NTM are ubiquitously present in the environment and can therefore be associated with either colonization, serious infection, or pseudo-outbreaks with a wide variety of presentations (10
). NTM should be considered in all cases of nosocomial infection, and careful surveillance must be applied to identify possible outbreaks. Presumed nosocomial outbreaks of NTM can be investigated by molecular typing of mycobacterial isolates. In cases where identical DNA fingerprints are found, laboratory cross-contamination cannot always be excluded. However, in our study, all possible measures were taken to avoid any laboratory cross-contamination. The NTM were cultured from patients with compatible clinical syndromes and were isolated from specimens that do not normally contain microorganisms. Molecular analysis revealed that the mycobacterial isolates represented several evolutionary lineages and more subtle strain variations. Therefore, in our study, laboratory cross-contamination is considered highly unlikely.
On basis of the diagnostic criteria of the American Thoracic Society, the medical relevance of the NTM isolations reported here appears certain for at least half of the cases (cases 1, 6, 7, and 8). Their signs and symptoms were compatible with pathology found on physical examination or chest X ray, and the NTM were isolated from pleural effusions and a lymph node. In the other four cases (cases 2, 3, 4, and 5), NTM were isolated from ascites and a cutaneous abscess, and in these cases, it is not completely clear whether these mycobacteria were the most important causes of the pathologies. These last patients had other conditions that could have explained their nonspecific symptoms and the physical findings.
In none of the eight patients diagnosed with NTM infection of normally sterile body sites was the diagnosis made before hospital discharge or death. No specific therapy was given for the mycobacteria isolated, except for patient 2, who received empirical treatment with rifampin, isoniazid, and pyrazinamide before the results of the culture became available. In five of the six specimens of sterile body sites, which were decontaminated with sulfuric acid and NALC-NaOH, NTM were cultured only after decontamination with sulfuric acid. However, the commonly used decontamination method is the use of NALC-NaOH. It has been shown that the decontamination method used affects the recovery of NTM (4
Only a few cases of human disease caused by M. lentiflavum
have been reported previously. The first case, concerning an 85-year-old woman with spondylodiscitis that improved upon antituberculous treatment, was reported in 1996 (24
). Four children with lymphadenitis due to M. lentiflavum
were described between 1997 and 2002 (5
), as were cases of disseminated infection in an HIV-infected patient (21
) and in a patient undergoing steroid therapy (13
). Finally, M. lentiflavum
was isolated from a patient with a chronic pulmonary disease. M. goodii
was first described in 1999 and was isolated from patients with traumatic osteomyelitis following iatrogenic infections and from patients with respiratory infections (3
). Recently, a patient with bursitis due to an M. goodii
infection was described (9
). All of these cases occurred in Europe and the United States. To our knowledge, here we describe the first cases of M. lentiflavum
and M. goodii
infection in African patients. In fact, no clinically relevant NTM isolations in sub-Saharan Africa were reported before the 1990s (11
Our htAFLP-mediated strain-typing method further corroborates the clinical relevance of the isolates; genetic diversity was observed among the strains. This degree of strain diversity shows that (i) the typing procedure is as adequate as can be expected when small numbers of strains are used and (ii) it is not the case that laboratory cross-contamination is the source of all of the M. lentiflavum isolates. However, multiple isolates of genotype D (Table ) were identified. Whether this is due to laboratory contamination or a genuine NTM outbreak still needs to be resolved. It has to be emphasized that the respective type D strains were derived from patients nursed in different wards. The elevated incidence of the type D M. lentiflavum isolates (7/10 [70%] of the Zambian isolates) suggests that local dissemination of a certain type occurred or that M. lentiflavum as a species is quite clonal. The latter hypothesis is not in contradiction with the well-conserved features of the htAFLP fingerprints, even when isolates from The Netherlands and Zambia are compared (Fig. ). In addition, both restriction fragment length polymorphism analysis and randomly amplified polymorphic DNA analysis performed for a subset of strains also revealed additional DNA polymorphisms among M. lentiflavum isolates (results not shown).
We conclude from our study that clinically relevant infection due to NTM seems to occur in HIV-positive as well as in HIV-negative patients in Zambia. The role of NTM in human disease in Africa may well be underestimated and should be examined in more detail and on a larger scale. Information is urgently needed with regard to the proper diagnostic procedures and the possibilities for adequate treatment of NTM-induced disease.