Characterization of Methicilin Resistant Staphylococci Isolated from Pigs in Nsukka Agricultural Zone Enugu State, Nigeria.

Abstract

Methicillin-resistant staphylococci from 291 randomly selected pigs in 16 farms from three selected LGAs were examined. Samples were cultured on ORSAB medium, Gram stained and tested for catalase production. They were confirmed as MRS by latex agglutination test kit detection of penicillin binding protein (PBP2') and PCR detection of mecA gene. Species identification was carried out using PCR amplification of nuc, spa genes and sequencing of sodA and 16S rDNA genes. The isolates were examined for coagulase, biofilm production and haemolysis using tube test, colonial appearance on modified congo red agar and sheep blood agar respectively. Their antibiogram was determined against a panel of 16 antibiotics using disc diffusion methods and were evaluated for sugar fermentation ability against a panel of 8 sugars. Chi square was used to determine the strength of association between occurrence of MRS and sex of the pigs, site on the pigs and LGA where samples were collected; and between methicillin resistance and biofilm production and haemolysis. All statistical analysis were carried out at 5% probability level. In the LGAs, 8.2%, 7.5% and 7.7% pigs haboured MRS in Nsukka, Udenu and Igbo-Eze LGA respectively. Eleven (68.8%) farms were positive for MRS with farm prevalence ranging from 0-18.5%. Twenty one MRS strains from 19 (6.5%) pigs through PBP2' test and 28 MRS strains from 24 (8.2%) pigs through mecA gene detection were isolated namely: S. sciuri (50%), S. lentus (25%), S. Cohnii (17.9%) and S. Haemolyticus (7.1%). MRS were isolated from 8.9% of male and 7.9% of female pigs; and from 5.2% of ear and 4.5% of nasal sites. No significant (p>0.05) association were observed between occurrence of MRS and sex, site and LGA where samples were collected; and also between methicillin resistance and biofilm and haemolysis. All the isolates were coagulase negative, while 3 (10.7%) and 15 (53.6%) were haemolytic and biofilm producers respectively. The MRS demonstrated high resistance to oxacillin (100%), ampicillin (96.4%) and streptomycin (89.3%) and low resistance to chloramphenicol (10.7%), gentamycin (14.3%) and clindamycin (14.3%). All the isolates were resistant to 3 or more of the 16 antibiotics tested with 92.9% resistant to 5 or more antibiotics. The most fermented sugar was glucose (100%) and mannitol (96.4%) while the least was dulcitol (35.7%) with 83.9% fermenting 5 or more of the 8 sugars tested. This study has shown that MRS are present in pig population in Nsukka Agricultural Zone, Enugu State, Nigeria with S. sciuri being the most prevalent species. These MRS are of clinical and public health significance.