The remaining 119 strains (group II) were collected countrywide in 2002 as part of the National selleck Survey of Tuberculosis Drug-Resistance , coordinated by the Honduran National TB Reference Laboratory (NRL). All strains were isolated on Lowenstein Jensen (LJ) medium and confirmed to be of the
MTC using standard biochemical tests  (niacin production, catalase activity and nitrate reduction). The drug-susceptibility profile of the isolates belonging to group I was determined at the Swedish Institute for Infectious Disease Control (SMI) using the BACTEC 460 system (Becton Dickinson, Sparks, MD USA) , with the following drug concentrations: rifampicin (RIF) 2.0 μg/ml, isoniazid (INH) 0.2 μg/ml, streptomycin (STM)
4.0 μg/ml and ethambutol (EMB) 5.0 μg/ml. For the group II isolates, the proportion method on LJ medium  was performed at the Honduran NRL to determine the susceptibility to the first-line drugs. The following critical concentrations were used: RIF 40 μg/ml, INH 0.2 μg/ml, STM 4.0 μg/ml, EMB 2.0 μg/ml. The strains were subsequently sent to the SMI, where the genotyping was performed. DNA extraction All isolates were subculture on LJ medium at SMI. For spoligotyping, mycobacterial lysates were prepared by MK-1775 clinical trial resuspending 2 loops of bacteria in 250 μl of 1 × TE buffer. After heat-killing the cells at 80°C during 1 hour, the suspensions were centrifuged at 13000 rpm for 2 minutes. Supernatants https://www.selleckchem.com/products/qnz-evp4593.html were discarded and pellets
resuspended in 500 μl of 150 mM NaCl, These centrifugation and resuspension steps were repeated. The final pellet was then dissolved in 25 μl of 1 × TE buffer. For RFLP typing, genomic DNA was obtained using the cetyl-trimethyl ammonium bromide (CTAB) method . Spoligotyping All isolates were genotyped with a spoligotyping commercial kit (Isogen Bioscience, BV Maarsen, The Netherlands) according to the protocol previously described by Kamerbeek et al . Briefly, the DR region of the TB genome was amplified using primers DRa and DRb, and the amplified biotinylated products hybridized to a set of 43 oligonucleotides covalently bound to a membrane. enough The hybridized PCR products were then incubated with a streptavidin-peroxidase conjugate and the membrane then exposed to chemiluminescence (Amersham ECL Direct™ nucleic acid labeling and detection system, GE Healthcare Limited, UK) and exposed on an X-ray film (Amersham Hyperfilm™ ECL, GE Healthcare Limited, UK) according to the manufacturer’s instruction. The X-ray film was developed using standard photochemical procedures after 20 minutes exposure. DNA extracts of M. tuberculosis H37Rv and M. bovis BCG were used as controls. The patterns obtained were analyzed using the BioNumerics software version 5.1 (Applied Maths, Sint-Martens-Latem, Belgium). A cluster was defined as two or more strains sharing identical spoligotyping patterns.