Serratia marcescens Outbreak in Mexico City

Serratia marcescens is a Gram-negative rod belonging to the Enterobacteriaceae family. This opportunistic pathogen has been the cause of epidemics in hospitals due to its high level of resistance to antimicrobials. This study investigated the characteristics of a Serratia marcescens outbreak in the Instituto Nacional de Pediatría of Mexico City. The outbreak was studied using epidemiological analysis and molecular biology techniques. The samples were isolated from newborn infants of different services, and VITEK identified all clinical isolates. The biochemical profile of the biotype and the biogroup was determined using P. Grimont and F. Grimont’s method with a single carbon source. The production of prodigiosin and hemolysis was also determined, and the sensitivity test was carried out using a Kirby–Bauer system with disc diffusion. The genotyping was done on 27 strains by PFGE. All the strains belonged to biogroup A8 and biotype A5 and were multiresistant to several antibiotics but were susceptible to amikacin, gentamicin, trimethoprim/sulfamethoxazole, and especially Imipenem. The PFGE showed it was the exact clone, and all strains had an identical pattern A. The strains presented hemolysis and produced prodigisin when cultured at 30 °C but not at 37 °C. It is essential to characterize the temperature at which S. marcescens produces prodigiosin because it has been identified as an antimicrobial that affects different organisms. Our findings underscore the importance of precautionary methods in hospital settings.