MOLECULAR EPIDEMIOLOGY OF LIVESTOCK-ASSOCIATED METHICILLIN RESISTANT STAPHYLOCOCCUS AUREUS (LA-MRSA) FROM POULTRY IN EBONYI STATE, NIGERIA

MOLECULAR EPIDEMIOLOGY OF LIVESTOCK-ASSOCIATED METHICILLIN RESISTANT STAPHYLOCOCCUS AUREUS (LA-MRSA) FROM POULTRY IN EBONYI STATE, NIGERIA

ABSTRACT

Methicillin resistant Staphylococcus aureus (MRSA) is now a leading cause of staphylococcal infections in humans and animals. In this study, cloacae and nostrils of 1800 poultry birds selected at random in 9 farms spread across Ebonyi State and 19 poultry farm workers from these farms were screened for Staphylococcus aureus. In addition, 150 clinical isolates of staphylococci from Microbiology Laboratories in 3 hospitals, one in each senatorial district of Ebonyi State were screened for Staphylococcus aureus using standard bacteriological techniques. The number of birds positive for S. aureus was 247, representing a percentage carriage of 14% (247/1800). Out of the 150 clinical isolates of staphylococci screened, 78 of them were identified as S. aureus representing a percentage incidence of 52%. Only 4 (21%) of the 19 volunteer poultry farm workers were found to carry S. aureus. More S. aureus were recovered by swabbing both cloacae and nostrils than either of cloacae or nostrils used singly. Antibiotic resistance profile of all the 329 S. aureus isolates using disk agar dilution method (DAD) showed that 8.5% (28/329) of the isolates were methicillin resistant. Percentage carriage of MRSA amongst poultry birds in the State was 6% (15/247). MRSA from broilers constituted 73% (11/15) of the total MRSA in poultry. Only one poultry farm worker had MRSA, representing 25% (1/4) carriage. The percentage of MRSA amongst the clinical isolates was 15.4% (12/78). The highest antibiotic resistance exhibited by the isolates was recorded against tetracycline with 47.7% (157/329) followed by Trimethoprim/Sulfamethoxazole with 42.5% (140/329). All the isolates were sensitive to Quinupristin/Dalfopristin, Linezolid, Rifampin and Vancomycin. Multidrug resistance (defined as resistance to at least one antibiotic agent in three classes of antibiotics) was recorded amongst S. aureus and MRSA in Ebonyi State. All the MRSA in this study were multidrug resistant. Multiplex PCR showed a correlation between phenotypic recovery of MRSA isolates and genotypic detection of mecA gene. All the isolates that were cefoxitin resistant by disk agar dilution (DAD) method were found to carry the mecA gene. Molecular ix epidemiological analysis revealed that 4 spa types (t002, t084, t2304 and t11469) were circulating in Ebonyi State with spa type t002 being the most prevalent, constituting 47% (22/46) of all the isolates. spa type t084 and t2304 were not found in poultry farm workers. Novel spa type t11469 was recorded in poultry (57%), poultry farm worker (14%) and hospital isolates (29%). Molecular screening for PVL gene (lukS-lukF) showed that only 8 out of 54 isolates were positive, representing a prevalence of 14.8%. All the PVL positive isolates were from poultry. Molecular screening for tetM gene among the tetracycline resistant isolates showed that only one isolate (n=32) harbored the tetM gene which could mean that other tetracycline resistant genes might be responsible for the huge tetracycline resistance observed in this study. Multilocus sequence typing of 9 isolates selected at random including the novel spa type showed that the spa types fell into 3 sequence types (ST5, ST15, ST121). spa types belonging to sequence type ST398 and ST9, the main sequence types of livestock associated methicillin resistant Staphylococcus aureus (LA-MRSA) were not found in poultry in this study. However, a poultry endemic strain t002 belonging to ST5 was found. The SCCmec typing of the isolates carrying the mecA gene showed that all the MRSA isolates typed were type V. The finding of the same spa types in poultry, poultry farm worker and hospital isolates in the State suggests possible zoonosis and interspecies transmission although the actual route of transmission was not investigated. It was also an indication of the involvement of poultry associated S. aureus and MRSA in staphylococcal infections in Ebonyi State.

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