Nasal Carriage of Methicillin-Resistant Staphylococcus Sciuri Group by Residents of an Urban Informal Settlement in Kenya

Abstract

Background: The Staphylococcus sciuri group constitutes animal-associated bacteria but can comprise up to 4% of coagulase-negative staphylococci isolated from human clinical samples. They are reservoirs of resistance genes that are transferable to Staphylococcus aureus but their distribution in communities in sub-Saharan Africa is unknown despite the clinical importance of methicillin-resistant S. aureus.
Objectives: We characterised methicillin-resistant S. sciuri group isolates from nasal swabs of presumably healthy people living in an informal settlement in Nairobi to identify their resistance patterns, and carriage of two methicillin resistance genes.
Method: Presumptive methicillin-resistant S. sciuri group were isolated from HardyCHROM™ methicillin-resistant S. aureus media. Isolate identification and antibiotic susceptibility testing were done using the VITEK®2 Compact. DNA was extracted using the ISOLATE II genomic kit and polymerase chain reaction used to detect mecA and mecC genes.
Results: Of 37 presumptive isolates, 43% (16/37) were methicillin-resistant including - S. sciuri (50%; 8/16), S. lentus (31%; 5/16) and S. vitulinus (19%; 3/16). All isolates were susceptible to ciprofloxacin, gentamycin, levofloxacin, moxifloxacin, nitrofurantoin and tigecycline. Resistance was observed to clindamycin (63%), tetracycline (56%), erythromycin (56%), sulfamethoxazole/trimethoprim (25%), daptomycin (19%), rifampicin (13%), doxycycline, linezolid, and vancomycin (each 6%). Most isolates (88%; 14/16) were resistant to at least 2 antibiotic combinations, including methicillin. The mecA and mecC genes were identified in 75% and 50% of isolates, respectively.
Conclusion: Colonizing S. sciuri group bacteria can carry resistance to methicillin and other therapeutic antibiotics. This highlights their potential to facilitate antimicrobial resistance transmission in community and hospital settings. Surveillance for emerging multidrug resistant strains should be considered in high transmission settings where human-animal interactions are prevalent. Our study scope precluded identifying other molecular determinants for all the observed resistance phenotypes. Larger studies that address the prevalence and risk factors for colonization with S. sciuri group and adopt a one health approach can complement the surveillance efforts.