Large oligoclonal outbreak due to Klebsiella pneumoniae ST14 and ST26 producing the FOX-7 AmpC ss-lactamase in a Neonatal Intensive Care Unit.

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Large oligoclonal outbreak due to Klebsiella pneumoniae ST14 and ST26 producing the FOX-7 AmpC ss-lactamase in a Neonatal Intensive Care Unit.

J Clin Microbiol. 2013 Oct 2;

Authors: Arena F, Giani T, Becucci E, Conte V, Zanelli G, D'Andrea MM, Buonocore G, Bagnoli F, Zanchi A, Montagnani F, Rossolini GM

Abstract
A large outbreak caused by Klebsiella pneumoniae resistant to expanded-spectrum cephalosporins (ESCR-Kp) was observed in a neonatal intensive care unit (NICU) in central Italy. The outbreak involved 127 neonates (99 colonizations and 28 infections, with seven cases of sepsis and two deaths) over a period of more than two years (Feb 2008 - Apr 2010). Characterization of the 92 non-redundant isolates that were available for further investigation revealed that all of them but one produced the FOX-7 AmpC-type β-lactamase and belonged to either Sequence Type (ST) 14 or ST26. All the FOX-7 positive isolates were resistant to cefotaxime, ceftazidime and piperacillin-tazobactam, while 76% were susceptible to cefepime, 98% to ertapenem, 99% to meropenem and 100% to imipenem. The two carbapenem-nonsusceptible isolates had alterations in the genes encoding Outer Membrane Proteins k35 or k36, that resulted in truncated and likely not functional proteins. The outbreak was eventually controlled by reinforcement of infection control measures based on a multi-tiered interventional approach. This is the first report of a large NICU outbreak caused by ESCR-Kp producing an AmpC-type enzyme. This study demonstrates that AmpC-type producing strains can cause large outbreaks with a significant impact in terms of morbidity and mortality (mortality rate at 14 days was 28.5% for sepsis episodes), and underscores the role of laboratory-based surveillance and infection control measures to contain similar episodes.

PMID: 24088849 [PubMed - as supplied by publisher]