Microbiological Contamination of Hospital Air

GREENE, V. W. (University of Minnesota, Minneapolis), D. VESLEY, R. G. BOND, AND G. S. MICHAELSEN. Microbiological contamination of hospital air. II. Qualitative studies. Appl. Microbiol. 10:567-571. 1962.-Over 10,000 airborne microorganisms, isolated from various areas of two hospitals, were characterized according to colonial and microscopic morphology and certain physiological reactions, including penicillin resistance and hemolysis. On the basis of all isolates examined during a 15-month period, 42.6 % were gram-positive cocci, 19.2 %O were gram-positive rods, 14.0 %o were gram-negative rods, 17.1 %o were molds, 2.2 % were actinomycetes, 1.2 %O were yeasts, and the remainder were assorted diphtheroids and coccobacillary types. The-distribution of types varied according to hospital area, locations within a given area, and level of gross airborne contamination, but did not vary significantly with season of the year. There appeared to be some relationship between contaminant particle size and type of organism associated with the particle. Distribution of penicillin-resistant types differed markedly in different hospital areas, with proportions ranging from 21.4 o in surgery areas to 4.3 % in incinerator rooms. Of all grampositive cocci isolated, 34.9 %O were hemolytic, and 16.4 % were penicillin-resistant. In the previous report (Greene et al., 1962) the authors described the numbers of airborne contaminants encountered during an extensive microbiological survey of two hospitals. To supplement the (uantitative information with qualitative data, over 10,000 contaminants isolated during this study were characterized. It was thought that information of this type could serve as a useful guide to further environmental studies, particularly if attempts are made to establish sanitary standards for hospital air. Furthermore, even if public health implications are disregarded, these data describe an important parameter of the human environment. The study of airborne microorganisms extends back more than 100 years, and was adequately reviewed by Wells (1955). However, relatively few general surveys have been made of microbial types encountered in hospital l Present address: Electronics Group, General Mills, Inc., Minneapolis, Minn. air (Engley and Bass, 1957; Fredette, 1958; Bourdillon and Colebrook, 1946). Most studies in hospitals have been restricted to the detection of specific pathogens, particularly among the streptococci, the staphylococci, and the clostridia (Blowers and Crew, 1960; Hardyment et al., 1960; Duguid and Wallace, 1948). Other attempts in this field have been handicapped by the lack of efficient volumetric samplers, the tendency to select "typical" colonies and to extrapolate their identification to all other colonies of similar gross morphology, and, finally, the examination of too few isolates to yield a representative picture of a highly variable situation. A notable exception to these shortcomings is encountered in the work by Williams, Lidwell, and Hirch (1956), who studied several thousand isolates obtained from the air of classrooms, offices, factories, dwellings, and outdoors, but unfortunately not in hospitals. This report describes data designed to overcome the above-mentioned deficiencies, and provides a method for mass characterization of colonies which enables rapid cataloging of large numbers of isolates in a relatively short time. MATERIALS AND METHODS The hospitals in which the study was carried out, the sampling apparatus, and the sampling and laboratory methods used for quantitative study of the air samples were described in the preceding communication. After all plate counts were completed, representative plates, which provided at least one sample per hour per sampling location, were chosen for use in the characterization study. During the course of this investigation, between 25 and 35% of the plates obtained in the quantitative survey were retained for the identification sequence outlined below. Each colony on the plate was assigned a code number, and its gross morphology was noted on a master sheet by checking one or more of the following categories: (1) round, raised, entire, glossy, smooth; (2) pinpoint (<2mm diam); (3) flat; (4) rough; (5) dull; (6) irregular; (7) pigmented (note color); (8) mold; (9) other (actinomycete, myxobacteria). Each colony was transferred to an assigned location on a square phage typing dish containing Tryptone glucose yeast extract agar. These dishes, designated as "master 567 on July 1, 2017 by gest ht://aem .sm .rg/ D ow nladed fom