The pathogenesis of clostridial myonecrosis

Clostridial Diseases of Horses: A Review

The clostridial diseases of horses can be divided into three major groups: enteric/enterotoxic, histotoxic, and neurotoxic. The main enteric/enterotoxic diseases include those produced by Clostridium perfringens type C and Clostridioides difficile, both of which are characterized by enterocolitis. The main histotoxic diseases are gas gangrene, Tyzzer disease, and infectious necrotic hepatitis. Gas gangrene is produced by one or more of the following microorganisms: C. perfringens type A, Clostridium septicum, Paeniclostridium sordellii, and Clostridium novyi type A, and it is characterized by necrotizing cellulitis and/or myositis. Tyzzer disease is produced by Clostridium piliforme and is mainly characterized by multifocal necrotizing hepatitis. Infectious necrotic hepatitis is produced by Clostridium novyi type B and is characterized by focal necrotizing hepatitis. The main neurotoxic clostridial diseases are tetanus and botulism, which are produced by Clostridium tetani and Clostridium botulinum, respectively. Tetanus is characterized by spastic paralysis and botulism by flaccid paralysis. Neither disease present with specific gross or microscopic lesions. The pathogenesis of clostridial diseases involves the production of toxins. Confirming a diagnosis of some of the clostridial diseases of horses is sometimes difficult, mainly because some agents can be present in tissues of normal animals. This paper reviews the main clostridial diseases of horses.

Amentoflavone Attenuates Clostridium perfringens Gas Gangrene by Targeting Alpha-Toxin and Perfringolysin O

Clostridium perfringens (C. perfringens) type A strains are the main cause of gas gangrene in humans and animals. Treatment of this lethal disease is limited, and the prognosis is not good. Alpha-toxin (CPA) and perfringolysin O (PFO) secreted by C. perfringens play irreplaceable roles in cytotoxicity to host cells, persistence in host tissues, and lethality of gas gangrene pathology. This work determined the influence of amentoflavone, a biflavonoid isolated from Selaginella tamariscina and other plants, on hemolysis and cytotoxicity mediated by CPA and PFO and evaluated the in vivo therapeutic effect on gas gangrene. Our data showed that amentoflavone could block the hemolysis and cytotoxicity induced by CPA and PFO in vitro, thereby mediating significant protection against mortality of infected mice in a mouse gas gangrene model, efficient bacterial clearance in tissues and alleviation of histological damage in vivo. Based on the above results, amentoflavone may be a potential candidate against C. perfringens infection by reducing CPA and PFO-mediated virulence.

Gas gangrene in mammals: a review

Gas gangrene is a necrotizing infection of subcutaneous tissue and muscle that affects mainly ruminants and horses, but also other domestic and wild mammals. Clostridium chauvoei, C. septicum, C. novyi type A, C. perfringens type A, and C. sordellii are the etiologic agents of this disease, acting singly or in combination. Although a presumptive diagnosis of gas gangrene can be established based on clinical history, clinical signs, and gross and microscopic changes, identification of the clostridia involved is required for confirmatory diagnosis. Gross and microscopic lesions are, however, highly suggestive of the disease. Although the disease has a worldwide distribution and can cause significant economic losses, the literature is limited mostly to case reports. Thus, we have reviewed the current knowledge of gas gangrene in mammals.

Histotoxic Clostridial Infections

The pathogenesis of clostridial myonecrosis or gas gangrene involves an interruption to the blood supply to the infected tissues, often via a traumatic wound, anaerobic growth of the infecting clostridial cells, the production of extracellular toxins, and toxin-mediated cell and tissue damage. This review focuses on host-pathogen interactions in Clostridium perfringens -mediated and Clostridium septicum -mediated myonecrosis. The major toxins involved are C. perfringens α-toxin, which has phospholipase C and sphingomyelinase activity, and C. septicum α-toxin, a β-pore-forming toxin that belongs to the aerolysin family. Although these toxins are cytotoxic, their effects on host cells are quite complex, with a range of intracellular cell signaling pathways induced by their action on host cell membranes.

Hyperbaric oxygenation in pediatrics: indications in the light of evidence - based medicine

Hyperbaric oxygen therapy (HBOT), which is a centuries-old treatment, has now increasingly often been used in the pediatric population. The basic indications for HBOT are well-known disease entities, i.e. carbon monoxide poisoning or decompression sickness. Due to the immunomodulatory properties of hyperbaric oxygen, attempts are made to use HBOT in the treatment of atopic dermatitis or inflammatory bowel diseases. The close cooperation between pediatricians and hyperbaric medicine teams is very important to obtain optimal results. The aim of this article is to present the mechanism of hyperbaric oxygen activity, and its influence on selected disease entities. The paper outlines new perspectives for HBOT in the pediatric population.

Ethanolamine utilization supports Clostridium perfringens growth in infected tissues

Clostridium perfringens possesses the ethanolamine (EA) utilization (eut) system encoded within the eut operon, which utilizes the EA as a carbon, nitrogen and energy source. To determine the role of the eut system in C. perfringens growth, an in-frame deletion of the eutABC genes was made in strain HN13 to generate the eutABC-deleted mutant strain HY1701. Comparison of HN13 and HY1701 growth in media supplemented with 1.0% glucose and/or 1.0% EA showed that glucose enhanced the growth of both strains, whereas EA enhanced HN13 growth, but not that of HY1701, indicating that the eut system is necessary for C. perfringens to utilize EA. The two-component regulatory system EutVW is needed to induce eut gene expression in response to EA whereas the global virulence regulator VirRS differentially controlled eut gene expression depending on glucose and EA availability. To assess the role of the eut system in vivo, an equal number of HN13 and HY1701 cells were injected into the right thigh muscles of mice. Mice infected with HY1701 showed fewer symptoms than those injected with HN13. The mortality rate of mice infected with HY1701 tended to be lower than for mice infected with HN13. In addition, in infected tissues from mice injected with a mixture of HN13 and HY1701, HN13 outnumbered HY1701. PCR screening demonstrated that C. perfringens isolated from gas gangrene and sporadic diarrhea cases carried both eut genes and the perfringolysin O gene (pfoA) as well as the phospholipase C gene (plc). However, pfoA was not detected in isolates from food poisoning patients and healthy volunteers. Culture supernatants prepared from HN13 grown in media containing 7.5% sheep red blood cells induced significantly higher eutB expression levels compared to those from plc- and/or pfoA-deletion mutants. Together, these results indicate that the eut system plays a nutritional role for C. perfringens during histolytic infection.

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Zusammenfassung. Zusammenfassung: Wir berichten über einen 69-jährigen Patienten, bei dem eine mikrochirurgische Dekompression und Diskektomie durchgeführt wurde. Im Verlauf entwickelte er stärkste Beinschmerzen ohne Ansprechen auf eine Schmerztherapie. Die durchgeführte Computertomografie zeigte grosse Lufteinschlüsse im retroperitonealen Raum von subdiaphragmal bis ins kleine Becken. Trotz sofortiger und radikaler chirurgischer Sanierung sowie antibiotischer Therapie starb der Patient noch im Operationssaal. Die vielzähligen intraoperativen Biopsien sowie alle Blutkulturen waren postmortem positiv für Clostridium perfringens.

Rethinking the role of alpha toxin in Clostridium perfringens-associated enteric diseases: a review on bovine necro-haemorrhagic enteritis

Bovine necro-haemorrhagic enteritis is an economically important disease caused by Clostridium perfringens type A strains. The disease mainly affects calves under intensive rearing conditions and is characterized by sudden death associated with small intestinal haemorrhage, necrosis and mucosal neutrophil infiltration. The common assumption that, when causing intestinal disease, C. perfringens relies upon specific, plasmid-encoded toxins, was recently challenged by the finding that alpha toxin, which is produced by all C. perfringens strains, is essential for necro-haemorrhagic enteritis. In addition to alpha toxin, other C. perfringens toxins and/or enzymes might contribute to the pathogenesis of necro-haemorrhagic enteritis. These additional virulence factors might contribute to breakdown of the protective mucus layer during initial stage of pathogenesis, after which alpha toxin, either or not in synergy with other toxins such as perfringolysin O, can act on the mucosal tissue. Furthermore, alpha toxin alone does not cause intestinal necrosis, indicating that other virulence factors might be needed to cause the extensive tissue necrosis observed in necro-haemorrhagic enteritis. This review summarizes recent research that has increased our understanding of the pathogenesis of bovine necro-haemorrhagic enteritis and provides information that is indispensable for the development of novel control strategies, including vaccines.

Lipidomic profile of GM95 cell death induced by Clostridium perfringens alpha-toxin

Clostridium perfringens alpha-toxin (ATX) is considered as a prototype of cytotoxic bacterial phospholipases C, and is the major virulence factor in C. perfringens-induced gas gangrene. It is known that, depending on the dose, ATX causes membrane disruption and cytolysis or only limited hydrolysis of its substrates. In the latter case, toxin activity leads to the unregulated generation of bioactive lipids that can ultimately induce cell death. We have characterized apoptosis and necrosis in highly ATX-sensitive, ganglioside-deficient cells exposed to different concentrations of ATX and we have studied the lipidomic profile of cells treated with ATX as compared to native cells to detect the main changes in the lipidomic profile and the possible involvement of lipid signals in cell death. ATX causes both apoptosis and necrosis, depending on dose and time. ATX activates cell death, stimulating the release of cytochrome C from mitochondria and the consequent activation of caspases-3. Moreover GM95 cells treated with ATX showed important lipidomic alterations, among them we detected a general decrease in several phospholipid species and important changes in lipids involved in programmed cell death e.g. ceramide. The data suggest two different mechanisms of cell death caused by ATX, one leading to (mainly saturated) glycerophospholipid hydrolysis related to an increase in diacylglycerols and associated to membrane damage and necrosis, and a second mechanism involving chiefly sphingomyelin hydrolysis and generation of proapoptotic lipidic mediators such as ceramide, N-acylethanolamine and saturated non-esterified fatty acids.

Animal models to study the pathogenesis of human and animal Clostridium perfringens infections

The most common animal models used to study Clostridium perfringens infections in humans and animals are reviewed here. The classical C. perfringens-mediated histotoxic disease of humans is clostridial myonecrosis or gas gangrene and the use of a mouse myonecrosis model coupled with genetic studies has contributed greatly to our understanding of disease pathogenesis. Similarly, the use of a chicken model has enhanced our understanding of type A-mediated necrotic enteritis in poultry and has led to the identification of NetB as the primary toxin involved in disease. C. perfringens type A food poisoning is a highly prevalent bacterial illness in the USA and elsewhere. Rabbits and mice are the species most commonly used to study the action of enterotoxin, the causative toxin. Other animal models used to study the effect of this toxin are rats, non-human primates, sheep and cattle. In rabbits and mice, CPE produces severe necrosis of the small intestinal epithelium along with fluid accumulation. C. perfringens type D infection has been studied by inoculating epsilon toxin (ETX) intravenously into mice, rats, sheep, goats and cattle, and by intraduodenal inoculation of whole cultures of this microorganism in mice, sheep, goats and cattle. Molecular Koch's postulates have been fulfilled for enterotoxigenic C. perfringens type A in rabbits and mice, for C. perfringens type A necrotic enteritis and gas gangrene in chickens and mice, respectively, for C. perfringens type C in mice, rabbits and goats, and for C. perfringens type D in mice, sheep and goats.

Immunization with recombinant bivalent chimera r-Cpae confers protection against alpha toxin and enterotoxin of Clostridium perfringens type A in murine model

Clostridium perfringens type A, an anaerobic pathogen is the most potent cause of soft tissue infections like gas gangrene and enteric diseases like food poisoning and enteritis. The disease manifestations are mediated via two important exotoxins, viz. myonecrotic alpha toxin (αC) and enterotoxin (CPE). In the present study, we synthesized a bivalent chimeric protein r-Cpae comprising C-terminal binding regions of αC and CPE using structural vaccinology rationale and assessed its protective efficacy against both alpha toxin (αC) and enterotoxin (CPE) respectively, in murine model. Active immunization of mice with r-Cpae generated high circulating serum IgG (systemic), significantly increased intestinal mucosal s-IgA antibody titres and resulted in substantial protection to the immunized animals (100% and 75% survival) with reduced tissue morbidity when administered with 5×LD(100) doses of αC (intramuscular) and CPE (intra-gastric gavage) respectively. Mouse RBCs and Caco-2 cells incubated with a mixture of anti-r-Cpae antibodies and αC and CPE respectively, illustrated significantly higher protection against the respective toxins. Passive immunization of mice with a similar mixture resulted in 91-100% survival at the end of the 15 days observation period while mice immunized with a concoction of sham sera and respective toxins died within 2-3 days. This work demonstrates the efficacy of the rationally designed r-Cpae chimeric protein as a potential sub unit vaccine candidate against αC and CPE of C. perfringens type A toxemia.

Type IV pili in Gram-positive bacteria

Type IV pili (T4P) are surface-exposed fibers that mediate many functions in bacteria, including locomotion, adherence to host cells, DNA uptake (competence), and protein secretion and that can act as nanowires carrying electric current. T4P are composed of a polymerized protein, pilin, and their assembly apparatuses share protein homologs with type II secretion systems in eubacteria and the flagella of archaea. T4P are found throughout Gram-negative bacterial families and have been studied most extensively in certain model Gram-negative species. Recently, it was discovered that T4P systems are also widespread among Gram-positive species, in particular the clostridia. Since Gram-positive and Gram-negative bacteria have many differences in cell wall architecture and other features, it is remarkable how similar the T4P core proteins are between these organisms, yet there are many key and interesting differences to be found as well. In this review, we compare the two T4P systems and identify and discuss the features they have in common and where they differ to provide a very broad-based view of T4P systems across all eubacterial species.

Multiple effects of Escherichia coli Nissle 1917 on growth, biofilm formation, and inflammation cytokines profile of Clostridium perfringens type A strain CP4

Clostridium perfringens is an important Gram-positive pathogen responsible for food poisoning, necrotic enteritis, gas gangrene, and even death. Escherichia coli Nissle 1917 (EcN) is a well-characterized probiotic strain with demonstrated benefits. In this study, we evaluated the effects of EcN on growth, toxin production, biofilm formation, and inflammatory cytokine responses of C. perfringens. In vitro co-culture experiments demonstrated that EcN inhibited growth, gas production, and toxin production (α-toxin and NetB) of C. perfringens in a dose-dependent manner. The growth inhibition effect was not observed when C. perfringens was incubated with EcN cell-free supernatants (CFSE), suggesting that growth inhibition was caused by nutrition competition during co-incubation. In vitro studies demonstrated that pre-incubation with EcN did not inhibit C. perfringens attachment to Caco-2 cells, but did reduce C. perfringens total number, toxin production, and cytotoxicity after 24 h. The similar growth inhibition results were also observed during the formation of C. perfringens biofilm. Finally, pre-incubation of EcN with RAW264.7 cells significantly decreased the production of inflammatory cytokines caused by the introduction of C. perfringens. Our results indicate that EcN can inhibit many of the pathological effects of C. perfringens in vitro conditions.

Opioid analgesics stop the development of clostridial gas gangrene

Gas gangrene is a potentially fatal disease that is primarily caused by the ubiquitous, anaerobic bacteria Clostridium perfringens and Clostridium septicum. Treatment is limited to antibiotic therapy, debridement of the infected tissue, and, in severe cases, amputation. The need for new treatment approaches is compelling. Opioid-based analgesics such as buprenorphine and morphine also have immunomodulatory properties, usually leading to faster disease progression. However, here we show that mice pretreated with buprenorphine and morphine do not die from clostridial myonecrosis. Treatment with buprenorphine after the onset of infection also arrested disease development. Protection against myonecrotic disease was specific to C. perfringens-mediated myonecrosis; buprenorphine did not protect against disease caused by C. septicum infection even though infections due to both species are very similar. These data provide the first evidence of a protective role for opioids during infection and suggest that new therapeutic strategies may be possible for the treatment of C. perfringens-mediated myonecrosis.

Gas gangrene in orthopaedic patients

Clostridial myonecrosis is most often seen in settings of trauma, surgery, malignancy, and other underlying immunocompromised conditions. Since 1953 cases of gas gangrene have been reported in orthopaedic patients including open fractures, closed fractures, and orthopaedic surgeries. We present a case of 55-year-old obese woman who developed rapidly progressive gas gangrene in her right leg accompanied by tibial plateau fracture without skin lacerations. She was diagnosed with clostridial myonecrosis and above-the-knee amputation was carried out. This patient made full recovery within three weeks of the initial episode. We identified a total of 50 cases of gas gangrene in orthopaedic patients. Several factors, if available, were analyzed for each case: age, cause of injury, fracture location, pathogen, and outcome. Based on our case report and the literature review, emergency clinicians should be aware of this severe and potentially fatal infectious disease and should not delay treatment or prompt orthopedic surgery consultation.

Induction of neurite-outgrowth in PC12 cells by alpha-toxin from Clostridium perfringens

Alpha-toxin-induced phosphorylation of PDK1 via the tyrosine kinase A (TrkA) receptor signaling pathway plays an important role in the activation of rabbit neutrophils. The relation between the toxin and TrkA, however, remains poorly understood. Here, we show that the toxin-induced phosphorylation of TrkA is closely related to the induction of neurite-outgrowth in PC12 cells. The toxin induced neurite-outgrowth and phosphorylation of TrkA in the cells in a dose-dependent manner. K252a, a TrkA inhibitor, and shRNA for TrkA inhibited the toxin-induced neurite-outgrowth, and phosphorylation of TrkA and ERK1/2. PD98059, an inhibitor of the ERK1/2 cascade, inhibited phosphorylation of ERK1/2 and the neurite-outgrowth induced by alpha-toxin. The wild-type toxin induced the formation of diacylglycerol, and neurite-outgrowth, but H148G, a variant toxin which binds to cell membranes and has lost the enzymatic activity did not. We demonstrated that the phosphorylation of TrkA through the phospholipid metabolism induced by the toxin synergistically play a key role in neurite-outgrowth.

Spezifische Infektionen

In diesem Kapitel wird auf die Infektionen eingegangen, die nicht im Rahmen der einzelnen Erkrankungsentitäten in den übrigen Kapiteln behandelt werden. Der Schwerpunkt liegt dabei auf den Infektionen bzw. Erregern, die auch dem Intensivmediziner häufiger begegnen können. Fragestellungen außerhalb dieser Gruppe sollten mit Hilfe spezieller Literatur beantwortet werden, Hilfestellungen geben auch die Verweise auf Webseiten am Ende des Kapitels.

Effect of erythromycin on biological activities induced by clostridium perfringens alpha-toxin

Clostridium perfringens alpha-toxin, an important agent of gas gangrene with inflammatory myopathies, possesses lethal, hemolytic, and necrotic activities. Here, we show that alpha-toxin-induced lethality in mice was inhibited by i.v. preadministration of erythromycin (ERM). Administration of ERM resulted in a drastic reduction in the release of tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, and IL-6 and systemic hemolysis induced by alpha-toxin, whereas the administration of kitasamycin did not. Furthermore, the lethality and systemic hemolysis caused by alpha-toxin were blocked by the preinjection of anti-TNF-alpha, but not the anti-IL-1beta- or anti-IL-6-antibody. In addition, TNF-alpha-deficient mice were resistant to alpha-toxin, indicating that TNF-alpha plays an important role in the lethality. ERM inhibited the toxin-induced release of TNF-alpha from neutrophils and phosphorylation of toropomyosin-related kinase receptor A (TrkA) and extracellular-regulated kinase (ERK) 1/2. Furthermore, K252a, a TrkA inhibitor, and PD98059 (2'-amino-3'-methoxyflavone), an ERK1/2 inhibitor, inhibited the toxin-induced release of TNF-alpha from neutrophils. The observation shows that the toxin-induced release of TNF-alpha is dependent on the activation of ERK/mitogen-activated protein kinase signal transduction via TrkA in neutrophils and that ERM specifically blocks the toxin-induced events through the activation of neutrophils.

Outcome of brain abscess by Clostridium perfringens

OBJECTIVE

Despite the aggressive infection of soft tissue caused by Clostridium perfringens (gas gangrene-necrotizing fasciitis), a brain abscess with this bacteria treated by early surgical excision, debridement of necrotic tissue, and antibiotic coverage may be expected to have a good recovery. Long-term follow-up has not been well established in this group of patients. We report this case to show the outcome at 3 years post surgical and antibiotic treatment for C. perfringens brain abscess and stress the need for urgent intervention to achieve good outcome. We also present a literature review of Clostridial brain abscesses since the 1960s.

CLINICAL PRESENTATION

A 53-year-old man was brought to the emergency room after having a witnessed seizure status postassault 3 days before admission. On presentation, he was febrile, disoriented, lethargic, and demonstrated right upper extremity weakness. A computed tomographic scan of the head showed a left frontoparietal depressed cranial fracture complicated with gas and intraparenchymal air fluid level cavity.

INTERVENTION

Emergent surgery for debridement and excision of necrotic tissue was performed. Empiric intravenous antibiotic therapy was started and penicillin G was added for 6 weeks after C. perfringens was demonstrated.

CONCLUSION

Despite the severe infection and effect of C. perfringens in soft tissues in the brain, it appears that emergent surgical debridement and antibiotic coverage will yield an excellent outcome for these patients.

Civilian gas gangrene: a clinical challenge

Gas gangrene due to clostridia infections is commonly seen in war injuries and is much less commonly seen in civilian life. When such problems do occur, they present a challenge to the surgeon due to the associated high morbidity and mortality associated. A case is presented where a patient developed gas gangrene in a limb consequent to trauma that had been treated surgically. It is vital to make a correct diagnosis at the earliest to limit disease progression and to avoid complications.

The role of neutrophils and monocytic cells in controlling the initiation of Clostridium perfringens gas gangrene

Clostridium perfringens is a common cause of the fatal disease gas gangrene (myonecrosis). Established gas gangrene is notable for a profound absence of neutrophils and monocytic cells (phagocytes), and it has been suggested that the bactericidal activities of these cells play an insignificant role in controlling the progression of the infection. However, large inocula of bacteria are needed to establish an infection in experimental animals, suggesting phagocytes may play a role in inhibiting the initiation of gangrene. Examination of tissue sections of mice infected with a lethal (1 x 10(9)) or sublethal (1 x 10(6)) inoculum of C. perfringens revealed that phagocyte infiltration in the first 3 h postinfection was inhibited with a lethal dose but not with a sublethal dose, indicating that exclusion of phagocytes begins very early in the infection cycle. Experiments in which mice were depleted of either circulating monocytes or neutrophils before infection with C. perfringens showed that monocytes play a role in inhibiting the onset of gas gangrene at intermediate inocula but, although neutrophils can slow the onset of the infection, they are not protective. These results suggest that treatments designed to increase monocyte infiltration and activate macrophages may lead to increased resistance to the initiation of gas gangrene.

A cellular deficiency of gangliosides causes hypersensitivity to Clostridium perfringens phospholipase C

Clostridium perfringens phospholipase C (Cp-PLC), also called alpha-toxin, is the major virulence factor in the pathogenesis of gas gangrene. Previously, a cellular UDP-Glc deficiency was related with a hypersensitivity to the cytotoxic effect of Cp-PLC. Because UDP-Glc is required in the synthesis of proteoglycans, N-linked glycoproteins, and glycosphingolipids, the role of these gly-coconjugates in the cellular sensitivity to Cp-PLC was studied. The cellular sensitivity to Cp-PLC was significantly enhanced by glycosphingolipid synthesis inhibitors, and a mutant cell line deficient in gangliosides was found to be hypersensitive to Cp-PLC. Gangliosides protected hypersensitive cells from the cytotoxic effect of Cp-PLC and prevented its membrane-disrupting effect on artificial membranes. Removal of sialic acids by C. perfringens sialidase increases the sensitivity of cultured cells to Cp-PLC and intramuscular co-injection of C. perfringens sialidase, and Cp-PLC in mice potentiates the myotoxic effect of the latter. This work demonstrated that a reduction in gangliosides renders cells more susceptible to the membrane damage caused by Cp-PLC and revealed a previously unrecognized synergism between Cp-PLC and C. perfringens sialidase, providing new insights toward understanding the pathogenesis of clostridial myonecrosis.

Fulminant massive gas gangrene caused by Clostridium perfringens

Clostridium perfringens (C.P) gas gangrene is one of the most fulminant infectious diseases. We encountered fulminant massive gas gangrene in a 56- year-old man with alcoholic liver cirrhosis. The patient died 14 hours after diagnosis of gas gangrene (54 hours after admission). Dramatic changes in abdominal CT imaging revealed development of a massive volume of gas in the intra-portal vein, retroperitoneum and abdominal subcutaneous tissue within 24 hours. We also proved C.P infection by immunohistological staining, leading to a diagnosis of C.P gas gangrene.

Effects of Clostridium perfringens alpha-toxin (PLC) and perfringolysin O (PFO) on cytotoxicity to macrophages, on escape from the phagosomes of macrophages, and on persistence of C. perfringens in host tissues

Clostridium perfringens is the most common cause of clostridial myonecrosis (gas gangrene). Polymorphonuclear cells (PMNs) appear to play only a minor role in preventing the onset of myonecrosis in a mouse animal model of the disease (unpublished results). However, the importance of macrophages in the host defense against C. perfringens infections is still unknown. Two membrane-active toxins produced by the anaerobic C. perfringens, alpha-toxin (PLC) and perfringolysin O (PFO), are thought to be important in the pathogenesis of gas gangrene and the lack of phagocytic cells at the site of infection. Therefore, C. perfringens mutants lacking PFO and PLC were examined for their relative cytotoxic effects on macrophages, their ability to escape the phagosome of macrophages, and their persistence in mouse tissues. C. perfringens survival in the presence of mouse peritoneal macrophages was dependent on both PFO and PLC. PFO was shown to be the primary mediator of C. perfringens-dependent cytotoxicity to macrophages. Escape of C. perfringens cells from phagosomes of macrophage-like J774-33 cells and mouse peritoneal macrophages was mediated by either PFO or PLC, although PFO seemed to play a more important role in escape from the phagosome in peritoneal macrophages. At lethal doses (10(9)) of bacteria only PLC was necessary for the onset of myonecrosis, while at sublethal doses (10(6)) both PFO and PLC were necessary for survival of C. perfringens in mouse muscle tissue. These results suggest PFO-mediated cytotoxicity toward macrophages and the ability to escape macrophage phagosomes may be important factors in the ability of C. perfringens to survive in host tissues when bacterial numbers are low relative to those of phagocytic cells, e.g., early in an infection.

Role of Clostridium perfringens phospholipase C in the pathogenesis of gas gangrene

Gas gangrene is an acute and devastating infection most frequently caused by Clostridium perfringens and characterized by severe myonecrosis, intravascular leukocyte accumulation, and significant thrombosis. Several lines of evidence indicate that C. perfringens phospholipase C (Cp-PLC), also called alpha-toxin, is the major virulence factor in this disease. This toxin is a Zn2+ metalloenzyme with lecithinase and sphingomyelinase activities. Its three dimensional structure shows two domains, an N-terminal domain which contains the active site, and a C-terminal domain required for the Ca2+dependent interaction with membranes. Cp-PLC displays several biological activities: it increases capillary permeability, induces platelet aggregation, hemolysis, myonecrosis, decreases cardiac contractility, and is lethal. Experiments with genetically engineered Cp-PLC variants have revealed that the sphingomyelinase activity and the C-terminal domain are required for toxicity. The myotoxicity of Cp-PLC is largely dependent on its membrane damaging effect. In addition, it has been suggested that the alterations in the blood flow induced by this toxin also contribute to muscle damage. In gas gangrene, Cp-PLC dysregulates transduction pathways in endothelial cells, platelets and neutrophils leading to the uncontrolled production of several intercellular mediators and adhesion molecules. Thus, Cp-PLC alters the traffic of neutrophils to the infected tissue and promotes thrombotic events, enhancing the conditions for anaerobic growth.

Clostridium perfringens alpha-toxin activates the sphingomyelin metabolism system in sheep erythrocytes

Clostridium perfringens alpha-toxin induces hemolysis of rabbit erythrocytes through the activation of glycerophospholipid metabolism. Sheep erythrocytes contain large amounts of sphingomyelin (SM) but not phosphatidylcholine. We investigated the relationship between the toxin-induced hemolysis and SM metabolic system in sheep erythrocytes. Alpha-toxin simultaneously induced hemolysis and a reduction in the levels of SM and formation of ceramide and sphingosine 1-phosphate (S1P). N-Oleoylethanolamine, a ceramidase inhibitor, inhibited the toxin-induced hemolysis and caused ceramide to accumulate in the toxin-treated cells. Furthermore, dl-threo-dihydrosphingosine and B-5354c, isolated from a novel marine bacterium, both sphingosine kinase inhibitors, blocked the toxin-induced hemolysis and production of S1P and caused sphingosine to accumulate. These observations suggest that the toxin-induced activation of the SM metabolic system is closely related to hemolysis. S1P potentiated the toxin-induced hemolysis of saponin-permeabilized erythrocytes but had no effect on that of intact cells. Preincubation of lysated sheep erythrocytes with pertussis toxin blocked the alpha-toxin-induced formation of ceramide from SM. In addition, incubation of C. botulinum C3 exoenzyme-treated lysates of sheep erythrocytes with alpha-toxin caused an accumulation of sphingosine and inhibition of the formation of S1P. These observations suggest that the alpha-toxin-induced hemolysis of sheep erythrocytes is dependent on the activation of the SM metabolic system through GTP-binding proteins, especially the formation of S1P.

Clostridium perfringens alpha-toxin induces rabbit neutrophil adhesion

Clostridium perfringens alpha-toxin, which is one of the main agents involved in the development of gas gangrene, stimulates O(2)(-)production in neutrophils. Exposure of rabbit neutrophils to the alpha-toxin induced firm adhesion of the cells to fibrinogen and fibronectin. Incubation of rabbit neutrophils and neutrophil lysates with alpha-toxin led to the production of diacylglycerol (DG) and L-alpha-phosphatidic acid (PA), respectively. The toxin-induced DG and PA formation preceded the toxin-induced adhesion of the neutrophils to fibrinogen and fibronectin, and the production of O(2)(-). Pertussis toxin inhibited the alpha-toxin-induced formation of PA, the adhesion of the neutrophils to fibrinogen and production. GTP gamma S stimulated the events induced by the alpha-toxin, whereas GDP beta S inhibited them. The alpha-toxin stimulated phosphorylation of a protein with a molecular mass of about 40 kDa. In addition, treatment of the cells with 1-oleoyl-2-acetyl-sn-glycerol (OAG) and phorbol-12,13-dibutyrate (PDBu) stimulated cell adhesion, production of and phosphorylation of the 40 kDa protein, but had no effect on the formation of PA. The events induced by the presence of OAG and PDBu were not inhibited by pertussis toxin. Protein kinase C inhibitors, H-7, staurosporine and chelerythrine, blocked alpha-toxin-induced adhesion, production of O(2)(-)and phosphorylation of the 40 kDa protein. These observations suggested that alpha-toxin-stimulated adhesion to the matrix and production were due to the formation of DG, through activation of phospholipid metabolism by a pertussis-toxin-sensitive GTP-binding protein, followed by activation of protein kinase C by DG.