In-vitro antimicrobial susceptibility pattern of Staphylococcus aureus isolates in Umuahia, Abia state, Nigeria

Abstract

The antimicrobial susceptibility pattern of Staphylococcusaureus in Umuahia was investigated in this study. A total of 113 strains of S. aureus consisting of 30 isolates from clinical specimens obtained from 10 medical Laboratories and 83 isolates from nasal swabs of University students in Umuahia, were tested against 10 antimicrobial agents using the disc agar diffusion method. Resistance to penicillin, ampicillin, cloxacillin and tetracycline was 100% among strains isolated from clinical specimens. The clinical isolates also exhibited high rates of resistance to chloramphenicol (97%) and erythromycin (97%). Seven (23%) of these isolates were sensitive to Gentamicin and 6 (20%) to Streptomycin. Likewise, all the 83(100%) and 82 (98.8%) were resistant to penicillin and cloxacillin, respectively. Isolates from nasal passages appeared to be less resistant to chloramphenicol (54.2%), gentamicin (43.4), streptomycin (31.3%) and tetracycline (51.8%). Ampicillin did not produce any zone of inhibition against 29 (96.7%) isolates from clinical specimens and only slightly inhibited one with zone of inhibition of 8 mm. Nineteen of the isolates manifested low to high level of resistance to chloramphenicol with mean zone of inhibition ranging from 15. 8+or-0.7 mm to 9.8+or-2.0 mm. All the isolates were completely resistant to penicillin and cloxacillin with no zone of inhibition at all. In the case of gentamicin, 5 (16.7%) had intermediate susceptibility (mean zone of inhibition 14+or-0 mm), 12(40%) had mean inhibition zone of 9.6+or-2.9 mm and 6(20%) were not inhibited. This study shows that S. aureus strains isolated from clinical specimens and healthy students in Umuahia are highly resistant to common antibiotics. This may not be unconnected with indiscriminate use of antibiotics and calls for more control and rational use of antibiotics to minimize the rate of development of resistance to other antibiotics.