The optimum cut-off value to differentiate Echinococcus granulosus sensu stricto from other species of E. granulosus sensu lato using larval rostellar hook morphometry.

Cystic echinococcosis caused by Echinococcus granulosus sensu lato is one of the most important helminth zoonoses in the world; it affects both humans and livestock. The disease is endemic in Argentina and highly endemic in the province of Neuquén. Considerable genetic and phenotypic variation has been demonstrated in E. granulosus, and ten different genotypes (G1-G10) have been identified using molecular tools. Echinococcus granulosus sensu lato may be considered a species complex, comprised of E. granulosus sensu stricto (G1-G3), E. equinus (G4), E. ortleppi (G5) and E. canadensis (G6-G10). In endemic areas, the characterization of cystic echinococcosis molecular epidemiology is important in order to apply adequate control strategies. A cut-off value for larval large hook total length to distinguish E. granulosus sensu stricto isolates from those produced by other species of the complex was defined for the first time. Overall, 1780 larval hooks of 36 isolates obtained from sheep (n= 11, G1), goats (n= 10, G6), cattle (n= 5, G6) and pigs (n= 10, G7) were analysed. Validation against molecular genotyping as gold standard was carried out using the receiver operating characteristic (ROC) curve analysis. The optimum cut-off value was defined as 26.5 µm. The proposed method showed high sensitivity (97.8%) and specificity (91.1%). Since in most endemic regions the molecular epidemiology of echinococcosis includes the coexistence of the widely distributed E. granulosus sensu stricto G1 strain and other species of the complex, this technique could be useful as a quick and economical tool for epidemiological and surveillance field studies, when fertile cysts are present.

Molecular characterization of Echinococcus isolates indicates goats as reservoir for Echinococcus canadensis G6 genotype in Neuquén, Patagonia Argentina.

Human cystic echinococcosis is a highly endemic zoonotic disease in the province of Neuquén, Patagonia Argentina, although a hydatid control programme has been carried out since 1970. Human infection due to Echinococcus canadensis (G6 genotype) is frequent in Neuquén. However, the reservoir for this species remains undetermined in a region where camels are absent. We investigated the fertility, viability and molecular epidemiology of hydatid cysts obtained from local goats, pigs and sheep in order to identify the possible reservoirs of E. canadensis (G6). We also analyzed isolates from infected dogs. A total of 67 isolates were identified by the DNA sequencing of the mitochondrial cytochrome c oxidase subunit 1 gene. Cysts from sheep (n=16), goats (n=23) and pigs (n=18) and adult worms from 10 infected dogs were analyzed. The fertility of the hydatid cysts was 78.6%; 90.4% and 94.4% for sheep, goats and pigs, respectively. We detected E. canadensis (G6) in 21 of 23 goat samples and in 1 dog isolate, E. canadensis (G7) in all the pig isolates, E. granulosus sensu stricto (G3) in 1 sheep and the G1 genotype in 15 sheep, 2 goats and 9 dog samples. The G1 haplotypes included the common sheep strain sequence and 2 microvariants of this sequence. E. granulosus sensu stricto (G3) is described for the first time in South America. We conclude that goats act as reservoir for E. canadensis (G6) in Neuquén, and that control strategies may have to be adapted to local molecular epidemiology to improve the control of parasite transmission.

Usefulness and validation of a coproantigen test for dog echinococcosis screening in the consolidation phase of hydatid control in Neuquén, Argentina.

Hydatidosis is endemic in Neuquén, Patagonia, Argentina, even though sanitary authorities have been performing a control programme since 1970. At present, the programme is in consolidation phase, and dogs have being evaluated by arecoline purgation. The aims of this study were to evaluate diagnostic performance of a coproantigen (CAg) ELISA test developed "in house" and to assess CAg detection in prepatent period. We examined 8 dogs experimentally infected with Echinococcus granulosus and 403 rural dogs in an endemic area in Neuquén using CAg ELISA test and arecoline purgation. Within the experimental dog group, sensitivity and specificity of the test were 93.6% and 88.5% respectively. In rural dogs group, the overall prevalence of canine echinococcosis was 3.7% using arecoline purgation and 12.4% by the CAg test; sensitivity and specificity of the test using arecoline purge as standard were 73.3% and 89.9% respectively. Possible cross reactions in CAg test were evaluated in rural dogs: CAg was undetectable in 96.4% of the dogs infected only with taeniids non-E. granulosus, and in 90.1% of dogs infected with non-taeniid helminths. The CAg test could detect infections within prepatent period and produced negative results after worm expulsion. Our test showed adequate diagnostic performance with experimentally and naturally infected dogs, in the epidemiological situation of Neuquén. Employment of this sensitive and practical method for surveillance in the control programme in Neuquén would improve screening of canine echinococcosis by detecting infected dogs even with low burdens or within prepatent period.

Erythromycin-resistant Streptococcus pyogenes in Argentina

Erythromycin (ERY) resistance in Streptococcus pyogenes has recently emerged as a problem of growing concern all through the world. We are presenting the comparison of results of the continuous surveillance of erythromycin resistance in S. pyogenes performed since 1989 in the Hospital de Pediatría J.P.Garrahan of Buenos Aires City, with independently observed rates in other five centers of Buenos Aires and seven centers of six other Argentinian cities, obtained between 1999 and 2001. A significant increase of erythromycin resistance was observed among S. pyogenes isolated in the Hospital Garrahan (6.6% in 1998-1999 to 9.9% in 2000). Similar trends were also detected in other centers of other Argentinian cities when recent data were compared to results of a multicenter study performed in 1995. However, lower rates of resistance were recorded in Mendoza, Cipolletti and Neuquén in comparison with data of 1995, 1998 and 1998 respectively. The reason of such decreasing resistance rates deserves to be investigated. The average of ERY-resistance rates obtained in the surveyed centers was 6.7% (range 0.5-14.1%). Control of antimicrobial use should be performed to warrant the future effectiveness of macrolide antibiotics regarding the positive association between use and resistance. These results also suggest that susceptibility tests for macrolides should be performed whenever S. pyogenes is isolated in Argentina.

La resistencia a la eritromicina en Streptococcus pyogenes ha emergido en los últimos tiempos como un problema creciente en todo el mundo. En este trabajo se presenta la comparación de los resultados de la vigilancia continua de la resistencia a la eritromicina que se viene realizando en el Hospital de Pediatría J.P.Garrahan de Buenos Aires desde 1989, con resultados independientes de otros cinco centros de la ciudad de Buenos Aires y siete de otras seis ciudades argentinas, obtenidos entre 1999 y 2001. Se observó un aumento significativo en el Hospital Garrahan (6.6% en1998-1999 a 9.9% en el año 2000) y una tendencia similar en otros centros de diversas ciudades argentinas si secomparan estos datos con los de un estudio multicéntrico realizado en 1995. No obstante, se registraron menoresporcentajes de resistencia en Mendoza, Neuquén y Cipolletti, en relación a lo hallado en 1995, 1998 y 1998respectivamente. La razón de esta disminución merece ser investigada. El porcentaje promedio de resistencia aeritromicina obtenido en los distintos centros participantes de este estudio fue de 6.7% (rango 0.5-14.1%). Debeefectuarse un control en el uso de estos antibióticos para garantizar la efectividad futura de los macrólidos, teniendo en cuenta la asociación estrecha entre uso y resistencia. Estos resultados sugieren que deberían realizarse pruebas de sensibilidad a los macrólidos para todos los aislamientos de S. pyogenes en la Argentina.

Intestinal parasites and the environment: frequency of intestinal parasites in children of Neuquén, Patagonia, Argentina.

The frequency of intestinal parasites (IP) in 69 children between 2 and 14 years of age was studied within the city of Neuquén, Patagonia, Argentina in relation to socioeconomic, cultural and environmental conditions. Soil type was determined and contamination with IP was investigated in 75 soil samples. Frequency of IP in children was 50.7%. Blastocystis hominis was the most frequent species (24.6%). Simultaneous infection with 2 to 4 species was found in 47,5% of the infected children. Statistical association was found between parasitic infection and family hygienic level (p < 0.001). Socioeconomic level was defined as lower middle class, however, infrastructure and public services were adequate. The climate is continental semiarid and the soil is sandy with a low organic matter level. Intestinal protozoan organisms were found in 33.3% of soil samples and Sarcocystis sp. was the most frequent species (14.6%). The parasites present in soil are related to the environmental conditions that allow their viability and development. Socioeconomic and cultural factors are important for the appearance and spread of IP in communities where sanitary conditions and infrastructure are adequate.

[Streptococcus pyogenes: penicillin and erythromycin susceptibility in the cities of Neuquen and Cipolletti]. / Streptococcus pyogenes: sensibilidad a penicilina y eritromicina en las ciudades de Neuquen y Cipolletti.

Penicillin resistance has not yet been detected in Streptococcus pyogenes. However macrolide-resistant streptococci have emerged in several countries. Only low rates of erythromycin-resistant S. pyogenes were reported in Argentina, with the exception of a 11.1% observed in Mendoza. The aim of the present study was to determine the susceptibility to penicillin and to erythromycin of 251 consecutive clinically-significant isolates of S. pyogenes obtained from four centers of Cipolletti and Neuquén during the period April-December 1998. The double disk test with erythromycin and clindamycin disks was employed as a screening method to detect ERY-resistant streptococci and to determine the phenotype of macrolide resistance. Disk diffusion was also employed for determining penicillin susceptibility. Macrolide-resistant isolates were also tested for penicillin, ceftriaxone, erythromycin, clindamycin and azithromycin susceptibility by the agar dilution method. Additionally they were also tested for erythromycin susceptibility by E-test (AB Biodisk, Solna, Sweden). All streptococci studied were susceptible to penicillin and thirty of them (12.0%) were resistant to erythromycin. All these resistant isolates were also resistant to azithromycin but susceptible to ceftriaxone and clindamycin. They showed the phenotype M (probably efflux-mediated mechanism) and the MICs of erythromycin ranged between 8 and 16 micrograms/ml. According to these results we conclude that in spite of universal susceptibility to penicillin in S. pyogenes, macrolide resistance is a matter of concern in Neuquén and Cipolletti. At least in those cities it appears to be necessary to routinely perform macrolide susceptibility tests in beta-hemolytic streptococci.