Mycobacterium fortuitum complex in Sweden during an 11-year period

Cardiac device infections due to Mycobacterium fortuitum

Two cases of cardiac device infection due to Mycobacterium fortuitum are reported along with a discussion of their clinical management. Long-term therapy and removal of the infected device is needed. The slow progression and absence of systemic signs and symptoms suggest a low pathogenicity of M fortuitum.

[Disseminated Mycobacterium chelonae infection during HIV. ]

INTRODUCTION

An atypical mycobacterium, Mycobacterium chelonae is a saprophyte germ in the environment, but rarely pathogenic. A few disseminated infections can be noted in immunodepressed patients.

OBSERVATION

A 30 year-old man infected by HIV was hospitalised for deterioration in his general status of health with, on clinical examination, pallor, several superficial lymph nodes and hepatosplenomegaly. A biopsy of an axillary node and the liver revealed numerous granulomas with many atypical M. chelonae-like mycobacteria. Adapted treatment led to complete remission.

DISCUSSION

Immunodepression facilitates the occurrence of M. chelonae infections, often of severe evolution and leading to dissemination. This mycobacterium is resistant to many antibiotics.

SDS-PAGE for identification of species belonging to the Mycobacterium fortuitum complex

We performed a study to determine the usefulness of SDS-PAGE of whole cell proteins for the characterization of species of rapidly growing mycobacteria belonging to the Mycobacterium fortuitum complex. Strains included 37 M. fortuitum, 32 M. chelonae, 10 M. peregrinum, 5 M. abscessus, and 3 M. mucogenicum. Eight collection strains (including type strains of the five species) were also included in the study. All strains yielded between 44 and 58 bands in the electrophoretograms. Intraspecies similarity showed Dice coefficients higher than 95%, with only one strain of M. fortuitum having a six-band difference (Dice coefficient 87.75%). However, interspecies similarity was always below 75%, the similarity being higher between M. fortuitum and M. peregrinum (75.51%) and between M. chelonae and M. abscessus (54.9%). Visual examination of the electrophoretograms was sufficient for species characterization. SDS-PAGE of whole cell proteins is a useful technique for identification of isolates of the M. fortuitum complex, and is easy to perform without the need for complex or expensive equipment.

Emergence of resistance to clarithromycin during treatment of disseminated cutaneous Mycobacterium chelonae infection: case report and literature review

Results of in vitro susceptibility studies and one clinical trial have led to recommendations of clarithromycin monotherapy for the treatment of disseminated cutaneous Mycobacterium chelonae infections. We describe the case of a 65-year-old woman, immunocompromised by the use of chronic steroid therapy, who developed disseminated cutaneous infection with M. chelonae and failed clarithromycin monotherapy due to the development of drug resistance. In the relapse isolate we document the presence of a single point mutation at position 2058 in the gene coding for 23S rRNA peptidyltransferase regions, a mutation previously implicated in the development of resistance to clarithromycin. Two susceptible control isolates lacked the mutation. Three additional reports in the literature of patients developing recurrent skin lesions with clarithromycin-resistant M. chelonae following initial response to monotherapy are summarized. We demonstrate that clarithromycin monotherapy in patients with disseminated cutaneous infections can lead to clarithromycin resistance and therapeutic failure associated with a single point mutation at position 2058 of 23S rRNA.