Motile Salmonella serotypes causing high mortality in poultry farms in three South-Western States of Nigeria

Dose-response study of a fenugreek-based antibiotic alternative in Bábolna Tetra-SL chicks (1-42 days old) with mixed bacterial infections

Introduction

Combating antimicrobial resistance is one of the most pressing public health challenges of our time. The rapid spread of resistant, zoonotic bacterial strains in livestock farming is increasingly raising concerns about the need to reduce antibiotic use. Because of this, there is an urgent need for safe and effective alternatives in animal husbandry.

Methods

This study aimed to perform an in vivo the dose-response analysis of fenugreek (Trigonella foenum-graecum), as a plant-based antibiotic alternative feed supplement in Bábolna Tetra-SL chicks (1-42 days old) with a 1:1 sex ratio. A total of 270 chicks were randomly assigned to 18 groups (15 birds per group) and subjected to six different treatment groups in three replicates: fenugreek at 1×, 10×, and 100× doses, an antibiotic-treated group (enrofloxacin), a positive control group (infection only), and a negative control group (no infection or treatment). The infection was induced using mixed Salmonella Enteritidis and Escherichia coli, administered via gavage on days 3 and 4 of life. The birds were monitored for clinical symptoms, body weight, feed intake, and Salmonella shedding through cloacal swab samples. Statistical analyses included mixed-effect logistic regression for mortality, mixed-effect linear models for weight gain, two-way ANOVA for feed efficiency, and random effects continuation ratio models for Salmonella isolation.

Results

Significant interactions for Group:Day and Sex:Day in weight gain were identified (p < 0.0001 for both). Additionally, the 1 × dose group showed significantly reduced Salmonella shedding compared to the positive control group on day 33 (p = 0.0031). The low-dose group (1×) demonstrated the most promising results, showing a 63% reduction in Salmonella shedding on day 10 and 31% on day 17. This group exhibited the fewest clinical symptoms, no diarrhea, and the lowest individual and specific feed intake up to day 24.

Discussion

The findings of this study suggest that low-dose fenugreek supplementation could be a viable strategy for reducing Salmonella shedding in poultry, potentially contributing to reduced antibiotic use in poultry farming and thus playing a role in the global effort to combat antimicrobial resistance. Future research will involve large-scale industrial trials and next-generation sequencing to evaluate the additive's impact on gut microbiota composition.

Antimicrobial Resistance and Phylogenetic Relatedness of Salmonella Serovars in Indigenous Poultry and Their Drinking Water Sources in North Central Nigeria

There is scant information on Salmonella in indigenous poultry in Nigeria. We investigated the occurrence and characterized Salmonella serovars in indigenous poultry and their drinking water sources to enhance the monitoring of the infection in poultry and to promote public health. We collected 1208 samples, poultry droppings (n = 1108), and water (n = 100) across 15 markets in North Central Nigeria. Salmonella spp. were isolated following World Organisation for Animal Health guidelines. Salmonella spp., confirmed through invA gene detection by a polymerase chain reaction assay, were 6.8% (75/1108) droppings and 3% (3/100) water. Susceptibility testing against 13 antimicrobials showed 60.3% (47/78) susceptibility to all the antimicrobials tested while 14.1% (11/78) were multidrug resistant. Serotyping and whole-genome sequencing were carried out on 44 of the isolates, and 23 different serovars were identified. Genomes of serovars Luedinghausen, Laredo, Widemarsh, and Lansing are being documented in Africa for the first time. Twenty (20) antimicrobial resistance (AMR) gene markers encoding for resistance to aminoglycosides, tetracyclines, sulphonamides, quinolones, trimethoprim, penicillins and phenicols were found. Phylogenetic cluster analysis showed close relatedness among isolates from different sources. This study shows both low Salmonella prevalence and AMR, but since uncommon serovars are circulating, continuous monitoring is recommended so as to ensure food safety and poultry health.

Gene expression response to Salmonella Typhimurium in the cecal tonsil reveals a potential mechanism of resistance in chickens

Salmonella has been one of the most important factors restricting the development of the poultry industry and also poses great threat to public health. To get insight into molecular alterations that occur during bacterial infection, we sequenced the cecal tonsil transcriptome in 2 chicken breeds (Beijing-You and Cobb) known to have differing resistance to Salmonella. The 28-day-old chickens were orally challenged by 1.83 × 1011 CFU Salmonella Typhimurium, and the cecal tonsil transcriptome was sequenced 3 d postinfection. Analysis identified 201 and 170 differentially expressed genes response to Salmonella in 2 chicken breeds, respectively. They were involved in the Toll-like receptor signaling pathway and activated the production of pro-inflammatory cytokines and chemokines. The protein-protein interaction (PPI) network suggested MMP9 as a crucial protein that may be involved in extracellular matrix breakdown and leukocyte migration in the resistant breed (Beijing-You). Meanwhile, in susceptible chickens (Cobb), ACOD1 was the key gene in the PPI network and might promote the expression of genes related to oxidative stress response and gastrointestinal tract function. These findings provide insight into the differing resistance of these 2 chicken breeds.

Evaluation of the different methods to detect Salmonella in poultry feces samples

Salmonella is one of the most common causes of foodborne outbreaks and infection worldwide. The gold-standard detection method of Salmonella is cultivation. There is a need to investigate rapid and accurate processes with time-consuming cultivation. The study evaluated different approaches to detect Salmonella in poultry feces samples. Poultry farm feces samples from 21 cities in Iran were collected from January 2016 to December 2019. Microbiological cultures, serological assays, and multiplex PCR (m-PCR) were used to detect and characterize Salmonella spp. isolates. Serological assays and m-PCR were used to determine the serogroups A, B, C1, C2, D1, E, H, and FliC. The m-PCR was used to detect seven Salmonella serovars, and a Chi-square test was performed to compare the discriminatory power of the methods. Of 2300 poultry feces samples, 173 (7.5%) and 166 (7.2%) samples were detected as Salmonella spp. by cultivation and m-PCR, respectively. The sensitivity of the molecular method was equal to cultivation at 0.96 (CI = 95%). Assessment of H antigenic subgroups showed the same for both m-PCR and serological tests. Therefore, the matching rate of the two methods for detecting all H antigenic subgroups was 100%. Thus, the relationship between the results obtained from both methods was significant in the contingency table test (P < 0.01). The PCR-based approach confirmed the detection of Salmonella in a shorter period (24-36 h) compared to the conventional microbiological approach (3-8 days).

Antimicrobial resistance and virulence genes in Salmonella enterica serovars isolated from droppings of layer chicken in two farms in Nigeria

AIM

This study aimed to investigate the isolation rate, antibiotic resistance, and virulence genes of Salmonella enterica serovar from two commercial farms in Nigeria.

METHODS AND RESULTS

Salmonella isolation was performed according to the United States Food and Drug Agency (USFDA) method. Serotyping, antimicrobial susceptibility testing, detection of resistance and virulence genes were done using the Kauffman-White Scheme, disc diffusion, minimum inhibitory concentration, and real-time polymerase chain reaction techniques. Salmonella serovars were isolated from only farm A at 22/50 (44.0%) while none were isolated from farm B. Salmonella Typhi, 9 (40.9%); Salmonella Typhimurium, 2 (9.1%), Salmonella Enteritidis, 2 (9.1%), Salmonella Pullorum, 1 (4.5%), Salmonella Kentucky, 4 (18.2%) were identified while 4 (18.2%) were untypable. Sixteen isolates (72.7%) showed multiple drug resistance and 17 different resistance profile types with AMP-CHL-TRM-SXT as the most prevalent pattern. Resistance genes (blaTEM, 12/22 (54.5%) and virulence genes (InvA, sopB, mgtC, and spi4D, 22/22 (100.0%), ssaQ, 16/22 (72.7%), and spvC, 13/22 (59.1%) were found, while blaSHV, blaCTX-M, floR, tetA, tetB, tetG, and LJSGI-1 genes were absent.

CONCLUSION

Pathogenic Salmonella were isolated from the chicken droppings in this study. Most of these strains were resistant to antibiotics and possessed characteristics of virulence.

SIGNIFICANCE AND IMPACT OF THE STUDY

Chicken droppings from this study area contained pathogenic strains of Salmonella and a rare occurrence of Salmonella Typhi. The study revealed that the environment and the food chain could be at risk of contamination of highly virulent and antimicrobial-resistant strains of Salmonella. These could affect the profitability of the poultry industry and food consumption. There is a need for caution in indiscriminate disposal of poultry waste and the use of uncomposted chicken droppings in soil amendment.

Occurrence, Risk Factors, Serotypes, and Antimicrobial Resistance of Salmonella Strains Isolated from Imported Fertile Hatching Eggs, Hatcheries, and Broiler Farms in Trinidad and Tobago

ABSTRACT

This cross-sectional study was conducted to determine the occurrence, risk factors, and characteristics of Salmonella isolates recovered from imported fertile broiler hatching eggs, hatcheries, and broiler farms in Trinidad and Tobago. Standard methods were used to isolate and characterize Salmonella isolates from two broiler hatcheries and 27 broiler farms in the country. The frequency of isolation of Salmonella was 0.0% for imported fertile hatching eggs (0 of 45 pools of 10 eggs each, i.e., 450 eggs), 7.6% for hatcheries (12 of 158 samples), and 2.8% for broiler farms (24 of 866 samples) (P = 0.006). Stillborn chicks at hatcheries had the highest prevalence of Salmonella (7 of 28 samples, 28.0%), whereas on broiler farms the cloacal swabs had the highest prevalence of Salmonella (15 of 675 samples, 2.2%). None of the 15 farm management and production practices investigated were significantly associated (P > 0.05) with the isolation of Salmonella. The predominant Salmonella serotypes were Kentucky (83.3%) and Infantis (62.5%) among hatchery and farm isolates, respectively. The disk diffusion method revealed frequencies of antimicrobial resistance (i.e., resistance to one or more agents) of 44.0% (11 of 25 isolates) and 87.5% (35 of 40 isolates) at hatcheries and broiler farms, respectively (P = 0.0002). Antimicrobial resistance among hatchery isolates was highest (28.0%) to doxycycline and kanamycin and was very high (>65%) among farm isolates to sulfamethoxazole-trimethoprim, gentamicin, ceftriaxone, kanamycin, and doxycycline. Multidrug resistance (MDR; i.e., resistance to antimicrobial agents from three or more classes) was exhibited by 4.0 and 85.7% of Salmonella isolates recovered from several environmental and animal sources at the hatcheries and farms, respectively (P < 0.0001). The high level of antimicrobial resistance and the presence of MDR among Salmonella isolates from broiler farms highlight the therapeutic implications and the potential for MDR strains to enter the food chain.

HIGHLIGHTS

Isolation and antimicrobial resistance of motile Salmonella enterica from the poultry hatchery environment

Salmonella is a globally distributed major food-borne pathogen and poultry is one of the predominant sources of salmonellosis in humans. To investigate the presence of motile Salmonella in the poultry hatchery environment, we collected 97 fluff samples from four selected broiler breeder chicken hatcheries from Chattogram, Bangladesh during July-December 2015. To isolate motile Salmonella enterica, we used conventional bacteriological techniques followed by serological verification using anti-Salmonella Poly A-E serum and species confirmation by conventional PCR assay. Antimicrobial susceptibility testing by Kirby-Bauer disc diffusion method for 10 commonly used antibiotics was performed on all isolates. Isolates displaying phenotypic resistance to ampicillin were tested by PCR for bla_TEM gene, whereas those resistant to tetracycline were tested for the presence of tetA, tetB and tetC genes. A total of 24 samples (24.7%; 95% CI: 16.5-34.5, N = 97) from 3 hatcheries were positive for motile Salmonella. Of them, 21 (87.5%) and 12 (50.0%) were resistant to ampicillin and tetracycline, respectively, 9 (37.5%) to nalidixic acid and sulphamethoxazole/trimethoprim. No resistance was detected to ceftriaxone, cefoxitin, gentamicin, neomycin, ciprofloxacin and colistin. Ten (42%) of 24 isolates from 2 hatcheries were multi-drug resistant (i.e. resistant to ≥ 3 antimicrobial classes). Six of 21 ampicillin resistant isolates contained bla_TEM gene and 10 of 12 tetracycline resistant isolates contained tetA gene. This study highlights the circulation of multi-drug resistant motile Salmonella in the hatchery environment for the first time in Bangladesh. Further epidemiological and molecular studies are therefore needed to identify the serotypes and source of the bacteria in hatcheries.

Prevalence and risk factors of Salmonella in commercial poultry farms in Nigeria

Salmonella is an important human pathogen and poultry products constitute an important source of human infections. This study investigated prevalence; identified serotypes based on whole genome sequence, described spatial distribution of Salmonella serotypes and predicted risk factors that could influence the prevalence of Salmonella infection in commercial poultry farms in Nigeria. A cross sectional approach was employed to collect 558 pooled shoe socks and dust samples from 165 commercial poultry farms in North West Nigeria. On-farm visitation questionnaires were administered to obtain information on farm management practices in order to assess risk factors for Salmonella prevalence. Salmonella was identified by culture, biotyping, serology and polymerase chain reaction (PCR). PCR confirmed isolates were paired-end Illumina- sequenced. Following de novo genome assembly, draft genomes were used to obtain serotypes by SeqSero2 and SISTR pipeline and sequence types by SISTR and Enterobase. Risk factor analysis was performed using the logit model. A farm prevalence of 47.9% (CI95 [40.3-55.5]) for Salmonella was observed, with a sample level prevalence of 15.9% (CI95 [12.9-18.9]). Twenty-three different serotypes were identified, with S. Kentucky and S. Isangi as the most prevalent (32.9% and 11%). Serotypes showed some geographic variation. Salmonella detection was strongly associated with disposal of poultry waste and with presence of other livestock on the farm. Salmonella was commonly detected on commercial poultry farms in North West Nigeria and S. Kentucky was found to be ubiquitous in the farms.

Biomonitoring of Heavy Metal Pollution Using Acanthocephalans Parasite in Ecosystem: An Updated Overview

As a result of the global industrial revolution, contamination of the ecosystem by heavy metals has given rise to one of the most important ecological and organismic problems, particularly human, early developmental stages of fish and animal life. The bioaccumulation of heavy metals in fish tissues can be influenced by several factors, including metal concentration, exposure time, method of metal ingestion and environmental conditions, such as water temperature. Upon recognizing the danger of contamination from heavy metals and the effects on the ecosystem that support life on earth, new ways of monitoring and controlling this pollution, besides the practical ones, had to be found. Diverse living organisms, such as insects, fish, planktons, livestock and bacteria can be used as bioindicators for monitoring the health of the natural ecosystem of the environment. Parasites have attracted intense interest from parasitic ecologists, because of the variety of different ways in which they respond to human activity contamination as prospective indices of environmental quality. Previous studies showed that fish intestinal helminths might consider potential bioindicators for heavy metal contamination in aquatic creatures. In particular, cestodes and acanthocephalans have an increased capacity to accumulate heavy metals, where, for example, metal concentrations in acanthocephalans were several thousand times higher than in host tissues. On the other hand, parasitic infestation in fish could induce significant damage to the physiologic and biochemical processes inside the fish body. It may encourage serious impairment to the physiologic and general health status of fish. Thus, this review aimed to highlight the role of heavy metal accumulation, fish histopathological signs and parasitic infestation in monitoring the ecosystem pollutions and their relationship with each other.

Quantitative distribution and interaction of Salmonella Zega with host cells in visceral organs of chickens infected orally, intraperitoneally and per cloaca

Immunohistochemical study of the visceral organs of chickens experimentally infected with Salmonella Zega by three routes was carried out to compare the quantitative distribution and interaction of the organism with host cells. 100 birds comprising of 2 week-old chickens were divided into 4 groups of 25 each. Group A was inoculated orally, group B intraperitoneally, group C were administered per cloaca and D were not inoculated and served as control. All the infected birds were inoculated with 0.2 ml of 1 × 108 cfu of the bacteria. Two birds from each group were sacrificed every 24 h post infection. Samples of visceral organs were collected for immunohistochemistry. The distribution of Salmonella Zega in every organ was taken as Mean ± SD of the number of foci of immunoreactions and Compared using a 2-way ANOVA. The interaction of Salmonella Zega with host cells was determined by taking the percentage of the days post infection in which immunoreactions were detected in host cells in each route of infection. The distribution of the organism was highest in the lung of intraperitoneally infected chickens (83.95 ± 27.89) and lowest in the heart (5.21 ± 3.65) of chickens that were infected per cloaca. The highest percentage of interaction of Salmonella Zega was recorded in the epithelial (100%) and blood (100%) cells in all the routes of infection. There were variations in the distribution of Salmonella Zega in visceral organs of chickens but the level of interactions with host cells were similar even when infected through different routes.

Comparison of the clinical signs, pathological and immuohistochemical findings in visceral organs of chickens experimentally infected with Salmonella Zega through three routes

Salmonella Zega isolated from natural outbreaks that were characterized by high mortality in poultry farms in three Southwestern States of Nigeria was used to inoculate two week-old chicks through different routes in order to determine and compare the clinical signs, pathological and immunohistochemical changes in each route of infection. The birds were divided into 4 groups of 25 each as groups A (orally inoculated), B (intraperitoneally inoculated), C (inoculated per cloaca) and D (uninoculated control). All the birds were inoculated with 0.2 ml of 1 × 10⁸ cfu of the bacteria. Clinical signs were observed and recorded according to the route of infection, and with the days post-infection from day 0 till day 10 post-infection. Two birds from each group were sacrificed every 24 h and examined for gross lesions, which were described and scored according to the route of infection and days post-infection. Samples of visceral organs were collected for bacteriology, histopathology and immunohistochemistry. Clinical signs in chicks infected orally and intraperitoneally were weakness, anoraexia lethargy, somnolescence, yellowish diarrhoea observed from 4 days till day 10 post infections. Mild sign of weakness was observed in chickes infected per cloaca, from day 3 to 7. The gross lesions were congestion, oedema and enlargement and necrosis in visceral organs from day 4 to 10 post infection in orally and intraperitoneally infected chicks, but mild vascular changes were observed in chicks infected per cloaca, except in the caecum were lesions of necrosis and infiltration of inflammatory cells were moderate to severe. Microscopic lesions were necrosis of host cells and infiltration by lymphocytes, heterophils and macrophages in multiple organs observed from day 4 to 10 post infection in orally and intraperitoneally infected chicks. Immunoreactions were observed in all the visceral organs examined. Clinical signs, pathological and immunohistochemical findings were mild in chicks infected per cloaca, except caecal lesions. Salmonella Zega isolated from an outbreak in poultry farms in Abeokuta, Nigeria was highly pathogenic in chicken and produced similar findings in oral and intraperitoneal infections; while per cloacal infection showed a localized infection of the caecum.