Antibiotic susceptibility of coagulase-negative staphylococcal blood isolates with special reference to adherent, slime-producing Staphylococcus epidermidis strains.

The epidemiologic relationship between slime-producing coagulase-negative staphylococci and antibiotic resistance was evaluated by analyzing the in vitro susceptibility of 278 blood isolates to 10 different antimicrobial agents. The strain collection consisted of 60 coagulase-negative staphylococcal septicemia isolates, recovered from at least 2 successive blood cultures from 59 septicemia patients and 218 single blood isolates defined as insignificant. When the slime-producing Staphylococcus epidermidis isolates were compared with all non-slime-producing S. epidermidis isolates, the slime-producing isolates exhibited higher MIC50 and/or MIC90 values than the non-slime-producing isolates, and were also more commonly resistant against many of the antimicrobials tested. The association between slime production and resistance against tobramycin, gentamicin and rifampicin was statistically significant (p less than 0.05). A similar finding was observed among the S. epidermidis septicemia isolates when they were analyzed separately from the single (suspected blood contaminant) S. epidermidis isolates. Further characterization of the septicemia isolates revealed that the positive correlation between slime production and antibiotic resistance reflected, to some extent, multiresistance of 1 epidemic slime-producing S. epidermidis strain. No difference in resistance was observed between the slime-producing and non-slime-producing single S. epidermidis blood isolates.