Review of Escherichia Coli Infections of Veterinary Importance

Abstract

Escherichia coli is a vital pollutant indicator, and pathogenic strains are a serious public health concern. Total coliform bacteria and E. coli count have been known indicators of unsanitary conditions and fecal contamination in food. The most common cause of E. coli O157:H7 outbreaks is the consumption of undercooked beef or other foods contaminated with beef. Such outbreaks are typically identified by a significant increase in illness within a group or community. Common-source outbreaks are typically brief, limited by the quantity and shelf life of the contaminated product(s), and avoidable with proper kitchen hygiene and cooking. Extraintestinal pathogenic E. coli (ExPEC), which causes diseases in humans, is suspected to be present in chicken products. The zoonotic risk of E. coli from chickens to humans is not fully understood. Food safety concerns with new meat products (for example, meat tenderization and E. coli internalization) as well as the development and evaluation of intervention strategies are some areas that require ongoing research and monitoring. Preventive measures include protecting the food from direct or indirect contamination, using personal hygiene practices, storing processed food in appropriate places and temperatures, checking packaging and storage, well cooking, proper cooling, and keeping cooked food separate from raw food.

1. Introduction

E. coli typically colonizes the gastrointestinal tract of humans and animals within a few hours after birth. Typically, E. coli and its human host coexist in good health and mutual benefit for decades. Except in immunocompromised hosts or when the normal gastrointestinal barriers are breached, such as in peritonitis, these commensal E. coli strains rarely cause disease. The mucous layer of the mammalian colon serves as a home for commensal E. coli. Despite an immense body of literature on the genetics and physiology of this species, the mechanisms by which E. coli maintains this favorable symbiosis in the colon are poorly understood. One intriguing theory proposes that E. coli may take advantage of its ability to use gluconate in the colon more efficiently than other resident species, allowing it to occupy a highly specific metabolic niche [1, 2].

E. coli is the most common foodborne pathogenic bacteria. Despite the well-documented risk of enteric infection, some consumers prefer to drink unpasteurized milk [3, 4]. E. coli enteropathogenic, enteroinvasive, and enterotoxigenic strains can be major cause of foodborne diarrhea [5]. The pathogen and food vehicle responsible for the majority of foodborne infections are difficult to identify. Foodborne diseases are primarily associated with unsanitary practices and the use of contaminated instruments and materials in food processing [6, 7].

E. coli O157:H7 is commonly found in food. Because of its low infectious dose and potentially fatal complications, this organism has emerged as a significant pathogen and a serious threat to public health [8]. This organism is mostly associated with bovine-derived foods, ground meat, and raw milk outbreaks [9]. It is transmitted fecally or orally and should never be found in food. This microorganism most noticeable symptom is diarrhea, sepsis, meningitis, and a variety of enteric diseases. As a result, this paper will focus on a review of the significance of food contaminated with E. coli of animal origin (meat, milk, and eggs), food contamination cases, current food safety approaches, and mitigation methods.

2. E. coli and food commodities of concern

E. coli is a coliform bacterium and one of six Escherichia species. It is one of 30 members of the Enterobacteriaceae bacterial family (E. adecaroxylate, E. blattae, Escherichia fergusonii, Escherichia hermannii, and Escherichia vulneris). The presence of coliforms in food indicates fecal contamination, poor hygiene, or the presence of enteric pathogens [10, 11]. It is widely assumed that farm ruminants, specifical cattle, are the primary reservoirs of EHEC. However, it is unclear to what extent EHEC can be considered ubiquitous in cattle, as well as the reasons for EHEC’s sporadic nature and variation in prevalence in cattle across the globe. Person-to-person transmission, animal contact, foodborne transmission, and waterborne transmission are the most common routes of EHEC infection. Only the foodborne route is discussed further in this review [12].

Raw or undercooked bovine foods, particularly undercooked ground beef and unpasteurized milk, have been implicated in the majority of EHEC outbreaks. Ground beef has been identified as an important risk factor for EHEC infection in several case-control studies. Furthermore, outbreaks and sporadic infections indicate that ground beef consumption remains the single most frequently identified source of foodborne EHEC infection. Dry fermented meats, as well as cooked and fermented sausages, have also been linked to reported EHEC outbreaks. However, a growing number of outbreaks have been linked to eating raw or minimally processed fruits and vegetables. Leafy green vegetables, such as lettuce, have been linked to several large E. coli O157:H7 outbreaks, some of which have had serious public health consequences. Because they are prone to contamination and are eaten raw, they are a significant source of human cases of EHEC-related foodborne illness [13].

2.1 E. coli associated with meat

E. coli O157:H7 belongs to the enterohemorrhagic E. coli (EHEC) group and was first identified as a human pathogen in 1982 when strains of a previously uncommon serotype, O157:H7, were linked to two outbreaks of hemorrhagic colitis (HC) in the United States of America. In the years since outbreaks and isolated cases of EHEC O157:H7 infection have been reported in some countries around the world. Infections caused by non-O157 E. coli serotypes, such as O26:H11, O103:H2, O104:H21, O111:H8, and O113:H21, are also frequently reported [13].

EHECs have been isolated from cattle, sheep, swine, goats, and deer, among other domestic animals and wildlife. Ruminants, particularly cattle, are thought to be a major reservoir of EHEC. Although multiple sources and routes of transmission are now known, data from outbreaks and sporadic infections show that beef and beef products are the most frequently identified source of foodborne EHEC infection. Undercooked ground beef products, in particular, have emerged as a significant source of foodborne infection. Milk and dairy products (e.g., unpasteurized milk and raw milk cheese), fresh produce (e.g., sprouts and salads), drinks (e.g., apple cider or juice), and water are other foodborne sources. Several new outbreaks have been reported, involving various sources and demonstrating the multifaceted epidemiology of EHEC infections [13].

2.2 History of E. coli O157:H7 in the meat industry

Meat inspection began in France in 1162, in England in 1319, and in Germany in 1385. Meat inspection was first observed in the United States in the 1800s, but mandatory inspection did not begin until 1906, with the passage of the Meat Inspection Act. The publication of Upton Sinclair’s book the Jungle in 1904 sparked interest in the government. The meat industry was found to have poor food safety practices, according to the Jungle. The book outlined several areas during slaughter and manufacturing, where additional food safety implementation methods were required. The Meat Inspection Act of 1906 established new regulatory standards for the meat industry that are still in effect today [14].

In 1981 and 1985, Congress passed several laws aimed at improving the inspection system and preventing disease transmission from animals to humans during consumption. The requirement for wholesome products, as well as the evaluation of live animals before slaughter for health reasons, included small butchers and farmers. The poultry industry quickly followed suit with the Poultry Products Inspection Act in 1957. The Wholesome Meat Act and the Wholesome Poultry Products Act were passed by Congress in 1967 and 1968, respectively, to ensure that processing plants would be held accountable for the products produced in their facilities [14].

2.3 Sources of E. coli O157:H7 cross-contamination

Numerous vectors can be used to spread E. coli O157:H7 on or into meat products. Animal feces can be transferred on hides and carcasses, the equipment can become contaminated, personnel may not use proper hygienic practices, airborne contamination, rodents, insects, and other animals are all potential sources (Tables 1 and 2) [14].

Vehicle	E. coli O157:H7 (%)
Water	25.6
Meat	24.6
Dairy	12.5
Animal contact	9.7
Produce	9.2
Person-person contact	6.8
Other food	5.8
Unknown	5.8

Table 1.

The important vehicles linked with international occurrences of E. coli O157:H7.

Sources: [15].

Food	Preservation time (day)
Eggs	14
Fruits	1–14
Vegetables	2–7
Big piece of meat	3–5
Milk and cream	3–4
Cooked fish	2–3
Chicken	2–3
Sausage	2–3
Cooked meat	2–3
Raw fish	1–2
Minced meat	1–2
Shellfish	1

Table 2.

Survival time of E. coli O157:H7 in diverse food and animal products.

Sources: [16].

2.4 E. coli is associated with poultry products

The ExPEC strains that cause these various syndromes are known as avian-pathogenic E. coli (APEC), uropathogenic E. coli (UPEC), neonatal meningitis E. coli (NMEC), and sepsis-associated E. coli, and are sometimes considered to represent distinct pathotypes (SEPEC). ExPEC-associated human diseases cause significant morbidity and mortality, as well as high medical costs and lost productivity, which place a significant economic burden on society [17].

Due to reduced production and/or transmission to consumers through contaminated poultry products, pathogenic bacteria in poultry pose a risk to both the poultry industry and human health. Human pathogens, such as Campylobacter, Listeria, and Salmonella, are known to be present in both meat and eggs. If the recommended limit for microbial load is exceeded, these products may be recalled if they are inspected and found to be contaminated with these organisms [18]. According to recent studies, poultry in particular can transmit the ExPEC strain to humans through meat consumption [19].

ExPEC has multiple virulence traits that allow it to invade, colonize, and cause infections in bodily sites other than the gastrointestinal tract [20]. Many ExPEC isolates from humans and animals have similar virulence genes and clonal backgrounds, implying that they may be zoonotic pathogens [21]. ExPEC virulence genes are common in E. coli isolates from food products, particularly raw meats [20] and poultry meat [22]. Although poultry-sourced E. coli isolates have been shown to cause UTI, sepsis, and meningitis in rodent models that mimic human ExPEC infections [23], the human health risk posed by poultry products is still being debated because direct transmission of ExPEC from poultry to humans is difficult to document [19].

ExPEC isolates are genotypically heterogeneous, which complicates determining the zoonotic risk of poultry products. They not only share numerous genomic similarities with commensal, nonpathogenic E. coli [24], but the different putative ExPEC subgroups are also difficult to distinguish. Although recent evidence suggests that phylotypes and virulence genotypes can distinguish ExPEC from commensal E. coli [25, 26, 27], host-pathogen interactions can lead to differential gene expression in vivo [28].

2.5 Survival of E. coli on the food of animal origin

E. coli O157:H7 is a cause for concern, especially if it is present in foods that have not been treated to eliminate the pathogen, or that may have been contaminated after such treatment but before packaging, as in the case of ready-to-eat (RTE) products. When microorganisms are exposed to a lethal agent, the population decreases exponentially rather than instantly. The D value, also known as “decimal reduction time,” is used in food microbiology to describe the time required in minutes at any given temperature to reduce 90%(or 1 log) of a specific microbial population in a specific food, and it is affected by factors, such as pH, water activity (Aw), preservative content, product composition, and the size of the microbial population, among others. According to research, cooking ground beef with 17–20% fat at 57.28°C and 62.88°C results in D values of 4.5 and 0.40, respectively. To ensure adequate cooking and prevent outbreaks, hamburgers must be cooked for 15 seconds at an internal temperature of 71.18°C (1608F) [14].

Pasteurization is another common heating method used to kill this pathogen in milk, fruit juices, and ciders. Milk can be pasteurized for 15 seconds at 71.78°C (1618F) for a 5-log reduction in E. coli O157:H7, and apple cider can be pasteurized for 14 seconds at 68.1°C. [29]. Ground beef stored at −208°C for 12 months recovered the pathogen with an approximate reduction of 1.0 log [30], demonstrating the ability of E. coli O157:H7 to survive in hamburgers for long periods at frozen temperatures with little decline in viable cell numbers. As a result, E. coli O157:H7 has the unique ability to survive in a wide range of products subjected to varying process conditions for extended periods, allowing foods to serve as vehicles for infection transmission.

2.6 Means of food poisonings interventions

The Processed Products Inspection Improvement Act of 1986 gave meat inspectors a resource for allocating training and increasing the overall effectiveness of product inspection. These measures were evaluated in the early 1990s, during a period of high-profile food poisoning caused by E. coli O157:H7 and meat products. The USDA mandated the implementation and use of HACCP in meat and poultry plants in 1996 to aid in food safety and as a prevention method. HACCP is intended to identify and control safety hazards during the food manufacturing process. Pillsbury Company introduced HACCP in 1959 to ensure that the food produced for NASA astronauts had a safe food supply during space travel [14].

The concept of preventing rather than reacting to food hazards resulted in a renewal of training and education for meat suppliers and producers. Sanitation practices, pre-and post-operational procedures, flow diagrams of all products produced and slaughter methods, and all forms used to monitor critical control points are all anticipated. Critical control points in the manufacturing process are steps that can reduce or eliminate the possibility of a hazard (chemical, biological, or physical) entering the food product [14].

Furthermore, the term hazard is used in the HACCP to refer to any substance or condition that has the potential to cause adverse health effects and is unacceptable. These risks can be caused by biological, chemical, or physical contamination in raw materials, semi-processed foods, or finished foods. Hazard analysis is defined as determining the severity of a hazard and the likelihood that it will occur. HACCP is a seven-principle-based system for identifying, assessing, and controlling potential food hazards [31, 32]: (1). Conduct hazard analysis; (2). Identify critical control points (CCP); (3). Establish critical limits; (4). Establish monitoring procedures; (5). Establish corrective actions; (6). Establish verification procedures; and (7). Establish documentation and record procedures [32].

State institutions, trade associations, and the food industry all endorse these principles. Today, HACCP-based food safety systems are successfully implemented in food processing plants, retail food stores, and global food service operations. Following HACCP guidelines in manufacturing facilities is critical. HACCP should be used in conjunction with antimicrobial treatment to reduce the presence of potential pathogens, such as E. coli O157: H7 and non-O157 STEC, in cattle carcasses, according to a Mexican slaughterhouse [33]. These guidelines serve as a guarantee for food production, testing, quality, and assurance, assisting in the reduction of the risk of foodborne diseases and ensuring the production and distribution of safe food for human consumption.

All beef processors and plants must develop a plan that identifies the hazards associated with their respective processes and the control measures that can be implemented in each step to reduce their likelihood in the food product as part of the HACCP system adoption. These control measures can be divided into three categories: (a) physical (hot water spray, steam pasteurization, steam-vacuuming, water wash cabinet, and knife trimming); (b) chemical (organic acids, polyphosphates, chlorine, acidified sodium chlorite, ozone, peroxyacetic acid, nisin, and lactoferrin); (c) emerging technologies (hydrostatic pressure, irradiation, pulsed electric fields, and microwaves) (Sa (lactic acid bacteria and bacteriophages). Previous authors have reported on the use and effectiveness of previous interventions on beef hides [34, 35], carcasses [36], beef trim/variety meats, and ground beef [35], and they are frequently used in addition to other procedures, such as carcass inspection and knife trimming off any visible feces, ingest. Furthermore, the use of interventions should not be viewed as a way to “clean” unwholesome products, and they should never be used as a substitute for strict hygienic manufacturing practices and good cleaning and sanitation procedures in the processing facility [14].

3. One health approach and mitigatigations of E. coli

Current clinical laboratory recommendations for EHEC diagnosis in humans, if followed, could allow for earlier diagnosis and better response to infection. To detect both O157:H7 and non-O157 EHEC strains, stools should be cultured on selective and differential agar, such as sorbitol-MacConkey (SMAC) agar and simultaneously tested for Shiga toxins or the genes that encode them [37]. Typical O157:H7 strains do not ferment sorbitol and appear as colorless colonies on SMAC agar, whereas most non-O157 strains ferment sorbitol and appear as pink colonies on SMAC agar. In humans, there are no specific treatments for HUS. Supportive therapy includes intravenous fluids and volume expansion [38].

Still, antibiotics are not recommended in suspected or confirmed cases of O157:H7 infection due to the increased risk of HUS caused by STX-encoding bacteriophage induction [39, 40]. Vaccines, Gb3 receptor analogs, and monoclonal antibodies against STX are examples of human intervention strategies [41, 42, 43]. The best way to avoid HUS is to avoid EHEC O157 infection; recommendations to reduce zoonotic risks associated with animals in public settings are available from the National Association of State Public Health Veterinarians [39, 44]. The most important step in lowering the risk of EHEC O157 and non-O157 transmission is hand washing [44, 45], in this issue, makes the same point about methicillin-resistant Staphylococcus aureus (Figure 1).

Figure 1.

The associations among the factors intricate in enterohemorrhagic Escherichia coli spread. Integrating and understanding the interaction of these factors linking humans, animals, and the environment will facilitate One health approaches to thwart and control the zoonotic transmission of EHEC. Source: [46].

The strain was isolated from feral swine, domestic cattle, surface water, sediment, and soil during the 2006 nationwide outbreak of EHEC O157 in humans, which was linked to the consumption of bagged spinach. It thus demonstrated the significance of the one Health concept [47], a strategy for better understanding and addressing contemporary health issues caused by the convergence of human, animal, and environmental domains [46]. The primary source of the organism, the animal reservoir, should be targeted for control of zoonotic EHEC on farms [48]; methods are available to reduce the risk of EHEC disease in humans at the farm, transport, processing unit, distributor, and retailer/preparer/consumer levels [49].

Probiotics, vaccination, antimicrobials, sodium chlorate, bacteriophages, and other feed additives are used before slaughter to reduce EHEC O157 shedding in the feces of weaned domestic ruminants [50]. Vaccination strategies can reduce EHEC O157 shedding to reduce zoonotic risk [51]. A coordinated multidisciplinary effort to understand and integrate EHEC epidemiology, pathogenesis, and pathophysiology will aid in the development of novel strategies for preventing, controlling, and treating zoonotic EHEC infection and disease.

4. Conclusions

Foodborne pathogens are regarded as a significant risk factor in terms of public health in both developed and developing countries due to their global prevalence. Controllability and traceability are critical throughout the food chain for ensuring consumer safety and protecting foods from biological, physical, and chemical hazards from the field to the point of consumption. The final ring of food safety is the consumer. Consumer purchasing power and awareness contribute to food safety and are the most important factors for risk protection and prevention. Despite their complex biology, epidemiology, and analyses, most foodborne diseases are preventable. It is critical for public health that consumers and food producers follow the principles governing internationally accepted safety methods. It should not be forgotten that E. coli, as a foodborne pathogen, has the potential to cause infections, food poisoning, and even death. There are numerous simple steps that consumers can take to prevent bacterial growth and ensure food safety. In conclusion, consumers should develop their safety methods at home by adhering to personnel sanitation and hygienic measures. Food producers should abide by public health safety method principles, such as HACCP and GMP, to prevent diseases of animal origin and outbreaks.

Funding

The work was not funded by any funding institution or source.

Conflict of interest

The authors declare no conflict of interest.