Molecular Epidemiology in Neonatal Pasteurellosis

Abstract

To the Editors: P asteurella multocida is a nonmotile, facultative anaerobic, bipolar staining, gram-negative coccobacillus. Humans can become asymptomatic carriers from animal contact and a source of transmission. Few studies have characterized P. multocida strains and confirmed animal and/or human exposure as the direct source of neonatal infection. A 25-day-old infant was admitted with P. multocida (Vitek, bioMérieux, Durham, NC) sepsis and meningitis with positive blood and cerebrospinal fluid cultures. He received a 21-day course of ampicillin (minimal inhibitory concentration < 0.12 μg/mL; Vitek, bioMérieux, Durham, NC) with complete resolution of symptoms during the first week of therapy. On follow-up appointment at 8 months of age, neurologic and developmental assessments were appropriate for his age. Surveillance investigation of close human and animal contacts was performed during the infant’s hospitalization. Throat cultures from the parents and vaginal cultures from the mother were negative for P. multocida. Mouth swabs obtained from both family dogs grew Pasteurella haemolytica. Mouth cultures from an outside cat grew P. multocida. Pulse-field gel electrophoresis (PFGE) and ribotyping analysis were performed at the Infectious Disease Research Laboratory, Christiana Health Care System. DNAs of the isolates recovered from the patient’s CSF and the oral specimens from household pets were digested with SmaI and examined by PFGE. Ribotyping analysis (RiboPrinter System, DuPont Qualicon, Wilmington, DE) of P. multocida strains isolated from the patient and the household cat demonstrated that the strain recovered from the cat was unrelated to the strain isolated from the patients’ cerebrospinal fluid. P. multocida neonatal sepsis and meningitis, although rare, are potentially preventable infections that remain associated with a significant morbidity and mortality in this age group. Most neonatal pasteurellosis cases reported in the English language literature are associated with animal exposure. Nonetheless, only 4 publications used genetic analysis to confirm that the recovered strains from animal contacts were in fact the same P. multocida strains responsible for the neonatal infections.1–4 One study used restriction fragment length polymorphism banding patterns derived from southern blotting and hybridization.3 The other studies used ribotying and/or PFGE to compare 16sRNA gene sequences from reference database with the isolates.1,2,4 Studies that used genetic techniques demonstrated identical strains in the household contacts and the affected infants. In our experience, detailed epidemiologic tracing of his parents and animal contacts failed to recover P. multocida, but in the household cat. DNA analysis by ribotyping and PFGE confirmed that the neonatal infection was caused by a different P. multocida strain, the 1 recovered from the animal. Holst et al5 characterized the clinical manifestations and epidemiology of P. multocida subspecies. In their series of 146 cases, P. multocida subspecies multocida was recovered from the 5 patients presenting with septicemia with or without known animal exposure. Of the 2 isolates recovered from CSF in patients with meningitis, 1 belonged to subspecies multocida and the other to subspecies septica. Animal studies suggest that P. multocida subspecies septica strains might have a greater affinity to cause central nervous system infections.6 Whether certain strains are more likely than others to cause sepsis and meningitis in newborns is unknown. Genetic analysis could assist to characterize the epidemiology and to better understand mechanisms of spread for this infection in neonates. This report emphasizes that DNA fingerprinting of recovered P. multocida isolates must be a requisite to confirm the link between exposure and infection. Andrew S. Wood, MD Department of Pediatrics Bryn Mawr Hospital Bryn Mawr, PA Elyse E. Foraker, BS MT (ASCP) Christiana Care Health Services Wilmington, DE Cecilia Di Pentima, MD, MPH Infectious Diseases Division Department of Pediatrics Vanderbilt University Nashville, TN