Prevalence of Salmonella spp., Listeria monocytogenes, Campylobacter spp. and Enterobacteriaceae in raw pet food

BackgroundClose contact between pets and owners provides the opportunity for transmission of antimicrobial resistant organisms like extended-spectrum beta-lactamase (ESBL)/AmpC beta-lactamase (AmpC)-producing Enterobacteriaceae, posing a risk to public health.ObjectivesTo investigate whether raw feed is a risk factor for household cats to shed ESBL-producing Enterobacteriaceae, a cohort study was designed. Additionally, raw and non-raw commercial pet food products were screened for the presence of ESBL-producing Enterobacteriaceae.MethodsWeekly fecal samples of 17 cats in the control group and 19 cats in the exposed group were collected for three weeks and analyzed for the presence of ESBL-producing Enterobacteriaceae. Questionnaires were obtained to determine additional risk factors. Fecal samples were cultured on MacConkey agar supplemented with 1 mg/L cefotaxime. PCR and sequence analysis was used for screening for ESBL genes in suspected isolates. Pet food samples were cultured in LB broth supplemented with 1 mg/L cefotaxime and processed as described above.ResultsIn the cohort study, ESBL-producing bacteria were isolated from 3 of 51 (5.9%) samples in the control group compared to 37 of 57 (89.5%) samples in the exposed group. A significant association was found between ESBL shedding and feeding raw pet food products (OR = 31.5). No other risk factors were identified in this study. ESBL-producing Enterobacteriaceae were isolated from 14 of 18 (77.8%) raw pet food products and 0 of 35 non-raw pet food products.ConclusionsThis study shows a strong association between shedding of ESBL-producing bacteria in household cats and feeding raw pet food. Raw pet food was often contaminated with ESBL-producing Enterobacteriaceae.

Raw meat pet food is increasingly popular in Great Britain prompting concerns about its potential to transmit zoonotic pathogens, particularly Salmonella. To investigate correlations between Salmonella isolated from dog food (both raw and heat-treated) and from dogs, using historical passive surveillance data from manufacturing plants and clinical samples. Data collected by the Animal and Plant Health Agency from 2013 to 2022 (phenotypically-determined Salmonella serovars plus their phage types and disc-diffusion antimicrobial resistance profiles) were compared between dog food and canine clinical sources. Over time both the number and serovar diversity of Salmonella isolations from raw meat pet food increased, from 4 isolates of 4 serovars in 2013 to 606 isolates of 39 serovars in 2022, in parallel with a five-fold increase in the number of raw meat pet food plants operating in Great Britain. Between 2021 and 2022, following the implementation of statutory Salmonella reporting in dogs, considerable overlaps in serovar distributions were observed between raw meat pet food and dog samples, with serovars of significant public health importance such as S. Typhimurium, monophasic S. Typhimurium and S. Infantis among the top 10 most frequently isolated from both sources. Some serovars, like S. Indiana and subspecies diarizonae, were more frequently isolated from raw meat pet food while others like S. Typhimurium and S. Dublin, were over twice as frequent among dog isolates. Antimicrobial resistance patterns revealed some correlations between sources for certain serovars, such as S. Typhimurium, while for others (including S. Dublin) resistance patterns were unique to the dog isolates. Resistances to cefotaxime, ceftazidime or ciprofloxacin were rare, although exceptionally 9.9% of S. Infantis isolates from raw meat pet food showed ciprofloxacin resistance. S. Kentucky resistant to cefotaxime, ceftazidime and ciprofloxacin was isolated from a dog sample. Despite limitations for establishing direct transmission pathways, the findings highlight raw meat pet food as a potential vector for Salmonella transmission, emphasizing the risks to both animal and public health and underlining the need for vigilant monitoring and hygiene practices. For antimicrobial resistance risk, generally high susceptibility to the extended spectrum cephalosporin and fluoroquinolone classes is reassuring, although the detection of multi-drug-resistant strains highlights ongoing concerns.

Reports of raw meat pet food containing zoonotic foodborne bacteria, including Salmonella, Escherichia coli, and Listeria monocytogenes, are increasing. Contaminated raw pet food and biological waste from pets consuming those diets may pose a public health risk. The U.S. Food and Drug Administration Veterinary Laboratory Investigation and Response Network conducted 2 case investigations, involving 3 households with animal illnesses, which included medical record review, dietary and environmental exposure interviews, animal sample testing, and whole genome sequencing (WGS) of bacteria isolated from the pets and the raw pet food. For each case investigation, WGS with core genome multi-locus sequence typing analysis showed that the animal clinical isolates were closely related to one or more raw pet food bacterial isolates. WGS and genomic analysis of paired animal clinical and animal food isolates can confirm suspected outbreaks of animal foodborne illness.

The Combined Use of High Pressure Processing and Lactic Acid Containing Fermentate on Inactivation of Salmonella, Shiga Toxin-producing E. coli, and Listeria monocytogenes in Raw Pet Foods

The increasing popularity of raw meat-based diets (RMBDs) and raw milk feeding in companion animals presents a growing concern for zoonotic disease transmission. Recent evidence has demonstrated that these products can serve as vehicles for highly pathogenic avian influenza (HPAI) H5N1, an emergent viral threat with a host range from birds, dairy cattle, and pets to humans. Since the emergence of clade 2.3.4.4b in 2020, HPAI H5N1 has caused widespread outbreaks in poultry, wild birds, and mammals, including dairy cattle and cats. Transmission to pets has been linked to ingestion of contaminated raw pet food and unpasteurized milk. Notably, multiple outbreaks in cats across Europe, Asia, and North America have been associated with raw pet food products, while recent U.S. cases confirm direct viral transmission from infected pet food, raw milk, and colostrum. Experimental studies have also supported the plausibility of gastrointestinal and respiratory routes of infection in cats and dogs, with felines appearing particularly susceptible, often exhibiting severe clinical disease and high mortality. A number of documented recalls of H5N1-contaminated raw pet food and raw milk in the US underscore the persistence of infectious viruses in cold-stored food products and highlight the risks of feeding raw diets. Although pet-to-human transmission of the HPAI H5N1 virus has not been reported yet, cat-to-human transmission of the H7N2 influenza virus has been reported in the USA. This review presents current evidence on H5N1 in RMBDs and raw milk, its epidemiology in companion animals, outbreaks, and the health implications among pets and humans. By raising awareness among pet owners, industry stakeholders, and veterinarians, this paper highlights the immediate need for stringent surveillance and improved biosecurity in raw food supply chains to minimize viral transmission risks, thereby safeguarding pet health and curb the potential spillover to humans.

In August 2017, a cluster of four persons infected with genetically related strains of Shiga toxin-producing Escherichia coli (STEC) O157:H7 was identified. These strains possessed the Shiga toxin (stx) subtype stx2a, a toxin type known to be associated with severe clinical outcome. One person died after developing haemolytic uraemic syndrome. Interviews with cases revealed that three of the cases had been exposed to dogs fed on a raw meat-based diet (RMBD), specifically tripe. In two cases, the tripe had been purchased from the same supplier. Sampling and microbiological screening of raw pet food was undertaken and indicated the presence of STEC in the products. STEC was isolated from one sample of raw tripe but was different from the strain causing illness in humans. Nevertheless, the detection of STEC in the tripe provided evidence that raw pet food was a potential source of human STEC infection during this outbreak. This adds to the evidence of raw pet food as a risk factor for zoonotic transmission of gastrointestinal pathogens, which is widely accepted for Salmonella, Listeria and Campylobacter spp. Feeding RMBD to companion animals has recently increased in popularity due to the belief that they provide health benefits to animals. Although still rare, an increase in STEC cases reporting exposure to RMBDs was detected in 2017. There has also been an increased frequency of raw pet food incidents in 2017, suggesting an increasing trend in potential risk to humans from raw pet food. Recommendations to reduce the risk of infection included improved awareness of risk and promotion of good hygiene practices among the public when handling raw pet food.

ObjectivesThe Food Safety Modernization Act (FSMA) has established a “zero tolerance” for Salmonella in pet food. The objective of this experiment was to evaluate the effectiveness of High Pressure Processing (HPP) and frozen storage time on the inactivation of non-pathogenic, surrogate bacteria populations in raw pet food. Materials and MethodsApproximately 18 kg of a raw beef pet food was inoculated to a target of 7 logs CFU/g with a 5 strain cocktail of non-pathogenic Escherichia coli (ATCC BAA 1427–31) which was previously validated as a surrogate for Salmonella. The inoculated product was packaged in 227 g individual roll stock packages and shipped to an external facility for HPP application. Inoculated samples were subjected to HPP at 600 mpa for 480 s. After HPP processing, samples were transported on ice to Colorado State University for determination of the remaining microbial population. The samples were randomly assigned to either sampling at 24-hours post-processing (n = 10) or following 5 d of frozen storage at -23°C (n = 10). Raw product samples were serially diluted in BPW and plated onto selective (Violet Red Bile Agar; VRBA; selective for coliforms) and non-selective (Tryptic Soy Agar; TSA) medias for enumeration. ResultsAt 24 h post-processing, following HPP, surviving colonies on VRBA totaled 1.8 logs CFU/g (4.9 log CFU/g reduction) following HPP and frozen storage, surviving colonies on VRBA totaled 0.48 logs CFU/g (6.2 log CFU/g reduction) with 90% of all samples under the detection limit. The TSA survivors totaled 4.8 logs CFU/g (2.1 log CFU/g reduction) 24 h post HPP and totaled 4.6 logs CFU/g (2.3 log CFU/g reduction) post HPP and frozen storage. Data were analyzed using the mixed procedure of SAS (version 9.3; SAS Inst. Inc., Cary, NC) and separated using the PDIFF statement with an ɑ of 0.05. ConclusionHigh Pressure Processing effectively kills pathogenic bacterial strains and causes substantial sub-lethal damage/injury to the bacterial cells, reducing the ability of the bacteria to recover and grow on selective media. Additionally, cellular injury leads to additional lethality in bacterial cells following frozen storage. Therefore, HPP and subsequent frozen storage are effective means of killing significant numbers of bacteria, but these methods do not achieve total death or sterilization. As a result, additional interventions must be investigated to achieve sterility and total destruction of Salmonella.

There has been concerns related to the risk of bacterial contamination from raw pet food to humans, but research is still scarce. The purpose of this cross-sectional study was to...

The purpose of the study was to characterize the commercially available raw meat pet food diets in the Minneapolis/St. Paul area by (i) determining the number and types of available diets; (ii) assessing pet food stores and brand labels for the provision of precautionary statements regarding the risk of foodborne illness from raw meat; (ii) assessing the labels for Food and Drug Administration (FDA)/American Association of Feed Control Officials (AAFCO) required content and nutrient-related information; and (iv) culturing purchased diets for the presence of Salmonella. Sixty raw meat diets were purchased, representing 11 different brands from eight different stores. Diets were readily available in the form of raw-frozen, dehydrated or freeze-dried varieties from different protein sources, such as lamb, beef, chicken or duck. All stores promoted raw meat diets; however, none provided foodborne illness warnings. Brands varied greatly in their precautionary statements; none of the diets underwent feeding trials; and nutritional adequacy substantiation was through formulation only. The first five ingredients tended to consist of meat, organ meat (by-products), vegetables, grains and ground bones. Currently, it is required that pet foods have an AAFCO nutritional adequacy statement and provide a guaranteed analysis table. Three brands did not meet these FDA requirements. Thirty-one (51.7%) of the 60 raw meat diets underwent some degree of processing including dehydration, freeze-drying or high-pressure pasteurization. Four of the 60 raw diets (7%) tested positive for Salmonella. Analysis of raw meat pet food labels indicated a lack of foodborne illness warnings. Based on these findings, we recommend that warning statements similar to those required by the United States Department of Agriculture and placed on labels of raw meat intended for human consumption be provided on the labels of raw meat pet food diets.

High-pressure processing inactivation of Salmonella in raw pet food for dog is enhanced by acidulation with lactic acid

Rapid Screening for Salmonella in Raw Pet Food by Loop-Mediated Isothermal Amplification

ObjectivesThe Food Safety Modernization Act (FSMA) has established a “zero tolerance” for Salmonella in pet food. The objective of this experiment was to evaluate the effectiveness of High Pressure Processing (HPP) and frozen storage time on the inactivation of non-pathogenic, surrogate bacteria populations in raw pet food.Materials and MethodsApproximately 18 kg of a raw beef pet food was inoculated to a target of 7 logs CFU/g with a 5 strain cocktail of non-pathogenic Escherichia coli (ATCC BAA 1427–31) which was previously validated as a surrogate for Salmonella. The inoculated product was packaged in 227 g individual roll stock packages and shipped to an external facility for HPP application. Inoculated samples were subjected to HPP at 600 mpa for 480 s. After HPP processing, samples were transported on ice to Colorado State University for determination of the remaining microbial population. The samples were randomly assigned to either sampling at 24-hours post-processing (n = 10) or following 5 d of frozen storage at -23°C (n = 10). Raw product samples were serially diluted in BPW and plated onto selective (Violet Red Bile Agar; VRBA; selective for coliforms) and non-selective (Tryptic Soy Agar; TSA) medias for enumeration.ResultsAt 24 h post-processing, following HPP, surviving colonies on VRBA totaled 1.8 logs CFU/g (4.9 log CFU/g reduction) following HPP and frozen storage, surviving colonies on VRBA totaled 0.48 logs CFU/g (6.2 log CFU/g reduction) with 90% of all samples under the detection limit. The TSA survivors totaled 4.8 logs CFU/g (2.1 log CFU/g reduction) 24 h post HPP and totaled 4.6 logs CFU/g (2.3 log CFU/g reduction) post HPP and frozen storage. Data were analyzed using the mixed procedure of SAS (version 9.3; SAS Inst. Inc., Cary, NC) and separated using the PDIFF statement with an ɑ of 0.05.ConclusionHigh Pressure Processing effectively kills pathogenic bacterial strains and causes substantial sub-lethal damage/injury to the bacterial cells, reducing the ability of the bacteria to recover and grow on selective media. Additionally, cellular injury leads to additional lethality in bacterial cells following frozen storage. Therefore, HPP and subsequent frozen storage are effective means of killing significant numbers of bacteria, but these methods do not achieve total death or sterilization. As a result, additional interventions must be investigated to achieve sterility and total destruction of Salmonella.

Contamination of pet food with Salmonella is a serious public health concern, and several disease outbreaks have recently occurred due to human exposure to Salmonella tainted pet food. The problem is especially challenging for raw pet foods (which include raw meats, seafood, fruits, and vegetables). These foods are becoming increasingly popular because of their nutritional qualities, but they are also more difficult to maintain Salmonella-free because they lack heat-treatment. Among various methods examined to improve the safety of pet foods (including raw pet food), one intriguing approach is to use bacteriophages to specifically kill Salmonella serotypes. At least 2 phage preparations (SalmoFresh® and Salmonelex™) targeting Salmonella are already FDA cleared for commercial applications to improve the safety of human foods. However, similar preparations are not yet available for pet food applications. Here, we report the results of evaluating one such preparation (SalmoLyse®) in reducing Salmonella levels in various raw pet food ingredients (chicken, tuna, turkey, cantaloupe, and lettuce). Application of SalmoLyse® in low (ca. 2-4×106 PFU/g) and standard (ca. 9×106 PFU/g) concentrations significantly (P < 0.01) reduced (by 60-92%) Salmonella contamination in all raw foods examined compared to control treatments. When SalmoLyse®-treated (ca. 2×107 PFU/g) dry pet food was fed to cats and dogs, it did not trigger any deleterious side effects in the pets. Our data suggest that the bacteriophage cocktail lytic for Salmonella can significantly and safely reduce Salmonella contamination in various raw pet food ingredients.

Using a next-generation sequencing approach to DNA metabarcoding for identification of adulteration and potential sources of mercury in commercial cat and dog foods.

Simple SummaryPet food and treat industries are rapidly growing and are important consumers of protein co-products from the human meat processing industry. Unfortunately, there are some co-products such as liver that can be difficult to handle due to the fact it liquifies when ground. This research attempts to address this issue through the use of protein structure forming food technology (hydrocolloids). These technologies may help produce pet foods and treats with higher acceptability, while allow for upcycling of highly nutritious protein co-products. Additions of one such technology (sodium alginate and encapsulated calcium lactate) demonstrated that inclusions of liver could be increased when used in raw pet foods and dehydrated pet treats without negatively impacting chemical attributes that may adversely impact consumer acceptance.Pet humanization and premiumization of pet foods have led to significant changes in the co-product market, as pet food companies are looking for more profitable protein sources for their products. Co-products such as beef liver (BL) and beef heart (BH) can be combined to generate restructured pet foods rich in vitamins and nutrients. Sodium alginate and encapsulated calcium lactate (ALGIN) can improve the acceptability of meat pieces by transforming them into a singular shape. The objective of this experiment was to assess the physiochemical parameters of co-products for utilization in raw pet foods and restructured pet treats generated from BL and BH by using ALGIN as a structure-forming agent. Results demonstrated increased cooking loss as ALGIN inclusion decreased, but cooking loss decreased as BL proportions increased (p = 0.0056). Expressible moisture of raw pet food decreased as ALGIN inclusion increased, but more moisture was released from treats when BL proportions increased (p < 0.0001). Increasing ALGIN and BH led to increased water activity of cooked treats (p < 0.0001). Thus, we suggest that BL and BH combinations with ALGIN inclusion produces a viable platform for higher inclusions of co-products in pet treats. Additionally, these ingredients improved the finished product quality characteristics of raw pet foods.