Cross-infection Mechanisms in a Ward with Controlled Practices

Abstract

The aim of this study was to examine the relevance of some patient parameters to nasal carriage and wound infection. This was based on cross-sectional surveys made in 38 hospitals between 1967 and 1973, a small continuous survey in two hospitals in 1977, and a continuous survey in one ward made 10 years previously. An attempt was made to formulate a mathematical model measuring the significance of patient parameters on the nasal acquisition of multiple-resistant Staph.aureus.  A comparison of the two types of survey was also made. The primary analysis showed that age and sex were related to the probability of a wound becoming infected, In addition to age and sex, antibiotic usage and length of stay in hospital affected the extent of nasal colonization with Staph.aureus. Multiple-resistant, penicillin-resistant and sensitive strains were considered both separately and together. In the primary analysis, the factors affecting the probability of wound infection and nasal colonization were similar in both the single ward continuous survey and the cross-sectional surveys. The more recent continuous survey showed a reduction in multiple-resistant Staph aureus in the patients noses when compared with the previous surveys, but, the carriage of penicillin-resistant only strains still increased with length of stay. The multiple-regression analysis of the single-ward continuous survey confirmed that age and length of stay were independent significant factors influencing the carriage of multiple-resistant Staph.aureus. However, sex was not significant and antibiotic usage did not influence the carriage rate, as in the large cross-sectional survey. The regression model developed was based on the assumption that nasal carriage of multiple resistant Staph.aureus is a measure of certain aspects of susceptibility to infection.