Studies On Coagulase‐Negative Staphylococci In Patients Undergoing Cardiac Surgery

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Abstract
Hypotheses for the origin of multiply-resistant coagulase-negative staphylococci from 146 patients undergoing cardiac surgery were tested. All received cephalothin pre-operatively. Antibiotic susceptibility testing, phage typing, biotyping and test for Tween 80-splitting enzyme were used to characterize 132 isolates from nose swabs. Of the pre-operative susceptible isolates, 75% were of biotype 1, while biotypes 3 and 4 made up 59% of the post-operative, multiply-resistant isolates. Of the isolates, 53% were typable by phage typing. Typability of isolates of biotype 1 was high (56%) while almost 75% of biotype 4 were untypable. Susceptible isolates were more often typable than multiply-resistant ones. Of the 146 patients, 105 (72%) carried coagulase-negative staphylococci pre-operatively, only 2 of them carried multiply-resistant strains. Fifty-nine patients (41%) were colonized with multiply-resistant coagulase-negative staphylococci post-operatively. By combining the results of biotyping, phage typing and test for Tween-splitting enzyme the study made it probable that a maximum of 10 patients (6.8%) already carried multiply-resistant strains on admission to the hospital or were carriers of initially susceptible strains which developed multiple-resistance during administration of antibiotics. It therefore seemed likely that most of the patients were deprived of their natural bacterial flora by antibiotic treatment and subsequently colonized post-operatively with multiply-resistant coagulase-negative staphylococci from the environment.