Clostridium novyi

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Clostridium novyi
Scientific classification
Kingdom: Bacteria
Phylum: Firmicutes
Class: Clostridia
Order: Clostridiales
Family: Clostridiaceae
Genus: Clostridium
Species: C. novyi
Binomial name
Clostridium novyi

Clostridium novyi (oedematiens) a Gram-positive, endospore- forming, obligate anaerobic bacteria of the class clostridia. It is ubiquitous, being found in the soil and faeces. It is pathogenic, causing a wide variety of diseases in man and animals. It comes in three types, labelled A, B, and a non-pathogenic type C distinguished by the range of toxins they produce. Some authors include Clostridium haemolyticum as Clostridium novyi type D. C novyi is closely related to Clostridium botulinum types C and D as Yoshimasa Sasaki et al. have demonstrated by 16S rDNA sequence analysis.[1] The PAGE analysis reported in ref 1 seems to indicate that the differences between these closely related types is a matter of gene expression rather than major genetic differences.[original research?] For example type C can be induced to produce the lethal alpha-toxin.

Growth in culture proceeds through 3 stages: Initial growth wherein no toxin is produced; vigorous growth wherein toxin is produced; and spore formation wherein endospores are formed and toxin production decreases. It is suggested that type C may be type B that forms spores more readily so does not go through the toxin-production stage.

Isolating and identifying C novyi is difficult due to its extreme anaerobic nature. Commercial kits may not be adequate.[2][3]

It is also fastidious and difficult to culture, requiring the presence of thiols.[4]

Toxins[edit]

The toxins are designated by Greek letters. The toxins normally produced by the various types are shown in table 1[5]
Table 1
C novyi type Toxins
A alpha, gamma, delta, epsilon
B alpha, beta, zeta
C gamma

The alpha-toxin of Clostridium botulinum types C and D, is similar to the C novyi beta-toxin. The A and B toxins of Clostridium difficile show homology with the alpha-toxin of C novyi as does the lethal toxin of clostridium sordellii.[6]

Alpha toxin[edit]

The alpha-toxin is characterised as lethal and necrotizing.

The type A alpha-toxin is oedematising.[7] It acts by causing morphological changes to all cell types especially endothelial cells by inhibition of signal transduction pathways,[8] resulting in the breakdown of cytoskeletal structures.[9] The cells of the microvascular system become spherical and the attachments to neighbouring cells are reduced to thin strings. This results in leakage from the capillaries, leading to oedema. The threshold concentration for this action to occur is 5 ng/ml (5 parts per billion) with 50% of cells rounded at 50 ng/ml.

The duodenum is particularly sensitive to the toxin. Injection into dogs resulted in extreme oedema of the submucosal tissues of the duodenum while leaving the stomach uninjured. Injection into the eye resulted in lesions similar to flame haemorrhages found in diabetic retinopathy.[7]
The toxin is a large 250-kDa protein the active part of which is the NH2-terminal 551 amino acid fragment.[10] Alpha-toxins are glycosyltransferases, modifying and thereby inactivating different members of the Rho and Ras subfamily of small GTP-binding proteins.[11][12][13] C novyi type A alpha-toxin is unique in using UDP-N-acetylglucosamine rather than UDP-glucose as a substrate.[14]

Beta-Toxin[edit]

The beta-toxin is characterised as haemolytic, necrotizing lecithinase.

Gamma-Toxin[edit]

The gamma-toxin is characterised as haemolytic, lecithinase.

Delta-Toxin[edit]

The delta-toxin is characterised as oxygen labile haemolysin.

Epsilon-Toxin[edit]

The epsilon-toxin is characterised as lecithino-vitelin and thought to be responsible for the pearly layer found in cultures.

Zeta-Toxin[edit]

The zeta-toxin is characterised as haemolysin.

Human diseases[edit]

The type and severity of the disease caused depends on penetration of the tissues. The epithelium of the alimentary tract, in general, provides an effective barrier to penetration. However, spores may escape from the gut and lodge in any part of the body and result in spontaneous infection should local anaerobic conditions occur.

Tissue penetration[edit]

Wound infection by C novyi and many other clostridium species cause gas gangrene[15] Spontaneous infection is mostly associated with predisposing factors of hematologic or colorectal malignancies and with diabetes mellitus,[16] although Gram-negative organisms, including Escherichia coli, may lead to a gas gangrene-like syndrome in diabetic patients. This presents with cellulitis and crepitus, and may be mistaken for gas gangrene.[17] Spontaneous, nontraumatic, or intrinsic infections from a bowel source have been increasingly reported recently.[18]

C novyi has been implicated in mortality among injecting illegal drug users.[19][20]

Epithelial infections[edit]

Symptoms are often non-specific including, colitis[citation needed], oedematous duodenitis[citation needed], and fever with somnolence[citation needed].

Testing is problematical with figures presented by McLauchlin and Brazier [cited above] suggesting a false negative rate of about 40% under ideal conditions. Only positive results may be regarded as reliable. In the absence of a positive test, C. novyi type A may be inferred from characterisation by clinical observation, table 2.

Table 2
Observation Comment
Oedema Especially if extreme with rapid onset. In view of the sensitivity of the duodenum to the alpha-toxin, oedematous duodenum is always suspect.
Anaerobic Infection occurs at an anaerobic site such as the gut or salivary gland. It may also occur at a site temporarily made anaerobic by occlusion and maintained in this state by oedema.
Gram positive If penicillin causes remission of oedema then a Gram positive organism is the causative agent.

Chronic infection leading to leaky capillaries may also cause retinal haemorrhages and oedema in the lower extremities leading to necrosis and gangrene. Leaky nephrons may compromise the ability of kidneys to concentrate urine leading to frequent urination and dehydration.

Animal diseases[edit]

Gas gangrene: Infectious necrotic hepatitis (Black disease)[21]

Clostridium novyi-NT - Potential Therapeutic Uses in Cancers[edit]

In general, solid tumors are characterized by hypoxic areas in the tumor core. This is due to irregular and insufficient tumor vessel growth and heavy metabolic demands of the surrounding tumor cells.

Much of the core within a tumor core is necrotic, however some live tumor cells reside there – often in a quiescent state. These cells are often quite resistant to standard treatments such as radiotherapy (which relies heavily on DNA damage from radiation-induced oxygen-based free radical species) and chemotherapy which has poor access to the poorly perfused tumor core and a weak effect on non-dividing quiescent cells. As a result, cells in the hypoxic tumor core often survive treatment and become a source for subsequent cancer recurrence and spread.

Clostridium novyi-NT is a genetically modified form of Clostridium novyi that lacks a major toxin. Because C. novyi-NT is a strict anaerobe; it grows selectively in hypoxic tumor cores; elsewhere, it tends to exist as inactive spores. C. novyi-NT activates and effectively infects and lyses tumor cells in hypoxic tumor cores.

Early work on use of strict anaerobes in tumors goes back several decades. Strongly lytic, infective bacteria tended to be the most effective (however, most earlier research was abandoned due to the risk of toxicity from release of toxins).

One major limitation on the use of C. novyi-NT or other strict anaerobes in cancer treatment is that it tends to affect only the hypoxic tumor core, leaving the active cancer cells in the well-perfused tumor rim alive and intact.

It is thus not surprising that this has led to attempts to combine C. novyi-NT with traditional chemotherapy and/or with radiotherapy (both of which tend to be preferentially effective within the well-perfused tumor rim).

A variety of other clever approaches are under continuing investigation, these include :

  • "RAIT" (radioactive immunotherapy) – Radioactive monoclonal antibodies have been used as a means of targeting radiotherapy to tumors using common tumor antigens such as CEA). This approach could be used to target antigenic epitopes on C. novyi-NT itself, using the tumor-localized vegetative forms to deliver radiation to specifically tumor cells thus sparing more healthy tissue. This could be viewed as a form of molecular brachytherapy).
  • Prodrug converting enzymes can be produced by further genetic modification of C. novyi-NT causing the activation of chemotherapeutic prodrugs at the tumor site.
  • Anti-cancer drugs may be packaged in liposomes and then specifically released at the tumor site by tumor-localized C. novyi-NT bacteria, improving the effectiveness and safety of the therapy. This approach exposes the tumors to a six times greater concentration of chemotherapy compared to the liposomal drug alone, without increasing the levels of chemotherapy in healthy tissue. Drug release from the liposomes is mediated by an enzyme secreted by C. novyi-NT called liposomase.[22]
  • Other chemotherapy delivery technologies using minicells may be used to more specifically deliver chemotheraputic agents to the site of the remaining tumor rim. This could be achieved for example through the conjugation of bispecific antibodies targeted to epitopes on C. novyi-NT. Minicells are a very promising technology in themselves that use bispecific antibodies to dramatically increase the delivery specificity of chemotheraputic drugs by several orders of magnitude, potentially allowing effective chemotheraputic dosages that are hundreds of times the current tolerated systemic levels. Nevertheless, minicells are limited by perfusion access to tumor cores – so combination with C. novyi-NT may provide an excellent complement.
  • Various genetic modifications to C. novyi-NT seek to further stimulate local inflammation and immune response to boost the immunogenicity of the tumor rim. Many of these approaches secrete immunomodulators/cytokines; others try to use siRNA or other approaches to further shut down tumor cells.
  • The hypoxic core can be made temporarily wider by use of drugs like dolastatin, or by temporarily reducing oxygenation. This then allows C. novyi-NT to lyse more of the tumor.
  • Most approaches have used single administrations of C. novyi-NT, but it may be useful to give repeated injections to promote an immune response in the area of the active bacteria (the former tumor core and adjacent rim) to create a "bystander effect" on the nearby tumor cells (e.g., boosting the bystander immune response to the tumor cells).[23] It may also help slow relapses by colonizing metastases early after they became large enough to have a significantly sized hypoxic core.

In summary, C. novyi-NT is a promising new component to the treatment of solid tumors - effectively targeting the hypoxic tumor cores that were a source of ongoing treatment resistance and recurrence. It is likely that additional modalities will be needed to treat the well-perfused tumor rims.

Further reading[edit]

References[edit]

  1. ^ Sasaki Y, Takikawa N, Kojima A, Norimatsu M, Suzuki S, Tamura Y (May 2001). "Phylogenetic positions of Clostridium novyi and Clostridium haemolyticum based on 16S rDNA sequences". International Journal of Systematic and Evolutionary Microbiology 51 (Pt 3): 901–4. doi:10.1099/00207713-51-3-901. PMID 11411712. 
  2. ^ Brazier JS, Duerden BI, Hall V, et al. (November 2002). "Isolation and identification of Clostridium spp. from infections associated with the injection of drugs: experiences of a microbiological investigation team". Journal of Medical Microbiology 51 (11): 985–9. PMID 12448683. 
  3. ^ "Identification of Clostridium species". National Standard Methods. BSOP ID8 Issue 3. Health Protection Agency. July 2008. 
  4. ^ Moore WB (October 1968). "Solidified media suitable for the cultivation of Clostridium novyi type B". Journal of General Microbiology 53 (3): 415–23. PMID 5721591. 
  5. ^ Oakley, C. L.; Warrack, G. Harriet; Clarke, Patricia H. (1947). "The Toxins of Clostridium oedematiens (Cl. novyi)". Journal of General Microbiology 1 (1): 91–107. doi:10.1099/00221287-1-1-91. PMID 20238541. 
  6. ^ Hofmann F, Herrmann A, Habermann E, von Eichel-Streiber C (June 1995). "Sequencing and analysis of the gene encoding the alpha-toxin of Clostridium novyi proves its homology to toxins A and B of Clostridium difficile". Molecular & General Genetics 247 (6): 670–9. doi:10.1007/BF00290398. PMID 7616958. 
  7. ^ a b Bette P, Frevert J, Mauler F, Suttorp N, Habermann E (August 1989). "Pharmacological and biochemical studies of cytotoxicity of Clostridium novyi type A alpha-toxin". Infection and Immunity 57 (8): 2507–13. PMC 313478. PMID 2744858. 
  8. ^ Schmidt M, Rümenapp U, Bienek C, Keller J, von Eichel-Streiber C, Jakobs KH (February 1996). "Inhibition of receptor signaling to phospholipase D by Clostridium difficile toxin B. Role of Rho proteins". The Journal of Biological Chemistry 271 (5): 2422–6. doi:10.1074/jbc.271.5.2422. PMID 8576201. 
  9. ^ Müller H, von Eichel-Streiber C, Habermann E (July 1992). "Morphological changes of cultured endothelial cells after microinjection of toxins that act on the cytoskeleton". Infection and Immunity 60 (7): 3007–10. PMC 257268. PMID 1612768. 
  10. ^ Busch C, Schömig K, Hofmann F, Aktories K (November 2000). "Characterization of the Catalytic Domain of Clostridium novyi Alpha-Toxin". Infection and Immunity 68 (11): 6378–83. doi:10.1128/IAI.68.11.6378-6383.2000. PMC 97722. PMID 11035748. 
  11. ^ Just I, Selzer J, Hofmann F, Green GA, Aktories K (April 1996). "Inactivation of Ras by Clostridium sordellii lethal toxin-catalyzed glucosylation". The Journal of Biological Chemistry 271 (17): 10149–53. doi:10.1074/jbc.271.17.10149. PMID 8626575. 
  12. ^ Just I, Selzer J, Wilm M, von Eichel-Streiber C, Mann M, Aktories K (June 1995). "Glucosylation of Rho proteins by Clostridium difficile toxin B". Nature 375 (6531): 500–3. doi:10.1038/375500a0. PMID 7777059. 
  13. ^ Just I, Wilm M, Selzer J, et al. (June 1995). "The enterotoxin from Clostridium difficile (ToxA) monoglucosylates the Rho proteins". The Journal of Biological Chemistry 270 (23): 13932–6. doi:10.1074/jbc.270.23.13932. PMID 7775453. 
  14. ^ Selzer J, Hofmann F, Rex G, et al. (October 1996). "Clostridium novyi alpha-toxin-catalyzed incorporation of GlcNAc into Rho subfamily proteins". The Journal of Biological Chemistry 271 (41): 25173–7. doi:10.1074/jbc.271.41.25173. PMID 8810274. 
  15. ^ Hatheway CL (January 1990). "Toxigenic clostridia". Clinical Microbiology Reviews 3 (1): 66–98. PMC 358141. PMID 2404569. 
  16. ^ Nagano N, Isomine S, Kato H, et al. (April 2008). "Human Fulminant Gas Gangrene Caused by Clostridium chauvoei". Journal of Clinical Microbiology 46 (4): 1545–7. doi:10.1128/JCM.01895-07. PMC 2292918. PMID 18256217. 
  17. ^ "Necrotising infections". The British Society for Antimicrobial Chemotherapy. 
  18. ^ Kornbluth AA, Danzig JB, Bernstein LH (January 1989). "Clostridium septicum infection and associated malignancy. Report of 2 cases and review of the literature". Medicine 68 (1): 30–7. PMID 2642585. 
  19. ^ Finn SP, Leen E, English L, O'Briain DS (November 2003). "Autopsy findings in an outbreak of severe systemic illness in heroin users following injection site inflammation: an effect of Clostridium novyi exotoxin?". Archives of Pathology & Laboratory Medicine 127 (11): 1465–70. doi:10.1043/1543-2165(2003)127<1465:AFIAOO>2.0.CO;2. PMID 14567722. 
  20. ^ McLauchlin J, Salmon JE, Ahmed S, et al. (November 2002). "Amplified fragment length polymorphism (AFLP) analysis of Clostridium novyi, C. perfringens and Bacillus cereus isolated from injecting drug users during 2000". Journal of Medical Microbiology 51 (11): 990–1000. PMID 12448684. 
  21. ^ Kahn, Cynthia M., ed. (2005). "Infectious Necrotic Hepatitis (Black disease)". The Merck Veterinary Manual (9th ed.). Whitehouse Station, New Jersey: Merck & Co. ISBN 978-0-911910-50-6. OCLC 57355058. 
  22. ^ Cheong I, Huang X, Bettegowda C, et al. (November 2006). "A bacterial protein enhances the release and efficacy of liposomal cancer drugs". Science 314(5803):1308-11. PMID 17124324
  23. ^ Agrawal N, Bettegowda C, Cheong I, et al. (October 2004). "Bacteriolytic therapy can generate a potent immune response against experimental tumors.". Proc Natl Acad Sci U S A 101(42):15172-7. PMID 15471990