Can J Infect Dis Med Microbiol 2020 9;2020:9091360. Epub 2020 Oct 9.
Department of Clinical Laboratory, The First Affiliated Hospital of Kunming Medical University, Kunming 650032, China.
Background: The emergence of the NDM-1-positive () strains has led to limited therapeutic options for clinical treatment. Understanding the clinical characteristics, antimicrobial resistance, biofilm assay, and the virulence genes of these isolated strains is of great significance.
Methods: The polymerase chain reaction (PCR) was used to screen isolated NDM-1-positive . The clinical information of the patients was collected from medical records. The NDM-1-positive isolates were subjected to antimicrobial susceptibility testing and multilocus sequence typing. Sixty strains of NDM-1-negative isolated during the same period were collected as the control group for the virulence analysis. The virulence phenotype of the strains was preliminarily evaluated by the string test and crystal violet semiquantitative biofilm formation experiment. PCR combined with gene sequencing was used to detect common high toxicity capsule genes (K1, K2, K5, K20, K54, and K57) and common virulence-related genes ().
Results: In the 30 nonduplicated NDM-1-positive isolates, 43.33% (13/30) of the patients had a history of a stay in the neonatal intensive care unit (NICU). All of the isolates exhibited multidrug resistance. Nine STs were identified, 77% (10/13) strains from the NICU were ST11. The NDM-1-positive string tests were all negative, and 35% (21/60) NDM-1-negative were positive. The ratios of NDM-1-positive isolates biofilm formation ability according to strong, medium, and weak classification were 67%, 23%, and 10%, respectively. NDM-1-negative isolates were 60%, 25%, and 15%, respectively. There was no statistical difference between the two groups ( = 0.61, =0.2723). The virulence-associated genes with more than 80% of detection rates among the 30 NDM-1-positive isolates included (100%, 30/30), (93.33%, 28/30), (90%, 27/30), (83.33%, 25/30), and (90%, 27/30). and were detected at prevalence of 3.33% and 13.33%. and were not detected. In the NDM-1-negative , all other 14 virulence genes except were detected. After statistical analysis, and virulence genes, < 0.005, there was a statistical difference.
Conclusion: NDM-1-positive exhibited multidrug resistance, MLST typing is mainly ST11, there is small clonal dissemination in the NICU in the hospital, and the NDM-1-positive virulence genes carrier rate is lower than the NDM-1-negative virulence genes carrier rate.