Panton-Valentine leukocidin (PVL)-positive health care-associated methicillin-resistant Staphylococcus aureus isolates are associated with skin and soft tissue infections and colonized mainly by infective PVL-encoding bacteriophages

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.

Genomic characterization and outbreak investigations of methicillin-resistant Staphylococcus aureus in a county-level hospital in China

Methicillin-resistant Staphylococcus aureus (MRSA) is a common pathogen contributing to healthcare-associated infections, which can result in multiple sites infections. The epidemiological characteristics of MRSA exhibit variability among distinct regions and healthcare facilities. The aim of this study was to investigate the molecular epidemiology and nosocomial outbreak characteristics of MRSA in a county-level hospital in China. A total of 130 non-repetitive MRSA strains were collected from December 2020 to November 2021. Whole-genome sequencing (WGS) was performed to identify antimicrobial resistance and virulence factors. Phylogenetic analysis was conducted to ascertain genetic diversity and phylogenetic relationships. Independent transmission scenarios were determined by the phylogeny derived from single nucleotide polymorphisms (SNPs) within the core genome. All the MRSA isolates were collected from the intensive care unit (30.00%, 39/130), the department of otorhinolaryngology (10.00%, 13/130) and the department of burn unit (9.23%, 12/130). The clinical samples mainly included phlegm (53.85%, 70/130), purulent fluid (24.62%, 32/130), and secretions (8.46%, 11/130). The resistance rates to erythromycin, clindamycin and ciprofloxacin were 75.38, 40.00, and 39.23%, respectively. All the isolates belonged to 11 clonal complexes (CCs), with the major prevalent types were CC5, CC59, and CC398, accounting for 30.00% (39/130), 29.23% (38/130), and 16.92% (22/130), respectively. Twenty sequence types (STs) were identified, and ST59 (25.38%, 33/130) was the dominant lineage, followed by ST5 (23.84%, 31/130) and ST398 (16.92%, 22/130). Three different SCCmec types were investigated, most of isolates were type IV (33.85%, 44/130), followed by type II (27.69%, 36/130) and type III (0.77%, 1/130). The common clonal structures included CC5-ST5-t2460-SCCmec IIa, CC59-ST59-t437-SCCmec IV and CC398-ST398-t034-SCCmec (-), with rates of 16.92% (22/130), 14.62% (19/130), and 13.84% (18/130), respectively. Only 12 panton-valentine leucocidin (PVL) positive strains were identified. Two independent clonal outbreaks were detected, one consisting of 22 PVL-negative strains belongs to CC5-ST5-t2460-SCCmec IIa and the other consisting of 8 PVL-negative strains belongs to CC5-ST5-t311-SCCmec IIa. Overall, our study indicated that the CC5 lineage emerged as the predominant epidemic clone of MRSA, responsible for nosocomial outbreaks and transmission within a county-level hospital in China, highlighting the necessity to strengthen infection control measures for MRSA in such healthcare facilities.

High prevalence of ST5-SCCmec II-t311 clone of methicillin-resistant Staphylococcus aureus isolated from bloodstream infections in East China

OBJECTIVES

Methicillin-resistant Staphylococcus aureus (MRSA) is a challenging global health threat, resulting in significant morbidity and mortality worldwide. This study aims to determine the molecular characteristics and antimicrobial susceptibility of 263 MRSA isolates in Zhejiang Province, east China.

METHODS

From 2014 to 2019, a total of 263 MRSA isolates from bloodstream infections (BSIs) were collected from 6 hospitals in 4 cities in Zhejiang province, east China. Antimicrobial susceptibility tests were conducted according to the guidelines set forth by the Clinical and Laboratory Standards Institute (CLSI). To characterize and analyze these isolates, multilocus sequence typing (MLST), staphylococcal cassette chromosome mec (SCCmec) typing, staphylococcal protein A (spa) typing and virulence genes gene profiles were performed.

RESULTS

The most predominant clone was ST5-SCCmec II-t311, which accounted for 41.8% (110/263), followed by ST59 (44/263, 16.7%). Compared with non-ST5-II-t311 isolates, ST5-II-t311 isolates were more resistant to erythromycin, tetracycline, levofloxacin, moxifloxacin, and ciprofloxacin, but more susceptible to clindamycin. Moreover, the rates of multidrug resistance were higher in ST5-II-t311 isolates compared to the non-ST5-II-t311 isolates. In comparison to the non-ST5-II-t311 isolates, ST5-II-t311 isolates showed no significant difference in virulence genes detected.

CONCLUSIONS

MRSA ST5-II-t311 clone has become the most predominant clone in Zhejiang Province, east China and has higher rates of multidrug resistance than other isolates, that should be kept in mind when treating BSI. Moreover, MRSA ST59 clone shows an upward trend and has begun to spread into hospitals. Our findings highlight the importance of epidemiological studies of S. aureus carriage in the eastern region.

Whole genome sequencing of methicillin-resistant Staphylococcus aureus clinical isolates from Terengganu, Malaysia, indicates the predominance of the EMRSA-15 (ST22-SCCmec IV) clone

Despite the importance of methicillin-resistant Staphylococcus aureus (MRSA) as a priority nosocomial pathogen, the genome sequences of Malaysian MRSA isolates are currently limited to a small pool of samples. Here, we present the genome sequence analyses of 88 clinical MRSA isolates obtained from the main tertiary hospital in Terengganu, Malaysia in 2016-2020, to obtain in-depth insights into their characteristics. The EMRSA-15 (ST22-SCCmec IV) clone of the clonal complex 22 (CC22) lineage was predominant with a total of 61 (69.3%) isolates. Earlier reports from other Malaysian hospitals indicated the predominance of the ST239 clone, but only two (2.3%) isolates were identified in this study. Two Indian-origin clones, the Bengal Bay clone ST772-SCCmec V (n = 2) and ST672 (n = 10) were also detected, with most of the ST672 isolates obtained in 2020 (n = 7). Two new STs were found, with one isolate each, and were designated ST7879 and ST7883. From the core genome phylogenetic tree, the HSNZ MRSA isolates could be grouped into seven clades. Antimicrobial phenotype-genotype concordance was high (> 95%), indicating the accuracy of WGS in predicting most resistances. Majority of the MRSA isolates were found to harbor more than 10 virulence genes, demonstrating their pathogenic nature.

Investigation into the prevalence of enterotoxin genes and genetic background of Staphylococcus aureus isolates from retain foods in Hangzhou, China

BACKGROUND

Staphylococcus aureus expresses numerous toxins, many of which are strongly believed to be responsible for specific symptoms and even diseases, making it significant in the pathogenesis of human health. Enterotoxins, which are vital toxins, are associated with foodborne illnesses that manifest through symptoms like vomiting and diarrhea. In the present study, 264 S. aureus isolates obtained from various retail foods in Hangzhou, China were further investigated the profiles of enterotoxin genes and genetic backgrounds.

RESULTS

Approximately, 64.02% of the isolates from diverse sources contained at least one Staphylococcal Enterotoxin (SE) genes, displaying a total of 36 distinct combinations. Enterotoxin gene cluster (egc) encoded enterotoxin genes, normally designated by seg, sei, sem, sen, seo and selu, plus with sep were more frequently detected (33.73%, each). In contrast, see, ses and set were absent in any of the isolates tested. A total of 44 sequence types (STs), 20 clonal complexes (CCs) and 66 different staphylococcal protein A (spa) types (including six novel types) were identified among those 169 SE-positive isolates. Moreover, nineteen methicillin-resistant Staphylococcus aureus (MRSA) isolates were identified. The majority of those isolates belonged to the CC59-Sccmec IVa cluster and carried the seb-sek-seq gene cluster. The egc cluster, either coexisting with or without other enterotoxin genes, was observed in all isolates allocated into CC5, CC9, CC20, CC25, CC72 and ST672. Irrespective of the spa types and origins of the food, it appeared that seh was a distinct genetic element present in isolates belonging to the CC1 clonal lineage.

CONCLUSIONS

The results not only proposed a suspected relationship between distribution of enterotoxigenic strains and genetic backgrounds, but also attributed the presence of novel enterotoxins to potential hazards in food safety.

Epidemiology of Staphylococcus aureus Non-Susceptible to Vancomycin in South Asia

Staphylococcus aureus is one of the ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) pathogens among which multidrug resistance has emerged. Resistance to methicillin has resulted in clinicians using the antibiotic of last resort, vancomycin, to treat infections caused by methicillin-resistant S. aureus (MRSA). However, excessive use and misuse of vancomycin are major causes of resistance among S. aureus strains. South Asia encompasses ~25% of the world's population, and countries in South Asia are often characterized as low- and middle-income with poor healthcare infrastructure that may contribute to the emergence of antibiotic resistance. Here, we briefly highlight the mechanism of vancomycin resistance, its emergence in S. aureus, and the molecular epidemiology of non-susceptible S. aureus to vancomycin in the South Asian region.

Prevalence of mecA and Panton-Valentine Leukocidin Genes in Staphylococcus aureus Clinical Isolates from Gaza Strip Hospitals

Methicillin-resistant Staphylococcus aureus (MRSA) are spreading worldwide in hospital and community settings, thus posing a serious public health problem. Panton-Valentine Leukocidin (PVL), an important virulence factor of S. aureus, is a marker of community-acquired MRSA. Here we determined the prevalence of pvl genes among S. aureus isolates from different hospitals in the Gaza Strip, Palestine. A total of 285 S. aureus isolates were collected from five different hospitals in the Gaza Strip. All isolates were characterized for their susceptibility patterns to available antimicrobial agents and by using multiplex PCR for the detection of mecA and pvl genes. The overall prevalence of MRSA in Gaza hospitals was 70.2% (range: 76.3% to 65.5%) and that of pvl among S. aureus isolates was 29.8% (range: 32.9% to 26.2%). The pvl gene was equally prevalent among MRSA isolates (30.5%) and MSSA isolates (28.2%). The most effective antibiotics were rifampicin, vancomycin, and clindamycin, with susceptibility rates of 91.2%, 88.7%, and 84.6%, respectively. The highest percentage of strains were observed to be resistant to penicillin and amoxicillin with clavulanic acid-96.1% and 73.6%, respectively. Our results showed a high prevalence of MRSA and pvl-positive isolates in Gaza Strip hospitals, which likely reflects the situation in the community. It is mandatory to implement systematic surveillance of both hospital and community isolates, together with interventions (such as increased hand hygiene, use of hydroalcoholic solutions, and isolation of carriers) to limit their spread.

Epidemiology and Risk Factors of Community-Associated Bloodstream Infections in Zhejiang Province, China, 2017–2020

Purpose

Community-associated bloodstream infection (CA-BSI) is increasing in many community settings. However, the clinical significance and epidemiology of CA-BSI present in hospital admissions in China are not well established. In this work, we identified the risk factors in outpatients presenting with CA-BSI, and investigate the role of procalcitonin (PCT) and hypersensitive C-reactive protein (CRP) in diagnosing different types of the pathogen in patients with acute CA-BSI.

Methods

A retrospective study enrolling 219 outpatients with CA-BSI from The Zhejiang People's Hospital from January 2017 to December 2020 was performed. Susceptibility of the isolates obtained from these patients was examined. Subjecting receiver operating characteristic curves (ROC) were constructed to analyze the specificity and sensitivity of PCT, CRP, and WBC in determining infections caused by different bacterial genera. Risk factors for CA-BSI in the emergency setting were analyzed using essential information and simple identification of other pathogenic bacterial species through rapidly tested biomarkers.

Results

A total of 219 patients were included in the selection criteria, of which 103 were infected with Gram-positive bacteria (G+) and 116 with Gram-negative bacteria (G-). The PCT was significantly higher in the GN-BSI group than in the GP-BSI group, while no significant difference was observed between the two groups for CRP. Subjecting ROC curves were constructed to analyze WBC, CRP, and PCT, and the area under the curve (AUC) of the PCT in this model was 0.6661, with sensitivity = 0.798 and specificity = 0.489.

Conclusion

The PCT between the GP-BSI group and the GN-BSI group was significantly different. By combining the knowledge of clinicians and the clinical signs of patients, PCT should be utilized as a supplementary approach to initially determine pathogens and direct medication in the early stages of clinical practice.

Molecular analysis of Panton-Valentine Leucocidin (pvl) gene among MRSA and MSSA isolates

The present study was conducted in order to determine the frequency of pvl gene among the pathogenic and healthy population isolates of Methicillin Resistant Staphylococcus aureus (MRSA) and Methicillin Sensitive Staphylococcus aureus (MSSA). For this purpose, nasal swab samples were collected from the healthy individuals (to be used as controls, all the samples were collected irrespective of the sex and age factors), the pathogenic samples were collected from different patients suffering from skin &soft tissue infections caused by S. aureus (to be used as test samples).Both of these population samples were analyzed for the presence of pvl gene. S.aureus were identified through conventional microbiological identification procedures. In the case of normal samples, 70 nasal swabs were collected and only 33 (47%) proved to be S. aureus while 20 pathogenic samples were collected and all (100%) were cleared as S. aureus. For further distribution of samples into MRSA and MSSA, antibiotic susceptibility pattern was checked by using the standard protocols of Kirby-Bauer disc diffusion method. Two antibiotic discs Oxacillin (OX: 1ug) and cefoxitin (FOX: 30ug) were used. Among healthy population, MRSA was found to be 79% (n=26) and MSSA were present as 21% (n= 7). Among pathogenic strains 100% MRSA was detected where n= 20. Detection of pvl gene among the MRSA and MSSA isolates was done by using the uniplex PCR followed by gel electrophoresis. MRSA and MSSA of normal healthy population carried 49% and 7% pvl gene respectively. While, pathogenic MRSA samples carried 46% pvl gene among them. Potentially alarming percentage of pvl gene is present among the normal healthy individuals which indicates a future threat and a major health concern.

An emerging Panton-Valentine leukocidin-positive CC5-meticillin-resistant Staphylococcus aureus-IVc clone recovered from hospital and community settings over a 17-year period from 12 countries investigated by whole-genome sequencing

BACKGROUND

A novel Panton-Valentine leukocidin (PVL)-positive meticillin-resistant Staphylococcus aureus (MRSA) clonal complex (CC)5-MRSA-IVc ('Sri Lankan' clone) was recently described from Sri Lanka. Similar isolates caused a recent Irish hospital outbreak.

AIM

To investigate the international dissemination and diversity of PVL-positive CC5-MRSA-IVc isolates from hospital and community settings using whole-genome sequencing (WGS).

METHODS

Core-genome single nucleotide polymorphism (cgSNP) analysis, core-genome multi-locus sequence typing (cgMLST) and microarray-based detection of antimicrobial-resistance and virulence genes were used to investigate PVL-positive CC5-MRSA-IVc (N = 214 including 46 'Sri Lankan' clone) from hospital and community settings in 12 countries over 17 years. Comparators included 29 PVL-positive and 23 PVL-negative CC5/ST5-MRSA-I/II/IVa/IVc/IVg/V.

RESULTS

Maximum-likelihood cgSNP analysis grouped 209/214 (97.7%) CC5-MRSA-IVc into Clade I; average of 110 cgSNPs between isolates. Clade III contained the five remaining CC5-MRSA-IVc; average of 92 cgSNPs between isolates. Clade II contained seven PVL-positive CC5-MRSA-IVa comparators, whereas the remaining 45 comparators formed an outlier group. Minimum-spanning cgMLST analysis revealed a comparably low average of 57 allelic differences between all CC5/ST5-MRSA-IVc. All 214 CC5/ST5-MRSA-IVc were identified as 'Sri Lankan' clone, predominantly spa type t002 (186/214) with low population diversity and harboured a similar range of virulence genes and variable antimicrobial-resistance genes. All 214 Sri Lankan clone isolates and Clade II comparators harboured a 9616-bp chromosomal PVL-encoding phage remnant, suggesting both arose from a PVL-positive meticillin-susceptible ancestor. Over half of Sri Lankan clone isolates were from infections (142/214), and where detailed metadata were available (168/214), most were community associated (85/168).

CONCLUSIONS

Stable chromosomal retention of pvl may facilitate Sri-Lankan clone dissemination.

Resistome and virulome diversity of foodborne pathogens isolated from artisanal food production chain of animal origin in the Mediterranean region

The aim of the present study was to investigate the resistome and virulome diversity of 43 isolates of Listeria monocytogenes, Salmonella enterica and S. aureus collected from artisanal fermented meat and dairy products and their production environments in Portugal, Spain, Italy and Morocco. After DNA extraction, genomes were sequenced, and de novo assembled. Genetic relationships among genomes were investigated by SNP calling and in silico 7- loci MLST. Genomes of the same species belonged to different ST-types demonstrating the circulation of different clones in in the same artisanal production plant. One specific clone included genomes of S. Paratyphi B belonging to ST43 and repeatedly isolated for more than a year in an artisanal sausage production plant. No genomes but three (belonging to Salmonella enterica), were predicted as multiresistant to different antimicrobials classes. Regarding virulence, genomes of L. monocytogenes belonging to ST1, ST3 and ST489, as well as genomes of S.enterica enterica (ST43, ST33, ST314, ST3667, ST1818, ST198) and ST121 S. aureus were predicted as virulent and hypervirulent. The occurrence of virulent and hypervirulent L. monocytogenes, Salmonella enterica and S. aureus strains in artisanal fermented meat and dairy productions as well as in their finished products suggests the need for a specific focus on prevention and control measures able to reduce the risk of these biological hazards in artisanal food productions.

Methicillin-Resistant Staphylococcus aureus Membrane Vesicles Inhibit the Proliferation and Induce the Apoptosis of Epithelial Cells

Staphylococcus aureus, or methicillin-resistant Staphylococcus aureus (MRSA), is the predominant pathogen in skin and soft tissue infections (SSTIs), and MRSA membrane vesicles (MVs) play a pivotal role in bacterial pathogenesis and the modulation of the host immune response. We aimed to investigate the interaction between MRSA MVs and epithelial cells. In this study, MVs were isolated from an MRSA culture supernatant using the ELD method, comprising an electrophoretic technique used in combination with a 300 kDa cut-off dialysis bag. The proteomic analysis of the MRSA MVs via mass spectrometry showed that shared and distinct proteins exist in the MVs from clinical MRSA isolates with different genetic backgrounds, such as health-care-associated MRSA (HA-MRSA) and community-associated MRSA (CA-MRSA). These MRSA MVs were found to suppress the proliferation and increase the apoptosis of HaCaT cells. We conducted qPCR array, quantitative real-time PCR (qRT-PCR), and Western blotting (WB) analyses, and the results indicated that BCL2 antagonist/killer 1 (Bak1) may be involved in the apoptosis of HaCaT epithelial cells. Our findings suggest that MRSA MVs inhibit the proliferation and induce the apoptosis of epithelial cells.

Antimicrobial Activity of Rhenium Di- and Tricarbonyl Diimine Complexes: Insights on Membrane-Bound S. aureus Protein Binding

Antimicrobial resistance is one of the major human health threats, with significant impacts on the global economy. Antibiotics are becoming increasingly ineffective as drug-resistance spreads, imposing an urgent need for new and innovative antimicrobial agents. Metal complexes are an untapped source of antimicrobial potential. Rhenium complexes, amongst others, are particularly attractive due to their low in vivo toxicity and high antimicrobial activity, but little is known about their targets and mechanism of action. In this study, a series of rhenium di- and tricarbonyl diimine complexes were prepared and evaluated for their antimicrobial potential against eight different microorganisms comprising Gram-negative and -positive bacteria. Our data showed that none of the Re dicarbonyl or neutral tricarbonyl species have either bactericidal or bacteriostatic potential. In order to identify possible targets of the molecules, and thus possibly understand the observed differences in the antimicrobial efficacy of the molecules, we computationally evaluated the binding affinity of active and inactive complexes against structurally characterized membrane-bound S. aureus proteins. The computational analysis indicates two possible major targets for this class of compounds, namely lipoteichoic acids flippase (LtaA) and lipoprotein signal peptidase II (LspA). Our results, consistent with the published in vitro studies, will be useful for the future design of rhenium tricarbonyl diimine-based antibiotics.

Methicillin-resistenter Staphylococcus aureus (MRSA) – eine zentrale Hygiene-Herausforderung in der Dermatologie

Der Methicillin-resistente Staphylococcus aureus ist ein im täglichen Alltag insbesondere für den Bereich der Dermatologie relevanter multiresistenter gram-positiver bakterieller Erreger. Chronische Wunden und atopische Dermatitis sowie der Typ II-Diabetes mellitus spielen hier als Risikofaktoren eine wichtige Rolle. Dieser Übersichtsartikel fokussiert sich neben Ausführungen zu Bedeutung und klinischem Vorkommen auf eine zusammenfassende Darstellung der Hygieneaspekte bei der Behandlung von MRSA-besiedelten oder -infizierten Patienten. Ziel einer solchen Behandlung mit etablierten Hygienekonzepten ist es, eine mögliche Verbreitung des multiresistenten Erregers von einem Patienten auf andere Personen zu verhindern. Werden diese Hygiene-Maßnahmen umgesetzt und gleichzeitig bei einer Infektion eine evidenzbasierte, nach dem Antibiotic-Stewardship ausgerichtete antibiotische Therapie initiiert, sind dies zwei wesentliche Bausteine, um auch weiterhin, wie in den letzten Jahren schon in Nord- und Mitteleuropa beobachtet, rückläufige MRSA-Prävalenzen zu erzielen.

MOLECULAR EPIDEMIOLOGY OF THE TRANSMISSION OF METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS IN KYIV ACUTE CARE HOSPITALS, UKRAINE

OBJECTIVE

The aim: To evaluate the potential of transmission of methicillin-resistance Staphylococcus aureus (MRSA) in Ukrainian acute care hospitals.

PATIENTS AND METHODS

Materials and methods: We performed a multicenter cross-sectional study. Definitions of HAI were used from the CDC/ NHSN. The susceptibility to antibiotics was determined by disk diffusion method according to the EUCAST. The cefoxitin-resistant isolates S.aureus were analyzed for the presence of the mecA gene and femA endogenous control gene using PCR. The virulence factor encoding genes (lukS-PV and lukF-PV) were detected by PCR.

RESULTS

Results: Of 2,421 patients with HAIs caused S.aureus included in the study, 28.7% patients had MRSA. Prevalence of nasal carriage rate of MRSA among healthcare workers (HCWs) was 33.3%. MRSA contamination of hands and uniforms/gowns of HCW were 32.2% and 29.7%, respectively. MRSA contamination in the inanimate environment surfaces in near- and extended patients areas were 26.9%. The predominant MRSA contamination in hospital environment surfaces were: room inner door knob (32.8%), bed rails (28.9%), room light switch (28.9%), chair (27.9%), bedside table handle (20.6%), bedside table (20.5%), and tray table (13.7%). The PVL gene was present in 38.7% of MRSA strains, isolated from patients with HAIs and in 55.7% of MRSA, isolated from environment surfaces in patient area. In addition, the PVL genes were detected in over 56.3% of MRSA isolated from HCWs carrier.

CONCLUSION

Conclusions: The majority of MRSA is acquired during hospitalization. Environmental surfaces may serve as potential reservoirs for nosocomial MRSA and facilitate transmissions via contact.

Combatting AMR: A molecular approach to the discovery of potent and non-toxic rhenium complexes active against C. albicans-MRSA co-infection

Antimicrobial resistance (AMR) is a major emerging threat to public health, causing serious issues in the successful prevention and treatment of persistent diseases. While the problem escalates, lack of financial incentive has lead major pharmaceutical companies to interrupt their antibiotic drug discovery programs. The World Health Organisation (WHO) has called for novel solutions outside the traditional development pathway, with emphasis on new classes of active compounds with non-classical mechanisms of action. Metal complexes are an untapped source of antibiotic potential owing to unique modes of action and a wider range of three-dimensional geometries as compared to purely organic compounds. In this study, we present the antimicrobial and antifungal efficacy of a family of rhenium tricarbonyl diimine complexes with varying ligands, charge and lipophilicity. Our study allowed the identification of potent and non-toxic complexes active in vivo against S. aureus infections at MIC doses as low as 300 ng/mL, as well as against C. albicans-MRSA mixed co-infection. The compounds are capable of suppressing the C. albicans morphogenetic yeast-to-hyphal transition, eradicating fungal-S. aureus co-infection, while showing no sign of cardio-, hepato-, hematotoxiciy or teratogenicity.

The eternal dilemma of antitoxin antibiotics for skin and soft tissue infection

PURPOSE OF REVIEW

In standard clinical practice, combined antibiotic treatment is used to treat severe skin and soft tissue infections (SSTIs), whereby one of the drugs is usually a protein synthesis inhibitor antibiotic. However, evidence for this practice is only based on data from 'in vitro' studies, animal models and case reports. There are no randomized controlled trials. In the light of several new drugs marketed for the treatment of these infections, there is a need to revise the state of the art.

RECENT FINDINGS

New reviews and systematic appraisals of the literature exist on the use of protein synthesis inhibitor antibiotics to treat severe SSTI. Several 'in vitro' studies have assessed the efficacy of some of the new drugs.

SUMMARY

Combination therapy, including an adjuvant protein synthesis inhibitor antibiotic for toxin suppression, should be used both in patients with severe SSTI and in those with moderate infection and risk factors for methicillin-resistant positive- or Panton-Valentine leukocidin positive-Staphylococcus aureus infection.

Comparative study of Staphylococcus aureus from burn patients and healthcare workers in a burn center, Yazd, Iran

Healthcare workers (HCWs) are proposed as the potential source of transmission of Staphylococcus aureus to hospitalized patients, especially in burn units. This study aimed to investigate S. aureus from burn wound infections and those from the nose of HCWs in terms of antibiotic resistance, the presence of Panton-Valentine leucocidin-encoding gene (pvl) and the arginine catabolic mobile element (ACME), and the ability for biofilm formation. Also, the genetic diversity of isolates was assessed using staphylococcal protein A (spa) typing and staphylococcal cassette chromosome mec (SCCmec) typing. Overall, regarding the studied factors, significant differences were found neither between isolates from patients and HCWs nor between methicillin-resistant and methicillin-susceptible isolates (except for multidrug resistance which was significantly higher in MRSA). The most frequent SCCmec types were type I and III. ACME-arcA was only detected in isolates from patients and similarly the presence of ACME-opp3 was the most prevalent in this group. The presence of common clonal complexes among patient isolates and more importantly between isolates from patients and HCWs is warning. The high prevalence of virulence factors, both in MRSA and MSSA, emphasizes the importance of MSSA in burn centers. Finding no significant difference in the presence of virulence-associated factors between isolates from patients and HCWs demonstrates the need to take HCWs into account as important reservoirs.

Temperate Bacteriophages-The Powerful Indirect Modulators of Eukaryotic Cells and Immune Functions

Bacteriophages are natural biological entities that limit the growth and amplification of bacteria. They are important stimulators of evolutionary variability in bacteria, and currently are considered a weapon against antibiotic resistance of bacteria. Nevertheless, apart from their antibacterial activity, phages may act as modulators of mammalian immune responses. In this paper, we focus on temperate phages able to execute the lysogenic development, which may shape animal or human immune response by influencing various processes, including phagocytosis of bacterial invaders and immune modulation of mammalian host cells.

Clonal diversity and spatial dissemination of multi-antibiotics resistant Staphylococcus aureus pathotypes in Southwest Nigeria

Spread of genetically diverse Staphylococcus aureus characterized with multi-antibiotic resistance and regulated by high level agr functionalities in several communities in southwest Nigeria was investigated and evaluated for infection control. Staphylococcus aureus pathotypes recovered from 256 cases including purulent pus from skin infections, soft tissue aspirates, wounds, otorrhea, eye, throat and endocervical infections were assayed for biofilm and antibiogram. Further genotyped with micro-array, mapped for geospatial distribution and evaluated for clonal diversity and functional accessory gene regulators (agr). Significant Staphylococci infection among the ages (OR:0.021, CI:0.545–1.914) and female gender with prevalence rate of MSSA (53.0%) and MRSA (1.5%) (OR:1.021, CI:0.374–1.785) were observed. More than 52.5% resistance rates to tetracycline and amoxicillin with significant median resistance were observed in all the infection cases (p = 0.001). Resistance rate of 78.8% at MIC₅₀ 32μg/ml and MIC₉₀ 128μg/ml to amoxicillin-clavulanate, and more than 40% resistance to ceftazidime, ciprofloxacin and tetracycline of MIC₉₀ and MIC₅₀ at 32 μg/ml were observed. Strains with multi-antibiotic resistance index above 0.83, high beta-lactamase and strong biofilm clustered into separate phylo-group. Heterogeneous t442 (wound and pus), t657 (wound), t091 (ear) and t657 (ear and wound) revealed high phylogenetic diversity. Only 4.6% pvl+ MSSA-CC1 agrI, pvl+ MSSA-CC5 (13.6%) and pvl+ MRSA-CC7 agrII (4.6%), expressed enterotoxin, leukocidins, proteases and resistance gene determinants. Livestock clonal types clustered with identified community-associated strains. Clonal dissemination of resistant pvl+ MSSA-CC1 and MRSA-CC5 encoding agr were predominant in several peri-urban communities where adequate geno-surveillance, population-target antimicrobial stewardship, extensive community structured infection control programs are needed to prevent further focal dissemination.

Antivirulence Strategies for the Treatment of Staphylococcus aureus Infections: A Mini Review

Staphylococcus aureus is a Gram-positive bacterium capable of infecting nearly all host tissues, causing severe morbidity and mortality. Widespread antimicrobial resistance has emerged among S. aureus clinical isolates, which are now the most frequent causes of nosocomial infection among drug-resistant pathogens. S. aureus produces an array of virulence factors that enhance in vivo fitness by liberating nutrients from the host or evading host immune responses. Staphylococcal virulence factors have been identified as viable therapeutic targets for treatment, as they contribute to disease pathogenesis, tissue injury, and treatment failure. Antivirulence strategies, or treatments targeting virulence without direct toxicity to the inciting pathogen, show promise as an adjunctive therapy to traditional antimicrobials. This Mini Review examines recent research on S. aureus antivirulence strategies, with an emphasis on translational studies. While many different virulence factors have been investigated as therapeutic targets, this review focuses on strategies targeting three virulence categories: pore-forming toxins, immune evasion mechanisms, and the S. aureus quorum sensing system. These major areas of S. aureus antivirulence research demonstrate broad principles that may apply to other human pathogens. Finally, challenges of antivirulence research are outlined including the potential for resistance, the need to investigate multiple infection models, and the importance of studying antivirulence in conjunction with traditional antimicrobial treatments.

Constellation of methicillin-resistant genomic islands (SCCmec) among nasal meticillin-resistant Staphylococcus aureus isolates

The apprehensiveness for the knowledge vacuum on existential threat of nasal carriage of pvl+ healthcare-acquired meticillin-resistant Staphylococcus aureus (HA-MRSA) strains amongst subjects in hospitals have led us to pursue a grasp on the constellation of staphylococcal cassette chromosome mec (SCCmec) types and pvl gene among mecA positive MRSA nasal strains. This was accomplished by phenotypic (catalase, coagulase, Microgen staph ID, ORSAB) and genotypic (polymerase chain reaction) biotyping techniques. All the mecA+ strains harboured the SCCmec gene; SCCmec type I prevailed in 43.75% and pvl was found in 42.1% of the isolates. Dual carriage of mecA and pvl genes occurred in six (37.5%, n = 6/16) strains. Overall, majority of the mecA+ MRSA strains documented in this study carried SCCmec elements of the HA genotype with a hint of community-acquired (CA)genotype suggesting a possible coexistence of both HA-MRSA and community-acquiredhealthcare-acquired meticillin-resistant Staphylococcus aureus (CA-MRSA) strains. Consequently, the implementation of methodical surveillance is needed for the evaluation of potential shifts in directionality of (HA-MRSA/CA-MRSA) pvl+ MRSA clones in our hospitals for effective and prudent antimicrobial stewardship.

NASAL CARRIAGE OF MULTI-DRUG RESISTANT PANTON VALENTINE LEUKOCIDIN POSITIVE STAPHYLOCOCCUS AUREUS IN HEALTHY INDIVIDUALS OF TUDUN-WADA, GOMBE STATE, NIGERIA

Background:

Panton-Valentine Leucocidin (PVL)-producing Staphylococcus aureus strains have been implicated in serious community-associated invasive infections and their increasing multidrug resistance is a major global health concern. Thus, we investigated the prevalence of the PVL gene and the antimicrobial resistance profile of nasal S. aureus isolates from healthy adults in Tundu-Wada, Gombe State of Nigeria.

Methods and Materials:

A total of 262 nasal samples from healthy adults were obtained and cultured. The isolates were identified as S. aureus by standard morphological and biochemical methods alongside with the Polymerase Chain Reaction (PCR) amplification of their 16S rRNA gene. Antimicrobial susceptibility testing was performed by the disc diffusion technique and the presence of mecA and PVL genes was determined by PCR analysis.

Results:

The overall nasal colonization of S. aureus was 17.6%. The prevalence of haemolysin and biofilm production among the isolates was 25(54.3%) and 42(91.3%), respectively. Only 2(4.3%) and 5(10.9%) possessed mecA and PVL genes respectively but none of the isolates harboured these two genes. All the isolates were resistant to amoxicillin but were highly susceptible (93.7%) to gentamicin. The prevalence of multi-drug resistance (MDR) among the isolates was M 45.7% and all PVL-producing isolates were MDR while one of the isolates with mecA gene exhibited extensive-drug resistance (XDR).

Conclusion:

This is the first report of nasal colonization of MDR PVL-producing S. aureus in healthy adults in Gombe, Northeastern Nigeria. This study highlights the importance of routine surveillance of healthy populations to provide useful strategies for controlling the spread of virulent multidrug-resistant organisms within the community.

High prevalence of a globally disseminated hypervirulent clone, Staphylococcus aureus CC121, with reduced vancomycin susceptibility in community settings in China

OBJECTIVES

Most vancomycin-intermediate Staphylococcus aureus (VISA) and heterogeneous VISA (hVISA) are derived from hospital-associated MRSA due to treatment failure; however, the prevalence of hVISA/VISA in community settings remains unclear.

METHODS

Four hundred and seventy-six community-associated isolates were collected between 2010 and 2011 during national surveillance for antimicrobial resistance in 31 county hospitals across China. Drug susceptibility evaluation and mecA detection were performed by using broth microdilution and PCR analysis, respectively. hVISA/VISA were identified by using macro-Etest and a modified population analysis profile (PAP)-AUC method. The genetic features of all hVISA/VISA isolates were genotyped.

RESULTS

Among 476 isolates, MRSA and MSSA accounted for 19.7% (n = 94) and 80.3% (n = 382), respectively. Two VISA and 36 hVISA isolates were identified by PAP-AUC testing. The VISA isolates and 29 of the hVISA isolates were MRSA. The proportion of hVISA/VISA was significantly higher in MRSA (30.9%) than in MSSA (1.8%). The hVISA/VISA isolates were assigned to 18 STs classified into seven clonal complexes (CCs). CC121 (n = 12) followed by ST239 (n = 11) was the most prevalent hVISA/VISA clone. All ST239-hVISA/VISA were MRSA, while 12 CC121-hVISA isolates included 6 MSSA and 6 MRSA isolates. SCCmec III was predominant among MRSA-hVISA/VISA isolates. agr I and agr IV were detected in ST239 and CC121, respectively. All except two strains were positive for Panton-Valentine leucocidin genes.

CONCLUSIONS

To the best of our knowledge, this is the first report of CC121 as a prevalent hVISA clone in community settings, highlighting the necessity of surveillance and stricter infection control measures for this globally disseminated lineage.

Design, synthesis and in vivo evaluation of 3-arylcoumarin derivatives of rhenium(I) tricarbonyl complexes as potent antibacterial agents against methicillin-resistant Staphylococcus aureus (MRSA)

We have prepared a series of ten 3-arylcoumarin molecules, their respective fac-[Re(CO)₃(bpy)L]⁺ and fac-[Re(CO)₃(L⁀L)Br] complexes and tested all compounds for their antimicrobial efficacy. Whereas the 3-arylcoumarin ligands are virtually inactive against the human-associated pathogens with minimum inhibitory concentrations (MICs) > 150 μM, when coordinated to the fac-[Re(CO)₃]⁺ core, most of the resulting complexes showed remarkable antibacterial potency. Several rhenium complexes exhibit activity in nanomolar concentrations against Gram-positive pathogens such as Staphylococcus aureus strains, including methicillin-resistant S. aureus (MRSA) and Enterococcus faecium. The molecules do not affect bacterial cell membrane potential, but some of the most potent complexes strongly interact with DNA, indicating it as a possible target for their mode of action. In vivo studies in the zebrafish model showed that the complexes with anti-staphylococcal/MRSA activity were non-toxic to the organism even at much higher doses of the corresponding MICs. In the zebrafish-MRSA infection model, the complexes increased the survival rate of infected fish up to 100% and markedly reduced bacterial burden. Moreover, all rescued fish developed normally following the treatments with the metallic compounds.

Characterisation of antibiotic resistance, virulence, clonality and mortality in MRSA and MSSA bloodstream infections at a tertiary-level hospital in Hungary: a 6-year retrospective study

BACKGROUND

Staphylococcus aureus bloodstream infections (BSI) cause significant morbidity and mortality due to the frequent antibiotic resistance, toxin and adhesin production of the bacterium. These characteristics differ significantly in methicillin resistant (MRSA) and methicillin sensitive S. aureus (MSSA) and also among isolates of different MRSA clones, contributing to the outcome of S. aureus bacteraemia.

METHODS

In this study, all MRSA BSI isolates from Semmelweis University, Budapest, Hungary, isolated between 2011-2016 and the same number of matched MSSA (overall 306 isolates) were characterised in terms of antibiotic susceptibility, virulence genes, clonality and their association with all-cause 30-day mortality. Effect of patient related variables, such as age, gender and comorbidities were also investigated.

RESULTS

ST22-MRSA-IV and ST5-MRSA-II were the most prevalent clones in our study. SCCmec I isolates showed the highest resistance rates and SCCmec II carried most virulence genes. Infections caused by SCCmec IV isolates were associated with the highest mortality rate (42.2%), despite the similar comorbidity rates of the different patient groups. All-cause 30-day mortality was 39.9% in the MRSA and 30.7% in the MSSA group. Increased teicoplanin MIC was associated with high mortality rate. Resistance to ciprofloxacin, erythromycin and clindamycin was common in MRSA, whereas MSSA isolates were more sensitive to all antibiotics with the exception of doxycycline. All MRSA isolates were sensitive to glycopeptides and linezolid; resistance to rifampicin and sulfamethoxazole-trimethoprim was low. MRSA isolates carried more adhesion genes, superantigens were more frequent in MSSA. Panton-Valentine leukocidin was found in 2.3% of the isolates.

CONCLUSION

This study provides insight into the clonal composition and associated mortality of BSI S. aureus isolates in Hungary. The results suggest that the outcome of the infection is determined by the antibiotic resistance, genotype of the bacterium, and patient-related factors; rather than the virulence factors carried by the bacteria.

Skin and Soft Tissue Infections Caused by Different Genotypes of PVL-Positive Community-Acquired Methicillin-Resistant Staphylococcus aureus Strains

Panton-Valentine leukocidin (PVL) is a causative agent of lethal necrotizing pneumonia and is associated with epidemic strains of community-acquired (CA) methicillin-resistant Staphylococcus aureus (MRSA). PVL-producing strains have rarely been isolated in Japan. However, PVL-positive CA-MRSA has been isolated much more frequently in recent years. To investigate the relevance of pvl genes (lukS/F-PV) and clinical traits in epidemic S. aureus strains, we genotyped four PVL-positive CA-MRSA strains isolated from patients with skin and soft tissue infections and measured their susceptibility to antibiotics. Three of the isolates matched the genotype of the USA300 clone, which has predominantly been isolated in the USA. The remaining strain matched the ST217 genotype, and its spa type was identical to that of PVL-positive strains previously reported in India and China. Abscess drainage was necessary in all cases, and deep cutaneous ulcers were formed in three out of four cases regardless of the genotype. The ST217 genotype strain was resistant to clindamycin, in addition to quinolones, macrolides, and aminoglycosides. Thus, diagnostic determination of lukS/F-PV should be used as a guide for selecting the treatment regimen.

Bacteriophages: Uncharacterized and Dynamic Regulators of the Immune System

The human gut is an extremely active immunological site interfacing with the densest microbial community known to colonize the human body, the gut microbiota. Despite tremendous advances in our comprehension of how the gut microbiota is involved in human health and interacts with the mammalian immune system, most studies are incomplete as they typically do not consider bacteriophages. These bacterial viruses are estimated to be as numerous as their bacterial hosts, with tremendous and mostly uncharacterized genetic diversity. In addition, bacteriophages are not passive members of the gut microbiota, as highlighted by the recent evidence for their active involvement in human health. Yet, how bacteriophages interact with their bacterial hosts and the immune system in the human gut remains poorly described. Here, we aim to fill this gap by providing an overview of bacteriophage communities in the gut during human development, detailing recent findings for their bacterial-mediated effects on the immune response and summarizing the latest evidence for direct interactions between them and the immune system. The dramatic increase in antibiotic-resistant bacterial pathogens has spurred a renewed interest in using bacteriophages for therapy, despite the many unknowns about bacteriophages in the human body. Going forward, more studies encompassing the communities of bacteria, bacteriophages, and the immune system in diverse health and disease settings will provide invaluable insight into this dynamic trio essential for human health.

Molecular typing revealed the emergence of pvl-positive sequence type 22 methicillin-susceptible Staphylococcus aureus in Urumqi, Northwestern China

Background

Staphylococcus aureus is among the most common causes of health care- and community-associated infections worldwide. The distributions of different S. aureus clones change over time and also vary geographically. The purpose of this study was to determine the molecular type and antimicrobial resistance profiles of clinical S. aureus strains isolated in Urumqi, Northwestern China.

Methods

A total of 605 clinical S. aureus isolates were collected from Xinjiang Military General Hospital, in Urumqi. Protein A-encoding (spa) typing, multilocus sequence typing, staphylococcal chromosomal cassette mec typing, Panton-Valentine leucocidin (pvl) gene detection, and antimicrobial resistance profiling were performed.

Results

Among these strains, 271 isolates (44.7%) were methicillin-resistant S. aureus (MRSA) and 334 (55.3%) were methicillin-susceptible S. aureus (MSSA). The MRSA strains consisted of 22 spa types and 14 sequence types (STs). ST239-MRSA-III-t030 (73.1%, 198/271) and ST59-MRSA-IV-t437 (11.8%, 32/271) were the most common, and ST22-MRSA-IV-t309 was the rarest (2.02%, 6/271). The MSSA strains consisted of 93 spa types and 29 STs. ST22, ST121, ST398, ST5, ST7, ST188, and ST15 were the main MSSA STs, and ST22-MSSA-t309 was most common (26.0%, 87/334). The pvl gene was present in 20.3% of all S.aureus strains, and 80.8% (88/99) of ST22-MSSA strains harbored the pvl gene. A total of 85.7% pvl-positive ST22-MSSA strains were spa t309 (85/99), and 87.5% of pvl-positive ST22-MSSA strains were from abscesses or wounds (skin and soft tissue infections). All ST239-MRSA strains were resistant to gentamicin (GEN), levofloxacin (LEV), ciprofloxacin (CIP), moxifloxacin (MXF), rifampicin (RIF), and tetracycline (TET). Among the ST59-MRSA strains, over 70.0% were resistant to erythromycin (ERY), clindamycin (CLI), and TET. ST22-MSSA remained susceptible to most antibiotics, but was resistant to PEN (97.0%), ERY (57.6%), and CLI (15.2%).

Conclusion

Our major results indicated that the antimicrobial resistance profiles and pvl genes of S. aureus isolates from Urumqi were closely associated with clonal lineage. ST239-MRSA-III-t030 and pvl-positive ST22-MSSA-t309 were the most common clones in this region of Northwestern China.

CA-MRSA and HA-MRSA coexist in community and hospital settings in Uganda

Background

Methicillin resistant Staphylococcus aureus (MRSA) strains were once confined to hospitals however, in the last 20 years MRSA infections have emerged in the community in people with no prior exposure to hospitals. Strains causing such infections were novel and referred to as community-associated MRSA (CA-MRSA). The aim of this study was to determine the MRSA carriage rate in children in eastern Uganda, and to investigate coexistence between CA-MRSA and hospital-associated (HA-MRSA).

Methods

Between February and October 2011, nasopharyngeal samples (one per child) from 742 healthy children under 5 years in rural eastern Uganda were processed for isolation of MRSA, which was identified based on inhibition zone diameter of ≤19 mm on 30 μg cefoxitin disk. SCCmec and spa typing were performed for MRSA isolates.

Results

A total of 140 S. aureus isolates (18.9%, 140/742) were recovered from the children of which 5.7% (42/742) were MRSA. Almost all (95.2%, 40/42) MRSA isolates were multidrug resistant (MDR). The most prevalent SCCmec elements were types IV (40.5%, 17/42) and I (38.1%, 16/42). The overall frequency of SCCmec types IV and V combined, hence CA-MRSA, was 50% (21/42). Likewise, the overall frequency of SCCmec types I, II and III combined, hence HA-MRSA, was 50% (21/42). Spa types t002, t037, t064, t4353 and t12939 were detected and the most frequent were t064 (19%, 8/42) and t037 (12%, 5/42).

Conclusion

The MRSA carriage rate in children in eastern Uganda is high (5.7%) and comparable to estimates for Mulago Hospital in Kampala city. Importantly, HA-MRSA (mainly of spa type t037) and CA-MRSA (mainly of spa type t064) coexist in children in the community in eastern Uganda, and due to high proportion of MDR detected, outpatient treatment of MRSA infection in eastern Uganda might be difficult.

Virulence Determinants Are Required for Brain Abscess Formation Through Staphylococcus aureus Infection and Are Potential Targets of Antivirulence Factor Therapy

Bacterial brain abscesses (BAs) are difficult to treat with conventional antibiotics. Thus, the development of alternative therapeutic strategies for BAs is of high priority. Identifying the virulence determinants that contribute to BA formation induced by Staphylococcus aureus would improve the effectiveness of interventions for this disease. In this study, RT-qPCR was performed to compare the expression levels of 42 putative virulence determinants of S. aureus strains Newman and XQ during murine BA formation, ear colonization, and bacteremia. The alterations in the expression levels of 23 genes were further confirmed through specific TaqMan RT-qPCR. Eleven S. aureus genes that persistently upregulated expression levels during BA infection were identified, and their functions in BA formation were confirmed through isogenic mutant experiments. Bacterial loads and BA volumes in mice infected with isdA, isdC, lgt, hla, or spa deletion mutants and the hla/spa double mutant strain were lower than those in mice infected with the wild-type Newman strain. The therapeutic application of monoclonal antibodies against Hla and SpA decreased bacterial loads and BA volume in mice infected with Newman. This study provides insights into the virulence determinants that contribute to staphylococcal BA formation and a paradigm for antivirulence factor therapy against S. aureus infections.

A Distinct Geographic Variant of sasX in Methicillin-Resistant Staphylococcus aureus ST239 and ST368 Lineage from South India

Staphylococcal surface protein sasX is a colonization mediating virulence factor in ST239 methicillin-resistant Staphylococcus aureus (MRSA) strains, which potentially contribute to its successful establishment. We aimed to study the presence and dissemination of sasX in clinical MRSA isolates and among MRSA carriers. A total of 450 nonduplicate clinical MRSA isolates recovered from blood cultures between 2013 and 2017 were included in this study. In addition, 93 nasal swabs were collected from patients receiving hemodialysis, after obtaining consent and screening for MRSA colonization. sasX polymerase chain reaction and sequencing were carried out for all isolates. Multilocus sequence typing was performed for all sasX-positive isolates. Of the tested clinical MRSA isolates, 11% (n = 48) were positive for sasX gene. Among hemodialysis patients, 26% (n = 24) were characterized as MRSA carriers. However, all MRSA strains isolated from nasal swab were negative for sasX gene. Overall, we observed 10% (11% in clinical MRSA isolates and 0% in MRSA carriers) of sasX-positive MRSA in this study. ST239 and ST368 were the predominant sasX carrying MRSA lineages. The majority of sasX carrying MRSA strains were characterized as Staphylococcus epidermidis surface protein I (sesI; 71%), a sasX homolog native to S. epidermidis. This study highlights the dissemination of sasX/sesI to ST368 (CC8), ST3324 (CC8), ST772 (CC1), and ST22 (CC22). The presence of S. epidermidis-specific invasive factor sesI in clinical MRSA strains provides evidence for horizontal transfer between these closely related species.

Predominance of methicillin-resistant Staphylococcus aureus in the residents and environments of long-term care facilities in Taiwan

BACKGROUND/PURPOSE

This study investigated the distribution and persistence of multidrug resistant organisms (MDROs) including methicillin-resistant Staphylococcus aureus (MRSA), carbapenem-resistant Enterobacteriaceae (CRE), carbapenem-resistant Pseudomonas aeruginosa (CRPA), and multidrug-resistant Acinetobacter baumannii (MDRAB) in six long-term care facilities (LTCFs).

METHODS

We investigated the distribution of MDROs in residents of six LTCFs and their environments from January to December 2016 (intervention period). Active surveillance of colonization of MDROs was performed by culturing rectal and nasal swab samples from the residents every three months. Multilocus sequence typing (MLST) was conducted, and genes for panton-valentine leukocidin (PVL) from MRSA isolates were determined.

RESULTS

A total of 521 samples were positive for MDROs, and MRSA was the most common organism (65.1%), followed by MDRAB (11.3%), carbapenem-resistant Klebsiella pneumoniae (11.1%), carbapenem-resistant Escherichia coli (4.6%), and carbapenem-resistant P. aeruginosa (2.1%, n = 11). By a linear regression model, positive MRSA isolates from the environment were found to be statistically significant and associated with the number of colonized LTCF residents (p = 0.01), while the timing of the surveillance culture was not (p = 0.227). The main MLST types associated with PVL-production were sequence type (ST) 59, (40.0%, 24/60), ST30 (21.4%, 3/14), ST8 (87.5%, 14/16), and ST45 (3.6%, 1/28). The susceptibility rates of tetracycline (96.7%), trimethoprim-sulfamethoxazole (96.7%), and ciprofloxacin (81.7%) were statistically significant and higher in MRSA ST59, compared to the rates in MRSA ST45 isolates.

CONCLUSIONS

MRSA was the most commonly colonized MDRO, both in the LTCF residents and in the environment, followed by MDRAB and carbapenem-resistant K. pneumoniae.

Antibiotic Based Phenotype and Hospital Admission Profile are the Most Likely Predictors of Genotyping Classification of MRSA

Background:

Methicillin-resistant Staphylococcus aureus (MRSA) infection is associated with increased morbidity, mortality, and financial burdens. Phenotyping methods are used to classify MRSA as either health care MRSA (HA-MRSA) or community-associated MRSA (CA-MRSA). Recent studies suggested the phenotyping methods are not always reliable, based on a lack of concordance with genotyping results.

Objective:

In this study, concordance of classification methods based on clinical characteristics or antibiotic susceptibility compared to the gold standard genotyping was assessed in the classification of MRSA.

Methods:

We compared the genotypes and phenotypes of MRSA in 133 samples taken from patients in Saudi Arabia. Statistical analyses included concordance, specificity and sensitivity, and logistic regression modeling.

Results:

There was fair a definite agreement between the health care risk and infection type methods (p < .001), but no statistically significant agreement between the susceptibility pattern and health care risk methods (p = 243), and between susceptibility pattern and infection type methods (p = .919). Reduced multiple regression modelling suggested the potential of a phenotyping-based method of antibiotic susceptibility pattern (OR = 15.47, p < .001) in conjunction with hospital admission profile(OR = 2.87, p = .008) to accurately identify MRSA as HA-MRSA and CA-MRSA.

Conclusion:

The use of a standardized phenotyping technique, using susceptibility pattern and hospital admission profiles to classify MRSA infections as either HA-MRSA or CA-MRSA, would facilitate diagnosis, infection control efforts, prevention, and assignment of appropriate therapies. The ability to use phenotyping in the classification of these strains would improve efforts to contend with this adept and evolving bacterial organism.

Molecular characterization of Panton-Valentine leukocidin (PVL) toxin-encoding phages from South India

A total of 19 methicillin-resistant Staphylococcus aureus (MRSA) isolates were investigated for Panton-Valentine leukocidin (PVL) toxin, PVL gene sequence variation and PVL-encoding phages. Whole genome sequencing was performed for all isolates. Analysis of MRSA isolates (n = 19) confirmed that most MRSA (n = 11) were positive for the PVL gene and were multidrug resistant. ST772-MRSA-V was the predominant PVL-positive MRSA clone, although all of them were found to carry the ΦIND772PVL phage in the genome. This study provides insights into the evolution of a new lineage of PVL-MRSA and highlights the potential risk of the emergence of multidrug-resistant community-acquired MRSA with high virulence.

Diagnosis and management of Panton-Valentine leukocidin toxin associated Staphylococcus aureus infection: an update

The incidence of invasive Staphylococcus aureus (SA) infection has increased in the past decade and is associated with poor outcomes and high mortality rates. Of all the virulence factors, Panton-Valentine Leukocidin (PVL) has received the greatest attention. PVL producing SA strains are more likely to produce severe skin and soft tissue infections (SSTIs) and necrotizing pneumonia. This review focuses on the current evidence on PVL-SA virulence, epidemiology, clinical disease and treatment with relevance to healthcare in India.

Molecular characterisation of methicillin-resistant Staphylococcus aureus (MRSA) isolated at a large referral hospital in Zambia

INTRODUCTION

Methicillin-resistant Staphylococcus aureus (MRSA) is globally recognized as an important public health problem. Whereas comprehensive molecular typing data of MRSA strains is available, particularly in Europe, North America and Australia, similar information is very limited in sub-Saharan Africa including Zambia.

METHODS

In this study, thirty two clinical isolates of Staphylococcus aureus, collected at a large referral hospital in Lusaka, Zambia between June 2009 and December 2012 were analysed by Staphylococcal cassette chromosome mec (SCCmec), Staphylococcus protein A gene typing (spa) and detection of the Panton-Valentine Leukocidin genes (pvl).

RESULTS

Three SCCmec types were identified namely SCCmec type IV (65.6%), SCCmec type III (21.9%), SCCmec type I (3.1%). Nine point four percent (9.4%) of the isolates were untypable. Five spa types, which included a novel type, were detected and the most prevalent spa type was t064 (40.6%). Other spa types included spa types t2104 (31.3%), t355 (3.1%) and t1257 (21.9%). The pvl genes were detected in 3 out of 32 isolates.

CONCLUSION

These molecular typing data indicated that the MRSA strains collected in Lusaka were diverse. Although the source of these MRSA was not established, these results stress the need for assessing infection prevention and control procedures at this health-care facility in order to curtail possible nosocomial infections. Furthermore, country-wide surveillance of MRSA in both the community and health-care facilities is recommended for infection prevention and control. To our knowledge, this represents the first study to characterise MRSA using molecular tools in Zambia.

Molecular and Phenotypic Characterization Revealed High Prevalence of Multidrug-Resistant Methicillin-Susceptible Staphylococcus aureus in Chongqing, Southwestern China

Methicillin-susceptible Staphylococcus aureus (MSSA) accounts for ∼40% of staphylococcal infections in China. However, the molecular characterization of MSSA is not well described. In this study, 124 MSSA strains collected in 2013 from a comprehensive teaching hospital in Chongqing, Southwestern China, were subjected to antibiotics susceptibility testing and molecular typing, including multilocus sequence typing, staphylococcal protein A (spa) gene typing, accessory gene regulator (agr) typing, pulsed-field gel electrophoresis (PFGE) typing, Panton-Valentine leukocidin (pvl) gene detection, and antibiotic-resistant gene detection. MSSA strains exhibited high genetic heterogeneity. A total of 10 PFGE groups, 26 sequence types, and 47 spa types were identified. Type I (62.9%) was the most frequent agr type, followed by type II (15.3%), type IV (11.3%), and type III (10.5%). The prevalence of pvl genes was 27.4% (34/124). Notably, 44.4% (55/124) of MSSA strains were multidrug resistance (MDR), and MDR isolates were mostly resistant to penicillin, erythromycin, and clindamycin. The resistance gene blaZ was present in 84.7% of strains, ermC was present in 85.5% of strains, ermA was present in 28.2% of strains, tetK was present in 16.1% of strains, tetM was present in 6.5% of strains, and aacA-aphD was present in 2.6% of strains. These data demonstrated the high prevalence of MDR MSSA in Chongqing, thereby indicating the need to control MSSA infection.

Typing of Panton-Valentine Leukocidin-Encoding Phages and lukSF-PV Gene Sequence Variation in Staphylococcus aureus from China

Panton-Valentine leukocidin (PVL, encoded by lukSF-PV genes), a bi-component and pore-forming toxin, is carried by different staphylococcal bacteriophages. The prevalence of PVL in Staphylococcus aureus has been reported around the globe. However, the data on PVL-encoding phage types, lukSF-PV gene variation and chromosomal phage insertion sites for PVL-positive S. aureus are limited, especially in China. In order to obtain a more complete understanding of the molecular epidemiology of PVL-positive S. aureus, an integrated and modified PCR-based scheme was applied to detect the PVL-encoding phage types. Phage insertion locus and the lukSF-PV variant were determined by PCR and sequencing. Meanwhile, the genetic background was characterized by staphylococcal cassette chromosome mec (SCCmec) typing, staphylococcal protein A (spa) gene polymorphisms typing, pulsed-field gel electrophoresis (PFGE) typing, accessory gene regulator (agr) locus typing and multilocus sequence typing (MLST). Seventy eight (78/1175, 6.6%) isolates possessed the lukSF-PV genes and 59.0% (46/78) of PVL-positive strains belonged to CC59 lineage. Eight known different PVL-encoding phage types were detected, and Φ7247PVL/ΦST5967PVL (n = 13) and ΦPVL (n = 12) were the most prevalent among them. While 25 (25/78, 32.1%) isolates, belonging to ST30, and ST59 clones, were unable to be typed by the modified PCR-based scheme. Single nucleotide polymorphisms (SNPs) were identified at five locations in the lukSF-PV genes, two of which were non-synonymous. Maximum-likelihood tree analysis of attachment sites sequences detected six SNP profiles for attR and eight for attL, respectively. In conclusion, the PVL-positive S. aureus mainly harbored Φ7247PVL/ΦST5967PVL and ΦPVL in the regions studied. lukSF-PV gene sequences, PVL-encoding phages, and phage insertion locus generally varied with lineages. Moreover, PVL-positive clones that have emerged worldwide likely carry distinct phages.

First report of Panton-Valentine leukocidin-positive methicillin-susceptible Staphylococcus aureus ST88 harbouring ΦSa2usa isolated from refractory breast abscesses in Japan

A methicillin-susceptible Staphylococcus aureus with Panton–Valentine leukocidin (PVL) genes was isolated from refractory breast abscesses of 12-year-old girl in Japan, and classified into ST88, spa-t1245 and coa-IIIa. This strain harboured PVL phage ΦSa2usa, which is usually found in ST8 community-acquired methicillin-resistant S. aureus clone USA300.

Staphylococcus aureus ST121: a globally disseminated hypervirulent clone

Staphylococcus aureus is a leading cause of bacterial infections in hospitals and communities worldwide. With the development of typing methods, several pandemic clones have been well characterized, including the extensively spreading hospital-associated meticillin-resistant S. aureus (HA-MRSA) clone ST239 and the emerging hypervirulent community-associated (CA) MRSA clone USA300. The multilocus sequence typing method was set up based on seven housekeeping genes; S. aureus groups were defined by the sharing of alleles at ≥ 5 of the seven loci. In many cases, the predicted founder of a group would also be the most prevalent ST within the group. As a predicted founder of major S. aureus groups, approximately 90 % of ST121 strains was meticillin-susceptible S. aureus (MSSA). The majority of ST121 strains carry accessory gene regulator type IV, whereas staphylococcal protein A gene types for ST121 are exceptionally diverse. More than 90 % of S. aureus ST121 strains have Panton-Valentine leukocidin; other enterotoxins, haemolysins, leukocidins and exfoliative toxins also contribute to the high virulence of ST121 strains. Patients suffering from S. aureus ST121 infections often need longer hospitalization and prolonged antimicrobial therapy. In this review, we tried to summarize the epidemiology of the S. aureus clone ST121 and focused on the molecular types, toxin carriage and disease spectrum of this globally disseminated clone.