The utility of restriction endonuclease analysis and phage typing in the epidemiologic investigation of a Staphylococcus aureus outbreak in a neonatal nursery.

Outbreaks of Staphylococcus aureus infections in neonatal units require prompt investigation and implementation of control measures. From January to March 1990, a marked increase in the number of S. aureus infections was observed in a neonatal nursery. Twenty-seven S. aureus isolates from 23 patients were analyzed by phage typing and restriction endonuclease analysis (REA). Only nine strains were differentiated by phage type. However, REA with HindIII, CfoI, and ClaI differentiated 20 strains. The REA results indicated that the outbreak was due to several different S. aureus strains and did not represent transmission of a single epidemic strain. REA may enable more accurate determination of the presence or absence of an epidemic strain during an outbreak than would traditional methods such as phage typing.