Prevalence and antibiotic resistance profiles of Escherichia coli O157:H7 in beef products from retail outlets in Gaborone, Botswana

A South African Perspective on the Microbiological and Chemical Quality of Meat: Plausible Public Health Implications

Meat comprises proteins, fats, vitamins, and trace elements, essential nutrients for the growth and development of the body. The increased demand for meat necessitates the use of antibiotics in intensive farming to sustain and raise productivity. However, the high water activity, the neutral pH, and the high protein content of meat create a favourable milieu for the growth and the persistence of bacteria. Meat serves as a portal for the spread of foodborne diseases. This occurs because of contamination. This review presents information on animal farming in South Africa, the microbial and chemical contamination of meat, and the consequential effects on public health. In South Africa, the sales of meat can be operated both formally and informally. Meat becomes exposed to contamination with different categories of microbes, originating from varying sources during preparation, processing, packaging, storage, and serving to consumers. Apparently, meat harbours diverse pathogenic microorganisms and antibiotic residues alongside the occurrence of drug resistance in zoonotic pathogens, due to the improper use of antibiotics during farming. Different findings obtained across the country showed variations in prevalence of bacteria and multidrug-resistant bacteria studied, which could be explained by the differences in the manufacturer practices, handling processes from producers to consumers, and the success of the hygienic measures employed during production. Furthermore, variation in the socioeconomic and political factors and differences in bacterial strains, geographical area, time, climatic factors, etc. could be responsible for the discrepancy in the level of antibiotic resistance between the provinces. Bacteria identified in meat including Escherichia coli, Listeria monocytogenes, Staphylococcus aureus, Campylobacter spp., Salmonella spp., etc. are incriminated as pathogenic agents causing serious infections in human and their drug-resistant counterparts can cause prolonged infection plus long hospital stays, increased mortality and morbidity as well as huge socioeconomic burden and even death. Therefore, uncooked meat or improperly cooked meat consumed by the population serves as a risk to human health.

Pathogenic Bacteria and Their Antibiotic Resistance Patterns in Milk, Yoghurt and Milk Contact Surfaces in Debre Berhan Town, Ethiopia

Background

Bacterial contamination of milk is a primary culprit for causing foodborne illnesses, presenting a significant health hazard for millions of individuals around the globe. The level and variety of microorganisms present in raw milk determine its degree of contamination and the potential health risks it poses.

Methods

A cross-sectional survey was conducted from February to August. A questionnaire was used to collect data on socio-demographic characteristics and hygiene practices from milk distributors and traders. Raw milk, yoghurt, swabs from milk containers and drinking cups were collected and processed for bacterial isolation and identification, antibiotic susceptibility testing, MDR screening and confirmation, ESBL screening and confirmation. Finally, all data were pooled and analyzed using SPSS software version 25.

Results

A total of 120 samples of fresh milk, yogurt and cotton swabs from milk containers and cups were collected. A total of 80 bacterial isolates were isolated from 120 samples. Among the bacteria isolated, S. aureus 17 (21.3%), E. coli 17 (21.3%), S. epidermidis 14 (17.5%), Klebsiella spp. 9 (11.3%) and Salmonella spp. 7 (8.8%) were detected most often. High rate of contamination was observed in fresh milk 23 (28.8%) and yogurt 23 (28.8%). All isolates were resistant to at least one antibiotic tested. Comparatively, high rates of resistance were observed in all isolates to the most commonly prescribed antibiotics in Ethiopia. However, lower rates of resistance have been observed for recently introduced antibiotics in Ethiopia. Of the isolates, 20 (25.0%) were resistant to eight or more antibiotics. While 16 (20.0%), 12 (15.0%), 9 (11.3%) isolates were resistant to two, three and five antibiotics, respectively. Of the bacteria isolated, 52/80 (65.0%) were MDR, 25/49 (51.0%) were screened for ESBL production, and 20/49 (40.8%) isolates were confirmed as ESBL producer.

Conclusion

This study showed a high rate of bacterial isolates along with MDR and ESBL-producing strains in raw milk, yoghurt, milk container swabs and drinking cup swab samples, associated with poor hygiene and sanitation practices.

Review of Escherichia coli O157:H7 Prevalence, Pathogenicity, Heavy Metal and Antimicrobial Resistance, African Perspective

Escherichia coli O157:H7 is an important food-borne and water-borne pathogen that causes hemorrhagic colitis and the hemolytic-uremic syndrome in humans and may cause serious morbidity and large outbreaks worldwide. People with bloody diarrhea have an increased risk of developing serious complications such as acute renal failure and neurological damage. The hemolytic-uremic syndrome (HUS) is a serious condition, and up to 50% of HUS patients can develop long-term renal dysfunction or blood pressure-related complications. Children aged two to six years have an increased risk of developing HUS. Clinical enteropathogenic Escherichia coli (EPEC) infections show fever, vomiting, and diarrhea. The EPEC reservoir is unknown but is suggested to be an asymptomatic or symptomatic child or an asymptomatic adult carrier. Spreading is often through the fecal-oral route. The prevalence of EPEC in infants is low, and EPEC is highly contagious in children. EPEC disease in children tends to be clinically more severe than other diarrheal infections. Some children experience persistent diarrhea that lasts for more than 14 days. Enterotoxigenic Escherichia coli (ETEC) strains are a compelling cause of the problem of diarrheal disease. ETEC strains are a global concern as the bacteria are the leading cause of acute watery diarrhea in children and the leading cause of traveler’s diarrhea. It is contagious to children and can cause chronic diarrhea that can affect the development and well-being of children. Infections with diarrheagenic E. coli are more common in African countries. Antimicrobial agents should be avoided in the acute phase of the disease since studies showed that antimicrobial agents may increase the risk of HUS in children. The South African National Veterinary Surveillance and Monitoring Programme for Resistance to Antimicrobial Drugs has reported increased antimicrobial resistance in E. coli. Pathogenic bacterial strains have developed resistance to a variety of antimicrobial agents due to antimicrobial misuse. The induced heavy metal tolerance may also enhance antimicrobial resistance. The prevalence of antimicrobial resistance depends on the type of the antimicrobial agent, bacterial strain, dose, time, and mode of administration. Developing countries are severely affected by increased resistance to antimicrobial agents due to poverty, lack of proper hygiene, and clean water, which can lead to bacterial infections with limited treatment options due to resistance.

Molecular mechanisms and clonal lineages of colistin-resistant bacteria across the African continent: A scoping review

Colistin (also known as Polymyxin E), a polymyxin antibiotic discovered in the late 1940s, has recently reemerged as a last-line treatment option for multidrug-resistant infections. However, in recent years, colistin-resistant pathogenic bacteria have been increasingly reported worldwide. Accordingly, the presented review was undertaken to identify, integrate and synthesize current information regarding the detection and transmission of colistin-resistant bacteria across the African continent, in addition to elucidating their molecular mechanisms of resistance. PubMed, Google Scholar, and Science Direct were employed for study identification, screening and extraction. Overall, based on the developed literature review protocol and associated inclusion/exclusion criteria, 80 studies published between 2000 and 2021 were included comprising varying bacterial species and hosts. Numerous mechanisms of colistin resistance were reported, including chromosomal mutation(s) and transferable plasmid-mediated colistin resistance (encoded by mcr genes). Perhaps unexpectedly, mcr-variants have exhibited rapid emergence and spread across most African regions. The genetic variant mcr-1 is predominant in humans, animals, and the natural environment, and is primarily carried by IncHI2- type plasmid. The highest numbers of studies reporting the dissemination of colistin-resistant Gram-negative bacteria were conducted in the North African region.

Isolation, Identification, and Susceptibility Profile of E. coli, Salmonella, and S. aureus in Dairy Farm and Their Public Health Implication in Central Ethiopia

A cross-sectional study was conducted from November 2018 to May 2019 in Bishoftu and Dukem in central part of Ethiopia. The objectives of the present study were to isolate and identify S. aureus, E. coli, and Salmonella from dairy cattle, personnel, and equipment at farms. In addition to this, antimicrobial resistance profiles of the isolates were determined. A total of 607 samples consisting of fresh cow milk (125), fecal sample (211), nasal swab (211), pooled milkers' hand swabs (20), pooled floor swabs (20), and tank milk (20) samples were collected from 20 dairy farms, which included 211 animals. Structured questionnaire was designed and administered to dairy farm owners and dairy food consumers to assess their consumption behavior and antibiotics usage. The samples were examined for the presence of S. aureus, E. coli, and Salmonella following standard techniques and procedures outlined by the International Organization for Standardization. Subsequently, 62 (15.7%) of S. aureus were isolated from 396 of the totals analyzed samples for S. aureus. Out of the 62 isolated S. aureus, 35/211(16.7%), 19/125(15.2%), 6/20(30%), 2/20(10%), and 0/20(0%) were from nasal swabs, udder milk, bulk milk, pooled hand swab, and floor swabs, respectively. On the other hand, 30 (7.6%) of E. coli were isolated from 396 of the totals analyzed samples for E. coli. Out of the 30 isolated E. coli, 17/211(8.1%), 12/125(9.6%), 0/20(0%), 0/20(0%), and 1/20(5%) were from faeces, udder milk, bulk milk, pooled hand swab, and floor swabs, respectively. In line with this, 13 (4.8%) of Salmonella were isolated from 271 of the totals analyzed samples for Salmonella. Out of the 13 isolated Salmonella, 10/211(4.7%), 2/20(10%), 0/20(0%), and 1/20(5%) were from faeces, bulk milk, pooled hand swab, and floor swabs, respectively. Subsequently, 62 of S. aureus, 30 of E. coli, and 13 of Salmonella isolates were subjected to antimicrobial susceptibility testing, and all isolates were resistant to at least one or more antimicrobials tested. Penicillin, methicillin, and trimethoprim/sulfamethoxazole are drugs to which a large proportion of isolated S. aureus were highly resistant, which range from 90% to 100%. From 30 tested E. coli, they showed (83%) resistance to Tetracycline and 80% to Vancomycin. The resistance level of 13 isolated Salmonella was 69% to Nalidixic acid and 54% to Vancomycin. Multiple drug resistance was detected in high (98.4%) for S. aureus, (56.7%) for E. coli, and (53.9%) for Salmonella. High proportion of multiple drug resistant in the dairy farm alerts concern for animal and public health as these drugs are used widely for treatment and prophylaxis in animals and humans.

Multidrug resistance to commonly prescribed antibiotics in Escherichia coli isolated from barbecued beef (Suya) sold in a Nigerian City

Introduction

Suya, a form of barbecued meat widely consumed in Nigeria is a rising source of concern for the dissemination of pathogens and antibiotic resistance.

Methods

this study was carried out to determine the antibiotic resistance profile of Escherichia coli (E. coli) isolated from Suya sold in Karu Local Government Area, Nasarawa State, Nigeria. A total of three hundred (300) Suya samples were collected and screened for the presence of E. coli. An antibiotic susceptibility study was carried out on the isolated bacteria to determine their resistance profiles.

Results

the overall isolation and occurrence of E. coli was 13.3%. The isolated organisms were most resistant to Ampicillin (100%) followed by Amoxicillin/Clavulanic acid (95%), Ciprofloxacin (92.5%), Nitrofurantoin, Imipenem and Ceftriaxone (85%), Cefixime (80%), Streptomycin (77.5%), and Cotrimoxazole (77%), with a low level of resistance recorded against Gentamycin (5%). Most of the E. coli isolates had multiple resistance (MAR) to at least five antibiotics (MAR Index of = 0.5) and the most frequent MAR Index was 0.8 with 37.5% occurrence. The most frequently encountered resistance phenotype was Nitrofurantoin-Imipenem-Streptomycin-Ciprofloxacin-Ceftriaxone-Amoxicillin/clavulanic acid-Cefixime-Ampicillin. The E. coli isolates categorised based on drug resistance classes were Multi-Drug Resistance, MDR (97.5%), Pan Drug Resistance, PDR (2.5%), Non-Multi-Drug Resistance, NMDR (0.0%) and Extensive Drug Resistance, XDR (0.0%).

Conclusion

these findings indicate a potential danger of multidrug resistant organisms in circulation. Antibiotics stewardship and drug resistance surveillance is strongly recommended for all stakeholders

Review on the occurrence of the mcr-1 gene causing colistin resistance in cow's milk and dairy products

Both livestock farmers and the clinic use significant amount of antibiotics worldwide, in many cases the same kind. Antibiotic resistance is not a new phenomenon, however, it is a matter of concern that resistance genes (mcr - Mobilized Colistin Resistance - genes) that render last-resort drugs (Colistin) ineffective, have already evolved. Nowadays, there is a significant consumption of milk and dairy products, which, if not treated properly, can contain bacteria (mainly Gram-negative bacteria). We collected articles and reviews in which Gram-negative bacteria carrying the mcr-1 gene have been detected in milk, dairy products, or cattle. Reports have shown that although the incidence is still low, unfortunately the gene has been detected in some dairy products on almost every continent. In the interest of our health, the use of colistin in livestock farming must be banned as soon as possible, and new treatments should be applied so that we can continue to have a chance in fighting multidrug-resistant bacteria in human medicine.

Occurrence and Antibiogram of Escherichia coli O157 : H7 in Raw Beef and Hygienic Practices in Abattoir and Retailer Shops in Ambo Town, Ethiopia

Foodborne infections are widespread and growing public health problems in the world. Shiga toxin-producing Escherichia coli O157 : H7 is one of the most significant foodborne pathogens. This study was conducted to assess the occurrence and antibiogram of E. coli O157 : H7 from raw beef as well as hygienic and sanitary practices of meat handling in abattoir and retailer shops. Systematic random sampling technique and census methods were used to collect samples from abattoir and retailer shops, respectively. All tryptone soya broth preenriched carcass samples were subcultured onto MacConkey agar. Then, the bacterium confirmed as Escherichia coli using biochemical tests was streaked onto Sorbitol-MacConkey agar and incubated at 37°C for 24 hrs. Escherichia coli O157 : H7 was confirmed by latex agglutination kit. In vitro antimicrobial susceptibility test of Escherichia coli O157 : H7 isolates was done against 13 antimicrobials. Hygiene and sanitation data were collected using a pretested structured questionnaire and observational checklist. Pearson Chi-square and Fisher's exact two-tailed tests were performed and differences were considered significant at P ≤ 0.05. Out of 197 meat samples, 23.4% (95% confidence interval (CI): 17.6-29.9%) and 9.1% (95% CI: 5.5-14.1%) were contaminated with Escherichia coli and Escherichia coli O157 : H7, respectively. There was a significant variation in the occurrence of Escherichia coli O157 : H7 between retailer shops (19.1%) and abattoir (7.2%) (P = 0.03). The study revealed that the municipal abattoir and retailer shops in Ambo town did not adhere to the required sanitation and hygienic standards. All Escherichia coli O157 : H7 isolates were susceptible to norfloxacin, sulfamethoxazole-trimethoprim, chloramphenicol, and ceftazidime. However, all isolates were resistant to amoxicillin. Multidrug resistance was widespread and was found in 66.3% of Escherichia coli O157 : H7 isolates. The occurrence of Escherichia coli O157 : H7 was high. Therefore, fulfilling national and international meat safety requirements, training and monitoring of meat handlers, and rational use of antimicrobials are recommended.

Understanding of Colistin Usage in Food Animals and Available Detection Techniques: A Review

Progress in the medical profession is determined by the achievements and effectiveness of new antibiotics in the treatment of microbial infections. However, the development of multiple-drug resistance in numerous bacteria, especially Gram-negative bacteria, has limited the treatment options. Due to this resistance, the resurgence of cyclic polypeptide drugs like colistin remains the only option. The drug, colistin, is a well-known growth inhibitor of Gram-negative bacteria like Acinetobacter baumanni, Enterobacter cloacae, Klebsiella pneumoniae, and Pseudomonas aeruginosa. Technological advancements have uncovered the role of the mcr-1(mobilized colistin resistance) gene, which is responsible for the development of resistance in Gram-negative bacteria, which make them distinct from other bacteria without this gene. Additionally, food animals have been determined to be the reservoir for colistin resistance microbes, from which they spread to other hosts. Due to the adverse effects of colistin, many developed countries have prohibited its usage in animal foods, but developing countries are still using colistin in animal food production, thereby imposing a major risk to the public health. Therefore, there is a need for implementation of sustainable measures in livestock farms to prevent microbial infection. This review highlights the negative effects (increased resistance) of colistin consumption and emphasizes the different approaches used for detecting colistin in animal-based foods as well as the challenges associated with its detection.

Isolation, Characterization, and Quantification of Bacteria from African Sausages Sold in Nairobi County, Kenya

African sausages are local popular delicacies in Kenya. Demand for these sausages has resulted in this delicacy's vendors being on the increase. However, health risk posed to unsuspecting consumers of African sausages sold in informal, unhygienic make shift road-side kiosks in major cities of Kenya is largely unknown. A descriptive study was designed to isolate, characterize and quantify bacteria from African sausages sold in Nairobi County. A total of hundred (100) African sausages (62 roasted and 38 nonroasted) were conveniently collected from three meat eatery points of Westlands, Kangemi slum, and Pangani estates. Five genera of bacteria, namely, Staphylococcus spp. at 50.4%, Bacillus spp. at 19.5%, Streptococcus spp. 9.8%, Proteus spp. 2.4%, and E. coli spp. at 1.6%, were isolated from 80 African sausage samples. The total aerobic bacterial count range was between 1.0-9.9x10¹ and 1.0-9.9x10⁷ log cfu/g with 37 samples having total aerobic bacterial count of between 1.0-9.9 x10⁴ and 1.0-9.9 x10⁷ log cfu/g. There was no significant difference (p>0.05) in distribution of isolates and total aerobic bacterial count across geographical sites studied among the roasted and nonroasted African sausages. This study has demonstrated presence of bacteria in African sausages which are potentially zoonotic to humans. Comprehensive study is needed to sample more eatery meat points in Nairobi and other areas in order to demonstrate pathogenic attributes of these isolates and establish the respective total aerobic bacterial count. There is also need to establish the sources of bacteria due to high total aerobic bacterial count determined in the current study.

Food safety management systems performance in African food processing companies: a review of deficiencies and possible improvement strategies

This study seeks to provide insight into current deficiencies in food safety management systems (FSMS) in African food-processing companies and to identify possible strategies for improvement so as to contribute to African countries' efforts to provide safe food to both local and international markets. This study found that most African food products had high microbiological and chemical contamination levels exceeding the set (legal) limits. Relative to industrialized countries, the study identified various deficiencies at government, sector/branch, retail and company levels which affect performance of FSMS in Africa. For instance, very few companies (except exporting and large companies) have implemented HACCP and ISO 22000:2005. Various measures were proposed to be taken at government (e.g. construction of risk-based legislative frameworks, strengthening of food safety authorities, recommend use of ISO 22000:2005, and consumers' food safety training), branch/sector (e.g. sector-specific guidelines and third-party certification), retail (develop stringent certification standards and impose product specifications) and company levels (improving hygiene, strict raw material control, production process efficacy, and enhancing monitoring systems, assurance activities and supportive administrative structures). By working on those four levels, FSMS of African food-processing companies could be better designed and tailored towards their production processes and specific needs to ensure food safety.

Genotypic characterization of Escherichia coli O157:H7 isolates from different sources in the North-West Province, South Africa, using enterobacterial repetitive intergenic consensus PCR analysis

In many developing countries, proper hygiene is not strictly implemented when animals are slaughtered and meat products become contaminated. Contaminated meat may contain Escherichia coli (E. coli) O157:H7 that could cause diseases in humans if these food products are consumed undercooked. In the present study, a total of 94 confirmed E. coli O157:H7 isolates were subjected to the enterobacterial repetitive intergenic consensus (ERIC) polymerase chain reaction (PCR) typing to generate genetic fingerprints. The ERIC fragments were resolved by electrophoresis on 2% (w/v) agarose gels. The presence, absence and intensity of band data were obtained, exported to Microsoft Excel (Microsoft Office 2003) and used to generate a data matrix. The unweighted pair group method with arithmetic mean (UPGMA) and complete linkage algorithms were used to analyze the percentage of similarity and matrix data. Relationships between the various profiles and/or lanes were expressed as dendrograms. Data from groups of related lanes were compiled and reported on cluster tables. ERIC fragments ranged from one to 15 per isolate, and their sizes varied from 0.25 to 0.771 kb. A large proportion of the isolates produced an ERIC banding pattern with three duplets ranging in sizes from 0.408 to 0.628 kb. Eight major clusters (I-VIII) were identified. Overall, the remarkable similarities (72% to 91%) between the ERIC profiles for the isolate from animal species and their corresponding food products indicated some form of contamination, which may not exclude those at the level of the abattoirs. These results reveal that ERIC PCR analysis can be reliable in comparing the genetic profiles of E. coli O157:H7 from different sources in the North-West Province of South Africa.

Detection of Escherichia coli O157:H7 using immunomagnetic separation and mPCR in Turkish foods of animal origin

The present study was conducted to investigate the presence of Escherichia coli O157:H7 in food samples of animal origin and to detect its virulence genes by immunomagnetic separation technique and multiplex PCR (mPCR). A total of 500 samples (consisting of diced meat, minced meat, burger, raw cow's milk and raw cow's milk cheese) were analysed. Escherichia coli O157:H7 was detected in 5 (1%) of 500 analysed samples including two diced meat, one minced meat and two raw-milk cheese. None of the burger samples tested contained E. coli O157:H7. Three isolates obtained from minced and diced meat were found to carry stx1 , stx2 , hlyA and eaeA genes whereas two isolates from raw-milk cheese were found to harbour the stx1 , eaeA and hlyA genes. The results of this study suggest that raw meat and raw-milk cheese tested could pose public health problems in consumers with regard to their virulence factors.

SIGNIFICANCE AND IMPACT OF THE STUDY

Escherichia coli (E. coli) O157:H7 is an important human pathogen. Escherichia coli 0157:H7 infections have been associated with consumption of uncooked meat and meat products, as well as unpasteurized dairy products. This study demonstrated that without specific tests for E. coli virulence factors raw meat and raw-milk cheese could pose public health problems to Turkish consumers.

Incidence of Shiga toxin-producing Escherichia coli serogroups in ruminant's meat

To assess the presences of Escherichia coli, its serogroups, virulence factors and antibiotic resistance properties in ruminant's meat, a total of 820 raw meat samples were collected and then evaluated using culture, PCR and disk diffusion methods. Totally, 238 (29.02%) samples were positive for presence of Escherichia coli. All of the isolates had more than one virulence gene including Stx1, Stx2, eaeA and ehly. All investigated serogroups were found in beef and sheep and all except O145, O121 and O128 were found in goat. The O91, O113, O111, O103, O26 and O157 serogroups were found in camel. Totally, aadA1-blaSHV combination was the most predominant antibiotic resistance gene. The highest resistance of STEC strains was seen against penicillin while resistance to nitrofurantoin and ciprofloxacin was minimal. These findings showed that health care and meat inspection should be reconsidered in Iranian slaughterhouses and butchers.

Shiga toxin-producing Escherichia coli in beef retail markets from Argentina

Shiga toxin-producing Escherichia coli (STEC) are foodborne pathogens that cause mild or serious diseases and can lead to people death. This study reports the prevalence and characteristics of STEC O157 and non-O157 in commercial ground beef and environmental samples, including meat table, knife, meat mincing machine, and manipulator hands (n = 450) obtained from 90 retail markets over a nine-month period. The STEC isolates were serotyped and virulence genes as stx (Shiga toxin), rfb(O157)] (O157 lipopolysaccharide), fliC(H7) (H7 flagellin), eae (intimin), ehxA (enterohemolysin) and saa (STEC autoagglutinating adhesin), were determined. STEC O157 were identified in 23 (25.5%) beef samples and 16 (4.4%) environmental samples, while STEC non-O157 were present in 47 (52.2%) and 182 (50.5%), respectively. Among 54 strains isolated, 17 were STEC O157:H7 and 37 were STEC non-O157. The prevalent genotype for O157 was stx(2)/eae/ehxA/fliC(H7) (83.4%), and for STEC non-O157 the most frequent ones were stx(1)/stx(2)/saa/ehxA (29.7%); stx(2) (29.7%); and stx(2)/saa/ehxA (27%). None of the STEC non-O157 strains were eae-positive. Besides O157:H7, other 20 different serotypes were identified, being O8:H19, O178:H19, and O174:H28 the prevalent. Strains belonging to the same serotype could be isolated from different sources of the same retail market. Also, the same serotype could be detected in different stores. In conclusion, screening techniques are increasingly sensitive, but the isolation of STEC non-O157 is still a challenge. Moreover, with the results obtained from the present work, although more studies are needed, cross-contamination between meat and the environment could be suspected.

Food as a vehicle for transmission of Shiga toxin-producing Escherichia coli

Contaminated food continues to be the principal vehicle for transmission of Escherichia coli O157:H7 and other Shiga toxin-producing E. coli (STEC) to humans. A large number of foods, including those associated with outbreaks (alfalfa sprouts, fresh produce, beef, and unpasteurized juices), have been the focus of intensive research studies in the past few years (2003 to 2006) to assess the prevalence and identify effective intervention and inactivation treatments for these pathogens. Recent analyses of retail foods in the United States revealed E. coli O157:H7 was present in 1.5% of alfalfa sprouts and 0.17% of ground beef but not in some other foods examined. Differences in virulence patterns (presence of both stx1 and stx2 genes versus one stx gene) have been observed among isolates from beef samples obtained at the processing plant compared with retail outlets. Research has continued to examine survival and growth of STEC in foods, with several models being developed to predict the behavior of the pathogen under a wide range of environmental conditions. In an effort to develop effective strategies to minimize contamination, several influential factors are being addressed, including elucidating the underlying mechanism for attachment and penetration of STEC into foods and determining the role of handling practices and processing operations on cross-contamination between foods. Reports of some alternative nonthermal processing treatments (high pressure, pulsed-electric field, ionizing radiation, UV radiation, and ultrasound) indicate potential for inactivating STEC with minimal alteration to sensory and nutrient characteristics. Antimicrobials (e.g., organic acids, oxidizing agents, cetylpyridinium chloride, bacteriocins, acidified sodium chlorite, natural extracts) have varying degrees of efficacy as preservatives or sanitizing agents on produce, meat, and unpasteurized juices. Multiple-hurdle or sequential intervention treatments have the greatest potential to minimize transmission of STEC in foods.

Escherichia coli O26 in minced beef: prevalence, characterization and antimicrobial resistance pattern

Verocytotoxin-producing Escherichia coli (VTEC) non-O157 serogroups are among the most important emerging food-borne pathogen groups. In particular, the O26 serogroup is able to cause a large spectrum of illnesses in humans which have a significant public health impact as they may range from haemorrhagic colitis (HC) to haemolytic uremic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP). It is known that VTEC organisms are associated with animal reservoirs, i.e. ruminants, and foods of animal origin, especially undercooked meat and raw milk, are often involved in outbreaks. In this study, 250 minced beef samples collected at retail outlets in southern Italy were tested for the presence of E. coli O26 and the isolates were characterized and studied for their antimicrobial resistance properties. Three minced beef samples (1.2%) tested positive for E. coli O26; one isolate per positive sample was characterized. One isolate harboured the genes encoding for virulence factors intimin (eaeA) and enterohaemolysin (hlyA), while none presented verocytotoxin-encoding genes (stx1 and stx2) and all were negative at the verotoxicity assay. All the isolates showed resistance properties to at least four antimicrobial agents tested and two were multi-drug resistant (MDR). Although no verocytotoxin-encoding genes were found in the isolates, the presence of potentially pathogenic E. coli O26 strains in minced beef points to the need for proper hygiene during meat production to reduce the risk of food-borne illnesses and transmission of MDR organisms via foods to humans. This paper is the first report on the presence and characterization of E. coli O26 in minced beef marketed in Italy.

Antimicrobial resistance and genetic profiling of Escherichia coli from a commercial beef packing plant

The objective of this study was to investigate the extent of antimicrobial resistance and to genetically characterize resistant Escherichia coli recovered from a commercial beef packing plant. E. coli isolates were recovered by a hydrophobic grid membrane filtration method by direct plating on SD-39 medium. A total of 284 isolates comprising 71, 36, 55, 52, and 70 isolates from animal hides, washed carcasses, conveyers, beef trimmings, and ground beef, respectively, were analyzed. The susceptibility of E. coli isolates to 15 antimicrobial agents was evaluated with an automated broth microdilution system, and the genetic characterization of these isolates was performed by the random amplified polymorphic DNA (RAPD) method. Of the 284 E. coli isolates, 56% were sensitive to all 15 antimicrobial agents. Resistance to tetracycline, ampicillin, and streptomycin was observed in 38, 9, and 6% of the isolates, respectively. Resistance to one or more antimicrobial agents was observed in 51% of the E. coli isolates recovered from the hides but in only 25% of the E. coli from the washed carcasses. Resistance to one or more antimicrobial agents was observed in 49, 50, and 37% of the isolates recovered from conveyers, beef trimmings, and ground beef, respectively. The RAPD pattern data showed that the majority of resistant E. coli isolates were genetically diverse. Only a few RAPD types of resistant strains were shared among various sample sources. The results of this study suggest that antimicrobial-resistant E. coli isolates were prevalent during all stages of commercial beef processing and that considerably higher numbers of resistant E. coli were present on conveyers, beef trimmings, and ground beef than on dressed carcasses. This stresses the need for improving hygienic conditions during all stages of commercial beef processing and meatpacking to avoid the risks of transfer of antimicrobial-resistant bacteria to humans.

Antimicrobial resistance in Irish isolates of verocytotoxigenic Escherichia coli (E. coli)—VTEC

This study compared the antimicrobial resistance profiles of Escherichia coli O157:H7 isolates (n=257) recovered from bovine hides, minced beef and human clinical samples in Ireland, to those profiles of a range of Irish non-O157 E. coli (O111 and O26) isolates (n=31) from a variety of clinical and veterinary sources. Four multi-drug resistant (MDR) E. coli O157:H7 food isolates were identified, with resistance to 10 (1 isolate), 6 (1 isolate) and 4 (2 isolates) antimicrobial agents, respectively. Two of these isolates (resistant to 7 and 4 antimicrobial classes) were characterised further by molecular methods and found to contain class 1 integrons along with a beta-lactamase-encoding tem-1 gene. Transfer of antimicrobial resistance (ampicillin, streptomycin and sulphonamides), the tem-1 gene and markers (int1, qacEDelta1, sul1) characteristic of class 1 integrons were evident in one MDR isolate (resistant to 4 antimicrobial classes) when conjugation and transformation experiments were performed. A clinical isolate and a veterinary isolate of the O111 serotype were MDR and resistant to 4 and 3 antimicrobial classes, respectively. These data suggest that the prevalence of antimicrobial resistance among the three VTEC serotypes examined in this study is low. However, these organisms may become a public health risk should they enter the food chain.