Antimicrobial resistance and genomic analysis of staphylococci isolated from livestock and farm attendants in Northern Ghana

Background: The emergence of antimicrobial resistant bacteria in food producing animals is of growing concern to food safety and health. Staphylococci are common inhabitants of skin and mucous membranes in humans and animals. Infections involving antibiotic resistant staphylococci are associated with increased morbidity and mortality, with notable economic consequences. Livestock farms may enable cross-species transfer of antibiotic resistant staphylococci. The aim of the study was to investigate antimicrobial resistance patterns of staphylococci isolated from livestock and farm attendants in Northern Ghana using phenotypic and genotypic methods. Antimicrobial susceptibility testing was performed on staphylococci recovered from livestock and farm attendants and isolates resistant to cefoxitin were investigated using whole genome sequencing.

Results: One hundred and fifty-two staphylococci comprising S. sciuri (80%; n = 121), S. simulans (5%; n = 8), S. epidermidis (4%; n = 6), S. chromogens (3%; n = 4), S. aureus (2%; n = 3), S. haemolyticus (1%; n = 2), S. xylosus (1%; n = 2), S. cohnii (1%; n = 2), S. condimenti (1%; n = 2), S. hominis (1%; n = 1) and S. arlettae (1%; n = 1) were identified. The isolates showed resistance to penicillin (89%; n = 135), clindamycin (67%; n = 102), cefoxitin (19%; n = 29), tetracycline (15%; n = 22) and erythromycin (11%; n = 16) but showed high susceptibility to gentamicin (96%; n = 146), sulphamethoxazole/trimethoprim (98%; n = 149) and rifampicin (99%; n = 151). All staphylococci were susceptible to linezolid and amikacin. Carriage of multiple resistance genes was common among the staphylococcal isolates. Genome sequencing of methicillin (cefoxitin) resistant staphylococci (MRS) isolates revealed majority of S. sciuri (93%, n = 27) carrying mecA1 (which encodes for beta-lactam resistance) and the sal(A) gene, responsible for resistance to lincosamide and streptogramin. Most of the MRS isolates were recovered from livestock.

Conclusion: The study provides insights into the genomic content of MRS from farm attendants and livestock in Ghana and highlights the importance of using whole-genome sequencing to investigate such opportunistic pathogens. The finding of multi-drug resistant staphylococci such as S. sciuri carrying multiple resistant genes is of public health concern as they could pose a challenge for treatment of life-threatening infections that they may cause.