Study of the prevalence of antibiotic-resistant bacterial strains of clinical origin in the region of Sétif and molecular characterization of their resistance

Abstract

Antibiotic resistance (AR) is among the leading global health concerns to date. In our study, 402 strains were collected from 7 medical diagnostic laboratories and 3 government hospitals in Sétif region over three years (2021-2023). First, the identification of 326 clinical community samples and 76 hospitalized samples, isolated from different specimens, was carried out using microbiological and biochemical tests and confirmed by API gallery. This analysis identified 10 species belonging to Gram negative bacteria (GNB) and 3 species belonging to Gram positive bacteria (GPB). E. coli was the predominant pathogen among GNB (50%) while S. aureus was the most common GPB (7.7%). The majority of these strains were found in urine samples from adult patients. Antibiotic susceptibility tests and MICs were performed according to CA-SFM recommendations. A significant proportion of the identified strains exhibited high resistance rates against first-line antibiotics commonly used in the treatment of various bacterial infections including penicillins and cephalosporins, but a substantial resistance was recorded against imipenem in E. coli (49.8%) and Proteus species (32.1%). Similarly, tobramycin and gentamycin exhibited limited effectiveness against P. aeruginosa, Enterobacter spp., (20% to 100%) and all GPB. MDR strains represented 56% of all tested isolates, followed by XDR (26.1%). Amikacin was the most effective antibiotic. Among K. pneumoniae isolates, 66.6% were classified as hypervirulent K. pneumoniae (hvKp) based on the string test. In S. aureus species, 61.3% were methicillin-resistant S. aureus (MRSA), while 9.7% exhibited the constitutive macrolide-lincosamide-streptogramin B (CMLSB) phenotype, and 16.1% displayed the inducible MLSB (IMLSB) phenotype, as determined by the D-test. Different virulence factors were tested in our pathogenic strains. Biofilm formation was assessed in microtiter plates using crystal violet dye, while hemolysin, protease, lecithinase, and lipase enzyme production were determined using plates containing human blood, skimmed milk, and egg yolk, respectively. Overall, 88.1% of strains were biofilm producers, with the majority (64.9%) exhibiting a weak ability to produce biofilms. XDR strains exhibited the highest percentage of strong biofilm producers (47.6%).