Prevalence and Molecular Typing of Colistin-Resistant Pseudomonas aeruginosa (CRPA) Among β-Lactamase-Producing Isolates: A Study Based on High-Resolution Melting Curve Analysis Method

BACKGROUND: The frequency and production of β-lactamase enzymes may be different in colistin-resistant Pseudomonas aeruginosa (CRPA) strains compared to susceptible strains. The purpose of this study was to investigate the relationship between colistin resistance and β-lactamase enzymes in different Sequence Types (ST) of P. aeruginosa. METHODS: A total of 101 P. aeruginosa isolates were collected from different samples. The antimicrobial susceptibilities of the bacterial isolates were examined by disk diffusion and MIC E-test methods. Also, real-time PCR and high-resolution melting curve analysis (HRMA) assay were performed to detect the resistance genes. RESULTS: Out of the 101 P. aeruginosa isolates, four isolates (3.96%) were resistant to colistin. Also, 39 isolates (38.61%) were considered as MDR, and eight isolates (7.92%) were considered as XDR. Further, 25 (24.75%) and 26 isolates (25.74%) were produced ESBL and carbapenemase enzymes, respectively. According to HRMA results, four isolates (3.96%) were positive for pmrA, three isolates (2.97%) were positive for mcr-1, 25 isolates (24.75%) were positive for blaTEM, 24 isolates (23.76%) were positive for blaSHV, 26 isolates (25.75%) were positive for blaKPC, and 23 isolates (22.77%) were positive for blaIMP genes. Furthermore, ST108 and ST250 showed the highest distribution in P. aeruginosa isolates. Also, ST217, ST1078, and ST3340 were reported as novel types in CRPA strains. CONCLUSION: Concerns about the prevalence of CRPA strains should be taken seriously. Also, our results showed that the mcr-1 gene plays a vital role in the distribution of ESBL and KPC-producing P. aeruginosa strains.