Rapidly growing non-tuberculous mycobacterial infection in a renal transplant patient after alemtuzumab induction

Renal transplant recipients are at high risk of developing opportunistic infections particularly in the first 6 months after transplantation. Organisms causing such infections include rapidly growing non-tuberculous mycobacteria (NTM). Lymphocytes have a central role in combating mycobacterial infections. The use of lymphocyte-depleting agents, such as alemtuzumab, in the renal transplant population has increased in recent years. A case of multifocal osteomyelitis caused by one of the NTM, Mycobacterium chelonae, in a renal transplant recipient, after alemtuzumab induction, is presented.

Antimicrobial susceptibility of nontuberculous mycobacteria from eye infections

PURPOSE

To characterize formerly designated atypical or nontuberculous mycobacteria (NTM) associated with eye infections.

METHODS

All clinical NTM eye isolates (112 isolates from 100 patients) submitted to a single national NTM reference laboratory between 1982 and 2009 were identified using polymerase chain reaction and restriction fragment length polymorphism of the hsp65 gene. Isolates were tested against 10 antimicrobials, including besifloxacin, a new 8-chloro-fluoroquinolone. Assessments included species of NTM recovered, year of isolation, type of eye infection, geographic location, and drug susceptibilities.

RESULTS

In the 1980s, the major pathogen isolated was Mycobacterium abscessus. In the 1990 s, Mycobacterium chelonae emerged as the major pathogen. By 2000, it was responsible for more than 50% of all cases. The majority of M. abscessus and Mycobacterium fortuitum were from southern coastal states and Texas, whereas M. chelonae isolates were more widespread geographically. The most active antimicrobials were amikacin and clarithromycin/azithromycin for M. abscessus and clarithromycin/azithromycin, amikacin, and tobramycin, and the quinolones for M. chelonae.

CONCLUSIONS

This is the largest study of NTM ophthalmic isolates to date and is the first to include susceptibilities and molecular identification for all isolates studied. This series establishes M. chelonae (44%) and M. abscessus (37%) as the NTM species most frequently associated with ophthalmic infections. Topical ophthalmic fluoroquinolones may have a role in the management of ocular infections involving M. chelonae and M. fortuitum.

Antimicrobial susceptibility testing, drug resistance mechanisms, and therapy of infections with nontuberculous mycobacteria

Within the past 10 years, treatment and diagnostic guidelines for nontuberculous mycobacteria have been recommended by the American Thoracic Society (ATS) and the Infectious Diseases Society of America (IDSA). Moreover, the Clinical and Laboratory Standards Institute (CLSI) has published and recently (in 2011) updated recommendations including suggested antimicrobial and susceptibility breakpoints. The CLSI has also recommended the broth microdilution method as the gold standard for laboratories performing antimicrobial susceptibility testing of nontuberculous mycobacteria. This article reviews the laboratory, diagnostic, and treatment guidelines together with established and probable drug resistance mechanisms of the nontuberculous mycobacteria.

Mycobacterium abscessus from respiratory isolates: activities of drug combinations

Mycobacterium abscessus is the most resistant of rapidly growing pathogenic mycobacteria. We performed a screening of the in vitro sterilizing capacity of various antibiotic combinations against two strains isolated from respiratory samples (in vitro activity of each antibiotic: 51 combinations of two drugs and 47 of three drugs). Our findings confirm that clarithromycin is the most useful drug. The combination of this drug with linezolid exhibits good activity. In addition, the fluoroquinolones and rifabutin in association with clarithromycin may have clinical utility because they are administered orally. Therapeutic alternatives in this type of infections should be evaluated in greater depth.