Molecular Analysis of the Antibiotic Resistant NDM-1 Gene in Clinical Isolates of Enterobacteriaceae.

BACKGROUND

The emergence of the New Dehli metallo-beta-lactamase (NDM) gene in Enterobacteriaceae is responsible for multidrug resistance responsible for severe infections and serious morbidity in patients. Our study aimed to define the molecular characteristics and antibiogram of the NDM-1 producing Enterobacteriaceae.

METHODS

We isolated 370 individual enterobacteria from the clinical specimens collected from the two tertiary hospitals in Sakaka, Saudi Arabia. Bacterial isolation was performed using standard microbiological techniques and the Phoenix and Microscan WalkAway Plus automated analyzers. Bacterial strains were characterized by phenotypic methods and PCR, and DNA sequencing was used for the molecular characterization of NDM genes.

RESULTS

The blaNDM gene was detected among the 68 members of the Enterobacteriaceae including a single case of rarely reported Cedecea lapagei. Of these 68, 43 isolates (63.2%) were blaNDM-1 and 25 (36.8%) were blaNDM variants. A statistically significant relationship between the NDM-1 and Klebsiella pneumoniae (p = 0.004) was seen, and the relationship between the NDM variants was significantly associated with Citrobacter freundii (p = 0.02) and Escherichia coli (p = 0.03). The in vitro minimum inhibitory concentrations (MICs) of NDM-producing Enterobacteriaceae revealed a very high rate of antibiotic resistance against several groups of antibiotics. These bacterial strains were less resistant to two aminoglycosides, gentamicin (39; 57.3%) and amikacin (27; 39.7%), and showed minimum resistance to tigecycline (25; 36.8%).

CONCLUSIONS

The emergence of a large number of NDM-1 enterobacteria in our study identifies a substantial public concern, both within hospitals and the wider community, and leaves us a narrow choice of therapeutic options: the aminoglycosides, co-trimoxazole, and tigecycline.