Salmonella contamination, serovars and antimicrobial resistance profiles of cattle slaughtered in South Africa

Isolation and antimicrobial susceptibility profile of Salmonella species from slaughtered cattle carcasses and abattoir personnel at Dessie, municipality Abattoir, Northeast Ethiopia

BACKGROUND

Antibiotic-resistant Salmonella is one of the main public health concerns in the world. Isolation of Salmonella in abattoirs has been considered the core source of infection in the community from meat. Still, there is limited information on the contamination rate of cattle carcasses.

OBJECTIVE

This study aimed to document the occurrence and antimicrobial susceptibility profile of Salmonella species recovered from cattle carcass and abattoir personnel at Dessie, municipality abattoir, Northeast Ethiopia: METHODS: A total of 336 carcass swabs of abdomen, neck, and hind limb from cattle carcasses and 24 stool samples were collected from abattoir personnel using a systematic sampling method from February to April 2019. The collected samples were transported using Cary-Blair transport media and cultivated on Selenite cysteine F-broth, Brilliant green agar, and Xylose-lysine deoxycholate agar plates to isolate Salmonella species. Gram stain, colony morphology, and biochemical tests were performed to identify the isolated bacteria. An antimicrobial susceptibility test for Salmonella was performed using the Kirby-Bauer Disc Diffusion method. Descriptive statistics; both bivariable and multivariable logistic regression analysis was performed using SPSS version 25 software. P-value < 0.05 at 95% CI was considered statistically significant.

RESULTS

The prevalence of salmonella species was 8%(27/336) from all samples.'The prevalence of Salmonella isolates in cattle carcass and abattoir personnel was 8%(25/312) and 8.3%(2/24) respectively. The antimicrobial test showed that Salmonella species were 100% resistant to ampicillin, 59.3% to trimethoprim-sulfamethoxazole, 59.3% to tetracycline, and 55.6% to amoxicillin/clavulanate. From the total antimicrobial tested bacteria, 81.5%(22/27) were resistant to three and above classes of antibiotics (drug classes). Unwashed knives, carcasses, and hands of butchers during slaughtering were significantly associated (p < 0.05) with Salmonella found in carcasses.

CONCLUSIONS

Salmonella isolation rates from cattle carcasses were high, with the bacteria showing notable resistance to most tested antibiotics. Poor hygiene practices, unsanitized equipment, and unhygienic beef processing were contributing factors.

Investigation of the seasonal prevalence, phenotypic, and genotypic characteristics of Listeria monocytogenes in slaughterhouses in Burdur

AIM

This study examined Listeria monocytogenes isolates from two slaughterhouses in Burdur province, southern Turkey, over four seasons for antibiotic resistance, serogroups, virulence genes, in vitro biofilm forming capacity, and genetic relatedness.

METHODS AND RESULTS

Carcass (540) and environment-equipment surface (180) samples were collected from two slaughterhouses (S1, S2) for 1 year (4 samplings). Of the 89 (12.4%) positive isolates, 48 (53.9%) were from animal carcasses, and 41 (46.1%) from the environment-equipment surfaces. Autumn was the peak season for Listeria monocytogenes compared to summer and spring (P < 0.05). In addition, the most common serotype between seasons was 1/2c. Except for plcA and luxS genes, all isolates (100%) harbored inlA, inlC, inlJ, hlyA, actA, iap, flaA genes. Listeria monocytogenes isolates were identified as belonging to IIc (1/2c-3c; 68.5%), IVb (4b-4d-4e; 29.2%), and IIa (1/2a-3a; 2.2%) in the screening using multiplex polymerase chain reaction-based serogrouping test. A total of 65 pulsotypes and 13 clusters with at least 80% homology were determined by using pulsed field gel electrophoresis on samples that had been digested with ApaI. Thirty-four (38.2%) of the isolates were not resistant to any of the 14 antibiotics tested. The antibiotic to which the isolates showed the most resistance was rifampicin (44.9%). Serotype 1/2c was the most resistant serotype to antibiotics. Despite having biofilm-associated genes (inlA, inlB, actA, flaA, and luxS), a minority (11%) of isolates formed weak biofilm.

CONCLUSION

This study revealed seasonal changes prevalence of Listeria monocytogenes, particularly higher in autumn, posing a greater risk of meat contamination. Notably, Serotype 1/2c showed significant prevalence and antibiotic resistance. Indistinguishable isolates indicated cross-contamination, underscoring the importance of prioritized training for slaughterhouse personnel in sanitation and hygiene protocols.

High diversity of Salmonella spp. from children with diarrhea, food, and environmental sources in Kilimanjaro - Tanzania: one health approach

Salmonella is one of the most frequent causes of diarrhea globally. This study used a One Health approach to identify Salmonella species in children admitted with diarrhea and tested samples from the cases' household environment to investigate their genetic similarity using whole genome sequencing. Surveillance of hospitalized diarrhea cases among children under 5 years was conducted in rural and urban Moshi Districts in the Kilimanjaro Region of Tanzania from July 2020 through November 2022. Household visits were conducted for every child case whose parent/caregiver provided consent. Stool samples, water, domestic animal feces, meat, and milk were collected and tested for Salmonella. Isolates were sequenced on the Illumina NextSeq platform. Multilocus Sequence Typing and phylogenetic analyses were performed to map the genetic relatedness of the isolates. Salmonella was isolated from 72 (6.0%) of 1,191 samples. The prevalence of Salmonella in children with diarrhea, domestic animal feces, food, and water was 2.6% (n = 8/306), 4.6% (n = 8/174), 4.2% (n = 16/382), and 17.3% (n = 39/225), respectively. Four (1.3%) of the 306 enrolled children had a Salmonella positive sample taken from their household. The common sequence types (STs) were ST1208, ST309, ST166, and ST473. Salmonella Newport was shared by a case and a raw milk sample taken from the same household. The study revealed a high diversity of Salmonella spp., however, we detected a Salmonella clone of ST1208 isolated at least from all types of samples. These findings contribute to understanding the epidemiology of Salmonella in the region and provide insight into potential control of foodborne diseases through a One Health approach.

Virulence and Antimicrobial Resistance Profiling of Salmonella Serovars Recovered from Retail Poultry Offal in KwaZulu-Natal Province, South Africa

As poultry organ meat is widely consumed, especially in low- and middle-income countries, there is reason to investigate it as a source of Salmonella infections in humans. Consequently, the aim of this study was to determine the prevalence, serotypes, virulence factors and antimicrobial resistance of Salmonella isolated from chicken offal from retail outlets in KwaZulu-Natal, South Africa. Samples (n = 446) were cultured for the detection of Salmonella using ISO 6579-1:2017. Presumptive Salmonella were confirmed using matrix-assisted laser desorption ionisation time-of-flight mass spectrometry. Salmonella isolates were serotyped using the Kauffmann-White-Le Minor scheme and antimicrobial susceptibility was determined by the Kirby-Bauer disk diffusion technique. A conventional PCR was used for the detection of Salmonella invA, agfA, lpfA and sivH virulence genes. Of the 446 offal samples, 13 tested positive for Salmonella (2.91%; CI = 1.6-5). The serovars included S. Enteritidis (n = 3/13), S. Mbandaka (n = 1/13), S. Infantis (n = 3/13), S. Heidelberg (n = 5/13) and S. Typhimurium (n = 1/13). Antimicrobial resistance against amoxicillin, kanamycin, chloramphenicol and oxytetracycline was found only in S. Typhimurium and S. Mbandaka. All 13 Salmonella isolates harboured invA, agfA, lpfA and sivH virulence genes. The results show low Salmonella prevalence from chicken offal. However, most serovars are known zoonotic pathogens, and multi-drug resistance was observed in some isolates. Consequently, chicken offal products need to be treated with caution to avoid zoonotic Salmonella infections.

Multiple-Locus Variable-Number Tandem Repeat Analysis Genotypes of Listeria monocytogenes Isolated from Farms, Abattoirs, and Retail in Gauteng Province, South Africa

ABSTRACT

The use of multiple-locus variable-number analysis (MLVA) of tandem repeats (TRs) for subtyping Listeria monocytogenes has proven to be reliable and fast. This study determined the MLVA genotypes of 60 isolates of L. monocytogenes recovered from cattle farms, abattoirs, and retail outlets in Gauteng province, South Africa. The distribution of the 60 L. monocytogenes isolates analyzed by type of sample was as follows: raw beef (28, 46.7%), ready-to-eat beef products (9, 15.0%), beef carcass swabs (9, 15.0%), cattle environment (6, 10.0%), and cattle feces (8, 13.3%). The serogroups of the isolates were determined using PCR and the MLVA genotypes based on six selected loci. The frequency of the 60 serogroups detected was as follows: 1/2a-3a (IIa) (27, 45.0%); 4b-4d-4e (1Vb) (24, 40.0%); 1/2c-3c (IIc) (8, 13.3%); and 1/2b-3b (IIb) (1, 1.7%). MLVA successfully clustered genetically related isolates and differentiated nonrelated isolates, irrespective of their sources, sample types, and serogroups, as demonstrated by 16 MLVA pattern types detected. For serogroup 4b-4d-4e (IVb), there was no variation in TRs LM-TR2, LM-TR4, and LM-TR6, which each contained only one allele (02, 00, and 93, respectively). However, across the sources and sample types of isolates, there was variation in serogroup 4b-4d-4e (IVb): LM-TR1 contained 00, 03, and 05; LM-TR3 contained 14, 20, and 22; and LM-TR5 contained 14, 21, and 25. Similar patterns of variation in the TRs were detected in the other serogroups (1/2a-3a, 1/2b-3b, and 1/2c-3c). BioNumeric data analysis identified at least five types in Gauteng province. MLVA epidemiologically clustered the related isolates and differentiated unrelated isolates.

HIGHLIGHTS

Antimicrobial Resistance, Enterotoxin and mec Gene Profiles of Staphylococcus aureus Associated with Beef-Based Protein Sources from KwaZulu-Natal Province, South Africa

Annually, approximately 23,000 cases of food poisoning by Staphylococcus aureus enterotoxins are reported worldwide. The aim of this study was to determine the occurrence and characterize S. aureus on beef and beef products in South Africa. Organ meats (n = 169), raw processed meat (n = 110), raw intact (n = 53), and ready-to-eat meats (n = 68) were obtained from 25 retail outlets. S. aureus was isolated and enumerated according to the ISO 6888-1 method. Identification of the strains was performed by MALDI-TOF MS. The antimicrobial resistance was determined using the disc diffusion test. The presence of methicillin-resistance genes and the staphylococcal enterotoxin genes was determined by PCR. Prevalence was low (13/400; CI 1.7–5) and all but one positive sample were from organ meats. Eight isolates were resistant to at least one antibiotic. Two isolates carried the mecC gene. All the isolates tested positive for seg, seh, sei, and sep, whilst 53.8% were positive for sea. None of the isolates was positive for ser, sej, seb, sec, or sed. The prevalence of S. aureus was low, with organ meats being the most contaminated. The presence of mecC-positive MRSA and of enterotoxins warrants further investigation and risk assessment.

Presence and Virulence Characteristics of Shiga Toxin Escherichia coli and Non-Shiga Toxin-Producing Escherichia coli O157 in Products from Animal Protein Supply Chain Enterprises in South Africa

Consumption of food that is contaminated with Shiga toxin-producing Escherichia coli (STEC) has been linked to serious foodborne disease outbreaks. Our aim was to provide a descriptive study on the presence and virulence factors of STEC and non-STEC O157 isolates recovered from 2017 diverse meat and meat product samples from all provinces of South Africa (n = 1758) and imported meat from South Africa's major ports of entry (n = 259). A cross-sectional study was undertaken to analyze raw intact meat, raw processed (nonintact) meat, and ready-to-eat (RTE) meat from cattle, game, sheep, pork, and poultry. Isolation was performed using International Organization for Standardization-based microbiological techniques, while detection and characterization were performed using real-time PCR (RT-PCR) and conventional PCR targeting the stx1, stx2, eae, and ehxA genes. A total of 28 of 1758 (1.59%; confidence interval [CI] 1.1-2) samples from the domestic market tested positive (n = 10 Escherichia coli O157:H7; n = 14 Escherichia coli O157: non-H7; and n = 4 non-O157 STEC), while 4/259 (1.54%; CI 0.4-4) samples from ports of entry tested positive for Escherichia coli O157:H7 based on RT-PCR. On average, diverse samples from domestic meat and meat products from cattle showed the highest number of positive samples (22/1758; 1.3%; CI 0.8-2). RT-PCR detected more positive samples (n = 32) compared with culture (n = 17). Sixteen different virulence factor combinations were observed. Our findings demonstrate a relatively low presence of diverse STEC strains along the meat value chain. To our knowledge, this is the first extensive report in South Africa to analyze STEC and non-STEC O157 from local and imported samples from many animal species. This is important as it reveals virulence factors in STEC strains circulating in meat and meat products in South Africa, which contribute to the risk of infection.

Spread of Nontyphoidal Salmonella in the Beef Supply Chain in Northern Tanzania: Sensitivity in a Probabilistic Model Integrating Microbiological Data and Data from Stakeholder Interviews

East Africa is a hotspot for foodborne diseases, including infection by nontyphoidal Salmonella (NTS), a zoonotic pathogen that may originate from livestock. Urbanization and increased demand for animal protein drive intensification of livestock production and food processing, creating risks and opportunities for food safety. We built a probabilistic mathematical model, informed by prior beliefs and dedicated stakeholder interviews and microbiological research, to describe sources and prevalence of NTS along the beef supply chain in Moshi, Tanzania. The supply chain was conceptualized using a bow tie model, with terminal livestock markets as pinch point, and a forked pathway postmarket to compare traditional and emerging supply chains. NTS was detected in 36 (7.7%) of 467 samples throughout the supply chain. After combining prior belief and observational data, marginal estimates of true NTS prevalence were 4% in feces of cattle entering the beef supply and 20% in raw meat at butcheries. Based on our model and sensitivity analyses, true NTS prevalence was not significantly different between supply chains. Environmental contamination, associated with butchers and vendors, was estimated to be the most likely source of NTS in meat for human consumption. The model provides a framework for assessing the origin and propagation of NTS along meat supply chains. It can be used to inform decision making when economic factors cause changes in beef production and consumption, such as where to target interventions to reduce risks to consumers. Through sensitivity and value of information analyses, the model also helps to prioritize investment in additional research.

One Health Perspective of Salmonella Serovars in South Africa Using Pooled Prevalence: Systematic Review and Meta-Analysis

Salmonella is a bacterium that is commonly associated with food-borne infections and is regarded as one of the most important pathogens in public health. Salmonella serovars, particularly Typhimurium and Enteritidis, which are widely distributed globally, mainly result in outbreaks commonly linked to the consumption of animal products. This study is a systematic review and meta-analysis of studies reporting the prevalence of Salmonella serovars from one health perspective that included human, environmental, and animal samples in South Africa. PubMed, ScienceDirect, African Journals Online, and Scopus databases were used to conduct extensive searches of articles which were ultimately included or excluded following the Systematic Reviews and Meta-Analysis (PRISMA) guidelines. According to the data obtained in this review, the overall pooled prevalence estimates (PPE) of Salmonella serovars detection were 79.6%, 61.6%, 56.5%, and 43.2% for human, environment, animal, and environment/animal samples in South Africa, respectively. The majority of the studies (50%) used the polymerase chain reaction (PCR) technique for the detection of Salmonella serovars, followed by culture methods (26.7%), while 20% used serotyping. The PPE for nontyphoidal Salmonellae (NTS) was 65.6% and 34.4% for Salmonella Typhimurium and Salmonella Enteritidis, respectively. Our data further shows that 3 serovars, namely, Salmonella Typhimurium, Salmonella Enteriditis, and Salmonella Hadar, have been isolated from animals, humans, and the environment in South Africa. Our results highlight the ongoing spread of Salmonella spp. especially on animals which might end up infecting humans via direct contact with infected animals or eating infected animal products. This calls for deliberate “One Health” epidemiological studies in order to document information on the transmission between humans, animals, and the environment. This will ultimately result in the formulation of a consolidated salmonellosis control policy by the environmental, human, and veterinary health sectors.

Virulence Factors and Antimicrobial Resistance in Salmonella Species Isolated from Retail Beef in Selected KwaZulu-Natal Municipality Areas, South Africa

Salmonellosis and antimicrobial resistance caused by non-typhoidal Salmonella are public health concerns. This study aimed at determining prevalence, serovars, virulence factors and antimicrobial resistance of Salmonella from beef products. Four-hundred beef samples from 25 retail outlets in KwaZulu-Natal, South Africa were analyzed for Salmonella using standard methods, confirmation with matrix-assisted laser desorption ionization–time of flight and serotyping according to the White–Kauffmann–Le Minor scheme. The Kirby Bauer disk diffusion method was used to determine antimicrobial resistance against Cefotaxime, Kanamycin, Ampicillin, Amoxicillin, Trimethoprim Sulfamethoxazole, Ciprofloxacin, Chloramphenicol, Gentamicin Cefoxitin and Tetracycline. A polymerase chain reaction was performed to detect invA, agfA, lpfA, hilA, sivH, sefA, sopE, and spvC virulence genes. Salmonella was observed in 1.25% (5/400) of the samples. Four serovars (Enteritidis, Hadar, Heidelberg, Stanley) were identified. Almost all Salmonella were susceptible to all antimicrobials except S. Enteritidis isolate that was resistant to Tetracycline, Ampicillin and Amoxicillin. All Salmonella isolates carried at least two virulence factors. The findings indicate low Salmonella prevalence in meat from selected KZN retail beef; however, routine surveillance to monitor risk associated with virulence factors is required to mitigate potential outbreaks. The resistant S. Enteritidis highlights a need to routinely monitor antimicrobial resistance in order to enhance human health.

Prevalence of Antibiotic Resistance in Salmonella Serotypes Concurrently Isolated from the Environment, Animals, and Humans in South Africa: A Systematic Review and Meta-Analysis

One of the main global concerns is the usage and spread of antibiotic resistant Salmonella serovars. The animals, humans, and environmental components interact and contribute to the rapid emergence and spread of antimicrobial resistance, directly or indirectly. Therefore, this study aimed to determine antibiotic resistance (AR) profiles of Salmonella serotypes isolated from the environment, animals, and humans in South Africa by a systematic review and meta-analysis. The preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines were followed to search four databases for studies published from 1980 to 2021, that reported the antibiotic resistance profiles of Salmonella serotypes isolated in South Africa. The AR was screened from 2930 Salmonella serotypes which were isolated from 6842 samples. The Western Cape province had high pooled prevalence estimates (PPE) of Salmonella isolates with AR profiles followed by North West, Gauteng, and Eastern Cape with 94.3%, 75.4%, 59.4%, and 46.2%, respectively. The high PPE and heterogeneity were observed from environmental samples [69.6 (95% CI: 41.7−88.3), Q = 303.643, I² = 98.353, Q-P = 0.045], animals [41.9 (95% CI: 18.5–69.5), Q = 637.355, I² = 98.745, Q-P = 0.577], as well as animals/environment [95.9 (95% CI: 5.4−100), Q = 55.253, I² = 96.380, Q-P = 0.300]. The majority of the salmonella isolates were resistant to sulphonamides (92.0%), enrofloxacin and erythromycin (89.3%), oxytetracycline (77.4%), imipenem (72.6%), tetracycline (67.4%), as well as trimethoprim (52.2%), among the environment, animals, and humans. The level of multidrug-resistance recorded for Salmonella isolates was 28.5% in this review. This study has highlighted the occurrence of AR by Salmonella isolates from animals, humans, and environmental samples in South Africa and this calls for a consolidated “One Health” approach for antimicrobial resistance epidemiological research, as well as the formulation of necessary intervention measures to prevent further spread.

Antimicrobial Use and Resistance in Agriculture and Food Production Systems in Africa: A Systematic Review

In Africa, there is dearth of information on antimicrobial use (AMU) in agriculture and food production systems and its consequential resistance in pathogens that affect animal, human and environmental health. Data published between 1980 and 2021 on the magnitude of AMU and AMR in agriculture and food productions systems in Africa were reviewed. Data from 13-27 countries in Africa indicate that 3558-4279 tonnes of antimicrobials were used in animals from 2015 to 2019. Tetracyclines and polypeptides contributed the largest proportion of antimicrobials used. Cattle and poultry production account for the largest consumption of antimicrobials in Africa. Although limited studies have reported AMR in crops, fish and beekeeping, AMR from a variety of farm animals has been substantially documented in Africa. Some countries in Africa have developed policies/plans to address AMU and AMR in agriculture and food production systems; however, their enforcement is challenged by weak regulations. In conclusion, although there is limited information on the quantities of antimicrobials used in agriculture and food production system, the levels of AMR are high. There is a need to strengthen regulatory authorities with a capacity to monitor AMU in agriculture and food production systems in Africa.

Assessment of beef carcass contamination with Salmonella and E. coli O 157 in slaughterhouses in Bishoftu, Ethiopia

Background

Salmonella and E. coli O157 are common causes of foodborne diseases. Evisceration and de-hiding steps can lead to carcass contamination during slaughter operation. In Ethiopia, information on the association between the presence of these pathogens in the rectal content and/or on the hide of cattle and their presence on the carcass is lacking.

Methods

The aim of this study was to assess the sources of beef carcass contamination with Salmonella and E. coli O157 during slaughter. Rectal contents and hide- and carcass-swabs (from three sites: foreleg, brisket and hind leg) were collected from 70 beef cattle at two small scale slaughterhouses. Isolates were genotyped by the Pulsed Field Gel Electrophoresis method and tested for resistance against 14 microbial drugs.

Results

Salmonella was detected at equal proportions (7.1%) in rectal content samples and hide swabs. E. coli O157 was detected in 8.6% of the rectal contents and 4.3% of the hide swabs. The proportion of contaminated carcasses was 8.6% for Salmonella and 7.1% for E. coli O157. Genetic linkage between the Salmonella and E. coli O157 isolates from the rectal contents and/or hides and carcasses were observed only in a few cases (2 and 1 carcasses, respectively) indicating the limited direct transfer of the pathogens from the feces and/or hide to the carcass during slaughter. Most carcasses became positive by cross contamination. All the S. Typhimurium isolates (n = 8) were multidrug resistant being resistant to ampicillin, chloramphenicol, sulfamethoxazole and tetracycline. The two S. Dublin isolates were resistant to colistin. All E. coli O157 isolates were susceptible to the antimicrobials tested.

Conclusion

The results indicated that cross contamination may be an important source for carcass contamination.

Carriage, Risk Factors, and Antimicrobial Resistance Patterns of Salmonella Isolates from Raw Beef in Jimma, Southwestern Ethiopia

Purpose

Consumption of raw beef infected with multidrug-resistant Salmonella is pertinent to the world public health risk of antimicrobial resistance. Henceforth, this study aimed to investigate the carriage, antimicrobial resistance (AR) patterns, and the revealing risk factors of Salmonella-contaminating beef in abattoirs and butcher shops in Jimma town.

Methods

A cross-sectional study was conducted to investigate the carriage and AR patterns and to reveal the risk factors of beef contaminated by Salmonella spp. Three hundred and forty-eight swab samples were collected from abattoirs (n=210) and butcher shops (n=138) and the conventional cultural methods were employed for identification of Salmonella. Isolates were subjected to 12 antimicrobials using the Kirby-Bauer disk diffusion method for AR patterns.

Results

The occurrence of Salmonella isolates from the abattoir samples was 11.4%, whereas about 6.52% of isolates were recovered from butcher shops. Educational status (abattoir: odds ratio (OR)=8.40, confidence interval (CI)=1.186-59.493; butcher shops: OR=9.17, CI=1.15-73.239), job related training (abattoir: OR=5.50, CI=1.065-28.416), contamination risk perception (abattoir: OR=5.31, CI=1.256-22.489), neatness of knives (abattoir: OR=7.6, CI=0.892-65.376), source of contamination (abattoir: OR=8.44, CI=1.682-42.39), wearing of protective cloth (butcher shops: OR=8.44, CI=1.682-42.39), manner of hand washing (butcher shops: OR=7.25, CI=1.210-43.442), and money handling (butcher shops: OR= 9.69, CI=1.578-59.474) were among the potential risk factors significantly associated with Salmonella carcass contamination in the abattoir and butcher shops. Of the 33 Salmonella isolates, 14 (58.3%) and six (66.7%) of the abattoir and butcher shops isolates, correspondingly, were resistant to two or more antibiotics.

Conclusion

The finding of this investigation exhibited extensive multidrug-resistant Salmonella isolates in the study setting. Hence, establishing standard meat safety requirements and provision of training for meat handlers and prudent use of antimicrobials are recommended.

Antimicrobial Resistance Profiles of Salmonella Isolates on Chickens Processed and Retailed at Outlets of the Informal Market in Gauteng Province, South Africa

The study determined the antimicrobial resistance profiles of Salmonella on chickens processed and retailed at outlets of the informal markets in Gauteng province, South Africa. The study also investigated the relationship of antimicrobial resistant Salmonella to the source and type of samples and their serotypes. Carcass swabs, cloacal swabs and carcass drips were randomly collected from each of 151 slaughtered chickens from six townships. Isolation and identification were performed using standard and polymerase chain reaction (PCR) methods. The disc diffusion method was used to determine the resistance of Salmonella isolates to 16 antimicrobial agents and PCR to determine their serovars. Ninety-eight (64.9%) of the 151 chickens were contaminated with Salmonella of which 94.9% (93/98) were resistant serovars. The frequency of antimicrobial resistance of Salmonella isolates was high to erythromycin (94.9%) and spectinomycin (82.7%) but was low to ciprofloxacin (1.0%) and norfloxacin (1.0%) (p < 0.05). All 170 isolates of Salmonella tested exhibited resistance to one or more antimicrobial agents and the frequency varied significantly (p < 0.05) across the townships, the type of samples and the serovars. The prevalence of multidrug resistance (MDR) in Salmonella was 81.8% (139/170). Our findings pose zoonotic, food safety and therapeutic risks to workers and consumers of undercooked, contaminated chickens from these outlets.

Microbial Communities of Meat and Meat Products: An Exploratory Analysis of the Product Quality and Safety at Selected Enterprises in South Africa

Consumption of food that is contaminated by microorganisms, chemicals, and toxins may lead to significant morbidity and mortality, which has negative socioeconomic and public health implications. Monitoring and surveillance of microbial diversity along the food value chain is a key component for hazard identification and evaluation of potential pathogen risks from farm to the consumer. The aim of this study was to determine the microbial diversity in meat and meat products from different enterprises and meat types in South Africa. Samples (n = 2017) were analyzed for Yersinia enterocolitica, Salmonella species, Listeria monocytogenes, Campylobacter jejuni, Campylobacter coli, Staphylococcus aureus, Clostridium perfringens, Bacillus cereus, and Clostridium botulinum using culture-based methods. PCR was used for confirmation of selected pathogens. Of the 2017 samples analyzed, microbial ecology was assessed for selected subsamples where next generation sequencing had been conducted, followed by the application of computational methods to reconstruct individual genomes from the respective sample (metagenomics). With the exception of Clostridium botulinum, selective culture-dependent methods revealed that samples were contaminated with at least one of the tested foodborne pathogens. The data from metagenomics analysis revealed the presence of diverse bacteria, viruses, and fungi. The analyses provide evidence of diverse and highly variable microbial communities in products of animal origin, which is important for food safety, food labeling, biosecurity, and shelf life limiting spoilage by microorganisms.

Enhanced Antibacterial Activity of Silver Nanoparticles Combined with Hydrogen Peroxide Against Multidrug-Resistant Pathogens Isolated from Dairy Farms and Beef Slaughterhouses in Egypt

Purpose

The last few decades have witnessed a rapid and global increase in multidrug-resistant bacteria (MDR) emergence.

Methods

The aim of the current study is to isolate the most common MDR bacteria from dairy farms and beef slaughterhouses followed by evaluation of their antimicrobial resistance pattern and assessment of the antibacterial activity of AgNPs-H₂O₂ as an alternative to conventional antibiotics. In this regard, 200 samples were collected from two dairy farms and one beef slaughterhouse located in Dakhliya Governorate, Egypt.

Results

Interestingly, out of 120 collected samples from dairy farms, the prevalence of the isolated strains was 26.7, 23.3, 21.7, 16.7, and 11.7% for S. typhimurium, E. coli O157:H7, L. monocytogenes, K. pneumoniae and P. aeruginosa, respectively. Meanwhile, the overall prevalence was 30, 25, 22.5, 17.5, and 5% for E. coli O157:H7, L. monocytogenes, S. typhimurium, P. aeruginosa, and K. pneumoniae, respectively, for the 80 samples collected from a beef slaughterhouse. The antimicrobial susceptibility pattern elucidated that all isolated strains exhibited resistance to at least four of the tested antimicrobials, with multiple-antibiotic resistance index values (MAR) ranging between 0.44 and 0.88. Furthermore, the commercial AgNPs-H₂O₂ product was characterized by transmission electron microscopy (TEM) and zeta potential that showed spherical particles with a surface charge of -0.192 mV. The antimicrobial activity of synergized nano-silver (AgNP) with H₂O₂ product toward MDR strains was assessed via measuring minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and time-kill curve.

Conclusion

The present data report high prevalence rates of MDR pathogens in dairy farms and abattoirs. More importantly, AgNPs-H₂O₂ exerted broad-spectrum bactericidal activity toward MDR bacterial strains, suggesting their promising usage as safe, ecofriendly, cost-effective antibacterial agents. To our knowledge, this study is a pioneer in investigating the potential alternative antimicrobial role of silver nanoparticles for control of multiple drug-resistant pathogens in Egypt.

Surveillance of Salmonella spp. in the environment of public hospitals in KwaZulu-Natal, South Africa

AIM

To investigate the dissemination of Salmonella spp. within four levels of government hospitals in KwaZulu-Natal, South Africa.

METHODS

The identification of Salmonella spp. was performed by amplification of the invA gene. Isolates were subjected to antimicrobial susceptibility testing and molecular characterization of eight resistance genes (qnrA, qnrB, qnrS, tetA, tetB, tetC, tetG, ermB) and three virulence genes (sitC, spvA, spv). Genetic relatedness between isolates was determined using enterobacterial repetitive intergenic consensus (ERIC) polymerase chain reaction.

FINDINGS

Ninety-four isolates were obtained. The largest source of isolates was the regional hospital. Paediatric wards had the highest prevalence of isolates. Nurses' tables contained the most isolates out of all sites sampled. Twenty-two clusters indicating diverse isolates were obtained via molecular typing. Four main ERIC types were identified, each unique to a specific hospital. A possibility of dissemination across the wards was noted as highly related isolates were present at various sites within the wards. Many of these sites were highly trafficked areas by healthcare staff. Ten multi-drug-resistant isolates were found.

CONCLUSIONS

This study suggests that infection prevention and control strategies that involve environmental cleaning and decontamination may not be enough, or adhered to sufficiently, to prevent the dissemination of Salmonella spp.

Prevalence of Campylobacter and Salmonella in African food animals and meat: A systematic review and meta-analysis

BACKGROUND

Campylobacter and Salmonella, particularly non-typhoidal Salmonella, are important bacterial enteric pathogens of humans which are often carried asymptomatically in animal reservoirs. Bacterial foodborne infections, including those derived from meat, are associated with illness and death globally but the burden is disproportionately high in Africa. Commercial meat production is increasing and intensifying in many African countries, creating opportunities and threats for food safety.

METHODS

Following Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines, we searched six databases for English language studies published through June 2016, that reported Campylobacter or Salmonella carriage or infection prevalence in food animals and contamination prevalence in food animal products from African countries. A random effects meta-analysis and multivariable logistic regression were used to estimate the species-specific prevalence of Salmonella and Campylobacter and assess relationships between sample type and region and the detection or isolation of either pathogen.

RESULTS

Seventy-three studies reporting Campylobacter and 187 studies reporting Salmonella across 27 African countries were represented. Adjusted prevalence calculations estimate Campylobacter detection in 37.7% (95% CI 31.6-44.3) of 11,828 poultry samples; 24.6% (95% CI 18.0-32.7) of 1975 pig samples; 17.8% (95% CI 12.6-24.5) of 2907 goat samples; 12.6% (95% CI 8.4-18.5) of 2382 sheep samples; and 12.3% (95% CI 9.5-15.8) of 6545 cattle samples. Salmonella were detected in 13.9% (95% CI 11.7-16.4) of 25,430 poultry samples; 13.1% (95% CI 9.3-18.3) of 5467 pig samples; 9.3% (95% CI 7.2-12.1) of 2988 camel samples; 5.3% (95% CI 4.0-6.8) of 72,292 cattle samples; 4.8% (95% CI 3.6-6.3) of 11,335 sheep samples; and 3.4% (95% CI 2.2-5.2) of 4904 goat samples. 'External' samples (e.g. hide, feathers) were significantly more likely to be contaminated by both pathogens than 'gut' (e.g. faeces, cloaca) while meat and organs were significantly less likely to be contaminated than gut samples.

CONCLUSIONS

This study demonstrated widespread prevalence of Campylobacter species and Salmonella serovars in African food animals and meat, particularly in samples of poultry and pig origin. Source attribution studies could help ascertain which food animals are contributing to human campylobacteriosis and salmonellosis and direct potential food safety interventions.

Colorimetric aptasensor for detecting Salmonella spp., Listeria monocytogenes, and Escherichia coli in meat samples

In this study, we successfully developed a simple and rapid method for simultaneous detection of Salmonella spp., Listeria monocytogenes, and Escherichia coli using gold nanoparticles and the aptamer aptasensor. We screened 25 specific DNA aptamer candidates against these pathogens using whole-cell Systematic Evolution of Ligands by EXponential enrichment. Among them, Ap6 was selected due to its low energy minimization values of -12.25 and -27.67 kcal/mol derived from MFold and RNAFold analysis, respectively. The assay presented in this study allowed the visual colorimetric detection of labeled colloidal gold nanoparticles as well as determination of UV absorbance at 625 and 525 nm under optimized conditions. The detection limit of this aptasensor was as less as 10⁵ CFU/ml. A random investigation of 50 meat samples, including ham and chicken sausages, collected from the local market revealed 96% accuracy, 96% specificity, and 100% sensitivity of the assay. The colorimetric aptasensor can accomplish one-step detection without pre-culture, DNA extraction, and amplification. Hence, it is an easy, rapid, specific, and qualitative assay that can be used as a point-of-care testing to directly detect multiplex foodborne pathogens.

Molecular Detection Of Multidrug-Resistant Salmonella Isolated From Livestock Production Systems In South Africa

BACKGROUND

Antibiotic-resistant bacterial pathogens associated with livestock remain a major concern worldwide as they get transmitted from animals to humans and cause foodborne and zoonotic diseases.

METHODS

Antimicrobial resistance in livestock-associated Salmonella spp in South Africa was investigated using molecular DNA methods. Three hundred and sixty-one environmental faecal samples were randomly collected from avian (chicken and ducks), cows, pigs, goats, and sheep. Salmonella spp. were isolated on selective media and were confirmed using the polymerase chain reaction. Antimicrobial susceptibility testing against ampicillin, chloramphenicol, ciprofloxacin, ceftriaxone, azithromycin, tetracycline, amoxicillin-clavulanate and trimethoprim-sulfamethoxazole was determined using the Kirby-Bauer disk diffusion method. Isolates were screened for the presence of blaTEM-1, blaCMY-2, tetA, tetC, sul2 and dfrA7 resistance genes by PCR.

RESULTS

Most of the isolates were resistant to ampicillin (64%), tetracycline (63%), amoxicillin-clavulanate (49%), trimethoprim-sulfamethoxazole (38%), and ceftriaxone (20%). Eight percent of the tested isolates were ciprofloxacin-resistant Salmonella spp. Multidrug resistance was observed with the mean multiple antibiotic resistance (MAR) index of 0.31. The study demonstrated that 43% of the isolates were multiple drug resistant. The prevalence rates of resistance genes were 44% for blaTEM-1 , 35% for blaCMY-2 , 21% for sul2, 18% for tetC, 14% for dfrA7 and 8% for tetA.

CONCLUSION

Resistance to ceftriaxone, detection of blaCMY-2 gene and the high level of intermediate susceptibility (33%) against ciprofloxacin suggested that livestock carry problematic Salmonella spp. This study used the global one-health initiative to report the potential public health risks of livestock-associated pathogens and highlights the importance of monitoring the trends of antimicrobial resistance for sustainability of antibiotics.