Comparison of methicillin-resistant Staphylococcus aureus strains isolated in 2003 and 2008 with an emergence of multidrug resistant ST22: SCCmec IV clone in a tertiary hospital, Malaysia

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.

Dissemination Pattern of Hospital-Acquired Methicillin-Resistant Staphylococcus aureus and Community-Acquired MRSA Isolates from Malaysian Hospitals: A Review from a Molecular Perspective

The global emergence of methicillin-resistant Staphylococcus aureus (MRSA) that unsusceptible to a wide selection of antimicrobial agents and any newly introduced antimicrobial over the past decades has triggered more extensive holistic measures to put an end to this situation. Molecular surveillance of MRSA clones is important to understand their evolutionary dynamics for investigating outbreaks, propagating precautionary measures, as well as planning for appropriate treatment. This review includes peer-reviewed reports on the molecular characterisation of clinical Staphylococcus aureus isolates within Malaysian hospitals from year 2008 to 2020. This work highlights the molecular clones of hospital-acquired MRSA (HA-MRSA) and community-acquired MRSA (CA-MRSA) isolates from Malaysian hospitals, with description on their ever-changing pattern. Among HA-MRSA, the ST22-t032-SCCmec IV MRSA clone was reported to supplant the previous dominating clone, ST239-t037-SCCmec III. Meanwhile, ST30, ST772, ST6 and ST22 were repeatedly detected in CA-MRSA, however, none of the strains became predominant. Future in-depth study on molecular epidemiology of MRSA clone is essential for the investigation of the extent of the clonal shift, especially in Malaysia.

Diversity and Dissemination of Methicillin-Resistant Staphylococcus aureus (MRSA) Genotypes in Southeast Asia

Methicillin-resistant Staphylococcus aureus (MRSA) is a successful pathogen that has achieved global dissemination, with high prevalence rates in Southeast Asia. A huge diversity of clones has been reported in this region, with MRSA ST239 being the most successful lineage. Nonetheless, description of MRSA genotypes circulating in the Southeast Asia region has, until now, remained poorly compiled. In this review, we aim to provide a better understanding of the molecular epidemiology and distribution of MRSA clones in 11 Southeast Asian countries: Singapore, Malaysia, Thailand, Vietnam, Cambodia, Lao People's Democratic Republic (PDR), Myanmar, Philippines, Indonesia, Brunei Darussalam, and Timor-Leste. Notably, while archaic multidrug-resistant hospital-associated (HA) MRSAs, such as the ST239-III and ST241-III, were prominent in the region during earlier observations, these were then largely replaced by the more antibiotic-susceptible community-acquired (CA) MRSAs, such as ST22-IV and PVL-positive ST30-IV, in recent years after the turn of the century. Nonetheless, reports of livestock-associated (LA) MRSAs remain few in the region.

Genetic Diversity among Methicillin-Resistant Staphylococcus aureus in Malaysia (2002-2020)

1.

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) is a common organism seen in both healthcare-associated and community-associated infections worldwide and in Malaysia over the past two decades. The aim of this review is to provide a firsthand documentation of all MRSA strains prevalent in the Malaysian population from 2002 to present and briefly describe the changing patterns. 2.

METHODS

Electronic and manual intensive literature searches were conducted between 2002 and 2020, addressing issues directly related to patients and published in the English language were selected. 3.

RESULTS

The literature search retrieved a total of 2217 articles and abstracts of 27 articles. The search yielded a total of 24 articles on genotyping of MRSA in Malaysia. The study found that MRSA strains were mostly genetically related and resulted in the predominant MRSA clones that caused active infections. Thirty-six different sequence types (ST) were recorded. The highest rates of STs detected were ST239 (52.6%), ST1 (47.4%), and ST22 (42.1%). The majority of studies showed that both SCCmec types III and IV were the most common SCCm type in Malaysia, followed by SCCmec type V (57.9%). 4.

CONCLUSIONS

Both Brazilian (ST 239 IIIA) and Hungarian (ST 239-III) MRSA strains were detected in Malaysia. PFGE remains the best method for comparing MRSA strains. However, whole-genome sequencing has a promising chance to replace PFGE in the future.

The global prevalence of fusidic acid resistance in clinical isolates of Staphylococcus aureus: a systematic review and meta-analysis

BACKGROUND AND AIM

Staphylococcus aureus (S. aureus) is one of the most common pathogens causing nosocomial and community-acquired infections with high morbidity and mortality rates. Fusidic acid has been increasingly used for the treatment of infections due to methicillin-susceptible S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA). The present study aimed to determine the precise prevalence of fusidic acid resistant MRSA (FRMRSA), fusidic acid resistant MSSA (FRMSSA), and total fusidic acid resistant S. aureus (FRSA) on a global scale.

METHODS

Several international databases including Medline, Embase, and the Web of Sciences were searched (2000-2020) to discern studies addressing the prevalence of FRSA, FRMRSA, and FRMSSA. STATA (version14) software was used to interpret the data.

RESULTS

Of the 1446 records identified from the databases, 215 studies fulfilled the eligibility criteria for the detection of FRSA (208 studies), FRMRSA (143 studies), and FRMSSA (71 studies). The analyses manifested that the global prevalence of FRSA, FRMRSA, and FRMSSA was 0.5%, 2.6% and 6.7%, respectively.

CONCLUSION

This meta-analysis describes an increasing incidence of FRSA, FRMSSA, and FRMRSA. These results indicate the need for prudent prescription of fusidic acid to stop or diminish the incidence of fusidic acid resistance as well as the development of strategies for monitoring the efficacy of fusidic acid use.

spa diversity of methicillin-resistant and -susceptible Staphylococcus aureus in clinical strains from Malaysia: a high prevalence of invasive European spa-type t032

Background

Staphylococcus aureus is one of the important pathogens causing nosocomial infection. spa typing allows identification of S. aureus clones in hospital isolates and is useful for epidemiological studies and nosocomial infection control. This study aims to investigate the spa types in Malaysian S. aureus isolates obtained from various clinical specimens.

Method

A total of 89 methicillin-resistant S. aureus (MRSA) [pus (n = 55), blood (n = 27), respiratory (n = 5), eye (n = 2)] isolates and 109 methicillin-susceptible S. aureus (MSSA) [pus (n = 79), blood (n = 24), respiratory (n = 3), eye (n = 2) and urine (n = 1)] isolates were subjected to spa typing with sequences analysed using BioNumerics version 7.

Results

The spa sequence was successfully amplified from 77.8% of the strains (154/198) and 47 known spa types were detected. The distribution of known spa types in MRSA (36.2%, 17/47) was less diverse than in MSSA (70.2%, 33/47). The most predominant spa types were t032 (50%) in MRSA, and t127 (19%) and t091 (16.7%) in MSSA, respectively. spa type t091 in MSSA was significantly associated with skin and soft tissue infections (p = 0.0199).

Conclusion

The previously uncommon spa type t032 was detected in the Malaysian MRSA strains, which also corresponded to the most common spa type in Europe and Australia, and has replaced the dominant spa type t037 which was reported in Malaysia in 2010.

Methicillin-Resistant Staphylococcus aureus (MRSA) Clonal Replacement in a Malaysian Teaching Hospital: Findings from an Eight-Year Interval Molecular Surveillance

Periodical surveillance on nosocomial pathogens is important for antimicrobial stewardship and infection control. The first methicillin-resistant Staphylococcus aureus (MRSA) molecular surveillance in Hospital Canselor Tuanku Muhriz (HCTM), a Malaysian teaching hospital, was performed in 2009. The dominant clone was identified as an MRSA carrying SCCmec type III-SCCmercury with ccrC and sea+cna toxin genes. In this study, we report the findings of the second HCTM MRSA surveillance carried out in 2017, after an interval of 8 years. Antibiotic susceptibility testing, SCCmec, toxin gene, and spa typing were performed for 222 MRSA strains isolated in 2017. Most strains were resistant to ciprofloxacin, erythromycin, clindamycin, cefoxitin, and penicillin (n = 126, 56.8%), belong to SCCmec type IV (n = 205, 92.3%), spa type t032 (n = 160, 72.1%) and harboured seg+sei toxin genes (n = 172, 77.5%). There was significant association between resistance of the aforementioned antibiotics with SCCmec type IV (p < 0.05), t032 (p < 0.001), and seg+sei carriage (p < 0.05). Results from this second MRSA surveillance revealed the occurrence of clonal replacement in HCTM during an interval of not more than 8 years. Investigation of the corresponding phenotype changes in this new dominant MRSA clone is currently on-going.

Genomic analysis revealed a novel genotype of methicillin-susceptible Staphylococcus aureus isolated from a fatal sepsis case in dengue patient

Staphylococcus aureus (S. aureus) is an opportunistic pathogen capable of causing serious health implications in susceptible individuals once it invades the host’s protective barriers. Methicillin-susceptible S. aureus (MSSA) often receives lesser attention although it has been frequently associated with serious infections in human. We aim to investigate the genomic features of a highly virulent yet pan susceptible MSSA strain (coded as HS-MSSA) which caused concurrent bacteraemia in a dengue patient, ultimately resulted in sepsis death of the patient. Whole genome sequence analysis was performed. The draft genome of HS-MSSA is approximately 2.78 Mb (GC content = 32.7%) comprising of 2637 predicted coding sequences. In silico genotyping of the HS-MSSA strain revealed a novel combined genotype (t091/ST2990). The HS-MSSA carries a SaPIn1-like pathogenicity island that harbours the staphylococcal enterotoxin and enterotoxin-like genes (sec3 and selL). The strain-specific β-lactamase (blaZ)-bearing plasmid region was identified in HS-MSSA. Core genome phylogeny showed that the HS-MSSA strain shared a common ancestry with the European MRSA clone. We report herein the genomic features of an MSSA lineage with novel genotype previously not reported elsewhere.

Prevalence of nasal carriers of methicillin-resistant Staphylococcus aureus in primary health care units in Brazil

Nasal carriage of Staphylococcus aureus by healthcare workers is of great clinical importance as it facilitates the contamination of medical devices and cross-transmission. However, studies regarding the epidemiology and dissemination of S. aureus and Methicillin-resistant S. aureus (MRSA) within the Primary Health Care in Brazil are scarce. The current study aimed to detect and characterize S. aureus and MRSA strains from the nasal cavities of 63 healthcare working in primary health care units in order to determine the prevalence of S. aureus and MRSA, biofilm formation and resistance profile of these isolates. PCR reactions were performed for detecting mecA, icaA and icaD genes. The phenotypic antimicrobial susceptibility was assessed by the disk diffusion method and biofilm formation by the Congo Red Agar (CRA) method. The MRSA isolates were typed for the Staphylococcal Cassette Chromosome mec (SCCmec). The prevalence of nasal carriage of S. aureus was 74.6%, of which 72.3% were MRSA carrying SCCmec type I (24.4%), III (34.1%), IV (36.6%). Two (4.9%) isolates presented a non-typeable cassette by the performed technique. The antimicrobial susceptibility evaluation evidenced penicillin resistance in 66.1% of S. aureus, erythromycin resistance in 49.2%, while 37.3% were resistant to oxacillin, 28.8% to cefoxitin, 5.1% to levofloxacin and 5.1% to clindamycin. All isolates were biofilm producers and 96.6% of the strains contained the ica biofilm-forming genes (icaA and/or icaD). We have demonstrated a high prevalence of S. aureus and MRSA carriage among health care working in Primary Health Care units, the presence of SCCmec types I, III and IV, in addition to their high ability to form biofilm, factors that possibly contribute to the dissemination and persistence of these pathogens within the primary care services. These observations highlight the importance of broadening the perspective of Health Care-Associated Infections prevention, including all health care levels, which are currently little explored. In addition, the dynamics and resistance mechanisms of S. aureus transmission still need to be further clarified to enable the implementation of more effective prevention measures.

Methicillin-resistant Staphylococcus aureus bacteraemia, 2003-2015: Comparative evaluation of changing trends in molecular epidemiology and clinical outcomes of infections

Methicillin-resistant Staphylococcus aureus (MRSA) is a prominent pathogen causing invasive infections such as bacteraemia. The continued excessive use of antibiotics to treat MRSA infections has resulted in the evolution of antimicrobial resistant of S. aureus. This study aims to perform a comparative evaluation of changing trends in molecular epidemiology of MRSA and clinical characteristics of patients. This study shows that ST22-MRSA-IV has gradually replaced ST239-MRSA-III as the predominant MRSA clone in the tertiary teaching hospital studied. Independent predictors of mortality among patients included devices in situ at the time of infection, pre-exposure to macrolides, catheter-related bloodstream infection and mono-microbial infection. Hence, our study affirmed community-associated MRSA, which was previously identified from individuals without any exposure to healthcare settings, has now emerged in healthcare settings, causing healthcare-associated MRSA infections.

Global Evolution of Pathogenic Bacteria With Extensive Use of Fluoroquinolone Agents

It is well-established that the spread of many multidrug-resistant (MDR) bacteria is predominantly clonal. Interestingly the international clones/sequence types (STs) of most pathogens emerged and disseminated during the last three decades. Strong experimental evidence from multiple laboratories indicate that diverse fitness cost associated with high-level resistance to fluoroquinolones contributed to the selection and promotion of the international clones/STs of hospital-associated methicillin-resistant Staphylococcus aureus (HA-MRSA), extended-spectrum β-lactamase-(ESBL)-producing Klebsiella pneumoniae, ESBL-producing Escherichia coli and Clostridioides difficile. The overwhelming part of the literature investigating the epidemiology of the pathogens as a function of fluoroquinolone use remain in concordence with these findings. Moreover, recent in vitro data clearly show the potential of fluoroquinolone exposure to shape the clonal evolution of Salmonella Enteritidis. The success of the international clones/STs in all these species was linked to the strains' unique ability to evolve multiple energetically beneficial gyrase and topoisomerase IV mutations conferring high-level resistance to fluorquinolones and concomittantly permitting the acquisition of an extra resistance gene load without evoking appreciable fitness cost. Furthermore, by analyzing the clonality of multiple species, the review highlights, that in environments under high antibiotic exposure virulence factors play only a subsidiary role in the clonal dynamics of bacteria relative to multidrug-resistance coupled with favorable fitness (greater speed of replication). Though other groups of antibiotics should also be involved in selecting clones of bacterial pathogens the role of fluoroquinolones due to their peculiar fitness effect remains unique. It is suggested that probably no bacteria remain immune to the influence of fluoroquinolones in shaping their evolutionary dynamics. Consequently a more judicious use of fluoroquinolones, attuned to the proportion of international clone/ST isolates among local pathogens, would not only decrease resistance rates against this group of antibiotics but should also ameliorate the overall antibiotic resistance landscape.

Molecular Characterization of Methicillin-Susceptible and -Resistant Staphylococcus aureus Harboring Panton-Valentine Leukocidin-Encoding Bacteriophages in a Tertiary Care Hospital in Myanmar

Panton-Valentine leukocidin (PVL) is a pore-forming toxin encoded by genes on bacteriophages distributed to Staphylococcus aureus, associated with its increased virulence to humans. In this study, molecular epidemiological characteristics were investigated for 239 clinical isolates of S. aureus collected in a tertiary care hospital in Yangon, Myanmar, particularly with regard to methicillin resistance and PVL genes. Methicillin-resistant S. aureus (MRSA) accounted for 13.8% (33/239) and possessed mostly types IV- and V-SCCmec, while types III- and IX-SCCmec were identified in a few isolates. PVL genes were detected in 66.7% and 28.6% in MRSA and methicillin-susceptible S. aureus (MSSA), respectively. Among PVL-positive MRSA, ST772/SCCmec-V isolates (i.e., Bengal Bay clone) were predominant (73%, 16/22), and harbored PVL gene-encoding bacteriophage ΦSa119. Furthermore, two ST8-MRSA-SCCmec-IVa isolates harbored type-I arginine catabolic mobile element and ΦSa2usa: these isolates were considered the USA300 clone first identified in Myanmar. ΦPVL was the most frequent PVL phage among MSSA (56%, 33/59), and distributed to various genotypes, with ST88 and ST121 being dominant. In contrast, ΦSa2usa and ΦSa119 were also detected in MSSA with genotypes other than ST8 or ST772, suggesting the spread of these PVL phages to MSSA. The present study revealed potentially high prevalence of PVL phages among diverse clones of MRSA and MSSA in Myanmar.

Tigecycline and inducible clindamycin resistance in clinical isolates of methicillin-resistant Staphylococcus aureus from Terengganu, Malaysia

The spread of multidrug-resistant Staphylococcus aureus is a public health concern. The inducible macrolide-lincosamide-streptogrammin B (iMLS_B ) phenotype (or inducible clindamycin resistance) is associated with false clindamycin susceptibility in routine laboratory testing and may lead to treatment failure. Tigecycline resistance remains rare in S. aureus worldwide. This study aims to determine the antimicrobial susceptibility profiles of clinical isolates of S. aureus obtained from the main tertiary hospital in Terengganu state, Malaysia, from July 2016 to June 2017. The antimicrobial susceptibilities of 90 methicillin-resistant S. aureus (MRSA) and 109 methicillin-susceptible S. aureus (MSSA) isolates were determined by disc diffusion with the iMLS_B phenotype determined by D-test. Multidrug resistance (MDR) and the iMLS_B phenotype were more prevalent in MRSA (84.4 and 46.7  %, respectively) compared to MSSA isolates. All five tigecycline-resistant isolates were MRSA. The high incidence of MDR and the iMLS_B phenotype and the emergence of tigecycline resistance in the Terengganu S. aureus isolates warrants continuous vigilance.

Staphylococcus aureus Infections in Malaysia: A Review of Antimicrobial Resistance and Characteristics of the Clinical Isolates, 1990-2017

Staphylococcus aureus is an important nosocomial pathogen and its multidrug resistant strains, particularly methicillin-resistant S. aureus (MRSA), poses a serious threat to public health due to its limited therapeutic options. The increasing MRSA resistance towards vancomycin, which is the current drug of last resort, gives a great challenge to the treatment and management of MRSA infections. While vancomycin resistance among Malaysian MRSA isolates has yet to be documented, a case of vancomycin resistant S. aureus has been reported in our neighboring country, Indonesia. In this review, we present the antimicrobial resistance profiles of S. aureus clinical isolates in Malaysia with data obtained from the Malaysian National Surveillance on Antimicrobial Resistance (NSAR) reports as well as various peer-reviewed published records spanning a period of nearly three decades (1990-2017). We also review the clonal types and characteristics of Malaysian S. aureus isolates, where hospital-associated (HA) MRSA isolates tend to carry staphylococcal cassette chromosome mec (SCCmec) type III and were of sequence type (ST)239, whereas community-associated (CA) isolates are mostly SCCmec type IV/V and ST30. More comprehensive surveillance data that include molecular epidemiological data would enable further in-depth understanding of Malaysian S. aureus isolates.

Predominance of ST22-MRSA-IV Clone and Emergence of Clones for Methicillin-Resistant Staphylococcus aureus Clinical Isolates Collected from a Tertiary Teaching Hospital Over a Two-Year Period

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most common nosocomial pathogens, causing mild to severe infections. This study aimed to determine the genotypic and phenotypic characteristics of clinical MRSA isolates collected from a teaching hospital from 2014 - 2015. These isolates were genotyped by multilocus sequence typing, staphylococcal cassette chromosomal mec (SCCmec) typing, virulence genes detection, and pulsed-field gel electrophoresis; they were phenotyped based on their antibiotics susceptibility profiles. The most prevalent sequence type was ST22. ST3547 was identified from a blood isolate from 2015. Three SCCmec types (III in 26.26%, IV in 70.71%, and V in 3.03% isolates) were detected. Agr type I, II, and III were also detected among the isolates. The most prevalent virulence genes found were hemolysin (100%) and intracellular adhesion (91.9%). At least one staphylococcal enterotoxin was detected in 83 (83.8%) isolates. All the isolates were susceptible to vancomycin (minimum inhibitory concentration ≤ 2 μg/mL). Statistical analysis revealed a significant increase in hypertension (p = 0.035), dyslipidemia and obesity (p = 0.046), and previous exposure to any quinolone (p = 0.010) cases over the two-year period. The emergence and circulation of community-associated MRSA variants were observed in our hospital.

Nasal colonisation, antimicrobial susceptibility and genotypic pattern of Staphylococcus aureus among agricultural biotechnology students in Besut, Terengganu, east coast of Malaysia

BACKGROUND

This study aimed to profile the antimicrobial susceptibility and presence of resistance and virulence genes of methicillin-susceptible Staphylococcus aureus (MSSA) and MRSA nasal carriage, by means of genotypic analyses, in students of a tertiary institution in the state of Terengganu, east coast of Malaysia.

METHODS

A total of 370 agricultural biotechnology students from Universiti Sultan Zainal Abidin in Besut, Terengganu, were enrolled in this study. Antimicrobial susceptibility profiles were evaluated by standard methods. PCR detection of resistance and virulence genes was performed on S. aureus that were methicillin-resistant, macrolide-lincosamide-streptogramin B (MLS_B )-positive phenotype and/or positive for the leukocidin (pvl) gene followed by staphylococcal cassette chromosome mec (SCCmec), staphylococcal protein A (spa) and accessory gene regulator (agr) typing.

RESULTS

One hundred and nineteen of 370 students carried S. aureus (32%); 18 of the isolates were MRSA (15%). Erythromycin resistance was detected in 20% (24/119) of which 15% (18/119) were MRSA and 5% (6/119) MSSA. Among the 24 erythromycin-resistant isolates, D-test was positive in 29% (7/24) displaying inducible MLS_B , whereas the remaining 71% (17/24) showed constitutive MLS_B phenotypes. Nine (7.6%) of 119 isolates were pvl positive: 44% MRSA (4/9) and 56% MSSA (5/9). Staphylococcal surface protein sasX gene was present in 92% of MRSA and 8% of MSSA isolates. The majority of MRSA isolates were agr type I (15/18; 83%). Five spa types identified with spa t037 were predominant, followed by spa types (t304 and t8696) as newly reported Malaysian MRSA in a community setting.

CONCLUSION

The presence of MRSA with SCCmec of hospital-associated features and globally recognised spa types in community setting is worrisome. Furthermore, the presence of MLS_B strains among multidrug-resistant (MDR) S. aureus with sasX as well as pvl-positive isolates highlights the potential risk of a community setting in facilitating the dissemination of both virulence and resistance determinants.

Prevalence of methicillin-resistant Staphylococcus aureus (MRSA) infection and the molecular characteristics of MRSA bacteraemia over a two-year period in a tertiary teaching hospital in Malaysia

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) is an established pathogen that causes hospital- and community-acquired infections worldwide. The prevalence rate of MRSA infections were reported to be the highest in Asia. As there is limited epidemiological study being done in Malaysia, this study aimed to determine the prevalence of MRSA infection and the molecular characteristics of MRSA bacteraemia.

METHODS

Two hundred and nine MRSA strains from year 2011 to 2012 were collected from a tertiary teaching hospital in Malaysia. The strains were characterized by antimicrobial susceptibility testing, staphylococcal cassette chromosome mec (SCCmec) typing, detection of Panton-Valentine leukocidin (PVL) gene, multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE). Patient's demographic and clinical data were collected and correlated with molecular data by statistical analysis.

RESULTS

Male gender and patient >50 years of age (p < 0.0001) were significantly associated with the increased risk of MRSA acquisition. Fifty-nine percent of MRSA strains were HA-MRSA that carried SCCmec type II, III, IV and V while 31% were CA-MRSA strains with SCCmec III, IV and V. The prevalence of PVL gene among 2011 MRSA strains was 5.3% and no PVL gene was detected in 2012 MRSA strains. All of the strains were sensitive to vancomycin. However, vancomycin MIC creep phenomenon was demonstrated by the increased number of MRSA strains with MIC ≥1.5 μg/mL (p = 0.008) between 2011 and 2012. Skin disease (p = 0.034) and SCCmec type III (p = 0.0001) were found to be significantly associated with high vancomycin MIC. Forty-four percent of MRSA strains from blood, were further subtyped by MLST and PFGE. Most of the bacteraemia cases were primary bacteraemia and the common comorbidities were diabetes, hypertension and chronic kidney disease. The predominant pulsotype was pulsotype C exhibited by SCCmec III-ST239. This is a first study in Malaysia that reported the occurrence of MRSA clones such as SCCmec V-ST5, untypeable-ST508, SCCmec IV-ST1 and SCCmec IV-ST1137.

CONCLUSIONS

SCCmec type III remained predominant among the MRSA strains in this hospital. The occurrence of SCCmec IV and V among hospital strains and the presence of SCCmec III in CA-MRSA strains are increasing. MRSA strains causing bacteraemia over the two-year study period were found to be genetically diverse.

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.

Antimicrobial resistance profiling and molecular typing of methicillin-resistant Staphylococcus aureus isolated from a Malaysian teaching hospital

The annual prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in Malaysia has been estimated to be 30 % to 40 % of all S. aureus infections. Nevertheless, data on the antimicrobial resistance and genetic diversity of Malaysian MRSAs remain few. In 2009, we collected 318 MRSA strains from various wards of our teaching hospital located in Kuala Lumpur, the capital city of Malaysia, and performed antimicrobial susceptibility testing on these strains. The strains were then molecularly characterized via staphylococcal cassette chromosome (SCC) mec and virulence gene (cna, sea, seb, sec, sed, see, seg, seh, sei, eta, etb, Panton-Valentine leukocidin and toxic shock syndrome toxin-1) typing; a subset of 49 strains isolated from the intensive care unit was also typed using PFGE. Most strains were found to be resistant to ciprofloxacin (92.5 %), erythromycin (93.4 %) and gentamicin (86.8 %). The majority (72.0 %) of strains were found to harbour SCCmec type III-SCCmercury with the presence of ccrC, and carried the sea+cna gene combination (49.3 %), with cna as the most prevalent virulence gene (94.0 %) detected. We identified four PFGE clusters, with pulsotype C (n=19) as the dominant example in the intensive care unit, where this pulsotype was found to be associated with carriage of SCCmec type III and the sea gene (P=0.05 and P=0.02, respectively). In summary, the dominant MRSA circulating in our hospital in 2009 was a clone that was ciprofloxacin, erythromycin and gentamicin resistant, carried SCCmec type III-SCCmercury with ccrC and also harboured the sea+cna virulence genes. This clone also appears to be the dominant MRSA circulating in major hospitals in Kuala Lumpur.

Dissimilar Fitness Associated with Resistance to Fluoroquinolones Influences Clonal Dynamics of Various Multiresistant Bacteria

Fitness cost associated with resistance to fluoroquinolones was recently shown to vary across clones of methicillin-resistant Staphylococcus aureus and extended-spectrum β-lactamase-producing Klebsiella pneumoniae. The resulting dissimilar fitness should have influenced the clonal dynamics and thereby the rates of resistance for these pathogens. Moreover, a similar mechanism was recently proposed for the emergence of the H30 and H30R lineages of ESBL-producing E. coli and the major international clone (ribotype 027) of Clostridium difficile. Furthermore, several additional international clones of various multiresistant bacteria are suspect to have been selected by an analogous process. An ability to develop favorable mutations in the gyrase and topoisomerase IV genes seems to be a prerequisite for pathogens to retain fitness while showing high-level resistance to fluoroquinolones. Since, the consumption of other "non-fluoroquinolone" groups of antibiotics have also contributed to the rise in resistance rates a more judicious use of antibiotics in general and of fluoroquinolones in particular could ameliorate the international resistance situation.

Molecular Markers of Antimicrobial Resistance in Methicillin-Resistant Staphylococcus aureus SCCmec IV Presenting Different Genetic Backgrounds

Methicillin-resistant Staphylococcus aureus (MRSA) carrying SCCmec type IV has emerged in hospitals worldwide. The aim of this study was to evaluate phenotypic and molecular characteristics of antimicrobial resistance in MRSA SCCmec IV isolates, presenting different genetic backgrounds, isolated from hospitals in Rio de Janeiro. The antimicrobial resistance of 128 S. aureus type IV isolates from 11 hospitals was characterized by the disk diffusion test and minimum inhibitory concentration (MIC) test. Mutations in parC gene, which encodes ciprofloxacin resistance, and genes associated with macrolide-lincosamide-streptogramin B (MLS_b) resistance were also investigated. MRSA isolates belonging to USA400/ST1 (60 isolates), USA800/ST5 (40), USA1100/ST30 (13), and other 11 (15) lineages were mainly resistant to erythromycin (68%), ciprofloxacin (56%), and clindamycin (50%). The highest antimicrobial resistance rates were found among USA400 isolates (p < 0.05). The majority of them (90%) carried only the erm(C) gene and mainly presented two mutation types in the parC gene. The msr(A) gene was most frequently found among USA800 isolates (p < 0.05). Among MRSA type IV isolates from Rio de Janeiro hospitals, multiresistance, including mutations in parC gene, was associated to the USA400/ST1, while the msr(A) gene was associated with USA800/ST5 isolates, highlighting that these lineages could have more potential to persist in a hospital environment.

Molecular epidemiology of Methicillin-resistant Staphylococcus aureus in Africa: a systematic review

Methicillin-resistant Staphylococcus aureus (MRSA) infections are a serious global problem, with considerable impact on patients and substantial health care costs. This systematic review provides an overview on the clonal diversity of MRSA, as well as the prevalence of Panton-Valentine leukocidin (PVL)-positive MRSA in Africa. A search on the molecular characterization of MRSA in Africa was conducted by two authors using predefined terms. We screened for articles published in English and French through to October 2014 from five electronic databases. A total of 57 eligible studies were identified. Thirty-four reports from 15 countries provided adequate genotyping data. CC5 is the predominant clonal complex in the healthcare setting in Africa. The hospital-associated MRSA ST239/ST241-III [3A] was identified in nine African countries. This clone was also described with SCCmec type IV [2B] in Algeria and Nigeria, and type V [5C] in Niger. In Africa, the European ST80-IV [2B] clone was limited to Algeria, Egypt and Tunisia. The clonal types ST22-IV [2B], ST36-II [2A], and ST612-IV [2B] were only reported in South Africa. No clear distinctions were observed between MRSA responsible for hospital and community infections. The community clones ST8-IV [2B] and ST88-IV [2B] were reported both in the hospital and community settings in Angola, Cameroon, Gabon, Ghana, Madagascar, Nigeria, and São Tomé and Príncipe. The proportion of PVL-positive MRSA carriage and/or infections ranged from 0.3 to 100% in humans. A number of pandemic clones were identified in Africa. Moreover, some MRSA clones are limited to specific countries or regions. We strongly advocate for more surveillance studies on MRSA in Africa.

New epidemiology of Staphylococcus aureus infection in Asia

Not only is Asia the most populous region in the world, but inappropriate therapy, including self-medication with over-the-counter antimicrobial agents, is a common response to infectious diseases. The high antibiotic selective pressure among the overcrowded inhabitants creates an environment that is suitable for the rapid development and efficient spread of numerous multidrug-resistant pathogens. Indeed, Asia is among the regions with the highest prevalence rates of healthcare-associated methicillin-resistant Staphylococcus aureus (HA-MRSA) and community-associated methicillin-resistant S. aureus (CA-MRSA) in the world. Most hospitals in Asia are endemic for multidrug-resistant methicillin-resistant S. aureus (MRSA), with an estimated proportion from 28% (in Hong Kong and Indonesia) to >70% (in Korea) among all clinical S. aureus isolates in the early 2010s. Isolates with reduced susceptibility or a high level of resistance to glycopeptides have also been increasingly identified in the past few years. In contrast, the proportion of MRSA among community-associated S. aureus infections in Asian countries varies markedly, from <5% to >35%. Two pandemic HA-MRSA clones, namely multilocus sequence type (ST) 239 and ST5, are disseminated internationally in Asia, whereas the molecular epidemiology of CA-MRSA in Asia is characterized by clonal heterogeneity, similar to that in Europe. In this review, the epidemiology of S. aureus in both healthcare facilities and communities in Asia is addressed, with an emphasis on the prevalence, clonal structure and antibiotic resistant profiles of the MRSA strains. The novel MRSA strains from livestock animals have been considered to constitute a public health threat in western countries. The emerging livestock-associated MRSA strains in Asia are also included in this review.

Mutations in rpoB and fusA cause resistance to rifampicin and fusidic acid in methicillin-resistant Staphylococcus aureus strains from a tertiary hospital in Malaysia

BACKGROUND

The prevalence of resistance to rifampicin and fusidic acid among Malaysian strains of methicillin-resistant Staphylococcus aureus (MRSA) is increasing. This study aimed to determine the mechanisms of rifampicin and fusidic acid resistance and the genetic diversity of MRSA strains from a Malaysian tertiary hospital.

METHODS

Minimum inhibitory concentrations (MIC) for 21 MRSA strains were determined by agar dilution test and Etest. The resistance genes, staphylococcal chromosome cassette mec (SCCmec) types, multilocus-sequence typing (MLST) types and spa types, were determined by PCR and DNA sequencing.

RESULTS

MIC for rifampicin and fusidic acid resistance ranged from <1 to 8 µg/ml and from <1 to 256 µg/ml, respectively. A double mutation (484Arg/His and 517Glu/Gln) in rpoB causes high rifampicin resistance while a mutational change (461Leu/Lys) in fusA was observed in seven strains highly resistant to fusidic acid. Five of the seven were also resistant to rifampicin (MIC 8 µg/ml) and carried a mutated rpoB gene (484Arg/His). No other acquired fusidic acid resistance gene (fusB, fusC or fusD) was detected. Most (14/21) of the strains belonged to clone ST239-III-t037. Three belonged to ST22-IV-t1378 and the remaining four to ST239-III-t2029, ST239-III-t421, ST1178-IV-t1107 and ST241-III-t363, respectively.

CONCLUSIONS

The study showed that both rifampicin and fusidic acid resistance was associated with mutational change in rpoB and fusA, respectively. All rifampicin-resistant strains were from the same clone ST239-III-t037 whereas strains resistant to fusidic acid were genetically more diverse.