Incidence and Antimicrobial Susceptibility to Clostridium perfringens in Premarket Broilers in Taiwan

High Prevalence of Multidrug-Resistant, Biofilm-Forming Virulent Clostridium perfringens in Broiler Chicken Retail Points in Northeast India

In light of the significant public health and food safety implications associated with Clostridium perfringens, this study aimed to isolate and characterize C. perfringens in samples obtained from broiler chicken retail points in Meghalaya, northeastern India. A total of 280 samples comprising meat, intestinal contents, water, and hand swabs were processed to detect contamination by C. perfringens. The isolates were subjected to toxinotyping, antimicrobial susceptibility testing, and biofilm-forming ability test. The overall occurrence of C. perfringens was 22.5% (17.74-27.85, 95% CI) with the highest recovery from intestine samples (31%; 22.13-41.03, 95% CI), followed by meat (23%, 15.17-32.49, 95% CI) and water samples (18%, 8.58-31.44, 95% CI). Type A was the predominant toxinotype (71.43%, 58.65-82.11, 95% CI), followed by Type A with beta2 toxin (17.46%, 9.05-29.10, 95% CI), Type C (7.94%, 2.63-17.56, 95% CI), and Type C with beta2 toxin (3.17%, 0.39-11.0, 95% CI). Nearly all (95.24%) isolates were multidrug resistant and 68.25% were biofilm formers. The predominance of multidrug-resistant and virulent Type A and Type C C. perfringens in retail broiler meat and intestines in the tribal-dominated northeastern region of India is of great concern from food safety and public health perspectives.

Clostridium perfringens-Opportunistic Foodborne Pathogen, Its Diversity and Epidemiological Significance

The C. perfringens species is associated with various environments, such as soils, sewage, and food. However, it is also a component of the gastrointestinal (GI) microflora (i.e., microbiota) of sick and healthy humans and animals. C. perfringens is linked with different systemic and enteric diseases in livestock and humans, such as gas gangrene, food poisoning, non-foodborne diarrhoea, and enterocolitis. The strains of this opportunistic pathogen are known to secrete over 20 identified toxins that are considered its principal virulence factors. C. perfringens belongs to the anaerobic bacteria community but can also survive in the presence of oxygen. The short time between generations, the multi-production capability of toxins and heat-resistant spores, the location of many virulence genes on mobile genetic elements, and the inhabitance of this opportunistic pathogen in different ecological niches make C. perfringens a very important microorganism for public health protection. The epidemiological evidence for the association of these strains with C. perfringens-meditated food poisoning and some cases of non-foodborne diseases is very clear and well-documented. However, the genetic diversity and physiology of C. perfringens should still be studied in order to confirm the importance of suspected novel virulence traits. A very significant problem is the growing antibiotic resistance of C. perfringens strains. The aim of this review is to show the current basic information about the toxins, epidemiology, and genetic and molecular diversity of this opportunistic pathogen.

Animal Model Studies, Antibiotic Resistance and Toxin Gene Profile of NE Reproducing Clostridium perfringens Type A and Type G Strains Isolated from Commercial Poultry Farms in China

Poultry necrotic enteritis (NE) is a complex and multifactorial disease caused by Clostridium perfringens types. Earlier, the disease was prevented and/or controlled through the addition of in-feed antibiotics and antimicrobial growth promoters (AGPs). The ban on the use of these agents as feed additives has been a major reason for re-emergence of this disease leading to huge economic losses to the world poultry industry. Understanding the pathogenesis of NE by developing an effective experimental model remains challenging and lacks consistency owing to the involvement of several critical factors involved in causing lesions of disease in the field. In this study, locally characterized C. perfringens types, i.e., ACP (toxinotype A), and GCP (toxinotype G), obtained from NE outbreaks on commercial farms in China (2020–2022), were used to experimentally induce NE in Specific-Pathogen-Free (SPF) chicks. The lesion scores observed on day 20 were 1.9 ± 1.10 (GCP strain) and 1.5 ± 1.08 (ACP strain), and both had significant difference as compared to the control group. The inclusion of fishmeal in addition to oral clostridial dose, i.e., fishmeal (day 7 onward) + Clostridia (7.5 × 108 cfu/mL consecutively for 04 days) induced a lesion score of 2.0 ± 1.15 in respective groups. Use of coccidia (Eimeria necatrix) on day 9 followed by clostridia challenge enhanced the lesion scores to 2.5 ± 1.08 and 2.2 ± 1.23 for type G and type A strains, respectively. When both predisposing factors (coccidia + fish meal) were given together, i.e., fishmeal (day 7 onward) and coccidia (day 9) along with clostridia, the lesion scores were 3.2 ± 1.22 (GCP + coccidia + fish meal) and 3.0 ± 1.15 (ACP + coccidia + fish meal). These results were significantly different from group 1 (ACP) and 2 (GCP), in which only C. perfringens was used to induce NE. The clinical signs as well as histopathological lesions in experimentally induced groups were found similar as reported in the literature. The two type G strains identified in this study were also used for susceptibility testing against various drugs. Both strains were found to be resistant to amikacin, doxycycline, metronidazole, neomycin, nystatin, polymyxin B, streptomycin, and tetracycline. Variable susceptibility was seen against ceftriaxone, florfenicol, gentamicin, and kanamycin drugs. Amoxicillin, ampicillin, cefotaxime, ciprofloxacin, enrofloxacin, ofloxacin, and penicillin were effective drugs based upon their low level of resistance and therefore they might be preferred over other antimicrobial agents for proper treatment/prophylaxis of NE infections. Further studies are needed to study the pathogenesis of NE in detail in experimentally induced models along with continuous monitoring of the resistance pattern of C. perfringens strains in the field.

Investigation of Clostridium perfringens in small-scale commercial broiler flocks in Mymensingh district of Bangladesh

Background and Aim

Necrotic enteritis (NE) is one of the most prevalent diseases in broiler poultry caused by Clostridium perfringens connected with significant economic losses. A cross-sectional survey was conducted in Mymensingh district of Bangladesh to assess the prevalence of C. perfringens through toxinotyping molecular assay and confirm the risk factors for NE, including antimicrobial-resistant (AMR) status of the isolates.

Materials and Methods

We included 40 small-scale commercial broiler farms randomly selected from two subdistricts of Mymensingh district of Bangladesh. As an individual sample, 240 cloacal swabs, and as a pooled sample, 40 drinking water, 40 workers' hand washing, 40 litter swab, and 40 feed samples were collected and evaluated by culture, biochemical, and molecular assays. A pretested semi-structured interview questionnaire was employed to capture flock-level data on risk factors from the farm owners. The flock-level data on risk factors were assessed through univariable and multivariable logistic regression analyses with p<0.05 was considered statistically significant.

Results

Overall flock-level prevalence of C. perfringens was estimated to be 10.3% (95% confidence interval [CI] 7.5-13.6%). Litter swab (pooled) was found to be highly contaminated with C. perfringens (25.0%, 95% CI: 12.7-41.2%) followed by the cloacal swab (10.4%, 95% CI: 6.9-15.0%) and feed sample (5.0%, 95% CI: 0.6-16.9%). History of coccidia infection (Adjusted odds ratio =33.01, 95% CI: 2.14-507.59, p=0.01) was significantly associated with flock-level C. perfringens infection status. In this study, 78.1% isolates were found as multidrug-resistant as they demonstrated resistance to 3-5 antimicrobial agents.

Conclusion

Evidence-based control options need to be taken through the uses of prebiotics and probiotics, biosecurity, and hygienic measurement, including control of coccidia infection, is needed to lessen the NE infection and AMR related to this pathogen in small-scale commercial broiler poultry.

Isolation, toxinotyping and antimicrobial susceptibility testing of Clostridium perfringens isolated from Pakistan poultry

BACKGROUND AND OBJECTIVES

Clostridium perfringens is a causative agent of enteric infections in animals including poultry by producing twenty different types of toxins. A single strain produces only a subset of these toxins, which form the basis of its classification into seven toxinotypes (A-G). C. perfringens toxinotype A is a widespread cause of necrotic enteritis (NE) in poultry. The current study was conducted to determine the prevalence of different toxins and antimicrobial susceptibility of C. perfringens isolated from Pakistan NE affected poultry.

METHODS

A total of 134 intestinal samples of the diseased birds were collected postmortem and processed for isolation of C. perfringens using tryptose sulphite cycloserine (TSC) agar supplemented with d-cycloserine. Isolates were confirmed by Gram's staining, biochemical and molecular analyses. Toxinotyping was performed by multiplex PCR. Antimicrobial susceptibility profile of isolates was performed by Kirby Bauer disc diffusion method.

RESULTS

A total of 34 strains of C. perfringens were isolated from 134 samples with prevalence rate of 25.37%. All the isolated strains were toxinotype A, as they were positive for alpha toxin (CPA) and negative for other tested toxins such as beta (CPB), epsilon (ETX), iota (ITX), enterotoxin (CPE), toxin perfringens large (TpeL) and necrotic B-like toxin (NetB). Interestingly, all the isolated strains of C. perfringens were multidrug resistant. The highest resistance was observed against Neomycin, Trimethoprim, Tetracycline and Lincomycin which are routinely used at Pakistan poultry production.

CONCLUSION

C. perfringens toxinotype A is prevalent in Pakistan poultry. Incidence of C. perfringens with prevalence rate of 25.37% can pose serious threat to Pakistan's poultry industry given that all the isolated strains were multidrug resistant. Our findings highlight the need for new antibiotics and antibiotic alternatives to overcome multidrug resistance.

Prevalence and characterization of Clostridium perfringens isolated from different chicken farms in China

Clostridium perfringens (C. perfringens) is a common pathogenic microorganism present in nature, which can cause animal and human diseases, such as necrotizing enteritis (NE) in poultry. Little is known about the current prevalence status of C. perfringens from poultry farms of different types and regions in China. From December 2018 to August 2019, we investigated the prevalence, genotype distribution and drug resistance of C. perfringens from Guangdong, Pingyin, Tai'an and Weifang. A total of 622 samples were collected and processed for C. perfringens isolation, among which 239 (38.42%) samples were determined to be positive for C. perfringens. A total of 312 isolates of C. perfringens were recovered (1-5 strains were isolated for each positive sample), and 98.72% of the isolates were identified as type A, while the others were type F. Antimicrobial susceptibility testing revealed that 47.71% of the isolates were resistant to at least five classes of commonly used antibiotics. Multilocus sequence typing (MLST) showed that 74 representative isolates were divided into 63 sequence types (STs), and the Simpson's diversity index (Ds) of the STs for the five farms was 0.9799. 37.84% of the isolates were classified into seven clonal complexes (CC1-CC7), and the isolates from the same farm were more concentrated in the minimum spanning tree. In addition, some cloaca isolates and feed isolates were distributed in the same ST or CC; this result indicates that the C. perfringens in chicken can come from the environment (feed etc.).

Research Note: Prevalence and molecular characteristics of Clostridium perfringens in "no antibiotics ever" broiler farms

Clostridium perfringens (C. perfringens) is the etiological agent of necrotic enteritis and gangrenous dermatitis; 2 diseases that cause significant economic and welfare concerns to the broiler industry. Previously, Clostridium-related diseases were managed with the use of antimicrobial growth promoters fed to broilers that improved gut health and performance. The recent shift to no antibiotics ever (NAE) production has increased the incidence of Clostridium-related diseases. The objective of this study was to identify C. perfringens prevalence and toxinotypes in NAE farms. Samples of litter, feces, and cloacal swabs were collected from 4 NAE broiler farms in the summer of 2019, on d 28 and d 56 of one flock cycle. A total of 734 presumptive isolates were obtained from 192 samples collected in the study. Irrespective of the age of flock and sample type, all 192 samples contained at least one colony presumptively identified as C. perfringens on Perfringens agar plate with morphology as a single, round colony with opaque ring and black center. All isolates were further screened using PCR for confirmation, toxinotyping, and identification of virulence-associated genes. Only 9 isolates among the 734 presumptive isolates were confirmed as C. perfringens and all confirmed isolates were toxinotype A with variation in presence of netB, cpb2, and tpeL. More extensive studies are required to assess the prevalence and virulence of C. perfringens in NAE farms.

Prevalence and multilocus sequence typing of Clostridium perfringens isolated from retail chicken products and diseased chickens in Tai'an region, China

Background

Clostridium perfringens is an important zoonotic microorganism, which can cause diseases in animals and humans under suitable conditions. Contamination of C. perfringens in chicken products has been reported worldwide, but the genetic diversity and relationship of isolates were seldom analyzed.

Objectives

The current study was undertaken to investigate the prevalence of C. perfringens from retail chicken products and sick chickens with suspected necrotic enteritis (NE) in Tai'an area, China.

Methods

In total, 295 samples were collected from Tai'an large poultry retail market and veterinary hospital in 2018, then the isolates were tested for toxin genes, drug resistance and multilocus sequence typing (MLST).

Results

Overall, 138 (46.78%) samples were determined to be positive for C. perfringens, and 99.37% of the isolates were identified as C. perfringens type A, with the remaining isolates being type F; 18.99% of the isolates were positive for cpb2 gene. Antimicrobial susceptibility testing revealed that 52.27% of the isolates from poultry retail market and diseased chickens showed multiple antibiotic resistance. MLST results showed that 50 analyzed isolates can be divided into 39 sequences types (STs), clustered in three clonal complexes (CCs) and 23 singletons. Although most of the isolates belong to type A, considerable genetic diversity can be observed, with the Simpson's diversity index up to 0.9181. MLST results and phylogenetic analysis showed that a portion of the isolates from humans and chickens were assigned to the same clusters in the phylogenetic tree or found to be in the same CCs, indicating the chicken isolates and the human isolates are related in certain stratification.

Conclusions

This study showed that the contamination rate of C. perfringens in the local retail chicken products was relatively high. Most of the isolates exhibit broad‐spectrum antimicrobial resistance. The high antibiotic resistance of C. perfringens isolates and the relationship between isolates from human and chicken indicated potential public health risks.

Probiotics: an Antibiotic Replacement Strategy for Healthy Broilers and Productive Rearing

Pathogens develop resistance to antibiotics at a rate much faster than the discovery of new antimicrobial compounds. Reports of multidrug-resistant bacteria isolated from broilers, and the possibility that these strains may spread diseases amongst humans, prompted many European countries to ban the inclusion of antibiotics in feed. Probiotics added to broiler feed controlled a number of bacterial infections. A combination of Enterococcus faecium, Pediococcus acidilactici, Bacillus animalis, Lactobacillus salivarius and Lactobacillus reuteri decreased the colonisation of Campylobacter jejuni and Salmonella Enteritidis in the gastro-intestinal tract (GIT) of broilers, whereas Bacillus subtilis improved feed conversion, intestinal morphology, stimulated the immune system and inhibited the colonisation of Campylobacter jejuni, Escherichia coli and Salmonella Minnesota. Lactobacillus salivarius and Pediococcus parvulus improved weight gain, bone characteristics, intestinal morphology and immune response, and decreased the colonisation of S. Enteritidis. Lactobacillus crispatus, L. salivarius, Lactobacillus gallinarum, Lactobacillus johnsonii, Enterococcus faecalis and Bacillus amyloliquefaciens decreased the Salmonella count and led to an increase in lysozyme and T lymphocytes. Probiotics may also improve feed digestion through production of phytases, lipases, amylases and proteases or stimulate the GIT to secrete digestive enzymes. Some strains increase the nutritional value of feed by production of vitamins, exopolysaccharides and antioxidants. Bacteriocins, if produced, regulate pathogen numbers in the GIT and keep pro-inflammatory and anti-inflammatory reactions in balance.

Tracing Clostridium perfringens strains along the chicken production chain from farm to slaughter by multilocus sequence typing

The current study is undertaken to characterize the prevalence, genotypes distribution, antibiotic resistance and genetic diversity of Clostridium perfringens (C. perfringens) collected from different stages of a chicken production chain. In total, 579 samples from a broiler farm and 378 samples from the slaughterhouse were collected from a large-scale rearing and slaughter one-stop enterprise in Weifang, China, between June and July 2019, of which 30.40% of the samples from farm and 54.50% of samples from slaughterhouse were determined to be positive for C. perfringens, respectively. The contamination of chicken products was relatively serious, with the total positive rate of carcasses at 59.73%; the positive rate of carcass samples was the highest in the evisceration process, which might be the critical point of C. perfringens contamination. A total of 476 isolates of C. perfringens were recovered; and 99.58% of recovered isolates were identified as type A, with the remaining isolates being type G. Antimicrobial susceptibility testing revealed that 97.15% of the isolates showed multiple antibiotic resistance and 67.89% of them were resistant to at least five classes of commonly used antibiotics. Multilocus sequence typing results of 91 representative isolates showed that the isolates can be divided into 74 sequences types (STs); 40.66% of the isolates can be included into seven clonal complexes (CCs). Although most of the isolates were classified as type A, considerable genetic diversity was observed, with the Simpson's diversity index of ST up to 0.9902. Some isolates from farm stage and slaughter stage were distributed in the same ST or CC, indicating that chicken products may be contaminated by the same ST or CC of C. perfringens originated from the farm stage. The high contamination rates of chicken products and the widespread multiple antibiotic resistance of isolates indicated potential public health risks, control measures at rearing and slaughtering stage should be considered to reduce this risk.

Alginate Nanoparticles Enhance Anti-Clostridium perfringens Activity of the Leaderless Two-Peptide Enterocin DD14 and Affect Expression of Some Virulence Factors

Here, we report a novel approach to improve the anti-Clostridium perfringens activity of the leaderless two-peptide enterocin 14 (EntDD14), produced by Enterococcus faecalis 14. This strategy consists of loading EntDD14 onto alginate nanoparticles (Alg NPs), which are made of a safe polymer. The resulting formulation (EntDD14/Alg NPs) was able to reduce up to four times the minimum inhibitory concentration (MIC) of EntDD14 against C. perfringens pathogenic strains isolated from a chicken affected by necrotic enteritis (NE). Interestingly, this formulation remained active under conditions mimicking the human and chicken gastric tract. Assays conducted to establish the impact of this formulation on the intestinal epithelial cell line Caco-2 and the human colorectal adenocarcinoma cell line HT29 revealed the absence of cytotoxicity of both free-EntDD14 and EntDD14 loaded onto the alginate nanoparticles (EntDD14/Alg NPs) against the aforementioned eukaryotic cells, after 24 h of contact. Notably, EntDD14 and EntDD14/Alg NPs, both at a sub-inhibitory concentration, affected the expression of genes coding for clostridial toxins such as toxin α, enteritis B-like toxin, collagen adhesion protein and thiol-activated cytolysin. Further, expression of these genes was significantly down-regulated following the addition of EntDD14/Alg NPs, but not affected upon addition of EntDD14 alone. This study revealed that adsorption of EntDD14 onto Alg NPs leads to a safe and active formulation (EntDD14/Alg NPs) capable of affecting the pathogenicity of C. perfringens. This formulation could therefore be used in the poultry industry as a novel approach to tackle NE.

Bacillus licheniformis-Fermented Products Improve Growth Performance and Intestinal Gut Morphology in Broilers under Clostridium perfringens Challenge

Necrotic enteritis caused by Clostridium perfringens has reemerged as a severe poultry disease worldwide since the ban on the routine use of antibiotics in animal feed. Probiotics are considered alternatives to antibiotic growth promoters. Bacillus species are the most common microorganisms used as probiotics in the feed industry. The current study investigated the growth and surfactin levels of Bacillus licheniformis in solid-state fermentation using different substrates and evaluated the effects of B. licheniformis-fermented products on growth performance and intestinal morphology in broilers exposed to C. perfringens. The highest viable biomass and surfactin concentration of B. licheniformis-fermented products was observed at 2% molasses and 20% soybean meal supplementation during fermentation (P<0.05). B. licheniformis-fermented product-derived surfactin inhibited the growth of C. perfringens in vitro in a dose dependent manner (P<0.05). B. licheniformis-fermented product supplementation (2 g/kg) significantly improved the body weight and average daily gain weight of broilers challenged with C. perfringens (P<0.05). B. licheniformis-fermented products significantly alleviated necrotic lesions and ameliorated intestinal morphology in broilers exposed to C. perfringens (P<0.05). Collectively, these observations demonstrate that B. licheniformis-fermented products improve growth performance and gut morphology in broilers under C. perfringens challenge. B. licheniformis-fermented products may have the potential to be used as alternatives to antibiotic growth promoters for preventive treatments against C. perfringens in broilers.

Antimicrobial Susceptibility and Association with Toxin Determinants in Clostridium perfringens Isolates from Chickens

The aim of the present study was to investigate variation in antimicrobial resistance in Clostridium perfringens (C. perfringens) isolated from chickens after withdrawal of antimicrobial growth promoters (AGPs); and to investigate the correlation between the presence of toxin genes (cpb2, netB, and tpeL) and antimicrobial resistance. Altogether, 162 isolates of C. perfringens were obtained from chickens displaying clinical signs of necrotic enteritis (n = 65) and from healthy chickens (n = 97) in Korea during 2010–2016. Compared to before AGP withdrawal, increased antimicrobial resistance or MIC₅₀/MIC₉₀ value was observed for nine antimicrobials including penicillin, tetracycline, tylosin, erythromycin, florfenicol, enrofloxacin, monensin, salinomycin, and maduramycin. Significantly (p < 0.05) higher resistance to gentamicin, clindamycin, and virginiamycin was found in isolates from chickens with necrotic enteritis compared to those from healthy chickens. tpeL gene was not detected in C. perfringens isolates from healthy chickens. A correlation between toxin gene prevalence and antibiotic resistance was found in the C. perfringens isolates. Because the usage of antimicrobials may contribute to the selection of both resistance and toxin genes, these can potentially make it challenging to control antimicrobial resistance in pathogenic colonies. Therefore, a more complete understanding of the interplay between resistance and virulence genes is required.

Prevalence and multilocus sequence typing of Clostridium perfringens isolated from 4 duck farms in Shandong province, China

Clostridium perfringens is an important zoonotic microorganism. The present study was undertaken to investigate prevalence, serotype distribution, antibiotic resistance, and genetic diversity of C. perfringens isolates from 4 duck farms in Shandong, China. In total, 424 samples of cloacal swabs and environment were collected from 3 commercial meat-type duck farms in Tai'an, Liaocheng, and Weifang and one breeder duck farm in Liaocheng between December 2018 and June 2019, of which, 207 (48.82%) samples were determined to be positive for C. perfringens; a total of 402 isolates of C. perfringens were recovered, all of which were identified as type A; 30.85% of the isolates were positive for cpb2 gene; and cpe gene was found in 0.5% of the isolates. Antimicrobial susceptibility testing revealed that some of the isolates exhibited high antibiotic resistance, and 39.14% of the isolates were resistant to at least 5 classes of commonly used antibiotics. Multilocus sequence typing analysis showed that 85 representative isolates encompassed 54 different sequences types (STs), clustered in 5 clonal complexes (CCs) and 40 singletons. ST3, the most common ST in 54 STs, constituting 15.29% of all isolates, was also the most prevalent ST of isolates from the Liaocheng breeder duck farm (farm 3). CC1, the most prolific CC, containing 15.29% of the analyzed isolates, was the popular subtype of isolates from Liaocheng meat duck farm (farm 2). Although all the isolates belong to type A, the genetic diversity varied greatly in different regions; the Simpson's Diversity Index of STs for Liaocheng, Tai'an, and Weifang were 0.5941, 0.9198, and 0.9627, respectively. Some of cloacal isolates and environmental isolates were distributed in the same ST or CC, indicating close genetic relationship between cloacal isolates and environmental isolates. A portion of the strains from humans and ducks was found to be phylogenetically close. The close relationship between strains from humans and ducks, the high antibiotic resistance of C. perfringens, and the cpe-positive isolates indicated potential public health risks.

Genotyping and antimicrobial susceptibility of Clostridium perfringens isolated from dromedary camels, pastures and herders

The present study aimed to isolate and genotype C. perfringens from healthy and diarrheic dromedary camels, pastures and herders; and to evaluate and compare antimicrobial susceptibility of the isolates. A total of 262 (56.3%) C. perfringens isolates were recovered from 465 samples of healthy and diarrheic dromedary camels, pastures and herders. C. perfringens type A (75.2%), type B (4.2%), type C (13.7%) and type D (6.9%) were detected. C. perfringens type A with only cpa⁺ gene was found in 191 (72.9%) isolates and with cpa⁺ associated cpb2⁺ was found only in 6 (2.3%) isolates. None of the isolates were positive for cpe and iap genes. The highest antimicrobial resistance (82.8%) was observed to ceftiofur with MIC₅₀ and MIC₉₀ values of <64 and ≥256 μg/mL, respectively, followed by penicillin G (72.9%) and erythromycin (61.5%). The lowest resistance (1.9%) was observed for doxycycline with MIC₅₀ and MIC₉₀ values of <1 and 4 μg/mL, respectively, followed by florfenicol (5.3%) and clindamycin (12.2%). In conclusion, C. perfringens type A with cpa⁺ gene was the most prevalent toxin type isolated in this study. The majority of the isolates were resistant to at least one of the ten antimicrobials tested. Antimicrobial resistance patterns of C. perfringens isolates provide further evidence on the emergence of multiple-drug resistant C. perfringens. Therefore, the dissemination of surveillance programs to monitor and control C. perfringens in dromedary camels is required.

Antimicrobial Resistance in Clostridium and Brachyspira spp. and Other Anaerobes

This article describes the antimicrobial resistance to date of the most frequently encountered anaerobic bacterial pathogens of animals. The different sections show that antimicrobial resistance can vary depending on the antimicrobial, the anaerobe, and the resistance mechanism. The variability in antimicrobial resistance patterns is also associated with other factors such as geographic region and local antimicrobial usage. On occasion, the same resistance gene was observed in many anaerobes, whereas some were limited to certain anaerobes. This article focuses on antimicrobial resistance data of veterinary origin.

Characterization of toxin genes and quantitative analysis of netB in necrotic enteritis (NE)-producing and non-NE-producing Clostridium perfringens isolated from chickens

Necrotic enteritis (NE) in chickens, a Clostridium perfringens infection, has re-emerged due to the removal of antibiotic growth promoters in feeds in recent years, thus contributing to significant economic losses for the industry. Toxins produced by C. perfringens in conjunction with predisposing factors are responsible for the onset and development of NE. Recently, several lines of evidence indicated the potential role of plasmid-encoded toxins in the virulence of NE, particularly necrotic enteritis B-like (NetB) toxin. However, the association of NetB, beta2 toxin (CPB2), and C. perfringens large cytotoxin (TpeL) in clinical NE isolates are not well-established. Therefore, we characterized the toxinotype and the presence of netB, cpb2, and tpeL genes in 15 NE-producing and 15 non-NE-producing C. perfringens isolates using conventional PCR and quantified netB among those isolates by quantitative PCR (qPCR). All isolates were characterized as toxinotype A and were negative for cpe, which is associated with human food poisoning. The netB was detected in 6.7% and 70% of NE-producing isolates by PCR and qPCR, respectively. In 15 non-NE-producing isolates, netB was not detected by conventional PCR, but was detected in 60% of isolates by qPCR. The presence of and the copy number of netB were not significantly different between NE- and non-NE-producing isolates (p >0.05). No difference was observed between NE- and non-NE-producing isolates in the presence of cpb2 or tpeL (p >0.05). These results suggest that the presence of netB, cpb2, and tpeL, as well as the copy number of netB in C. perfringens is not correlated with clinical NE. In addition, we suggest that qPCR, but not conventional PCR, be used to detect netB.

Antimicrobial Resistance in Bacterial Poultry Pathogens: A Review

Antimicrobial resistance (AMR) is a global health threat, and antimicrobial usage and AMR in animal production is one of its contributing sources. Poultry is one of the most widespread types of meat consumed worldwide. Poultry flocks are often raised under intensive conditions using large amounts of antimicrobials to prevent and to treat disease, as well as for growth promotion. Antimicrobial resistant poultry pathogens may result in treatment failure, leading to economic losses, but also be a source of resistant bacteria/genes (including zoonotic bacteria) that may represent a risk to human health. Here we reviewed data on AMR in 12 poultry pathogens, including avian pathogenic Escherichia coli (APEC), Salmonella Pullorum/Gallinarum, Pasteurella multocida, Avibacterium paragallinarum, Gallibacterium anatis, Ornitobacterium rhinotracheale (ORT), Bordetella avium, Clostridium perfringens, Mycoplasma spp., Erysipelothrix rhusiopathiae, and Riemerella anatipestifer. A number of studies have demonstrated increases in resistance over time for S. Pullorum/Gallinarum, M. gallisepticum, and G. anatis. Among Enterobacteriaceae, APEC isolates displayed considerably higher levels of AMR compared with S. Pullorum/Gallinarum, with prevalence of resistance over >80% for ampicillin, amoxicillin, tetracycline across studies. Among the Gram-negative, non-Enterobacteriaceae pathogens, ORT had the highest levels of phenotypic resistance with median levels of AMR against co-trimoxazole, enrofloxacin, gentamicin, amoxicillin, and ceftiofur all exceeding 50%. In contrast, levels of resistance among P. multocida isolates were less than 20% for all antimicrobials. The study highlights considerable disparities in methodologies, as well as in criteria for phenotypic antimicrobial susceptibility testing and result interpretation. It is necessary to increase efforts to harmonize testing practices, and to promote free access to data on AMR in order to improve treatment guidelines as well as to monitor the evolution of AMR in poultry bacterial pathogens.