Multiple-Locus Variable Number Tandem Repeat Analysis of Klebsiella pneumoniae: Comparison with Pulsed-Field Gel Electrophoresis.

AIM: To assess whether multiple-locus variable-number tandem repeat analysis (MLVA) could replace pulsed-field gel electrophoresis (PFGE) for genotyping of Klebsiella pneumoniae, this study was conducted to compare the typeability, discriminatory power, and concordance of these methods.

MATERIALS AND METHODS: We used the nine variable number tandem repeat (VNTR) loci scheme to test its suitability for differentiating 114 ESBL-producing K. pneumoniae isolates collected from different clinical specimens in three hospitals of Tehran, Iran between April and December 2011. PFGE with XbaI was performed and the results were compared with those obtained by typing with MLVA.

RESULTS: MLVA and PFGE yielded 44 and 64 types, respectively. Simpson's Diversity Index of MLVA was 0.896 (a 95% confidence interval of 0.850-0.942) and of PFGE was 0.962 (a 95% confidence interval of 0.943-0.981). Congruence between PFGE and MLVA was low. The adjusted Wallace coefficient of PFGE to MLVA was 0.946; however, MLVA was less able to predict PFGE type (32.5%). A range of 2-12 alleles was identified at VNTR loci with Simpson's diversity values between 0.017 and 0.818.

CONCLUSION: MLVA is a PCR-based typing method and is much easier and more rapid in comparison to PFGE. These data indicate that the MLVA typing scheme used in this study is discriminative and reliable for typing of K. pneumoniae. However, optimization of the VNTR markers is required to improve the discriminatory power of the method.