Antimicrobial Resistance of Listeria monocytogenes Strains Isolated from Humans, Animals, and Food Products in Russia in 1950-1980, 2000-2005, and 2018-2021

Listeria monocytogenes from Food Products and Food Associated Environments: Antimicrobial Resistance, Genetic Clustering and Biofilm Insights

Listeria monocytogenes, a foodborne pathogen, exhibits high adaptability to adverse environmental conditions and is common in the food industry, especially in ready-to-eat foods. L. monocytogenes strains pose food safety challenges due to their ability to form biofilms, increased resistance to disinfectants, and long-term persistence in the environment. The aim of this study was to evaluate the presence and genetic diversity of L. monocytogenes in food and related environmental products collected from 2014 to 2022 and assess antibiotic susceptibility and biofilm formation abilities. L. monocytogenes was identified in 13 out of the 227 (6%) of samples, 7 from food products (meat preparation, cheeses, and raw milk) and 6 from food-processing environments (slaughterhouse-floor and catering establishments). All isolates exhibited high biofilm-forming capacity and antibiotic susceptibility testing showed resistance to several classes of antibiotics, especially trimethoprim-sulfamethoxazole and erythromycin. Genotyping and core-genome clustering identified eight sequence types and a cluster of three very closely related ST3 isolates (all from food), suggesting a common contamination source. Whole-genome sequencing (WGS) analysis revealed resistance genes conferring resistance to fosfomycin (fosX), lincosamides (lin), fluoroquinolones (norB), and tetracycline (tetM). In addition, the qacJ gene was also detected, conferring resistance to disinfecting agents and antiseptics. Virulence gene profiling revealed the presence of 92 associated genes associated with pathogenicity, adherence, and persistence. These findings underscore the presence of L. monocytogenes strains in food products and food-associated environments, demonstrating a high virulence of these strains associated with resistance genes to antibiotics, but also to disinfectants and antiseptics. Moreover, they emphasize the need for continuous surveillance, effective risk assessment, and rigorous control measures to minimize the public health risks associated to severe infections, particularly listeriosis outbreaks. A better understanding of the complex dynamics of pathogens in food products and their associated environments can help improve overall food safety and develop more effective strategies to prevent severe health consequences and economic losses.

Distribution and Antimicrobial Resistance Characterization of Listeria monocytogenes in Poultry Meat in Jiading District, Shanghai

To investigate the distribution, contamination status, and antibiotic resistance of Listeria monocytogenes in four types of retail poultry meat, including chicken, duck, goose, and pigeon, sold in Jiading District, Shanghai, a total of 236 retail poultry meat samples were collected, and L. monocytogenes isolates were obtained for identification and antibiotic susceptibility testing against 14 common antibiotics. Forty-one L. monocytogenes isolates were detected from the 236 retail poultry meat samples, with detection rates of 24.47%, 19.44%, 14.75%, and 4.44% in chicken, goose, duck, and pigeon meat, respectively. Among refrigerated, frozen, and room temperature samples, refrigerated poultry had the highest detection rate at 25.40%, while frozen poultry had the lowest at 13.33%. The detection rate of L. monocytogenes in chicken meat differed significantly between the storage temperatures, while no significant differences were found for other poultry types. No significant differences in detection rates were observed between different retail locations or packaging methods. Isolates exhibited complete resistance to cefoxitin (FOX) and increasing resistance over time to tetracycline (TET) and clindamycin (CLI), while low levels of resistance were found for penicillin (PEN), oxacillin (OXA), and erythromycin (ERY). Resistance to ERY and TET suggests the potential for multidrug resistance. Significant differences in antibiotic resistance profiles were observed among L. monocytogenes from the various poultry types. In summary, contamination status and antibiotic resistance profiles differed among retail chicken, duck, goose, and pigeon meat sold and the resistance rate of strains continues to increase in Jiading District, Shanghai. Targeted control measures should be implemented to reduce the emergence of resistant strains, as retail conditions had minimal impact on L. monocytogenes prevalence in poultry meat.

A South African Perspective on the Microbiological and Chemical Quality of Meat: Plausible Public Health Implications

Meat comprises proteins, fats, vitamins, and trace elements, essential nutrients for the growth and development of the body. The increased demand for meat necessitates the use of antibiotics in intensive farming to sustain and raise productivity. However, the high water activity, the neutral pH, and the high protein content of meat create a favourable milieu for the growth and the persistence of bacteria. Meat serves as a portal for the spread of foodborne diseases. This occurs because of contamination. This review presents information on animal farming in South Africa, the microbial and chemical contamination of meat, and the consequential effects on public health. In South Africa, the sales of meat can be operated both formally and informally. Meat becomes exposed to contamination with different categories of microbes, originating from varying sources during preparation, processing, packaging, storage, and serving to consumers. Apparently, meat harbours diverse pathogenic microorganisms and antibiotic residues alongside the occurrence of drug resistance in zoonotic pathogens, due to the improper use of antibiotics during farming. Different findings obtained across the country showed variations in prevalence of bacteria and multidrug-resistant bacteria studied, which could be explained by the differences in the manufacturer practices, handling processes from producers to consumers, and the success of the hygienic measures employed during production. Furthermore, variation in the socioeconomic and political factors and differences in bacterial strains, geographical area, time, climatic factors, etc. could be responsible for the discrepancy in the level of antibiotic resistance between the provinces. Bacteria identified in meat including Escherichia coli, Listeria monocytogenes, Staphylococcus aureus, Campylobacter spp., Salmonella spp., etc. are incriminated as pathogenic agents causing serious infections in human and their drug-resistant counterparts can cause prolonged infection plus long hospital stays, increased mortality and morbidity as well as huge socioeconomic burden and even death. Therefore, uncooked meat or improperly cooked meat consumed by the population serves as a risk to human health.

Antimicrobial Susceptibility Profile of Listeria monocytogenes Isolated from Meat Products: A Systematic Review and Meta-Analysis

The objective of this study was to conduct a systematic review to comprehensively understand antimicrobial resistance (AMR) in Listeria monocytogenes (LM) isolated from meat and meat products. The study was performed following the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Published articles from 2000 to 2022 were collected from six widely used online databases, including AGRICOLA, PubMed, Web of Science (WoS), Scopus, Cochrane Library, and CINAHL-EBSCO. Prevalence rates and AMR of pathogen isolates were analyzed using MedCalc software, including the I2 statistic and Cochrane Q test for heterogeneity. Sensitivity analysis, subgroup analysis, and meta-regression were conducted to analyze potential sources of heterogeneity at a 95% significance level. The distribution and prevalence of multidrug resistance (MDR) were examined using a random-effect model. The pooled frequency of bacterial MDR was 22.97% (95% confidence interval [CI] = 14.95-32.13). The studies exhibited high heterogeneity (I2 = 94.82%, 95% CI = 93.74-95.71, p < 0.0001). Furthermore, the most prevalent antibiotics resistance found in the majority of included studies were tetracycline, clindamycin, penicillin, ampicillin, and oxacillin (I2 = 86.66%, 95% CI = 73.20-93.36, p < 0.0001). This meta-analysis provides a comprehensive understanding of AMR in LM isolates, and the results indicate that none of the variable factors, including sampling location, sampling size, or methodology, significantly influenced the outcome of LM isolates resistant to multidrug.

ARGs Detection in Listeria Monocytogenes Strains Isolated from the Atlantic Salmon (Salmo salar) Food Industry: A Retrospective Study

Among bacterial foodborne pathogens, Listeria monocytogenes represents one of the most important public health concerns in seafood industries. This study was designed as a retrospective study which aimed to investigate the trend of antibiotic resistance genes (ARGs) circulation in L. monocytogenes isolates identified (in the last 15 years) from Atlantic salmon (Salmo salar) fresh and smoked fillets and environmental samples. For these purposes, biomolecular assays were performed on 120 L. monocytogenes strains collected in certain years and compared to the contemporary scientific literature. A total of 52.50% (95% CI: 43.57-61.43%) of these samples were resistant to at least one antibiotic class, and 20.83% (95% CI: 13.57-28.09%) were classified as multidrug resistant. Concerning ARGs circulation, tetracycline (tetC, tetD, tetK, tetL, tetS), aminoglycoside (aadA, strA, aacC2, aphA1, aphA2), macrolide (cmlA1, catI, catII), and oxazolidinone (cfr, optrA, poxtA) gene determinants were majorly amplified. This study highlights the consistent ARGs circulation from fresh and processed finfish products and environmental samples, discovering resistance to the so-called critical important antimicrobials (CIA) since 2007. The obtained ARGs circulation data highlight the consistent increase in their diffusion when compared to similar contemporary investigations. This scenario emerges as the result of decades of improper antimicrobial administration in human and veterinary medicine.

Occurrence and Multidrug Resistance in Strains of Listeria monocytogenes Recovered from the Anaerobic Co-Digestion Sludge Contained in a Single Stage Steel Biodigester: Implications for Antimicrobial Stewardship

L. monocytogenes is a zoonotic foodborne pathogen with inherent adaptability to tolerate environmental and physiological stresses, thereby causing severe disease outbreaks. Antibiotic resistant foodborne pathogens are a challenge to the food industry. A total of 18 samples were pooled from a bio-digester co-digesting swine manure/pinewood sawdust, and evaluated for the occurrence of bacterium plus total viable counts using the spread plate method. The recovered bacterial isolates were presumptively identified by growth on selective medium and confirmed by biochemical characterisation, leading to the isolation of 43 L. monocytogenes. The isolates were characterized based on their susceptibility to antibiotics via the Kirby-Bauer disc diffusion technique against a panel of 14 antibiotics. Equally, the multiple antibiotic resistance (MAR) index was calculated, and MAR phenotypes generated. The bacterial counts were between 102 and104 cfu/mL. Complete susceptibility (100%) was demonstrated to ampicillin, gentamicin and sulfamethoxazole, which are the drugs of choice in the treatment of listeriosis. In addition, intermediate sensitivity occurred at 25.58% to cefotaxime, and the highest resistance (51.16%) was exhibited against nalidixic acid. The MAR index ranged from 0 to 0.71. Overall, 41.86% of the Listeria isolates displayed multidrug resistance, with 18 different MAR phenotypes, demonstrating CIP, E, C, TET, AUG, S, CTX, NA, AML, NI as the greatest MAR phenotype. It can be concluded that the isolates yielding MAR > 0.2 originated from the farm, where antibiotics had been in routine use. Therefore, strict monitoring of antibiotics use in the farm is crucial to mitigate further increase in antibiotic resistance amongst these bacterial isolates.

Prevalence and Antimicrobial Resistance of Virulent Listeria monocytogenes and Cronobacter sakazakii in Dairy Cattle, the Environment, and Dried Milk with the In Vitro Application of Natural Alternative Control

This study aims to detect the prevalence and antimicrobial resistance of Listeria monocytogenes and Cronobacter sakazakii in three dairy households and dried milk from different suppliers, and evaluate the antimicrobial effect of rose water, rose, and orange essential oils. In total, 360 samples were collected from cattle, the environment, and dried milk (n = 30). Antimicrobial activity was evaluated with twofold microtube dilution and the time-kill method. L. monocytogenes was identified in all households (13.3%) with a prevalence in the range of 5.8–17.5%, while C. sakazakii was identified in one household (5.3%). The former and latter pathogens were highly isolated from the feces at 20% and 2.5% and bedding at 12.5% and 1.6%, respectively. L. monocytogenes was isolated only from milk at 7.5%, but C. sakazakii was not detected in either milk or dried milk. L. monocytogenes strains were screened for virulence genes (iap, hylA, and actA). All strains were positive for the iap gene, while for hlyA and actA, the percentages were (35.4% 16.6%, respectively). L. monocytogenes strains showed high resistance against sulfamethoxazole–trimethoprim (100%), followed by gentamicin, penicillin, and imipenem (95.8%, 95.8%, and 91.6%, respectively). All C. sakazakii strains were susceptible to all tested antibiotics. The bactericidal activity of orange oil was the strongest, appeared after 1 h for both pathogens, followed by rose oil and then rose water.

An Exploration of Listeria monocytogenes, Its Influence on the UK Food Industry and Future Public Health Strategies

Listeria monocytogenes is a Gram-positive intracellular pathogen that can cause listeriosis, an invasive disease affecting pregnant women, neonates, the elderly, and immunocompromised individuals. Principally foodborne, the pathogen is transmitted typically through contaminated foods. As a result, food manufacturers exert considerable efforts to eliminate L. monocytogenes from foodstuffs and the environment through food processing and disinfection. However, L. monocytogenes demonstrates a range of environmental stress tolerances, resulting in persistent colonies that act as reservoirs for the reintroduction of L. monocytogenes to food contact surfaces and food. Novel technologies for the rapid detection of L. monocytogenes and disinfection of food manufacturing industries have been developed to overcome these obstacles to minimise the risk of outbreaks and sporadic cases of listeriosis. This review is aimed at exploring L. monocytogenes in the UK, providing a summary of outbreaks, current routine microbiological testing and the increasing awareness of biocide tolerances. Recommendations for future research in the UK are made, pertaining to expanding the understanding of L. monocytogenes dissemination in the UK food industry and the continuation of novel technological developments for disinfection of food and the food manufacturing environment.

Synthetic oxepanoprolinamide iboxamycin is active against Listeria monocytogenes despite the intrinsic resistance mediated by VgaL/Lmo0919 ABCF ATPase

Background

Listeriosis is a food-borne disease caused by the Gram-positive Bacillota (Firmicute) bacterium Listeria monocytogenes. Clinical L. monocytogenes isolates are often resistant to clinically used lincosamide clindamycin, thus excluding clindamycin as a viable treatment option.

Objectives

We have established newly developed lincosamide iboxamycin as a potential novel antilisterial agent.

Methods

We determined MICs of the lincosamides lincomycin, clindamycin and iboxamycin for L. monocytogenes, Enterococcus faecalis and Bacillus subtilis strains expressing synergetic antibiotic resistance determinants: ABCF ATPases that directly displace antibiotics from the ribosome and Cfr, a 23S rRNA methyltransferase that compromises antibiotic binding. For L. monocytogenes strains, either expressing VgaL/Lmo0919 or lacking the resistance factor, we performed time-kill kinetics and post-antibiotic effect assays.

Results

We show that the synthetic lincosamide iboxamycin is highly active against L. monocytogenes and can overcome the intrinsic lincosamide resistance mediated by VgaL/Lmo0919 ABCF ATPase. While iboxamycin is not bactericidal against L. monocytogenes, it displays a pronounced post-antibiotic effect, which is a valuable pharmacokinetic feature. We demonstrate that VmlR ABCF of B. subtilis grants significant (33-fold increase in MIC) protection from iboxamycin, while LsaA ABCF of E. faecalis grants an 8-fold protective effect. Furthermore, the VmlR-mediated iboxamycin resistance is cooperative with that mediated by the Cfr, resulting in up to a 512-fold increase in MIC.

Conclusions

While iboxamycin is a promising new antilisterial agent, our findings suggest that emergence and spread of ABCF ARE variants capable of defeating next-generation lincosamides in the clinic is possible and should be closely monitored.

Distribution of antimicrobial resistance among clinical and food Listeria monocytogenes isolated in Moscow in 2019–2021

Objective. To determine the current state-of-art of acquired resistance to antimicrobial drugs among L. monocytogenes strains associated with listeriosis in humans and food contamination in Moscow. Materials and Methods. We used 39 L. monocytogenes strains isolated in Moscow in 2019–2021 from clinical material (n = 24) and food (n = 15). Resistance to 12 antibiotics of the first and second lines of defense was studied using disk-diffusion method. The parameters recommended for L. monocytogenes were used to interpret the results; in the absence of recommendations for L. monocytogenes, the criteria for Staphylococcus aureus and/or Enterococcus spp. were used. Results. All strains were susceptible to ampicillin, benzylpenicillin, erythromycin, vancomycin, imipenem, linezolid, and the amoxicillin/clavulanic acid. Resistance was observed to gentamicin (23%) as well as to meropenem, trimethoprim/sulfamethoxazole and ciprofloxacin (5%, 74% and 28% of strains, respectively). A total of 15 strains with multiple antibiotic resistance were identified (13 and 2 isolates were resistant to three and four antibiotics, respectively). Simultaneous resistance to trimethoprim/sulfamethoxazole, ciprofloxacin and levofloxacin was observed in 9 strains, 6 strains were resistant to gentamicin and trimethoprim/sulfamethoxazole, including 3 strains – to gentamicin, trimethoprim/sulfamethoxazole, levofloxacin, and 2 strains – to gentamicin, trimethoprim/sulfamethoxazole, ciprofloxacin. Comparison of the growth inhibition zones by ampicillin and benzylpenicillin in the studied strains with historical data on the strains isolated in Russia in 1950–1980 showed a significant downward shift in the size of growth inhibition zones. Comparison of the distribution of strains with different diameters of growth inhibition zones depending on the source of isolation did not show significant differences between clinical strains and strains of food origin isolated in 2019–2021. Conclusions. A wide spread of acquired resistance was shown among L. monocytogenes strains of clinical and food origin isolated in Moscow in 2019–2021. Despite the fact that all strains were susceptible to penicillins, the distribution of growth inhibition zone diameters showed a significant shift towards decreasing sensitivity to ampicillin and benzylpenicillin in strains isolated in 2019–2021 compared with L. monocytogenes strains isolated in Russia before 1980.