Streptomycin Monoresistant Mycobacterium tuberculosis
Streptomycin Monoresistant Mycobacterium tuberculosis
A distinct branch of the Mycobacterium tuberculosis W phylogenetic lineage (W14 group) has been identified and characterized by various genotyping techniques. The W14 group comprises three strain variants: W14, W23, and W26, which accounted for 26 clinical isolates from the New York City metropolitan area. The W14 group shares a unique IS6110 hybridizing banding motif as well as distinct polymorphic GC-rich repetitive sequence and variable number tandem repeat patterns. All W14 group members have high levels of streptomycin resistance. When the streptomycin resistance rpsL target gene was sequenced, all members of this strain family had an identical mutation in codon 43. Patients infected with the W14 group were primarily of non-Hispanic black origin (77%); all were US-born. Including HIV positivity, 84% of the patients had at least one known risk factor for tuberculosis.
With the advent of molecular techniques, tuberculosis (TB) investigators have a powerful tool to further the understanding of the transmission and phylogenetic properties of Mycobacterium tuberculosis. Molecular techniques have been used to discriminate exogenous versus endogenous disease, investigate suspected outbreaks and cases of laboratory cross-contamination, study transmission within a defined geographic setting, and demonstrate the occurrence of exogenous superinfection in immunocompetent and immunocompromised patients.
Genotyping has facilitated identification and characterization of the W strain, a multidrug-resistant (MDR) clone associated primarily with nosocomial transmission in hospitals and detention facilities in New York City (NYC) in the early 1990s. In such studies, molecular markers were used to confirm and characterize the W strain outbreak and to elucidate a plausible evolutionary scenario for the sequential acquisition of multidrug resistance. In a recent study, when molecular techniques were applied in a population-based setting, genotyping identified a drug-susceptible group of isolates (W4) that represents a distinct branch of the W phylogenetic lineage. Members of this W4 group define a previously unidentified cluster of cases in a community in northern New Jersey; the cluster likely resulted from both historical and recent transmission. Although the W-MDR strain from NYC is clearly distinct from the drug-susceptible W4 group, both groups of isolates evolved from a common ancestor.
Strains that define the W family have several distinguishing genotypes in common: 1) they belong to principal genetic group 1; 2) they have similar spoligotype patterns, characterized by a deletion of spacers 1-34 and the corresponding repeat in the direct repeats (DR) region, an alteration that defines spoligopattern S00034 and closely related spoligotypes; 3) they contain a unique insertion in the origin of replication and in the NTF locus. Strains grouped in the W or Beijing family are prevalent in China, Southeast Asia, Russia, and other former Soviet regions (unpub. data) and have recently been reported in South Africa.
A distinct branch of the Mycobacterium tuberculosis W phylogenetic lineage (W14 group) has been identified and characterized by various genotyping techniques. The W14 group comprises three strain variants: W14, W23, and W26, which accounted for 26 clinical isolates from the New York City metropolitan area. The W14 group shares a unique IS6110 hybridizing banding motif as well as distinct polymorphic GC-rich repetitive sequence and variable number tandem repeat patterns. All W14 group members have high levels of streptomycin resistance. When the streptomycin resistance rpsL target gene was sequenced, all members of this strain family had an identical mutation in codon 43. Patients infected with the W14 group were primarily of non-Hispanic black origin (77%); all were US-born. Including HIV positivity, 84% of the patients had at least one known risk factor for tuberculosis.
With the advent of molecular techniques, tuberculosis (TB) investigators have a powerful tool to further the understanding of the transmission and phylogenetic properties of Mycobacterium tuberculosis. Molecular techniques have been used to discriminate exogenous versus endogenous disease, investigate suspected outbreaks and cases of laboratory cross-contamination, study transmission within a defined geographic setting, and demonstrate the occurrence of exogenous superinfection in immunocompetent and immunocompromised patients.
Genotyping has facilitated identification and characterization of the W strain, a multidrug-resistant (MDR) clone associated primarily with nosocomial transmission in hospitals and detention facilities in New York City (NYC) in the early 1990s. In such studies, molecular markers were used to confirm and characterize the W strain outbreak and to elucidate a plausible evolutionary scenario for the sequential acquisition of multidrug resistance. In a recent study, when molecular techniques were applied in a population-based setting, genotyping identified a drug-susceptible group of isolates (W4) that represents a distinct branch of the W phylogenetic lineage. Members of this W4 group define a previously unidentified cluster of cases in a community in northern New Jersey; the cluster likely resulted from both historical and recent transmission. Although the W-MDR strain from NYC is clearly distinct from the drug-susceptible W4 group, both groups of isolates evolved from a common ancestor.
Strains that define the W family have several distinguishing genotypes in common: 1) they belong to principal genetic group 1; 2) they have similar spoligotype patterns, characterized by a deletion of spacers 1-34 and the corresponding repeat in the direct repeats (DR) region, an alteration that defines spoligopattern S00034 and closely related spoligotypes; 3) they contain a unique insertion in the origin of replication and in the NTF locus. Strains grouped in the W or Beijing family are prevalent in China, Southeast Asia, Russia, and other former Soviet regions (unpub. data) and have recently been reported in South Africa.
