Bacteriologic surveillance of the patient isolator system

Elimination of bacteria from dogs with antibiotics

The effect of oral administration of neomycin cephalothin or kanamycin cephalothin on the aerobic intestinal bacterial flora, was studied in dogs maintained under isolation conditions in a conventional animal room. The dogs were successfully freed of aerobic bacteria with both combinations within two to seven days after the start of antibiotic treatment, and were maintained bacteria free for up to 21 days. Decontamination was attained more rapidly in dogs that were bathed in hexachlorophene surgical soap before and during the first and third days of antibiotic treatment. There was no evidence of toxicity from either of the antibiotic combinations. These results indicate that, as with mice and monkeys, decontamination of dogs with oral antibiotics is feasible. The technique is of potential value in preventing endogenous bacterial infections in canine experimental studies involving use of immunosuppressive agents.

Oropharyngeal cultures of patients in protected environment units: evaluation of semiquantitative technique during antibiotic prophylaxis

A semiquantitative culture technique was used to monitor the microbial flora of the oropharynx of 30 patients receiving antibiotic prophylaxis in protected environment units. After institution of antibiotic prophylaxis, the median concentration of organisms in the oropharynx fell by 2 logs but gradually increased by 1 log and then remained stable. Neisseria spp., Micrococcus sp., and Streptococci were generally eradicated by the antibiotics but were replaced by Lactobacilli and yeast. Four of nine enteric organisms persisted despite in vitro sensitivity to the antibiotic regimens. Yeast were cultured from the initial specimens of only 17% of the 30 patients, but they were cultured subsequently from specimens of 80% of the 20 patients who remained in protected environment units for at least 8 weeks.

Microbiological evaluation of protected environments during patient occupancy

Microbiological monitoring has been conducted in two life island (LI) units and two laminar airflow (LAF) rooms while they were occupied by patients undergoing cancer chemotherapy. There were only 5 organisms per 1,000 ft(3) of air sampled in LAF rooms, 31 organisms in LI units, and over 3,000 organisms in regular hospital rooms. None of the floor samples obtained from hospital rooms was sterile, compared to over 70% in LAF rooms. The rate of deposition of organisms onto settling plates was one organism per 4.5 hr in LAF rooms compared to one organism per 0.08 hr in hospital rooms. Potential pathogens were isolated much more frequently from environmental samples obtained from hospital rooms than from LI units or LAF rooms. Two sites of persistent contamination arose in the LAF rooms: the vinyl tile flooring and the water supply system. Over half of the potential pathogens cultured from the protected environment units were cultured initially from the patients who occupied the units.

Semiquantitative oropharyngeal culture technique

A semiquantitative method for determining the concentration of organisms constituting the normal oropharyngeal flora has been developed. Eleven species of organisms were isolated from the 18 subjects studied. The concentration of organisms in multiple samples, taken at 5-min intervals, was quite similar. The concentration of organisms increased slightly at the end of the day. Obtaining specimens on different days of the week did not appreciably affect the concentration or kinds of organisms. Eating had only a minimal effect on the oropharyngeal flora, but brushing teeth reduced the concentration of organisms substantially. When specimens were obtained 6 months after the initial specimens, the concentration of organisms remained the same but the species of organisms isolated varied considerably. The gargle method was compared to a swab method and proved to be superior. This method of obtaining oropharyngeal culture specimens is reliable and useful as a means of monitoring the normal oropharyngeal flora.