Food borne microbial pathogens of cultured aquatic species

Bacterial Communities and Antibiotic Resistance of Potential Pathogens Involved in Food Safety and Public Health in Fish and Water of Lake Karla, Thessaly, Greece

Bacterial communities, microbial populations, and antibiotic resistance of potential pathogens in the water and fish (Cyprinus carpio, flesh and gut) from different areas (A1, A2 and A3-A1 was linked with river water, A2 with cattle activity, and A3 with waters of a spring after heavy rains) of Lake Karla (Thessaly, Central Greece) were investigated. The isolated bacteria were identified using Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) and were tested for resistance in 21 antibiotics. The microbiota composition of fish flesh was also studied using 16S amplicon-based sequencing Serratia fonticola and several species of Aeromonas (e.g., Aeromonas salmonicida, Aeromonas bestiarium, Aeromonas veronii, etc.) exhibited the highest abundances in all studied samples, while the microbiota profile between the three studied areas was similar, according to the culture-dependent analysis. Of them, S. fonticola was found to be resistant in the majority of the antibiotics for the water and fish (gut and flesh), mainly of the areas A1 and A2. Regarding 16S metabarcoding, the presence of Serratia and Aeromonas at genus level was confirmed, but they found at very lower abundances than those reported using the culture-dependent analysis. Finally, the TVC and the rest of the studied microbiological parameters were found at acceptable levels (4 log cfu/mL or cfu/g and 2-4 log cfu/mL or cfu/g, extremely low levels of E. coli/coliforms) in both water and fish flesh. Based on our findings, the water of Lake Karla would be used for activities such as irrigation, recreation and fishing, however, the development and implementation of a quality management tool for Lake Karla, to ensure environmental hygiene and prevention of zoonosis during the whole year, is imperative.

Detection of Zoonotic Bacteria and Paragonimus kellicotti in Red Swamp Crayfish (Procambarus clarkii) and the Assessment of Traditional Crayfish Boils

ABSTRACT

Studies of red swamp crayfish (Procambarus clarkii) outside of the United States confirm the presence of a variety of zoonotic pathogens, but it is unknown whether these same pathogens occur in P. clarkii in the United States. The U.S. commercial crayfish industry generates $200 million yearly, underscoring the need to evaluate this consumer commodity. The study objectives were to evaluate specific zoonotic pathogens present on P. clarkii from Alabama and Louisiana, states in the southeastern United States, and to determine the effectiveness of traditional food preparation methods to reduce pathogens. Experiment A evaluated the presence of Escherichia coli, Salmonella, Staphylococcus aureus, and Vibrio spp. in crayfish and environmental samples over a 2-month collection period (May to June 2021). Crayfish sampling consisted of swabbing the cephalothorax region; 15 samples were tested for E. coli, Salmonella, and S. aureus, and an additional 15 samples for Vibrio spp. Additionally, crayfish shipping materials were sampled. In experiment B, 92 crayfish were evaluated for Paragonimus kellicotti. Experiment C compared live and boiled crayfish for the presence of Vibrio spp. In experiments A and B, all 60 (100%) crayfish samples and 13 (81.25%) of 16 environmental samples showed growth characteristic of Vibrio spp. Three (5%) of 60 samples showed E. coli growth, with no statistical difference (P = 0.5536) between farms. P. kellicotti, Salmonella, and S. aureus were not recovered from any samples. In experiment C, all 10 (100%) of the live preboiled crayfish samples showed characteristic growth, whereas 1 (10%) of 10 samples of crayfish boiled in unseasoned water showed Vibrio growth (P < 0.0001). These results confirm that Vibrio spp. and E. coli may be present on U.S. commercial crayfish and that care should be taken when handling any materials that come into contact with live crayfish because they can potentially be contaminated.

HIGHLIGHTS

Modelling the effects of physicochemical variables and anthropogenic activities as ecological drivers of Plesiomonas shigelloides distribution and freshwaters quality

Spatio-temporal distribution of pathogens in freshwater is driven by environmental variables (EVs), natural, and human-induced activities and the spread of infections and disease outbreaks are triggered significantly by these processes. The role of EVs and anthropogenic activities on the distribution of Plesiomonas shigelloides is not well understood; hence this study aimed at modelling the effects of EVs and anthropogenic gradients on the densities of Plesiomonas in freshwaters and freshwater quality. Three freshwaters were sampled from February to December 2017. The EVs and Plesiomonas densities of the freshwaters were determined using standard techniques, while partial least square path modelling and correlation analysis were performed on the data collected. Factors underpinning the quality of the freshwaters were identified through principal component analysis (PCA). Most EVs fell within the bounds of recommended permissible limits except turbidity, TSS, salinity and TDS. Results revealed a significant increase of Plesiomonas densities with an increase in the magnitude of path coefficients and intensities of anthropogenic activities along the freshwaters. The distribution of Plesiomonas correlated with temperature (r = 0.69, p < 0.01), TSS (r = 0.30, p < 0.01), TBS (r = 0.28, p < 0.01), and BOD (r = 0.39, p < 0.01). Similarly, a significant correlation existed between conductivity and TDS (r = 0.97, p < 0.01) and salinity (r = 0.99, p < 0.01). Network analysis of EVs identified three closed networks essential for freshwaters quality and Plesiomonas distribution with nodes of variables under synergistic latent influences. Overall, PCA identified four drivers of the freshwater quality and in part, Plesiomonas density; namely, nutrient loading; thermal and organic pollutions, aesthetic pollution, and pH modulators. Higher component score indicated a greater impact of nutrient loading on the freshwater quality. The study concluded that Plesiomonas distribution is largely shaped by anthropogenic gradients and EVs in rivers, and these may play a major role in its dissemination along freshwater milieus.

Molecular cloning, recombinant expression and functional characterization of an antimicrobial peptide, Crustin from the Indian white shrimp, Fenneropenaeus indicus

Antimicrobial peptides (AMPs) comprise molecules that involve in the defense mechanism of various organisms towards pathogens such as bacteria, fungi, parasites and viruses. Crustins are generally defined as multi-domain cationic antimicrobial peptides containing one whey acidic protein (WAP) domain at the C-terminus as the functional unit. In this study, we identified and characterized a novel crustin homolog (Fi-Crustin2) with 354 bp fragment cDNA encoding 117 amino acids and an ORF of 100 amino acids with a net charge of +1 from the mRNA of F. indicus haemocytes. This study forms the second report of a crustin isoform from F. indicus. Blast analysis revealed that Fi-crustin2 exhibits similarity to shrimp crustins already reported. The active mature peptide has a molecular weight of 10.61 kDa and pI of 7.59 with a beta sheeted structure. The mature peptide was cloned into pET-32a(+) with a N-terminal hexa-histidine tag fused in-frame, and expressed in Escherichia coli, and the recombinant crustin, Fi-crustin2 inhibited the growth of Gram-negative bacteria with low MIC. All these features suggest that Fi-crustin2 is a potent antibacterial protein against Gram-negative bacteria and could play an important role in the innate immune mechanism of F. indicus.

Plesiomonas shigelloides Revisited

After many years in the family Vibrionaceae, the genus Plesiomonas, represented by a single species, P. shigelloides, currently resides in the family Enterobacteriaceae, although its most appropriate phylogenetic position may yet to be determined. Common environmental reservoirs for plesiomonads include freshwater ecosystems and estuaries and inhabitants of these aquatic environs. Long suspected as being an etiologic agent of bacterial gastroenteritis, convincing evidence supporting this conclusion has accumulated over the past 2 decades in the form of a series of foodborne outbreaks solely or partially attributable to P. shigelloides. The prevalence of P. shigelloides enteritis varies considerably, with higher rates reported from Southeast Asia and Africa and lower numbers from North America and Europe. Reasons for these differences may include hygiene conditions, dietary habits, regional occupations, or other unknown factors. Other human illnesses caused by P. shigelloides include septicemia and central nervous system disease, eye infections, and a variety of miscellaneous ailments. For years, recognizable virulence factors potentially associated with P. shigelloides pathogenicity were lacking; however, several good candidates now have been reported, including a cytotoxic hemolysin, iron acquisition systems, and lipopolysaccharide. While P. shigelloides is easy to identify biochemically, it is often overlooked in stool samples due to its smaller colony size or relatively low prevalence in gastrointestinal samples. However, one FDA-approved PCR-based culture-independent diagnostic test system to detect multiple enteropathogens (FilmArray) includes P. shigelloides on its panel. Plesiomonads produce β-lactamases but are typically susceptible to many first-line antimicrobial agents, including quinolones and carbapenems.

Microbiological quality of sushi from sushi bars and retailers

Sushi is a traditional Japanese food, mostly consisting of rice and raw fish. Fish is considered a healthy food, but as with other animal products, consumption of raw muscle incurs potential health risks such as ingestion of pathogenic bacteria or parasites. In this study, 250 sushi samples were analyzed for their microbiological status and the prevalence of pathogenic bacteria. A comparison was made between frozen sushi from supermarkets and fresh sushi from sushi bars. Aerobic mesophilic bacteria counts differed for sushi from these two sources, with means of 2.7 log CFU/g for frozen sushi and 6.3 log CFU/g for fresh sushi. The prevalence of Escherichia coli and Staphylococcus aureus was higher in the fresh samples. Salmonella was found in four (1.6%) of the sushi samples, and Listeria monocytogenes was found in three (1.2%) of the samples. These results indicate that the microbiological quality of industrially processed sushi is higher than that of freshly prepared sushi. The quality of freshly prepared sushi strongly depends on the skills and habits of the preparation cooks, which may vary.

Updated perspectives on emerging vibrios associated with human infections

This review describes the ecological, clinical and epidemiological features of emerging vibrios and discusses what laboratory methods are being used for the detection of pathogenic vibrios in clinical, environmental and food samples. After selecting articles illustrative of the current scientific research on pathogenic vibrios, the review focuses on the need for better insight into the risk factors of emerging infections to establish adequate prevention procedures.