Laboratory aspects of "Mycobacterium genavense," a proposed species isolated from AIDS patients

Abstract

Mycobacterium genavense" is a proposed new species recently reported to cause disseminated infections in 18 patients with AIDS in Europe. We have recovered "M. genavense" as slowly growing fastidious mycobacteria in blood cultures of seven patients with AIDS. In the original studies of "M. genavense," the fastidious organism grew only in BACTEC 13A vials. The Seattle, Washington, isolates of "M. genavense" also failed to grow when subcultured from 13A vials to routine solid media, but dysgonic colonies were produced on Middlebrook 7H11 agar supplemented with mycobactin J. The mycolic acid pattern of patients' isolates closely resembled that of the type strain of Mycobacterium simiae when analyzed by one-and two-dimensional thin-layer chromatography and by high-performance liquid chromatography. Whole-cell fatty acid analyses by gas-liquid chromatography distinguished the isolates from M. simiae but misidentified them as Mycobacterium fortuitum. Sequence determinations of the hypervariable regions of the 16S rRNA gene indicate that these organisms belong to the recently proposed new species "M. genavense." Growth from Middlebrook 7H11 agar supplemented with mycobactin J consistently yielded positive tests for catalase (semiquantitative and at 68°C), pyrazinamidase, and urease which enable mycobacteriology laboratories to presumptively identify "M. genavense" without nucleic acid analyses. The failure of "M. genavense" to grow on conventional mycobacterial solid media suggests that mycobacterial blood cultures should include a broth medium incubated for at least 8 weeks.

Hyperammonemia in Generalized Mycobacterium genavense Infection after Renal Transplantation

“…Direct hepatotoxicity of M. genavense cannot be ruled out. However, a possible clue may lie in the ability of M. genavense to produce urease (7,8). The amount of ammonia produced depends on the number of urease producing bacteria and the availability of its substrate, urea, at the same site.…”

Mycobacterium genavenseinfection in two aged ferrets with conjunctival lesions

“…More recently, however, M genavense strains have been isolated using enriched liquid media and subcultured onto solid media supplemented with mycobactin J, although growth is typically poor and extremely slow. 2,4,5,16,17 This preliminary work was extended in further investigations that are summarised in the taxonomic description of Böttger and colleagues: 2 M genavense can be differentiated from other slow-growing mycobacteria by its fastidious growth, a preference for broth media, inability to grow on standard (unsupplemented) solid media used for isolation of mycobacteria and its characteristic morphological appearance (minute acid-fast coccobacilli). Enzymatic and biochemical characteristics of this organism have been published and have enabled it to be distinguished from M avium, M malmoense, M ulcerans and M haemophilum.…”

“…Recently, a new species of mycobacteria, named M genavense, has been identified as a cause of disseminated disease in human patients with AIDS. [1][2][3][4][5][6][7] Histologically, M genavense infections are characterised by masses of foamy macrophages and, depending on the immunological reactivity of the host, by ill-formed granulomas in various tissues. 8 Mycobacteriosis due to M genavense has also been well described as a potentially fatal condition in various species of birds [9][10][11][12][13] and this species appears to be an important avian pathogen, particularly in Europe.…”

The detection of mycobacteria in blood cultures using the Bactec system: 6 weeks versus 12 weeks of incubation? routine terminal Ziehl—Neelsen?

“…Nevertheless, as some slow-growing mycobacteria have only recently been described [4,14,15], a six-week incubation could be insuficient to detect them by culture. Based on their experience with M. genavense, Coyle et a1 proposed an 8-week incubation for all blood cultures [5]. Our study effectively showed a significantly lower level of detection of M. genavense (37%) than of MAC (96%) after 6 weeks of incubation.…”