Infections caused by Mycobacterium avium complex in immunocompromised patients: diagnosis by blood culture and fecal examination, antimicrobial susceptibility tests, and morphological and seroagglutination characteristics

Abstract

The Mycobacterium avium complex, only rarely described as an invasive pathogen in humans, has recently been reported to frequently cause disseminated disease in patients with the acquired immune deficiency syndrome. Between February 1981 and February 1984 at Memorial Sloan-Kettering Cancer Center, 30 patients with acquired immune deficiency syndrome, 3 patients with leukemia, and 2 patients with congenital severe combined immunodeficiency syndrome developed disseminated M. avium complex infection. Mycobacteria were often found in multiple sites both antemortem and postmortem. Blood cultures were a reliable method for detecting disseminated infection, and the new lysis blood culture systems provided an efficient technique for determining the number of organisms per milliliter of blood. Acid-fast stains and cultures of fecal specimens were also helpful in diagnosing infection. Most of the mycobacteria were serovar 4 (77%), and most (86%) produced a deep yellow pigment. All isolates were susceptible to standard concentrations of clofazimine, cycloserine,and ansamycin, but tended to be resistant to isoniazid, streptomycin, ethambutol, ethionamide, and rifampin.

Therapeutic Drug Monitoring in Patients Coinfected with Human Immunodeficiency Virus and Disseminated Mycobacterium avium Complex

“…The minimum inhibitory concentration (MIC) for MAC is typically less than 2 mcg/mL; however, this represents a much higher MIC than that of Mycobacterium tuberculosis, which is typically sensitive at a concentration of 0.06mcg/mL. 17 Previous studies have documented that rifabutin when used in combination with a macrolide and ethambutol is not associated with improved clearance of MAC from blood cultures, rather its use may prevent the development of resistance to macrolides. 5, 6 The Tuberculosis Trials Consortium documented an increase in the development of rifabutin resistance and relapse of Mycobacterium tuberculosis when peak concentrations of rifabutin were less than 0.45mcg/mL.…”

Update on detection of bacteremia and fungemia.

“…In contrast, much more extensive information is available about the frequency of bacteremia in patients with MAC infection. Occasional patients with a variety of immunosuppressive conditions including leukemias, severe combined immunodeficiency syndrome, steroid therapy, cytotoxic chemotherapy, multiple myeloma, other nonhematologic malignancies, diabetes mellitus, anthrasilicosis, asthma, and other infections appear to be at increased risk for MAC bacteremia (68,73,84). Despite these possible associations, the vast majority of patients with disseminated MAC infection and positive blood cultures have advanced HIV infection.…”

“…Although not all patients who prove to have MAC infection at other sites or at autopsy have had positive blood cultures, the majority do. Moreover, the level of bacteremia that has been identified has been very high, with colony counts typically in the range of 1,000 to 17,000 CFU/ml (84).…”

“…Since mycobacteria are intracellular organisms, lysis of cells prior to inoculation of media was soon incorporated into laboratory protocols. The lysis-centrifugation system soon became the most common method used, and it improved recovery in all the above media (56,57,84,100,127). Use of the Isolator system, however, required additional laboratory steps that are not otherwise necessary in inoculation of blood cultures.…”

Early Diagnosis and Treatment of Opportunistic Mycobacterial Infections in HIV-Seropositive AIDS Patients

“…Overall, approximately 25-40% of febrile AIDS patients with a consistent clinical syndrome hospitalised at New York's Sloan Kettering Center have had Maavium bacteremia, whilst the prevalence of disseminated M.avium infection increases to over 70% once infections such as Pn..um y.tis, cytomegalovirus and diarrheal pathogens have been excluded as the cause of fever and other symptoms (3). Bacteremia is continuous and high-grade with quantitation at 20-30,000 CFU/ml (13,14). Tissue loads are one million times higher, at about 109 CFU/g tissue (13).…”