NetB, a new toxin that is associated with avian necrotic enteritis caused by Clostridium perfringens

For over 30 years a phospholipase C enzyme called alpha-toxin was thought to be the key virulence factor in necrotic enteritis caused by Clostridium perfringens. However, using a gene knockout mutant we have recently shown that alpha-toxin is not essential for pathogenesis. We have now discovered a key virulence determinant. A novel toxin (NetB) was identified in a C. perfringens strain isolated from a chicken suffering from necrotic enteritis (NE). The toxin displayed limited amino acid sequence similarity to several pore forming toxins including beta-toxin from C. perfringens (38% identity) and alpha-toxin from Staphylococcus aureus (31% identity). NetB was only identified in C. perfringens type A strains isolated from chickens suffering NE. Both purified native NetB and recombinant NetB displayed cytotoxic activity against the chicken leghorn male hepatoma cell line LMH; inducing cell rounding and lysis. To determine the role of NetB in NE a netB mutant of a virulent C. perfringens chicken isolate was constructed by homologous recombination, and its virulence assessed in a chicken disease model. The netB mutant was unable to cause disease whereas the wild-type parent strain and the netB mutant complemented with a wild-type netB gene caused significant levels of NE. These data show unequivocally that in this isolate a functional NetB toxin is critical for the ability of C. perfringens to cause NE in chickens. This novel toxin is the first definitive virulence factor to be identified in avian C. perfringens strains capable of causing NE. Furthermore, the netB mutant is the first rationally attenuated strain obtained in an NE-causing isolate of C. perfringens; as such it has considerable vaccine potential.

Clostridium perfringens can cause gas gangrene and food poisoning in humans and causes several enterotoxemic diseases in animals including avian necrotic enteritis. This disease affects all chicken producing countries worldwide and is a considerable burden on the commercial chicken production industry. Until recently alpha-toxin was thought to be the major virulence factor involved in necrotic enteritis. However, by using an alpha-toxin null mutant it has been demonstrated that this toxin is not essential for disease. This paper details the identification and characterisation of a novel toxin, NetB, and provides evidence that the protein is an essential factor in causing necrotic enteritis in chickens. NetB has limited protein sequence identity to the beta-toxin of C. perfringens, which causes mucosal necrosis of the small intestine in humans and animals. We demonstrate that NetB null mutants can no longer cause disease in chickens, whereas both the wild-type and mutant complemented with a wild-type netB gene caused significant levels of necrotic enteritis. The identification of this important toxin advances our understanding of the pathogenesis of the disease and opens significant opportunities for the development of novel vaccines against necrotic enteritis in poultry.

Clinical severity of Clostridium difficile PCR ribotype 027: a case-case study

BACKGROUND

Clostridium difficile is a leading infectious cause of health care associated diarrhoea. Several industrialised countries have reported increased C. difficile infections and outbreaks, which have been attributed to the emergent PCR ribotype 027 strain.

METHODS AND FINDINGS

We conducted a case-case study to compare severity of C. difficile disease for patients with 027 versus non-027 ribotypes. We retrospectively collected clinical information about 123/136 patients with C. difficile infections admitted to hospitals in the East of England region in 2006 and from whom stool isolates were cultured and ribotyped as part of an earlier national survey. We defined severe C. difficile disease as having one or more of shock, paralytic ileus, pseudo membranous colitis or toxic megacolon. Patient median age was 83 years old (range 3 to 98, interquartile range 75 to 89), 86% were prescribed antibiotics in the eight weeks before illness onset, 41% had ribotype 027 and 30-day all cause mortality during hospital admission was 21%. Severe disease occurred in 24% (95%CI 13% to 37%) and 17% (95%CI 9% to 27%) of patients with PCR ribotype 027 and non-027 ribotypes respectively. In a multivariable model, ribotype 027 was not associated with severe disease after adjusting for sex, discharge from hospital prior to 60 days of current admission, gastroenteritis on admission, number of initiator antibiotics for C. difficile disease, and hospital where the patient was admitted.

CONCLUSIONS

Our study found no evidence to support previous assertions that ribotype 027 is more virulent than other PCR ribotypes. This finding raises questions about the contribution of this strain to the recent increase in C. difficile disease throughout North America and Europe.

Clostridial sacroiliitis in a patient with fecal incontinence: a case report and review of the literature

INTRODUCTION

Image-guided sacroiliac joint injections are frequently employed for both diagnostic and therapeutic relief of low back pain.

CASE REPORT

An 83-year-old male with chronic lumbrosacral pain previously responsive to right sacroliac joint injections presented for repeat injection. His medical history included Parkinsonism and stool incontinence. Forty-two hours after the injection, he developed fever, dyspnea, and crepitus on the right buttock and thigh. Surgical debridement was recommended, but the family wished for comfort care only. The patient died hours later. The autopsy revealed Gram positive bacilli consistent with Clostridial myonecrosis.

DISCUSSION

Pyogenic sacroiliitis is rare and usually occurs in the setting of trauma, drug abuse, or extraspinal infections. Joint infections with Clostridium have been reported after traumatic events including puncture, surgery, and abrasions. Clostridium spores are resistant to chemical preparations used for skin sterilization and require high heat for destruction. Possible practice guidelines with patients that are stool incontinent include mechanical wash prior to sterile preparation and placement of an occlusive sterile dressing after injection to prevent stool contamination of the needle puncture site. As with all rare complications, large scale studies are needed to better identify risk factors to formulate practice management strategies.

Necrotic enteritis-producing strains of Clostridium perfringens displace non-necrotic enteritis strains from the gut of chicks

We inoculated broiler chicks with mixtures of Clostridium perfringens strains to investigate the single strain dominance observed in natural cases of necrotic enteritis (NE) [Nauerby, B., Pedersen, K., Madsen, M., 2003. Analysis by pulsed-field gel electrophoresis of the genetic diversity among Clostridium perfringens isolates from chickens. Vet. Microbiol. 94, 257-266]. Pre-inoculation bacteriologic culture of chick intestines yielded up to six pulsed-field gel electrophoresis (PFGE) types of C. perfringens. Birds developed typical NE lesions in response to administration (2x per day for 4 days) of a combined inoculum comprising one NE strain (JGS4143, PFGE pattern 8) and four non-NE strains (from piglet necrotizing enteritis, chicken normal flora, human gas gangrene, and bovine neonatal enteritis). After inoculation commenced, only the NE strain was recovered through the first post-inoculation day, in spite of intense efforts to recover pre-challenge flora strains and the other challenge strains. Thereafter, pre-inoculation and previously undetected PFGE types were found, and JGS4143 became undetectable. Birds inoculated simultaneously with five NE strains (from disease in chickens or turkeys, and including JGS4143) also developed lesions, but again only JGS4143 was recovered through the 1st day post-challenge. At that time, birds began to be repopulated with pre-challenge PFGE types. Two NE strains (JGS4143 and JGS4064) produced bacteriocins, which inhibited each other and normal flora strains (n=17), while normal flora strains inhibited neither NE strains nor each other. Thus, it appears that naturally occurring dominance of the gut by NE strains can be reproduced experimentally. Bacteriocins directed against normal flora could possibly provide the necessary advantage, although inhibition of one NE strain by another suggests that other factors may be partially or completely responsible for the dominance.

Quantification of gut lesions in a subclinical necrotic enteritis model

Currently Clostridium perfringens-induced necrotic enteritis is a major problem in broiler flocks. In the present study, broilers were inoculated with a combination of Eimeria maxima or overdose coccidial vaccine (one inoculation) with C. perfringens (repeated inoculations). Single C. perfringens, E. maxima or an overdose of live coccidial vaccine inoculations did not result in grossly visible necrotic gut lesions, while combined inoculation resulted in typical necrotic lesions at approximately 4 days after inoculations with C. perfringens in approximately one-half of the inoculated animals. Semi-quantitative histological lesion scoring was done to evaluate gut damage in gut sections of animals in which no gross necrotic lesions were detected. This included scoring of hyperaemia, haemorrhages, the amount of red blood cells and protein precipitate in the lumen, villus fusion and epithelial defects. The villus length and the villus length/crypt depth ratio were also analysed. This approach proved to be discriminative between single E. maxima infection, overdose of coccidial vaccine or C. perfringens inoculations and the non-inoculated control group, and between the double-inoculated and single-inoculated groups. In general, the highest histological scores for gut lesions were observed in the double-inoculated groups, but the single-inoculated groups had higher scores than the control group. It was concluded that oral inoculation of broilers with an overdose of live coccidial vaccine in combination with multiple oral C. perfringens inoculations is a suitable model for necrotic enteritis without inducing mortality of the animals. C. perfringens and Eimeria act synergistically in inducing grossly visible gut damage.

Leger J, Puschner B, Fisher DJ, McClane BA, Uzal FA. Necrotizing enterocolitis and death in a goat kid associated with enterotoxin (CPE)-producing Clostridium perfringens type A

A goat kid died after being depressed for several days. No significant gross abnormalities were observed at postmortem examination, while histopathological analysis revealed diffuse necrotizing enterocolitis. Isolation of Clostridium perfringens type A secreting enterotoxin (CPE) and presence of CPE in the small intestine suggest that CPE contributed to the death of this kid.

Enteritis necroticans 'pigbel' in a Japanese diabetic adult

Enteritis necroticans 'pigbel' is caused by Clostridium perfringens type C but has rarely been reported in developed countries. A 50-year-old Japanese man with untreated diabetes mellitus (DM) presented with diarrhea and abdominal pain. Intraoperative endoscopic and macroscopic examination disclosed segmental annular mucosal lesions characteristic of clostridial enteritis. Clostridial infection type C was verified on pathological, and immunohistochemical analysis. Although rare, the disease is likely to be underdiagnosed. Hence, the pathology and immunohistochemistry of segmental enteritis with annular mucosal lesions should be examined to establish a diagnosis of enteritis necroticans even in mildly affected patients, and especially those with DM.

Massive intravascular hemolysis in a patient infected by a Clostridium perfringens

Clostridium perfringens infection is a very rare cause of massive intravascular hemolysis, but it should always be kept in mind, since only early treatment can rescue patients from an otherwise rapidly fatal outcome. We report a case of a 78-year-old diabetic male who was admitted complaining of general fatigue, dark red urine, and vomiting. His blood revealed massive hemolysis. Computer tomography demonstrated huge liver abscess in the right lobe of the liver. About 1 h after admission, he suddenly fell into a critical condition. He died 3 h after admission in spite of intensive care and resuscitation. Clostridium perfringens was detected from the blood taken before death and from liver abscess by biopsy after death. We concluded that this patient died of acute massive intravascular hemolysis in septicemia caused by Clostridium perfringens infection.

An observation of Clostridium perfringens in Greater Sage-Grouse

Mortality due to infectious diseases is seldom reported in the Greater Sage-Grouse (Centrocercus urophasianus). A case of necrotic enteritis associated with Clostridium perfringens type A is described in a free-ranging adult male sage-grouse in eastern Oregon. Clostridial enteritis is known to cause outbreaks of mortality in various domestic and wild birds, and should be considered as a potential cause of mortality in sage-grouse populations.

Association between gizzard lesions and increased caecal Clostridium perfringens counts in broiler chickens

The aim of this study was to investigate the relationship between mucosal gizzard lesions and caecal Clostridium perfringens counts. Gross pathological changes in the gizzard and small intestine, and caecal C. perfringens counts from 1217 meat-type chickens were recorded during the course of six experiments and were statistically analysed. C. perfringens counts increased significantly (P < 0.001) with the severity of mucosal gizzard lesions. Mucosal gizzard lesions were more prevalent than necrotic enteritis. Correcting for the pen and necrotic enteritis within experiment, mucosal gizzard lesions explained 31.8% of the variation in C. perfringens counts. Mucosal gizzard lesions and age together explained 59.1% of the variation in C. perfringens counts. The mean ages of birds with moderate and severe mucosal gizzard lesions were 1.7 and 0.8 days lower than the mean age of birds with necrotic enteritis, respectively. The association between mucosal gizzard lesions and high C. perfringens counts might be of importance when attempting to improve production efficiency, health and the welfare of the chickens.

Toxin production by and adhesive properties of Clostridium difficile isolated from humans and horses with antibiotic-associated diarrhea

Clostridium difficile is a common nosocomial pathogen in humans and animals that causes diarrhea and colitis following antibiotic therapy. Isolates of C. difficile obtained from faecal material from 20 human patients and 6 equine subjects with antibiotic-associated diarrhea were investigated regarding production of toxins A and B, their capacity to adhere to the human intestinal Caco-2 cell line and equine intestinal cells, and for the presence of fimbriae. The results showed that most (17/20) of the human clinical isolates produced both toxins A and B. One of the human isolates proved toxin A-negative/toxin B-positive. All (6/6) horse isolates were positive for both toxins A and B. Both the human and horse isolates possessed the capacity to adhere, to varying degree, to human and equine intestinal cells. It appeared that human isolates produced greater amounts of toxin B, and that there was a host-species dependency on ability to attach to intestinal epithelial cells. No fimbriae were found in any of the investigated isolates.

Fatal myocarditis due to Clostridium novyi type B in a previously healthy woman: case report and literature review

Clostridium novyi is a Gram-positive anaerobe, which is commonly a pathogen of domestic and wild animals. Disease in humans typically presents as myonecrosis. C. novyi has not previously been reported as a cause of myocarditis. We report a fatal case with infection of the myocardium by C. novyi type B.

[High mortality in a herd with signs of jejunal hemorrhage syndrome]

Eleven cows from a herd of 80 dairy cows (14%) died over a 7-month period. Death occurred within 12-24 hours of the onset of the first clinical signs, namely, dullness and a decrease (mean 25%) in milk production. Within 12 hours the cows were unable to rise, felt cold, and were restless. Examined mucous membranes were pale. Two of three cows examined at necropsy had blood in the jejunum and high counts of Clostridium perfringens. Jejunal hemorrhage syndrome was diagnosed in these two cows on the basis of the clinical signs and postmortem findings.

Naturally occurring Tyzzer's disease in cotton-top tamarins (Saguinus oedipus)

We noted naturally occurring infection with Clostridium piliforme (Tyzzer's disease) in 2 captive-reared cotton-top tamarins (Saguinus oedipus). Spontaneous Tyzzer's disease has been reported in multiple species of laboratory, domestic, and wild animals but is extremely rare in humans and nonhuman primates. Distinct from idiopathic colitis, which is common in cotton-top tamarins, these 2 tamarins had severe, transmural, necrotizing typhlocolitis accompanied by myocarditis and hepatitis. Abundant bacteria compatible with C. piliforme, the etiologic agent of Tyzzer's disease, were present adjacent to lesions in the cecum-colon, liver, and heart. Therefore, colitis caused by C. piliforme, although rare, should be included as a differential diagnosis in cotton-top tamarins and as a cause of postnatal mortality in this species.

Haemorrhagic Bowel Syndrome in Dairy Cattle: Possible Role of Clostridium perfringens Type A in the Disease Complex

A survey based on clinical, pathological and microbiological investigations was performed on 11 Brown Swiss cattle affected with depression, anorexia, agalaxia, ruminal hypomotility, abdominal pain and melaena. In eight animals, macroscopical lesions consisted in haemorrhagic enteritis in the small intestine. Seven of eight isolates from tissue samples were identified as Clostridum perfringens type A, and four were identified as C. perfringens type A with the beta2 toxin gene. Based on these observations, animals were considered affected with haemorrhagic bowel syndrome.

Isolation of Clostridium tertium from a striped dolphin (Stenella coeruleoalba) in the Adriatic Sea

Bacteriologic examination of an abscess found between blubber and musculature of a striped dolphin (Stenella coeruleoalba) found dead on 30 March 2002 in the Adriatic Sea, Croatia, was performed and an aerotolerant, nontoxogenic Clostridium tertium was isolated in pure culture. National Collections of Industrial Food and Marine Bacteria (NCIMB Ltd., Aberdeen, Scotland, UK) confirmed the results. Sequencing results showed it to be C. tertium with 100% similarity. The strain was named Clostridium tertium strain Zagreb, acceded to the culture collection and assigned the accession number NCIMB 13970. This is the first record of C. tertium in marine mammals.

Immunohistochemical evidence of Clostridium sp, Staphylococcus aureus, and group A Streptococcus in severe soft tissue infections related to injection drug use

Severe soft tissue infections are caused by either single or multiple microorganisms. We performed a retrospective immunohistochemical (IHC) study on formalin-fixed, paraffin-embedded soft tissue samples from 20 injection drug users who were part of a cluster of severe illness and death after skin and soft tissue infections in Scotland and Ireland in 2000. The IHC assays used antibodies against Clostridium sp, Staphylococcus aureus, group A streptococci, and Bacillus anthracis. Intact bacilli and granular Clostridium antigen staining in areas with necrosis, edema, and inflammation were observed in skin, fascia, or muscle samples of 12 (60%) patients. A variety of clostridia were isolated from affected soft tissues in 10 IHC-positive cases. Staphylococcus aureus antigens were observed in 3 cases including 1 where S aureus was isolated, 1 with negative cultures, and 1 where mixed cultures were obtained. Group A streptococcal antigens were observed in 1 case in which Streptococcus pyogenes and S aureus were isolated. By using IHC, we detected different bacteria in archival soft tissue samples from patients with severe skin and soft tissue infections. Immunohistochemical assays can be of great diagnostic value, particularly for bacteria such as Clostridium sp, which are difficult to isolate because of their anaerobic fastidious growth requirements.

Clostridium septicum infections in children: a case report and review of the literature

Clostridium myonecrosis is a rare and deadly infection that progresses very rapidly; thus, prompt diagnosis and treatment is vital. In adults, clostridial myonecrosis used to be a well-known complication of war wounds. Today, it is usually seen in settings of trauma, surgery, malignancy, skin infections/burns, and septic abortions. More recently, cases of nontraumatic or spontaneous clostridial myonecrosis have been reported in both adults and children. Clostridium perfringens and Clostridium septicum are responsible for the majority of the clinically relevant infections. Higher mortality rates are seen when C septicum is the causative agent. Here we present a child who survived a severe case of C septicum myonecrosis involving both abdominal and thoracic cavities. This rare infection has a high mortality rate and might be easily misdiagnosed in children, even by experienced clinicians, because of its nonspecific presentation. We also review all reported pediatric cases of C septicum infection and myonecrosis and discuss the surgical and medical interventions associated with improved survival. We identified a total of 47 cases of C septicum infection; of these, 22 (47%) were cases of C septicum associated with myonecrosis. Several factors, if available, were analyzed for each case: age, gender, infection location, previous diagnoses, presenting signs and symptoms, neutropenia, gross pathology of the colon, antibiotic use, surgical intervention, and final outcome. We found that conditions related with C septicum infection in children can be grouped into 3 major categories: patients with neutrophil dysfunction; patients with associated bowel ischemia; and patients with a history of trauma. Malignancies were found in 49% of the cases, cyclic or congenital neutropenia in 21%, hemolytic-uremic syndrome in 11%, structural bowel ischemia in 4%, and local extremity trauma in 6%. In addition, 6% of the cases had no known underlying disorder. Abdominal symptoms including vomiting, diarrhea, blood per rectum, abdominal pain, anorexia, and/or acute abdomen, were reported in 85% of the children. Fever was also a common finding. The mainstay of treatment for C septicum infection was parenteral antibiotics and/or surgical intervention. The mortality rate for children with C septicum infection and myonecrosis was 57% and 59%, respectively. Although 82% of all cases received antibiotics, only 43% underwent therapeutic surgical intervention. Several clinical factors were found to be associated with improved survival. Only 35% of the children with gastrointestinal tract involvement survived, compared with 86% of the children without gastrointestinal tract involvement. The survival rates for other conditions ranged from 0% to 50%. One hundred percent survival was reported in patients with no previously diagnosed conditions and those with infections resulting from trauma to the extremities. All survivors received antibiotic treatment, compared with only 68% of the nonsurvivors. Most survivors (84%) underwent therapeutic surgical intervention, compared with only 12% of nonsurvivors. Other treatments were used adjunctively, including hyperbaric oxygen, granulocyte colony-stimulating factor, granulocyte transfusions, and intravenous immunoglobulin. C septicum infections in children are often fatal; thus, one needs to have a high index of suspicion in at-risk patients. This review describes who these patients are, their clinical presentation, and the therapeutic strategies associated with improved survival.

Ulcerative enteritis (quail disease) in lories

Ulcerative enteritis is found in a wide range of avian hosts but has not been described in psittacine birds. This case report describes ulcerative enteritis in four lories (two Trichoglossus sp. and two Eos sp.) that were found dead without any previous sign of disease. Macroscopically, all four birds showed good body condition. The only remarkable finding was a moderate dilatation of the small intestine with the presence of multiple yellow foci. Histologically, multiple ulcers extended into the submucosa and were filled with necrotic debris; bacteria and fibrin were observed in the intestinal mucosa. The liver and spleen exhibited a multifocal fibrinoid necrosis associated with a very moderate inflammatory reaction. Microbiological isolation revealed colonies of Clostridium colinum and Clostridium perfringens in the intestinal tract of the investigated birds.

Clostridium perfringens toxin-types in lambs and kids affected with gastroenteric pathologies in Italy

A study was carried out in the South of Italy to assess the role of clostridia in neonatal diseases of lambs and kids. Eighty-seven lambs and 15 kids belonging to 25 flocks were examined and Clostridium perfringens was the microorganism most commonly identified. C. perfringens isolates were analysed by polymerase chain reaction (PCR), in order to determine the prevalence of the genes cpa, cpb, cpb2, etx, iap and cpe. The most prevalent toxin-type of C. perfringens was found to be type A found in 84% of the cases with clostridial enterotoxaemia. No C. perfringens type B, C or E were found. C. perfringens type D was isolated in 16% of the cases. About 24% of the isolates were cpb2 positive. The prevalence of cpb2 across the different C. perfringens types varied. The beta(2)-toxin gene cpb2 was detected in 4/21 (19%) type A isolates, in 1/2 type D isolates, and in 1/2 type DE (cpe-carrying type D) isolates. The high rate of positivity to cpb2 among the isolates suggests that a vaccine based on the beta(2)-toxin, should be included in the vaccination schedule of the animals to confer adequate protection and to prevent the disease.

The alpha-toxin of Clostridium septicum is essential for virulence

Clostridium septicum is the causative agent of spontaneous gas gangrene or atraumatic myonecrosis, a sudden and frequently fatal infection that is increasingly associated with malignancy of the colon. Little is known about the disease process although the focus of virulence studies has been the alpha-toxin, a pore-forming cytolysin that is encoded by the csa gene and secreted as an inactive protoxin. Until now a lack of techniques for the genetic manipulation of C. septicum has hindered the use of molecular approaches to understand pathogenesis. By introducing plasmids by conjugation from Escherichia coli, we have developed methods for the genetic manipulation of C. septicum and constructed a chromosomal csa mutant by allelic exchange. Virulence testing of an isogenic series of strains consisting of the wild type, the csa mutant, and a csa mutant complemented with the wild-type csa gene revealed that the development of fulminant myonecrosis in mice was dependent on the ability to produce a functional haemolytic alpha-toxin. Furthermore, the inhibition of leukocyte influx into the lesion, which is very typical of clostridial myonecrosis, was also dependent on the ability to produce alpha-toxin. This study represents the first definitive identification of a virulence factor in this organism and opens the way for further studies that will delineate the role of other putative virulence factors in this significant pathogen.

Secondary infection of intracranial hydatid cyst with Clostridium ramosum

INTRODUCTION

Brain involvement in hydatid disease occurs in 1-2% of all Echinococcus granulosus infections. Secondary infection of intracranial hydatid cysts is extremely rare.

CASE REPORT AND DISCUSSION

In this case report, we present a secondary infection of an intracranial hydatid cyst due to Clostridium ramosum, which is an extremely rare infectious pathogen in neurosurgical practice, and a potential pitfall in neuroradiological investigations.

[Emphysematous cystitis due to Clostridium perfringens--a localised infection in a man with generalized melanoma]

Emphysematous cystitis was found at autopsy of a 47-year-old man suffering from generalised malignant melanoma. Bacteriological cultures from the urinary bladder showed Escherichia coli, Klebsiella sp. and Clostridium perfringens type A, toxic strain. The histological examination revealed cystic dilatation of lymphatic vessels both in bladder mucosa and muscularis propria. There were multinucleated macrophages in the lining of some of these cystic spaces and a few Gram-positive rods inside their lumina. In the mucosal and submucosal connective tissue there were signs of chronic inflammation and, focally, small haemorrhages. We suppose that the gas production was due to the presence of Clostridium perfringens and believe that the infection of the urinary bladder occurred in relation to the repeated insertion of the catheter into the bladder of a patient with secondary immunosuppression. Emphysematous cystitis was, in our case, a localised clostridial infection without clinical and morphological signs of generalised septicaemia.