Spread of Klebsiella pneumoniae isolates producing OXA-48 β-lactamase in a Tunisian university hospital.

Sir, The emergence and dissemination of Klebsiella pneumoniae isolates harbouring carbapenemases is a serious problem. Since the initial report of the OXA-48 enzyme in a K. pneumoniae isolate from Turkey in 2001, OXA-48 producers have been reported in many countries of the world. – 4 Current reports indicate that OXA-48 producers are widespread, mostly from Mediterranean countries as well as other countries in Europe. – 4 In North Africa, OXA-48 producers have been identified in Morocco and Tunisia. The outbreaks of OXA-48-producing K. pneumoniae isolates have been described in several cities in Turkey, once in the UK and recently in France. In the present report, we describe the spread of OXA-48 associated with CMY-4and CTX-M-14-producing K. pneumoniae clinical isolates in Sfax University Hospital. During a 6 month period (October 2009–March 2010), 153 clinical isolates of K. pneumoniae with reduced susceptibility to extended-spectrum cephalosporins and/or imipenem were recovered in Sfax University Hospital. Among these isolates, 21 (13.7%) produced the blaOXA-48 gene. These isolates were recovered from patients in eight different wards. The antibiogram determined by the disc diffusion method and MICs determined by agar dilution and interpreted according to European Committee on Antimicrobial Susceptibility Testing (EUCAST) revealed that all isolates were resistant to ticarcillin (MICs.2048 mg/L) (Table 1). All but one isolate were resistant to extended-spectrum cephalosporins, including cefotaxime (MICs 4–1024 mg/L), ceftazidime (MICs 0.5–256 mg/L) and cefepime (MICs 2–64 mg/L). All isolates but one (Kp11) were susceptible to imipenem (MIC901⁄42 mg/L; MIC range1⁄40.5–8 mg/L). This isolate, Kp11, was intermediate to imipenem but susceptible to extended-spectrum cephalosporins. However, all isolates were resistant to ertapenem (MIC901⁄48 mg/L; MIC range1⁄42–32 mg/L). The b-lactamase genes detected by PCR as described previously and sequencing in the 21 OXA-48-positive K. pneumoniae isolates were as follows: blaOXA-48 (1 isolate); blaOXA-48+blaCMY-4+ blaCTX-M-14 (14 isolates); blaOXA-48+blaCMY-4+blaCTX-M-14+blaOXA-1 (3 isolates); blaOXA-48+blaCMY-4+blaCTX-M-14+blaTEM-1 (1 isolate); blaOXA-48+blaCTX-M-14+blaOXA-1 (1 isolate); and blaOXA-48+blaCMY-4+blaCTX-M-15 (1 isolate). Transferability of the blaOXA-48 gene to Escherichia coli J53 was observed in 20 OXA-48-producing isolates. However, conjugation and electroporation experiments failed for Kp4, suggesting that in this isolate the blaOXA-48 gene might be chromosomally located. However, the blaOXA-48 gene was shown to be mostly plasmid-borne and associated with insertion sequence IS1999 but not integrons. Using a series of PCR primers, two IS1999 insertion sequences were found surrounding the blaOXA-48 gene in all our isolates, as found in the prototype OXA-48-positive K. pneumoniae 11978 isolate from Turkey. Molecular analysis of E. coli transconjugants showed that the blaOXA-48 and blaCMY-4 genes were detected on the same plasmid, explaining the resistance to b-lactams of the K. pneumoniae isolates and their transconjugants. Plasmid analysis showed Research letters