Molecular epidemiological study on transmission of tuberculosis in a hospital for mentally handicapped patients in Havana, Cuba.

The IS 6110 restriction fragment length polymorphism (RFLP) analysis of Mycobacterium tuberculosis isolates has revolutionized the description of the epidemiology of tuberculosis. This technique has been used to confirm suspected cases of transmission in several institutional settings. In this study, we analysed by conventional and molecular epidemiological methods the unexpectedly high number of tuberculosis cases which occurred among 14 mentally handicapped patients and a healthcare worker in Havana's Psychiatric Hospital in the period from 1995 to 1998. Twelve M. tuberculosis isolates of the respective patients showed the same DNA fingerprint, consisting of nine bands. Three other different IS 6110 RFLP patterns with 10, eight, and 10 bands were observed. The results of RFLP analysis and of an additional epidemiological investigation allowed the identification of the probable source of this chain of transmission in the healthcare facility. This would not have been possible without the aid of DNA fingerprinting. Delays in diagnosis of the source patient and of the secondary cases, a tardy and deficient tuberculin skin test and the difficulties of management of mentally handicapped patients probably contributed to spread the M. tuberculosis strain in Havana's Psychiatric Hospital.

Transmission of tuberculosis in Havana, Cuba: a molecular epidemiological study by IS6110 restriction fragment length polymorphism typing

The combination of molecular and conventional epidemiological methods has improved the knowledge about the transmission of tuberculosis in urban populations. To examine transmission of tuberculosis in Havana, Cuba, with DNA fingerprinting, we studied 51 out of 92 Mycobacterium tuberculosis strains isolated from tuberculosis patients who resided in Havana and whose infection was culture-confirmed in the period from September 1997 to March 1998. Isolates from 28 patients (55 percent) had unique IS6110 restriction fragment length polymorphism (RFLP) patterns, while isolates from 23 others (45 percent) had identical patterns and belonged to 7 clusters. Three clusters consisting of six, five and two cases were each related to small outbreaks that occurred in a closed setting. Three other clustered cases were linked to a large outbreak that occurred in another institution. Younger patients were more correlated to clustering than older ones. The finding that 45 percent of the isolates had clustered RFLP patterns suggests that recent transmission is a key factor in the tuberculosis cases in Havana. The IS6110 RFLP typing made it possible to define the occurrence of outbreaks in two closed institutions

Molecular epidemiology of tuberculosis in Cuba outside of Havana, July 1994-June 1995: utility of spoligotyping versus IS6110 restriction fragment length polymorphism.

SETTING: Molecular typing has become an important tool for examining the extent of active transmission of tuberculosis. OBJECTIVES: To examine transmission of tuberculosis in Cuba using IS6110 restriction fragment length polymorphism (RFLP) typing and to evaluate the utility of spoligotyping. DESIGN: One hundred and sixty Mycobacterium tuberculosis strains isolated over a one year period in Cuba were subjected to RFLP and spoligotyping. RESULTS: Forty-eight percent of the isolates were found in 19 clusters of strains with identical RFLP patterns. In general, cluster sizes were limited, except for two large institutional outbreaks. Age was strongly inversely correlated to clustering. Most streptomycin-resistant isolates were found in clusters. Fifteen spoligotype clusters comprised 78% of the isolates. Significantly different IS6110 RFLP types subdivided 11 spoligotype clusters, whereas none of the IS6110 clusters were subdivided by spoligotyping. CONCLUSIONS: Considering the short study period, 48% clustering is high, indicating that recent transmission plays an important role in Cuba. Although resistance is still a minor problem, transmission of streptomycin-resistant strains occurs. The high polymorphism observed with IS6110 RFLP indicates that this marker is useful for future molecular epidemiological studies in Cuba. Spoligotyping appeared less suitable for population-based studies.