Rapid identification of international multidrug-resistant Pseudomonas aeruginosa clones by multiple-locus variable number of tandem repeats analysis and investigation of their susceptibility to lytic bacteriophages

Abstract

The objective of this study was to determine the genetic diversity of multidrug-resistant (MDR) Pseudomonas aeruginosa strains isolated over a period of 12 months in two French hospitals and to test their susceptibility to bacteriophages. A total of 47 MDR isolates recovered from hospitalized patients were genotyped using multiple-locus variable number of tandem repeats analysis. The genotypes were distributed into five clones (including 19, 5, 5, 3, and 3 isolates, respectively) and 12 singletons. Comparison to 77 MDR strains from three other countries, and MLST analysis of selected isolates showed the predominance of international MDR clones. The larger clone, CC235, contained 59 isolates displaying different antibiotic resistance mechanisms, including the presence of the GES1, VIM-2, VIM-4, and IMP-1 β-lactamases. Three newly isolated P. aeruginosa bacteriophages were found to lyse 42 of the 44 analyzed strains, distributed into the different clonal complexes. This pilot study suggests that systematic genotyping of P. aeruginosa MDR strains could improve our epidemiological understanding of transmission at both the local (hospital) and the national level and that phage therapy could be an alternative or a complementary treatment to antibiotics for treating MDR-infected patients.

Fig 1

Clustering analysis of 47 isolates from the Narbonne and Clamart hospitals. The dendrogram was produced in BioNumerics using MLVA data. Clones defined with an 80% cutoff are indicated by colors. The resistances to ten antibiotics are indicated on the right. R, resistant; S, susceptible; and I, intermediate. GM, gentamicin; TM, tobramycin; AK, amikacin; IMP, imipenem; MPM, meropenem; CAZ, ceftazidime; FEP, cefepime; CIP, ciprofloxacin; TZP, piperacillin-tazobactam; AZN, aztreonam.

Fig 2

Restriction pattern of the three bacteriophages A, B, and C. Genomic DNA digested by HindIII or BssHII was run on an agarose gel. M, size marker.