Antibiotic resistance and virulence genes in Enterococcus species isolated from raw and processed seafood

Enterococcus spp. in fish: Analysis of the presence and resistance in samples from Tri-City, Poland

The growing concern over antibiotic resistance in foodborne pathogens necessitates comprehensive assessments of its prevalence and associated risks in various food products. The present study aimed to assess the occurrence of Enterococcus spp. in samples of fish purchased at various points of sale in the Tricity region. The selection of products (n = 74) was based on their availability and included both fish caught in the Baltic region and products imported from, Vietnam, China, Norway, and European Union (EU) countries. For bacterial isolation, samples were inoculated into selective broth, and the growth of enterococci was assessed based on turbidity. Positive cultures were confirmed by a change in color in bromocresol purple broth and were isolated on Slanetz-Bartley agar. Bacteria were present in all tested samples regardless of the degree of raw material processing as follows: frozen (F)- 55%, fresh/raw (FS)- 70.6%, thawed (DF)- 30%, smoked (S)- 50%, and the packaging methods, modified atmosphere packaging (MAP)- 34.4%, unit packaging (UP)- 75%, and sold in bulk (SB)- 76.9%, with an overall frequency of occurrence of 58.1%. The number of bacteria ranged from not detected to 4.28-log cfu/g, with the lowest mean values for thawed fish and those packed in MAP. Tests conducted on 24 strains isolated from samples showed their varied sensitivity to tetracyclines. Single cases of multidrug resistance of the tested strains were also observed. The conducted statistical analysis did not show statistically significant differences in the count of enterococci based on the origin, degree of processing, or packaging (p < 0.05). Moreover, differences in strain sensitivity to ampicillin were observed. Detected cases of resistance, especially to tetracycline, require careful monitoring and action to limit the health risks associated with resistant bacterial strains in food products.

Bacterial abscesses in whitespotted bamboo sharks (Chiloscyllium plagiosum) in managed care

Sixteen whitespotted bamboo sharks (Chiloscyllium plagiosum) with histologically similar bacterial abscesses were submitted to Northwest ZooPath from nine zoo and aquarium institutions over a 17-year period. These abscesses were characterized by inflammatory cell infiltrates and necrosis with intralesional small, Gram-positive, acid-fast negative, cocci bacteria. The clinical presentation, histologic findings, and culture results indicate that Enterococcus faecalis is a relatively common cause of these lesions in whitespotted bamboo sharks. This organism also provides a treatment challenge due to its inherent antibiotic-resistant properties and ability to form biofilms, confounding the host's immune response. Enterococcus faecalis represents an important cause for abscess formation and cellulitis in captive whitespotted bamboo sharks.

Resistance Profiles and Virulence Determinants in Biofilm-Forming Enterococcus faecium Isolated from Raw Seafood in Bangladesh

Pathogenic, antibiotic-resistant, and biofilm-forming bacteria can be transferred to humans through the consumption of contaminated seafood. The present study was carried out to determine antibiotic resistance profiles and virulence determinants in biofilm-forming Enterococcus faecium isolated from seafood in Bangladesh. A total of 150 seafood samples, including shrimp (n = 50), crabs (n = 25), and marine fish (n = 75), were screened using cultural, staining, biochemical, polymerase chain reaction (PCR), Congo red (CR), and disk diffusion (DD) assays. In PCR, E. faecium was detected in 27.3% (41/150; CI95% 20.8; 34.9) of samples, where marine fish (34.7%, CI95% 24.9; 45.9) had the highest prevalence (p < 0.05) compared to crabs (32%, CI95% 17.2; 51.6) and shrimp (14%, CI95% 7.0; 26.1). Thirty-two (78.1%, CI95% 63.3; 88.0) of the E. faecium isolates were determined to be biofilm formers in the CR test, where 43.9% (18/41, CI95% 29.9; 59.0) and 34.2% (14/41, CI95% 21.6; 49.5) of the isolates were strong and intermediate biofilm formers, respectively. In PCR, virulence genes, i.e., pil (100%), ace (92.7%), agg (68.3%), fsrA (65.9%), gelE (63.4%), sprE (53.7%), fsrB (51.2%), and fsrC (43.9%), were detected in E. faecium isolates. All the E. faecium isolates were phenotypically resistant to ≥3 antimicrobial categories and ≥3 antibiotics, including WHO-classified reserve antibiotics linezolid (70.7%) and fosfomycin (19.5%). Moreover, the multiple antibiotic resistance index ranged up to 0.8, showing resistance to ten antibiotics and eight antibiotic classes. In this study, the prevalence of virulence genes and antibiotic resistance was significantly greater (p < 0.05) in strong biofilm-forming E. faecium strains as compared to strains with intermediate and non-biofilm-forming abilities. As far as we know, this study, for the first time in Bangladesh, determined antibiotic resistance and detected virulence genes in biofilm-forming E. faecium isolated from seafood samples. The data from this study could play a significant role in evaluating potential health hazards linked to the ingestion of uncooked or minimally processed seafood.

Prevalence and antimicrobial resistance profiles of Vibrio spp. and Enterococcus spp. in retail shrimp in Northern California

Shrimp is one of the most consumed seafood products globally. Antimicrobial drugs play an integral role in disease mitigation in aquaculture settings, but their prevalent use raises public health concerns on the emergence and spread of antimicrobial resistant microorganisms. Vibrio spp., as the most common causative agents of seafood-borne infections in humans, and Enterococcus spp., as an indicator organism, are focal bacteria of interest for the monitoring of antimicrobial resistance (AMR) in seafood. In this study, 400 samples of retail shrimp were collected from randomly selected grocery stores in the Greater Sacramento, California, area between September 2019 and June 2020. The prevalence of Vibrio spp. and Enterococcus spp. was 60.25% (241/400) and 89.75% (359/400), respectively. Subsamples of Vibrio (n = 110) and Enterococcus (n = 110) isolates were subjected to antimicrobial susceptibility testing (AST). Vibrio isolates had high phenotypic resistance to ampicillin (52/110, 47.27%) and cefoxitin (39/110, 35.45%). Enterococcus were most frequently resistant to lincomycin (106/110, 96.36%), quinupristin-dalfopristin (96/110, 87.27%), ciprofloxacin (93/110, 84.55%), linezolid (86/110, 78.18%), and erythromycin (58/110, 52.73%). For both Vibrio and Enterococcus, no significant associations were observed between multidrug resistance (MDR, resistance to ≥3 drug classes) in isolates from farm raised and wild caught shrimp (p > 0.05) and in isolates of domestic and imported origin (p > 0.05). Whole genome sequencing (WGS) of a subset of Vibrio isolates (n = 42) speciated isolates as primarily V. metschnikovii (24/42; 57.14%) and V. parahaemolyticus (12/42; 28.57%), and detected 27 unique antimicrobial resistance genes (ARGs) across these isolates, most commonly qnrVC6 (19.05%, 8/42), dfrA31 (11.90%, 5/42), dfrA6 (9.5%, 4/42), qnrVC1 (9.5%, 4/42). Additionally, WGS predicted phenotypic resistance in Vibrio isolates with an overall sensitivity of 11.54% and specificity of 96.05%. This study provides insights on the prevalence and distribution of AMR in Vibrio spp. and Enterococcus spp. from retail shrimp in California which are important for food safety and public health and exemplifies the value of surveillance in monitoring the spread of AMR and its genetic determinants.