Successful control of a neonatal outbreak caused mainly by ST20 multidrug-resistant SHV-5-producing Klebsiella pneumoniae, Greece

Abstract

Background: Extended spectrum beta-lactamase-producing Klebsiella pneumoniae (ESBL-Kp) infection can cause significant morbidity and mortality in neonates. We investigated a nosocomial ESBL-Kp outbreak in a neonatal intensive care unit (NICU) of the University Hospital of Larissa (UHL), Central Greece.

Methods: A total of sixty-four ESBL-Kp were studied; twenty six isolates were recovered from the NICU and were compared with thirty-eight randomly selected isolates from different wards of the hospital during the period March- December 2012. All isolates were characterized by antimicrobial susceptibility testing, ESBL-production by double-disk synergy test, molecular typing using BOX-PCR, whereas selected isolates were further characterized by beta lactamase and virulence gene content, multilocus sequence typing and phylogenetic analysis. All neonates affected by ESBL-Kp were put under strict contact isolation, along with appropriate infection control measures.

Results: The outbreak strain of ST20 multidrug-resistant SHV-5-producing K. pneumoniae was identified in all infected (n = 13) and three colonized neonates. A novel ST (ST1114) was also identified among SHV-5 producers (n = 10) recovered from nine colonized infants, but it was not related with ST20. Both STs were identified only in the NICU and not in other wards of the hospital. No ESBL-Kp were isolated from the hands of the nursing staff and the environment. Although we were not able to identify the source of the outbreak, no ESBL-Kp were isolated in the NICU after this period and we assumed that the outbreak was successfully controlled. All neonates received parenteral nutrition and most of them were delivered by caesarean section and showed low gestational age (<32 weeks) and low birth weights (<1500 g).

Conclusion: According to our knowledge, this is the first description of an outbreak of multidrug-resistant SHV-5 producing K. pneumoniae assigned to ST20.

Figure 1

Neighbor-joining tree of the STs of the 32 representative ESBL-Kp. For each isolate, the MLST ST, the BOX-PCR profile and the beta-lactamase content are indicated.

Figure 2

Time-course of the outbreak of ST20 ESBL-Kp. The sex (F: female, M: male) and the infection (I) or colonization (C) status of each infant is indicated. Case 4, indicated with a different colour scheme, has died. The time of first isolation of ST20 SHV-5 producers for each infant is indicated with an asterisk.