Correlations between major risk factors and closely related Mycobacterium tuberculosis isolates grouped by three current enotyping procedures: a population-based study in northeast Mexico

The characteristics of tuberculosis (TB) patients related to a chain of recent TB transmissions were investigated. Mycobacterium tuberculosis (MTB) isolates (120) were genotyped using the restriction fragment length polymorphism-IS6110 (R), spacer oligotyping (S) and mycobacterial interspersed repetitive units-variable number of tandem repeats (M) methods. The MTB isolates were clustered and the clusters were grouped according to the similarities of their genotypes. Spearman’s rank correlation coefficients between the groups of MTB isolates with similar genotypes and those patient characteristics indicating a risk for a pulmonary TB (PTB) chain transmission were ana- lysed. The isolates showing similar genotypes were distributed as follows: SMR (5%), SM (12.5%), SR (1.67%), MR (0%), S (46.67%), M (5%) and R (0%). The remaining 35 cases were orphans. SMR exhibited a significant correlation (p < 0.05) with visits to clinics, municipalities and comorbidities (primarily diabetes mellitus). S correlated with drug consumption and M with comorbidities. SMR is needed to identify a social network in metropolitan areas for PTB transmission and S and M are able to detect risk factors as secondary components of a transmission chain of TB.

A population-based study of first and second-line drug-resistant tuberculosis in a high-burden area of the Mexico/United States border

The resistance of 139 Mycobacterium tuberculosis (MTB) isolates from the city of Monterrey, Northeast Mexico, to first and second-line anti-TB drugs was analysed. A total of 73 isolates were susceptible and 66 were resistant to anti-TB drugs. Monoresistance to streptomycin, isoniazid (INH) and ethambutol was observed in 29 cases. Resistance to INH was found in 52 cases and in 29 cases INH resistance was combined with resistance to two or three drugs. A total of 24 isolates were multidrug-resistant (MDR) resistant to at least INH and rifampicin and 11 MDR cases were resistant to five drugs. The proportion of MDR-TB among new TB cases in our target population was 0.72% (1/139 cases). The proportion of MDR-TB among previously treated cases was 25.18% (35/139 cases). The 13 polyresistant and 24 MDR isolates were assayed against the following seven second-line drugs: amikacin (AMK), kanamycin (KAN), capreomycin (CAP), clofazimine (CLF), ethionamide (ETH), ofloxacin (OFL) and cycloserine (CLS). Resistance to CLF, OFL or CLS was not observed. Resistance was detected to ETH (10.80%) and to AMK (2.70%), KAN (2.70%) and CAP (2.70%). One isolate of MDR with primary resistance was also resistant to three second-line drugs. Monterrey has a high prevalence of MDR-TB among previously treated cases and extensively drug-resistant-MTB strains may soon appear.

Serotipos de Salmonelas identificados en México entre 1974 y 1981 / Salmonella serotypes identified in México between 1974 and 1981

Entre 1974 y 1981 se tipificaron en México 4 522 cepas de Salmonella. De ellas, 1 619 procedían de alimentos, 100 de aguas de drenaje y animales, y 2 803 eran de origen humano. De los 80 tipos que se identificaron 35 no se habían reconocido con anterioridad. En cuanto a la frecuencia con que se aisló cada serotipo, Salmonella typhimurium ocupó el primer lugar en humanos (45,7%) seguido por S. derby (8,6%) y S. newport (7.8%); en alimentos S. derby fue el más frecuente (27,9%) seguido por S. anatum (9,6%) y S. typhimurium (8,9%). S. typhimurium se aisló con más frecuencia de pacientes de hospitales que de los que asistían a laboratorios clínicos privados (53,0 y 24,1% respectivamente), aunque predominó en ambos casos. Se destaca el aumento de la frecuencia de S. newport a partir de 1979 en las cepas de origen humano provenientes en su mayor parte de dos hospitales de la ciudad de México. Este incremento no se observó, sin embargo, en cepas procedentes de alimentos o de otras fuentes