Antimicrobial susceptibility of Clostridium perfringens strains isolated from broiler chickens

Necrotic Enteritis in Broiler Chickens: A Review on the Pathogen, Pathogenesis, and Prevention

Clostridium perfringens type A and C are the primary etiological agents associated with necrotic enteritis (NE) in poultry. The predisposing factors implicated in the incidence of NE changes the physical properties of the gut, immunological status of birds, and disrupt the gut microbial homeostasis, causing an over-proliferation of C. perfringens. The principal virulence factors contributing to the pathogenesis of NE are the α-toxin, β-toxin, and NetB toxin. The immune response to NE in poultry is mediated by the Th1 pathway or cytotoxic T-lymphocytes. C. perfringens type A and C are also pathogenic in humans, and hence are of public health significance. C. perfringens intoxications are the third most common bacterial foodborne disease after Salmonella and Campylobacter. The restrictions on the use of antibiotics led to an increased incidence of NE in poultry. Hence, it is essential to develop alternative strategies to keep the prevalence of NE under check. The control strategies rely principally on the positive modulation of host immune response, nutritional manipulation, and pathogen reduction. Current knowledge on the etiology, pathogenesis, predisposing factors, immune response, effect on the gut microbial homeostasis, and preventative strategies of NE in this post-antibiotic era is addressed in this review.

Optimal Regimens and Clinical Breakpoint of Avilamycin Against Clostridium perfringens in Swine Based on PK-PD Study

Clostridium perfringens causes significant morbidity and mortality in swine worldwide. Avilamycin showed no cross resistance and good activity for treatment of C. perfringens. The aim of this study was to formulate optimal regimens of avilamycin treatment for C. perfringens infection based on the clinical breakpoint (CBP). The wild-type cutoff value (CO_WT) was defined as 0.25 μg/ml, which was developed based on the minimum inhibitory concentration (MIC) distributions of 120 C. perfringens isolates and calculated using ECOFFinder. Pharmacokinetics–pharmacodynamics (PK-PD) of avilamycin in ileal content were analyzed based on the high-performance liquid chromatography method and WinNonlin software to set up the target of PK/PD index (AUC_0–24h/MIC)_ex based on sigmoid E_max modeling. The PK parameters of AUC_0–24h, C_max, and T_max in the intestinal tract were 428.62 ± 14.23 h μg/mL, 146.30 ± 13.41 μg/ml,, and 4 h, respectively. The target of (AUC_0–24h/MIC)_ex for bactericidal activity in intestinal content was 36.15 h. The PK-PD cutoff value (CO_PD) was defined as 8 μg/ml and calculated by Monte Carlo simulation. The dose regimen designed from the PK-PD study was 5.2 mg/kg mixed feeding and administrated for the treatment of C. perfringens infection. Five respective strains with different MICs were selected as the infection pathogens, and the clinical cutoff value was defined as 0.125 μg/ml based on the relationship between MIC and the possibility of cure (POC) following nonlinear regression analysis, CART, and “Window” approach. The CBP was set to be 0.25 μg/ml and selected by the integrated decision tree recommended by the Clinical Laboratory of Standard Institute. The formulation of the optimal regimens and CBP is good for clinical treatment and to control drug resistance.

Antimicrobial use through consumption of medicated feeds in chicken flocks in the Mekong Delta of Vietnam: A three-year study before a ban on antimicrobial growth promoters

Antimicrobials are included in commercial animal feed rations in many low- and middle-income countries (LMICs). We measured antimicrobial use (AMU) in commercial feed products consumed by 338 small-scale chicken flocks in the Mekong Delta of Vietnam, before a gradual nationwide ban on prophylactic use of antimicrobials (including in commercial feeds) to be introduced in the country over the coming five years. We inspected the labels of commercial feeds and calculated amounts of antimicrobial active ingredients (AAIs) given to flocks. We framed these results in the context of overall AMU in chicken production, and highlighted those products that did not comply with Government regulations. Thirty-five of 99 (35.3%) different antimicrobial-containing feed products included at least one AAI. Eight different AAIs (avilamycin, bacitracin, chlortetracycline, colistin, enramycin, flavomycin, oxytetracycline, virginamycin) belonging to five classes were identified. Brooding feeds contained antimicrobials the most (60.0%), followed by grower (40.9%) and finisher feeds (20.0%). Quantitatively, chlortetracycline was consumed most (42.2 mg/kg SEM ±0.34; 50.0% of total use), followed by enramycin (18.4 mg/kg SEM ±0.03, 21.8%), bacitracin (16.4 mg/kg SEM ±0.20, 19.4%) and colistin (6.40 mg/kg SEM ± 4.21;7.6%). Other antimicrobials consumed were virgianamycin, avilamycin, flavomycin and oxytetracycline (each ≤0.50 mg/kg). Antimicrobials in commercial feeds were more commonly given to flocks in the earlier part of the production cycle. A total of 10 (9.3%) products were not compliant with existing Vietnamese regulation (06/2016/TT-BNNPTNT) either because they included a non-authorised AAI (4), had AAIs over the permitted limits (4), or both (2). A number of commercial feed formulations examined included colistin (polymyxin E), a critically important antimicrobial of highest priority for human medicine. These results illustrate the challenges for effective implementation and enforcement of restrictions of antimicrobials in commercial feeds in LMICs. Results from this study should help encourage discussion about policies on medicated feeds in LMICs.

A secondary bile acid from microbiota metabolism attenuates ileitis and bile acid reduction in subclinical necrotic enteritis in chickens

Background

Clostridium perfringens-induced chicken necrotic enteritis (NE) is responsible for substantial economic losses worldwide annually. Recently, as a result of antibiotic growth promoter prohibition, the prevalence of NE in chickens has reemerged. This study was aimed to reduce NE through titrating dietary deoxycholic acid (DCA) as an effective antimicrobial alternative.

Materials and methods

Day-old broiler chicks were assigned to six groups and fed diets supplemented with 0 (basal diet), 0.8, 1.0 and 1.5 g/kg (on top of basal diet) DCA. The birds were challenged with Eimeria maxima (20,000 oocysts/bird) at d 18 and C. perfringens (10⁹ CFU/bird per day) at d 23, 24, and 25 to induce NE. The birds were sacrificed at d 26 when ileal tissue and digesta were collected for analyzing histopathology, mRNA accumulation and C. perfringens colonization by real-time PCR, targeted metabolomics of bile acids, fluorescence in situ hybridization (FISH), or terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay.

Results

At the cellular level, birds infected with E. maxima and C. perfringens developed subclinical NE and showed shortening villi, crypt hyperplasia and immune cell infiltration in ileum. Dietary DCA alleviated the NE-induced ileal inflammation in a dose-dependent manner compared to NE control birds. Consistent with the increased histopathological scores, subclinical NE birds suffered body weight gain reduction compared to the uninfected birds, an effect attenuated with increased doses of dietary DCA. At the molecular level, the highest dose of DCA at 1.5 g/kg reduced C. perfringens luminal colonization compared to NE birds using PCR and FISH. Furthermore, the dietary DCA reduced subclinical NE-induced intestinal inflammatory gene expression and cell apoptosis using PCR and TUNEL assays. Upon further examining ileal bile acid pool through targeted metabolomics, subclinical NE reduced the total bile acid level in ileal digesta compared to uninfected birds. Notably, dietary DCA increased total bile acid and DCA levels in a dose-dependent manner compared to NE birds.

Conclusion

These results indicate that DCA attenuates NE-induced intestinal inflammation and bile acid reduction and could be an effective antimicrobial alternative against the intestinal disease.

Effect of Feed Additives as Alternatives to In-feed Antimicrobials on Production Performance and Intestinal Clostridium perfringens Counts in Broiler Chickens

Numerous non-antibiotic feed additives (alternatives to antibiotics, ATAs) have been marketed, but few have been evaluated under uniform testing conditions modelling commercial flocks. We compared 24 ATA treatments and the ionophorous coccidiostat narasin against a diet without any feed additives. Feed conversion ratio and body weight gain were registered from day 0 to 28 in Ross 308 chickens housed on litter floor. The chickens were challenged with Eimeria spp., and cecal Clostridium perfringens (CP) counts were investigated. Active components from all ATA classes had a positive impact on intestinal health or production performance. Whereas narasin had a strong CP-reducing effect in combination with performance-promoting impact, only two ATA treatments achieved significantly beneficial effects on CP counts as well as feed conversion during the time span following Eimeria challenge. Active components present in these two treatments include a Bacillus subtilis probiotic strain, short- and medium-chain fatty acids and Saccharomyces cerevisiae components. Different ATA classes had beneficial impact during distinct rearing phases and on specific performance targets, suggesting that optimizing combinations and use of active components can make ATAs even more useful tools in broiler rearing without the use of in-feed antimicrobials. Further studies of promising ATAs and ATA combinations are required.

The impact of Bacillus subtilis DSM 32315 on the pathology, performance, and intestinal microbiome of broiler chickens in a necrotic enteritis challenge

It was hypothesized that dietary inclusion of Bacillus subtilis DSM 32315 could inhibit Clostridium perfringens induced necrotic enteritis (NE), thereby improving broiler performance. Male, d 0 chicks were randomly assigned 14 birds/pen, 11 pens/treatment in 3 treatments: a basal diet (control), a coccidiostat fed control (Narasin), and a direct fed microbial (DFM) B. subtilis DSM 32315 treatment. Necrotic enteritis was induced in all birds by oral inoculation of Eimeria maxima oocysts on d 12 and a virulent C. perfringens on d 16. Mortality was reduced (P < 0.001) in DFM and Narasin compared to control. DFM reduced (P < 0.001) feed conversion ratio (FCR) compared to control. Furthermore, DFM and Narasin reduced (P < 0.001) footpad lesions. The DFM was shown to increase (P < 0.05) Bacillus spp. and decrease (P < 0.05) C. perfringens in the ileum and cecum at several time points. To investigate microbiome changes in the cecum, digesta samples were analyzed with % guanine and cytosine (%G+C) microbial profiling which fractionates bacterial chromosomes based on the %G+C in DNA. The method revealed treatment profile peaks in low (27.0 to 34.5%), mid (40.5 to 54.0%), and high (59.0 to 68.0%) G+C fractions. 16S rRNA gene amplification and high throughput sequencing was conducted on each of these fractions in order to elucidate specific bacterial population differences. In the low and mid %G+C fractions, DFM had greater abundance of Lactobacillaceae family members (P = 0.03 and P = 0.01, respectively) and Lactobacillus salivarius (P = 0.04 and P = 0.01, respectively) than control or Narasin. Lactobacillus johnsonii was also greater in the low %G+C fraction compared to control and Narasin (P = 0.01). Lachnospiraceae (P = 0.04) and Ruminococcaceae (P < 0.01) in the mid %G+C fraction were reduced in the DFM compared to control. Positive alterations to the microbial populations in the gut of broilers may at least be a partial mechanism by which B. subtilis DSM 32315 reduced pathology and improved performance of broilers in the NE challenge.

The prevalence of antibiotic-resistant Clostridium species in Iran: a meta-analysis

Clostridium species are ubiquitous and associated with various diseases in animals and humans. However, there is little knowledge about the prevalence of their resistance to antibiotics in Iran. Therefore, the aim of this study was to determine the prevalence of antibiotic-resistant Clostridium species in Iran through a meta-analysis of eligible studies published up until December 2018. Fourteen articles on the drug resistance of Clostridium species in Iran were included in the current study following a search in PubMed, Scopus and Google Scholar databases using relevant keywords and screening based on inclusion and exclusion criteria. Antibiotic resistance rates of C. difficile to ampicillin (42.8%), ciprofloxacin (69.5%), clindamycin (84.3%), erythromycin (61.5%), gentamicin (93.5%), nalidixic acid (92.9%), tetracycline (32.5%), imipenem (39.6%), levofloxacin (93.4%), ertapenem (58.7%), piperacillin/tazobactam (56.5%), kanamycin (100%), colistin (100%), ceftazidime (76%), amikacin (76.5%), moxifloxacin (67.9%) and cefotaxime (95%) were high. In addition, resistance of C. perfringens to ampicillin (25.8%), erythromycin (32.9%), gentamicin (45.4%), nalidixic acid (52.5%), tetracycline (19.5%), penicillin (21.8%), trimethoprim-sulfamethoxazole (32.1%), amoxicillin (19.3%), imipenem (38%), cloxacillin (100%), oxacillin (45.6%), bacitracin (89.1%) and colistin (40%) was high. Metronidazole and vancomycin, as the first-line therapies, fidaxomicin, tetracyclines (except tetracycline), rifampicin and chloramphenicol can still be used for the treatment of C. difficile infections. However, the present results do not recommend the use of penicillin, bacitracin and tetracycline for the treatment of C. perfringens infections in humans and domestic animals in Iran.

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.

Recurring Necrotic Enteritis Outbreaks in Commercial Broiler Chicken Flocks Strongly Influence Toxin Gene Carriage and Species Richness in the Resident Clostridium perfringens Population

Extensive use of antibiotic growth promoters (AGPs) in food animals has been questioned due to the globally increasing problem of antibiotic resistance. For the poultry industry, digestive health management following AGP withdrawal in Europe has been a challenge, especially the control of necrotic enteritis. Much research work has focused on gut health in commercial broiler chicken husbandry. Understanding the behavior of Clostridium perfringens in its ecological niche, the poultry barn, is key to a sustainable and cost-effective production in the absence of AGPs. Using polymerase chain reaction and pulsed-field gel electrophoresis, we evaluated how the C. perfringens population evolved in drug-free commercial broiler chicken farms, either healthy or affected with recurring clinical necrotic enteritis outbreaks, over a 14-month period. We show that a high genotypic richness was associated with an increased risk of clinical necrotic enteritis. Also, necrotic enteritis-affected farms had a significant reduction of C. perfringens genotypic richness over time, an increase in the proportion of C. perfringens strains harboring the cpb2 gene, the netB gene, or both. Thus, necrotic enteritis occurrence is correlated with the presence of an initial highly diverse C. perfringens population, increasing the opportunity for the selective sweep of particularly virulent genotypes. Disease outbreaks also appear to largely influence the evolution of this bacterial species in poultry farms over time.

Detection of toxins A/B and isolation of Clostridium difficile and Clostridium perfringens from dogs in Minas Gerais, Brazil

The objective of this study was to detect C. difficile A/B toxins and to isolate strains of C. perfringens and C. difficile from diarrheic and non-diarrheic dogs in Brazil. Stool samples were collected from 57 dogs, 35 of which were apparently healthy, and 22 of which were diarrheic. C. difficile A/B toxins were detected by ELISA, and C. perfringens and C. difficile were identified by multiplex PCR. C. difficile A/B toxins were detected in 21 samples (36.8%). Of these, 16 (76.2%) were from diarrheic dogs, and five (23.8%) were from non-diarrheic dogs. Twelve C. difficile strains (21.1%) were isolated, of which ten were A⁺B⁺ and two were A⁻B⁻. All non-toxigenic strains were isolated from non-diarrheic animals. The binary toxin gene cdtB was found in one strain, which was A⁺B⁺ and was derived from a non-diarrheic dog. C. perfringens strains were isolated from 40 samples (70.2%). Of these, 18 (45%) were from the diarrheic group, and 22 (55%) belonged to the non-diarrheic group. All isolates were classified as C. perfringens type A and there was an association between the detection of the cpe gene and the presence of diarrhea. Interestingly, ten strains (25%) were positive for the presence of the cpb2 gene. The high rate of detection of the A/B toxins in non-diarrheic dogs suggests the occurrence of subclinical disease in dogs or carriage of its toxins without disease. More studies are needed to elucidate the epidemiology of C. difficile and C. perfringens in dogs and to better our understanding of C. difficile as a zoonotic agent. This is the first study to report the binary toxin gene in C. difficile strains isolated from dogs in Brazil.