Abstract:
BACKGROUND AND AIM : Methicillin-resistant Staphylococcus aureus (MRSA), an important opportunistic pathogen, is a
Gram-positive coccus known to be resistant to β-lactam antibiotics. Its virulence depends on a large range of factors, mainly
extracellular proteins, such as enzymes and exotoxins, that contribute to causing a wide range of diseases in human and
animal species. The major reasons for the success of this pathogen are its great variability, which enables it to occur and
thrive at different periods and places with diverse clonal types and antibiotic resistance patterns within regions and countries.
Infections caused by antibiotic-resistant S. aureus bring about serious problems in the general population (humans and
animals). Infections with these pathogens can be devastating, particularly for the very young, adults and immunocompromised
patients in both humans and animals. This study aimed to determine the presence of MRSA in both apparently healthy and
sick sheep brought to the veterinary hospital as well as veterinary staff and students on clinical attachment in the hospital.
MATERIALS AND METHODS : A total of 200 nasal swab samples were collected aseptically from sheep and humans (100 each) for
the isolation of MRSA. The samples were processed by appropriately transporting them to the laboratory, then propagated
in nutrient broth at 37°C for 24 h followed by subculturing on mannitol salt agar at 37°C for 24 h, to identify S. aureus.
This was followed by biochemical tests (catalase and coagulase tests) and Gram staining. MRSA was isolated using Clinical
Laboratory Standard Institute (CLSI) guideline and confirmed by plating onto Oxacillin (OX) Resistance Screening Agar
Base agar. The antimicrobial susceptibility pattern of the MRSA isolates was determined using the disk diffusion method
against 12 commonly used antimicrobial agents.
RESULTS : The total rate of nasal carriage of S. aureus and MRSA was found to be 51% and 43% in sheep and humans, respectively.
The MRSA prevalence in male and female sheep was 18% and 8%, while 9% and 8% were for male and female human samples,
respectively. The antimicrobial susceptibility test showed 100% resistance to OX, cefoxitin, oxytetracycline, cephazolin, and
penicillin-G (Pen) by MRSA isolates from humans. Conversely, there was 100% susceptibility to ciprofloxacin, imipenem, and
gentamicin; for linezolid (LZD), it was 87.5%, norfloxacin (NOR) (71%), and erythromycin (ERY) (50%) susceptibility was
recorded. The MRSA isolates from sheep recorded 100% resistance to the same set of drugs used for human MRSA isolates
and were equally 100% susceptible to gentamicin, imipenem, LZD, ciprofloxacin, NOR (92%), and ERY (50%).
CONCLUSION : This study determined the presence of MRSA in sheep and humans from the Veterinary Hospital, Maiduguri.
It appears that certain drugs such as ciprofloxacin, imipenem, and gentamicin will continue to remain effective against
MRSA associated with humans and sheep. Reasons for the observed patterns of resistance must be explored to reduce the burdens of MRSA resistance. Furthermore, the present study did not confirm the MRSA resistance genes such as mecA and
spa typing to ascertain the polymorphism in the X-region using appropriate molecular techniques. Hence more studies need
to be conducted to elucidate these findings using robust techniques.
