Antimicrobial Resistance of Salmonella enterica Isolates from Tonsil and Jejunum with Lymph Node Tissues of Slaughtered Swine in Metro Manila, Philippines

Prevalence and Antimicrobial Susceptibility of Foodborne Pathogens from Raw Livestock Meat in China, 2021

The rising prevalence of pathogenic bacteria in livestock meat poses a growing public health concern in China. The determination of antimicrobial resistance (AMR) is critical for the clinical management of foodborne infections stemming from livestock meat consumption. This study aimed to assess the prevalence of pathogenic bacteria in livestock meat (pork, beef, and mutton) sampled in China in 2021 and to identify the most common AMR patterns among the isolated pathogens. A total of 2515 raw livestock meat samples were collected across 15 provinces in China during 2021. Pathogen detection, including Listeria monocytogenes, Salmonella, and diarrheagenic Escherichia coli (DEC), followed China's national food safety standards. All Salmonella isolates underwent serotyping via slide agglutination. Antimicrobial susceptibility of Salmonella and DEC isolates was assessed using the broth dilution method. The detection rates for L. monocytogenes, Salmonella, and DEC in raw livestock meat were 9.06% (228/2, 515), 10.54% (265/2, 515), and 6.16% (155/2, 515), respectively. Pork showed the highest contamination rates for Salmonella and DEC, with prevalence rates of 17.60% (214/1, 216, χ2 = 124.62, p < 0.05) and 7.89% (96/1, 216, χ2 = 14.466, p < 0.05), respectively. L. monocytogenes contamination was notably higher in chilled (14.43%, 84/582) and frozen (12.39%, 55/444) meat than in fresh meat (χ2 = 43.510, p < 0.05). In contrast, Salmonella (12.09%, 180/1489, χ2 = 15.173, p < 0.05) and DEC (7.25%, 108/1489, χ2 = 12.275, p < 0.05) were more prevalent in fresh meat than in chilled or frozen samples. The predominant Salmonella serotypes identified were Salmonella enterica subsp. enterica serovar Typhimurium, followed by Salmonella enterica serovar Derby, Salmonella enterica serovar Rissen, Salmonella enterica serovar London, and Salmonella enterica serotype Enteritidis. Enteroaggregative E. coli was the most frequent pathotype among DEC (84.7%, 133/157), followed by enteropathogenic E. coli (8.3%, 13/157) and enterohemorrhagic E. coli (5.1%, 8/157). Among the 14 tested antimicrobial agents, Salmonella isolates demonstrated an overall resistance rate of 87.50%, while DEC exhibited a resistance rate of 84.70%. Ampicillin and tetracycline showed the highest resistance rates in both pathogens. Multi-drug resistance (MDR) was observed in 67.53% of Salmonella isolates (183 isolates) and 57.96% of DEC isolates (91 isolates). This study highlights the significant contamination of retail raw livestock meat in China by L. monocytogenes, Salmonella, and DEC. The high resistance of MDR in both pathogens poses serious public health risks. Chinese food safety and veterinary authorities should implement stricter measures to control pathogen contamination and regulate the use of antimicrobials in livestock to mitigate these risks.

Development of a closed-tube, calcein-based loop-mediated isothermal amplification assay to detect Salmonella spp. in raw meat samples

Foodborne pathogens compromise food safety and public health, and Salmonella spp. are among the major pathogenic bacteria that cause outbreaks worldwide. Proper surveillance through timely and cost-effective detection methods across the food animal production chain is crucial to prevent Salmonella outbreaks and agricultural losses. Traditional culture methods are labor- and resource-intensive, with lengthy turnaround times. Meanwhile, conventional molecular tools, such as PCR and qPCR, are expensive and require technical skills and equipment. Loop-mediated isothermal amplification (LAMP) is a simple, rapid, inexpensive, highly sensitive, and specific molecular assay that does not require expensive equipment. Hence, this study developed and optimized a closed-tube, calcein-based LAMP assay to detect Salmonella using the invA gene and performed evaluation and validation against conventional PCR. The LAMP assay showed high specificity and sensitivity. It showed 10-fold higher sensitivity than conventional PCR, at <1 ng/μL DNA concentrations. Meanwhile, for CFU/mL, LAMP assay showed 1000-fold higher sensitivity than conventional PCR at 4.8 × 103 cells/mL than 4.8 × 107 cells/mL, respectively. For parallel testing of 341 raw meat samples, after conventional culture enrichment (until Rappaport-Vassiliadis broth), the optimized LAMP assay showed 100% detection on all samples while conventional PCR showed 100%, 99.04%, and 96.64% for raw chicken, beef, and pork samples, respectively. Meanwhile, a shortened enrichment protocol involving 3-h incubation in buffered peptone water only, showed lower accuracy in tandem with the optimized LAMP assay ranging from 55 to 75% positivity rates among samples. These suggest that the optimized LAMP assay possesses higher sensitivity over conventional PCR for invA gene detection when coupled with conventional enrichment culture methods. Hence, this assay has potential as a powerful complementary or alternative Salmonella detection method to increase surveillance capacity and protect consumer food safety and public health worldwide.

Use of veterinary medicinal products in the Philippines: regulations, impact, challenges, and recommendations

Agricultural production is a major driver of the Philippine economy. Mass production of animal products, such as livestock and poultry farming, is one of the most prominent players in the field. Filipino farmers use veterinary medicinal products (VMPs) when raising agricultural animals to improve animal growth and prevent diseases. Unfortunately, the extensive use of VMPs, particularly antibiotics, has been linked to drug resistance in animals, particularly antibiotics. Antimicrobial gene products produced in animals due to the prolonged use of VMPs can passed on to humans when they consume animal products. This paper reviews information on the use of VMPs in the Philippines, including the regulations, their impact, challenges, and potential recommendations. The Philippines has existing legislation regulating VMP use. Several agencies were tasked to regulate the use of VMPs, such as the Department of Agriculture, the Department of Health, and the Philippine National Action Plan. Unfortunately, there is a challenge to implementing these regulations, which affects consumers. The unregulated use of VMPs influences the transmission of antibiotic residues from animals to crops to humans. This challenge should be addressed, with more focus on stricter regulation.

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.

Prevalence and multidrug resistance in Salmonella enterica Typhimurium: an overview in South East Asia

Acute/chronic gastroenteritis is caused by a few serovars of Salmonella enterica. Among different serovars, S. enterica Typhimurium is a potent pathogen that contributes significantly to self-limiting diarrhea related mortality worldwide. With no successful vaccine in hand against this pathogen, antibiotics are used as for gold standard for treatment against Salmonella induced gastroenteritis. Indispensably, rise in multi drug resistance against Salmonella Typhimurium poses challenge to treatment options. South East Asia, with 11 different countries, stands 3rd as super region for global burden of Salmonella induced gastroenteritis. In this review, we made an attempt to discuss on prevalence and multidrug resistance in Salmonella Typhimurium in 11 countries of South East Asia-the issue that has not been seriously addressed so far. By thorough analysis of reported data, we found varying frequencies for prevalence of Salmonella Typhimurium as well as subtle evidences on resistance of this pathogen to multiple antibiotics in different countries. Vietnam ranked top in terms of reports for prevalence and antimicrobial resistance. However, in countries such as Brunei and Timor Leste, no study has been performed so far to track the frequency of incidence and drug resistance of this pathogen. Our review, the first of its kind, emphasizes that, although the pathogen was not found as dominant serovar in South East Asia in last 20 years unlike sub-Saharan Africa, it may be still considered as a major threat in this region due to available evidences for infection in humans as well as contamination in several animal and food sources. More importantly, the importance as a public threat in this subregion of Asia is also due to resistance of this pathogen to multiple antibiotics. South East Asian countries showing incidence and multi drug resistance of Salmonella enterica Typhimurium in human and non-human sources (1969-2020). -Drug resistant S. enterica Typhimurium.

Antimicrobials Used in Backyard and Commercial Poultry and Swine Farms in the Philippines: A Qualitative Pilot Study

Chicken and pork are the most frequently consumed meat products in the Philippines. Swine and poultry are reared in either commercial farms (CMf) or backyard farms (BYf); the latter production system is relatively common and essential to food security in low- and middle-income countries (LMICs) such as the Philippines. Similar to resource-limited LMICs, antimicrobial use (AMU) surveillance has not yet been established; thus, AMU in food animals is a knowledge gap in understanding the emergence of antimicrobial resistance (AMR) in zoonotic foodborne bacteria in the country. This qualitative AMU pilot study aims to describe the antimicrobial active ingredients (AAIs) used and associated AMU practices (e.g., source of AAIs and informed AMU decisions) by poultry and swine CMf and BYf in the Philippines. Ninety-three farms across four regions in the Philippines voluntarily provided AMU information as part of a larger biosecurity and good practices study. The percentage of farms using AAI over the total number of farms was the metric used to describe AMU. In total, there were 30 AAIs used (CMf: n =27 and BYf: n = 13); per farm, the number of AAIs used ranged from 1 to 7. The spectrum of AAIs was more diverse in swine (n = 24) compared to poultry (n = 18). Enrofloxacin was the most frequently reported AAI in poultry (33%) and swine (36%) farms. Respiratory diseases were the most frequently reported reason for AMU in both species. Between production systems, significant differences were observed in the percentage of farms using amoxicillin (27% CMf vs. 3% BYf), colistin (17% CMf vs. 3% BYf), and oxytetracycline (12% CMf vs. 39% BYf). In terms of AMU practices, of important concern was the over-the-counter access of AAIs at retail outlets and the limited veterinary oversight in BYf. Our data indicated that antimicrobials critically important for human medicine are frequently used in poultry and swine farms in the Philippines. This study can inform the development of guidelines for curbing AMR through prudent AMU and serves as a reference point for AMU surveillance capacity development in the Philippines.

Antimicrobial Resistance in Nontyphoidal Salmonella Isolates from Human and Swine Sources in Brazil: A Systematic Review of the Past Three Decades

Salmonella is the leading cause of foodborne illnesses worldwide. The widespread use of antimicrobials as prophylactic, therapeutic, and growth promoters in both livestock and human medicine has resulted in selective pressure regarding antimicrobial-resistant (AMR) bacteria. This systematic review summarizes phenotypic antimicrobial resistance profiles in Salmonella isolates from human and swine sources between 1990 and 2018 in Brazil. The 20 studies that matched the eligibility criteria-isolates from pigs and humans from Brazil, between 1990 and 2016, containing information on the number of Salmonella isolates, and applying the disk diffusion susceptibility method-were included. During the assessed period, Salmonella strains isolated from swine sources displayed the highest resistance rates for tetracycline (20.3%) and sulfonamides (17.4%). In contrast, human isolates displayed the highest resistance rates against ampicillin (19.8%) and tetracycline (17%). Salmonella Typhimurium was the most frequent AMR isolate from both swine and human sources, corresponding to 67% of all isolates. From 2001 to 2005, tetracycline and ampicillin were the top antimicrobial resistance compounds, and the most frequently detected in swine and human sources, respectively. A total of 63 and 58 multiple drug resistance profiles were identified in swine and human isolates, respectively. Antimicrobial resistance has decreased throughout the 1990-2016 period, except for gentamicin and nalidixic acid in swine and human isolates, respectively. The results indicate that Salmonella isolated from human and swine display resistance against clinically important antimicrobials, indicating that swine are possibly one of the main vectors for spreading human salmonellosis in Brazil.

Worldwide Epidemiology of Salmonella Serovars in Animal-Based Foods: a Meta-analysis

Salmonella spp. are among the most important foodborne pathogens and the third leading cause of human death among diarrheal diseases worldwide. Animals are the primary source of this pathogen, and animal-based foods are the main transmission route to humans. Thus, understanding the global epidemiology of Salmonella serovars is key to controlling and monitoring this bacterium. In this context, this study aimed to evaluate the prevalence and diversity of Salmonella enterica serovars in animal-based foods (beef, pork, poultry, and seafood) throughout the five continents (Africa, the Americas [North and Latin America], Asia, Europe, and Oceania). The meta-analysis consisted of a chemometric assessment (hierarchical cluster analysis and principal component analysis) to identify the main epidemiological findings, including the prevalence and diversity of the Salmonella serovars in each matrix. Regarding the serovar distribution, S Typhimurium presented a cosmopolitan distribution, reported in all four assessed matrices and continents; poultry continues to play a central role in the dissemination of the Enteritidis serovar to humans, and Anatum and Weltevreden were the most frequently found in beef and seafood, respectively. Additionally, we recommended careful monitoring of certain serovars, such as Derby, Agona, Infantis, and Kentucky. Finally, given the scientific data regarding the most frequently reported serovars and which matrices constitute the main vehicles for the transmission of this pathogen, control programs may be improved, and specific interventions may be implemented in an attempt to reduce the risk of this pathogen reaching humans.IMPORTANCE Salmonellosis is caused by Salmonella spp. and is the third leading cause of death among food-transmitted diseases. This pathogen is commonly disseminated in domestic and wild animals, and the infection's symptoms are characterized by acute fever, nausea, abdominal pain, and diarrhea. The animals are the primary source of salmonellae, and animal-based foods are the main transmission route to humans. Therefore, data collected from these sources could contribute to future global interventions for effective control and surveillance of Salmonella along the food chain. In light of this, the importance of our research is in identifying the prevalence of Salmonella serovars in four animal-based food matrices (pork, poultry, beef, and seafood) and to evaluate the importance that each matrix has as the primary source of this pathogen to humans.