Asymptomatic carriers of toxigenic Staphylococcus aureus are potential source of diseases, including food poisoning. Toxigenic potential and genetic traits of colonizing S. aureus were investigated for 563 healthy food handlers in Myanmar. Carriage of S. aureus was found in 110 individuals (19.5%), and a total of 144 S. aureus isolates were recovered from nasal cavities (110 isolates) and hands (34 isolates). Panton-Valentine leucocidin genes (pvl) were detected in 18 isolates (12.5%), among which 11 isolates were classified into coa-VIa, agr type III, and ST1930 (CC96) that had been also detected in pvl-positive clinical isolates in Myanmar. A pvl-positive, ST2250 nasal isolate was identified as S. argenteus, a novel coagulase-positive staphylococcus species. Toxic shock syndrome toxin-1 (TSST-1) gene was detected in five pvl-negative isolates. All of the 144 isolates harbored at least one of the 21 enterotoxin(-like) gene(s). The most prevalent enterotoxin(-like) gene was selw (98%), followed by selx (97%), sei (28%), sely (28%), sem (26%), sel (24%), and sea and sec (22% each). Considerable genetic diversity with five groups was detected for selw. The present study revealed the relatively high rate of pvl, as well as the wide distribution of enterotoxin(-like) genes among colonizing S. aureus in Myanmar.

The increasing trend of Escherichia coli producing extended-spectrum beta-lactamases (ESBLs) and carbapenemases is a global public health concern. In this study, prevalence and molecular characteristics of E. coli harboring ESBL and carbapenemase genes were investigated for 426 isolates derived from various clinical specimens in a teaching hospital in Yangon, Myanmar, for the 1-year period beginning January 2016. A total of 157 isolates (36.9%) were ESBL producers and harbored CTX-M-1 group genes (146 isolates; bla _CTX-M-15 , bla _CTX-M55 ) or CTX-M-9 group genes (11 isolates; bla _CTX-M-14 , bla _CTX-M-27 ). Carbapenem resistance was detected in 35 isolates (8.2%), among which 26 isolates had carbapenemase genes encoding NDM-1 (2 isolates), NDM-4 (6 isolates), NDM-5 (14 isolates), NDM-7 (3 isolates), and OXA-181 (2 isolates). bla _NDM-5 was identified in phylogenetic groups A, B1, and D isolates belonging to various genotypes (ST101, ST354, ST405, ST410, ST1196) associated with bla _TEM-1 , bla _CTX-M-15 , bla _OXA-181 , bla _CMY-2 , bla _CMY-6 , bla _CMY-42 , qnrB , qnrS , or aac6′-Ib-cr . While two isolates with bla _OXA-181 belonged to phylogenetic group A-ST410, one isolate had also bla _NDM-5 , as well as bla _CTX-M-15 and bla _CMY-2 , and the other harbored bla _CMY-42 and aac6′-Ib-cr , showing different resistance patterns. Phylogenetic group B2 isolates examined were classified into mostly ST131 and had solely bla _CTX-M-15 or bla _CTX-M-27 , harboring more virulence factors than other phylogenetic groups. The present study revealed high prevalence of ESBL genes represented by bla _CTX-M-15 and dominance of bla _NDM-5 among NDM genes, disseminating to various E. coli clones. Notably, carbapenemase gene encoding OXA-181 was first identified in Myanmar, suggesting its spread together with NDM genes.

Staphylococcus aureus produces virulence factors, including various exotoxins and adhesins, which are associated with a variety of symptoms caused by its infections. In the present study, the prevalence of these virulence factors was analyzed for 23 S. aureus strains isolated from wound infections in hospitals, nasal swabs, or vomit from patients and cooks in a food poisoning case and from healthy adults in Yangon, Myanmar. Among these strains, five were methicillin-resistant S. aureus (MRSA) derived from pus (four strains, SCC mec III, ST239) and a healthy adult (one strain, SCC mec -IVa, ST5). The Panton-Valentine leukocidine (PVL) gene was detected in five methicillin-susceptible S. aureus (MSSA) clinical strains belonging to ST121 (CC121). The MRSA clinical strains had only a few or no staphylococcal enterotoxin (SE) genes, whereas PVL-positive MSSA and an MRSA strain from a healthy adult possessed an enterotoxin gene cluster ( seg , sei , sem , sen , seo , and selu ). Strains from the food poisoning case had either SE genes or only etd and edin-B . Adhesin genes, which are associated with binding to fibronectin, fibrinogen, and elastin, were detected in all the MRSA and most of the MSSA strains examined. However, the bone sialoprotein-binding protein gene ( bbp ) and the variant form of the elastin-binding protein gene ( ebpS-v ) with an internal 180 bp deletion were identified only in the MSSA strains harboring the PVL gene. These findings suggest that those genetic traits are characteristic of PVL-positive ST121 S. aureus strains in Myanmar.

Purpose. Staphylococcus argenteus is a novel emerging species of coagulase-positive staphylococcus that is genetically closely related to Staphylococcus aureus. To elucidate the molecular differences in the virulence factors (staphylocoagulase, protein A, alpha-haemolysin, enterotoxin-like toxin and staphylokinase) between these staphylococcal species, S. argenteus that had recently been isolated in Myanmar (five nasal isolates and four clinical isolates) were analysed. Methodology. The nucleotide sequences of the virulence factors were determined by PCR and direct sequencing, followed by phylogenetic analysis by mega6 and multiple alignment by clustalw using the published sequence data for S. aureus and S. argenteus. Results. Six S. argenteus isolates belonged to MLST sequence type (ST) 2250, while others belonged to ST4625, ST2198 and ST2854. The novel staphylocoagulase (coa) genotype XIV and the novel coa-XI subtype (XId) were identified in an ST2198 isolate and all other isolates, respectively. Among the S. argenteus isolates, the protein A and alpha-haemolysin genes showed high sequence identity (96–98 % and >99 %, respectively), while lower identity was observed between S. argenteus and S. aureus (88–91 % and 86 %, respectively), with both species showing phylogenetically distinct clusters. Similar findings were found for the staphylococcal enterotoxin (SE)-like toxin genes selw, selx and sely. In contrast, the staphylokinase genes were almost identical between these two species. All of the coa-XId isolates had a CRISPR/Cas locus at the site of orfX without having SCCmec, whereas an ST2198 isolate lacked this locus. Conclusion.The primary virulence factors (staphylocoagulase, protein A andalpha-haemolysin) as well as the SE-like toxins of S. argenteus were genetically discriminated from those of S. aureus, revealing the presence of the novel coa-type/subtype (coa-IXd, XIV) in S. argenteus.

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-SCC mec , while types III- and IX-SCC mec 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/SCC mec -V isolates ( i.e. , Bengal Bay clone) were predominant (73%, 16/22), and harbored PVL gene-encoding bacteriophage ΦSa119. Furthermore, two ST8-MRSA-SCC mec -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.

Antimicrobial resistance (AMR) is a concern in medical care for children who have high burden of infectious diseases. We investigated the prevalence of bacterial species and their susceptibility to antimicrobials of 1019 clinical isolates from pediatric patients in a tertiary-care hospital in Yangon, Myanmar for one-year period (2020). The most frequently recovered species was Escherichia coli, followed by Klebsiella pneumoniae and Staphylococcus aureus, all of which accounted for 43% of clinical isolates, while 25% of isolates comprised non-fermenter, including Pseudomonas sp. and Acinetobacter sp. Phenotypically determined ESBL (extended-spectrum beta-lactamase)-positive rates in E. coli, K. pneumoniae, and Enterobacter sp. were 82%, 88%, and 65%, respectively. High rates of multiple drug resistance were noted for E. coli (84%), K. pneumoniae (81%), and Acinetobacter sp. (65%), associated with carbapenem resistance in 48%, 42%, and 59% of isolates, respectively. In contrast, S. aureus isolates exhibited low resistance rates (<30%) to most of antimicrobials, with 22% being resistant to oxacillin/cefoxitin. Fluoroquinolone resistance was found in most of bacterial species with different prevalence rates. The present study revealed the current status on prevalence of bacterial species causing infections in pediatric patients in Myanmar, highlighting the significance to monitor AMR among children.