High rate of aminoglycoside resistance in CTX-M-15 producing Klebsiella pneumoniae isolates in Tehran, Iran.

OBJECTIVE

To determine the prevalence of extended-spectrum beta lactamases (ESBLs), the bla(CTX-M) genes, and aminoglycoside modifying enzymes genes in clinical isolates of Klebsiella pneumoniae (K. pneumoniae).

METHODS

We collected 200 nonduplicate clinical isolates of K. pneumoniae in hospitals in Tehran, Iran. We determined antibacterial susceptibility and confirmed ESBL production via the disk diffusion and minimum inhibitory concentration (MIC) methods. We identified bla(CTX-M) and aminoglycoside modifying enzymes genes via polymerase chain reaction (PCR).

RESULTS

We detected 72 (36.0%) ESBL-positive K. pneumoniae, in which the bla(CTX-M-15) was dominant (62.5%). A total of 54.0% of isolates were resistant to at least 1 tested aminoglycoside; also, we detected aac(6')-Ib in 42.5% of isolates and aac(3)-IIa in 35.1% of them. We observed a high rate of aminoglycoside-resistant genes (71.0%) among bla(CTX-M-15)-carrying isolates.

CONCLUSION

We report that CTX-M-15 is the dominant type of CTX-M, which associates with entities that have high aminoglycoside resistance. Continuous surveillance and monitoring of this entity are needed because the codissemination of multiple drug-resistant genes with K. pneumoniae may become a serious therapeutic problem.