VP4 and VP7 genotyping by reverse transcription-PCR of human rotavirus in mexican children with acute diarrhea.

Dual typing (VP4 and VP7) of rotavirus obtained from 257 Mexican children during three epidemiological seasons was performed by reverse transcription-PCR. The P1G1 genotype was the most prevalent (40%), followed by P1G3 (19%) and P2G2 (16%). Thirty-one specimens (12%) presented mixed infections, while some genotypes were not found. This is the first dual typing of isolates from diarrhea cases in Mexico.

Clinical consequences and transmissibility of drug-resistant tuberculosis in southern Mexico.

BACKGROUND: Consequences of drug-resistant tuberculosis (TB) in developing countries using directly observed treatment, short-course (DOTS), are not well defined. OBJECTIVE: To determine the impact of drug resistance on clinical outcome and transmission of TB under programmatic conditions. PATIENTS AND METHODS: A prospective cohort and molecular epidemiologic study was conducted in southern Mexico. Between March 1995 and February 1998 all patients with persistent cough whose sputa had acid-fast bacilli (AFB) underwent clinical and mycobacteriologic evaluation (species identification, drug susceptibility testing, and IS6110-based genotyping). Treatment was provided in accordance with Mexico's National Tuberculosis Program. Clinical and microbiologic outcomes and molecular epidemiologically defined transmission were measured. RESULTS: Mycobacterium tuberculosis was isolated from 238 of the 284 AFB smear-positive persons. The overall rate of resistance was 28.4% (new, 20.7%; retreated, 54.7%), and 10.8% (new, 3.3%; retreated, 35.8%) had multi-drug-resistant TB (ie, resistance to isoniazid and rifampin). After treatment, 75% (new, 81.0%; retreated, 52.8%) were cured, 8% (new, 7.8%; retreated, 7.5%) abandoned therapy, 9% (new, 3.9%; retreated, 28.3%) had treatment failure, and 4% (new, 3.3%; retreated, 7.5%) died. Another 2% of patients relapsed, and 9% died during a median of 24.4 months of follow-up. Drug-resistance was a strong independent risk factor for treatment failure. Being infected with multi-drug-resistant TB was the only factor associated with a decreased likelihood of being in a restriction fragment length polymorphism cluster. CONCLUSIONS: Despite the use of DOTS, patients with drug-resistant TB had a dramatically increased probability of treatment failure and death. Although multi-drug-resistant TB may have a decreased propensity to spread and cause disease, it has a profoundly negative impact on TB control.

The role of core groups in transmitting Mycobacterium tuberculosis in a high prevalence community in Southern Mexico.

SETTING: A community in Southern Mexico with a high prevalence of tuberculosis. OBJECTIVE: To characterize the transmission dynamics in a region with a DOTS-based tuberculosis control program. DESIGN: Community-based screening of chronic coughers between 1 March 1995 and 31 August 1996. Individuals with acid-fast bacilli (AFB) in their sputum were enrolled, interviewed, and had mycobacterial cultures and fingerprinting performed. In-depth interviews were conducted on all persons with DNA fingerprinting. RESULTS: AFB smears were performed on 1424 individuals, 124 of whom were microbiologically confirmed. Of the 95 cases for whom bacterial DNA fingerprints were available, 38 were in clusters. The largest cluster involved seven individuals who were members of a social network centered on a series of unlicensed bars. CONCLUSION: This population-based molecular epidemiologic study showed that a focus of transmission within a social network accounted for one fourth of transmission which rapidly progressed to disease. These observations raise questions about the potential benefit of targeted tuberculosis control interventions in health jurisdictions approaching WHO-defined DOTS benchmarks.

Comparison among three methods for mycobacteria identification.

OBJECTIVE: To compare three methods: Biochemical tests, high-performance liquid chromatography (HPLC) and polymerase chain reaction-restriction fragments length polymorphism (PCR-RFLP), for the identification of mycobacteria, and to perform a cost-benefit analysis to define an optimum identification algorithm. MATERIAL AND METHODS: One-hundred-and-seven mycobacteria isolates were identified by the three methods at Instituto de Diagnóstico y Referencia Epidemiológicos, between February of 1999 and January of 2000 and the results were compared with those of a reference laboratory using the Q-Cochran statistical test. RESULTS: PCR-RFLP was the most rapid and specific procedure but also the most expensive; biochemical tests excelled for identification of Mycobacterium tuberculosis, but were lengthy and expensive for other mycobacteria; HPLC ranked in the middle for price, speed and specificity. CONCLUSIONS: Considering the expected proportion of M. tuberculosis, the following algorithm was proposed: Initially, biochemical tests should be performed; if the results indicate a non-tuberculous mycobacteria, the isolate should be analyzed with HPLC; if results are unclear, the isolate should be analyzed using PCR-RFLP. Isolates showing a previously undescribed PCR-RFLP pattern should be characterized by DNA sequencing.

Mycobacterium tuberculosis drug resistance in a suburban community in southern Mexico.

OBJECTIVE: To determine the impact of drug resistance (DR) on the clinical outcome and transmission of tuberculosis under programmatic conditions. METHODS: Prospective cohort and molecular epidemiologic study in the Orizaba Health Jurisdiction of Mexico. Between March 1995 and July 1999, chronic coughers with positive acid-fast bacilli (AFB) detected in sputum smear underwent clinical and mycobacteriologic evaluation (species identification, drug susceptibility testing and IS6110-based genotyping). Treatment was provided in accordance with official norms. RESULTS: Mycobacterium tuberculosis was isolated from 326/387 AFB-positive cases. The rate of DR was 24.2% and that of multidrug resistance (MDR, defined as resistance to both isoniazid and rifampin at least) was 7.7%; 78% were cured, 8% abandoned treatment, 6% failed treatment, and 5% died. An additional 13.5% received retreatment and 8.9% died during a median 28.6 months of follow up. Factors associated with DR by multivariate analysis were chronicity of tuberculosis (OR 4.8, 95%CI 2.7-8.4, P < 0.001), age >40 years (OR 1.9, 95%CI 1.1-3.2, P = 0.02) and indigenous origin (OR 0.3, 95%CI 0.13-0.75, P = 0.01). Cox-adjusted relative risks showed that MDR (RR 2.5, 95%CI 1.02-6.16, P = 0.04), HIV infection (RR 31.3, 95%CI 11.6-84.8, P < 0.001), and chronicity of tuberculosis (RR 2.1, 95%CI 1.0-4.4, P = 0.06) were associated with mortality, controlling for age. Predictors of retreatment were DR (not including MDR) (RR 2.2 95%CI 0.89-5.31, P < 0.087), MDR (RR 12.6, 95%CI 5.46-28.88, P < 0.001), and living in a household with an earthen floor (RR 2.8, 95%CI 1.27-6.13, P = 0.011). Being infected with MDR-TB was the only factor associated with a decreased likelihood of being in an RFLP cluster (OR 0.31, 95%CI 0.12-0.81, P = 0.02). CONCLUSIONS: Although MDR-TB may have a decreased propensity to spread and cause disease, it has a profoundly negative impact on tuberculosis control.