Phenotypic consequences of red–white colony type variation in Mycobacterium avium

Abstract

Mycobacterium avium undergoes reversible morphotypic switching between the virulent transparent colony type and the less virulent opaque colony type. A new morphotypic switch in M. avium, termed red-white, that becomes visible when opaque colonies of clinical isolates are grown on agar media containing Congo red, was recently described. White opaque (WO) variants were found to be more resistant to multiple antibiotics than were red opaque (RO) variants. The present paper reports that transparent derivatives of RO and WO clones retain the differential Congo red binding properties of their opaque parents, indicating that the opaque-transparent switch operates independently of the red-white switch. White transparent variants were more resistant to clarithromycin and rifampin in vitro, and better able to survive within human macrophages, than their red transparent counterparts. Neither red nor white variants were markedly favoured during growth in vitro ; however, red variants were better able to spread on soft agar (sliding motility), a potential selective advantage under some environmental circumstances. White-to-red switching was frequently observed in vitro and was accompanied by decreased antibiotic resistance and increased motility. Red-to-white switching has yet to be observed in vitro, indicating that the red morphotype is very stable. Significantly, some widely studied laboratory reference strains of M. avium, including strain 2151 and the genome sequence strain 104, are stable red clones. These strains are intrinsically antibiotic resistant and virulent in animal models, but they may not express genes encoding the elevated levels of antibiotic resistance and intracellular survival observed in white variants.

Surface Spreading Motility Shown by a Group of Phylogenetically Related, Rapidly Growing Pigmented Mycobacteria Suggests that Motility Is a Common Property of Mycobacterial Species but Is Restricted to Smooth Colonies

“…The rough strain, completely devoid of GPLs, did not spread, while another rough strain which was able to synthesize incomplete GPLs produced smaller spreading areas. In addition to these results, Cangelosi et al have reported that when M. avium grows in agar media containing Congo red, new phenotypic variations can be detected since smooth strains give pink, red, and white colonies (4). These authors detected that red variants spread more aggressively than white ones, but no data about the content of GPLs or other compounds responsible for the different behaviors between the two morphotypes were provided.…”

Growth, Congo Red Agar Colony Morphotypes and Antibiotic Susceptibility Testing of Mycobacterium avium subspecies paratuberculosis

“…avium has been shown to undergo red-white morphotypic switching when grown on agar media containing Congo Red. 28,34 White opaque variants were found to be more resistant to multiple antibiotics than red opaque variants.…”

“…Transparent variants of M. avium subsp. avium predominate in clinical samples, 28 whereas opaque variants in general have been shown to be better adapted for growth in the laboratory and tend to predominate after multiple passages. [29][30][31][32][33] In addition, M. avium subsp.…”

Avaliação da virulência de isolados suínos de Mycobacterium avium no Brasil caracterizados pelo método de RFLP

“…As micobactérias, bactérias do gênero Mycobacterium, são bacilos álcool-ácido resistentes (BAAR), de crescimento lento (GYLES;THOEN, 1986;TIMONEY et al, 1988;INDERLIED et al, 1993;FALKINHAM III, 1996), com 0,2 a 0,7 μm de largura e um a 10 μm de comprimento, aeróbios, imóveis, não esporulados (HOLT et al, 1994) e não pigmentados que têm crescimento otimizado em pH 5 a 5,5 em microaerofilia, em águas salobras ou não (FALKINHAM III, 1996) e são intrinsecamente resistentes a drogas (INDERLIED et al, 1993;REDDY, 1998;CANGELOSI et al, 2001;COSMA et al, 2003) e a vários desinfetantes químicos (EVERITT et al, 1982 RICHTER et al, 2003;CHIMARA et al, 2004).…”

“…A variação reversível e transitória na morfologia das colônias de M. avium tem importância significante para a virulência, patogenia e susceptibilidade a antibióticos desses microrganismos (REDDY et al, 1996). As variantes lisas opacas normalmente são isoladas do ambiente e crescem bem em meios de cultura (REDDY et al, 1996;CANGELOSI et al, 2001); as lisas transparentes, mais virulentas que as lisas opacas (REDDY et al, 1996;REDDY, 1998;CANGELOSI et al, 2001), predominam em amostras clínicas, crescem melhor em macrófagos e modelos animais (CANGELOSI et al, 2001), colonizam eficientemente as mucosas, aderem facilmente às células epiteliais e são mais resistentes aos antibióticos (REDDY et al, 1996;REDDY, 1998;CANGELOSI et al, 2001); as intermediárias podem sobreviver e prosperar sob condições adversas. As variantes rugosas podem surgir após passagem in vitro, mas são desconhecidas as condições que favorecem seu crescimento (CANGELOSI et al, 2001).…”