Abstract
Background: The rapid spread of multidrug-resistant gram-negative bacteria, particularly an increase in carbapenem-resistant gram-negative bacteria, has led to a critical level of multi-drug resistance in clinics. Colistin is considered to be the last line of defense against Gram-negative bacteria.
Objective: To investigate the genetic characteristics and antimicrobial resistance patterns of four mcr-1 (mobile colistin resistance) Escherichia coli （E. coli）isolated from various sources in Hainan Province, tropical China, and determine their genetic relationships with both domestic and global strains.
Methods: Samples were collected from swimming pools, marine beaches, and beach personnel in Haikou and Sanya, Hainan Province, China. E. coli isolates were obtained, multilocus sequence typing (MLST) was performed, and the resistance genes of mcr family were amplified by polymerase chain reaction (PCR). The mobile sequences, antimicrobial resistance genes, phenotype and virulence genotypes of the mcr-1 strains were analyzed. The phylogenic analyses were conducted to investigate the relationships between the mcr-1 E. coli strains and those in NCBI database.
Results: In the current study, the mcr-1 resistance gene was detected in 4 trains, accounting for 2.94% (4/136) of the total. The 4 strains of E. coli were from freshwater swimming pool, pool wall, seawater and human body. Among the four strains, the minimum inhibitory concentration (MIC) of polymyxin was 8mg/L, except for one strain showed low-level resistance at 4mg/L. All four strains showed complete resistance to ampicillin, three were resistant to compound sulfamethoxazole and chloramphenicol, and all strains were sensitive to other common antibiotics. The virulence genes of cfaA, cfaB, cfaC and cfaD/cfaE were detected in all E. coli strains. The insertable sequence IS3 was the most widely distributed type. Three isolates were identified as ST987, whereas the isolate from marine sources was identified as ST24. Comparison of the core genes of the strains indicated that the four strains were closely related to the Chrysomya.sp from Northern Thailand.
Conclusions: The four mcr-1 genes can mediate low and medium levels of colistin resistance, which dissemination within the population and environment. It is significant to trace the source of multidrug-resistant bacteria in recreational water that are in direct contact with humans, and reduce the risks to human health through supervision.
Copyright
© 2024, Author(s). This open-access article is available under the Creative Commons Attribution 4.0 (CC BY 4.0) International License (https://creativecommons.org/licenses/by/4.0/), which allows for unrestricted use, distribution, and reproduction in any medium, provided that the original work is properly cited.