ABSTRACT
BACKGROUND: Chronic leg ulcers are hard to treat and can be a burden, particularly in resource-limited settings where diagnosis is a challenge. Staphylococcus aureus is among the common bacteria isolated from chronic wounds with a great impact on wound healing, particularly in patients with co-morbidities. Antimicrobial resistance genes and virulence factors in Staphylococcus aureus isolates were assessed to support healthcare professionals to make better therapeutic choices, and importantly to curb the development and spread of antibiotic resistance. METHODS: A cross-sectional study involved both inpatients and outpatients with chronic leg ulcers was conducted from August 2022 to April 2023 in 2 health facilities in Kilimanjaro region in Tanzania. Antimicrobial susceptibility testing was done using the disc diffusion method. Further, whole genome sequencing was performed to study the genotypic characteristics of the isolates. RESULTS: A total of 92 participants were recruited in which 9 participants were only positive for 10â¯Staphylococcus aureus isolates upon culture. Five STs among 9 isolates were identified. Most of them belonged to ST8 (44%), with 1 isolate does not belong to any ST. Additionally, 50% of the isolates were methicillin-resistant Staphylococcus aureus (MRSA). All S. aureus isolates had almost similar virulence factors such as hemolysin, proteases and evasions that promote toxin production, protease production and host immune evasion respectively. Moreover, all mecA positive S. aureus isolates were phenotypically susceptible to cefoxitin. CONCLUSION: Presence of mecA positive S. aureus isolates which are also phenotypically susceptible to cefoxitin implies the possibility of classifying MRSA as MSSA. This may result in the possible emergence of highly cefoxitin - resistant strains in health care and community settings when subsequently exposed to beta-lactam agents. Therefore, combination of whole genome sequencing and conventional methods is important in assessing bacterial resistance and virulence to improve management of patients.
ABSTRACT
OBJECTIVES: Plasmids are infectious double stranded DNA molecules that are found within bacteria. Horizontal gene transfer promotes successful spread of different types of plasmids within or among bacteria species, making their detection an important task for guiding clinical treatment. We used whole genome sequenced data to determine the prevalence of plasmid replicon types in clinical bacterial isolates, the presence of resistance and virulence genes in plasmid replicon types, and the relationship between resistance and virulence genes within each plasmid replicon. METHODS: All bacterial sequences were de novo assembled using Unicycler before extraction of plasmids. Assembly graphs were submitted to Gplas+plasflow for plasmid contigs prediction. The predicted plasmid contigs were validated using PlasmidFinder. RESULTS: A total of 159 (56.2%) out of 283 bacterial isolates were found to carry plasmid replicons, with Escherichia coli, Klebsiella pneumoniae, and Staphylococcus aureus being the most prevalent plasmid carriers. A total of 26 (86.7%) multiple-replicon types were found to carry both resistance and virulence genes compared to 4 (13.3%) single plasmid replicons. No statistically significant correlation was found between the number of antibiotic resistance and virulence genes in multiple-replicon types (r = - 0.14, P > 0.05). CONCLUSION: Our findings show a relatively high proportion of plasmid replicon-carrying isolates suggesting selection pressure due to antibiotic use in the hospital. Co-occurrence of antibiotic resistance and virulence genes in clinical isolates is a public health problem warranting attention.
