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At autopsy, about one third of AIDS patients with MTB are found to have succumbed to
this infection, usually from extensive pulmonary involvement.[417] Prophylaxis against MTB
infection can be considered for patients with a positive tuberculin skin test (induration >5 mm)
who have never been treated for tuberculosis, and for patients with recent exposure to someone
with active tuberculosis. Isoniazid plus pyridoxine, or rifampin plus pyrazinamide, administered
for 9 months, are the regimens of choice.[208]

MYCOBACTERIUM FORTUITUM.-- Mycobacterium fortuitum occurs less commonly
than either MTB or MAC in AIDS. This organism is widely found in the environment but is an
infrequent human pathogen. In culture M fortuitum is a rapid grower. In persons who are
immunocompetent, infections of surgical sites, soft tissues, skin, and lung can occur but are
typically not life threatening. In immunocompromised persons, M fortuitum infections are more
disseminated and severe, with multiple skin lesions and deep organ involvement. In persons
with HIV infection, M fortuitum occurs late in the course, with CD4 counts typically below
100/µL. Cervical lymphadenitis is the most common initial sign. Microscopically, a mixture of
granulomatous and acute suppurative inflammation characterizes the lesions. The long,
filamentous acid-fast bacilli may not be numerous and may stain poorly with standard special
stains such as Ziehl-Neelsen, Kinyoun, or auramine. They may be confused with Nocardia
species, though M fortuitum organisms tend to have shorter, blunter branches that extend at right
angles from their origin, compared to Nocardia. A response to antibiotic therapy with agents
such as amikacin and ciprofloxacin is generally seen.[443]

MYCOBACTERIUM XENOPI.-- Mycobacterium xenopi is most likely to be a colonizing
agent in persons with AIDS in regions where this organism is endemic and considered to be a
commensal or environmental contaminant where it can be recovered from water sources. In
most cases, it does not require specific antimicrobial therapy.[444] However, in some cases it
can cause pneumonia and/or septicemia in persons with AIDS. M xenopi infection may be
accompanied by cough, chronic fever, and wasting syndrome. Disseminated infections are rare.
M xenopi demonstrates reduced susceptibility to anti-tuberculous drugs, and the response to
treatment is variable.[445]

OTHER MYCOBACTERIA.-- Infections with Mycobacterium africanum,
Mycobacterium kansasii, Mycobacterium scrofulaceum, or Mycobacterium gordonae may also
occur in AIDS. These infections both clinically and pathologically are more likely to resemble
MTB infection than MAC infection.[428,446] The specific diagnosis depends upon culture of
tissues or body fluids, but morphologically M kansasii organisms have a long, curved or folded,
and beaded appearance (barber pole) on acid fast stain. M avium complex (MAC) organisms are
short, thick, and beaded. M tuberculosis organisms are not as thick or beaded as those of MAC.
Mycobacterium scrofulaceum organisms are very short and delicate.[447]
Mycobacterium haemophilum infection, first described in 1978, produces disseminated
lesions, most often as cutaneous lesions or as pulmonary infiltrates or nodules. HIV-infected
persons are at risk when CD4 counts are below 100 cells/microliter. The skin lesions begin as
erythematous papules or nodules that become suppurative, with painful draining ulcers. Cysts,
scaly plaques, or focal panniculitis occur less commonly. M haemophilum lesions typically
occur on the extremities overlying the joints because of enhanced growth of the organisms at
lower temperatures, typically 30 to 32 C. The organism is very fastidious and slow growing in