Multidrug-resistant and hypervirulent Listeria monocytogenes in foods and food-processing environments in southern Brazil

Listeria monocytogenes is a major foodborne pathogen responsible for listeriosis, a severe disease with high fatality rates that typically requires antimicrobial therapy. This study aimed to characterize antimicrobial resistance and the presence of hypervirulence-associated LIPI-3 and LIPI-4 markers in L. monocytogenes from foods and food-processing environments in southern Brazil, and to evaluate the genetic relatedness of multidrug-resistant (MDR) isolates using Pulsed-Field Gel Electrophoresis (PFGE). Among 82 isolates, resistance was observed to clindamycin (CLI, 48.7 %), meropenem (MER, 29.3 %), sulfamethoxazole/trimethoprim (SUT, 29.3 %), rifampicin (RIF, 14.6 %), erythromycin (ERY, 10.9 %), tetracycline (TET, 8.5 %), streptomycin (STR, 7.3 %), and amikacin (AMK, 4.9 %). All tetracycline-resistant isolates carried the tetM gene (7/7), and 85.7 % (6/7) also carried the tetL gene. Among erythromycin-resistant isolates, the ermB gene was detected in 11.1 % (1/9). Fifteen isolates (18.3 %) showed multidrug resistance, with the ERY-CLI-RIF-MER-SUT-TET profile being the most prevalent. Regarding virulence, all 15 MDR isolates harbored LIPI-1 and LIPI-2 genes, whereas 60 % of these isolates carried at least one of the hypervirulence-associated pathogenicity islands, LIPI-3 or LIPI-4, or both. MDR L. monocytogenes showed distinct PFGE patterns (n = 15), indicating high genetic diversity, including among hypervirulent isolates. This study demonstrates the occurrence of L. monocytogenes isolates in foods and food-processing environments in southern Brazil that are resistant to clinically relevant antimicrobials, including multidrug resistance, and that also exhibit hypervirulent genotypes. The coexistence of antimicrobial resistance and hypervirulence in L. monocytogenes underscores the urgent need for continuous monitoring and control strategies to mitigate public health risks.