[Utility of gas chromatography for the identification of mycobacterial species]

The human immunodeficiency virus (HIV) epidemic has altered the epidemiological profile of tuberculosis in both industrialized and developing countries. Serious diseases caused by mycobacteria other than Mycobacterium tuberculosis, mostly belonging to the M. avium-intracellulare complex (MAC), have become very common in association with severe immunosuppression. The increase in mycobacterial disease complexity has stimulated the development of more rapid and efficient methods for diagnosis. In the present study, we investigated and assessed the suitability of a gas-liquid chromatography technique for diagnosis of clinically important mycobacteria in Argentina. An identification scheme was developed from the results obtained in a previous study where we characterized the cellular fatty acids and the mycolic acid cleavage products from most frequent species in Argentina. Of 183 isolates tested, 69% were correctly identified to species level and 5% were incorrectly classified. If we only take into account the isolates that could be identified, 93% were correctly identified. Although all of the isolates of M. tuberculosis were correctly identified, four isolates of MAC incorrectly matched by M. tuberculosis. Gas chromatography provides a rapid technique of highly predictive value for mycobacteria identification; it could be used in reference laboratories as a rapid presumptive identification until the biochemical tests are completed.

Immigration and health: the Italian National Focal Point experience

This report is a description of the situation of migrant populations in Italy. It was written by a committed team of experts from public institutions, non-governmental organisations (NGO) and volunteer associations that for three years have been part of the Italian National Focal Point (NFP) within the European Project "AIDS & Mobility", which is being co-ordinated by the Netherlands Institute for Health Promotion and Disease Prevention (the Netherlands) and financed by the European Commission DG/V. This year the Italian National Focal Point, co-ordinated by the Telefono Verde AIDS of the Istituto Superiore di Sanità, has produced a second report (the first one was published in 1998) on health issues related to migrant populations. Besides providing an updated picture on the presence of foreigners in Italy, such report illustrates the present legislative situation within the sanitary area and some interventions regarding prevention, treatment and rehabilitation provided by each structure in the Italian NFP to foreign citizens. The initiatives carried out during the year 1999 by public institutions, NGO and volunteer associations are also reported in order to detect the psycho-social-sanitary needs of immigrants and target prevention programmes to their particular and specific needs.

Usefulness of spoligotyping in molecular epidemiology of Mycobacterium bovis-related infections in South America

Two hundred twenty-four Mycobacterium bovis isolates, mainly from South American countries, were typed by spoligotyping, and 41 different spoligotypes were identified. A total of 202 M. bovis isolates (90%) were grouped into 19 different clusters. The largest cluster contained 96 isolates (42.8%) on the basis of the most frequently observed spoligotype, spoligotype 34. Nineteen M. bovis isolates from humans in Argentina had spoligotypes and polymorphic GC-rich repetitive sequence (PGRS) types that represented the most common types found among isolates from cattle. All five isolates from Uruguay and three of the six isolates from Paraguay had spoligotypes that were also detected for isolates from Argentina. The spoligotypes of isolates from Brazil, Costa Rica, and Mexico and of some of the isolates from Paraguay could not be found in Argentina. A total of 154 M. bovis isolates were selected in order to compare the discriminative power of spoligotyping and restriction fragment length polymorphism (RFLP) analysis with direct repeat (DR) and PGRS probes. By spoligotyping, 31 different types were found, while AluI-digested DR probe-associated RFLP analysis identified 42 types, and RFLP analysis with the PGRS probe also detected 42 types; these were partly independent of the DR types. By combining the results obtained by spoligotyping and by RFLP analysis with the DR and PGRS probes, 88 different types were obtained. Although the differentiation of M. bovis by spoligotyping was less discriminatory than differentiation by RFLP analysis with the DR and PGRS probes, spoligotyping is easier to perform and its results are easier to interpret. Therefore, for the purpose of typing of M. bovis isolates, spoligotyping could be performed first and the isolates could be grouped into clusters and then analyzed by RFLP analysis with the DR and PGRS probes.

[Resistance and multiresistance to antitubercular drugs in Argentina and in other Latin American countries]

Resistance of Mycobacterium tuberculosis to both isoniazid (INH) and rifampicin (RPM), the most important antituberculosis drugs, with or without simultaneous resistance to other drugs, is known as multidrug resistance (MDR). It is the main obstacle to attain the cure of patients by the specific treatment, and a threat to the tuberculosis control. Between 1994 and 1997, several Latin American countries undertook countrywide surveys or surveillance programs to determine their primary and acquired drug resistance prevalence rates. These studies followed the WHO/International Union Against Tuberculosis and Lung Diseases (IUATLD) guidelines. Percentages of not previously treated patients with tuberculosis due to MDR strains ranged from null or very small (Uruguay, Cuba, Chile) to 4% or higher (Dominican Republic, Argentina). In Argentina, a remarkable correlation between MDR tuberculosis, AIDS and the assistance in urban reference hospitals for infections diseases was observed. Coincidentally with the survey, nosocomial spread of HIV-related MDR tuberculosis occurred in two of these hospitals situated in Buenos Aires and Rosario. But, at the same time, an alarming emergence of MDR was evidenced among non HIV-infected patients with history of previous antituberculosis treatment. Directly observed treatment (DOT) should be increasingly applied, and drug supply guaranteed. Treatment as well as microscopy services for diagnosis and follow up of patients, should be decentralized from the big specialized hospitals in urban areas to the peripheral health centers, in order to make easier for the patients to attend regularly and receive their medications. These strategies will contribute to increase cure rates and to reduce the tuberculosis transmission.

[Etiology of acute lower respiratory tract infections among children younger than 5 years old in Santa Fe]

The etiology of acute lower respiratory tract infections (ARI) and nasopharyngeal bacterial carriage in children less than 5 years old living in Santa Fe city, Argentina, was studied. A total of 518 children were included in the study: 450 suffering from ARI and 68 asymptomatic children. Blood samples, pleural effusions and nasopharyngeal secretions (NS) were obtained from children for bacterial isolations. NS was also used for fluorescent antibody techniques, and serum samples were employed for detecting IgM anti Chlamydia trachomatis. A bacterial pathogen was isolated from blood in 6.2% (14/224) of the children with ARI. A total of 11 Streptococcus pneumoniae (five of them oxacillin resistant), two Haemophilus influenzae and one Staphylococcus aureus strains were isolated. The most frequently detected pathogen in the ARI group was respiratory syncytial virus (RSV). It was found in 23.3% (105/450) of the children with ARI. Among children with risk of Chlamydia trachomatis infection, 24% presented high titters of specific IgM antibodies. Main bacteria carried in NS in the ARI group were H.influenzae (31.6%) and S. pneumoniae (23.4%) while viridans streptococci (26.5%), H.influenzae (23.5%) and Moraxella catarrhalis (22.1%) were more frequently isolated from controls. The most common pneumococcal types were 14 and 7 and the main type of H.influenzae was b biotype I. During the period of this study, the susceptibility of the pneumococcal isolates to oxacillin decreased from 60% to 50.8%, and the H.influenzae susceptibility to ampicillin fell from 92.3% to 79%. All the H.influenzae type b isolations were susceptible to ampicillin.

Molecular epidemiology of Mycobacterium bovis isolates from South America

One hundred seventy-eight isolates of Mycobacterium bovis were subjected to DNA restriction fragment length polymorphism (RFLP) analysis, using the direct repeat element (DR) and the polymorphic GC-rich repeat sequence (PGRS) as probes. By combining the patterns generated by the two repeat DNA elements, 93 different patterns were observed. One hundred-one isolates were grouped in clusters, which include 25 different clusters. One pattern was the most frequently observed, clustering 18.5% of isolates. It was only found in the Center and northeast regions of Argentina and in one isolate from Paraguay. The isolates from Brazil analyzed here presented exclusive patterns (only found in a particular region). The number of exclusive patterns was high in all argentine regions: northeast 78%, center 81%, and Buenos Aires 81%.

[Characterization of fatty acids and mycolic acid degradation products in mycobacterial species of major incidence in Argentina]

The human immunodeficiency virus (HIV) epidemic has altered the epidemiological profile of tuberculosis in both industrialized and developing countries. Serious diseases caused by mycobacteria other that M. tuberculosis, mostly belonging to the M. avium-intracellulare complex (MAC), have become very common in association with severe immunosuppression. The increase in mycobacterial disease complexity has stimulated the development of more rapid and efficient methods of diagnosis. In the present study we characterized the cellular fatty acids and the mycolic acid cleavage product from most frequent mycobacteria species in Argentina using gas chromatography in order to develop a rapid technique for their identification. Fatty acids and mycolic acids extracted from saponified mycobacterial cells were examined as methyl esters by capillary has chromatography. The major constituent fatty acids in all species, with the exception of M. smegmatis, were octadecenoic (18:1) and hexadecanoic (16:1) acids. The fatty acids and mycolic acid cleavage product profiles from the studied species were quantitatively but not qualitatively different. Tuberculostearic acid was found in all species. Significantly different amounts of some fatty acids (p < 0.01) were observed among clinical isolates of M. tuberculosis, M. bovis and MAC. Traces of 2-eicosanol were detected in the M. tuberculosis H37Rv strain. Although a limited number of strains and species were tested, preliminary results indicate that this method could be used to characterize mycobacterial cultures.