title: A simultaneous outbreak of Serratia marcescens and Klebsiella pneumoniae in a neonatal intensive care unit.
abstract: We describe two concurrent outbreaks of Serratia marcescens and Klebsiella pneumoniae in a neonatal intensive care unit (NICU). Over a 16-month period, a total of 27 infants were either colonized (N=14) or infected (N=13). There were 15 cases of S. marcescens and 11 cases of K. pneumoniae. Both micro-organisms were involved in one fatal case. Seven preterm babies developed septicaemia, two had bacteraemia, three had respiratory infections and one had purulent conjunctivitis. The S. marcescens and K. pneumoniae isolates were investigated by three molecular methods: enterobacterial repetitive intergenic consensus polymerase chain reaction (PCR), arbitrary primed PCR with M13 primer, and random amplification of polymorphic DNA. Different patterns were found in the 16 S. marcescens epidemic isolates from 16 newborn infants. The major epidemic-involved genotype was linked to the first nine cases and this was subsequently replaced by different patterns. Eight different typing profiles were also determined for the 13 K. pneumoniae isolates from 12 newborn infants. Four K. pneumoniae bacteraemic strains proved to be identical. In conclusion, the typing results revealed that two different micro-organisms (S. marcescens and K. pneumoniae) were simultaneously involved in invasive nosocomial infections in preterm newborns. Two simultaneous clusters of cases were documented. Heterogeneous genotypes among both species were also demonstrated to be present in the NICU at the same time. A focal source for both micro-organisms was not identified but cross-transmission through handling was probably an important route in this outbreak. Strict adherence to handwashing policies, cohorting, isolation of colonized and infected patients, and rigorous environmental hygiene were crucial measures in the containment of the epidemic.
authors.affiliation: Unit of Microbiology and Virology, Policlinico of Modena, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Casolari
authors.forename: M
authors.initials: M
authors.lastname: Pecorari
authors.forename: G
authors.initials: G
authors.lastname: Fabio
authors.forename: S
authors.initials: S
authors.lastname: Cattani
authors.forename: C
authors.initials: C
authors.lastname: Venturelli
authors.forename: L
authors.initials: L
authors.lastname: Piccinini
authors.forename: M G
authors.initials: MG
authors.lastname: Tamassia
authors.forename: W
authors.initials: W
authors.lastname: Gennari
authors.forename: A M T
authors.initials: AM
authors.lastname: Sabbatini
authors.forename: G
authors.initials: G
authors.lastname: Leporati
authors.forename: P
authors.initials: P
authors.lastname: Marchegiano
authors.forename: F
authors.initials: F
authors.lastname: Rumpianesi
authors.forename: F
authors.initials: F
authors.lastname: Ferrari
mesh_terms: D016470:Bacteremia / Q000382:microbiology; D015373:Bacterial Typing Techniques; D003231:Conjunctivitis / Q000382:microbiology; D003428:Cross Infection / Q000453:epidemiology*; D016172:DNA Fingerprinting; D004269:DNA, Bacterial / Q000032:analysis / Q000378:metabolism; D004196:Disease Outbreaks; D005260:Female; D006235:Hand Disinfection; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature; D007235:Infant, Premature, Diseases / Q000453:epidemiology*; D017053:Infection Control; D007363:Intensive Care Units, Neonatal; D007710:Klebsiella Infections / Q000453:epidemiology*; D007711:Klebsiella pneumoniae / Q000145:classification / Q000235:genetics / Q000302:isolation & purification; D008297:Male; D017720:Molecular Epidemiology; D010356:Patient Isolation; D011014:Pneumonia / Q000382:microbiology; D018805:Sepsis / Q000382:microbiology; D016868:Serratia Infections / Q000453:epidemiology*; D012706:Serratia marcescens / Q000145:classification / Q000235:genetics / Q000302:isolation & purification
chemical_list: D004269:DNA, Bacterial