Antimicrobial Resistance and Biofilm Formation of Escherichia coli Isolated from Pig Farms and Surroundings in Bulgaria

Abstract

Escherichia coli (E. coli) is a ubiquitous microorganism with pathogenic and saprophytic clones. The objective of this study was to evaluate the presence, virulence, antibiotic resistance and biofilm formation of E. coli in three industrial farms in Bulgaria, as well as their adjacent sites related to the utilization of manure (feces, wastewater in a separator, lagoons, means of transport, and soils). The isolation of single bacterial cultures was performed via standard procedures with modifications, and E. coli isolates were identified via matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and polymerase chain reaction (PCR). The disk diffusion method was used to assess antimicrobial resistance, and PCR was used to detect genes for antibiotic resistance (GAR) (qnr, aac(3), ampC, blaSHV/blaTEM and erm) and virulence genes (stx, stx2all, LT, STa, F4 and eae). The protocol of Stepanović was utilized to measure the biofilm formation of the isolates. A total of 84 isolates from different samples (n = 53) were identified as E. coli. Almost all demonstrated antimicrobial resistance, and most of them demonstrated resistance to multiple antibiotics from different classes. No virulence genes coding the Shiga toxin or enterotoxins or those associated with enteropathogenicity were detected. No GAR from those tested for quinolones, aminoglycosides and macrolides were found. However, all isolates that were resistant to a penicillin-class antibiotic (56) had β-lactamase-producing plasmid genes. All of them had ampC, and 34 of them had blaTEM. A total of 14 isolates formed strongly adherent biofilms. These results in a country where the use of antibiotics for growth promotion and prophylaxis in farms is highly restricted corroborate that the global implemented policy on antibiotics in human medicine and in animal husbandry needs revision.

Rabbits as a Reservoir of Multidrug-Resistant Escherichia coli: Clonal Lineages and Public Health Impact

“…Stronger biofilm-forming strains were also found in poultry isolates [43]. In Bulgaria, isolates from three industrial farms formed strongly adherent biofilms, indicating the presence of E. coli in various meat products [44]. The presence of resistance to commonly used antimicrobials, coupled with the occurrence of MDR strains and strong biofilm formation ability, is alarming.…”

Preliminary Data on Escherichia coli, Yersinia enterocolitica, and Other Bacteria, as Well as Absent African Swine Fever Virus in the Gut Microbiota of Wild Mice and Voles from Bulgaria

“…E. coli strains had very little resistance level-only to some aminoglycosides of some the isolates. This is noteworthy, since E. coli is an ESBL producer and easily gains resistance to carbapenems, polymyxins, and quinolones through horizontal gene transfer [53,54].…”

Unveiling Antibiotic Resistance, Clonal Diversity, and Biofilm Formation in E. coli Isolated from Healthy Swine in Portugal

“…Although E. coli is less common in healthcare-associated biofilms, it remains a potential cause of sepsis. Biofilm formation is considered a pathogenic factor that plays an important role in antimicrobial resistance, leading to reduced permeability and contributing to reduced susceptibility to antimicrobial agents and invasive infections [ 21 , 22 ]. The ability to form biofilms also facilitates the spread of resistance genes in the environment, and bacteria can exchange genetic elements to facilitate the dissemination of resistance traits [ 23 ].…”