- Volume 13, Issue 2, 1980

A preliminary examination has been made of the effects of salts of heavy metals on bacterial adherence. 3H-thymidine labelled strains of Enterobacteriaceae isolated from sputa were incubated with human buccal cells and metallic salts. 10−4 m zinc or iron salts significantly increased adherence of Enterobacteriaceae to human buccal cells in an in-vitro system. These effects were not altered by variation of the buffer system used, and seem dependent upon interactions between metals and bacteria that occur within about 5 minutes.

Eight isolates of micrococci from the 15100(181163111 of six patients obtained under circumstances suggesting a pathogenic role were studied in detail. The organisms were remarkably uniform in cultural, biochemical and antibiotic-susceptibility characters. All strains showed high resistance to methicillin and hydrolysed arginine. The characters found did not correspond with those of any hitherto described species, but were closest to Micrococcus fyke.

Applied routinely to 1081 recently isolated cultures, the phenol-induced slide-agglutination test (standard procedure) with flagellar antiserum correctly identified 98-9% of Vibrio cholerae strains of O type-I and NAG serotypes; 10% of cultures were unstable in phenol-saline. The incidence of instability and other types of defect was higher (7-3%) in older stock cultures. The majority of such strains were successfully tested by one of the three modified procedures. No cross-reactions were observed in 47 cultures of other species including the halophilic vibrios. Only one out of the 1205 cultures of V. cholerae tested by all procedures reacted negatively; this strain was found to lack functional flagella. These results establish the significance of flagellar specificity as a classificatory determinant in V. cholerae, and the fidelity and utility of the phenol test in routine bacteriology.

Bio typing provided evidence of the phylogenetic relationships between strains of Salmonella typhimurium of phage types 49 and 204 and certain strains of phage type 193, which were interconvertible in phage types. All of 564 strains of phage types 49 and 204, 35 of which were chloramphenicol-resistant, were of biotype 26, whereas those of phage type 193 (91 strains) belonged to six different primary biotypes. Lines of descent are suggested for strains of phage type/biotype: 193/26a, 193/17gand 193/9f.

An antiserum-agar technique was evaluated as a method for detecting Salmonella typhi in faeces. Thirty-one laboratory strains of S. typhi produced immunoprecipitate haloes during overnight growth on SS agar and blood-agar-base infusion agar (BAB) containing donkey antiserum to a vaccine strain of S. typhi. Other salmonella species sharing O serogroup antigens with S. typhi also produced haloes when streaked in pure culture on SS-antiserum agar but not on BAB-antiserum agar. One hundred and forty-one consecutive faecal specimens were cultured on SS-antiserum agar. Results with this method were concordant with those of established isolation techniques on specimens from six of seven suspected carriers of S. typhi.

Ten other salmonellas were isolated from the faecal specimens but only S. faviana, like S. typhi a serogroup-D organism, yielded false-positive haloes on antiserum agar. The antiserum-agar technique offers promise as a means of screening for S. typhi in faecal cultures.

Penelope Fox provided expert technical assistance and Inelle Reynolds valuable secretarial service. Carl E. Frasch contributed several helpful insights. We are particularly indebted to John C. Feeley, Center for Disease Control, Atlanta, Georgia, for determining salmonella-antibody titres on the S. typhi strain Ty 2 antiserum.