Distribution of Serratia marcescens serotypes in cancer patients.

A study of 1314 patients with malignancies was made to determine the prevalence of Serratia marcescens in surveillance, diagnostic, and environmental cultures. Sera obtained from a commercial source were used to determine serotypic distributions of the S. marcescens strains isolated during a 51-month period. S. marcescens was isolated from 19% of patients with haematological neoplasms, from 5% of patients with lymphoma, and from 6% of those with solid tumours. Among carriers, rectal cultures were the commonest source in patients with lymphoma (32%); rectal and gingival cultures in patients with leukaemia (43% and 39%, respectively), and gingival cultures in patients with solid tumours (30%). Bacteraemias (.07%) were infrequent sources. Although seldom isolated from environmental or food samples, S. marcescens may occasionally be abundant in fresh fruit and vegetables. Serotyping of 220 strains of S. marcescens demonstrated 38 distinct antigenic types. The predominant serotype, O14:H12, was present in the upper respiratory tract of half of the persons who carried this serotype. Serotyping is a readily reproducible method of subspeciating S. marcescens; it can be satisfactorily used as an epidemiological tool.