Surveys of hospital infection in the Birmingham region. I. Effect of age, sex, length of stay and antibiotic use on nasal carriage of tetracycline-resistant Staphyloccus aureus and on post-operative wound infection

Abstract

Cross-sectional surveys of infection in relation to ward structure and practice were made in 38 hospitals between 1967 and 1973, including repeat surveys in 12 hospitals. The survey team (a research nurse and a senior microbiologist or technician) visited one ward a day and entered data on patients, including appearance of wounds seen at change of dressings, on the structure of the ward, and on ward practices; bacteriological swabs were taken from noses of all patients and staff of wards visited and from infected or open wounds, also from some environmental sites. Effect of age, sex, length of hospital stay and antibiotic use on carriage of tetracycline-resistant Staphylococcus aureus and on post-operative sepsis are considered here.Clinical infection (sepsis), further classified as ;severe', ;moderate' or ;mild' in accordance with a code of physical signs, including inflammation and suppuration, was found in 6.1% of clean undrained operation wounds. Drained wounds and those through hollow, heavily colonized viscera (;contaminated' wounds) had higher sepsis rates than undrained and ;clean' wounds; there was less sepsis with closed drainage and with small drains. Staph. aureus (24%) was the commonest single bacterial species, but gram-negative bacilli (50%) were found in a much larger proportion of septic wounds. The results showed that the infection rate was lowest among patients between 20 and 40 years old. Infection was significantly more common in male than in female patients.Nasal carriage of tetracycline-resistant Staph. aureus, used as an index of hospital-acquired infection, was commonest in geriatric patients and least common in gynaecological patients. There was correlation between nasal carriage of tetracycline-resistant staphylococci and age of the patient, length of hospital stay, sex, (male greater than female), operative treatment, and treatment with tetracycline, ampicillin and nitrofurantoin, but not with penicillin.