Clinical features of infections caused by new nontuberculous mycobacteria, part I

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.

[Cutaneous and soft skin infections due to non-tuberculous mycobacteria]

The frequency of isolation as well as the number of species of non-tuberculous mycobacteria (NTM) has increased in the last years. Nearly every pathogenic species of NTM may cause skin and soft tissue infections, but rapidly growing mycobacteria (Mycobacterium fortuitum, Mycobacterium chelonae and Mycobacterium abscessus), Mycobacterium marinum and Mycobacterium ulcerans are the most commonly involved. Many of these cutaneous mycobacteriosis, such as rapidly growing mycobacteria, M. marinum, Mycobacterium avium complex, Mycobacterium kansasii or Mycobacterium xenopi are world-wide distributed. In contrast, some others have a specific geographical distribution. This is the case of M. ulcerans, which causes a cutaneous diseases endemic of Central and West Africa (Buruli ulcer) and Australia (Bairnsdale ulcer), being the third mycobacterial infection after tuberculosis and leprosy. Cutaneous mycobacteriosis usually appear either after contact of traumatic or surgical wounds with water or other contaminated products, or, secondarily, as a consequence of a disseminated mycobacterial disease, especially among immunosuppressed patients. For an early diagnosis, it is necessary to maintain a high degree of suspicion in patients with chronic cutaneous diseases and a history of trauma, risk exposure and negative results of conventional microbiological studies. In general, individualized susceptibility testing is not recommended for most NTM infections, except for some species, and in case of therapeutic failure. Treatment includes a combination of different antimicrobial agents, but it must be taken into account that NTM are resistant to conventional antituberculous drugs. Severe cases or those with deep tissues involvement could also be tributary of surgical resection.

Avian mycobacteriosis in companion birds: 20-year survey

The causative agents of avian mycobacteriosis in pet birds are rarely identified. The aim of this study is to add information about the etiology of avian mycobacteriosis. The identification of mycobacterium species in 27 cases of avian mycobacteriosis in pet birds was investigated by polymerase chain reaction (PCR) and sequencing of a rRNA hypervariable region. Avian mycobacteriosis appeared to be an infrequent diagnosis. Interestingly, a few cases of avian mycobacteriosis were recorded in very young birds. The most commonly affected species were the canary (Serinus canarius), the Eurasian goldfinch (Carduelis carduelis) and the red siskin (Spinus cucullatus). All but one bird were infected with Mycobacterium genavense. Mycobacterium avium was identified only in one case.

Atypical mycobacterial infection in patients with cystic fibrosis: update on clinical microbiology methods

While patients with cystic fibrosis (CF) have had dramatic improvement in their survival rates, this has been accompanied by the emergence of more virulent pathogens such as Pseudomonas aeruginosa and Burkholderia cepacia complex organisms. In addition, there has been emergence of organisms of increasing clinical significance such as the nontuberculous mycobacterial (NTM). Although TB infection in patients with CF is extremely uncommon, there is growing concern with regard to atypical Mycobacterium spp, in particular Mycobacterium abscessus. Many methods of decontamination of sputum, which have been adapted from TB methodologies, are ineffective; as shown by the overgrowth of P. aeruginosa, it is essential that decontamination methods are optimized to overcome this. Establishing optimal methods of isolation and determining accurate levels of prevalence is of importance as, although NTM may be isolated relatively infrequently in CF populations, their clinical status in pulmonary disease is now beginning to emerge.

Mycobacterium lentiflavum, an emerging pathogen?

Three cases of infection due to Mycobacterium lentiflavum, a recently described species characterized by multiple resistance to anti-mycobacterial drugs, are reported here. While one case simply adds to the number of cervical lynphadenitis reported in literature, the others concern the first isolations from pleural effusions, in a young boy with leukaemia and in an elderly patient with lung disease, respectively.

Infections due to the newly described species Mycobacterium parascrofulaceum

We report on four cases of infection by the recently described species Mycobacterium parascrofulaceum. In two cases the mycobacterium was isolated from AIDS patients, while in the others it was responsible for pulmonary disease in elderly men. Our findings suggest that M. parascrofulaceum is an opportunistic pathogen, like many other nontuberculous mycobacterial species.