Stenotrophomonas maltophilia de origem clínica: caracterização fenotípica e molecular da resistência a trimetoprima/sulfametoxazol e carbapenêmicos

Abstract

Stenotrophomonas maltophilia is an opportunistic microorganism and often associated with infections in immunocompromised patients hospitalized in critical units, related to exacerbation and loss of lung function in Cystic Fibrosis (CF) patients, contributing to morbi-mortality rates. Multidrug resistant strains is a clinical challenge. The aim of this study was to evaluate the antimicrobial resistance profile to the most antibiotics commonly used in S. maltophilia infection and investigate genes associated with resistance to trimethoprima/sulfamethoxazole and carbapenems. We analyzed 155 S. maltophilia isolates recovered from many clinical specimens, during January 2010 to April 2021. 112 (72.3%) and 43 (27.7%) isolates were obtained from patients without CF (NFC) and CF patients, repectivelly. In NFC group, most of all were obtained from respiratory secretions (95; 84.8%) followed by blood samples (10; 8.9%), while in CF group, all of them were from respiratory specimens. These data corroborate the higher prevalence of S. maltophilia in respiratory infections. The exclusive isolation in blood samples from NFC was expected since cases of bacteremias are unusual in CF, whose clinical follow-up is predominantly ambulatory. Using disk diffusion test, 155 S. maltophilia isolates was analyzed for trimethoprima-sulfamethoxazole (SXT), levofloxacin (LEV) and minocycline (MIN). Most of all were suscetible to antimicrobials tested, in both patients group, including isolates (n=9) from NFC patients with COVID-19. Just a single isolate from NFC group was resistant to SXT and LEV, and only one of the FC group was resistant to LEV. Minimal inhibitory concentration was performed using gradient diffusion test to SXT, LEV, MIN and ceftazidime (CAZ) for 32 (20.6%) isolates, obtained between 2014 to 2019. Five (15.6%) and 17 (53.1%) isolates showed an intermediate and resistance categories to CAZ, respectively. Among the resistance isolates, 43.7% presented high levels resistance (≥ 256 μg/mL). All isolates were susceptible to other antimicrobials. Despite the intrinsic resistance of S. maltophilia to carbapenems, we investigated the presence of genes encoding carbapenemases such as blaKPC, blaNDM and blaOXA-48like, by PCR, in order to verify a possible role of this microorganism as reservoir of these genes. PCR for sul1 gene, associated with SXT resistance, was also performed. All isolates were negative. The majority isolates showed high susceptible rates to all antimcirobial tested in our study. Despite that, it does not excluded the continuous monitoring of resistance profiles in our hospital, including clinical and environmental origins. Microbiological surveillance, including the resistance profile, allows development of an action plan for an outbreak control measures.