Resistance Pattern of Clinical Isolates of Staphylococcus Aureus against Five Groups of Antibiotics

Among the samples received in pathology laboratory, Pakistan Institute of Medical Sciences, Islamabad, 5069 samples had bacterial growth, among these 2580 (51%) samples were Gram-positive cocci and 1688 were Staphylococcus aureus during a period of two years. Out of these Gram-positive cocci 56% were resistant to penicillin group, 27% were resistant to cephalosporin group, 22% were resistant to aminoglycoside group, 15% were resistant to quinolone group and 31% were resistant to other antibiotics (cotrimaxazole, erythromycin, aztreonam, vancomycin, nitrofurantoin and meropenam). Antibiograms of Gram-positive cocci were determined against various antibiotics by disc diffusion method. The rate of resistance to most of the antibiotics such as ampicillin, piperacillin, carbenicillin, penicillin, cephradine, cefotaxime, oxacillin, ceftriazone, amikacin, ceclor, ofloxacin, pefloxacin, ciprofloxacin, cotrimexazole (septran), gentamicin, meropenem, ceftazidime, erythromycin, tobramycin, enoxacin was higher when tested against the isolates collected from pus as compared to those from blood and urine. Antibiotic resistant strains were more prevalent in pus samples than the other clinical isolates (blood and urine). The randomly selected 155 strains of Staphylococcus aureus when tested against five groups of antibiotics showed resistance rate against ampicillin (92%), cephradine (60%), and gentamicin (58%). However intermediate resistance was found in case of vancomicin (38%), in hospitalized and non-hospitalized patients.