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Here, we describe a nosocomial cluster of OXA-48 K pneumoniae, which lends support to a proactive rather than a reactive infection control policy for control of CPE.
Since 2010, carbapenem-resistant Enterobacteriaceae (CRE) have regularly been clinically cultured at Tan Tock Seng Hospital (TTSH), a 1,500-bed teaching hospital in Singapore. When CRE is identified from clinical cultures, the patient is isolated in a single room with contact precaution comprising apron and gloves on entering the patient's room and dedicated equipment for routine medical and nursing care (ie, stethoscope, sphygmomanometer, and thermometer). Index patient's movement throughout the hospital is traced using an electronic Infection Control and Epidemiology Surveillance System (ICESS). Patients in the same ward as the index patient are pre-emptively placed on contact precaution and screened for CRE with 1 sample of rectal swab. Movements to and from the wards are restricted until screening has been completed except for discharges, transfers to intensive care units, and essential procedures. All patients identified as CPE carriers are tagged electronically and identified during subsequent admissions and outpatient clinic visits. A conventional multiplex polymerase chain reaction (PCR) incorporating specific primers targeting blaNDM, blaKPC, and blaOXA-48-like is routinely done on all clinical isolates of Enterobacteriaceae that are meropenem nonsusceptible.
In July 2013, a 75-year-old female patient was admitted for an infected sacral ulcer. She had multiple comorbidities without any recent travel history. She was antibiotic experienced with multiple past hospitalizations at various institutions in Singapore. The admission blood cultures were negative. She underwent bone biopsy 5 days later and became febrile on the same day. Repeat blood cultures and bone biopsy cultures grew carbapenem-resistant Citrobacter koseri. This isolate was found to harbor blaOXA-48. Fifty patients across 3 wards who were epidemiologically linked to her were identified and screened using the modified Centers for Disease Control and Prevention broth method (Centers for Disease Control and Prevention, Atlanta, GA). Three carriers of carbapenem-resistant K pneumoniae were identified, of which 2 patients, A and B, tested positive for OXA-48. Repetitive element palindromic polymerase chain reaction (rep-PCR) fingerprinting was performed to determine clonal relatedness of the carbapenem-resistant K pneumoniae. rep-PCR primers enterobacterial repetitive intergenic consensus (ERIC) 1R (5'-ATGTAAGCTCCTGGGGATTCAC-3') and ERIC 2 (5'-AGTAAGTGACTGGGGTGAGCG-3') were used for amplification with HotStar Taq Plus Master Mix Kit (Qiagen, Hilden, Germany). Amplified DNA fragments were separated on 1.5% ethidium-bromide stained agarose gel, and gel images were analyzed with Bio-Numerics software (version 5.1; Bio-Numerics, Sint-Martens-Latem, Belgium) by calculating cluster analysis using the band-based Dice method to illustrate pairwise similarities among all isolates and the dendrogram-type unweighted-pair group method using average linkages. Band position tolerance of 1.00% was used.
To determine possible transmission route among these 3 patients, we charted overlap of medical equipment used for routine care and all health care workers (HCWs) with close contact. Although patients A and B did not share any medical equipment, there were 38 separate instances in which they shared HCWs. Surprisingly, patients A and B did not share HCWs or medical equipment with the index patient. There was possible horizontal transmission of OXA-48 between patients A and B unrelated to the index case confirmed by rep-PCR genotyping showing that the OXA-48-producer from patients A and B were clonal but distinct from OXA-48 in the index patient (Fig 1). Without HCW screening for CRE, we could not confirm the possibility of a HCW being a common source for the clonal OXA-48-positive isolate.
This is the first report of blaOXA-48-positive Enterobacteriaceae in Singapore and provides evidence for its spread to Southeast Asia.
We were unable to narrow down the source of these isolates. Continuous surveillance did not reveal any further isolation of blaOXA-48-positive Enterobacteriaceae in our center. International travel was associated with importation of blaOXA-181-positive K pneumoniae to Singapore in the past,
but we found no such association with this cluster. The admission prevalence of CRE at TTSH was about 0.9%, and the majority of these was CPE from a recent point prevalence survey. The incidence of CPE has been increasing steadily since 2010 despite aggressive infection control measures. Average hand hygiene compliance rate at TTSH hovers around 45%, marginally higher than the international average of about 38.7%.
it is unclear whether an institution should adopt a reactive approach, involving contact screening after CPE detection, or a proactive approach, which aims to identify and contain CPE before symptomatic manifestation.