Investigation of carbapenemase genes and molecular epidemiology of Enterobacteriaceae strains isolated between 2010-2014 in a university hospitals

Abstract

The worldwide spread of carbapenemase producing Enterobacteriaceae isolates has become a major threat of public health. This worrisome situation leads the development of new methods for carbapenemase screening, detection, prevention of spread and epidemiological data collection as mandatory. In this study, it was aimed to investigate existence and distribution of carbapenemase-encoding genes (CEGs) among carbapenem-resistant Enterobacteriaceae isolated from various clinical samples in Ankara University Faculty of Medicine, Ibni Sina Hospital, Central Microbiology Laboratory between June 2010-May 2014 and detect their clonal relationship. A total of 112 non-repetitive Enterobacteriaceae isolates which were intermediate or resistant to ertapenem were identified by using Phoenix (BD Diagnostic Systems, Sparks, USA) automated microbiology system. After DNA extraction from the isolates, 11 carbapenemase-encoding genes (CEGs) (blaIMP, blaVIM, blaSPM, blaKPC, blaNDM, blaOXA-48, blaGIM, blaSIM, blaAIM, blaDIM ve blaBIC) were detected with PCR. The clonal relationship among the isolates was determined by PFGE method following digestion with Xbal DNA macrorestriction endonuclease. Among 112 isolates Klebsiella pneumoniae was the most frequent (n= 79, 70.5%) bacteria followed by Escherichia coli (n= 15, 13.4%), Enterobacter cloacae (n= 10, 8.9%), Enterobacter aerogenes (n= 4, 3.6%) and Klebsiella oxytoca (n= 4, 3.6%) respectively. blaOXA-48 was the most frequent gene detected. Among 83 (74.1%) isolates blaOXA-48 was detected alone and in 7 (6.3%) of the isolates it was identified with blaVIM gene coexistence. blaVIM gene was identified as the second most frequent CEG among the isolates. blaVIM gene was detected positive in 9 (8%) isolates. blaNDM gene was identified in 2 (1.8%) isolates. Ten of the K.pneumoniae isolates with identical PFGE pattern were named as pulsotype B. These isolates were found to be similar in terms of isolate location, isolation dates, antibiotic resistance patterns and the carbapenemase genes they carry, and are considered to be potential outbreak isolates originated from intensive care units. On the other hand CEGs were found in the clinical samples obtained from five out-patients suggesting that community-acquired infections may also arise due to carbapenemase producing Enterobacteriaceae in our country where blaOXA-48 producers are endemic. According to this study, blaOXA-48 producing gram negative bacteria were frequent in our hospital. The prevalance of blaVIM gene among metallo-beta-lactamases and coexistence with blaOXA-48 gene was remarkable. The frequency of blaNDM producing isolates in our hospital was not detected as high yet. In this study, the identification of carbapenemase producing bacteria as outbreak strains in our hospital indicated that cross-sectional surveillance for carbapenemase-producing bacteria from each patient was valuable in terms of early diagnosis of outbreaks.