Slime production and antibiotic susceptibility in staphylococci isolated from clinical samples

ABSTRACT

A total of 187 isolates from several clinical specimens were identified to species level as 129 Staphylococcus aureus strains and 58 coagulase-negative staphylococci (CNS) strains by the API Staph System (Biomerieux). Slime production was detected both by the conventional Christensen's method as well as by the Congo red agar method. Seventy-two strains of staphylococci isolates (38.5 percent) were found to be slime producers by Christensen's test tube method whereas 58 strains (31 percent) were slime positive with Congo red agar method. There was no statistically significant difference between the two methods for the detection of slime production (P > 0.05). Susceptibility of isolates against antimicrobial agents was tested by the disk diffusion method. Staphylococcal species had resistance to one or more antibiotics. Among the various antimicrobial agents, oxacillin (71.1 percent) and erythromycin (47.1 percent) showed higher resistance than most of the agents used against all isolates. Oxacillin resistant S. aureus (ORSA) and oxacillin resistant coagulase-negative staphylococci (ORCNS), 97 (75.2 percent) and 36 (62.1 percent) respectively were frequently observed in strains isolated from clinical materials. Among the ORSA strains, two strains were resistant to vancomycin. Moreover, 96 (74.4 percent) of 129 S. aureus strains were positive for blactamase enzyme. However, 78 (81.25 percent) of 96 b-lactamase positive S. aureus strains were b-lactamase positive ORSA isolates, but none of them had vancomycin resistance.