[Oxacillin and gentamicin-resistant Staphylococcus aureus: surveillance and development over a period of 6 months]

Abstract

An outbreak of nosocomial infections caused by oxacillin and gentamicin-resistant Staphylococcus aureus occurred over a 3 month period in the intensive care unit of a 371-bed hospital. Four patients were infected. S. aureus isolates were resistant to multiple antibiotics beside oxacillin and gentamicin. They exhibited identical antibiotic susceptibility pattern and identical phage type (47/54/75/77/84/85). A subsequent survey of oxacillin-resistant S. aureus was conducted in the hospital during a 6 month period. Bacteriophage typing was performed on 52 isolates of oxacillin-resistant S. aureus. Seventeen were non typeable . Fourteen had the same phage type (or a minor variant +/- 2 numbers) as that of the previously isolated S. aureus. The antibiotic susceptibility pattern of 10 of the 14 isolates was identical to that of the epidemic strain. The antibiotic susceptibility patterns of 2 isolates differed from it with respect to the resistance to one antibiotic among those tested (these two isolates were obtained from patients that received the particular antibiotic before the isolation of the Staphylococcus). The 7 patients from whom these 12 S. aureus were isolated were staying in the intensive care unit except one who was hospitalized in this unit several months ago. Among the personnel screened, two intensive care unit nurses were found to be nasal carriers of oxacillin resistant S. aureus. One strain had the same phage type as that of the epidemic strain but its antibiotic susceptibility pattern was different. Room-mate to room-mate spread within the intensive care unit may be responsible for the perpetuation of the epidemic strain.(ABSTRACT TRUNCATED AT 250 WORDS)