Panton-Valentine Leukocidin Research Articles

Computational Study of Antimicrobial Peptides for Promising Therapeutic Applications Against Methicillin-resistant Staphylococcus Aureus.

Methicillin-resistant Staphylococcus aureus (MRSA) is a causative agent for multiple drug-resistant diseases and is a prime health concern. Currently, antibiotics like vancomycin, daptomycin, fluoroquinolones, linezolid, fifth-generation cephalosporin and others are available in the market for the treatment of MRSA infection. With the increasing prevalence of drug-resistant cases, researchers are actively investigating alternative strategies to combat MRSA, including the exploration of peptide therapeutics. This study employed computational methods to prospect for potential Antimicrobial Peptides (AMPs). A total of One hundred and fifty antimicrobial peptides were explored based on physicochemical properties. The results showed that Clavanin B was the most appropriate candidate. Molecular Docking and Molecular Dynamics Simulation results showed the protein-peptide interaction of the MRSA target proteins, Penicillin Binding Protein 2a and Panton-Valentine Leukocidin Toxin, with the Antimicrobial Peptide Clavanin B. Currently, the antimicrobial peptide database highlights Clavanin B's role as an anti-HIV peptide. Moreover, this investigation proposes Clavanin B as a viable repurposed drug for treating MRSA, underscoring its potential deployment in the management of MRSA infections.

Staphylococcus aureus Panton-Valentine Leukocidin worsens acute implant-associated osteomyelitis in humanized BRGSF mice.

Staphylococcus aureus is the most common pathogen that causes implant-associated osteomyelitis, a clinically incurable disease. Immune evasion of S. aureus relies on various mechanisms to survive within the bone niche, including the secretion of leukotoxins such as Panton-Valentine leukocidin (PVL). PVL is a pore-forming toxin exhibiting selective human tropism for C5a receptors (C5aR1 and C5aR2) and CD45 on neutrophils, monocytes, and macrophages. PVL is an important virulence determinant in lung, skin and soft tissue infections. The involvement of PVL in S. aureus pathogenesis during bone infections has not been studied extensively yet. To investigate this, humanized BALB/c Rag2-/-Il2rg-/-SirpaNODFlk2-/- (huBRGSF) mice were subjected to transtibial implant-associated osteomyelitis with community-acquired methicillin-resistant S. aureus (CA-MRSA) USA300 wild type strain (WT), an isogenic mutant lacking lukF/S-PV (Δpvl), or complemented mutant (Δpvl+pvl). Three days post-surgery, Δpvl-infected huBRGSF mice had a less severe infection compared to WT-infected animals as characterized by 1) improved clinical outcomes, 2) lower ex vivo bacterial bone burden, 3) absence of staphylococcal abscess communities (SACs) in their bone marrow, and 4) compromised MRSA dissemination to internal organs (liver, kidney, spleen, heart). Interestingly, Δpvl-infected huBRGSF mice had fewer human myeloid cells, neutrophils, and HLA-DR+ monocytes in the bone niche compared to WT-infected animals. Expectedly, a smaller fraction of human myeloid cells were apoptotic in the Δpvl-infected huBRGSF animals. Taken together, our study highlights the pivotal role of PVL during acute implant-associated osteomyelitis in humanized mice.

Molecular detection of pore-forming leuko toxin in methicillin resistant Staphylococcus aureus isolated from skin infection

Abstract Background: The ability of Staphylococcus aureus to cause disease has been attributed to an impressive spectrum of virulence factors. Objective: The study investigated molecular detection of pore-forming leuko toxin (Panton–Valentine leucocidin [PVL]) in S. aureus that is resistant to methicillin (MRSA) isolated from skin infections. Materials and Methods: All 100 isolates of S. aureus were obtained from clinical samples (burn, wound, impetigo, boil, acne, abuses, folliculated, infected atopic dermatitis, and secondary infection), and 24 of these had been confirmed as MRSA. Antibiotic susceptibility patterns, mecA, 16sRNA, and PVL genes were isolated and detected by polymerase chain reaction (PCR). Results: All isolates were determined to be resistant to cefoxitin discs and oxacillin by using phenotypic analysis, and a genotypic investigation revealed that 79.16% of them carried the mecA gene. Additionally, the data showed that 58.33% of MRSA isolates contain the PVL gene and 83.33%% of MRSA isolates harbor of 16sRNA gene. Conclusions: The study detected a high S. aureus isolates percentage in a burn, followed by impetigo, wound, and boil, respectively. A higher percentage of MRSA isolates contain the PVL gene, mecA, and harbor of 16sRNA gene.

Antimicrobial resistance profile of Staphylococcus aureus isolated from patients, healthcare workers, and the environment in a tertiary hospital in Addis Ababa, Ethiopia.

Staphylococcus aureus infection and colonization in patients may be transmitted to healthcare providers and the environment and subsequently cause healthcare-associated infections in other patients. Pathogenic S. aureus strains produce virulence factors, such as Panton-Valentine Leukocidin (PVL), that contribute to the severity of infections and aid in their spread. The emergence of antimicrobial resistance (AMR) is additional concern with respect to S. aureus infection. In this study, the virulence genes and antibiotic resistance profiles of S. aureus were characterized from patients' clinical isolates, healthcare workers' (HCWs') nasal colonization screenings, and the environment at a tertiary healthcare hospital in Addis Ababa, Ethiopia. A total of 365 samples were collected from September 2021 to September 2022: 73 patients' clinical specimens, 202 colonization screenings from HCWs, and 90 hospital environment's swabs. Fifty-one (25.2%) HCW and 10/90 (11.1%) environment S. aureus isolates were identified. Among the 134 isolates, 10 (7.5%) were methicillin-resistant S. aureus (MRSA). Three (4.1%), five (9.8%), and two (20.0%) of the MRSA isolates were identified from the patients, HCWs, and the environment, respectively. Overall, 118 (88.1%) were ampicillin and penicillin resistant; 70 (52.2%) were trimethoprim sulfamethoxazole resistant; and 28 (20.9%) were erythromycin resistant. S. aureus isolates from patients were more resistant to antibiotics than isolates from HCWs or the hospital environment (p<0.05). A total of 92/134 (68.6%) isolates possessed the lukfF-PV gene, which was identified in 62 (85.0%), 26 (51.0%), and 4 (40.0%) of the patient, HCWs, and the environment, respectively. The proportion of lukfF-PV gene containing S. aureus isolated from patient samples was statistically significant. Four (40.0%) of the MRSA isolates also had the lukfF-PV gene. The identification of highly AMR and virulence factors from patients, HCWs and the environment is concerning. Further studies are needed to identify potential transmission links and improve infection prevention and control.

Faktori virulencije Staphylococcus aureus i njihov značaj u infekcijama povezanim sa biofilmom

Although Staphylococcus aureus colonises the skin and mucous membranes in approximately 30% of healthy individuals, it is also an important pathogen, primarily due to its arsenal of virulence factors that contribute significantly to its ability to cause a variety of infections. These factors include surface proteins that promote adhesion to host tissues, as well as enzymes and toxins that damage host cells and tissue. Important virulence factors such as protein A, which binds to antibodies and evades recognition by the immune system, and various exotoxins such as Alpha-toxin and Panton-Valentine leukocidin, which cause cell lysis and tissue destruction, play a crucial role in pathogenesis. The ability of S. aureus to form biofilms on medical devices further increases its persistence and resistance to therapy. Biofilms are structured communities of bacterial cells that are enclosed in a self-produced polymeric matrix and that adhere to biotic or abiotic surfaces. Biofilm-related infections caused by S. aureus, such as infections of medical devices (catheters, prosthetic joints, heart valves, intravascular catheters) and human tissue (chronic rhinosinusitis, chronic wounds, endocarditis and osteomyelitis), are a significant concern in medical settings. Understanding these virulence mechanisms is crucial for the development of targeted therapies and preventive measures to effectively combat S. aureus infections.

Puerperal mastitis caused by limited community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) clones.

To outline the epidemiology of puerperal mastitis caused by methicillin-resistant Staphylococcus aureus (MRSA) and evaluate the effect of an infection control bundle on its incidence. A surge in MRSA puerperal mastitis was noted in a community hospital in September 2009. MRSA samples from mastitis cases and the environment underwent typing using multilocus sequence typing (MLST), staphylococcal cassette chromosome mec (SCCmec), gene encoding surface protein A (spa), accessory gene regulator (agr), and pulsed-field gel electrophoresis (PFGE). The phenotypic characteristics, including superantigen toxin profiles, gene encoding Panton-Valentine leucocidin (pvl), and minimal inhibitory concentration (MIC) against vancomycin, were ascertained. Subsequently, an infection control bundle emphasizing contact precautions was introduced, and mastitis incidence rates pre- and post-intervention were compared. The majority of cases occurred within 6 weeks post-delivery in first-time mothers. Of the 42 S. aureus isolates (27 from mastitis and 15 from colonized staff and environmental sources), 25 (92.6%) clinical and 3 (20%) colonized MRSA were identified as ST59-SCCmecVT-spa t437-agr group I with a vancomycin MIC of 1 mg/L, pvl-positive, and predominantly with a consistent toxin profile (seb-selk-selr). PFGE revealed 13 patterns; pulsotype B exhibited clonal relatedness between two clinical and three colonized MRSA samples. Post-intervention, the incidence of both mastitis and MRSA mastitis notably decreased from 13.01 to 1.78 and from 3.70 to 0.99 episodes per 100 deliveries, respectively. Distinct community-associated MRSA (CA-MRSA) clones were detected among puerperal mastitis patients and colonized staff. The outbreak was effectively controlled following the implementation of a targeted infection control bundle.

Diversity of Staphylococcus aureus isolated from nares of ruminants.

To examine the diversity of Staphylococcus aureus isolated from nasal swabs of ruminants in Rwanda. A total of 454 nasal swabs from 203 cows, 170 goats, and 81 sheep were examined for the presence of S. aureus, and 30 S. aureus isolates were detected and characterized pheno- and genotypically. Resistance to penicillin and/or tetracycline was observed. The isolates were assigned to eight different spa types (t21057 (novel), t10103, t18853, t20842, t318, t355, t458, and t9432) belonging to six clonal complexes (CCs) (CC152, CC30, CC3591, CC3666, CC522, and CC97). Panton-Valentine leukocidin (PVL) genes (lukF-PV/lukS-PV), the bovine leukocidin genes (lukM/lukF-P83), and the human and bovine variants of the toxic shock syndrome toxin gene tst-1 variants were detected. These findings demonstrate that the nares of ruminants in Rwanda are colonized with mastitis-associated S. aureus, including lineages that are also carried by humans, underscoring the zoonotic risk, especially for livestock keepers. These results highlight the crucial importance of hygiene measures when handling livestock.

A Rare Case of Panton-Valentine Leukocidin-Related Cervical Empyema

Abstract Staphylococcus aureus is found in the normal skin and mucosa of approximately 30% of healthy populations and is the most common pathogen in human disease associated with bacteria. They are divided into methicillin-sensitive S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA). The S. aureus strains carrying the Panton-Valentine leukocidin genes (SA-PVL) were initially believed to belong to the MRSA group; however, recent reports showed they also belonged to the MSSA group (MSSA-PVL). SA-PVL is common in skin and soft-tissue infections but rare in musculoskeletal infections, especially in spondylodiscitis. We are reporting a case suffering from cervical spondylodiscitis and epidural abscess associated with MSSA carrying the Panton-Valentine leukocidin genes.

Molecular Characteristics and Pathogenicity of Staphylococcus aureus Exotoxins.

Staphylococcus aureus stands as one of the most pervasive pathogens given its morbidity and mortality worldwide due to its roles as an infectious agent that causes a wide variety of diseases ranging from moderately severe skin infections to fatal pneumonia and sepsis. S. aureus produces a variety of exotoxins that serve as important virulence factors in S. aureus-related infectious diseases and food poisoning in both humans and animals. For example, staphylococcal enterotoxins (SEs) produced by S. aureus induce staphylococcal foodborne poisoning; toxic shock syndrome toxin-1 (TSST-1), as a typical superantigen, induces toxic shock syndrome; hemolysins induce cell damage in erythrocytes and leukocytes; and exfoliative toxin induces staphylococcal skin scalded syndrome. Recently, Panton-Valentine leucocidin, a cytotoxin produced by community-associated methicillin-resistant S. aureus (CA-MRSA), has been reported, and new types of SEs and staphylococcal enterotoxin-like toxins (SEls) were discovered and reported successively. This review addresses the progress of and novel insights into the molecular structure, biological activities, and pathogenicity of both the classic and the newly identified exotoxins produced by S. aureus.

Characterization of Staphylococcus aureus Nasal Carriage Among Healthcare Providers in an Intensive Care Unit: Insights into Antibiotic Resistance Profiles and Virulence Gene Distribution

Background: Staphylococcus aureus ranks among the leading causes of serious nosocomial infections. One critical route for the spread of this bacterium within hospitals is via asymptomatic carriers, particularly healthcare providers. Staphylococcus aureus can exist as part of the normal skin flora and within the anterior nostrils of individuals, making healthcare providers a significant vector for transmission. Several genes associated with virulence, such as toxic shock syndrome toxin-1 (tsst-1), alpha-toxin (hla), and panton-valentine leucocidin (pvl), play pivotal roles in the pathogenicity and severity of infections caused by S. aureus. Objectives: This study aimed to characterize S. aureus nasal carriage among healthcare providers in an intensive care unit (ICU), with a particular focus on antibiotic resistance profiles and the prevalence of virulence genes. Methods: Nasal swabs were collected from 120 healthcare workers in the ICU of Ganjavian hospital, Dezful, Iran. Standard microbiological procedures were employed for S. aureus detection. Antibiotic susceptibility testing was conducted using both disk diffusion and minimum inhibitory concentration methods. Polymerase chain reaction (PCR) was employed to identify the presence of the mecA gene and the virulence genes hla, tsst-1, and pvl. A statistical analysis was performed to evaluate the data. Results: The study revealed that 12.5% of healthcare providers were carriers of S. aureus, with 26.6% of them harboring methicillin-resistant S. aureus (MRSA) strains. Antibiotic resistance patterns varied, with a notable resistance to erythromycin and penicillin. The hla gene was detected in 66.6% of S. aureus strains; nevertheless, the tsst-1 and pvl genes were not identified. The study suggests a potential association between high expression of the hla and mecA genes and antibiotic resistance. Conclusions: This study underscores the prevalence of S. aureus nasal carriage, antibiotic resistance patterns, and the distribution of virulence genes among healthcare providers in an ICU setting. The findings emphasize the significance of continuous surveillance and infection control strategies to mitigate the transmission of S. aureus and associated infections within healthcare facilities. The study recommends routine screening of ICU healthcare providers for asymptomatic S. aureus carriers and appropriate interventions to eliminate colonization.

Genetic characterization of methicillin-resistant / susceptible Staphylococcus aureus (MRSA/MSSA) and Staphylococcus argenteus clinical isolates in Bangladesh: Dominance of ST6-MRSA-IV/t304 and detection of cfr/fexA in ST8-MSSA/t008

ObjectivesCoagulase-positive staphylococcus (CoPS), represented by Staphylococcus aureus, is a major cause of infections in humans. This study aimed to investigate molecular epidemiological characteristics, antimicrobial resistance, and their trends of CoPS in Bangladesh. MethodsClinical isolates of CoPS were collected from two medical institutions in Bangladesh for a 2-year period and analyzed for their species, genotypes, virulence factors, antimicrobial susceptibility, and resistance determinants. Results172 CoPS isolates collected were identified as S. aureus or S. argenteus (170 and two, respectively). Methicillin-resistant S. aureus (MRSA) accounted for 36% (n = 61), having Staphylococcal cassette chromosome mec (SCCmec)-IV (82%) or V (18%). Panton-Valentine leukocidin (PVL) genes were detected at higher rate in methicillin-susceptible S. aureus (MSSA) (62%) than MRSA (26%). MRSA comprised 11 STs, including a dominant type ST6 (46%) associated with mostly SCCmec-IVa/spa-t304, and one isolate had genetic features of the USA300 clone (ST8/SCCmec-IVa/coa-IIIa/spa-t008/ACME-I/ΦSa2USA). STs of CC1, CC88, and CC398 were common in MSSA, with CC88 showing the highest PVL-positive rate. One MSSA isolate (ST8/spa-t008) harbored fexA and cfr showing susceptibility to linezolid. S. argenteus was methicillin-susceptible and belonged to ST2250/coa-XId. ConclusionsGenetic characteristics of current MRSA/MSSA in Bangladesh were revealed, with first identification of S. argenteus at low prevalence.

A Study of Community-Acquired Pyodermas with Special Reference to Panton-Valentine Leukocidin (PVL)-Positive Methicillin-Resistant Staphylococcus Aureus.

Community-acquired (CA) pyodermas are one of the most common infections encountered in the dermatology outpatient clinics. A significant number of these conditions are caused by Staphylococcus aureus. CA-methicillin-sensitive Staphylococcus aureus (MSSA) and CA-methicillin-resistant Staphylococcus aureus (MRSA) have specific virulence genes which are associated with these diseases, particularly the Panton-Valentine leukocidin (PVL) genes. The presence of the PVL gene as a virulence factor may be associated with recurrent and severe skin infections. A prospective study was conducted with 205 cases of CA pyodermas, of which five were discarded due to mixed isolates. Clinical details were taken and wound exudate was sent for bacteriological examination. Further, the molecular study was performed on all MRSA (7) isolates and 13 randomly selected MSSA isolates using polymerase chain reaction for mecA and PVL genes. Staphylococcus aureus was the most common organism (90%) isolated from primary or secondary CA pyodermas. The prevalence of CA-MRSA among all pyodermas was 3.5% in our community. The PVL gene was not detected in all tested CA-MRSA and CA-MSSA isolates. While pyodermas are common, the prevalence of MRSA is low in the CA pyodermas in our region. PVL does not appear to be a virulence factor among the isolated MRSA. Larger, multicentric, and periodic studies are, however, required to further justify these claims.

The prevalence of Staphylococcus aureus and the emergence of livestock-associated MRSA CC398 in pig production in eastern China.

Livestock-associated Staphylococcus aureus (LA-MRSA) has been of increasing concern due to its potential risk to humans. This study investigated the prevalence of MRSA in pig production in Eastern China and determined the genomic characteristics of pig-associated MRSA isolates by whole-genome sequencing (WGS). A total of 1,318 samples were collected from pig farms and pig slaughterhouses, and 150 S. aureus were identified, including 63 MRSA isolates and 87 MSSA isolates. MRSA was detected in all pig farms and pig slaughterhouses. The antimicrobial susceptibility test revealed that all MRSA isolates were multidrug-resistant. The WGS and MLST analysis demonstrated that 56 MRSA isolates belonged to clonal complex (CC) 398, and seven MRSA isolates belonged to CC9. All LA-MRSA isolates were absent of phiSa3 phage containing immune evasion cluster (IEC) and possessed an intact hlb gene. In addition, genes associated with Panton-Valentine leukocidin, typically indicative of human adaptation, were not detected. The analysis of antibiotic resistance genes (ARGs) demonstrated that all MRSA isolates contained multiple ARGs. All MRSA isolates had Plthe mecA gene and at least one tetracycline resistance gene. Both tetM and tetK were detected in all MRSA CC398 isolates, while tetL was detected in all MRSA CC9 isolates. The phenicol resistance gene fexA was detected in 51 MRSA isolates, while the linezolid resistance gene cfr was detected in 60 MRSA isolates. The emergence of LA-MRSA CC398 in four pig farms and one slaughterhouse in this study indicates the spread of this clonal complex in the pig production sector in Eastern China. Further investigations are required to understand the potential transmission routes of LA-MRSA CC398 within the pork production chain in China and to assess the potential risks to humans.

Methicillin-resistant staphylococci in clinical bovine mastitis: occurrence, molecular analysis, and biofilm production.

Staphylococcus aureus is an important pathogen that causes mastitis in cattle, and the emergence of methicillin-resistant S. aureus (MRSA) poses a threat to veterinary and human medicine. The aims of the study were to investigate the prevalence of MRSA and methicillin-resistant coagulase-negative staphylococci (MR-CoNS) isolated from clinical mastitis, their ability to form biofilms, and the antimicrobial susceptibility of S. aureus strains. In addition, the Staphylococcal Cassette Chromosome mec (SCCmec) type, spa type and the presence of Panton-Valentine Leucocidin in MRSA were evaluated. A total of 326 staphylococcal strains were screened by multiplex-PCR for S. aureus and Staphylococcus intermedius group (SIG) identification. The S. aureus strains (n = 163) were subjected to phenotypic testing for antimicrobial susceptibility and biofilm formation. Molecular analysis was performed on MRSA mecA-positive strains. Of 163 S. aureus isolates, 142 strains (87.1%) were resistant to at least one antibiotic, and all 19 MRSA strains were resistant to at least four out of five antibiotics tested. All S. aureus strains harboured the icaA gene and were biofilm producers. Nineteen MR-CoNS strains were also isolated. The most prevalent spa types among MRSA were t001 (57.9%) and t037 (31.6%), while one MRSA was type t008 and one was type t041. Most MRSA were SCCmec type I (63.2%) and III (31.6%) and only one strain was type IV. None of the MRSA isolates had the PVL gene. The prevalence of multidrug-resistant S. aureus in bovine mastitis is a serious concern. The finding of MRSA with spa types predominant in humans and infrequent in Italian cows and with SCCmec infrequently found in bovine milk or cheese suggest a human origin of these strains. The ability of MRSA and MR-CoNS involved in bovine mastitis to be transferred to humans and vice versa poses a public health concern.

Molecular and Clinical Features of Heterogeneous Vancomycin-Intermediate Staphylococcus aureus in Tertiary Care Hospitals in South India

Objectives: This study aimed to detect heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA) among methicillin-resistant S. aureus (MRSA) isolated from healthcare-associated infections and identify staphylococcal cassette chromosome mec (SCCmec) types. Methods: This study was conducted from February 2019 to March 2020 and included patients admitted in 4 tertiary care hospitals in Karnataka, India. Isolation and identification of MRSA were done using standard bacteriological methods. Antimicrobial susceptibility testing was done using Kirby–Bauer disc diffusion; macrolide-lincosamide-streptogramin B phenotypes were identified using the D test. The minimum inhibitory concentration (MIC) of vancomycin was determined using agar dilution. hVISA were confirmed by the modified population analysis profile-area under the curve test. SCCmec types and the Panton- Valentine leukocidin (pvl) gene were detected using multiplex polymerase chain reaction. Results: Of 220 MRSA stains, 14 (6.4%) were hVISA. None of the MRSA isolates was vancomycin-intermediate or -resistant and all hVISA were susceptible to linezolid and teicoplanin. The macrolide-streptogramin B phenotype was present in 42.9% of hVISA; 92.9% of the hVISA strains had vancomycin MIC in the range of 1–2 μg/mL. Majority of the hVISA and vancomycin-susceptible MRSA were isolated from patients with skin and soft tissue infections. SCCmec III and IV were present in 50% and 35.7% of hVISA, respectively; 14.3% of the hVISA harboured SCCmec V. Conclusion: The prevalence rate of hVISA among MRSA was 6.4%. Therefore, MRSA strains should be tested for hVISA before starting vancomycin treatment. None of the isolates was vancomycin-intermediate or -resistant and all the hVISA strains were susceptible to linezolid and teicoplanin. The majority of the hVISA were isolated from patients with skin and soft tissue infections and harboured SCCmec III and IV. Keywords: MRSA; Hospital Infection; Molecular Typing; Vancomycin; India.

Importance of Toxin Genes and Polymerase Chain Reaction-Based Open Reading Frame Type Analyses for Severe Staphylococcus aureus Infection in Children.

This study analyzed 26 Staphylococcus aureus strains, including 16 methicillin-resistant S. aureus (MRSA) and 10 methicillin-susceptible S. aureus (MSSA), collected from eight medical institutions in the Chiba Prefecture that requested a toxin gene analysis between 2015 and 2021. A total of 14 Panton-Valentine leukocidin (PVL) positive strains were identified, including MSSA. PVL-positive strains were classified into seven types according to polymerase chain reaction-based open reading frame typing (POT); of these types, three POT MRSA strains have not been previously reported, and one has been previously reported as PVL-negative. Some strains tested positive for both PVL and toxic shock syndrome toxin 1. One POT type was identified in both PVL-positive and PVL-negative strains. To the best of our knowledge, this is the first report on the regional spread of highly pathogenic S. aureus strains based on the POT method in children from multiple medical institutions. This method is useful for estimating the spread of toxin gene-carrying strains in the community owing to its association with toxin genes. As the number of PVL-positive strains in Japan increases, it is important to analyze the isolates of severe S. aureus infections in children by combining toxin gene analyses with the POT method.

Clinical and molecular characteristics of methicillin-resistant Staphylococcus aureus in bone and joint infection among children

ObjectiveTo investigate the characteristics of Methicillin-Resistant Staphylococcus aureus (MRSA) in bone and joint infection (BJI) among children.MethodsA total of 338 patients diagnosed with BJI from 2013 to 2022 in Children’s Hospital of Fudan University were enrolled. Demographic information, microbiology culture results and laboratory findings, including white blood counts (WBC), C-reactive protein (CRP), procalcitonin (PCT), interleukin-6 (IL-6), and erythrocyte sedimentation rate (ESR) were collected and analyzed. MRSA was confirmed by antimicrobial susceptibility testing. Other MRSA-caused infections were randomly selected for comparison. Twenty-three virulence and antimicrobial resistance (AMR) genes were screened for MRSA strains. Multilocus sequence typing (MLST) and Staphylococcal protein A (spa) typing were performed using PCR amplification and sequencing.ResultsOf the identified pathogens in BJI, MRSA accounted for 21.0% (47/224). Patients with BJI had high levels of initial CRP, white blood cell count (WBC) and IL-6. ST59 (43.9%) and t437 (37.6%) were the main MRSA subtypes isolated from the children. The major genotypes in BJI were ST59-t437 (29.8%) and ST22-t309 (14.9%), with high carriage of hemolysins including hla (94.4–100%), hlb (66.2–93.3%), and hld (100%). Notably, Panton–Valentine leukocidin (pvl) had a high prevalence (53.3%) in ST22-t309-MRSA. Other virulence genes including tst, seg and sei were more commonly detected in ST22-t309-MRSA (40.0–46.7%) than in ST59-t437-MRSA (4.2–9.9%). High-carriage AMR genes in MRSA included aph(3ʹ)/III (66.7–80%), ermB (57.5–73.3%) and ermC (66.7–78.9%). MRSA presented high-resistance to erythromycin (52.0–100%) and clindamycin (48.0–92.5%), different genotypes displayed variation in their susceptibilities to antibiotics.ConclusionsThe major MRSA genotype in BJI was ST59-t437, followed by ST22-t309, with a higher prevalence of the pvl gene. Continuous surveillance of pvl-positive ST22-t309-MRSA in pediatric BJI infections is thus required.

Genitoanal infections caused by Panton-Valentine leukocidin (PVL)-positive Staphylococcus aureus : Smear infection or sexually transmitted disease?

Panton-Valentine leukocidin (PVL) is apore-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 asmear 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 asexually 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.

Virulence attributes of successful methicillin-resistant Staphylococcus aureus lineages.

Methicillin-resistant Staphylococcus aureus (MRSA) is a leading cause of severe and often fatal infections. MRSA epidemics have occurred in waves, whereby a previously successful lineage has been replaced by a more fit and better adapted lineage. Selection pressures in both hospital and community settings are not uniform across the globe, which has resulted in geographically distinct epidemiology. This review focuses on the mechanisms that trigger the establishment and maintenance of current, dominant MRSA lineages across the globe. While the important role of antibiotic resistance will be mentioned throughout, factors which influence the capacity of S. aureus to colonize and cause disease within a host will be the primary focus of this review. We show that while MRSA possesses a diverse arsenal of toxins including alpha-toxin, the success of a lineage involves more than just producing toxins that damage the host. Success is often attributed to the acquisition or loss of genetic elements involved in colonization and niche adaptation such as the arginine catabolic mobile element, as well as the activity of regulatory systems, and shift metabolism accordingly (e.g., the accessory genome regulator, agr). Understanding exactly how specific MRSA clones cause prolonged epidemics may reveal targets for therapies, whereby both core (e.g., the alpha toxin) and acquired virulence factors (e.g., the Panton-Valentine leukocidin) may be nullified using anti-virulence strategies.

Molecular epidemiology and change trend of methicillin-resistant Staphylococcus aureus from invasive infections of a hospital in Hangzhou from 2012 to 2018.

The disease caused by methicillin-resistant Staphylococcus aureus (MRSA) is a global public health challenge that threatens society and patients seriously. Therefore, the molecular epidemiology and change trend of MRSA is essential for the control and treatment of diseases caused by the pathogen in their regions. To explore molecular epidemiology of MRSA in Hangzhou, we collected 162 MRSA isolates from 2012 to 2018, conducted the antimicrobial susceptibility and used polymerase chain reaction(PCR) to test the molecular typing including multilocus sequence typing (MLST), staphylococcal chromosome cassette mec (SCCmec), staphylococcal protein A (spa A) and Panton-Valentine leucocidin (PVL). All the strains was divided into community-associated MRSA (CA-MRSA) or hospital-associated MRSA (HA-MRSA). 162 MRSA isolates were divided into 16 STs and 30 spa types. The major ST type was ST5 (96/162, 59.3%) and the predominant spa type was t311 (83/162, 51.2%). Five SCCmec types were found and the most common SCCmec type was type II (101/162, 61.7%). ST5-II-t311 was the predominant MRSA clone. And the prevalence of ST5 MRSA gradually declined from 2014 to 2018 but the prevalence of ST59 MRSA significantly increased. At the same time, livestock-associated methicillin-resistant Staphylococcus aureus(LA-MRSA) ST398 and ST9 were detected. Twenty-eight isolates were PVL gene positive (28/162, 17.3%). The most prevalent PVL-positive clone was ST59-IVa-t437. Comparing with HA-MRSA, CA-MRSA had a lower probability of ST5 (9.1% vs 67.1%, P=0.000) but a higher probability of ST59 (63.6% vs 11.4%, P=0.000), not only that, it was more likely to carrying PVL-positive gene (36.4% vs 14.3%, P=0.028). In summary, the molecular types of MRSA were getting complex over time. ST5-II-t311 was the predominant clone of MRSA isolate with a downward incidence from 2014 to 2018. ST59 MRSA strains, which is thought community related strain are spreading into hospitals and has an upward incidence from 2014 to 2018.