Changing epidemiology of community-associated methicillin-resistant Staphylococcus aureus in the Asia-Pacific region

Methicillin resistant Staphylococcus aureus in the United Arab Emirates: a 12-year retrospective analysis of evolving trends

Introduction

Methicillin resistant Staphylococcus aureus (MRSA) is a major contributor to the global burden of antimicrobial resistance (AMR). As MRSA continues to evolve, the need for continued surveillance to evaluate trends remains crucial. This study was carried out to assess MRSA trends in the United Arab Emirates (UAE) based on analysis of data from the national AMR surveillance program.

Methods

We carried out a 12-year (2010-2021) retrospective analysis of MRSA demographic and microbiological data collected as part of the UAE national AMR surveillance program. Participating centers from across the country routinely submit AMR surveillance data collected by trained personnel to the National AMR Surveillance Committee, where data is analyzed using a unified WHONET platform. Data on non-duplicate isolates associated with clinical infections were obtained and included in the analysis.

Results

A total of 29,414 non-duplicate MRSA isolates associated with clinical infections were reported between 2010 and 2021 (2010: n = 259; 2021: n = 4,996). MRSA represented 26.4% of all S. aureus (n = 111,623) isolates identified during the study period. In 2010, among the S. aureus isolates with reported oxacillin testing, 21.9% (n/N = 259/1,181) were identified as MRSA and this showed an increase to 33.5% (n/N = 4,996/14,925) in 2021. Although there was variation in the distribution of MRSA across the seven emirates of the country, most had an upward trend. Patient demographics reflected a male preponderance, with most being adults and from the outpatient setting. Isolates were mostly from skin and soft tissue infection specimens (72.5%; n/N = 21,335/29,414). Among the inpatients (N = 8,282), a total of 3,313 MRSA isolates were from specimens obtained ≤ 48 h after admission indicative of community acquired infection. Increasing resistance trends were observed for most antibiotics including ciprofloxacin, levofloxacin, moxifloxacin, erythromycin, gentamicin, trimethoprim-sulfamethoxazole, and quinupristin/dalfopristin. Low levels of resistance (0.0-0.8%) were sustained for linezolid except for 2015, 2016, and 2017 with 2.5, 2.6, and 2.9%, respectively. No confirmed vancomycin resistance was reported.

Conclusion

The increasing trend of MRSA isolates associated with clinical infections in the hospital and community settings is a concern. Continued monitoring including incorporation of genomic surveillance and infection control measures are recommended to stem the dissemination.

Prevalence, drug resistance, molecular typing and comparative genomics analysis of MRSA strains from a tertiary A hospital in Shanxi Province, China

Staphylococcus aureus (S. aureus) is an important zoonotic pathogen that causes a high incidence rate and mortality worldwide. This study investigated the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) strains in a tertiary A hospital in Shanxi Province, China, in order to determine the major epidemic clones as well as their antibiotic resistance and virulence characteristics. A total of 212 S. aureus strains were collected in this hospital, and were subjected to antimicrobial susceptibility testing, detection of virulence genes, resistance genes, and efflux pump genes. Among them, 38 MRSA strains were further subjected to detection of biofilm genes, assessment of biofilm formation ability, MLST, spa typing, SCCmec typing, and phylogenetic analysis. The majority of S. aureus strains came from the neonatology department, with secretions and purulent fluid being the main source of samples. The strains showed high resistance to penicillin (98.11%), erythromycin (64.62%) and clindamycin (59.91%), while being sensitive to vancomycin and linezolid. The detection rates of efflux pump genes and resistance genes were high, and there was a significant correlation between resistance gene types and phenotypes, with mecA showing a close correlation with oxacillin. The detection rates of virulence genes and the toxin gene profiles of MSSA and MRSA strains showed significant differences. And the detection rate of biofilm genes in MRSA strains was relatively high, with 13.16% of MRSA strains showing strong biofilm formation ability. The most common epidemic clone of MRSA was ST59-SCCmecIV-t437, followed by ST59-SCCmecV-t437. The former had a higher detection rate of resistance genes and a stronger biofilm formation ability, while the latter had a higher positive rate for pvl gene and stronger pathogenicity, making it more likely to cause systemic infections. Phylogenetic analysis showed that all MRSA strains in this study clustered into three major branches, with distinct differences in antibiotic resistance and virulence characteristics among the branches. ST59-MRSA strains from different species showed consistency and inter-species transmission, but there were differences among ST59-MRSA strains from different geographical locations. In general, most MSSA and MRSA strains exhibited multidrug resistance and carried multiple resistance genes, virulence genes, and biofilm formation genes, warranting further research to elucidate the mechanisms of drug resistance and pathogenesis.

Comparing the Phylogenetic Distribution of Multilocus Sequence Typing, Staphylococcal Protein A, and Staphylococcal Cassette Chromosome Mec Types in Methicillin-Resistant Staphylococcus Aureus (MRSA) in Korea from 1994 to 2020

Staphylococcus aureus (S. aureus) bacteremia is one of the most frequent and severe bacterial infections worldwide. Methicillin-resistant Staphylococcus aureus (MRSA) is a serious human pathogen that can cause a wide variety of infections. Comparative genetic analyses have shown that despite the existence of a vast number of genotypes, genotypes are restricted to certain geographical locations. By comparing multilocus sequence typing (MLST) and SCCmec types from 1994 to 2020, the present study intended to discover which genotype genes were related to MRSA infections. MLST, Staphylococcus aureus protein A (spa), and SCCmec typings were performed to determine their relationship during those years. Results revealed that MRSA isolates in the Republic of Korea were distributed among all major staphylococcal cassette chromosome mec (SCCmec) types. The majority of SCCmec isolates belonged to SCCmec type II and type IV. The majority of MLST had the sequence type (ST) 72, 239, 8, or 188. By contrast, minorities belonged to ST22 (SCCmec IV), ST772 (SCCmec V), and ST672 (SCCmec V) genotypes. The SCCmec type was determined for various types. The spa type was dispersed, seemingly regardless of its multidrug resistance property. The MLST type was found to be similar to the existing typical type. These results showed some correlations between resistance characteristics and types according to the characteristics of the MLST types distributed, compared to previous papers. Reports on genotype distribution of MLST and SCCmec types in MRSA are rare. These results show a clear distribution of MLST and SCCmec types of MRSA from 1994 to 2020 in the Republic of Korea.

An insight into whole genome sequencing data of methicillin-resistant Staphylococcus aureus circulating in a teaching hospital in North India

PURPOSE

To provide an insight into the Whole-genome sequencing (WGS) data of MRSA strains circulating in a teaching hospital in north India.

METHODS

An exploratory study was conducted in which fifty non-repetitive MRSA isolates obtained from pus samples of inpatients from July 2018 to February 2019 were subjected to preliminary identification (ID) and antibiotic susceptibility testing (AST) at our centre. These isolates were later sent to Central Research Laboratory, India for further testing using the VITEK-2 compact system followed by WGS. Only eighteen isolates were eventually considered for final analysis and the rest (n ​= ​32) were excluded due to various technical reasons.

RESULTS

The WGS confirmed MRSA isolates predominantly belonged to CC22 (56.25%) and CC30 (31.25%). The CC22 MRSA strains carried SCCmec types IVa (77.8%) & IVc (22.2%) and belonged to spa types t005 (44.4%), t4584 (22.2%), t11808 (11.1%), t1328 (11.1%) and t309 (11.1%), respectively. The MRSA isolates of CC30 carried SCCmec types IVa (60%), IVg (20%) & V (20%) and belonged to spa types t021 (80%) & t2575 (20%), respectively. One MRSA isolate carried a novel SCCmec type V. The luk-PV and tsst-1 genes were present in 93.75% and 33.33% of MRSA isolates, respectively. The concordance between the phenotypic and genotypic AST results was 100% for Beta-lactams, Fluoroquinolones, Tetracyclines & Lipoglycopeptides, respectively.

CONCLUSIONS

Through this study, we intend to embark upon a relatively newer avenue of clinical-genomic surveillance of nosocomial bacterial isolates like MRSA, which would help us improve the existing infection control and antibiotic stewardship practices in our hospital.

Methicillin resistant Staphylococcus aureus isolated from surgical patients in Cambodia over a 10-year period

Methicillin-resistant Staphylococcus aureus (MRSA) related surgical infections are a global challenge. The burden of antimicrobial resistance is high throughout South-East Asia, and this is reflected in our local institution in Cambodia. Between 2011 and 2013, we analysed 251 wound swab samples at the Children's Surgical Centre, Phnom Penh; 52.5% of the Staphylococcus aureus isolates (n = 52/99) were MRSA positive. Ten years on, we have sought to investigate whether there is a difference in MRSA rates within our adult and paediatric patient population. Between 2020 and 2022, MRSA rates in our patient population have remained similar at 53.8% (n = 42/78). Resistance profiles of MRSA isolates have also remained similar with a significant proportion of MRSA still showing sensitivity to trimethoprim-sulfamethoxazole and tetracycline. We also find that patients presenting with wound infection secondary to trauma or orthopaedic implants had greater propensity to yield MRSA.

Molecular Epidemiology of Staphylococcus aureus in China Reveals the Key Gene Features Involved in Epidemic Transmission and Adaptive Evolution

Staphylococcus aureus is a Gram-positive pathogen that causes various infections in humans and domestic animals. In China, S. aureus is the most common Gram-positive pathogen that causes clinical infections. However, there are few comprehensive genome-based molecular epidemiology studies to investigate the genotypic background of the major S. aureus clones that are epidemic in China. Here, four S. aureus isolates that were recovered from hospital personnel were sequenced. In combination with whole-genome sequencing (WGS) data of 328 S. aureus strains as references, we performed a comprehensive molecular epidemiology study to reveal the molecular epidemic characterization of S. aureus that is epidemic in China. It was found that 332 S. aureus isolates were phylogenetically categorized into 4 major epidemic groups with different epidemiology phenotypes. Each group has exclusive features in virulence genotypic profiles, antimicrobial resistance genotypic profiles, core and pangenome features representing the differences involved in genetic features, evolutionary processes, and potential future evolutionary directions. Moreover, a comparative core genome analysis of 332 S. aureus isolates indicated several key genes that contributed to differences in molecular epidemic characterization and promoted the adaptive evolutionary process of each group. This study provides a comprehensive understanding of molecular epidemiological characteristics and adaptive evolutionary directions of major S. aureus clones that are epidemic in China. IMPORTANCE Staphylococcus aureus is an important Gram-positive pathogen that is epidemic worldwide and causes various infections in humans and domestic animals. However, there has been relatively little research on comprehensive molecular epidemiology in China. In this research, we reconstructed the phylogenetic relationship based on whole-genome data of strains almost all over China, screened for resistance and virulence genes, and took core and pan genome analysis to perform a comprehensive molecular epidemiology study of S. aureus that is epidemic in China. Our results highlight that there are 4 major epidemic groups with different epidemiology phenotypes after phylogenetic categorization with exclusive genetic features in virulence genotypic profiles, antimicrobial-resistance genotypic profiles, and core and pangenome features, and we found key gene features involved in epidemic transmission and adaptive evolution. Our findings are critical in describing molecular characteristic profiles of S. aureus infection, which could update existing preventive measures and take appropriate strategies.

Genomic Insights of First ermB-Positive ST338-SCCmecVT/CC59 Taiwan Clone of Community-Associated Methicillin-Resistant Staphylococcus aureus in Poland

We report the first Polish representative of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA), lukS/F-PV-positive, encoding the ermB gene, as a genetic determinant of constitutive resistance to macrolides, lincosamides, and streptogramin B antibiotics, cMLS-B. This is the first detection of the CA-MRSA strain responsible for nosocomial infection in the Warsaw Clinical Hospital. Resistance to β-lactams associates with a composite genetic element, SCCmec cassette type V_T (5C2&5). We assigned the strain to sequence type ST338 (single-locus variant of ST59), clonal complex CC59, spa-type t437, and agr-type I. Genomic-based comparison was designated SO574/12 as an international Taiwan clone, which has been so far described mainly in the Asia-Pacific region. The ermB gene locates on the chromosome within the 14,690 bp mobile element structure, i.e., the MES_PM1-like structure, which also encodes aminoglycoside- and streptothricin-resistance genes. The MES_PM1-like structure is a composite transposon containing Tn551, flanked by direct repeats of IS1216V insertion sequences, which probably originates from Enterococcus. The ermB is preceded by the 273 bp regulatory region that contains the regulatory 84 bp ermBL ORF, encoding the 27 amino acid leader peptides. The latest research suggests that a new leader peptide, ermBL2, also exists in the ermB regulatory region. Therefore, the detailed function of ermBL2 requires further investigations.

Investigating Unfavorable Factors That Impede MALDI-TOF-Based AI in Predicting Antibiotic Resistance

The combination of Matrix-Assisted Laser Desorption/Ionization Time-of-Flight (MALDI-TOF) spectra data and artificial intelligence (AI) has been introduced for rapid prediction on antibiotic susceptibility testing (AST) of Staphylococcus aureus. Based on the AI predictive probability, cases with probabilities between the low and high cut-offs are defined as being in the “grey zone”. We aimed to investigate the underlying reasons of unconfident (grey zone) or wrong predictive AST. In total, 479 S. aureus isolates were collected and analyzed by MALDI-TOF, and AST prediction and standard AST were obtained in a tertiary medical center. The predictions were categorized as correct-prediction group, wrong-prediction group, and grey-zone group. We analyzed the association between the predictive results and the demographic data, spectral data, and strain types. For methicillin-resistant S. aureus (MRSA), a larger cefoxitin zone size was found in the wrong-prediction group. Multilocus sequence typing of the MRSA isolates in the grey-zone group revealed that uncommon strain types comprised 80%. Of the methicillin-susceptible S. aureus (MSSA) isolates in the grey-zone group, the majority (60%) comprised over 10 different strain types. In predicting AST based on MALDI-TOF AI, uncommon strains and high diversity contribute to suboptimal predictive performance.

Methicillin-resistant Staphylococcus aureus in China: a multicentre longitudinal study and whole-genome sequencing

The aim of this study was to investigate the genomic epidemiology of MRSA in China to identify predominant lineages and their associated genomic and phenotypic characteristics. In this study, we conducted whole-genome sequencing on 565 MRSA isolates from 7 provinces and municipalities of China between 2014 and 2020. MRSA isolates were subjected to MLST, spa typing, SCCmec typing, analysis of virulence determinants and antimicrobial susceptibility testing. Among 565 MRSA isolates tested, clonal complex (CC) 59 (31.2%), CC5 (23.4%) and CC8 (13.63%) were the major lineages, and the clonal structure was dominated by ST59-t437-IV (14.9%), ST239-t030-III (6.4%) and ST5-t2460-II (6.0%), respectively. Of note, CC8, the predominant lineage in 2014–2015, was replaced by CC59 after 2016. Interestingly, the extension and unstable structure of the CC5 population was observed, with ST5-t311-II, ST764-t1084-II, ST5-t2460-II and ST764-t002-II existing complex competition. Further analysis revealed that virulence determinant profiles and antibiograms were closely associated with the clonal lineage. The CC59 MRSA was less resistant to most tested antimicrobials and carried fewer resistance determinants. But rifampicin resistance and mupirocin resistance were closely linked with CC8 and CC5, respectively. MRSA isolates conservatively carried multiple virulence genes involved in various functions. PVL encoding genes were more common in ST338, CC30, CC398, ST8 and CC22, while tsst-1 was associated with ST5. In conclusion, the community-associated CC59-ST59-t437-IV lineage was predominant in China, with diverse clonal isolates alternately circulating in various geographical locations. Our study highlights the need for MRSA surveillance in China to monitor changes in MRSA epidemiology.

A longitudinal molecular surveillance of clinical methicillin-resistant Staphylococcus aureus isolates in neonatal units in a teaching hospital, 2003-2018

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) has been an important nosocomial pathogen in our neonatal units since 1990s. To understand the longitudinal changing molecular epidemiology of these MRSA isolates, we conducted this study.

MATERIALS

From 2003 to 2018, we collected clinical MRSA isolates from 536 infants hospitalized at neonatal units of a medical center in northern Taiwan. First isolate from each infant was characterized.

RESULTS

The case/isolate number ranged from 7 cases/isolates (the lowest) in 2010 to 71 cases/isolates (the highest) in 2004. Of the 536 isolates, a total of 15 pulsotypes were identified. Three major clones were identified and characterized as sequence type (ST) 239/pulsotype A/staphylococcal chromosomal cassette (SCC) mec III/Panton-Valentine leukocidin (PVL)-negative, accounting for 22.2% of the isolates, ST59/pulsotype C/SCCmec IV/PVL-negative, accounting for 34.3% and ST59/pulsotype D/SCCmec V_T/PVL-positive, accounting for 30.0%. The first clone (hospital strains) dominated in the first two years, and became weakened from 2005 through 2016. Clonal complex (CC) 59 (combined the second and third clones) dominated (>50% of the isolates) from 2005 through 2018. One community clone (ST573) demonstrated a marked increase since 2007 and vanished abruptly since 2010. Several minor MRSA clones emerged after 2010.

CONCLUSION

The molecular epidemiology of MRSA isolates in our neonatal units from 2003 to 2018 revealed that an epidemic as well as endemic hospital clone of ST239 dominated before 2005 and was replaced by the local community clone of CC59 thereafter.

The First Report of a Methicillin-Resistant Staphylococcus aureus Isolate Harboring Type IV SCCmec in Thailand

Methicillin-resistant Staphylococcus aureus (MRSA) is mostly found in Thailand in the hospital as a nosocomial pathogen. This study aimed to report the genetic characterization of a clinical community-acquired MRSA (CA-MRSA) isolate collected from hospitalized patients in Thailand. Among 26 MRSA isolates, S. aureus no. S17 preliminarily displayed the presence of a staphylococcal cassette chromosome mec (SCCmec) type IV pattern. The bacterial genomic DNA was subjected to whole-genome sequencing. Panton-Valentine leukocidin (PVL) production, virulence toxins, and antibiotic resistance genes were identified, and multi-locus sequence typing (MLST) and spa typing were performed. The strain was matched by sequence to MLST type 2885 and spa type t13880. This strain carried type IV SCCmec with no PVL production. Five acquired antimicrobial resistance genes, namely blaZ, mecA, Inu(A), tet(K), and dfrG conferring resistance to β-lactams, lincosamides, tetracycline, and trimethoprim, were identified. The detected toxins were exfoliative toxin A, gamma-hemolysin, leukocidin D, and leukocidin E. Moreover, there were differences in seven regions in CR-MRSA no. S17 compared to CA-MRSA type 300. In summary, we have reported the ST2885-SCCmec IV CA-MRSA clinical strain in Thailand for the first time, highlighting the problem of methicillin resistance in community settings and the consideration in choosing appropriate antibiotic therapy.

Clinical and molecular characteristics of Staphylococcus aureus isolated from Chinese children: association among the agr groups and genotypes, virulence genes and disease types

BACKGROUND

This study was aimed to investigate the clinical and molecular epidemiology of Staphylococcus aureus (S. aureus) isolated from Chinese children and determine the possible relationship among the accessory gene regulator (agr) groups and genotypes, as well as among the virulence genes and disease types.

METHODS

S. aureus strains were isolated from Beijing Children's Hospital between October 2017 and October 2019. The isolates and 19 virulence genes were characterized using multi-locus sequence typing, staphylococcal protein A (spa), staphylococcal cassette chromosome mec, and agr typing.

RESULTS

A total of 191 non-repetitive S. aureus clinical isolates were divided into 33 sequence types (STs), 18 clonal complexes (CCs), and 59 spa types. ST59 (39.8%), t437 (37.7%), and agr I (84.8%) were the predominant types. CC59, CC25, CC22, CC951, CC8, and CC398 belonged to agr I. CC5 and CC15 were assigned to agr II, and CC30 was characterized as agr III. CC121 was classified under agr IV. The eta, etb, and bbp genes were more prevalent in agr IV (P < 0.001 for each), while tst was more prevalent in agr group III compared to the other groups (P < 0.001). Nearly all isolates that harbored lukS/F-PV belonged to agr I (P = 0.005). However, the correlation between disease types and agr groups was not significant (P > 0.05).

CONCLUSIONS

An association among the agr groups and genotypes, as well as specific toxin genes, was observed among the S. aureus strains isolated from Chinese children. However, a statistical correlation was not found among the agr groups and disease types.

Prevalence, predictors, and mortality of bloodstream infections due to methicillin-resistant Staphylococcus aureus in patients with malignancy: systemic review and meta-analysis

BACKGROUND

Cancer patients are more likely to develop and die of bloodstream infection (BSI) than noncancer patients. Methicillin-resistant Staphylococcus aureus (MRSA), which is associated with immense mortality and economic burden worldwide, is not covered by the recommended initial antibiotic therapy for cancer patients with BSI. This systemic review was performed to estimate the global methicillin-resistant Staphylococcus aureus (MRSA) prevalence among bacteremia in patients with malignancy, and further study the predictors and mortality of cancer patients with MRSA bacteremia.

METHODS

The PubMed and EMBASE databases were searched for studies published from Jan. 2000 to Mar. 2020 that provided primary data on the prevalence, predictors, or mortality of MRSA bacteremia in cancer patients. A random-effects model meta-analysis was performed to estimate the pooled prevalence of MRSA with 95% confidence intervals (95% CIs).

RESULTS

The pooled prevalence of MRSA was 3% (95% CI 2-5%) among all bloodstream infections (BSIs) and 44% (95% CI 32-57%) among S. aureus bacteremia in cancer patients. Based on geographical stratification, the pooled prevalence was 5% in Africa (95% CI 1-14%), 1% in Americas (95% CI 1-2%), 2% in Europe (95% CI 1-4%), 4% in Western Pacific (95% CI 2-7%), 8% in South-east Asia (95% CI 4-14%) and 0% in Eastern Mediterranean (95% CI 0-3%). No significant temporal change in MRSA rates was detected in this analysis (R2 = 0.06; P = 0.24). Predictors for MRSA BSIs among cancer patients were identified by comparison with their methicillin-susceptible counterparts, and they were mainly related to healthcare-associated infections and immunosuppression. Finally, the 60-day mortality in adult cancer patients with MRSA BSIs was reported to be 12%, and the 6-month overall mortality was 43.2%, with community-onset infection, secondary BSI, and vancomycin MIC≥2 g/mL being the risk factors for mortality.

CONCLUSIONS

Although the prevalence of MRSA BSIs among cancer patients is relatively low, it did not decline over time as MRSA BSIs in the general hospital population and the high mortality rate was related to MRSA BSIs in patients with malignancy.

Prevalence, Characterization, and Drug Resistance of Staphylococcus Aureus in Feces From Pediatric Patients in Guangzhou, China

Background: Staphylococcus aureus (S. aureus) is a major pathogen of human infections. Its fecal carriage serves as a risk factor for nosocomial transmission and disease development. However, the rate of S. aureus fecal carriage among Chinese children has not yet been reported. Therefore, we sought to investigate the prevalence, characterization, and drug resistance of S. aureus isolated from pediatric patients' feces in Southern China. Methods: Fecal samples (2059) from pediatric patients in three centers in Guangzhou were cultured. From which, 412 S. aureus isolates were identified via selective mediums and automated VITEK Mass Spectrometer analysis. Antibiotic susceptibility was determined and DNA sequencing of seven housekeeping genes were used for multilocus sequence typing analysis. Results: The fecal carriage rates were 20.0% for S. aureus and 4.5% for methicillin-resistant S. aureus (MRSA). Moreover, S. aureus fecal carriage was positively correlated with outpatient status and gastroenteritis diagnosis. Moreover, age-related patterns were observed with respect to prevalence of S. aureus. Besides, a total of 76 sequence types (STs) were identified, including 25 newly assigned STs and 28 clonal complexes (CCs). ST188, ST6, and ST15 were the most prevalent methicillin-sensitive S. aureus (MSSA) clones, while ST59 and ST45 were the major MRSA clones. S. aureus isolates also exhibited high rates of penicillin (84.2%), erythromycin (38.8%), and clindamycin (35.9%) resistance. Specifically, all ST30 and ST338 isolates were resistant to erythromycin and clindamycin, 61% of ST7 were resistant to tetracycline, and 84% of ST45 exhibited resistance and intermediate resistance to rifampicin. Also, CC59 (ST338 and ST59) and CC45 exhibited different antibiotic resistance patterns. Conclusion: These results demonstrate the colonization dynamics and molecular epidemiology of S. aureus in child feces in Southern China. Further, they suggest an urgency for strengthening the surveillance programs in China and provide important information for the prevention and treatment of S. aureus infection.

Marked increase in community-associated methicillin-resistant Staphylococcus aureus infections, Western Australia, 2004-2018

This study presents enhanced surveillance data from 2004 to 2018 for all community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) specimens collected in Western Australia (WA), and describes the changing epidemiology over this period. A total of 57 557 cases were reviewed. Annual incidence rates increased from 86.2 cases per 100 000 population to 245.6 per 100 000 population (IRR = 2.9, CI95 2.7-3.0). The proportion of isolates carrying Panton-Valentine leucocidin (PVL)-associated genes increased from 3.4% to 59.8% (χ2 test for trend 7021.9, P < 0.001). The emergence of PVL-positive, 'Queensland CA-MRSA' (ST93-IV) and 'WA 121' (ST5-IV) accounted for the majority of increases in CA-MRSA across the study period. It is unclear why some clones are more prolific in certain regions. In WA, CA-MRSA rates increase as indices of temperature and humidity increase after controlling for socioeconomic disadvantage. We suggest climatic conditions may contribute to transmission, along with other socio-behavioural factors. A better understanding of the ability for certain clones to form ecological niches and cause outbreaks is required.

A comparative genomic analysis between methicillin-resistant Staphylococcus aureus strains of hospital acquired and community infections in Yunnan province of China

BACKGROUND

Currently, Staphylococcus aureus is one of the most important pathogens worldwide, especially for methicillin-resistant S. aureus (MRSA) infection. However, few reports referred to patients' MRSA infections in Yunnan province, southwest China.

METHODS

In this study, we selected representative MRSA strains from patients' systemic surveillance in Yunnan province of China, performed the genomic sequencing and compared their features, together with some food derived strains.

RESULTS

Among sixty selective isolates, forty strains were isolated from patients, and twenty isolated from food. Among the patients' strains, sixteen were recognized as community-acquired (CA), compared with 24 for hospital-acquired (HA). ST6-t701, ST59-t437 and ST239-t030 were the three major genotype profiles. ST6-t701 was predominated in food strains, while ST59-t437 and ST239-t030 were the primary clones in patients. The clinical features between CA and HA-MRSA of patients were statistical different. Compared the antibiotic resistant results between patients and food indicated that higher antibiotic resistant rates were found in patients' strains. Totally, the average genome sizes of 60 isolates were 2.79 ± 0.05 Mbp, with GC content 33% and 84.50 ± 0.20% of coding rate. The core genomes of these isolates were 1593 genes. Phylogenetic analysis based on pan-genome and SNP of strains showed that five clustering groups were generated. Clustering ST239-t030 contained all the HA-MRSA cases in this study; clustering ST6-t701 referred to food and CA-MRSA infections in community; clustering ST59-t437 showed the heterogeneity for provoking different clinical diseases in both community and hospital. Phylogenetic tree, incorporating 24 isolates from different regions, indicated ST239-t030 strains in this study were more closely related to T0131 isolate from Tianjin, China, belonged to 'Turkish clade' from Eastern Europe; two groups of ST59-t437 clones of MRSA in Yunnan province were generated, belonged to the 'Asian-Pacific' clone (AP) and 'Taiwan' clone (TW) respectively.

CONCLUSIONS

ST239-t030, ST59-t437 and ST6-t701 were the three major MRSA clones in Yunnan province of China. ST239-t030 clonal Yunnan isolates demonstrated the local endemic of clone establishment for a number of years, whereas ST59-t437 strains revealed the multi-origins of this clone. In general, genomic study on epidemic clones of MRSA in southwest China provided the features and evolution of this pathogen.

Characterization of a community-acquired methicillin-resistant sequence type 338 Staphylococcus aureus strain containing a staphylococcal cassette chromosome mec type VT

OBJECTIVES

To determine the molecular characteristics of a sequence type 338 community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) strain and the relationship among MRSA strains from various lineages and areas.

METHODS

Whole-genome sequencing, genomic comparison, antimicrobial susceptibility testing, and hemolysis analysis were performed to identify the resistance determinants and virulence factors of strain ZY05 and the relationships among CC59 clones.

RESULTS

MRSA strain ZY05 was resistant to tetracycline, erythromycin, and clindamycin, and the resistance genes erm(B) and tet(K) were detected in the genome. ZY05 harbors the genomic islands νSaα, νSaβ, νSaγ, and ΦSa2, the pathogenicity island νSa1, and virulence factors such as Panton-Valentine leukocidin, phenol-soluble modulins, alpha-hemolysin, enterotoxin B, enterotoxin K, and enterotoxin Q, which are the same as those present in ST59 strains. In addition, the virulence potential of ST338 did not differ from that of ST59. This strain contains the staphylococcal cassette chromosome mec (SCCmec) type V_T, a distinct SCCmec type previously reported from Taiwan. The results of core genome multilocus sequence typing (cgMLST) analysis showed that the gene distances between ST59 and ST338 were close among CC59 isolates, while strains from Taiwan were identical to isolates from the Chinese mainland with respect to these two sequence types.

CONCLUSIONS

The ST338 strain ZY05, which has a close genetic relationship to ST59 strains, is multidrug-resistant and highly virulent. Strains of two identical lineages, ST59 and ST338, from Taiwan and the Chinese mainland may have the same genetic background.

Dissecting the Heterogeneous Population Genetic Structure of Candida albicans: Limitations and Constraints of the Multilocus Sequence Typing Scheme

Candida albicans is a fungal opportunistic pathogen of significant public health importance mainly due to the recent emergence of strains with increased aggressiveness and antifungal resistance. Here, we aimed to describe the epidemiological profiles and approximate the population structure of C. albicans by analyzing the C. albicans multilocus sequence typing (MLST) database (Calb-MLST-DB), which contains the largest publically available dataset for this species. Based on 4,318 database isolates, we confirmed the ubiquitous nature of C. albicans including a group of diploid sequence types (DSTs) obtained from Healthy individuals exclusively (taken as an indicator of lack of association with illnesses in its host), until isolates established from Non-Healthy individuals (potentially associated with pathogenic processes) and other DSTs reported in both types (Healthy and Non-Healthy). The highest number of reported DSTs was related to blood, oral and vaginal swabs (32.4, 20.5, and 13.8%, respectively). High genetic diversity was observed in the seven housekeeping genes included in the MLST scheme, with a diverse population structure (154 clonal complexes, CCs; and a high number of singletons, n = 1,074). Phylogenetic reconstruction on the concatenated alignment of these housekeeping genes for all the reported DSTs (n = 3,483) was partially concordant with the CC assignment, however, an absence of bootstrap threshold supported nodes or p-distance, and the lack of association with the other epidemiological variables, evidenced the limitations of the MLST scheme. Marked genetic admixture signals were identified by STRUCTURE, with the majority being attributable to recombination events according to the RDP program results, although another type of exchange event cannot be ruled out. Our results reaffirm the genetic diversity inherent in the genes used for the MLST scheme, which are associated with the chromosomal remodeling already proposed for C. albicans. This was also corroborated with an internal validation at a micro geographical scale. Despite these results are biased due to the unavailability of considering the broad global spectrum of C. albicans isolates around the world. This suggests that the strategy used to population type this pathogen should be reevaluated to improve epidemiological monitoring of its health impact.

Aminobenzylated 4-Nitrophenols as Antibacterial Agents Obtained from 5-Nitrosalicylaldehyde through a Petasis Borono-Mannich Reaction

Multidrug-resistant bacteria are one of the current biggest threats to public health and are responsible for most nosocomial infections. Herein, we report the efficient and facile synthesis of antibacterial agents aminoalkylphenols, derived from 5-nitrosalicyladehyde and prepared through a Petasis borono-Mannich multicomponent reaction. Minimum inhibitory concentrations (MICs) as low as 1.23 μM for a chlorine derivative were determined for multidrug-resistant Gram-positive bacteria, namely, Staphylococcus aureus and Enterococcus faecalis, two of the main pathogens responsible for infections in a hospital environment. The most promising antibacterial agents were further tested against eight strains of four Gram-positive species in order to elucidate their antibacterial broadness. In vitro cytotoxicity assays of the most active aminoalkylphenol revealed considerably lower toxicity against mammalian cells, as concentrations one order of magnitude higher than the determined MICs were required to induce human keratinocyte cell death. The phenol moiety was verified to be important in deeming the antibacterial properties of the analyzed compounds, although no correlation between such properties and their antioxidant activity was observed. A density functional theory computational study substantiated the ability of aminoalkylphenols to serve as precursors of ortho-quinone methides.

A molecular epidemiological study of methicillin-resistant and methicillin-susceptible Staphylococcus aureus contamination in the airport environment

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) causes a wide variety of serious infections worldwide. There are few studies on the prevalence, antimicrobial susceptibility, and molecular characteristics of MRSA contamination in the environment of airports.

MATERIALS AND METHODS

A cross-sectional survey was conducted in Guangzhou Baiyun Airport. Environmental surface sampling was conducted in frequently touched locations for S. aureus analysis. All isolates were characterized by multilocus sequence typing (MLST) and tested for antimicrobial susceptibility, resistance genes, and virulence genes. Data were analyzed by chi-squared test and correspondence analysis.

RESULTS

Of the 1,054 surface samples, the contamination rate was 7.2% (76/1,054) for S. aureus and 2.2% (23/1,054) for MRSA. There were 62.9% (56/89) S. aureus isolates classified as multidrug resistant (MDR), with six linezolid-resistant isolates and two cfr-carrying isolates. The most prevalent S. aureus genotypes were CC6 (ST6), CC59 (ST59), and CC188 (ST188), with ST59-MRSA-IV (pvl-) as the predominant MRSA. There were significant differences between methicillin-resistant and methicillin-sensitive isolates in rates of resistance to tetracycline (P<0.001) and sek carriage (P=0.029). The correspondence analyses revealed significant corresponding relationships between genotypes and phenotype-genotype characteristics of S. aureus isolates.

CONCLUSION

Our findings revealed a potential risk of cross-transmission of MRSA between human beings and environments, suggesting more stringent contamination control measures. In addition, this study revealed significant corresponding relationships between genotypes and phenotype-genotype characteristics of S. aureus isolates, which may provide new ideas for monitoring the latest epidemiological trends.

Import of community-associated, methicillin-resistant Staphylococcus aureus to Europe through skin and soft-tissue infection in intercontinental travellers, 2011-2016

OBJECTIVES

Recently, following import by travel and migration, epidemic community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has caused nosocomial outbreaks in Europe, sometimes with a fatal outcome. We describe clinico-epidemiological characteristics of CA-MRSA detected by the European Network for the Surveillance of imported S. aureus (www.staphtrav.eu) from May 2011 to November 2016.

METHODS

Sentinel surveillance at 13 travel clinics enrolling patients with travel-associated skin and soft-tissue infection (SSTI) and analysing lesion and nose swabs at one central laboratory.

RESULTS

A total of 564 independent case-patients with SSTI were enrolled and had 374 (67%) S. aureus-positive lesions, of which 14% (51/374) were MRSA. The majority of CA-MRSA isolates from SSTI were Panton-Valentine leucocidin (PVL) -positive (43/51, 84%). The risk of methicillin-resistance in imported S. aureus varied by travel region (p <0.001) and was highest in Latin America (16/57, 28%, 95% CI 17.0-41.5) and lowest in Sub-Saharan Africa (4/121, 3%, 95% CI 0.9-8.3). Major epidemic clones (USA300 / USA300 Latin-American Variant, Bengal Bay, South Pacific) accounted for more than one-third (19/51, 37%) of CA-MRSA imports. CA-MRSA SSTI in returnees was complicated (31/51 multiple lesions, 61%; 22/50 recurrences, 44%), led to health-care contact (22/51 surgical drainage, 43%; 7/50 hospitalization, 14%), was transmissible (13/47 reported similar SSTI in non-travelling contacts, 28%), and associated with S. aureus nasal colonization (28 of 51 CA-MRSA cases, 55%; 24 of 28 colonized with identical spa-type in nose and lesion, 85%).

CONCLUSIONS

Travel-associated CA-MRSA SSTI is a transmissible condition that leads to medical consultations and colonization of the infected host.

Determinants of methicillin-resistant Staphylococcus aureus (MRSA) prevalence in the Asia-Pacific region: A systematic review and meta-analysis

OBJECTIVES

Published literature on methicillin-resistant Staphylococcus aureus (MRSA) in the Asia-Pacific region was reviewed to document the prevalence of MRSA in the region and to examine the impact of variability in study design on the reported MRSA prevalence data.

METHODS

This review included studies reporting MRSA prevalence between 2000 and 2016. Studies were excluded if they did not contain complete information on antimicrobial susceptibility testing (AST) methods. Primary outcomes were the proportion of MRSA among S. aureus isolates (resistance proportion) or among individual samples (prevalence).

RESULTS

A total of 229 studies in 19 countries/territories were included in the study. There was substantial heterogeneity in both outcomes (resistance proportion, I²=99.59%; prevalence, I²=99.83%), precluding pooled averages, and meta-regression analyses revealed that these variations were explained by country income status and participant characteristics but not by methodological differences in AST. Also, no significant secular changes in MRSA prevalence or resistance proportions in Asia-Pacific were found.

CONCLUSION

The resistance proportions and prevalence of MRSA infections in Asia-Pacific are comparable with those reported in other regions with no significant secular changes in the past decade. Country income status and characteristics of the sample population explained more variation in the reported resistance proportions and prevalence of MRSA than methodological differences in AST across locations in the region.

Comparative and molecular analysis of MRSA isolates from infection sites and carrier colonization sites

Background

Methicillin resistant Staphylococcus aureus (MRSA) constitutes a major global health concern causing hospital and community acquired infections. A wide diversity of MRSA genotypes are circulating in geographically related regions. Therefore understanding the molecular epidemiology of MRSA is fundamental to design control and clearance measures.

Methods

A total of 106 MRSA isolates from infection (51) and carrier colonization sites (55) are characterized genetically based on SCCmec and MLST genotyping methods in addition to detection of PVL, TSST-1 and enterotoxins.

Results

Sccmec-IV was the most frequently detected genotype (77.3%) followed by genotype V (13.2%) and III (9.4%). SCCmec-IVa was more prevalent among the carrier group (p value 0.002). CC80 was the most commonly identified clonal complex (CC). CC6 and CC22 were significantly more prevalent among the carrier group (p value 0.02 and 0.01, respectively). PVL was highly prevalent among the isolates (58.5%). PVL was detected in 70.6% of isolates from infection sites and 47.3% of isolates from carriers. All strains were sensitive to vancomycin, however, MRSA strains isolated from infection sites had significantly higher MICs compared to strains isolated from carrier colonization sites (p value 0.021). Five new sequence types mainly from the carrier group were identified and described in the study.

Conclusions

MRSA population is genetically very diverse among carriers and infected individuals. With SCCmec type IV being most prevalent, this suggests a community origin of most MRSA strains. Therefore very well designed surveillance and clearance strategies should be prepared to prevent emergence and control spread of MRSA in the community.