02609nas a2200325   4500000000100000008004100001260001300042653003100055653001800086653001900104653002000123653001100143653001800154653002800172653001400200653003000214653001200244653002200256653002300278100001500301700001200316700001200328700001200340700001300352245008500365300001200450490000700462520180000469022001402269       2006                            d  c2006 Apr10aBacteriological Techniques10aCulture Media10aDNA, Bacterial10aDecontamination10aMalawi10aMycobacterium10aMycobacterium fortuitum10aPhylogeny10apolymerase chain reaction10aSeasons10aSoil Microbiology10aWater Microbiology1 aChilima BZ1 aClark I1 aFloyd S1 aFine PE1 aHirsch P00aDistribution of environmental mycobacteria in Karonga District, northern Malawi.  a2343-500 v723 a<p>The genus Mycobacterium includes many species that are commonly found in the environment (in soil and water or associated with plants and animals), as well as species that are responsible for two major human diseases, tuberculosis (Mycobacterium tuberculosis) and leprosy (Mycobacterium leprae). The distribution of environmental mycobacteria was investigated in the context of a long-term study of leprosy, tuberculosis, Mycobacterium bovis BCG vaccination, and the responses of individuals to various mycobacterial antigens in Karonga District, northern Malawi, where epidemiological studies had indicated previously that people may be exposed to different mycobacterial species in the northern and southern parts of the district. A total of 148 soil samples and 24 water samples were collected from various locations and examined to determine the presence of mycobacteria. The detection method involved semiselective culturing and acid-fast staining, following decontamination of samples to enrich mycobacteria and reduce the numbers of other microorganisms, or PCR with primers specific for the mycobacterial 16S rRNA gene, using DNA extracted directly from soil and water samples. Mycobacteria were detected in the majority of the samples, and subsequent sequence analysis of PCR products amplified directly from soil DNA indicated that most of the products were related to known environmental mycobacteria. For both methods the rates of recovery were consistently higher for dry season samples than for wet season samples. All isolates cultured from soil appeared to be strains of Mycobacterium fortuitum. This study revealed a complex pattern for the environmental mycobacterial flora but identified no clear differences between the northern and southern parts of Karonga District.</p>  a0099-2240