Biotyping of Serratia marcescens strains of clinical origin.

One hundred and ninety five Serratia marcescens strains of clinical origin isolated at the Children's Hospital of Mexico (Hospital Infantil de México) in 1978 and at the National Institute of Pediatrics (Instituto Nacional de Pediatría) in Mexico City in 1977 and from 1988 to 1989, were studied and compared. All strains were identified using the biotyping system described by Grimont and Grimont, without modification. The most numerous biogroup found was A5/8, and the frequencies of isolation of each biotype varied depending on the institution where it was isolated and the period of study.