Antimicrobial resistance in foodborne <i>Salmonella enterica</i> isolates in the Republic of Belarus

Introduction. Antimicrobial resistance is a global public health concern. Salmonella spp., which can be transmitted to humans through contaminated food, are among the most important foodborne pathogens worldwide. Materials and methods. The antimicrobial resistance of 358 bacterial isolates collected from food and water in the Republic of Belarus (Belarus) in 20182021 was studied by analyzing phenotypic and genotypic characteristics of antibiotic bacterial resistance. MALDI-TOF mass spectrometry was used to classify and identify bacteria. Phenotypic antimicrobial susceptibility of bacteria was measured by the minimum inhibitory concentration method using a Sensititre automated bacteriological analyzer and the disk diffusion test for 45 antimicrobial agents. Antimicrobial resistance genes in multidrug-resistant Salmonella isolates were identified by whole-genome sequencing. Results. The in vitro testing of phenotypic bacterial susceptibility showed high susceptibility to fluoroquinolones (97.2%), third-generation cephalosporins (93.9%), carbapenems (98.0%), ampicillin (81.8%), aminoglycosides (97.5%), tetracyclines (87.5%), chloramphenicol (93.8%), trimethoprim/sulfamethoxazole (co-trimoxazole) (95.3%) and colistin (85.2%). It was found that the antibiotic resistance mechanism in S. enterica was associated with the presence of genes blaTEM-1B (82%), blaTEM-1C (7.7%), blaSHV-12 (2.6%), blaDHA-1 (2.6%), blaCMY-2 (7.7%), qnrB2 (9.1%), qnrB4 (9.1%), qnrB5 (9.1%), qnrB19 (72.7%), aac(6)-Ib-cr (9.1%), aac(6)-Iaa (100%), aadA1 (13.2%), aadA2 (8.8%), tetB (74.3%), tetA (25.7%), tetM (2.9%), tetD (28.6%), mcr-9 (1.5%). Conclusion. All the bacterial isolates were phenotypically susceptible to first-line antibiotics used in treatment of salmonellosis: fluoroquinolones and third-generation cephalosporins. The whole-genome sequencing of multidrug-resistant Salmonella isolates (19.0%) detected resistance genes for 9 groups of antibiotics: aminoglycosides (100%), beta-lactams (57.4%), fluoroquinolones (16.2%), tetracyclines (51.5%), macrolides (1.5%), phenicols (30.4%), trimethoprim (13.0%), sulfonamides (47.8%) and colistin (1.4%). Thus, epidemiological surveillance of the Salmonella spread through the food chain is of critical importance for the monitoring of antimicrobial resistance among foodborne Salmonella

Killer Whales and Marine Mammal Trends in The North Pacific—A Re-Examination of Evidence for Sequential Megafauna Collapse and the Prey-Switching Hypothesis

Springer et al. (2003) contend that sequential declines occurred in North Pacific populations of harbor and fur seals, Steller sea lions, and sea otters. They hypothesize that these were due to increased predation by killer whales, when industrial whaling’s removal of large whales as a supposed primary food source precipitated a prey switch. Using a regional approach, we reexamined whale catch data, killer whale predation observations, and the current biomass and trends of potential prey, and found little support for the prey-switching hypothesis. Large whale biomass in the Bering Sea did not decline as much as suggested by Springer et al., and much of the reduction occurred 50–100 yr ago, well before the declines of pinnipeds and sea otters began; thus, the need to switch prey starting in the 1970s is doubtful. With the sole exception that the sea otter decline followed the decline of pinnipeds, the reported declines were not in fact sequential. Given this, it is unlikely that a sequential megafaunal collapse from whales to sea otters occurred. The spatial and temporal patterns of pinniped and sea otter population trends are more complex than Springer et al. suggest, and are often inconsistent with their hypothesis. Populations remained stable or increased in many areas, despite extensive historical whaling and high killer whale abundance. Furthermore, observed killer whale predation has largely involved pinnipeds and small cetaceans; there is little evidence that large whales were ever a major prey item in high latitudes. Small cetaceans (ignored by Springer et al.) were likely abundant throughout the period. Overall, we suggest that the Springer et al. hypothesis represents a misleading and simplistic view of events and trophic relationships within this complex marine ecosystem