Staphylococcus aureus: No ticket for the Paris 2024 Olympic Games!

Athletes are vulnerable to Staphylococcus aureus infections due to skin-to-skin contact and skin abrasions during training and competitions involving sharied sport equipment or toiletries, which promote the spread of the bacteria between athletes and within sport teams. This results not only in higher prevalence of S.aureus carriage among athletes compared to the general population, but also in outbreaks of infections, particularly skin infections, within sports teams. To limit the spread of S. aureus among athletes, a decolonization protocol can be applied when clustered cases of S. aureus infections occur, especially if Panton-Valentine leukocidin-producing strains are implicated. Finally, to avoid exposing athletes to S.aureus transmission/colonization, it is recommended to establish strict and clearly formulated individual and collective hygiene rules and to regularly disinfect shared sports equipment.

Exploring the virulence potential of Staphylococcus aureus CC121 and CC152 lineages related to paediatric community-acquired bacteraemia in Manhiça, Mozambique.

Staphylococcus aureus is a frequent agent of bacteraemia. This bacterium has a variety of virulence traits that allow the establishment and maintenance of infection. This study explored the virulence profile of S. aureus strains causing paediatric bacteraemia (SAB) in Manhiça district, Mozambique. We analysed 336 S. aureus strains isolated from blood cultures of children younger than 5 years admitted to the Manhiça District Hospital between 2001 and 2019, previously characterized for antibiotic susceptibility and clonality. The strains virulence potential was evaluated by PCR detection of the Panton-Valentine leucocidin (PVL) encoding genes, lukS-PV/lukF-PV, assessment of the capacity for biofilm formation and pathogenicity assays in Galleria mellonella. The overall carriage of PVL-encoding genes was over 40%, although reaching ~ 70 to 100% in the last years (2014 to 2019), potentially linked to the emergence of CC152 lineage. Strong biofilm production was a frequent trait of CC152 strains. Representative CC152 and CC121 strains showed higher virulence potential in the G. mellonella model when compared to reference strains, with variations within and between CCs. Our results highlight the importance of monitoring the emergent CC152-MSSA-PVL+ and other lineages, as they display important virulence traits that may negatively impact the management of SAB paediatric patients in Manhiça district, Mozambique.

Nasal carriage of virulent and multidrug resistant Staphylococcus aureus: a possible comorbidity of COVID-19.

BACKGROUND: Staphylococcus aureus (S. aureus) associated with COVID-19 has not been well documented. This cross-sectional study evaluated the association between nasal S. aureus carriage and COVID-19. METHODS AND RESULTS: Nasopharyngeal samples were collected from 391 participants presenting for COVID-19 test in Lagos, Nigeria, and S. aureus was isolated from the samples. Antimicrobial susceptibility test was done by disc diffusion method. All S. aureus isolates were screened for the presence of mecA, panton-valentine leucocidin (PVL) and toxic shock syndrome toxin (TSST) virulence genes by polymerase chain reaction. Staphylococcal protein A (spa) typing was conducted for all the isolates. Participants with COVID-19 had double the prevalence of S. aureus (42.86%) compared to those who tested negative (20.54%). A significant association was seen between S. aureus nasal carriage and COVID-19 (p = 0.004). Antimicrobial sensitivity results showed resistance to oxacillin (100%), cefoxitin (53%), and vancomycin (98.7%). However, only 41% of the isolates harbored the mecA gene, with SCCmecV being the most common SCCmec type. There was no association between the carriage of virulence genes and COVID-19. A total of 23 Spa types were detected, with t13249 and t095 being the two most common spa types. CONCLUSION: This study examined the association between nasal S. aureus carriage and SARS-COV-2 infection. Further research is required to fully explore the implications of S. aureus co-infection with COVID-19.

High Prevalence of Panton-Valentine Leukocidin Among Staphylococcus aureus Causing Acute Hematogenous Bone and Joint Infections From a Tertiary Children's Hospital in Vietnam.

BACKGROUND: We aimed to investigate the clinical features, antimicrobial susceptibility and pvl gene expression in Staphylococcus aureus causing acute hematogenous bone and joint infections (BJIs) in children in Vietnam. METHODS: In this prospective study, the demographics, microbiology and clinical outcomes of pediatric patients with acute hematogenous BJIs were collected from September 2022 to September 2023. Antimicrobial susceptibility profiles were determined using VITEK2 Compact system. The pvl gene encoding the Panton-Valentine leukocidin (PVL) toxin was detected by using polymerase chain reaction. Mann-Whitney, χ 2 and Fisher test were used for statistical analysis. RESULTS: In total, 78 patients (46 boys) with S. aureus acute hematogenous BJIs were recruited at the National Children's Hospital, Hanoi, Vietnam. Of all S. aureus isolates, 84.6% were methicillin-resistant S. aureus . All S. aureus isolates were susceptible to vancomycin, ciprofloxacin and levofloxacin; 97% of methicillin-resistant S. aureus isolates was resistant to clindamycin (minimum inhibitory concentration ≥8 µg/mL). The pvl gene was detected in 83.3% of isolates, including 57 methicillin-resistant S. aureus isolates. Patients in the pvl -positive group had significantly higher C-reactive protein levels than those in the pvl -negative group ( P = 0.04). In addition, all 8 children with septic shock were infected with pvl -positive S. aureus . CONCLUSIONS: PVL is a prevalent virulence factor of S. aureus in Vietnam. Furthermore, high inflammatory parameters (C-reactive protein) may be present at the time of diagnosis in PVL positivity-related acute hematogenous BJIs. Further research is necessary to enhance our understanding of the varying correlations between virulence factors and outcomes of S. aureus BJIs.

Detection of Staphylococcus aureus virulence gene pvl based on CRISPR strip.

Introduction: Staphylococcus aureus (S. aureus) is a prominent pathogen responsible for both hospital-acquired and community-acquired infections. Among its arsenal of virulence factors, Panton-Valentine Leucocidin (PVL) is closely associated with severe diseases such as profound skin infections and necrotizing pneumonia. Patients infected with pvl-positive S. aureus often exhibit more severe symptoms and carry a substantially higher mortality risk. Therefore, it is crucial to promptly and accurately detect pvl-positive S. aureus before initiating protective measures and providing effective antibacterial treatment. Methods: In this study, we propose a precise identification and highly sensitive detection method for pvl-positive S. aureus based on recombinase-assisted amplification and the CRISPR-ERASE strip which we previously developed. Results: The results revealed that this method achieved a detection limit of 1 copy/µL for pvl-positive plasmids within 1 hour. The method successfully identified all 25 pvl-positive and 51 pvl-negative strains among the tested 76 isolated S. aureus samples, demonstrating its concordance with qPCR. Discussion: These results show that the CRISPR-ERASE detection method for pvl-positive S. aureus has the advantages of high sensitivity and specificity, this method combines the characteristics of recombinase-assisted amplification at room temperature and the advantages of ERASE test strip visualization, which can greatly reduce the dependence on professional laboratories. It is more suitable for on-site detection than PCR and qPCR, thereby providing important value for rapid on-site detection of pvl.

Antimicrobial Resistance and the Prevalence of the Panton-Valentine Leukocidin Gene among Clinical Isolates of Staphylococcus aureus in Lithuania.

This study aimed to determine resistance to antimicrobials of Staphylococcus aureus strains isolated from clinical specimens in Lithuanian hospitals and to identify the genes conferring resistance and virulence. The study was carried out from June 2019 to September 2021. S. aureus strains were isolated from skin, soft tissues, blood, lower respiratory tract, urine and other specimens. Antibiotic susceptibility testing was performed using the disc diffusion method according to EUCAST guidelines. All isolates were analyzed for detection of the ermA, ermC, mecA, mecC, tetK, tetM, and lukF-PV genes by multiplex real-time PCR. The 16S rRNA coding sequence was applied as an internal PCR control. Altogether, 745 S. aureus strains were analyzed. Antimicrobial susceptibility testing revealed that all isolates were susceptible to rifampin and vancomycin. Of the 745 strains, 94.8% were susceptible to tetracycline, 94.5% to clindamycin, and 88.3% to erythromycin. The lowest susceptibility rate was found for penicillin (25.8%). Six percent of the tested strains were methicillin-resistant S. aureus (MRSA). The majority of methicillin-resistant strains were isolated from skin and soft tissues (73.3%), with a smaller portion isolated from blood (17.8%) and respiratory tract (8.9%). The ermC gene was detected in 41.1% of erythromycin-resistant S. aureus strains, whereas ermA was detected in 32.2% of erythromycin-resistant S. aureus strains. 69.2% of tetracycline-resistant S. aureus strains had tetK gene, and 28.2% had tetM gene. 7.3% of S. aureus isolates harbored lukF-PV gene. The frequency of the pvl gene detection was significantly higher in MRSA isolates than in methicillin-susceptible S. aureus isolates (p < 0.0001).

Epidemiology and clinical features of Skin and Soft Tissue Infections Caused by PVL-Positive and PVL-Negative Methicillin-Resistant Staphylococcus aureus Isolates in inpatients in China: a single-center retrospective 7-year study.

Previous studies have mainly focused on outpatient cases of skin and soft tissue infections (SSTIs), with limited attention to inpatient occurrences. Thus, we aimed to compare the clinical parameters of inpatients with SSTIs, performed genomic characterization, and determined the subtypes of Panton-Valentine leucocidin (PVL) bacteriophages of methicillin-resistant Staphylococcus aureus (MRSA) strains isolated from these patients. We found that PVL-positive patients had shorter hospital stays (mean, 9 vs. 24 days; p < 0.001) and abscess resolution durations (mean, 8 vs. 13 days; p < 0.01). PVL-positive MRSA-induced SSTIs were more frequently associated with abscesses [36/55 (65.5%) vs. 15/124 (12.1%), p < 0.001], with 52.7% undergoing incision and drainage; over 80% of PVL-negative patients received incision, drainage, and antibiotics. In PVL-positive patients receiving empirical antibiotics, anti-staphylococcal agents such as vancomycin and linezolid were administered less frequently (32.7%, 18/55) than in PVL-negative patients (74.2%, 92/124), indicating that patients with PVL-positive SSTIs are more likely to require surgical drainage rather than antimicrobial treatment. We also found that the ST59 lineage was predominant, regardless of PVL status (41.3%, 74/179). Additionally, we investigated the linear structure of the lukSF-PV gene, revealing that major clusters were associated with specific STs, suggesting independent acquisition of PVL by different strain types and indicating that significant diversity was observed even within PVL-positive strains detected in the same facility. Overall, our study provides comprehensive insights into the clinical, genetic, and phage-related aspects of MRSA-induced SSTIs in hospitalized patients and contributes to a more profound understanding of the epidemiology and evolution of these pathogens in the Chinese population.

Evolutionary dynamics of the novel ST22-PT methicillin-resistant Staphylococcus aureus clone co-harbouring Panton-Valentine leucocidin and duplicated toxic shock syndrome toxin 1 genes.

OBJECTIVES: Globally, the isolation of community-associated methicillin-resistant Staphylococcus aureus (MRSA) harbouring both the Panton-Valentine leucocidin (PVL) and toxic shock syndrome toxin 1 (TSST-1) genes is rare. However, we encountered an outbreak of the ST22-PT clone exhibiting this phenotype in Japan. Notably, the TSST-1 gene was duplicated in most of the strains. This study aimed to elucidate the mechanisms underlying this gene duplication. METHODS: A total of 90 MRSA isolates were collected from the skin of outpatients in Fukuoka City, Japan, between 2017 and 2019. Whole-genome sequencing was performed on MRSA strains that were PVL and TSST-1 positive. RESULTS: A total of 43 (47.8%) strains produced TSST-1, 20 (22.2%) produced PVL, and 16 (17.8%) produced both. Fifteen isolates were classified as ST22/SCCmec type IVa (ST22-PT clone) and one as ST1/SCCmec type V (ST1-PT clone). Three distinct ST22-PT clones were identified: Fukuoka clone I (one PVL gene and one TSST-1 gene), Fukuoka clone II (addition of a TSST-1 gene to Fukuoka clone I), and Fukuoka clone III (marked by a chromosomal inversion in a large region from Fukuoka clone II). DISCUSSION: Fukuoka clone I may have integrated a novel pathogenicity island bearing the TSST-1 gene, leading to the emergence of Fukuoka clone II with a duplicated TSST-1 gene. This duplication subsequently instigated a chromosomal inversion in a large region owing to the homologous sequence surrounding TSST-1, giving rise to Fukuoka clone III. These findings provide crucial insights into the genetic evolution of MRSA.

Staphylococcus aureus senses human neutrophils via PerR to coordinate the expression of the toxin LukAB.

Staphylococcus aureus is a gram-positive pathogen that poses a major health concern, in part due to its large array of virulence factors that allow infection and evasion of the immune system. One of these virulence factors is the bicomponent pore-forming leukocidin LukAB. The regulation of lukAB expression is not completely understood, especially in the presence of immune cells such as human polymorphonuclear neutrophils (hPMNs). Here, we screened for transcriptional regulators of lukAB during the infection of primary hPMNs. We uncovered that PerR, a peroxide sensor, is vital for hPMN-mediated induction of lukAB and that PerR upregulates cytotoxicity during the infection of hPMNs. Exposure of S. aureus to hydrogen peroxide (H2O2) alone also results in increased lukAB promoter activity, a phenotype dependent on PerR. Collectively, our data suggest that S. aureus uses PerR to sense the H2O2 produced by hPMNs to stimulate the expression of lukAB, allowing the bacteria to withstand these critical innate immune cells.IMPORTANCEStaphylococcus aureus utilizes a diverse set of virulence factors, such as leukocidins, to subvert human neutrophils, but how these toxins are regulated is incompletely defined. Here, we identified the peroxide-sensitive repressor, PerR, as a required protein involved in the induction of lukAB in the presence of primary human neutrophils, a phenotype directly linked to the ability of PerR to sense H2O2. Thus, we show that S. aureus coordinates sensing and resistance to oxidative stress with toxin production to promote pathogen survival.

Panton-Valentine leukocidin-induced neutrophil extracellular traps lack antimicrobial activity and are readily induced in patients with recurrent PVL + -Staphylococcus aureus infections.

Staphylococcus aureus strains that produce the toxin Panton-Valentine leukocidin (PVL-SA) frequently cause recurrent skin and soft tissue infections. PVL binds to and kills human neutrophils, resulting in the formation of neutrophil extracellular traps (NETs), but the pathomechanism has not been extensively studied. Furthermore, it is unclear why some individuals colonized with PVL-SA experience recurring infections whereas others are asymptomatic. We thus aimed to (1) investigate how PVL exerts its pathogenicity on neutrophils and (2) identify factors that could help to explain the predisposition of patients with recurring infections. We provide genetic and pharmacological evidence that PVL-induced NET formation is independent of NADPH oxidase and reactive oxygen species production. Moreover, through NET proteome analysis we identified that the protein content of PVL-induced NETs is different from NETs induced by mitogen or the microbial toxin nigericin. The abundance of the proteins cathelicidin (CAMP), elastase (NE), and proteinase 3 (PRTN3) was lower on PVL-induced NETs, and as such they were unable to kill S. aureus. Furthermore, we found that neutrophils from affected patients express higher levels of CD45, one of the PVL receptors, and are more susceptible to be killed at a low PVL concentration than control neutrophils. Neutrophils from patients that experience recurring PVL-positive infections may thus be more sensitive to PVL-induced NET formation, which might impair their ability to combat the infection.

[Genitoanal infections caused by Panton-Valentine leukocidin (PVL)-positive Staphylococcus aureus : Smear infection or sexually transmitted disease?] / Genitoanale Infektionen durch Panton-Valentine-Leukozidin(PVL)-positiven Staphylococcus aureus : Schmierinfektion oder sexuell übertragbare Erkrankung?

Panton-Valentine leukocidin (PVL) is a pore-forming exotoxin produced by certain Staphylococcus (S.) aureus strains, which is responsible for the increased virulence of the pathogen. Thus, infections caused by PVL-positive S. aureus tend to recur. Usually, the infection is a smear infection, which can cause folliculitis and purulent lid margin inflammation in addition to the classic mucocutaneous abscesses. Recently, recurrent genitoanal infections caused by PVL-positive S. aureus have also been described. In most cases, this is a sexually transmitted disease. Currently, it is assumed that most infections are imported from abroad. In addition to treatment of these infections, decolonization should be performed for prophylaxis of recurrence.

Emergence and control of an outbreak of PVL-positive MRSA in a UK-based maternity setting.

This paper aims to describe the investigation and control of an outbreak of USA300 ST8 Panton-Valentine leucocidin (PVL)-positive meticillin-resistant Staphylococcus aureus (MRSA), confirmed by whole genome sequencing (WGS), within a maternity and neonatal setting in the UK. The identification of two linked PVL-MRSA cases led to an outbreak investigation. A lookback exercise conducted using the infection control surveillance database, typing of saved MRSA isolates, enhanced patient screening, and staff screening were used to identify further cases. Environmental screening was also performed. Genetic relatedness between isolates was assessed by WGS. During the outbreak, 18 cases were identified between 11th July 2021 and 22nd December 2022: 10 cases were infections and eight cases were colonizations. A healthcare worker (HCW) tested positive for colonization with the same strain, and environmental swabbing identified contaminated information technology equipment in the hospital. The outbreak was brought to an end by exclusion of the colonized HCW from work, and infection prevention and control measures. Since the end of the outbreak, cases of PVL-MRSA with similar molecular profiles have been found in the community. It is likely that the HCW played a role in the transmission of PVL-MRSA. Their exclusion from work and decolonization were key to preventing further cases. WGS was valuable in identifying and linking cases. The identification of community cases of PVL-MRSA with similar molecular profiles confirms transmission of the organism outside of healthcare settings.

Genomic characterization of a unique Panton-Valentine leucocidin-positive community-associated methicillin-resistant Staphylococcus aureus lineage increasingly impacting on Australian indigenous communities.

In 2010 a single isolate of a trimethoprim-resistant multilocus sequence type 5, Panton-Valentine leucocidin-positive, community-associated methicillin-resistant Staphylococcus aureus (PVL-positive ST5 CA-MRSA), colloquially named WA121, was identified in northern Western Australia (WA). WA121 now accounts for ~14 % of all WA MRSA infections. To gain an understanding of the genetic composition and phylogenomic structure of WA121 isolates we sequenced the genomes of 155 WA121 isolates collected 2010-2021 and present a detailed genomic description. WA121 was revealed to be a single clonally expanding lineage clearly distinct from sequenced ST5 strains reported outside Australia. WA121 strains were typified by the presence of the distinct PVL phage φSa2wa-st5, the recently described methicillin resistance element SCCmecIVo carrying the trimethoprim resistance (dfrG) transposon Tn4791, the novel ß-lactamase transposon Tn7702 and the epidermal cell differentiation inhibitor (EDIN-A) plasmid p2010-15611-2. We present evidence that SCCmecIVo together with Tn4791 has horizontally transferred to Staphylococcus argenteus and evidence of intragenomic movement of both Tn4791 and Tn7702. We experimentally demonstrate that p2010-15611-2 is capable of horizontal transfer by conjugative mobilization from one of several WA121 isolates also harbouring a pWBG749-like conjugative plasmid. In summary, WA121 is a distinct and clonally expanding Australian PVL-positive CA-MRSA lineage that is increasingly responsible for infections in indigenous communities in northern and western Australia. WA121 harbours a unique complement of mobile genetic elements and is capable of transferring antimicrobial resistance and virulence determinants to other staphylococci.

Detection and characterization of potential virulence determinants in Staphylococcus pseudintermedius and S. schleiferi strains isolated from canine otitis externa in Korea.

BACKGROUND: A recent increase in the occurrence of canine skin and soft tissue infections, including otitis externa and pyoderma, caused by antimicrobial-resistant Staphylococcus pseudintermedius and S. schleiferi has become a significant public and veterinary health issues. OBJECTIVE: We investigated the virulence potentials associated with the occurrence of canine otitis externa in S. pseudintermedius and S. schleiferi. METHODS: In this study, the prevalence of genes encoding leukocidins, exfoliative toxins, and staphylococcal enterotoxins (SEs) was investigated using previously characterized S. pseudintermedius (n = 26) and S. schleiferi (n = 19) isolates derived from canine otitis externa. Susceptibility to cathelicidins (K9CATH and PMAP-36) and hydrogen peroxide (H2O2) was also examined in both staphylococcal species. RESULTS: A high prevalence of genes encoding leukocidins (lukS/F-I, lukS1/F1-S, and lukS2/F2-S), exfoliative toxins (siet, expB, and sset), and SEs was identified in both S. pseudintermedius and S. schleiferi isolates. Notably, S. pseudintermedius isolates possessed higher number of SE genes, especially newer SE genes, than S. schleiferi isolates harboring egc clusters. Although no significant differences in susceptibility to K9CATH and H2O2 were observed between the two isolate groups, S. pseudintermedius isolates exhibited enhanced resistance to PMAP-36 compared to S. schleiferi isolates. CONCLUSIONS: These findings suggest that high a prevalence of various toxin genes together with enhanced resistance to cathelicidins may contribute to the pathogenicity of S. pseudintermedius and S. schleiferi in canine cutaneous infections.

High prevalence of Panton-Valentine Leucocidin among Staphylococcus coagulans isolated from dogs in Rio de Janeiro.

AIMS: The purpose of this study was to characterize the capacity for biofilm formation, antimicrobial resistance rates, and search for genetic determinants of resistance and virulence in the species. METHODS AND RESULTS: Strains were collected from asymptomatic and infected dogs. Identification was conducted using matrix-assisted laser desorption ionization-time of flight (MALDI-TOF), antimicrobial susceptibility using disk diffusion and PCR targeting mecA. Biofilm formation was evaluated on a microtiter plate assay. A total of 27 strains were selected for whole-genome sequencing. We identified 111 Staphylococcus coagulans. The highest number was obtained from infected dogs. The highest resistance rates were observed for penicillin, gentamicin, and ciprofloxacin/erythromycin. Twelve strains were characterized as resistant to methicillin. All isolates had the ability to form biofilm and were strong producers. Among Methicillin Resistant Staphylococcus coagulans (MRSC), SCCmec types IIIA, and Vc were identified. Acquired resistance genes, such as aac(6')-aph(2''), tet(K), blaZ, qacG, qacJ, and erm(C) were found. Different virulence genes were identified. Of note, Panton-Valentine Leucocidin was highly prevalent among the isolates. CONCLUSION: Staphylococcus coagulans had a high isolation rate among infected dogs and demonstrated significant resistance to commonly used antibiotics such as penicillin and gentamicin.

Monoclonal antibodies neutralizing alpha-hemolysin, bicomponent leukocidins, and clumping factor A protected against Staphylococcus aureus-induced acute circulatory failure in a mechanically ventilated rabbit model of hyperdynamic septic shock.

Background: Patients with septic shock caused by Staphylococcus aureus have mortality rates exceeding 50%, despite appropriate antibiotic therapy. Our objectives were to establish a rabbit model of S. aureus septic shock and to determine whether a novel immunotherapy can prevent or halt its natural disease progression. Methods: Anesthetized rabbits were ventilated with lung-protective low-tidal volume, instrumented for advanced hemodynamic monitoring, and characterized for longitudinal changes in acute myocardial dysfunction by echocardiography and sepsis-associated biomarkers after S. aureus intravenous challenge. To demonstrate the potential utility of this hyperdynamic septic shock model for preclinical drug development, rabbits were randomized for prophylaxis with anti-Hla/Luk/ClfA monoclonal antibody combination that neutralizes alpha-hemolysin (Hla), the bicomponent pore-forming leukocidins (Luk) including Panton-Valentine leukocidin, leukocidin ED, and gamma-hemolysin, and clumping factor A (ClfA), or an irrelevant isotype-matched control IgG (c-IgG), and then challenged with S. aureus. Results: Rabbits challenged with S. aureus, but not those with saline, developed a hyperdynamic state of septic shock characterized by elevated cardiac output (CO), increased stroke volume (SV) and reduced systemic vascular resistance (SVR), which was followed by a lethal hypodynamic state characterized by rapid decline in mean arterial pressure (MAP), increased central venous pressure, reduced CO, reduced SV, elevated SVR, and reduced left-ventricular ejection fraction, thereby reproducing the hallmark clinical features of human staphylococcal septic shock. In this model, rabbits pretreated with anti-Hla/Luk/ClfA mAb combination had 69% reduction in mortality when compared to those pretreated with c-IgG (P<0.001). USA300-induced acute circulatory failure-defined as >70% decreased in MAP from pre-infection baseline-occurred in only 20% (2/10) of rabbits pretreated with anti-Hla/Luk/ClfA mAb combination compared to 100% (9/9) of those pretreated with c-IgG. Prophylaxis with anti-Hla/Luk/ClfA mAb combination halted progression to lethal hypodynamic shock, as evidenced by significant protection against the development of hyperlactatemia, hypocapnia, hyperkalemia, leukopenia, neutropenia, monocytopenia, lymphopenia, as well as biomarkers associated with acute myocardial injury. Conclusion: These results demonstrate the potential utility of a mechanically ventilated rabbit model that reproduced hallmark clinical features of hyperdynamic septic shock and the translational potential of immunotherapy targeting S. aureus virulence factors for the prevention of staphylococcal septic shock.

Infectious hazards of tatami mats.

A 16-year old girl consulted for repeated axillary abscesses. The bacteriological culture yielded monomicrobial Staphylococcus aureus. Faced with these recurrent abscesses in an immunocompetent patient playing a close contact sport, the biologist suspected the strain to harbor a virulence factor explaining these recurrences.

Panton-Valentine Leukocidin (PVL) genes may not be a reliable marker for community-acquired MRSA in the Dakahlia Governorate, Egypt.

BACKGROUND: Methicillin-resistant Staphylococcus aureus is linked to both nosocomial and community infections. One of the key virulence factors of S. aureus is Panton-Valentine leukocidin (PVL). The PVL genes are mostly associated with community-acquired MRSA (CA-MRSA). This study evaluates the prevalence of PVL genes as a marker for CA-MRSA at tertiary hospitals in Mansoura, Dakahlia, Egypt. S. aureus was isolated from clinical specimens obtained from different departments of tertiary hospitals, outpatient clinics, and hospital healthcare workers (HCWs). PCR was used to detect the mecA, PVL, and SCCmec genes among the recovered isolates. Standard broth microdilution method was used to determine the minimum inhibitory concentrations (MIC) of nine antibiotics against S. aureus. RESULTS: Two hundred S. aureus isolates were recovered and identified out of the total isolates (n = 320). The mecA gene was detected in 103 S. aureus isolates (51.5%). Among the MRSA isolates, 46.60% were PVL-positive. The incidence of the PVL genes of MRSA in nosocomial (HA), outpatient clinics (CA), and HCWs was 46.66%, 56.52%, and 42%, respectively. All MRSA isolates showed resistance to cefoxitin. The percentage of resistance to most tested antibiotics was high, except for ciprofloxacin (6.85%). Both antibiotic resistance and multidrug resistance among MRSA isolates were generally higher in PVL-positive isolates than in PVL-negative isolates in HA- and CA-MRSA isolates. While SCCmec type V was the most prevalent in PVL-positive MRSA stains, type I was the most prevalent in PVL-negative isolates. CONCLUSION: This study revealed that PVL genes are generally highly prevalent among mecA-positive MRSA isolates, whether they are CA-MRSA, HA-MRSA, or HCW isolates. Therefore, PVL is not a valid marker for CA-MRSA in Mansoura, Dakahlia Governorate, Egypt, as has been reported in other countries. Further epidemiologic studies are required to track the incidence of PVL in HA-MRSA, CA-MRSA, and HCW isolates in other Egyptian governorates.

Unlatching of the stem domains in the Staphylococcus aureus pore-forming leukocidin LukAB influences toxin oligomerization.

Staphylococcus aureus (S. aureus) is a serious global pathogen that causes a diverse range of invasive diseases. S. aureus utilizes a family of pore-forming toxins, known as bi-component leukocidins, to evade the host immune response and promote infection. Among these is LukAB (leukocidin A/leukocidin B), a toxin that assembles into an octameric ß-barrel pore in the target cell membrane, resulting in host cell death. The established cellular receptor for LukAB is CD11b of the Mac-1 complex. Here, we show that hydrogen voltage-gated channel 1 is also required for the cytotoxicity of all major LukAB variants. We demonstrate that while each receptor is sufficient to recruit LukAB to the plasma membrane, both receptors are required for maximal lytic activity. Why LukAB requires two receptors, and how each of these receptors contributes to pore-formation remains unknown. To begin to resolve this, we performed an alanine scanning mutagenesis screen to identify mutations that allow LukAB to maintain cytotoxicity without CD11b. We discovered 30 mutations primarily localized in the stem domains of LukA and LukB that enable LukAB to exhibit full cytotoxicity in the absence of CD11b. Using crosslinking, electron microscopy, and hydroxyl radical protein footprinting, we show these mutations increase the solvent accessibility of the stem domain, priming LukAB for oligomerization. Together, our data support a model in which CD11b binding unlatches the membrane penetrating stem domains of LukAB, and this change in flexibility promotes toxin oligomerization.