Characterization of Salmonella spp. from wastewater used for food production in Morogoro, Tanzania

The African Wastewater Resistome: Identifying Knowledge Gaps to Inform Future Research Directions

Antimicrobial resistance (AMR) is a growing global public health threat. Furthermore, wastewater is increasingly recognized as a significant environmental reservoir for AMR. Wastewater is a complex mixture of organic and inorganic compounds, including antibiotics and other antimicrobial agents, discharged from hospitals, pharmaceutical industries, and households. Therefore, wastewater treatment plants (WWTPs) are critical components of urban infrastructure that play a vital role in protecting public health and the environment. However, they can also be a source of AMR. WWTPs serve as a point of convergence for antibiotics and resistant bacteria from various sources, creating an environment that favours the selection and spread of AMR. The effluent from WWTPs can also contaminate surface freshwater and groundwater resources, which can subsequently spread resistant bacteria to the wider environment. In Africa, the prevalence of AMR in wastewater is of particular concern due to the inadequate sanitation and wastewater treatment facilities, coupled with the overuse and misuse of antibiotics in healthcare and agriculture. Therefore, the present review evaluated studies that reported on wastewater in Africa between 2012 and 2022 to identify knowledge gaps and propose future perspectives, informing the use of wastewater-based epidemiology as a proxy for determining the resistome circulating within the continent. The study found that although wastewater resistome studies have increased over time in Africa, this is not the case in every country, with most studies conducted in South Africa. Furthermore, the study identified, among others, methodology and reporting gaps, driven by a lack of skills. Finally, the review suggests solutions including standardisation of protocols in wastewater resistome works and an urgent need to build genomic skills within the continent to handle the big data generated from these studies.

Consumption Trends of Antibiotic for Veterinary Use in Tanzania: A Longitudinal Retrospective Survey From 2010-2017

Background

With increased livestock keeping, multiple prevailing infections, antimicrobial agents’ use and pattern in Tanzania, the development of antimicrobial resistance (AMR) becomes inevitable. Antibiotic-resistant pathogens have increasingly become a major challenge in human and animal medicine. Although inappropriate use of antibiotics in humans is the principal cause of resistance, antibiotic-resistant bacteria originating from animals contribute to the emergence and spread of these bacteria. Antibiotics help control a multitude of bacterial infections that are major causes of diseases in both animals and humans. Rational use in animals is crucial to control any development and transfer of AMR to humans. This study aimed to create quantitative evidence of animal antimicrobial usage patterns in Tanzania to serve as a baseline for surveillance of antimicrobial use and antimicrobial resistance control.

Methodology

This descriptive longitudinal retrospective study was conducted to explore the trend of veterinary-antibiotics consumed in the eight years, from 1st January 2010 to 31st December 2017 in Tanzania mainland. The data source was records of all antibiotics imported for veterinary use into Tanzania’s mainland according to the Tanzania Medicines and Medical Devices Authority (TMDA) records. The analysis employed the World Health Organization (WHO) Collaborating Centre for Drug Statistics Methodology using Anatomical Therapeutic and Chemical (ATC) classification. Regression and time series analysis was used to establish trends in antibiotics consumption.

Results

A total of 12,147,491 kg of antibiotics were consumed in Tanzania from 2010 to 2017. Tetracycline, sulfonamides and trimethoprim, quinolones, aminoglycosides, beta-lactams and antibacterial combinations were the most commonly used antibacterial agents in Tanzania. Tetracycline class topped the list with about 8,090,798 kg (66.6%) out of 12,147,491 kg total quantity of antimicrobials consumed. Non-significant, linear curve estimations and time series analysis indicate a decline in the quantities of veterinary antibiotics used in the eight years from 2010 to 2017.

Conclusions

This study suggests that tetracycline is the most used antibiotic class for veterinary medicine in Tanzania. The trend of antimicrobial use is generally decreasing compared to other countries in Africa. Even though some antibiotics have the lowest consumption rate, they are also prone to AMR, prompting follow-up by the relevant regulatory authorities.

Salmonella in the processing line of farmed Tambatinga (Colossoma macropomum x Piaractus brachypomus) in Mato Grosso, Brazil: serotypes of occurrence and antimicrobial profile

The objective of this study was to evaluate the dispersion dynamics and antimicrobial resistance profiles of Salmonella in the processing of Tambatinga (Colossoma macropomum x Piaractus brachypomus). Thirty fish were monitored during four processing stages (reception, first wash, evisceration, and prepackage area) in a fish slaughterhouse. One hundred and twenty fish surface samples were collected and tested through bacteriological analysis, PCR, serotyping, and antimicrobial resistance profile (disk-diffusion). Of these samples, 7.5% (9/120) were positive for Salmonella, with 0.83% being observed in the pre-packaging phase, indicating a low occurrence at this stage. All the analyzed stages were positive for Salmonella, with the prevalent serovars being Ndolo, Mbandaka, Typhimurium, Rough, and O:16. All strains were sensitive to various antimicrobials. Improvements in microbiological control during all processing stages should be implemented to ensure a Salmonella-free product.

Prevalence, Distribution, and Diversity of Salmonella Strains Isolated From a Subtropical Lake

This study investigated the prevalence, serovar distribution, antimicrobial resistance, and pulsed field gel electrophoresis (PFGE) typing of Salmonella enterica isolated from Lake Zapotlán, Jalisco, Mexico. Additionally, the association of the presence of Salmonella with physicochemical and environmental parameters was analyzed using Pearson correlation analysis and principal component analysis (PCA). Salmonella spp. were identified in 19 of 63 (30.15%) samples. The prevalence of Salmonella was positively correlated with air temperature, electrical conductivity, pH, and dissolved oxygen and negatively correlated with relative humidity, water temperature, turbidity, and precipitation. The predominant serotype identified was Agona (68.48%), followed by Weltevreden (5.26%), Typhimurium (5.26%), and serogroup B (21.05%). Overall, the highest detected antimicrobial resistance was toward colistin (73.68%), followed by sulfamethoxazole (63.15%), tetracycline (57.89%), nalidixic acid (52.63%), and trimethoprim (52.63%). All Salmonella strains were genetically diverse, with a total of 11 XbaI and four BlnI profiles on PFGE. The use of these two enzymes allowed differentiate strains of Salmonella of the same serotype. The results obtained in this study contribute to a better understanding of the Salmonella spp. ecology in an endorheic subtropical lake and provide information for decision makers to propose and implement effective strategies to control point and non-point sources of pathogen contamination.

Detection of Enteric Viruses and Bacterial Indicators in a Sewage Treatment Center and Shallow Water Bay

The incidence of enteric viruses in treated wastewater and their potential release into the environment or use for agriculture are very critical matters in public health. In our study, PCR (polymerase chain reaction) analysis of enteric viruses was performed on 59 samples of influents and effluents collected from Tubli wastewater treatment plant (Water Pollution Control Center (WPCC)) and Tubli Bay, where the effluents were discharged, in Kingdom of Bahrain during two sampling periods. Four clinically essential waterborne enteric viruses were examined: enterovirus (EV), hepatitis A virus (HAV), astroviruses (AV), and rotaviruses (RV) and compared to standard bacterial and bacteriophages indicators of fecal pollution. Detection rates of EV, AV, HAV, and RV in the influent samples were 100%, 75%, 12.5%, and 12.5%, respectively, while 50% of the effluent samples from Tubli WPCC contained only EV RNA. None of the tested enteric viruses could be detected in any of the samples collected directly from Tubli Bay. Effluent samples from Tubli plant did not show significant seasonal differences. Since detection of enteric viruses genome does not necessarily indicate infectivity, the infectivity of these viruses was evaluated through isolation and growth of indictor bacteria and bacteriophages. High concentration of fecal bacteriological indicators was detected in all effluents samples (100%): 3.20 × 10³ cfu/mL for E. coli, 1.32 × 10³ cfu/mL for Salmonella spp., and 1.92 × 10³ cfu/mL for Shigella spp. E. coli and Salmonella specific bacteriophages were also detected in the effluent samples in high titers. The combined results of PCR and bacterial enumeration point to a probable public health risk via the use of these wastewaters in agriculture or their discharge into the sea. Continuous surveillance of viral and bacterial prevalence and their resistance to sewage disinfection procedures could contribute to a better control of risks associated with the recycling of effluent wastewater and its release into the environment.

Characterization and evolution of antibiotic resistance of Salmonella in municipal wastewater treatment plants

The objective of this study was to investigate the evolution of antibiotic resistance phenotypes, antibiotic resistance genes (ARGs) and Class 1 integron of Salmonella in municipal wastewater treatment plants (WWTPs). A total of 221 Salmonella strains were isolated from different stages of three WWTPs. After the susceptibility testing, high frequency of resistance was observed for tetracycline (TET, 47.5% of isolates) and sulfamethoxazole (SMZ, 38.5%), followed by ampicillin (AMP, 25.3%), streptomycin (STP, 17.6%), chloramphenicol (CHL, 15.4%), and gentamicin (GEN, 11.3%). Low prevalence of resistance was detected for norfloxacin (0.45%), ciprofloxacin (0.9%), and cefotaxime (0.9%). The tetA and sul3 genes were most frequently detected among the Salmonella isolates. Statistically significant correlations among AMP, CHL, GEN, and STP resistances were observed. High detection frequencies of Class 1 integron were observed in double antibiotic-resistant and multiple-antibiotic-resistant (MAR) Salmonella, which were 94.3% and 85.7%, respectively. The proliferation of MAR Salmonella and transfer of ARGs occurred in WWTPs. Class 1 integron plays a crucial role in the evolution of MAR Salmonella during WWTPs.

Antimicrobial susceptibility profile of selected Enterobacteriaceae in wastewater samples from health facilities, abattoir, downstream rivers and a WWTP in Addis Ababa, Ethiopia

Background

Evaluation of antimicrobial susceptibility profile of various bacterial pathogens in the health facilities, abattoirs and related environment is important to assess potential risk of dissemination of resistant pathogens to the environment. There is limited information about antimicrobial susceptibility profile of common Enterobacteriaceae in waste water samples from hospitals, abattoirs and the downstream water bodies in Addis Ababa. The present study assessed antimicrobial susceptibility of bacteria belonging to the family Enterobacteriaceae isolated from wastewater samples (WWS) of two hospitals: Tikur Anbessa Specialized Hospital (TASH) and Minilik II hospital, a wastewater treatment plant (WWTP) and an abattoir, and downstream rivers in Addis Ababa.

Results

A total of 54 bacterial isolates belonging to 6 species were identified: E.coli (32%), Salmonella 23%), Klebsiella pneumonia (15%), Enterobacter aerogenes (11%), Citrobacter (7%), Klebsiella oxytoca (6%) and Enterobacter cloacae (6%), respectively. Two strains of Citrobacter spp. isolated from TASH wastewater sample (WWS) were resistant to all 12 antimicrobials tested whereas an E. coli isolate from the same source was resistant to 11 antimicrobials. All isolates were resistant to 2 or more antimicrobials tested. Multi-drug resistance (MDR) to several antimicrobials was recorded, particularly in isolates obtained from hospital WWS and it was more common in Citrobacter and E. coli isolates. Extended spectrum betalactamase (ESBL) production was detected in 27.3% of MDR isolates, all of them obtained from hospital effluents whereas none of the isolates were carbapenemase producers.

Conclusion

The present study revealed that Enterobacteriaceae in wastewater from hospitals, abattoir and downstream water bodies are resistant to commonly used antimicrobials. Hospital effluents contained more of MDR bacteria, posing significant public health threat through dissemination to the downstream water bodies.

Infection, colonization and shedding of Campylobacter and Salmonella in animals and their contribution to human disease: A review

Livestock meat and offal contribute significantly to human nutrition as sources of high-quality protein and micronutrients. Livestock products are increasingly in demand, particularly in low- and middle-income settings where economies are growing and meat is increasingly seen as an affordable and desirable food item. Demand is also driving intensification of livestock keeping and processing. An unintended consequence of intensification is increased exposure to zoonotic agents, and a contemporary emerging problem is infection with Campylobacter and Salmonella spp. from livestock (avian and mammalian), which can lead to disease, malabsorption and undernutrition through acute and chronic diarrhoea. This can occur at the farm, in households or through the food chain. Direct infection occurs when handling livestock and through bacteria shed into the environment, on food preparation surfaces or around the house and surroundings. This manuscript critically reviews Campylobacter and Salmonella infections in animals, examines the factors affecting colonization and faecal shedding of bacteria of these two genera as well as risk factors for human acquisition of the infection from infected animals or environment and analyses priority areas for preventive actions with a focus on resource-poor settings.