Hi.
What are the virulence genes in the environmental mycobacteria? Does anyone investigate about virulence genes in the mycobacteria? I want to study about evaluation of the virulence genes in the environmental mycobacteria, but I cannot find them.
Some of the virulence factors are common to both M. tuberculosis complex and some environmental mycobacteria such as
1. The intracellular location: All mycobacteria have the potential to reside inside phagocytic cells where they are protected from antibodies, complement and other components of the immune defence system.
2. Neutralisation of free radicals: To survive within phagocytes these bacteria must have the ability to block the host cell capacity to form toxic oxygen radicals or neutralise them as they are formed.
3. Mycobacteria have a lipid rich outer cell wall. Some of these lipids may have the ability to stimulate interleukin 1 (IL-1) and tumour necrosis factor alpha (TNF-alpha) release form macrophages that contribute to the symptoms of the illness.
4. Specific virulence genes have been mapped in a number of atypical mycobacterial species including M. abscessus and M. smegmatis which are considered to be analogues of Mycobacterium tuberculosis complex.
5. This amazing table from Ripoll F et al 2009 gives detailed comparison of the virulence factors between the three species.
(a) For proteins belonging to the PE/PPE and ESX families, homologs of M. tuberculosis LeuD, TrpD, ProC and PurC (amino acid and purine biosynthesis) present in both M. abscessus and M. smegmatis
(b) A protein homologous to IipB (Rv1478) is also present in both M. abscessus (MAB_2727c) and M. smegmatis (Msmeg_3156)
(c) A protein homologous to IrtB (Rv1349) is also present in both M. abscessus (MAB_2261c) and M. smegmatis (Msmeg_6553)
(d) There are three other proteins homologous to Rv3763 in M. abscessus: MAB_ 2379 (51% identity), MAB_3261c (35%) and MAB_4074c (34%)
(e) Presence of homologs most similar to non mycobacterial proteins
(f) A cluster similar to the narGHIJ cluster encoding the M. tuberculosis nitrate reductase is present in M. smegmatis, but not M. abscessus.
(g) There are three phospholipases C encoded in H37Rv: PlcA (Rv2351c), PlcB (Rv2350c) and PlcC (Rv2349c)
(h) Homologs of RpfB (Rv1009) and RpfC (Rv1884c) are present in both M. abscessus (MAB_1130 and MAB_4080c, respectively) and M. smegmatis (Msmeg_5439 and Msmeg_4640, respectively).
(i) Other M. tuberculosis sigma factors involved in virulence (SigA, SigD, SigE, SigH) have homologs in both M. abscessus and M. smegmatis.
Best wishes
Dr Sayed S Bukhari FRCPath
Consultant in Infection
University Hospitals of Leicester NHS Trust
Leicester LE1 5WW
England
I agree with the previous answer,
And to add some other information, since lot of mycobacteria strains survive (or live?) inside amoeba, after phagocytosis, in the environment (for example in water, see our publications) they probably have lot of characteristics who can be described as “virulence factors”.
Amoeba is like a training field for mycobacteria...
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