Clariid catfish (Clarias spp.) are among the most widely cultured freshwater fish in Africa and Asia, yet consolidated evidence regarding parasitic infections and prevalence trends remains limited. This systematic review and meta-analysis synthesized cross-sectional studies reporting infections in clariid catfish identified through literature searches conducted between 2005 and 2024, with eligible studies published from 2008 to 2024. The review was registered in PROSPERO (CRD420251120588) and conducted in accordance with PRISMA 2020 guidelines. Nineteen eligible studies comprising 2878 examined fish were included. Six major parasite groups were identified, with cestodes, nematodes, and trematodes predominating across regions, whereas acanthocephalans and crustacean ectoparasites were reported infrequently. Mixed helminth infections were frequently reported, particularly in African freshwater systems, reflecting both the strong concentration of studies in Africa and recurrent reports of diverse parasite assemblages in these environments. Protozoan infections were nearly absent from the literature (1/19 studies), and no eligible studies documented bacterial, viral, or fungal prevalence, highlighting substantial gaps in pathogen surveillance. Meta-analysis of comparable datasets involving parasitic helminths and arthropods, while excluding protozoa because of insufficient data, yielded an overall pooled prevalence of 34.7% (95% CI: 24.1–46.0). Cestodes exhibited the highest pooled prevalence (41.2%; 95% CI: 22.2–61.7), followed by nematodes and trematodes, whereas crustacean ectoparasites consistently showed lower prevalence. High between-study heterogeneity (I² > 96%) reflected substantial geographic, ecological, and methodological variability. These findings highlight the strong African concentration of the available evidence base, substantial heterogeneity in reported prevalence that precludes simple generalizations across studies, and important gaps in pathogen surveillance, particularly for protozoan, bacterial, viral, and fungal infections. Strengthening parasite surveillance and integrated health management strategies will be essential for improving fish health, aquaculture productivity, and food security in Africa and other regions practicing clariid aquaculture.

Accurate water quality monitoring of microbial indicators hinges on understanding the impact of holding times and treatments on water sample results. This study examined interacting factors influencing holding times for fecal indicator bacteria (FIB) in water samples held for a range of times (0-216 h) under three storage treatments (i.e., Controlled Cold [∼4°C], Controlled Ambient [∼21°C], and Changing Conditions [∼4°C-21°C]). Four separate trials were conducted during 2016 using two distinct water supplies: river water (n = 2) and post-irrigation canal water (n = 2). Large carboys of water (n = 3/trial, ∼53L) were evenly divided into 500 mL aliquots for storage under different treatments (n = 105/treatment). Samples were processed in triplicate using standard membrane filtration for Escherichia coli and fecal coliforms. Linear regression with autocorrelation and Dunnett's test were used to analyze the concentration of FIB across holding times from baseline (T = 0). Canal water samples maintained FIB concentrations similar to T = 0 for at least 72 h under Controlled Cold; at least 48 h under Changing Conditions, and at least 30 h under Controlled Ambient treatments. By contrast, river water samples maintained concentrations similar to T = 0 at least 180 h without statistically significant changes under Controlled Cold, at least 72 h under Changing Conditions, and at least 36 h under Controlled Ambient treatments. Regardless of the treatments, river water samples were more stable than canal water samples, likely due to starting conditions. Holding times for water quality monitoring continues to be a multifaceted challenge and may warrant further exploration or more flexibility around regulatory requirements.

BackgroundAlthough various laboratory protocols exist for the detection of Shiga toxin-producing E. coli (STEC), the number of presumptive colonies selected per sample for confirmation remains a critical yet largely overlooked factor that is has not been standardized between investigators.ObjectivesOur study evaluated how the number of presumptive colonies selected for confirmation per fecal sample influences the probability to detect true positive samples, which when optimized can facilitate more accurate estimates of STEC prevalence in feces while simultaneously minimizing costs associated with confirming excessive numbers of colonies.MethodsAn experimental trial was first conducted using inoculated concentrations of E. coli O157:H7 (−1.1 to 4.3 log₁₀ CFU/g) and non-O157 STEC (−1.9 to 4.6 log₁₀ CFU/g), with up to 45 presumptive colonies selected for qPCR confirmation. In parallel, a dairy fecal longitudinal survey was conducted on 14 dairy farms in California to examine how the number of presumptive colonies selected per sample affected STEC prevalence estimates, using the 45-presumptive colony protocol as the benchmark method. Using colony-based positive predictive values (cPPV) generated from the experimental trial for CT-SMAC, Rainbow Agar O157, and CHROMagar STEC selective agars, the hypergeometric (HG) and binomial (BN) distributions were used to calculate the probability of diagnosing a sample as true positive (PrHG and PrBN, respectively) and the computation of the STEC prevalence for dairy fecal samples as a function of number of confirmed colonies.ResultsThe experimental trial comprised 126 spiked samples. Results showed that the high cPPV (~100%) values observed for all but the lowest bacterial concentrations (−1.1 log₁₀ CFU/g) for E. coli O157:H7 generated a > 90% probability of true positive detection (PrHG and PrBN) when as few as 3 to 4 presumptive colonies were selected. Selecting only 3–4 presumptive colonies yielded a model-predicted prevalence of ~33%, representing a difference of <5% from the observed prevalence of 37.9%. This difference decreased to <2% when 8 (HG) or 11 (BN) presumptive colonies were selected. In contrast, for non-O157 STEC, ≥38 colonies per sample had to be selected when the maximum concentration of bacteria was ≤1.6 log₁₀ CFU/g in order to achieve ≥90% detection probability of true positives. Selecting 31 (HG) or 56 (BN) presumptive colonies resulted in a model-predicted prevalence of ~38%, which differed by 5% from the observed prevalence (42.9%). The difference was further reduced to <2% when 38 (HG) or 92 (BN) colonies were selected.ConclusionIn conclusion, given the large impact of colony selection totals on the PrBN or PrHG and STEC prevalence estimates, we recommend that authors report the number of presumptive colonies selected per sample in related future research in order to improve inter-study comparability and accurate interpretation of results from studies evaluating E. coli O157:H7 and especially non-O157 STEC in manure samples.

Food-producing animals such as dairy cattle are potential reservoirs of antimicrobial resistance (AMR), with multidrug-resistant (MDR) organisms such as Escherichia coli observed in higher frequency in young calves compared to older cattle. In this study, we characterized the genomes of enteric MDR E. coli from pre-weaned dairy calves with and without diarrhea and evaluated the influence of host-level factors on genomic composition. Whole genome sequence comparative analysis of E. coli (n = 43) revealed substantial genomic diversity that primarily clustered by sequence type and was minimally driven by calf diarrheal disease status (healthy, diarrheic, or recovered), antimicrobial exposure, and dietary zinc supplementation. Diverse AMR genes (ARGs)—including extended-spectrum beta-lactamase genes and quinolone resistance determinants—were identified (n = 40), with unique sets of ARGs co-occurring in gene clusters with large AMR plasmids IncA/C2 and IncFIB(AP001918). Zinc supplementation was not significantly associated with the selection of individual ARGs in E. coli, however analysis of ARG and metal resistance gene pairs identified positive associations between certain aminoglycoside, beta-lactam, sulfonamide, and trimethoprim ARGs with acid, tellurium and mercury resistance genes. Although E. coli in this study lacked the typical virulence factors of diarrheagenic strains, virulence genes overlapping with those in major pathotypes were identified. Among the 103 virulence genes detected, the highest abundance and diversity of genes corresponded to iron acquisition (siderophores and heme uptake). Our findings indicate that the host-level factors evaluated in this study were not key drivers of genomic variability, but that certain accessory genes in enteric MDR E. coli may be enriched. Collectively, this work provides insight into the genomic diversity and host-microbe interface of MDR E. coli from pre-weaned dairy calves.

The objective of this study was to evaluate the impact of dietary zinc supplementation in pre-weaned dairy calves on the phenotypic antimicrobial resistance (AMR) of fecal commensal bacteria. A repository of fecal specimens from a random sample of calves block-randomized into placebo (n = 39) and zinc sulfate (n = 28) groups collected over a zinc supplementation clinical trial at the onset of calf diarrhea, calf diarrheal cure, and the last day of 14 cumulative days of zinc or placebo treatment were analyzed. Antimicrobial susceptibility testing was conducted for Enterococcus spp. (n = 167) and E. coli (n = 44), with one representative isolate of each commensal bacteria tested per sample. Parametric survival interval regression models were constructed to evaluate the association between zinc treatment and phenotypic AMR, with exponentiated accelerated failure time (AFT) coefficients adapted for MIC instead of time representing the degree of change in AMR (MIC Ratio, MR). Findings from our study indicated that zinc supplementation did not significantly alter the MIC in Enterococcus spp. for 13 drugs: gentamicin, vancomycin, ciprofloxacin, erythromycin, penicillin, nitrofurantoin, linezolid, quinupristin/dalfopristin, tylosin tartrate, streptomycin, daptomycin, chloramphenicol, and tigecycline (MR = 0.96–2.94, p > 0.05). In E. coli, zinc supplementation was not associated with resistance to azithromycin (MR = 0.80, p > 0.05) and ceftriaxone (MR = 0.95, p > 0.05). However, a significant reduction in E. coli MIC values was observed for ciprofloxacin (MR = 0.17, 95% CI 0.03–0.97) and nalidixic acid (MR = 0.28, 95% CI 0.15–0.53) for zinc-treated compared to placebo-treated calves. Alongside predictions of MIC values generated from these 17 AFT models, findings from this study corroborate the influence of age and antimicrobial exposure on phenotypic AMR.

Aquaculture has been proposed to sustain the pool of bacteria with antimicrobial resistance (AMR) leading to global threats to human health. This study disclosed the distribution of AMR, including multidrug resistance (MDR), and characterized antimicrobial resistant genes (ARGs) in Escherichia coli recovered from hybrid red tilapia cultivation. Three hundred and thirty-three isolates were recovered from tilapia organs and the cultivation water. The average prevalence of E. coli with no AMR, AMR against one to two antibiotic classes, and MDR against three or more classes was 20.4%, 25.8%, and 53.8%, respectively. In fifteen antibiotic susceptibility tests, the substantial levels of E. coli were resistant to ampicillin (AMP) (63.1%), oxytetracycline (OTC) (58.6%), tetracycline (TET) (58.0%), and oxolinic acid (OXO) (57.4%). All the isolates were slightly resistant to cephalosporins (3.9%), and gentamicin (GEN, 7.5%). Three dominant MDR patterns included AMP-ciprofloxacin (CIP)- enrofloxacin (ENR)-florfenicol (FFC)-OTC-OXO-TET, AMP-OTC-OXO-TET, and CIP-ENR-OXO resistance, dependent on the sample sources. Among 28 ARGs investigated, the prevalence of blaTEM (58.0%), tet(A) (29.1%), tet(B) (23.7%), and qnrS (43.8%) was detected greater than that of the others. The number of extended-spectrum β-lactamase (ESBL)-producing, and quinolone resistant E. coli was 6.6% and 3.9%, respectively. blaTEM, and S83L in gyrA were the major genetic factor responsible for ESBL production and quinolone resistance, respectively. Together, the abundance of AMR E. coli, especially MDR isolates, in hybrid red tilapia cultivation present the risk of ARG transmission to pathogenic bacteria and human food chain.

The incidence of antimicrobial resistance (AMR) in the environment is often overlooked and leads to serious health threats under the One Health paradigm. Infection with extended-spectrum β-lactamase (ESBL) producing bacteria in humans and animals has been widely examined, with the mode of transmission routes such as food, water, and contact with a contaminated environment. The purpose of this study was to determine the occurrence and molecular characteristics of resistant Salmonella enterica (S. enterica) (n = 59) and Escherichia coli (E. coli) (n = 392) isolated from produce commodities collected from fresh markets and supermarkets in Bangkok, Thailand. In this study, the S. enterica isolates exhibited the highest prevalence of resistance to tetracycline (11.9%) and streptomycin (8.5%), while the E. coli isolates were predominantly resistant to tetracycline (22.5%), ampicillin (21.4%), and sulfamethoxazole (11.5%). Among isolates of S. enterica (6.8%) and E. coli (15.3%) were determined as multidrug resistant (MDR). The prevalence of ESBL-producing isolates was 5.1% and 1.0% in S. enterica and E. coli, respectively. A minority of S. enterica isolates, where a single isolate exclusively carried blaCTX-M-55 (n = 1), and another isolate harbored both blaCTX-M-55 and blaTEM-1 (n = 1); similarly, a minority of E. coli isolates contained blaCTX-M-55 (n = 2) and blaCTX-M-15 (n = 1). QnrS (11.9%) and blaTEM (20.2%) were the most common resistant genes found in S. enterica and E. coli, respectively. Nine isolates resistant to ciprofloxacin contained point mutations in gyrA and parC. In addition, the odds of resistance to tetracycline among isolates of S. enterica were positively associated with the co-occurrence of ampicillin resistance and the presence of tetB (P = 0.001), while the E. coli isolates were positively associated with ampicillin resistance, streptomycin resistance, and the presence of tetA (P < 0.0001) in this study. In summary, these findings demonstrate that fresh vegetables and fruits, such as cucumbers and tomatoes, can serve as an important source of foodborne AMR S. enterica and E. coli in the greater Bangkok area, especially given the popularity of these fresh commodities in Thai cuisine.

Antimicrobial resistance (AMR) is a global emerging problem for food safety and public health. Retail meat is one of the vehicles that may transmit antimicrobial resistant bacteria to humans. Here we assessed the phenotypic and genotypic resistance of non-typhoidal Salmonella from retail meat collected in California in 2019 by the National Antimicrobial Resistance Monitoring System (NARMS) Retail Food Surveillance program. A total of 849 fresh meat samples were collected from randomly selected grocery stores in Northern and Southern California from January to December 2019. The overall prevalence of Salmonella was 15.31 %, with a significantly higher occurrence in Southern (28.38%) than in Northern (5.22 %) California. The prevalence of Salmonella in chicken (24.01 %) was higher (p < 0.001) compared to ground turkey (5.42 %) and pork (3.08 %) samples. No Salmonella were recovered from ground beef samples. The prevalence of Salmonella in meat with reduced antibiotic claim (20.35 %) was higher (p < 0.001) than that with conventional production (11.96 %). Salmonella isolates were classified into 25 serotypes with S. Kentucky (47.73 %), S. typhimurium (11.36 %), and S. Alachua (7.58 %) as predominant serotypes. Thirty-two out of 132 (24.24 %) Salmonella isolates were susceptible to all tested antimicrobial drugs, while 75.76 % were resistant to one or more drugs, 62.88 % to two or more drugs, and 9.85 % to three or more drugs. Antimicrobials that Salmonella exhibited high resistance to were tetracycline (82/132, 62.12 %) and streptomycin (79/132, 59.85 %). No significant difference was observed between reduced antibiotic claim and conventional production in the occurrence of single and multidrug resistance. A total of 23 resistant genes, a D87Y mutation of gyrA, and 23 plasmid replicons were identified from resistant Salmonella isolates. Genotypic and phenotypic results were well correlated with an overall sensitivity of 96.85 %. S. infantis was the most resistant serotype which also harbored the IncFIB (pN55391) plasmid replicon and gyrA (87) mutation. Data from Northern and Southern California in this study helps us to understand the AMR trends in Salmonella from retail meat sold in the highly populous and demographically diverse state of California.

This study investigated the prevalence and antimicrobial resistance (AMR) of Escherichia coli (E. coli) in Nile tilapia from fresh markets and supermarkets. A total of samples (n = 828) were collected from Nile tilapia including fish flesh (n = 276), liver and kidney (n = 276), and intestine (n = 276). Overall prevalence of fecal coliforms (61.6%) and E. coli (53.0%) were observed. High prevalence of E. coli was found in the intestine (71.4%), followed by the liver and kidney (45.7%). The highest prevalence of resistance was commonly found against tetracycline (78.5%), ampicillin (72.8%), and sulfamethoxazole (45.6%) with resistance to only tetracycline (15.2%) as the most common antibiogram. The prevalence of multidrug resistance (MDR) (54.4%) and Extended-spectrum beta-lactamases (ESBLs) (5.7%) were examined. The predominant virulence genes (n = 158) were st (14.6%), followed by eaeA (0.6%). The blaTEM (73.4%), tetA (65.2%), and qnrS (57.6%). There is statistical significance between Nile tilapia from fresh markets and supermarkets. Based on logistic regression analysis, ampicillin-resistant E. coli was statistically associated with the phenotypic resistance to tetracycline and trimethoprim, and the presence of blaTEM and tetA (p < 0.05). Further investigation of AMR transference and their mechanisms is needed for AMR control.

This study aimed to investigate AMR profiles of Aeromonas hydrophila, Salmonella spp., and Vibrio cholerae isolated from Nile tilapia (Oreochromis spp.) (n = 276) purchased from fresh markets and supermarkets in Bangkok, Thailand. A sample of tilapia was divided into three parts: fish intestine (n = 276), fish meat (n = 276), and liver and kidney (n = 276). The occurrence of A. hydrophila, Salmonella, and V. cholerae was 3.1%, 7.4%, and 8.5%, respectively. A high prevalence of these pathogenic bacteria was observed in fresh market tilapia compared to those from supermarkets (p < 0.05). The predominant Salmonella serovars were Paratyphi B (6.4%), followed by Escanaba (5.7%), and Saintpaul (5.7%). All isolates tested positive for the virulence genes of A. hydrophila (aero and hly), Salmonella (invA), and V. cholerae (hlyA). A. hydrophila (65.4%), Salmonella (31.2%), and V. cholerae (2.9%) showed multidrug resistant isolates. All A. hydrophila isolates (n = 26) exhibited resistant to ampicillin (100.0%) and florfenicol (100.0%), and often carried sul1 (53.8%) and tetA (50.0%). Salmonella isolates were primarily resistant to ampicillin (36.9%), with a high incidence of blaTEM (26.2%) and qnrS (25.5%). For V. cholerae isolates, resistance was observed against ampicillin (48.6%), and they commonly carried qnrS (24.3%) and tetA (22.9%). To identify mutations in the quinolone resistance determining regions (QRDRs), a single C248A point mutation of C248A (Ser-83-Tyr) in the gyrA region was identified in six out of seven isolates of Salmonella isolates. This study highlighted the presence of antimicrobial-resistant pathogenic bacteria in Nile tilapia at a selling point. It is important to rigorously implement strategies for AMR control and prevention.

Retail meat products may serve as reservoirs and conduits for antimicrobial resistance, which is frequently monitored using Escherichia coli as indicator bacteria. In this study, E. coli isolation was conducted on 221 retail meat samples (56 chicken, 54 ground turkey, 55 ground beef, and 56 pork chops) collected over a one-year period from grocery stores in southern California. The overall prevalence of E. coli in retail meat samples was 47.51% (105/221), with E. coli contamination found to be significantly associated with meat type and season of sampling. From antimicrobial susceptibility testing, 51 isolates (48.57%) were susceptible to all antimicrobials tested, 54 (51.34%) were resistant to at least 1 drug, 39 (37.14%) to 2 or more drugs, and 21 (20.00%) to 3 or more drugs. Resistance to ampicillin, gentamicin, streptomycin, and tetracycline were significantly associated with meat type, with poultry counterparts (chicken or ground turkey) exhibiting higher odds for resistance to these drugs compared to non-poultry meats (beef and pork). From the 52 E. coli isolates selected to undergo whole-genome sequencing (WGS), 27 antimicrobial resistance genes (ARGs) were identified and predicted phenotypic AMR profiles with an overall sensitivity and specificity of 93.33% and 99.84%, respectively. Clustering assessment and co-occurrence networks revealed that the genomic AMR determinants of E. coli from retail meat were highly heterogeneous, with a sparsity of shared gene networks.

This study characterized the effect of distance from beef cattle feedlots, environmental factors, and climate on the occurrence of airborne bacterial indicators and pathogens. Three hundred air samples were collected over 6 months from five feedlots, with each air sample comprising 6000 L of air. Air samples were processed onto TSB-enriched air filters, qPCR-screened, and then qPCR-confirmed for suspect positive colonies of E. coli O157, non-O157-Shiga-toxin-producing E. coli (STEC), Salmonella, and E. coli. Direct enumeration of E. coli was also collected. Although no bacterial pathogens were qPCR-confirmed for the 300 samples, E. coli was detected in 16.7% (50/300) of samples, with an overall mean concentration of 0.17 CFU/6000 L air. Logistic regression analyses revealed a higher odds of E. coli for samples in close proximity compared to >610 m (2000 ft) distance from feedlots, along with significant associations with meteorological factors, sampling hour of day, and the presence of a dust-generating activity such as plowing a field or nearby vehicular traffic. The lack of bacterial pathogen detection suggests airborne deposition from nearby feedlots may not be a significant mechanism of leafy green bacterial pathogen contamination; the result of our study provides data to inform future revisions of produce-safety guidance.

Background Tilapia is a primary aquaculture fish in Thailand, but little is known about the occurrence of antimicrobial resistance (AMR) in Aeromonas hydrophila , Salmonella spp., and Vibrio cholerae colonizing healthy tilapia intended for human consumption and the co-occurrence of these AMR bacteria in the cultivation water. Methods This study determined the phenotype and genotype of AMR, extended-spectrum β -lactamase (ESBL) production, and virulence factors of A. hydrophila , Salmonella spp., and V. cholerae isolated from hybrid red tilapia and cultivation water in Thailand. Standard culture methods such as USFDA’s BAM or ISO procedures were used for the original isolation, with all isolates confirmed by biochemical tests, serotyping, and species-specific gene detection based on PCR. Results A total of 278 isolates consisting of 15 A. hydrophila , 188 Salmonella spp., and 75 V. cholerae isolates were retrieved from a previous study. All isolates of A. hydrophila and Salmonella isolates were resistance to at least one antimicrobial, with 26.7% and 72.3% of the isolates being multidrug resistant (MDR), respectively. All A. hydrophila isolates were resistant to ampicillin (100%), followed by oxytetracycline (26.7%), tetracycline (26.7%), trimethoprim (26.7%), and oxolinic acid (20.0%). The predominant resistance genes in A. hydrophila were mcr-3 (20.0%), followed by 13.3% of isolates having floR , qnrS , sul1 , sul2 , and dfrA1. Salmonella isolates also exhibited a high prevalence of resistance to ampicillin (79.3%), oxolinic acid (75.5%), oxytetracycline (71.8%), chloramphenicol (62.8%), and florfenicol (55.3%). The most common resistance genes in these Salmonella isolates were qnrS (65.4%), tetA (64.9%), bla TEM (63.8%), and floR (55.9%). All V. cholerae isolates were susceptible to all antimicrobials tested, while the most common resistance gene was sul1 (12.0%). One isolate of A. hydrophila was positive for int1 , while all isolates of Salmonella and V. cholerae isolates were negative for integrons and int SXT . None of the bacterial isolates in this study were producing ESBL. The occurrence of mcr-3 (20.0%) in these isolates from tilapia aquaculture may signify a serious occupational and consumer health risk given that colistin is a last resort antimicrobial for treatment of Gram-negative bacteria infections. Conclusions Findings from this study on AMR bacteria in hybrid red tilapia suggest that aquaculture as practiced in Thailand can select for ubiquitous AMR pathogens, mobile genetic elements, and an emerging reservoir of mcr and colistin-resistant bacteria. Resistant and pathogenic bacteria, such as resistance to ampicillin and tetracycline, or MDR Salmonella circulating in aquaculture, together highlight the public health concerns and foodborne risks of zoonotic pathogens in humans from cultured freshwater fish.

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.

California Leafy Green Products Handler Marketing Agreement (LGMA) established food safety metrics with guidance recommendations of 366 m (1,200 feet) and 1,609 m (1 mile) distances between production fields of leafy greens and a concentrated animal feeding operation (CAFO) containing >1,000 and >80,000 head of cattle, respectively. This study evaluated the effect of these distance metrics and environmental factors on the occurrence of airborne Escherichia coli in proximity to seven commercial beef cattle feedlots located in Imperial Valley, California. A total of 168 air samples were collected from seven beef cattle feedlots during March and April 2020, which were the months implicated in the 2018 Yuma Arizona lettuce outbreak of E. coli O157:H7. The distance between air sampling sites and the edge of the feedlot ranged from ∼0 to ∼2,200 m (∼1.3 mile), with each sample comprised of 1,000 L of processed air taken at a 1.2 m elevation over a 10-minute duration. E. coli colonies were enumerated on CHROMagar ECC selective agar and confirmed with conventional PCR. Meteorological data (air temperature, wind speed, wind direction, relative humidity) were collected in situ. The prevalence and mean concentration of E. coli were 6.55% (11/168) and 0.09 CFU per 1,000 L of air, with positive samples limited to within 37 m (120 ft) of the feedlot. Based on logistic regression, the odds of airborne E. coli detection were associated with little to no wind and close proximity to a feedlot. This pilot study found limited dispersal of airborne E. coli in proximity to commercial feedlots in Imperial Valley, with light-to-no wind and proximity within 37 m of a feedlot significant factor-associated airborne E. coli in this produce-growing region of California.

Produce-associated food-borne outbreaks have been increasingly implicated as the significant proportion of the annual incidence of food-borne illness worldwide. The objectives of this study were to determine the concentrations of indicator bacteria and the presence of Salmonella spp., Shigella spp., Escherichia coli (E. coli) O157:H7, and Listeria monocytogenes (L. monocytogenes), and to characterize predictors associated with Salmonella contamination of retail produce from fresh markets and supermarkets in Bangkok, Thailand. A total of 503 samples were collected during May 2018 and February 2019, comprised of sweet basil, spring onion, coriander, cabbage, lettuce, cucumber, and tomato, with conventional items from fresh open-air markets (n=167), conventional items from supermarkets (n=168), and organic items from supermarkets (n=168). The overall prevalence in these 503 items for fecal coliforms and E. coli was 84.3% and 71.4%, with mean concentrations (+/- standard deviation) of fecal coliforms and E. coli being (3.0x10(5)+/- 1.3x10(6)) most probable number (MPN)/g and (1.8x10(5)+/- 1.1x10(5)) MPN/g, respectively. The concentrations of fecal coliforms and E. coli were higher in produce sampled from fresh open-air markets than produce from supermarkets; similarly, these bacterial indicators were higher from produce grown under conventional methods than certified organic produce. The prevalence of Salmonella and Shigella was 4.8% and 0.4%, respectively, but no positives were found for E. coli O157:H7 and L. monocytogenes. The predominant Salmonella serovar was Stanley (30.8%). Based on logistic regression, the odds of Salmonella contamination were significantly (P<0.05) higher during the rainy versus dry season, produce grown using conventional versus organic agriculture, sweet basil versus other commodities, and using ice tank versus dry refrigeration for overnight retail storage. This study indicated that fruits and vegetables are important sources of microbial contamination. Hence, monitoring and surveillance of pathogen contamination to produce is needed to strengthen food safety.

Microbial food safety in cultured tilapia remains a challenge to public health worldwide,due in part to intensive aquaculture leading to poor water quality and high organic matter deposition.This study aimed to determine the prevalence of indicator and potential pathogenic bacteria in hybrid red tilapia(Oreochromis spp.)and their cultivation water and to identify environmental parameters and other bacterial contaminants as-sociated with Salmonella contamination.A total of 120 fish were sampled,which were partitioned into fish carcasses(n=120),muscle(n=120),intestine(n=120),liver and kidney(n=120),and cultivation water(n=120)from three commercial farms in western Thailand from October 2019 to November 2020.The prevalence of fecal coliforms and Escherichia coli(E.coli)in these 600 samples was 74.8％and 56.7％,respectively.The prevalence of Salmonella,Vibrio cholerae(V.cholerae),Aeromonas hydrophila,and Vibrio vulnificus(V.vulnificus)was 23.0％,17.5％,2.5％,and 1.7％,respectively.None of the samples tested positive for Streptococcus agalactiae.Cultivation water exhibited a high prevalence for Salmonella(58.3％).Among fish samples,Salmonella had the highest prevalence at 14.1％,which was mainly from fish intestine.There was a significant association of Salmonella with the presence of fecal coliforms,E.coli,V.cholerae,and V.vulnificus.The predominant serovars of Salmonella included Saintpaul,Neukoelln,Escanaba,and Papuana.Grazing ducks that were raised in proximity to these cultured tilapia shared the same isolates of Salmonella based on the similarity of their rep-PCR DNA fingerprints,suggesting that ducks may function as either a bio-logical reservoir for tilapia or at minimum participate in the environmental replication of this strain of Salmonella.Taken together,the results suggest that the environment used for tilapia aquaculture may be contaminated with pathogenic bacteria;therefore,food safety precautions are needed during processing,transportation,cooking,and consumption.

Pandemics caused by pathogens that originate in wildlife highlight the importance of understanding the behavioral ecology of disease outbreaks at human-wildlife interfaces. Specifically, the relative effects of human-wildlife and wildlife-wildlife interactions on disease outbreaks among wildlife populations in urban and peri-urban environments remain unclear. We used social network analysis and epidemiological Susceptible-Infected-Recovered models to simulate zooanthroponotic outbreaks, through wild animals' joint propensities to co-interact with humans, and their social grooming of conspecifics. On 10 groups of macaques (Macaca spp.) in peri-urban environments in Asia, we collected behavioral data using event sampling of human-macaque interactions within the same time and space, and focal sampling of macaques' social interactions with conspecifics and overall anthropogenic exposure. Model-predicted outbreak sizes were related to structural features of macaques' networks. For all three species, and for both anthropogenic (co-interactions) and social (grooming) contexts, outbreak sizes were positively correlated to the network centrality of first-infected macaques. Across host species and contexts, the above effects were stronger through macaques' human co-interaction networks than through their grooming networks, particularly for rhesus and bonnet macaques. Long-tailed macaques appeared to show intraspecific variation in these effects. Our findings suggest that among wildlife in anthropogenically-impacted environments, the structure of their aggregations around anthropogenic factors makes them more vulnerable to zooanthroponotic outbreaks than their social structure. The global features of these networks that influence disease outbreaks, and their underlying socio-ecological covariates, need further investigation. Animals that consistently interact with both humans and their conspecifics are important targets for disease control.

The occurrence of waterborne antimicrobial-resistant (AMR) bacteria in areas of high-density oyster cultivation is an ongoing environmental and public health threat given the popularity of shellfish consumption, water-related human recreation throughout coastal Thailand, and the geographical expansion of Thailand’s shellfish industry. This study characterized the association of phenotypic and genotypic AMR, including extended-spectrum β-lactamase (ESBL) production, and virulence genes isolated from waterborne Escherichia coli (E. coli) (n = 84), Salmonella enterica (S. enterica) subsp. enterica (n = 12), Vibrio parahaemolyticus (V. parahaemolyticus) (n = 249), and Vibrio cholerae (V. cholerae) (n = 39) from Thailand’s coastal aquaculture regions. All Salmonella (100.0%) and half of V. cholerae (51.3%) isolates harbored their unique virulence gene, invA and ompW, respectively. The majority of isolates of V. parahaemolyticus and E. coli, ~25% of S. enterica subsp. enterica, and ~12% of V. cholerae, exhibited phenotypic AMR to multiple antimicrobials, with 8.9% of all coastal water isolates exhibiting multidrug resistance (MDR). Taken together, we recommend that coastal water quality surveillance programs include monitoring for bacterial AMR for food safety and recreational water exposure to water for Thailand’s coastal water resources.