Antimicrobial Resistance Patterns of Methicillin Resistant Staphylococci in Medical Students of Some Nigerian Universities.
Etim, M. E.
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This study was undertaken to establish the prevalence of hospital acquired and community acquired methicillin resistant Staphylococci, to determine the antimicrobial resistance patterns and clonal relationships of isolated methicillin resistant Staphylococcifrom medical students of Imo State University, Abia State University and University of Uyo. Four hundred and forty sampleswere collected from palms, nostrils and throats of medical students and screened using standard microbiological techniques. Staphylococcus species isolated on the basis of growth on mannitol salt agar were further characterized based on biochemical tests, resistance to oxacillin and other antibiotics. Isolates were classified based on school, class, type of sample, species, age and gender. Data generated were analyzed descriptively and frequencies were expressed in percentages. Polymerase Chain Reaction was used to detect the Staphylococcus nuc, mecA, and blaZgenes. Genetic fingerprinting of 31 different isolates of methicillin resistant Staphylococci from medical students of the three schools sampled was carried out using 2 primers (blaZ-F and blaZ-R) of Random Amplified Polymorphic DNA to determine if methicillin resistant isolates are clones of each other. A total of 248 Staphylococcus spp. were identified as Staphylococcus aureus (191) and coagulase-negative Staphylococci (57). The Staphylococcus aureus strains were highly resistant to methicillin (oxacillin) and ampicillin (59.7%), penicillin (68.1%) and several non-β-lactams including clindamycin (28.2%), erythromycin (38.3%), trimethoprim (74.3%), and vancomycin (21.8%). The frequency of methicillin resistance among Coagulase negative Staphylococci was 94% with no resistance to nitrofurantoin (0%), moderate resistance to erythromycin (0.8%), vancomycin (4.8%) and clindamycin (13.3%). Out of 193 methicillin resistant isolates, pre-clinical students had higher frequencies with 44% Methicillin resistant Staphylococcus aureus compared to their clinical counterparts with 32.6%Methicillin resistant Staphylococcus aureus and 11.9% methicillin resistant coagulase negative Staphylococci compared with their clinical counterparts with 11.4% methicillin resistant coagulase negative Staphylococci. The prevalence rate of methicillin resistant Staphylococci for male and female group was 59.7% and 40.3% respectively. Methicillin resistant Staphylococci occurred more in students aged 26-30 years of age. The relationship between age and sex was statistically insignificant (p>0.05). A dendrogram was constructed usingthe Unweighted Pair Group Method with Arithmetic Averages analysis with the Random Amplified Polymorphic DNA data generated which clustered thirty-one (31) randomly selected methicillin resistant Staphylococci isolates from these schools into different clusters and sub-clusters based on their genetic relation. However, only two clones were observed in the third sub-cluster of the second cluster. All members of the respective clones are of the same origin and the clonal groupings are in accordance with the geographical distribution indicating possible relationship between host origin and genetic variation among those isolates. Polymerase Chain Reaction based Random Amplified Polymorphic DNA proved to be an easy yet helpful method for molecular typing and identification of clonal relationships. This study has demonstrated high prevalence of methicillin resistant Staphylococci among medical students in Imo State University (21.8%), Abia State University (20.2%) and University of Uyo (58.1%)and underlines the need for periodic surveillance studies of this type. Reassessment of policies on antibiotics use in Nigeria, development and enforcement of measures to prevent the spread of methicillin resistant Staphylococci infections in the community and in the hospitals are recommended.