Molecular epidemiology and antibiotic resistance profiles of Mycobacterium and Nocardia species in patients with cancer: Detection of multidrug-resistant and extensively drug-resistant strains.

Patients with cancer are vulnerable to infections caused by mycobacteria and Nocardia. Antimicrobial agents are necessary to treat these infections, but extensive antibiotic use can lead to drug-resistant strains. Due to this issue, in the present study, we aimed to isolate, molecularly identify, prevalence, and assess the resistance genes in mycobacterial and nocardial isolates from patients with cancer. 79 clinical samples were obtained from patients with cancer which were referred to Mohammad Rasolallah hospitals in Shiraz. Initial identification was conducted through phenotypic and biochemical assays, followed by molecular confirmation using PCR amplification of the 16S rRNA and hsp65 genes. Genus and species determination was achieved through direct sequencing of the 16S rRNA gene. Drug susceptibility testing was carried out using the serial dilution method, adhering to the guidelines set by the Clinical and Laboratory Standards Institute (CLSI) in 2021. Out of 79 clinical samples, 17 isolates (21.51 %) were recovered and identified as Mycobacterium and Nocardia species through molecular and biochemical analyses. In our study, the most prevalent species were M. tuberculosis complex 6 (35.3 %) isolates, M. avium complex 3(17.64 %) isolates, M. terrae 2(11.76 %)isolates, N.cyriacigeorgica 2 (11.76 %) ‏ ‏isolates, N. nova, N. kroppenstedtii, M. arupense, and M. canariasense 1 (5/89 %) isolate each. The analysis of the resistance profile of isolates showed that the M. tuberculosis (MTB) isolates HM7 and HM9 showed multidrug-resistant (MDR), and the isolates HM11 and HM12 showed extensively drug-resistant (XDR) profile, M. avium showed MDR profile, while no resistance patterns were observed in the Nocardia isolates. Moreover, the results show that some of the MTB isolates ‏ ‏harbored katG, ermA, and rpoB resistance genes and M. avium isolates harbored katG and rpoB resistance genes. In conclusion, our results showed, that patients with cancer are vulnerable to infections caused by mycobacteria and Nocardia, moreover the emergence of antibiotic resistance further complicates the management of these infections, necessitating vigilant surveillance and the development of tailored treatment guidelines.