Comparative Evaluation of Cefoxitin Liofilchem® Mic Etest Strips and Cefoxitin Disc for Detection of Methicillin Resistant Staphylococcus aureus Isolated from Clinical Specimens in Federal Capital Territory, Nigeria

This study evaluated the efficacy of Cefoxitin Liofilchem^® MIC Test Strips and the disc diffusion test on methicillin-resistant S. aureus (MRSA) isolated from hospital patients in Abuja, Nigeria from February to November 2015. Specimens were collected and identified by culturing on bacteriological media. Staphylococcus aureus isolated were confirmed for MRSA using oxacillin resistance screening agar base (ORSAB). Out of 48 MRSA isolated, 31.3% were isolated from urine specimens, 20.8% wound swabs, 14.6%  Endo cervical swabs,14.6%  High vaginal swabs, 10.4%  ear swab and 8.3%  urethral swabs. The age range with the highest isolation rate is between 20-40 years while the lowest was from 40 and above. Antibiotics susceptibility testing of 48 identified Methicillin-Resistant S. aureus (MRSA) strains isolated from clinical samples in six-selected hospital in Federal Capital Territory (FCT) Abuja, Nigeria were tested for in vitro sensitivity to commonly used antibiotics using disk diffusion and Etest methods. High resistance was observed against cefoxitin (100%), oxacillin (100%), amoxicillin (87.5%), tetracycline (64.6%), erythromycin (56.3%), ceftazidime (56.3%), clindamycin (43.8%), ciprofloxacin (27.1%), and linezolid (22.9%). The antibiotics susceptibility study showed that Vancomycin was the highest effective drug of choice (100%).  A high percentage (34.2%) of the isolates was multidrug resistant while 65.8% of the isolates had MARI ≥ 0.4. Out of 48 phenotypically identified MRSA isolates on agar disc diffusion method, further evaluation using MIC test strip showed that 62.5% (30) were susceptible to cefoxitin, while 37.5% (18) were resistant. All the isolates were resistant to more than five antibiotics tested; the MIC of these isolates to cefoxitin ranges from 6 - 64 µg/ml and 0.38 – 2 µg/ml for vancomycin.  Vancomycin   MIC test strips were 100% susceptible. This study observed that MIC strip test is more accurate than agar disc diffusion method as 62.5% of the isolates that were resistant to cefoxitin on agar disc diffusion test were observed to be susceptible while 37.5% were resistant.