Staphylococcus aureus AbcA transporter enhances persister formation under ß-lactam exposure.

We evaluated the role of Staphylococcus aureus AbcA transporter in bacterial persistence and survival following exposure to the bactericidal agents nafcillin and oxacillin at both the population and single-cell levels. We show that AbcA overexpression resulted in resistance to nafcillin but not oxacillin. Using distinct fluorescent reporters of cell viability and AbcA expression, we found that over 6-14 hours of persistence formation, the proportion of AbcA reporter-expressing cells assessed by confocal microscopy increased sixfold as cell viability reporters decreased. Similarly, single-cell analysis in a high-throughput microfluidic system found a strong correspondence between antibiotic exposure and AbcA reporter expression. Persister cells grown in the absence of antibiotics showed neither an increase in nafcillin MIC nor in abcA transcript levels, indicating that survival was not associated with stable mutational resistance or abcA overexpression. Furthermore, persister cell levels on exposure to 1×MIC and 25×MIC of nafcillin decreased in an abcA knockout mutant. Survivors of nafcillin and oxacillin treatment overexpressed transporter AbcA, contributing to an enrichment of the number of persisters during treatment with pump-substrate nafcillin but not with pump-non-substrate oxacillin, indicating that efflux pump expression can contribute selectively to the survival of a persister population.

Potential antivirulence and antibiofilm activities of sub-MIC of oxacillin against MDR S. aureus isolates: an in-vitro and in-vivo study.

BACKGROUND: Multi-drug resistant Staphylococcus aureus is one of the most common causes of nosocomial and community-acquired infections, with high morbidity and mortality. Treatment of such infections is particularly problematic; hence, it is complicated by antibiotic resistance, and there is currently no reliable vaccine. Furthermore, it is well known that S. aureus produces an exceptionally large number of virulence factors that worsen infection. Consequently, the urgent need for anti-virulent agents that inhibit biofilm formation and virulence factors has gained momentum. Therefore, we focused our attention on an already-approved antibiotic and explored whether changing the dosage would still result in the intended anti-virulence effect. METHODS: In the present study, we determined the antibiotic resistance patterns and the MICs of oxacillin against 70 MDR S. aureus isolates. We also investigated the effect of sub-MICs of oxacillin (at 1/4 and 1/8 MICs) on biofilm formation using the crystal violet assay, the phenol-sulphuric acid method, and confocal laser scanning microscopy (CLSM). We examined the effect of sub-MICs on virulence factors and bacterial morphology using quantitative reverse transcription polymerase chain reaction (qRT-PCR) and electron microscopy, respectively. Moreover, we studied the effect of sub-MICs of oxacillin (OX) in-vivo using a wound infection model. RESULTS: Oxacillin at 1/2 MIC showed a significant decrease in bacterial viability, while 1/4 and 1/8 MICs had negligible effects on treated bacterial isolates. Treatment of MDR isolates with 1/4 or 1/8 MICs of oxacillin significantly reduced biofilm formation (64% and 40%, respectively). The treated MDR S. aureus with sub-MICs of OX exhibited a dramatic reduction in several virulence factors, including protease, hemolysin, coagulase, and toxic shock syndrome toxin-1 (TSST-1) production. The sub-MICs of OX significantly decreased (P < 0.05) the gene expression of biofilm and virulence-associated genes such as agrA, icaA, coa, and tst. Furthermore, oxacillin at sub-MICs dramatically accelerated wound healing, according to the recorded scoring of histological parameters. CONCLUSION: The treatment of MDR S. aureus with sub-MICs of oxacillin can help in combating the bacterial resistance and may be considered a promising approach to attenuating the severity of S. aureus infections due to the unique anti-biofilm and anti-virulence activities.

A rare biofilm dispersion strategy demonstrated by Staphylococcus aureus under oxacillin stress.

Staphylococcus aureus (S. aureus), a versatile Gram-positive bacterium, is implicated in a spectrum of infections, and its resilience is often attributed to biofilm formation. This study investigates the effect of sub-inhibitory doses of oxacillin on biofilm formation by methicillin-resistant S. aureus (MRSA). Specifically, it examines how these doses influence biofilms' development, maturation, and dispersal. The biofilm's zenith reached 48 h of incubation, followed by a noteworthy decline at 96 h and a distinctive clearance zone around biofilm-positive cells exposed to oxacillin. Scanning electron micrographs unveiled an intriguing active biofilm dispersal mechanism, a rarity in this species. Among 180 isolates, only three carrying the elusive icaD gene exhibited this phenomenon. icaD gene was absent in their counterparts. Notably, the icaD gene emerges as a distinctive marker, crucial in regulating biofilm dispersion and setting these isolates apart. The captivating interplay of oxacillin, biofilm dynamics, and genetic signatures disintegrate novel dimensions in understanding MRSA's adaptive strategies and underscores the importance of the icaD gene in engineering biofilm resilience.

Daptomycin Plus Oxacillin for Persistent Methicillin-Susceptible Staphylococcus aureus Bacteremia.

BACKGROUND: The preferred antibiotic salvage regimen for persistent methicillin-susceptible Staphylococcus aureus bacteremia (MSSAB) is unclear. Ertapenem with cefazolin or an antistaphylococcal penicillin has been primarily described, but identifying alternative carbapenem-sparing options may support antibiotic stewardship efforts and decrease the risk of antibiotic-associated Clostridioides difficile infection. OBJECTIVE: We sought to evaluate the effectiveness and safety of daptomycin plus oxacillin (D/O) for persistent MSSAB. METHODS: This was a single-center, retrospective cohort of patients with persistent MSSAB who received D/O between January 1, 2014, and January 1, 2023. Adult patients were included if they had blood cultures positive for MSSA ≥72 hours and received D/O combination for ≥48 hours. Patients were excluded if they were pregnant, incarcerated, or received another antibiotic considered to have excellent activity against MSSA. The primary outcome was time to MSSA bacteremia clearance post-daptomycin initiation. Secondary outcomes included microbiological cure, hospital length of stay, 90-day all-cause mortality, MSSA bacteremia-related mortality, 90-day readmission for MSSAB, and incidence of antibiotic-associated adverse effects. Time to MSSAB clearance post-D/O initiation was plotted using Kaplan-Meier estimation. RESULTS: Seven unique patient encounters were identified including 4 with endocarditis. Despite a median MSSA bacteremia duration of 7.8 days, median clearance was 2 days post-daptomycin initiation. All achieved microbiological cure, and no adverse effects were reported. Ninety-day all-cause mortality, MSSAB-related mortality, and 90-day readmission for MSSAB occurred in 28.6%, 14.3%, and 14.3% of patients, respectively. CONCLUSIONS AND RELEVANCE: D/O was an effective, well-tolerated salvage regimen in this cohort and may represent a carbapenem-sparing option for persistent MSSAB.

Retrospective Evaluation of the Association of Oxacillin MIC on Acute Treatment Outcomes with Cefazolin and Antistaphylococcal Penicillins in Methicillin-Susceptible Staphylococcus aureus Bacteremia.

Antistaphylococcal penicillins (ASP) and cefazolin are first-line treatment of methicillin-susceptible Staphylococcus aureus (MSSA) bacteremia. Borderline oxacillin resistance (i.e., oxacillin MICs 1-8 µg/mL) is observed in strains hyperproducing beta-lactamases. This mechanism is also behind the proposed inoculum effect. Minimal data exists on the comparative efficacy of cefazolin or ASP in qualitatively susceptible strains that demonstrate MICs of oxacillin of 1 to 2 µg/mL compared to strains with MIC of oxacillin < 1 µg/mL. We performed a retrospective cohort study of acute treatment outcomes in adult patients with community-acquired MSSA bacteremia treated with cefazolin or ASP, stratified by oxacillin MIC. The primary outcome was a composite of all-cause mortality during the index inpatient admission, failure to clear blood cultures within 72 h after initiating definitive therapy, and change in therapy due to perceived lack of efficacy. A total of 402 patients were included in this study, including 226 isolates with an oxacillin MIC ≥ 1 µg/mL and 176 isolates with an MIC < 1 µg/mL. There were no differences in the rate of the primary outcome occurrence between patients with an oxacillin MIC ≥ 1 µg/mL and an MIC < 1 µg/mL (16.4% versus 15.9%, P = 0.90). There was no difference in the primary outcome between high versus low oxacillin MIC groups among those who received ASP (22.9% versus 24.1%, P = 0.86) or cefazolin (10.3% versus 11.9%, P = 0.86). In our cohort of patients with MSSA bacteremia, oxacillin MIC (i.e., ≥ 1 versus < 1 µg/mL) was not associated with acute treatment outcomes, regardless of the beta-lactam selected as definitive therapy.

Post-treatment outcomes of ceftriaxone versus antistaphylococcal penicillins or cefazolin for definitive therapy of methicillin-susceptible Staphylococcus aureus bacteremia.

Methicillin-susceptible Staphylococcus aureus (MSSA) bacteremia is associated with poor outcomes. Ceftriaxone offers logistical advantages over other standard therapies, though in vitro studies have questioned its efficacy and clinical studies of ceftriaxone in MSSA bacteremia are conflicting.We performed a multicenter, retrospective cohort study of adult patients who received ceftriaxone, cefazolin, or antistaphylococcal penicillins as definitive therapy for MSSA bacteremia from 2018 to 2019. Definitive therapy was defined as the antibiotic used in the outpatient setting. Patients were excluded if they received less than 7 days of outpatient therapy. Follow-up started on the date of definitive therapy completion. The primary outcome was 90-day treatment failure, defined as a composite of mortality and microbiologic recurrence. This was analyzed with multivariable Cox regression. A total of 223 patients were included, 37 (16.6%) of whom received ceftriaxone. The most common ceftriaxone dose was 2 g daily (83.8%). The most common primary site of infection was skin/soft tissue (37.2%), unknown (21.1%), and catheter-related (15.2%). Twenty-six (11.7%) developed infective endocarditis. Median total duration of treatment was 31.0 days, and median outpatient duration was 24.0 days. Twenty-six (11.7%) developed 90-day treatment failure. After adjusting for Charlson comorbidity index, duration of therapy, and use of transesophageal echocardiography, definitive treatment with ceftriaxone was associated with treatment failure (hazard ratio 2.66, 95% confidence interval 1.15-6.12; p=0.022). Among patients with MSSA bacteremia, definitive treatment with ceftriaxone was associated with a higher risk of treatment failure within 90 days as compared to cefazolin or antistaphylococcal penicillins.

Phenotypic and genomic characteristics of oxacillin-susceptible mecA-positive Staphylococcus aureus, rapid selection of high-level resistance to beta-lactams.

The aim of this study is to describe the phenotypic and genetic properties of oxacillin-susceptible methicillin-resistant Staphylococcus aureus (OS-MRSA) isolates and their beta-lactam resistant derivatives obtained after selection with oxacillin. A collection of hospital- (HA-) and community-acquired (CA-) MRSA was screened for oxacillin susceptibility. Antibiotic susceptibility testing, population analysis profile (PAP), mecA expression analysis, and whole genome sequencing (WGS) were performed for 60 mecA-positive OS-MRSA isolates. Twelve high-level beta-lactam resistant derivatives selected during PAP were also subjected to WGS. OS-MRSA were more prevalent among CA-MRSA (49/205, 24%) than among HA-MRSA (11/575, 2%). OS-MRSA isolates belonged to twelve sequence types (ST), with a predominance of ST22-t223-SCCmec IVc and ST59-t1950-SCCmec V lineages. OS-MRSA were characterized by mecA promoter mutations at - 33 (C→T) or - 7 (G→T/A) along with PBP2a substitutions (S225R or E246G). The basal and oxacillin-induced levels of mecA expression in OS-MRSA isolates were significantly lower than those in control ST8-HA-MRSA isolates. Most of the OS-MRSA isolates were heteroresistant to oxacillin. High-level beta-lactam resistant OS-MRSA derivatives selected with oxacillin carried mutations in mecA auxiliary factors: relA (metabolism of purines), tyrS, cysS (metabolism of tRNAs), aroK, cysE (metabolism of amino acids and glycolysis). Cefoxitin-based tests demonstrated high specificity for OS-MRSA detection. The highest positive predictive values (PPV > 0.95) were observed for broth microdilution, the VITEK® 2 automatic system, and chromogenic media. Susceptibility testing of CA-MRSA requires special attention due to the high prevalence of difficult-to-detect OS-MRSA among them. Mis-prescription of beta-lactams for the treatment of OS-MRSA may lead to selection of high-level resistance and treatment failures.

Epidemiology of clinically isolated methicillin-resistant Staphylococcus aureus (MRSA) and its susceptibility to linezolid and vancomycin in Egypt: a systematic review with meta-analysis.

BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA) is a major nosocomial pathogen that causes severe morbidity and mortality worldwide. For the establishment of national strategies to combat MRSA infection in each country, accurate and current statistics characterizing the epidemiology of MRSA are essential. The purpose of this study was to determine the prevalence of MRSA among Staphylococcus aureus clinical isolates in Egypt. In addition, we aimed to compare different diagnostic methods for MRSA and determine the pooled resistance rate of linezolid and vancomycin to MRSA. To address this knowledge gap, we conducted a systematic review with meta-analysis. METHODS: A comprehensive literature search from inception to October 2022 of the following databases was performed: MEDLINE [PubMed], Scopus, Google Scholar, and Web of Science. The review was conducted following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) Statement. Based on the random effects model, results were reported as proportions with a 95% confidence interval (CI). Analyses of the subgroups were conducted. A sensitivity analysis was conducted to test the robustness of the results. RESULTS: A total of sixty-four (64) studies were included in the present meta-analysis, with a total sample size of 7171 subjects. The overall prevalence of MRSA was 63% [95% CI: 55-70]. Fifteen (15) studies used both PCR and cefoxitin disc diffusion for MRSA detection, with a pooled prevalence rate of 67% [95% CI: 54-79] and 67% [95% CI: 55-80], respectively. While nine (9) studies used both PCR and Oxacillin disc diffusion for MRSA detection, the pooled prevalences were 60% [95% CI: 45-75] and 64% [95% CI: 43-84], respectively. Furthermore, MRSA appeared to be less resistant to linezolid than vancomycin, with a pooled resistance rate of 5% [95% CI: 2-8] to linezolid and 9% [95% CI: 6-12] to vancomycin, respectively. CONCLUSION: Our review highlights Egypt's high MRSA prevalence. The cefoxitin disc diffusion test results were found to be consistent with PCR identification of the mecA gene. A prohibition on antibiotic self-medication and efforts to educate healthcare workers and patients about the proper use of antimicrobials may be required to prevent further increases.

The Synergistic Antimicrobial Effect and Mechanism of Nisin and Oxacillin against Methicillin-Resistant Staphylococcus aureus.

Methicillin-resistant Staphylococcus aureus (MRSA) is responsible for skin and soft tissue infections with multi-resistance to many antibiotics. It is thus imperative to explore alternative antimicrobial treatments to ensure future treatment options. Nisin (NIS), an antibacterial peptide produced by Lactococcus lactis, was selected to combine with Oxacillin (OX), to evaluate the antimicrobial effect and potential mechanism against MRSA. The synergistic antimicrobial effect of OX and NIS was verified by Minimal Inhibitory Concentration (MIC) assays, checkerboard analysis, time-kill curve, biofilm producing ability, and mice skin infection model in vivo. For the potential synergistic antimicrobial mechanism, the microstructure and integrity change of MRSA cells were determined by Scanning and Transmission Electron Microscope (SEM and TEM), intracellular alkaline phosphatase activity and propidium iodide staining were assayed; And transcription of mecA, main gene of MRSA resistant to OX, were detected by qRT-PCR. The results showed NIS could restore the sensitivity of MRSA to OX and inhibit biofilm production; OX + NIS can make MRSA cell deform; NIS may recover OX sensitivity by inhibiting the transcription of mecA. In vivo, mice skin infection models indicate that OX + NIS can substantially alleviate MRSA infections. As a safe commercially available biological compound, NIS and the combination of antibiotics are worth developing as new anti-MRSA biomaterials.

Polyclonal Dissemination of OXA-232 Carbapenemase-Producing Klebsiella pneumoniae, France, 2013-2021.

During 2013-2021, increased prevalence of oxacillinase 232-producing Enterobacterales was observed in France, mostly driven by its emergence in Klebsiella pneumoniae. Whole-genome sequencing identified that oxacillinase 232-producing K. pneumoniae belonged to 14 sequence types (STs), among which 2 polyclonal high-risk clones, ST-231 and ST-2096, were overrepresented.

Oxacillin plus ertapenem rapidly clears persistent left ventricular assist device-related methicillin-susceptible Staphylococcus aureus bacteremia.

There is an increasing use of left ventricular assist devices (LVADs) as bridge to transplantation or permanent destination therapy in the heart failure patient population. Infection remains a common complication in LVADs, with Gram-positive skin flora as predominant pathogens implicated, including Staphylococcus aureus. While there is emerging evidence for synergistic antibiotic combinations with methicillin resistant S. aureus, there remains a significant gap in the literature for persistent methicillin susceptible S. aureus bacteremia. In this article, we describe the first successful treatment of persistent LVAD-related bacteremia with salvage oxacillin plus ertapenem. The salvage therapy described here must be balanced by the risks for toxicity, impact on resistance, microbiota disruption, drug shortages, and patient costs. This combination warrants further evaluation in the clinical setting to better establish its role in our expanding patient population.

Role of RNAIII in Resistance to Antibiotics and Antimicrobial Agents in Staphylococcus epidermidis Biofilms.

Staphylococcus epidermidis is a known opportunistic pathogen and is one of the leading causes of chronic biofilm-associated infections. Biofilm formation is considered as a main strategy to resist antibiotic treatment and help bacteria escape from the human immune system. Understanding the complex mechanisms in biofilm formation can help find new ways to treat resistant strains and lower the prevalence of nosocomial infections. In order to examine the role of RNAIII regulated by the agr quorum sensing system and to what extent it influences biofilm resistance to antimicrobial agents, deletion mutant S. epidermidis RP62a-ΔRNAIII deficient in repressor domains with a re-maining functional hld gene was created. A deletion strain was used to examine the influence of oxacillin in combination with vanillin on biofilm resistance and cell survival was determined. Utilizing real-time qPCR, confocal laser scanning microscopy (CLSM), and crystal violet staining analyses, we found that the RNAIII-independent controlled phenol soluble modulins (PSMs) and RNAIII effector molecule have a significant role in biofilm resistance to antibiotics and phenolic compounds, and it protects the integrity of biofilms. Moreover, a combination of antibiotic and antimicrobial agents can induce methicillin-resistant S. epidermidis biofilm formation and can lead to exceedingly difficult medical treatment.

Cheminformatics Study on Structural and Bactericidal Activity of Latest Generation ß-Lactams on Widespread Pathogens.

Raman spectra of oxacillin (OXN), carbenicillin (CBC), and azlocillin (AZL) are reported for the first time together with their full assignment of the normal modes, as calculated using Density Functional Theory (DFT) methods with the B3LYP exchange-correlation functional coupled to the 6-31G(d) and 6-311+G(2d,p) basis sets. Molecular docking studies were performed on five penicillins, including OXN, CBC, and AZL. Subsequently, their chemical reactivity and correlated efficiency towards specific pathogenic strains were revealed by combining frontier molecular orbital (FMO) data with molecular electrostatic potential (MEP) surfaces. Their bactericidal activity was tested and confirmed on a couple of species, both Gram-positive and Gram-negative, by using the disk diffusion method. Additionally, a surface-enhanced Raman spectroscopy (SERS)-principal component analysis (PCA)-based resistogram of A. hydrophila is proposed as a clinically relevant insight resulting from the synergistic cheminformatics and vibrational study on CBC and AZL.

Phenotypic and genotypic characterization of oxacillin-susceptible and mecA positive Staphylococcus aureus strains isolated in Uruguay.

The aim of this study was to characterize phenotypically and genotypically 27 mecA positive Staphylococcus aureus strains with oxacillin MICs of ≤2µg/ml by Vitek 2, isolated in different regions of Uruguay. Susceptibility to oxacillin and cefoxitin was studied by gradient diffusion, disk diffusion to cefoxitin, and Phoenix and MicroScan systems. PBP2a was determined. SCCmec typing was performed and the isolates were compared by PFGE. Twenty-six isolates were susceptible to oxacillin; one strain was susceptible to cefoxitin by disk diffusion and 3 strains by gradient diffusion. Phoenix and MicroScan panels detected methicillin resistance in 25 and 27 strains, respectively. Twenty-six strains tested positive for PBP2a. Twenty-six strains carried SCCmec V and 24 belonged to pulsotype A. One strain carried SCCmec IV and did not belong to pulsotype A. Cefoxitin disk diffusion test and PBP2a detection correctly identified 26 of these 27 strains as MRSA. PFGE results suggest the dissemination of a cluster of MRSA carrying SCCmec V.

Impact of FtsZ Inhibition on the Localization of the Penicillin Binding Proteins in Methicillin-Resistant Staphylococcus aureus.

Methicillin-resistant Staphylococcus aureus (MRSA) is a multidrug-resistant pathogen of acute clinical importance. Combination treatment with an FtsZ inhibitor potentiates the activity of penicillin binding protein (PBP)-targeting ß-lactam antibiotics against MRSA. To explore the mechanism underlying this synergistic behavior, we examined the impact of treatment with the FtsZ inhibitor TXA707 on the spatial localization of the five PBP proteins expressed in MRSA. In the absence of drug treatment, PBP1, PBP2, PBP3, and PBP4 colocalize with FtsZ at the septum, contributing to new cell wall formation. In contrast, PBP2a localizes to distinct foci along the cell periphery. Upon treatment with TXA707, septum formation becomes disrupted, and FtsZ relocalizes away from midcell. PBP1 and PBP3 remain significantly colocalized with FtsZ, while PBP2, PBP4, and PBP2a localize away from FtsZ to specific sites along the periphery of the enlarged cells. We also examined the impact on PBP2a and PBP2 localization of treatment with ß-lactam antibiotic oxacillin alone and in synergistic combination with TXA707. Significantly, PBP2a localizes to the septum in approximately 15% of the oxacillin-treated cells, a behavior that likely contributes to the ß-lactam resistance of MRSA. Combination treatment with TXA707 causes both PBP2a and PBP2 to localize in malformed septum-like structures. Our collective results suggest that PBP2, PBP4, and PBP2a may function collaboratively in peripheral cell wall repair and maintenance in response to FtsZ inhibition by TXA707. Cotreatment with oxacillin appears to reduce the availability of PBP2a to assist in this repair, thereby rendering the MRSA cells more susceptible to the ß-lactam. IMPORTANCE MRSA is a multidrug-resistant bacterial pathogen of acute clinical importance, infecting many thousands of individuals globally each year. The essential cell division protein FtsZ has been identified as an appealing target for the development of new drugs to combat MRSA infections. Through synergistic actions, FtsZ-targeting agents can sensitize MRSA to antibiotics like the ß-lactams that would otherwise be ineffective. This study provides key insights into the mechanism underlying this synergistic behavior as well as MRSA resistance to ß-lactam drugs. The results of this work will help guide the identification and optimization of combination drug regimens that can effectively treat MRSA infections and reduce the potential for future resistance.

Molecular epidemiology of methicillin resistant Staphylococcus species in healthcare workers of a blood bank in the Brazilian Amazon.

BACKGROUND: Healthcare workers are susceptible to colonization by multiresistant bacteria, which can increase the risk of outbreaks. METHODS: Samples were collected from the nasopharynx, hands, and lab coats of healthcare workers. The phenotypic identification was carried out using a VITEK®2 rapid test system. PCR tests for the mecA gene and the sequencing of the amplicons were performed. Staphylococcus epidermidis and Staphylococcus aureus phylogenies were reconstructed using the Bayesian inference. RESULTS: A total of 225 healthcare workers participated in this study. Of these, 21.3% were male and 78.7% female. S. epidermidis and S.aureus showed high levels of resistance to penicillin, ampicillin, erythromycin, tetracycline and cefoxitin. The prevalence of methicillin resistant S. aureus was 3.16% and methicillin resistant S. epidermidis was 100%. Multilocus sequence typing identified 23 new S. epidermidis sequence types, and one new allele and sequence type for S. aureus. The frequency of methicillin-resistant S. epidermidis in nursing and hemotherapy technicians as a percentage of the total number of healthcare workers was 5.8-3.1%, while the frequency of methicillin resistant S. aureus in hemotherapy technicians and biomedics, as a percentage of the total number of healthcare workers was 4.2-8.9%%. CONCLUSIONS: The healthcare workers at the city's blood bank, even when taking the necessary care with their hands, body and clothes, harbour methicillin-resistant S. aureus and S. epidermidis sequence types, which, as a potential source of multidrug resistant bacteria, can contribute to nosocomial infections among hematological patients.

Antistaphylococcal penicillins vs. cefazolin in the treatment of methicillin-susceptible Staphylococcus aureus infective endocarditis: a quasi-experimental monocentre study.

Whether cefazolin is as effective and safer than antistaphylococcal penicillins (ASPs) for the treatment of methicillin-susceptible Staphylococcus aureus (MSSA) infective endocarditis (IE) is still debated in the absence of a randomized controlled trial. In this quasi-experimental study, we aimed to assess the effectiveness and safety of these two treatments in MSSA-IE, using the ASPs nationwide shortage in April 2016 as a unique opportunity to overcome the indication bias associated with observational studies. In this single-centre study, we compared patients with Duke-Li definite MSSA-IE treated with ASPs from January 2015 to March 2016 versus those treated with cefazolin from April 2016 to December 2018, when ASPs were not available. Effectiveness outcome was 90-day all-cause mortality. Safety outcomes included significant decrease in GFR and significant increase in serum liver enzymes. Logrank test was used to compare survival rates. Of 73 patients with MSSA-IE, 35 and 38 were treated with ASPs and cefazolin, respectively. Baseline patients' characteristics (demography, native or prosthetic valve IE, clinical characteristics, cardiac and septic complications) were similar between groups. Ninety-day all-cause mortality was 28.6% and 21.1%, in patients treated with ASPs and cefazolin, respectively (logrank p = 0.5727). There was no difference between groups for incident renal or liver toxicity events: acute kidney injury 45.7% vs. 44.7% (p = 0.933), increased ALT 5.7% vs. 13.2% (p = 0.432), bilirubin increase 5.7% vs. 10.5% (p = 0.676), in ASPs vs. cefazolin groups, respectively. In this quasi-experimental, effectiveness and safety did not statistically differ between ASPs and cefazolin for MSSA-IE treatment.

Disproportionality Analysis of Safety with Nafcillin and Oxacillin with the FDA Adverse Event Reporting System (FAERS).

Antistaphylococcal penicillins such as nafcillin and oxacillin are among the first choices of treatment for severe invasive methicillin-susceptible Staphylococcus aureus (MSSA) infections, although there has been limited safety evaluations between individual agents. Using the FDA Adverse Event Reports System (FAERS), oxacillin was observed to have a lower proportion of reports of acute renal failure (reporting odds ratio [ROR], 5.3 [95% confidence interval {CI}, 3.1 to 9.3] versus 21.3 [95% CI, 15.8 to 28.6], respectively) and hypokalemia (ROR, 0.7 [95% CI, 0.1 to 4.8] versus 11.4 [95% CI, 7.1 to 18.3], respectively) than nafcillin.

The antivirulence compound myricetin possesses remarkable synergistic effect with antibacterials upon multidrug resistant Staphylococcus aureus.

Staphylococcus aureus is an opportunistic pathogen involved in several human diseases and presents ability to produce many virulence factors and resistance to antibacterial agents. One of the current strategies to combat such multidrug resistant bacteria is the antibacterial combination therapy. Myricetin is a flavonoid capable of inhibiting several S. aureus virulence factors without influencing on bacterial growth. Therefore, the combination of antibacterials with the antivirulence compound myricetin may provide a positive interaction to control multidrug resistant-bacteria. This work aims to evaluate the effect of the combination of myricetin with oxacillin and vancomycin against methicillin resistant S. aureus (MRSA) and vancomycin intermediate resistant S. aureus (VISA) strains. Concentrations used in combination assays were determined according to the minimum inhibitory concentration (MIC) for antibacterials and to the biofilm minimum inhibitory concentration (BMIC) for myricetin. Checkerboard evaluations showed reduction in MIC for antibacterials in presence of myricetin and time-kill assays confirmed the synergism for these combinations, except for VISA strain when the flavonoid was combined with vancomycin. Importantly, when myricetin was combined with oxacillin, MRSA strain became susceptible to the antibacterial. Myricetin did not reduce staphyloxanthin production, indicating that the oxacillin susceptibility seems not to be related to this step of functional membrane microdomains. In vivo evaluations using Galleria mellonella confirmed the efficacy of oxacillin plus myricetin in treatment of MRSA infected-larvae when compared to the control groups, increasing in 20% host survival. The present work points out the potential of antibacterial and antivirulence compounds combinations as new alternative to control infections by multidrug resistant-bacteria.

Antibacterial and antibiofilm effects of flufenamic acid against methicillin-resistant Staphylococcus aureus.

Methicillin-resistant Staphylococcus aureus (MRSA) infections are one of the most serious surgery complications, and their prevention is of utmost importance. Flufenamic acid is a non-steroid anti-inflammatory drug approved for clinical use to relieve inflammation and pain in rheumatoid arthritis patients. In this study, we explored the antibacterial efficacy of flufenamic acid and the mechanisms underlying this effect. By using minimal inhibitory concentration (MIC), time-kill, resistance induction assays, and the antibiotic synergy test, we demonstrated that flufenamic acid inhibited the growth of methicillin-resistant staphylococci and did not induce resistance when it was used at the MIC. Furthermore, flufenamic acid acted synergistically with the beta-lactam antibiotic oxacillin and did not show significant toxicity toward mammalian cells. The biofilm inhibition assay revealed that flufenamic acid could prevent biofilm formation on medical implants and destroy the ultrastructure of the bacterial cell wall. RNA sequencing and quantitative RT-PCR indicated that flufenamic acid inhibited the expression of genes associated with peptidoglycan biosynthesis, beta-lactam resistance, quorum sensing, and biofilm formation. Furthermore, flufenamic acid efficiently ameliorated a local infection caused by MRSA in mice. In conclusion, flufenamic acid may be a potent therapeutic compound against MRSA infections and a promising candidate for antimicrobial coating of implants and surgical devices.