Drug resistance and genetic characteristics of clinical isolates of staphylococci in Myanmar: high prevalence of PVL among methicillin-susceptible Staphylococcus aureus belonging to various sequence types

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.

Bacterial Species and Antimicrobial Resistance of Clinical Isolates from Pediatric Patients in Yangon, Myanmar, 2020

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.

Mapping of the fibrinogen-binding site on the staphylocoagulase C-terminal repeat region

Fibrin (Fbn) deposits are a hallmark of staphylocoagulase (SC)-positive endocarditis. Binding of the N terminus of Staphylococcus aureus SC to host prothrombin triggers formation of an active SC·prothrombin∗ complex that cleaves host fibrinogen to Fbn. In addition, the C-terminal domain of the prototypical SC contains one pseudorepeat (PR) and seven repeats (R1 → R7) that bind fibrinogen/Fbn fragment D (frag D) by a mechanism that is unclear. Here, we define affinities and stoichiometries of frag D binding to C-terminal SC constructs, using fluorescence equilibrium binding, NMR titration, alanine scanning, and native PAGE. We found that constructs containing the PR and single repeats bound frag D with K_D ∼50 to 130 nM and a 1:1 stoichiometry, indicating a conserved binding site bridging the PR and each repeat. NMR titration of PR-R7 with frag D revealed that residues 22 to 49, bridging PR and R7, constituted the minimal peptide (MP) for binding, corroborated by alanine scanning, and binding of labeled MP to frag D. MP alignment with the PR-R and inter-repeat junctions identified critical conserved residues. Full-length PR-(R1 → R7) bound frag D with K_D ∼20 nM and a stoichiometry of 1:5, whereas constructs containing the PR and various three repeats competed with PR-(R1 → R7) for frag D binding, with a 1:3 stoichiometry. These findings are consistent with binding at PR-R and R-R junctions with modest inter-repeat sequence variability. CD of PR-R7 and PR-(R1 → R7) suggested a disordered flexible structure, allowing binding of multiple fibrin(ogen) molecules. Taken together, these results provide insights into pathogen localization on host fibrin networks.

Clonal Diversity and Molecular Characteristics of Methicillin-Susceptible and -Resistant Staphylococcus aureus from Pediatric Patients in Myanmar

The spread of multidrug-resistant and virulent Staphylococcus aureus among children is a public health concern, but the actual conditions in Myanmar have not been characterized. In this study, a total of 244 clinical isolates of S. aureus collected from pediatric patients in Yangon Children's Hospital during a 1-year period were analyzed for their drug resistance and genetic features. Methicillin-resistant S. aureus (MRSA) accounted for 19.7% of isolates associated with staphylococcal cassette chromosome mec (SCCmec) type III, IV, or V. Panton-Valentine leukocidin (PVL) genes were detected in 61.5% of all isolates, with a significantly higher prevalence in methicillin-susceptible S. aureus (MSSA; 67.9%) than in MRSA (35.4%) isolates. Sequence type (ST) 239/SCCmec-III was the most common MRSA clone lacking PVL genes, while PVL-positive MRSA belonged to mostly ST361/SCCmec-V and ST772/SCCmec-V. Among MSSA isolates, ST121, ST2990, ST88, and ST1930 were dominant, harboring mostly PVL genes. ST239 MRSA isolates exhibited the highest resistance rates to antimicrobials, and quinolone resistance was found in the dominant MRSA clones (ST239, ST361, and ST772) and some MSSA lineages. The present study revealed the prevalence and clonal diversity of MRSA/MSSA in children in Myanmar in relation to drug resistance and virulence determinants.

Wounds, Antimicrobial Resistance and Challenges of Implementing a Surveillance System in Myanmar: A Mixed-Methods Study

Wound infections with drug-resistant bacteria lead to higher mortality and morbidity and increased healthcare costs. We aimed to describe the spectrum of bacterial pathogens, isolated from wound cultures in Yangon General Hospital in 2018, and their antimicrobial resistance (AMR) patterns and to understand the challenges in implementing an AMR surveillance system in Myanmar. We conducted a concurrent mixed-methods study involving analysis of surveillance data and in-depth interviews with nine key personnel involved in AMR surveillance. Of 1418 wound specimens processed, 822 (58%) were culture-positive. The most common Gram-positive bacteria were coagulase-negative staphylococci (23.3%) and Staphylococcus aureus (15.1%). Among Gram-negative bacteria, Escherichia coli (12.5%) and Pseudomonas aeruginosa (10.1%) were common. Staphylococcus aureus isolates were resistant to penicillin (98%), oxacillin (70%) and tetracycline (66%). Escherichia coli showed resistance to ampicillin (98%). Lack of dedicated and trained staff (microbiologist, technician, data entry operator), lack of computers at sentinel sites and non-uniform and non-standardized data capture formats were the major challenges in implementing AMR surveillance. These challenges need to be addressed urgently. We also recommend periodic analysis and sharing of antibiograms at every hospital to inform the treatment regimens used in wound management.

High Prevalence of Methicillin-Resistant Staphylococcus aureus among Healthcare Facilities and Its Related Factors in Myanmar (2018-2019)

BACKGROUND

Antimicrobial resistance (AMR) is a growing global health problem. Staphylococcus aureus (SA) is a common bacterium associated with a variety of community and hospital infections. Methicillin-resistant Staphylococcus aureus (MRSA) accounts for most SA related morbidity and mortality. In this study, we determined the prevalence and factors associated with SA and MRSA in Myanmar.

METHODS

We collected the data retrospectively by reviewing an electronic register containing the results of bacterial culture and antibiotic susceptibility testing of biological specimens received from healthcare facilities during 2018-2019.

RESULTS

Of the 37,798 biological specimens with bacterial culture growth, 22% (8244) were Gram-positive. Among the Gram-positive bacteria, 42% (2801) were SA, of which 48% (1331) were judged as MRSA by phenotypic methods. The prevalence of MRSA was higher in the older age groups, in female patients, in urine specimens and specimens received from the intensive care unit and dermatology departments. One site (Site F) had the highest MRSA prevalence of the seven AMR sentinel sites. Most SA isolates were sensitive to vancomycin (90%) by phenotypic methods.

CONCLUSIONS

The high prevalence of MRSA indicates a major public health threat. There is an urgent need to strengthen the AMR surveillance and hospital infection control program in Myanmar.

Characterisation of S. aureus/MRSA CC1153 and review of mobile genetic elements carrying the fusidic acid resistance gene fusC

While many data on molecular epidemiology of MRSA are available for North America, Western Europe and Australia, much less is known on the distribution of MRSA clones elsewhere. Here, we describe a poorly known lineage from the Middle East, CC1153, to which several strains from humans and livestock belong. Isolates were characterised using DNA microarrays and one isolate from the United Arab Emirates was sequenced using Nanopore technology. CC1153 carries agr II and capsule type 5 genes. Enterotoxin genes are rarely present, but PVL is common. Associated spa types include t504, t903 and t13507. PVL-positive CC1153-MSSA were found in Egyptian cattle suffering from mastitis. It was also identified among humans with skin and soft tissue infections in Saudi Arabia, France and Germany. CC1153-MRSA were mainly observed in Arabian Gulf countries. Some isolates presented with a previously unknown SCCmec/SCCfus chimeric element in which a mec B complex was found together with the fusidic acid resistance gene fusC and accompanying genes including ccrA/B-1 recombinase genes. Other isolates carried SCCmec V elements that usually also included fusC. Distribution and emergence of CC1153-MRSA show the necessity of molecular characterization of MRSA that are resistant to fusidic acid. These strains pose a public health threat as they combine resistance to beta-lactams used in hospitals as well as to fusidic acid used in the community. Because of the high prevalence of fusC-positive MRSA in the Middle East, sequences and descriptions of SCC elements harbouring fusC and/or mecA are reviewed. When comparing fusC and its surrounding regions from the CC1153 strain to available published sequences, it became obvious that there are four fusC alleles and five distinct types of fusC gene complexes reminiscent to the mec complexes in SCCmec elements. Likewise, they are associated with different sets of ccrA/B recombinase genes and additional payload that might include entire mec complexes or SCCmec elements.

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.

The Role of Staphylococcus aureus in Mastitis : A Multidisciplinary Working Group Experience

BACKGROUND

Breastfeeding women are at risk of developing mastitis during the lactation period. Staphylococcus aureus has emerged as the community-acquired pathogen responsible for virulence (methicillin resistance and Panton-Valentine leukocidin toxin producing).

RESEARCH AIM

The aim was to compare the microorganisms responsible for mastitis and breast abscesses during breastfeeding.

METHODS

This observational study was conducted with a sample of women (N = 60) admitted to our hospital between 2016 and 2018. Participants affected by mastitis and breast abscess were studied and cared for by a multidisciplinary working group. A diagnostic breast ultrasound identified the pathology.

RESULTS

Twenty-six participants (43.3%) were affected by mastitis and 34 (56.7%) by breast abscess. The most common microorganism identified was Staphylococcus aureus (S. aureus; mastitis, n = 13; abscesses, n = 24). Methicillin resistance was identified in 21 (44.7%) S. aureus strains: 17 (80.9%) cases of abscess and four (19.1%) cases of mastitis. The median number of months of breastfeeding was smaller in the methicillin-resistant S. aureus (MRSA) cases (median = 3, range = 1-20 months) than in the methicillin-sensitive S. aureus (MSSA) cases (median = 6.5, range = 3-21 months). The Panton-Valentine leukocidin toxin gene was detected in 12 (25.5%) cases (MRSA, n = 8, 66.7%; MSSA, n = 4, 33.3%). Hospitalization was required more frequently in MRSA (n = 8, 38%; five Panton-Valentine leukocidin positive) than in MSSA cases (n = 5, 19%; one Panton-Valentine leukocidin positive). Four women out of the eight MRSA cases (50%) that were Panton-Valentine leukocidin positive stopped breastfeeding during mammary pathologies, three (37.5%) participants continued breastfeeding until the follow-up recall, and one case was lost at follow-up.

CONCLUSION

Clinical severity was probably complicated by the presence of the Panton-Valentine leukocidin toxin, which required hospitalization more frequently.

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.

Molecular Epidemiological Characterization of Methicillin-Susceptible and -Resistant Staphylococcus aureus Isolated from Skin and Soft Tissue Infections in Bangladesh

Genetic background and molecular characteristics of Staphylococcus aureus collected from patients with skin and soft tissue infections were studied in the North-Central region of Bangladesh from 2015 to 2016. Among 430 clinical isolates, methicillin-resistant S. aureus (MRSA) accounted for 31% having SCCmec type IV (73%) and V (14%), and belonged mostly to coagulase (coa) genotypes IIa, IIIa, IVb, and XIa, while dominant coa type in methicillin-susceptible S. aureus (MSSA) was IIIa, followed by Va, IIa, and VIa. Panton-Valentine Leukocidin genes (pvl) were detected at higher rate in MSSA (54%) than in MRSA (24%). Based on multilocus sequence typing, pvl-positive MRSA isolates were classified into clonal complex 88 (CC88) (ST88, ST2884, ST4345), CC6 (ST6, ST4350), and CC1 (ST1, ST772), while pvl-negative MRSA into CC5, CC22, CC80, CC121, and CC672. The pvl-negative ST80 MRSA isolates had SCCmec-IVa (agr-III/coa-XIc, etd/edinB-positive, fusB-negative), indicating that they belong to the novel CC80 clade related to the European community-acquired MRSA clone. Among MSSA, genotypes ST121/spa-t645/coa-Va and ST2884 (CC88)/spa-t2393/coa-IIIa were identified in both pvl-positive and negative isolates, and all the ST772 isolates harbored pvl. All the ST121 isolates had a variant of elastin-binding protein gene (ebpS-v) with internal 180-nucleotide deletion. The present study suggested that CC88 (ST88, ST2884) and ST772 are the putative dominant lineages of pvl-positive MRSA/MSSA, while novel CC80 clade is one of the main pvl-negative MRSA lineages distributed endemically in Bangladesh.

Prevalence and Genetic Characteristics of Staphylococcus aureus and Staphylococcus argenteus Isolates Harboring Panton-Valentine Leukocidin, Enterotoxins, and TSST-1 Genes from Food Handlers in Myanmar

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 antimicrobial activity of nanoparticles: present situation and prospects for the future

Nanoparticles (NPs) are increasingly used to target bacteria as an alternative to antibiotics. Nanotechnology may be particularly advantageous in treating bacterial infections. Examples include the utilization of NPs in antibacterial coatings for implantable devices and medicinal materials to prevent infection and promote wound healing, in antibiotic delivery systems to treat disease, in bacterial detection systems to generate microbial diagnostics, and in antibacterial vaccines to control bacterial infections. The antibacterial mechanisms of NPs are poorly understood, but the currently accepted mechanisms include oxidative stress induction, metal ion release, and non-oxidative mechanisms. The multiple simultaneous mechanisms of action against microbes would require multiple simultaneous gene mutations in the same bacterial cell for antibacterial resistance to develop; therefore, it is difficult for bacterial cells to become resistant to NPs. In this review, we discuss the antibacterial mechanisms of NPs against bacteria and the factors that are involved. The limitations of current research are also discussed.

Characterization of methicillin-resistant Staphylococcus aureus isolates from fitness centers in the Memphis metropolitan area, Tennessee

Indoor skin-contact surfaces of public fitness centers may serve as reservoirs of potential human transmission of methicillin-resistant Staphylococcus aureus (MRSA). We found a high prevalence of multidrug-resistant (MDR) MRSA of clonal complex 59 lineage harboring a variety of extracellular toxin genes from surface swab samples collected from inanimate surfaces of fitness centers in the Memphis metropolitan area, Tennessee. Our findings underscore the role of inanimate surfaces as potential sources of transmission of MDR MRSA strains with considerable genetic diversity.