ANTIBIOTIC RESISTANCE AND SEROTVPES OF

Abstract

A total of 75 recent distinct isolates of Ps,aerug;nosQ were recovered from clinical specimens in three hospitals in Madinah, Saudi Arabia. The minimal inhibitory concentrations (MIC) against 8 corrunonly antipseudomonal antibiotics were determined by an agar dilution method. Ciprofioxacin (CP), amikacin (AK), ortobramycin (TO), and imipenem (1M), and gentamicin (GM) showed the highest activity against the tested isolates. The resistance rates for CP, AK, or TO were 5%. whereas those for 1M, and GM were 8, and 17% respectively. Although aztreonam and ceftazidime exhibited comparable resistance rates of 22 and 24% respectively, cross-resistance between them was not observed, nor with 1M. Whereas most of strains were resistant to ceftriaxone (94%). In contrast, strains resistant to AK or TO were also resistant to OM, but the reciprocal was not true. Ps.aeruginosa isolates were further serotyped and tested for pyocin activity against 7 indicator strains .. Serotype 0:6 was the commonest, and 13 serotypes were defined, though 51% of the strains were non-typable. Apart from an apparent nosocomial association in one hospital. there was no apparent correlation between serotypes. pyocin profiles, and antibiotic resistance markers, nor to the origin of the clinical specimens.