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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, betalactam, 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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%), blaTEM (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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Coastal pollution is of public health concern due to the possibility of bacterial contamination in aquaculture affecting health risk and seafood safety. This study determined the concentrations of total coliforms, fecal coliforms, E. coli, and V. parahaemolyticus and the presence of V. cholerae and Salmonella in water and measured water quality and meteorological factors from the major oyster cultivation areas in Thailand. The water samples (n = 363) were collected from Surat Thani (n = 60), Chanthaburi (n = 60), Trat (n = 60), Phetchaburi (n = 60), Chonburi (n = 63), and Phang Nga (n = 60) from February 2021 to January 2022. The prevalence of total coliforms (96.7%), fecal coliforms (60.6%), E. coli (22.9%), along with the prevalence of Salmonella (2.5%), Vibrio parahaemolyticus (74.9%), and V. cholerae (11.3%) were determined. Common Salmonella serovars were Othmarschen and Lamberhurst. The concentration of E. coli was significantly associated with dissolved oxygen and precipitation (p < 0.0001). Therefore, continuing microbiological monitoring and surveillance of water for coastal aquaculture is important to produce safe aquatic products. Furthermore, raising awareness of coastal pollution and seafood safety will help enhance sustainable coastal fisheries in Thailand. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Cryptosporidium spp. is a parasite that can infect a wide variety of vertebrate species. The parasite has been detected in sheep worldwide with diverse species and genotypes of various levels of zoonotic potential and public health concern. The purpose of this study was to determine the distribution of genotypes of Cryptosporidium in sheep in California, USA. Microscopic positive samples from individual sheep from central and northern California ranches were genotyped by sequencing a fragment of the 18S rRNA gene and BLAST analysis. Eighty-eight (63.8%) of the microscopic positive samples were genotyped, and multiple genotypes of Cryptosporidium were identified from sheep in the enrolled ranches. Approximately 89% of isolates (n = 78) were C. xiaoi or C. bovis, 10% of isolates (n = 9) were C. ubiquitum, and 1% of isolates (n = 1) were C. parvum. The C. parvum and C. ubiquitum isolates were detected only from lambs and limited to four farms. Given that the majority of Cryptosporidium species (i.e., C. xiaoi and C. bovis) were of minor zoonotic concern, the results of this study suggest that sheep are not a reservoir of major zoonotic Cryptosporidium in California ranches. [ABSTRACT FROM AUTHOR]

We investigated involvement of feral swine in contamination of agricultural fields and surface waterways with Escherichia coli O157:H7 after a nationwide outbreak traced to bagged spinach from California. Isolates from [...]

The results of laboratory flume experiments designed to investigate the stream-subsurface exchange of Cryptosporidium parvum oocysts is presented. The results indicate that the interactions reduce oocyst concentrations in surface waters and they also concentrate oocysts in sediment beds, which then represent a reservoir for pathogens that could be released during high-flow events.

A study conducted to better estimate the annual rate of environmental loading of Cryptosporidium spp. by colonies of California ground squirrels, to better map the distribution of genotypes for the host species is described. Sufficient numbers of oocysts were not available to conduct a mouse infectivity trial, as Sbey03a is a rare type of genotypes in the sample.

Research has been conducted on the waterborne Cryptosporodium parvum. The ability of vegetative buffer strips to remove this bacterium from surface and shallow subsurface flow during simulated rainfalls has been tested, and the results are reported.

Some California ground squirrels shed over 50,000 Cryptosporidium parvum oocysts per gram of feces. Males shed greater numbers of oocysts than females, which could facilitate the dissemination of the organism because males are more likely to leave the family colony.

A direct immunofluorescence assay (DFA) was contrasted with an immunomagnetic separation (IMS) assay combined with immunofluorescent microscopy for their ability to detect low concentrations of Cryptosporidium parvum oocysts in adult bovine feces. IMS-DFA resulted in a 2-log-unit increase in sensitivity compared to DFA alone. The higher sensitivity of the IMS-DFA resulted from testing 2 g of fecal material instead of the 13 to 19 mg of fecal material tested in the DFA. The increased sensitivity was not attributable to a higher percent recovery.

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 associated 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 biological 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. [ABSTRACT FROM AUTHOR]

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 (3.0×105±1.3×106) most probable number (MPN)/g and (1.8×105±1.1×105) 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. [ABSTRACT FROM AUTHOR]

Consumption of contaminated food causes 600 million cases, including 420,000 of fatal infections every year. Estimated cost from food-borne illnesses is USD 110 billion per year, which is an economic burden to low- and middle-income countries. Thailand is a leading producer and consumer of seafood, but little is known about bacterial contamination in seafood. In particular, public health agencies need to know the relationship between Salmonella contamination in seafood and risk factors, as assessed with readily available culture-dependent and bacterial phenotyping methods. To address this, levels of indicator bacteria, Salmonella and Vibrio in various seafood products were determined to identify risk factors associated with Salmonella contamination. A total of 335 samples were collected from October 2018 to July 2019 at seafood markets throughout Bangkok, Thailand; overall sample composition was Pacific white shrimp (n = 85), oysters (n = 82), blood cockles (n = 84), and Asian seabass (n = 84). Prevalence was 100% for fecal coliforms and 85% for E. coli. In contrast, prevalence was 59% for V. parahaemolyticus, 49% for V. cholerae, 19% for V. alginolyticus, 18% for V. vulnificus, and 36% for Salmonella. Highest concentrations of fecal coliforms and E. coli were in oysters. Highest concentrations of Salmonella with Matopeni (31%) being the predominant serotype were in shrimp. Salmonella contamination was significantly associated with type of seafood, sampling location, retail conditions, and the presence of E. coli, V. alginolyticus and V. vulnificus. A cutoff value for E. coli concentration of 1.3 x 104 MPN/g predicted contamination of Salmonella, with a sensitivity of 84% and specificity of 61%. Displaying seafood products on ice, presence of E. coli and Vibrio, and seafood derived from Eastern Thailand were associated with an increased risk of Salmonella contamination. [ABSTRACT FROM AUTHOR]

Background: The presence of Escherichia coli O157:H7 (E. coli O157:H7) super-shedding cattle in feedlots has the potential to increase the overall number (bio-burden) of E. coli O157:H7 in the environment. It is important to identify factors to reduce the bio-burden of E. coli O157 in feedlots by clarifying practices associated with the occurrence of super-shedders in feedlot cattle. Methods: The objective of this study is to (1) identify host, pathogen, and management risk factors associated with naturally infected feedlot cattle excreting high concentrations of E. coli O157:H7 in their feces and (2) to determine whether the ingested dose or the specific strain of E. coli O157:H7 influences a super-shedder infection within experimentally inoculated feedlot cattle. To address this, (1) pen floor fecal samples and herd parameters were collected from four feedlots over a 9-month period, then (2) 6 strains of E. coli O157:H7, 3 strains isolated from normal shedder steers and 3 strains isolated from super-shedder steers, were inoculated into 30 one-year-old feedlot steers. Five steers were assigned to each E. coli O157:H7 strain group and inoculated with targeted numbers of 10², 104, 106, 108, and 1010 CFU of bacteria respectively. Results: In the feedlots, prevalence of infection with E. coli O157:H7 for the 890 fecal samples collected was 22.4%, with individual pen prevalence ranging from 0% to 90% and individual feedlot prevalence ranging from 8.4% to 30.2%. Three samples had E. coli O157:H7 levels greater than 104 MPN/g feces, thereby meeting the definition of super-shedder. Lower body weight at entry to the feedlot and higher daily maximum ambient temperature were associated with increased odds of a sample testing positive for E. coli O157:H7. In the experimental inoculation trial, the duration and total environmental shedding load of E. coli O157:H7 suggests that the time post-inoculation and the dose of inoculated E. coli O157:H7 are important while the E. coli O157:H7 strain and shedding characteristic (normal or super-shedder) are not. Discussion: Under the conditions of this experiment, super-shedding appears to be the result of cattle ingesting a high dose of any strain of E. coli O157:H7. Therefore strategies that minimize exposure to large numbers of E. coli O157:H7 should be beneficial against the super-shedding of E. coli O157:H7 in feedlots. [ABSTRACT FROM AUTHOR]

A cross-sectional study was conducted on the risk factors and prevalence of Giardia sp cysts and Cryptosporidium parvum oocsyts in populations of feral pigs in western California. Results show that, of the 221 feral pigs studied, 12 were shedding Cryptosporidium oocysts and 17 were shedding Giardia sp cysts. Results also indicate that feral pigs may cause surface water protozoal contamination.

Background: Understanding the effects of herd management practices on the prevalence of multidrug-resistant pathogenic Salmonella and commensals Enterococcus spp. and Escherichia coli in dairy cattle is key in reducing antibacterial resistant infections in humans originating from food animals. Our objective was to explore the herd and cow level features associated with the multi-drug resistant, and resistance phenotypes shared between Salmonella, E. coli and Enterococcus spp. using machine learning algorithms. Methods: Randomly collected fecal samples from cull dairy cows from six dairy farms in central California were tested for multi-drug resistance phenotypes of Salmonella, E. coli and Enterococcus spp. Using data on herd management practices collected from a questionnaire, we built three machine learning algorithms (decision tree classifier, random forest, and gradient boosting decision trees) to predict the cows shedding multidrug-resistant Salmonella and commensal bacteria. Results: The decision tree classifier identified rolling herd average milk production as an important feature for predicting fecal shedding of multi-drug resistance in Salmonella or commensal bacteria. The number of culled animals, monthly culling frequency and percentage, herd size, and proportion of Holstein cows in the herd were found to be influential herd characteristics predicting fecal shedding of multidrug-resistant phenotypes based on random forest models for Salmonella and commensal bacteria. Gradient boosting models showed that higher culling frequency and monthly culling percentages were associated with fecal shedding of multidrug resistant Salmonella or commensal bacteria. In contrast, an overall increase in the number of culled animals on a culling day showed a negative trend with classifying a cow as shedding multidrug-resistant bacteria. Increasing rolling herd average milk production and spring season were positively associated with fecal shedding of multidrug- resistant Salmonella. Only six individual cows were detected sharing tetracycline resistance phenotypes between Salmonella and either of the commensal bacteria. Discussion: Percent culled and culling rate reflect the increase in culling over time adjusting for herd size and were associated with shedding multidrug resistant bacteria. In contrast, number culled was negatively associated with shedding multidrug resistant bacteria which may reflect producer decisions to prioritize the culling of otherwise healthy but low-producing cows based on milk or beef prices (with respect to dairy beef), amongst other factors. Using a data-driven suite of machine learning algorithms we identified generalizable and distant associations between antimicrobial resistance in Salmonella and fecal commensal bacteria, that can help develop a producer-friendly and data-informed risk assessment tool to reduce shedding of multidrug-resistant bacteria in cull dairy cows. [ABSTRACT FROM AUTHOR]

Abstract Background Giardia duodenalis is a ubiquitous protozoan parasite that has emerged as a significant opportunistic human pathogen. G. duodenalis may have a deleterious effect on animal growth and performance, therefore its potential as a production limiting organism should not be discounted. We therefore undertook this study to determine management and environmental factors in feedlots that influence the prevalence and environmental load of G. duodenalis cysts in fecal material deposited by feedlot cattle in the central and western United States. Results Twenty two feedlots from 7 states were included in the study, and up to 240 fecal samples were collected from pen floors of up to 6 pens per feedlot. Giardia duodenalis cysts were identified and counted using direct immunofluorescent microscopy. The estimated overall point prevalence of G. duodenalis was 19.1%, representing feedlots from a wide range of climates and management systems. Pen-level prevalence varied from 0 to 63.3%, with pen-level shedding estimates ranging from 0 to 261,000 cysts/g feces. Higher environmental temperatures, increased animal density, and increased time in the feedlot were associated with a lower prevalence of G. duodenalis. Removing manure before placing a new group of cattle in a pen was associated with a decreased prevalence of G. duodenalis in fecal pats. Using coccidiostats as a feed additive was associated with a higher prevalence of Giardia. Conclusion Management practices could be employed that would limit the probability that feedlot cattle shed G. duodenalis in their feces and therefore potentially limit contamination of their environment.

Research was conducted to determine if nucleic acid amplification with primers specific for Cryptosporidium parvum followed by automated DNA sequence analysis of the amplicons could discriminate C parvum isolates derived from different mammalian sources throughout California. A previously set developed set of PCR primers was used for the experiments. Results indicate that there was no sufficient polymorphism within the amplicon to allow for reliable differentiation between C parvum isolates obtained within California.

Bacterial attachment on surfaces is an important biological and industrial concern. Many parameters affect cell attachment behavior, including surface roughness and other topographical features. An understanding of these relationships is critical in the light of recent outbreaks caused by foodborne bacteria. Postharvest packing lines have been identified as a potential source of cross-contamination with pathogens, which can cause subsequent foodborne illness. The objective of this article is to evaluate the influence of surface topographical features on bacterial attachment at various processing temperatures to determine the extent of bacterial colonization. Type 304 stainless steel surfaces and pathogenic Listeria monocytogenes Scott Awere used for a detailed investigation. Two commonly used surface types, extruded and ground, were evaluated to determine differences in bacterial attachment on the same type of material. Fifteen surface topography parameters at three processing temperatures were studied to evaluate possible correlations with microbial attachment on these surfaces. Scanning electron microscopy, energydispersive X-ray spectroscopy, and confocal microscopy were used for both qualitative and quantitative analyses of surfaces. An analysis of variance and multivariate regression analysis were used to predict the attachment behavior of L. monocytogenes Scott A on stainless steel surfaces. Surface isotropy, average surface roughness, surface spacing, and processing temperatures were strongly correlated with bacterial attachment on 304 stainless steel material. [ABSTRACT FROM AUTHOR]

Epidemiological studies of low prevalence disease problems are often hindered by the high cost of diagnostic testing. The objective of this study was to evaluate PCR screening of both individual and pooled fecal samples from culled dairy cows for the invA gene of Salmonella followed by culture to determine if the sensitivity and specificity were comparable to the results from traditional culture methods applied to individual samples. Cows from six different dairies were sampled in all four seasons. A total of 240 individual cow fecal samples, 24 fecal pools and 24 pools of 24-hour tetrathionate enrichment broth were tested. Diagnostic sensitivity of PCR screening followed by culture of PCR positive or indeterminate samples (i.e PCR-CUL method) was lower than that of culture (CUL) when applied to individual fecal samples (94.8%, 99.5%), however the specificity was comparable (99.6% and 97.7% respectively). For pools of five fecal samples and pools of five, 24 h tetrathionate broth samples, the specificity of both tests were comparable (~98%); however, their sensitivity was only comparable in pooled fecal samples (~93%) but greater for culture compared to PCR-CUL in pooled broth samples (~99% versus ~93%). Compared to culture results from testing of individual fecal samples, testing pooled fecal samples by culture had a relative sensitivity of 74% and relative specificity of 96%, testing pooled fecal samples by PCR-CUL resulted in relative sensitivity of 90% and relative specificity of 96%. Testing of pooled 24-hour enrichment broth by PCR-CUL increased the relative sensitivity and specificity to 100%. PCR testing followed by culture of positive or indeterminate samples is a time saving alternative to traditional methods. In addition, pooling of samples may be a useful method for decreasing cost if study aims can accommodate a moderate loss of relative sensitivity. [ABSTRACT FROM AUTHOR]

Phylogenetic analyses of the 18S small-subunit (SSU) rRNA and Cryptosporidium oocyst wall protein (COWP) genes was performed to gain insight into the multiple unique Cryptosporidium isolates shed by separate species of Spermophilus ground squirrels throughout California. The obtained data confirmed with the assertion that Spermophilus squirrels shed novel Cryptosporidium species despite geographical isolation of some squirrel populations.

The rate of inactivation of Cryptosporidium parvum oocysts attributable for daily oscillations of low ambient temperatures is calculated. The determination of the temperature-dependent rate of Cryptosporidium parvum oocyst inactivation for these lower temperatures has allowed grazing management and source water assessment plans to predict the amount of time required for exclusion of cattle prior to the onset of winter precipitation in order to inactivate enough numbers of oocysts in critical watersheds.

The climatic factors and on-farm management practices are analyzed for their association with the concentrations and instantaneous loads of Giardia duodenalis in storm-based runoff from diary lots and other high-cattle-use areas from coastal California farms. The analysis has indicated that vegetated buffer strips might help in reducing the environmental loading of these fecal protozoa discharging from diary farms.