Background
Carbapenem resistant Enterobacteriaceae (CRE) is a very important emerging threat to patient safety for its association with high rates of morbidity and mortality. In January 2013 a case of bacteraemia with Carbapenem resistant Klebsiella pneumoniae was isolated from a 24-bed ward in our hospital. Infection control department requested a maximum of 2 rectal swabs to be taken from each contact patient for the purpose of contact tracing.
Method
Rectal swabs were taken from patients in the same ward, during outpatient follow-up and readmission. The laboratory uses chromIDTM CARBA agar (CARB) (bioMérieux) for CRE screening and plate reading was done after 18-24hours incubation. All suspicious colonies were identified with API 20E (bioMérieux) and carbapenem resistance was confirmed using Meropenem Etest with breakpoint interpretation at ≥ 2μg/mL for resistant. Genotyping was confirmed with PCR by National Public Health Laboratory, Singapore.
Result
A total of 231 samples were received from January – April 2013, of which 8 (3.5%) were CRE positive; 7 Klebsiella pneumoniae and 1 Escherichia coli. All screening positive isolates shared similar minimum inhibition concentration (MIC) values of 24 to >32μg/mL for meropenem and blaOXA-181 genotype was detected as of index patient’s. ERIC2 PCR typing for the K.pneumoniae strains showed that they belong to the same clone.
Conclusion
The OXA-181 producing strain of Klebsiella pneumoniae that was isolated in our laboratory demonstrated high levels of carbapenem resistance unlike usual OXA producers, hence enabling the use of CARBA plate for screening this outbreak isolate. However, CRE with low level resistance might not grow on this plate, thus better screening procedures are necessary for their detection. Shortening of confirmation time would also allow the laboratory to provide better support for the containment of outbreaks.