Microbiologic surveillance of both the patients and the ambient environment of a surgical intensive care unit allowed us to relate the incidence of nosocomial respiratory tract infection to levels of airborne bacteria. Over the study period respiratory tract nosocomial infection rates varied from 0.7% to 17.0%, and nonrespiratory infection rates varied from 1.0% to 25.0%. Airborne bacteria counts during that time varied from 1.0 ± 0.8 S.E. CFU/ft3 to 96.0 ± 6.8 S.E. CFU/ft3. There was a reasonably close correlation between airborne bacteria levels and the incidence of nosocomial pneumonia (r=0.81, p<0.05). Furthermore, there was a close correlation between a specific organism nosocomial infection rate and the number of colonies of that organism present in the air (r=0.88, p<0.05). In contrast, there was no significant relationship between airborne bacteria counts and nonrespiratory attack rates (r=0.60, p<0.05). If the bacteria traveled from the air to the patients, there appear to be at least three possible explanations for this significant relationship: (1) direct inoculation of the airway by the airborne bacteria; (2) inoculation of the airway by direct contact, which is related to the degree of “cleanliness” of the environment; and (3) an increased incidence of contaminated respiratory equipment and airway inoculation because of high counts of airborne bacteria. It is also possible that high bacterial air counts represent contamination of the air from patients with respiratory infections. Regardless of the pathway(s), surveillance of the ambient environment may prove to be a useful epidemiologic tool in the study and control of nosocomial respiratory tract infections in certain high-risk patient care areas.

Research leading to the development of Sporicidin, a new (synergized glutaraldehyde-phenate) sterilant and concentrated disinfectant, is reported. Microbial evaluation and shelf life testing of the new formulation was done using AOAC tests—Use-Dilution, Sporicidal, Tuberculocidal—and the E.P.A. Virucidal Test. Full-strength Sporicidin sterilizes (is sporicidal) in 6% hours at both 20C and 25C, and disinfects in 1-2 minutes. When diluted with 15 parts of tap water, Sporicidin is tuberculocidal, virucidal, and germicidal in 10 minutes, qualifying as a hospital disinfectant that will not “yellow” the hands or skin. The shelf life of activated Sporidicin, full strength or diluted 1 in 16, is 30 days. According to the data presented, which were the basis of E.P.A. registrations, Sporicidin is: (a) the fastest glutaraldehyde sterilant at room temperature, and (b) the only glutaraldehyde product that can be diluted below 2% and still qualify as a hospital disinfectant.

During a hospital epidemic of infections with gentamicin-resistant Serratia marcescens (GRS), we studied the relation between receiving antibiotics and acquiring GRS. In a five-month period, 22 patients acquired GRS, whereas 18 patients acquired gentamicin-sensitive Serratia (GSS). When compared with patients with nosocomial GSS infection, patients with nosocomial GRS had been in the hospital (p = 0.04) and the intensive care unit (p = 0.003) longer before infection and more had received gentamicin (p = 0.001) or ampicillin (p = 0.02) before infection. To control for the influence of underlying disease, we matched all 12 ICU patients with GRS infection and 12 patients without GRS infection for underlying illness and duration of intensive care. Use of any antibiotic (p = 0.04), or a combination of gentamicin plus ampicillin or cephalosporin (p = 0.047) was more common among patients with GRS infection. The hospital had not significantly increased the use of aminoglycosides from the previous year. We conclude that for the individual patient antimicrobial therapy, especially with gentamicin or ampicillin, creates a risk for later infection by GRS that is independent of the severity of the underlying illness.

This communication is the third in a four-part series on nosocomial viral infections from the Strong Memorial Hospital. This third article discusses guidelines for prevention and control of exanthematous viruses, gastroenteritis viruses, adenoviruses and the picornaviruses other than rhinoviruses. Several uncommonly seen viruses, such as the virus of Creutzfeldt-Jakob disease and Marburg, Ebola, and Lassa fever viruses, also are reviewed briefly.