Clinical and Laboratory Studies of NosocomialStaphylococcus aureusResistant to Methicillin and Aminoglycosides

Abstract

A methicillin/aminoglycoside-resistant strain of Staphylococcus aureus (MARS) was likely introduced by transfer of a patient from another hospital. Over the next year, 20 other patients were colonized or infected with MARS of the same phage type, although antibiograms varied. Affected patients usually had serious underlying disease and were in intensive care units. Vancomycin therapy was frequently delayed and MARS may have contributed to the death of some patients. The mode of spread was not definitively delineated, but two nurses were found to be colonized. Institution of isolation procedures was difficult, but the problem gradually waned.Susceptibility testing showed vancomycin to be the most active agent. Synergy studies showed no consistent effect of combining methicillin with an aminoglycoside. This experience illustrates the problem of MARS spread between hospitals and wards, the need for institution of effective control measures, and consideration of early empiric use of vancomycin.

Efficacies of rapid agglutination tests for identification of methicillin-resistant staphylococcal strains as Staphylococcus aureus

“…Strain variability was documented by phage typing and differing antimicrobial susceptibility patterns. An unacceptably high number of MRSA were misidentified as coagulasenegative staphylococci, which could result in inadequate treatment and isolation of patients with MRSA and contribute to patient morbidity and mortality as well as to the spread of this troublesome pathogen (7).…”

Antimicrobial agent susceptibility patterns of bacteria in hospitals from 1971 to 1982

“…Before 1946, 85% of Staphylococcus aureus strains were highly susceptible to penicillin; today, only 11% remain susceptible (12). The medical community has been warned repeatedly of major increases in bacterial resistance (23,28,34,39,41), with many reports citing the increased resistance of S. aureus to methicillin (1,4,5,7,8,11,19,41,44,49) and gentamicin (5,10,11,44,48), of Haemophilus influenzae to ampicillin (16,20,27,51), of gram-negative bacilli, especially Pseudomonas aeruginosa, to aminoglycosides (13,17,24,31,32,37,38,50), and the increasing multiple drug resistance among enterococci (30, 33). The new cephalosporins appear to be responsible for bacterial cross-resistance to several betalactam antibiotics and occasionally to the aminoglycosides (43).…”