In Vivo IS 6110 Profile Changes in a Mycobacterium tuberculosis Strain as Determined by Tracking over 14 Years

Abstract

f Transposition and homologous recombination of IS6110 appear in Mycobacterium tuberculosis along in vivo sequential infections. These events were checked in different clones of a successful strain, M. tuberculosis Zaragoza, with the focus on a variant in which integration of a copy of IS6110 in the origin of replication (oriC) region occurred. Clonal Mycobacterium tuberculosis variants appear along the sequential infections of hosts involved in the same transmission cluster (1). IS6110 in M. tuberculosis has been one of the most widely used elements in molecular epidemiology and has a transposition rate estimated at ϳ18% over a period of 5 to 6 years (2). The IS6110 element itself modulates expression of neighboring genes and, depending on its location, could confer both transmission ability and virulence (3-5). Microevolution events due to the transposition of IS6110 are usually reflected in variations of restriction fragment length polymorphism (RFLP) patterns (6, 7). Minor variations in IS6110 fingerprints, spoligotypes, or mycobacterial interspersed repetitive-unit (MIRU)-variable-number tandem-repeat (VNTR) loci reveal microevolution in clonal infections (6,8). These changes could have effects on the molecular structure of the mycobacterial genome and the biology of the bacillus (7).Molecular epidemiological studies carried out for more than a decade have provided accuracy in the study of the transmission (9). The usefulness of the approach has been proven, even in countries with low incidences of tuberculosis (10). The M. tuberculosis Zaragoza strain spread in Zaragoza, Spain, and reached 18.7% of all isolates of M. tuberculosis in 2001 to 2004 (11). This strain was classified in principal genetic group 3 and in singlenucleotide polymorphism (SNP) cluster group 6a (12), it demonstrated the rare spoligotype SIT773, and it carried 12 localized copies of IS6110 (13). In addition, in the context of a highthroughput survey of in vivo IS6110 transposition in multiple M. tuberculosis genomes, an additional IS6110 copy was detected in the oriC region in one isolate (14). The purpose of this study was to review the in vivo genomic changes of the M. tuberculosis Zaragoza strain, focusing on this variant.Among the 2,348 isolates collected between 2000 and 2013, 246 were identified as M. tuberculosis Zaragoza by IS6110 RFLP typing (15) and spoligotyping (16) in the context of tuberculosis surveillance in our region. By tracking the strain changes throughout time, we found 7 different variants, i.e., variants 1 to 7 (Fig. 1). An additional copy of IS6110 was detected in six evolved clones, namely, variants 1 to 6. Variant 7 lost one copy in the RFLP pattern and was the only variant that revealed a change in its spoligotyping pattern. Clones 1, 2, 4, 5, 6, and 7 were isolated from only one patient, whereas variant 3 was isolated from 12 patients, as described below.In variant 7, 10 of the 12 IS6110 insertion sites known for M. tuberculosis Zaragoza were confirmed by PCR (13). However, the two nonamplified copies were l...

A Mycobacterium tuberculosis Beijing strain persists at high rates and extends its geographic boundaries 20 years after importation

“…More than a thousand cases infected by this single strain have been identified during the last 23 years 17 . Similar findings were reported in Zaragoza, Spain, where a strain progressed from being low-prevalence to responsible for around 20% of the all tuberculosis cases in the population, with high rates maintained throughout the period 18 .…”

A whole-genome sequencing study of an X-family tuberculosis outbreak focus on transmission chain along 25 years

“…In addition, it shared the five locations of the IS6110 with Ara50. Modifications in the RFLP pattern were observed before for strains belonging to the same cluster [19,20]. In contrast, three of these isolates were not related to the Ara50 outbreak.…”

New insights into the transposition mechanisms of IS6110 and its dynamic distribution between Mycobacterium tuberculosis Complex lineages

“…Diverse epidemiological studies have demonstrated that IS 6110 RFLP presents distinct profiles in M . tuberculosis transmission clusters [ 28 , 64 – 67 ]. Since these studies involve isolates from different patients isolated during prolonged periods of time, it is plausible to think that IS 6110 -mediated adaptive mechanisms might be involved in the patient-to-patient transmission of M .…”

“…This confers plasticity to the MTBC genomes and could have significant biological implications. As for other IS, insertion of IS 6110 into a coding region frequently renders the gene inactive, the basis of transposon mutagenesis, or the recombination between two IS 6110 copies can lead to either inversion or deletion of the chromosomal fragment between them [ 26 – 28 ]. Furthermore, it has been demonstrated that IS 6110 acts as a mobile promoter and this phenotype is selectively activated during in vitro infection of monocytes/macrophages [ 29 , 30 ].…”