Background: Pseudomonas aeruginosa (P. aeruginosa) predominated in hospitals.
Methods: In order to determine the source of the outbreak and take effective measures to prevent the spread, we tested their relationships between the strains. 97 P. aeruginosa samples were analyzed by multiple-locus variablenumber tandem repeat (VNTR) analysis (MLVA) method. In order to identify a minimal subset that could provide high discrimination, we evaluated the ability of various VNTR sets.
Results: The result showed all of the 11 loci displayed high discrimination, and the lowest loci was ms223 (h = 0.59). The 97 strains were all discriminated (HGDI = 1.0000). The top 7-locus set produced a HGDI value of 1.0000, which was the same as the 11-locus set. The 4-locus set had a HGDI value of 0.9972 with a clustering rate of 11.3%. The strains were divided into four groups based on the phylogenetic clustering and genotypic characteristics. There were obvious differences among the four groups regarding the drug-resistance patterns of Imipenem, Ciprofloxacin, Ceftazidime, Levofloxacin, Meropenem, Piperacillin, Cefepime, Aztreonam (p < 0.05).
Conclusions: In conclusion, the transmission of the strains was not found in this study. The 7-locus set yielded a high discrimination, while for an easier and more robust MLVA scheme, the number of markers can be reduced to 4 loci of ms212, ms211, ms213, and ms142. These four strains from four inpatients in the same ward displayed the same drug resistance spectrum. The MLVA genotype results showed the four strains had the same gene structures. The four patients were from the same treatment group. They showed the IMP-1 allele and belonged to the aac (6′)-I type, and there was a deletion of the OprD2 gene in four strains, supporting the MLVA results in suggesting that they are similar.