wild-type (WT) (Fib+) mice rapidly cleared S. aureus following intraperitoneal infection with elimination of ∼99% of an initial inoculum within 15 min. In contrast, fibrinogen-deficient (Fib-) mice failed to clear the microbe. The genotype-dependent disparity in early clearance resulted in a significant difference in host mortality whereby Fib+ mice uniformly survived whereas Fib- mice exhibited high mortality rates within 24 h. Fibrin(ogen)-mediated bacterial clearance was dependent on (pro)thrombin procoagulant function, supporting a suspected role for fibrin polymerization in this mechanism. Unexpectedly, the primary host initiator of coagulation, tissue factor, was found to be dispensable for this antimicrobial activity. Rather, the bacteria-derived prothrombin activator vWbp was identified as the source of the thrombin-generating potential underlying fibrin(ogen)-dependent bacterial clearance. Mice failed to eliminate S. aureus deficient in vWbp, but clearance of these same microbes in WT mice was restored if active thrombin was administered to the peritoneal cavity. These studies establish that the thrombin/fibrinogen axis is fundamental to host antimicrobial defense, offer a possible explanation for the clinical observation that coagulase-negative staphylococci are a highly prominent infectious agent in peritonitis, and suggest caution against anticoagulants in individuals susceptible to peritoneal infections.

Staphylococcus aureus binds to the N-terminal region of corneodesmosin to adhere to the stratum corneum in atopic dermatitis.

Staphylococcus aureus colonizes the skin of the majority of patients with atopic dermatitis (AD), and its presence increases disease severity. Adhesion of S. aureus to corneocytes in the stratum corneum is a key initial event in colonization, but the bacterial and host factors contributing to this process have not been defined. Here, we show that S. aureus interacts with the host protein corneodesmosin. Corneodesmosin is aberrantly displayed on the tips of villus-like projections that occur on the surface of AD corneocytes as a result of low levels of skin humectants known as natural moisturizing factor (NMF). An S. aureus mutant deficient in fibronectin binding protein B (FnBPB) and clumping factor B (ClfB) did not bind to corneodesmosin in vitro. Using surface plasmon resonance, we found that FnBPB and ClfB proteins bound with similar affinities. The S. aureus binding site was localized to the N-terminal glycine-serine-rich region of corneodesmosin. Atomic force microscopy showed that the N-terminal region was present on corneocytes containing low levels of NMF and that blocking it with an antibody inhibited binding of individual S. aureus cells to corneocytes. Finally, we found that S. aureus mutants deficient in FnBPB or ClfB have a reduced ability to adhere to low-NMF corneocytes from patients. In summary, we show that FnBPB and ClfB interact with the accessible N-terminal region of corneodesmosin on AD corneocytes, allowing S. aureus to take advantage of the aberrant display of corneodesmosin that accompanies low NMF in AD. This interaction facilitates the characteristic strong binding of S. aureus to AD corneocytes.

Toxigenic characterization, spoilage potential, and antimicrobial susceptibility of coagulase-positive Staphylococcus species isolated from Minas Frescal cheese.

This study aimed to identify coagulase-positive staphylococci (CPS) species from 21 samples of clandestine Minas Frescal cheese, investigate the potential for deterioration in psychrotrophic and mesophilic conditions, verify the toxigenic potential of Staphylococcus aureus, and determine the antimicrobial susceptibility profile of toxigenic S. aureus. Species determination was performed based on the detection of ß-hemolysis in 5% ovine blood agar; fermentation of mannitol, maltose, and trehalose sugars; and production of acetoin. After species determination, DNA extraction and analysis was performed for S. aureus colonies for genes encoding staphylococcal toxins (eta, etb, tst, sea, seb, sec, sed, and see) using 2 multiplex PCR assays. Isolates identified as toxigenic S. aureus were tested for antimicrobial susceptibility to tetracycline, erythromycin, clindamycin, gentamicin, ciprofloxacin, sulfazotrim, trimethoprim, streptomycin, cefoxitin, vancomycin and enrofloxacin. Elevated CPS counts were observed with an average of >6 log cfu/g. Of the 355 isolates, 177 (49.86%) were identified as S. aureus. Staphylococcus hyicus, Staphylococcus intermedius, Staphylococcus delphini, and Staphylococcus coagulans were identified in 3 (0.84%), 2 (0.56%), 2 (0.56%), and 1 (0.28%) isolates, respectively. Of the total number of S. aureus, 25 (52.08%) were positive for the gene that encodes for toxic shock toxin (TSST-1). Another 16 (33.33%) were positive for the sea gene, and 4 isolates (8.33%) were positive for see and one isolate each was positive for seb (2.08%), sec (2.08%), and etb (2.08%) genes. All isolates demonstrated lipolytic activity under mesophilic and psychrotrophic conditions. S. intermedius and S. hyicus had the most prominent proteolytic potential. Multidrug resistance was observed in most of the potentially toxigenic isolates, with clindamycin having the lowest efficiency (40%), whereas the aminoglycosides (gentamicin and streptomycin) had the highest effectiveness demonstrating inhibition in all evaluated isolates. Methicillin-resistant S. aureus (MRSA) was detected. Minas Frescal cheeses, marketed in the north of Tocantins in the Brazilian Amazon region, do not comply with legal quality standards and pose a public health risk due to the enterotoxigenic potential of multiresistant isolates, in addition to low shelf life of the samples given the high spoilage potential of this microbiota.

Methicillin-Resistant Staphylococcus aureus and Coagulase-Negative Staphylococcus from School Dining Rooms in Argentina.

Methicillin-resistant Staphylococcus aureus (MRSA) constitutes an important cause for concern in the field of public health, and the role of the food chain in the transmission of this pathogen and in antimicrobial resistance (AMR) has not yet been defined. The objectives of this work were to isolate and characterize coagulase-positive Staphylococcus (CoPS) and coagulase-negative Staphylococcus (CoNS), particularly S. aureus, from school dining rooms located in Argentina. From 95 samples that were obtained from handlers, inert surfaces, food, and air in 10 establishments, 30 Staphylococcus strains were isolated. Four isolates were S. aureus, and the remaining ones (N = 26) belonged to 11 coagulase-negative species (CoNS). The isolates were tested for susceptibility to nine antibiotics. The presence of genes encoding toxins (luk-PV, sea, seb, sec, sed, and see), adhesins (icaA, icaD), and genes that confer resistance to methicillin (mecA) and vancomycin (vanA) was investigated. The resistance rates measured for penicillin, cefoxitin, gentamicin, vancomycin, erythromycin, clindamycin, levofloxacin, trimethoprim-sulfamethoxazole, and tetracycline were 73%, 30%, 13%, 3%, 33%, 17%, 13%, 7%, and 7% of the isolates, respectively. Seventeen AMR profiles were detected, and 11 isolates were multidrug resistant (MDR). Seven methicillin-resistant Staphylococcus isolates were detected in the hands of handlers from four establishments, two of them were MRSA. Two S. aureus isolates presented icaA and icaD, another one, only icaD. The gene vanA was found in two isolates. In relation to S. aureus, resistance to vancomycin but not to gentamicin was detected. School feeding plays a key role in the nutrition of children, and the consumption of food contaminated with MRSA and vancomycin-resistant S. aureus (VRSA) can be a serious threat to health. In particular, it was detected that the handlers were the source of MRSA, VRSA, MR-CoNS (methicillin-resistant coagulase-negative Staphylococcus), and MDR isolates. The results obtained indicate that the vigilance of this pathogen in school dining rooms should be extreme.

Mapping of the fibrinogen-binding site on the staphylocoagulase C-terminal repeat region.

Fibrin (Fbn) deposits are a hallmark of staphylocoagulase (SC)-positive endocarditis. Binding of the N terminus of Staphylococcus aureus SC to host prothrombin triggers formation of an active SC·prothrombin∗ complex that cleaves host fibrinogen to Fbn. In addition, the C-terminal domain of the prototypical SC contains one pseudorepeat (PR) and seven repeats (R1 → R7) that bind fibrinogen/Fbn fragment D (frag D) by a mechanism that is unclear. Here, we define affinities and stoichiometries of frag D binding to C-terminal SC constructs, using fluorescence equilibrium binding, NMR titration, alanine scanning, and native PAGE. We found that constructs containing the PR and single repeats bound frag D with KD ∼50 to 130 nM and a 1:1 stoichiometry, indicating a conserved binding site bridging the PR and each repeat. NMR titration of PR-R7 with frag D revealed that residues 22 to 49, bridging PR and R7, constituted the minimal peptide (MP) for binding, corroborated by alanine scanning, and binding of labeled MP to frag D. MP alignment with the PR-R and inter-repeat junctions identified critical conserved residues. Full-length PR-(R1 → R7) bound frag D with KD ∼20 nM and a stoichiometry of 1:5, whereas constructs containing the PR and various three repeats competed with PR-(R1 → R7) for frag D binding, with a 1:3 stoichiometry. These findings are consistent with binding at PR-R and R-R junctions with modest inter-repeat sequence variability. CD of PR-R7 and PR-(R1 → R7) suggested a disordered flexible structure, allowing binding of multiple fibrin(ogen) molecules. Taken together, these results provide insights into pathogen localization on host fibrin networks.

In Vivo Effectiveness of Several Antimicrobial Locks To Eradicate Intravascular Catheter Coagulase-Negative Staphylococci Biofilms.

Tunneled central venous catheter (TCVC) related infection remains a challenge in the care of hemodialysis patients. We aimed to determine the best antimicrobial lock therapy (ALT) to eradicate coagulase-negative staphylococci (CoNS) biofilms. We studied the colonization status of the catheter every 30 days by quantitative blood cultures (QBC) drawn through all catheter lumens. Those patients with a significant culture (i.e.,100 to 1,000 CFU/mL) of a CoNS were classified as patients with a high risk of developing catheter-related bloodstream infections (CRBSI). They were assigned to receive daptomycin, vancomycin, teicoplanin lock solution, or the standard of care (SoC) (i.e., heparin lock). The primary endpoint was to compare eradication ability (i.e., negative QBC for 30 days after ending ALT) rates between different locks and the SoC. A second objective was to analyze the correlation between ALT exposure and isolation of CoNS with antimicrobial resistance. Daptomycin lock was associated with a significant higher eradication success than with the SoC: 85% versus 30% (relative risk [RR] = 14, 95% confidence interval [CI] = 2.4 - 82.7); followed by teicoplanin locks with a 83.3% success (RR = 11.7; 95% CI = 2 - 70.2). We observed CoNs isolates with a higher teicoplanin MIC in patients with repeated teicoplanin locks exposure (coefficient = 0.3; 95% CI = 0.11 - 0.47). However, teicoplanin MICs decreased in patients treated with vancomycin locks (coefficient = -0.56; 95% CI = -0.85 - -0.02). Methicillin-resistance decreased with accumulative ALT (RR = 0.82; 95% CI = 0.69 - 0.98). In this study, daptomycin locks achieve the highest eradication rate of CoNS from hemodialysis catheters in vivo.

Prevalence of multidrug-resistant coagulase-positive staphylococci in canine and feline dermatological patients over a 10-year period: a retrospective study.

Coagulase-positive staphylococci (CPS) are common cutaneous pathogens often requiring multiple courses of antibiotics, which may facilitate selection for methicillin-resistant (MR) and/or multidrug-resistant (MDR) strains. To determine the prevalence of canine and feline MR/MDR CPS associated with skin diseases, medical records were retrospectively searched from April 2010 to April 2020. Pets with at least one positive culture for CPS were selected. Age, sex, antimicrobial sensitivity, previous history of antimicrobial/immunomodulatory medications and methicillin resistance/multidrug resistance status were recorded. Staphylococcus pseudintermedius (SP) (575/748) and Staphylococcus schleiferi (SS) (159/748) in dogs, and Staphylococcus aureus (12/22) in cats, were the most common CPS isolated. Three hundred and twenty-three out of 575 isolates were MR-SP (56.2 %), 304/575 were MDR-SP (52.8 %), 100/159 were MR-SS (62.9 %) and 71/159 were MDR-SS (44.6 %). A trend analysis showed a significant increase of resistance to oxacillin and chloramphenicol for S. pseudintermedius (r=0.86, 0.8; P=0.0007, 0.0034, respectively). Major risk factors for MDR-SP included oxacillin resistance (OR: 3; 95 % CI: 1.4-6.5; P=0.0044), positivity for PBP2a (OR: 2.3; 95 % CI: 1-5; P=0.031) and use of antibiotics in the previous year (OR: 2.8; 95 % CI: 1.3-5.8; P=0.0071). Oxacillin resistance was identified as a major risk factor for MDR-SS (OR: 8.8; 95 % CI: 3.6-21.1; P<0.0001). These results confirmed the widespread presence of MR/MDR CPS in referred dermatological patients. Judicious antibiotic use, surveillance for MR/MDR infections and consideration of alternative therapies are crucial in mitigating the development of resistant strains.

Improved Genomic Prediction of Staphylococcus epidermidis Isolation Sources with a Novel Polygenic Score.

Staphylococcus epidermidis infections can be challenging to diagnose due to the species frequent contamination of clinical specimens and indolent course of infection. Nevertheless, S. epidermidis is the major cause of late-onset sepsis among premature infants and of intravascular infection in all age groups. Prior work has shown that bacterial virulence factors, antimicrobial resistances, and strains have up to 80% in-sample accuracy to distinguish hospital from community sources, but are unable to distinguish true bacteremia from blood culture contamination. Here, a phylogeny-informed genome-wide association study of 88 isolates was used to estimate effect sizes of particular genomic variants for isolation sources. A "polygenic score" was calculated for each isolate as the summed effect sizes of its repertoire of genomic variants. Predictive models of isolation sources based on polygenic scores were tested with in-samples and out-samples from prior studies of different patient populations. Polygenic scores from accessory genes (AGs) distinguished hospital from community sources with the highest accuracy to date, up to 98% for in-samples and 65% to 91% for various out-samples, whereas scores from single nucleotide polymorphisms (SNPs) had lower accuracy. Scores from AGs and SNPs achieved the highest in-sample accuracy to date, up to 76%, in distinguishing infection from contaminant sources within a hospital. Model training and testing data sets with more similar population structures resulted in more accurate predictions. This study reports the first use of a polygenic score for predicting a complex bacterial phenotype and shows the potential of this approach for enhancing S. epidermidis diagnosis.

Efficacy of vancomycin lock therapy for totally implantable venous access port-related infection due to coagulase-negative staphylococci in 100 patients with cancer.

OBJECTIVES: Data on the efficacy of vancomycin catheter lock therapy (VLT) for conservative treatment of totally implantable venous access port-related infections (TIVAP-RI) due to CoNS are scarce. The aim of this study was to evaluate the effectiveness of VLT in the treatment of TIVAP-RI due to CoNS in cancer patients. METHODS: This prospective, observational, multicentre study included adults with cancer treated with VLT for a TIVAP-RI due to CoNS. The primary endpoint was the success of VLT, defined as no TIVAP removal nor TIVAP-RI recurrence within 3 months after initiation of VLT. The secondary endpoint was 3 month mortality. Risk factors for VLT failure were also analysed. RESULTS: One hundred patients were included [men 53%, median age 63 years (IQR 53-72)]. Median duration of VLT was 12 days (IQR 9-14). Systemic antibiotic therapy was administered in 87 patients. VLT was successful in 44 patients. TIVAP could be reused after VLT in 51 patients. Recurrence of infection after completion of VLT occurred in 33 patients, among which TIVAP was removed in 27. Intermittent VLT (antibiotic solution left in place in the TIVAP lumen part of the time) was identified as a risk factor for TIVAP-RI recurrence. At 3 months, 26 deaths were reported; 1 (4%) was related to TIVAP-RI. CONCLUSIONS: At 3 months, success of VLT for TIVAP-RI due to CoNS was low. However, removing TIVAP was avoided in nearly half the patients. Continuous locks should be preferred to intermittent locks. Identifying factors of success is essential to select patients who may benefit from VLT.

The frequency of adherence, biofilm-associated, Arginine Catabolic Mobile element genes, and biofilm formation in clinical and healthcare worker coagulase-negative staphylococci isolates.

BACKGROUND: Healthcare workers may pave the way for increased infections in hospitalized patients by coagulase-negative staphylococci (CoNS). Biofilm formation and antibiotic resistance are the major problems posed by CoNS in nosocomial infections. In this study, we determined biofilm production level and the distribution of biofilm-associated and virulence genes, including icaADBC, aap, bhp, atlE, embp, and fbe, as well as IS256, IS257, mecA, and ACME clusters (arc-A, opp-3AB) among 114 clinical (n = 57) and healthcare workers (n = 57) CoNS isolates in Kerman, Iran. RESULTS: In this study, more than 80% (n = 96) of isolates were methicillin-resistant CoNS (MR-CoNS). Out of 114 isolates, 33% (n = 38) were strong biofilm producers. Strong biofilm formation was found to be significantly different between clinical and healthcare workers' isolates (P < 0.050). In addition, 28% (n = 32) of isolates were positive for icaADBC simultaneously, and all were strong biofilm producers. The prevalence of icaADBC, mecA, bhp, fbe, and IS256 in clinical isolates was higher than that in healthcare workers' isolates (P < 0.050). A significant relationship was observed between clinical isolates and the presence of icaADBC, mecA, bhp, and IS256. Although these elements were detected in healthcare workers' isolates, they were more frequent in clinical isolates compared to those of healthcare workers. CONCLUSIONS: The high prevalence of ACME clusters in healthcare workers' isolates and biofilm formation of these isolates partially confirms the bacterial colonization in the skin of healthcare workers. Isolating MR-CoNS from healthcare workers' skin through similar genetic elements to clinical isolates, such as icaADBC, mecA, and IS256, calls for appropriate strategies to control and prevent hospital infections.

Identification and characterization of SCCmec typing with psm-mec positivity in staphylococci from patients with coagulase-negative staphylococci peritoneal dialysis-related peritonitis.

BACKGROUND: Peritonitis is the most important complication of peritoneal dialysis (PD) and coagulase-negative staphylococci (CNS) are a frequent cause of dialysis-related infections. The association between SCCmec typing with psm-mec positivity in staphylococci and PD-related infections has not been identified. We aim to investigate the molecular epidemiology of CNS isolated from PD-peritonitis in a single Chinese center, focusing on the genetic determinants conferring methicillin resistance. METHODS: We collected 10 genetically unrelated CNS isolates from 10 patients with CNS PD-related peritonitis. The patients were divided into two groups based on the results of MIC to oxacillin: the methicillin-resistant CNS (MRCNS) and methicillin-sensitive CNS (MSCNS) groups. The biofilm formation group (BFG) and the non-biofilm formation group (NBFG) were used as the control groups. Phenotypic and molecular methods were used to analyze SCCmec types I, II and III, associated genes and biofilm formation and the existence of psm-mec. The demographic data and clinical indicators were collected. RESULTS: Ten CNS PD-related peritonitis patients were enrolled for this study. There were 6 MRCNS and 4 MRCNS isolates. SCCmec types were fully determined in 10 isolates. Seven staphylococci (70%) carried SCCmec, of which 4 isolates carried single SCCmec type I (40%) and 3 isolates had multiple SCCmec elements (I + III). Of the 6 MRCNS isolates, 3 carried SCCmec type I (50%) and 2 isolates carried SCCmec type I + III (33.3%). A high diversity of ccr types, mec complexes and ccr-mec complex combinations was identified among the 10 CNS isolates. The psm-mec gene was detected in 2/10 (20%) CNS isolates. There was no mutation in the psm-mec gene. CONCLUSIONS: The majority of isolates were hospital-associated isolates. Furthermore, 2 psm-mec positive isolates were MRCNS in the NBFG. The PD patients frequent exposure to hospital would be the main risk factor. The presence of the psm-mec signal in the spectra of the MRCNS tested here demonstrates the presence of certain SCCmec cassettes that convey methicillin resistance.

Cheilitis in an atopic dermatitis patient associated with co-infection of Staphylococcus pseudintermedius and Staphylococcus aureus.

BACKGROUND: Atopic dermatitis (AD) is an inflammatory skin condition distinguished by an activated Th2 immune response. The local skin microbial dysbiosis is a contributing factor to the development of AD. The pathogenic coagulase-positive Staphylococcus aureus is the primary species responsible for the progression of AD. Even though Staphylococcus pseudintermedius is an animal-origin pathogen, it is increasingly becoming a source of concern in human diseases. As another coagulase-positive Staphylococci, it is crucial to pay more attention to S. pseudintermedius isolated from the lesion site. RESULTS: In our investigation, we presented a case of cheilitis in a patient with atopic dermatitis (AD). We utilized culture and next-generation genomic sequencing (NGS) to identify the bacteria present on the skin swabs taken from the lip sites both prior to and following treatment. Our findings indicated that the predominant bacteria colonizing the lesion site of AD were S. pseudintermedius and S. aureus, both of which were eradicated after treatment. The Multi-locus sequence typing (MLST) of S. pseudintermedius and S. aureus demonstrated coordinated antibiotic susceptibility, with ST2384 and ST22 being the respective types. Although the skin abscess area resulting from S. pseudintermedius infection was significantly smaller than that caused by S. aureus in mice, the expression of cytokines interleukin-4 (IL-4) and interleukin-5 (IL-5) were significantly higher in the S. pseudintermedius-infected mice. CONCLUSIONS: The S. pseudintermedius strain isolated from the lesion site of the AD patient exhibited a higher expression of IL-4 and IL-5 when colonized on mouse skin, as compared to S. aureus. This observation confirms that S. pseudintermedius can effectively induce the Th2 response in vivo. Our findings suggest that animal-origin S. pseudintermedius may play a role in the development of AD when colonized on the skin, emphasizing the importance of taking preventive measures when in contact with animals.