Jorge Vázquez

Species distribution and antifungal susceptibility of bloodstream fungal isolates in paediatric patients in Mexico: a nationwide surveillance study

OBJECTIVES To establish the species distribution and in vitro susceptibilities of 358 bloodstream fungal isolates from paediatric patients in Mexico. METHODS Isolates were collected during a 2 year surveillance programme in 14 medical centres in 10 Mexican states. A molecular approach was used to determine the Candida parapsilosis species complex. In vitro susceptibility to amphotericin B, fluconazole, voriconazole, itraconazole, posaconazole, caspofungin, anidulafungin and micafungin was determined according to CLSI procedures. Species-specific clinical breakpoints for fluconazole, voriconazole and echinocandins were applied. RESULTS Candida spp. accounted for 98.33% of fungaemias, including 127 Candida albicans isolates, 127 C. parapsilosis complex isolates (121 C. parapsilosis sensu stricto, 4 Candida orthopsilosis and 2 Candida metapsilosis strains) and 72 Candida tropicalis isolates. C. albicans and C. parapsilosis complex were the species predominant in neonates (48 cases each; 41.02%). C. parapsilosis complex was also the predominant species in patients 1 month to <2 years of age (P = 0.007). In contrast, C. albicans was the most frequent species in patients aged 2 to <12 years (P = 0.003). Antifungal resistance was rare among the subset of isolates. Candida glabrata showed the highest resistance rate to amphotericin B (1/9 isolates), fluconazole (1/9 isolates) and itraconazole (2/9 isolates). CONCLUSIONS The species distribution differed with the age of the patients, with C. albicans and C. parapsilosis complex being the most commonly isolated species. C. glabrata showed the highest resistance rate to amphotericin B, fluconazole and itraconazole. This is the first study of fungaemia episodes in Mexican children.

Demography, density, and survival of an endemic and near threatened cottontailSylvilagus cunicularius in central Mexico

A 3-year live trapping investigation was carried out in a temperate forest in central Tlaxcala, México from 2002 to 2004. During a total of 504 trap nights, 87Silvilagus cunicularius Waterhouse, 1848 individuals were captured and marked, and age-specific survival models using demographic parameters were tested using the JOLLYAGE program. We evaluated population density of this species over a 1-year period. The age structure of the population varied among years, and the proportion of adults was relatively constant among years, whereas the proportion of juvenile showed high fluctuations. The sex ratio of juveniles that were recaptured as adults, did not differ from unity neither did the sex ratio for adults. We found no sex bias among cottontails during all 3 years of the study. When data for both sexes were combined, mean survival probability of juveniles was lower than that of adults. Although our line transect counts showed a mean density of 27 ± 5.4 individuals per km2, the obtained results from trapping suggests that this species is low in abundance at La Malinche. Further studies are needed to evaluate demographical aspects of this species at different protected and unprotected areas to obtain robust information about their status.

Seasonal reproduction in Mexican cottontail rabbitsSylvilagus cunicularius in La Malinche National Park, central Mexico

Mexico has the largest number of leporid species in the world but most have been little studied. The endemic Mexican cottontailSylvilagus cunicularius (Waterhouse, 1848) is the largest Mexican rabbit, and although not in danger of extinction, it is increasingly threatened. Since little is known about its annual pattern of reproduction, we studied this species in La Malinche National Park, central Mexico, whereS. cunicularius is still common. For 7 years we trapped and marked 157 different individuals (plus 59, sometimes multiple, re-captures), determining across the year the percent of adult females that were reproductively active, the number of juveniles as a percent of total captures, and the percent of males with scrotal testes. Reproductively active females were present throughout the year but with a notable peak from March to October, juveniles were present throughout the year but with a peak from September to December, and adult males had scrotal testes throughout the year with no seasonal change in testis length. Onset of the breeding season coincided with increasing day length and temperature, and births with high rainfall. Thus, in central MexicoS. cunicularius breeds throughout the year but particularly during the warmer, wetter summer months. We therefore recommend that hunting only be permitted from November to February.

Response of two sympatric carnivores to human disturbances of their habitat: the bobcat and coyote

Information about human land uses, producing the least impact on wildlife and their habitats, is crucial to develop management strategies allowing coexistence between human beings and wildlife. We investigated the responses of the bobcat (Lynx rufus) and the coyote (Canis latrans) to different types of human activity by assessing the abundance, habitat use, and activity patterns of these species in response to extraction of firewood, grazing, and crop farming within their habitat. Photographic records of both carnivores were obtained from 18 camera-trap stations, distributed evenly within these three types of habitat disturbances. The highest relative abundance index for both carnivores was obtained at firewood extraction sites, followed by grazing sites, and croplands. The probability of carnivore sightings varied between species by type of disturbance and by season. The probability of bobcat sightings was highest within firewood extraction sites, with no effect of season, whereas that of the coyote was highest during winter, with no effect of type of human disturbance. An analysis of habitat use revealed that both carnivores avoided cropland sites. Activity patterns were similar, which suggests an absence of temporal segregation between these species; moreover, the activity patterns of both carnivores seems to be affected by intensity of human activities. Preference for woodland habitats by both carnivores denotes that firewood extraction is the disturbance that least affects bobcat and coyote populations; therefore, this kind of human activity could be the least impacting type of disturbance for the coexistence between humans and these carnivore species.

Optimización de la Eficiencia Térmica de un Motor Robinson Aplicando el Modelo Senft-Schmidt-Petrescu

Se presentan los resultados de la optimizacion de la eficiencia termica de un motor Robinson aplicando el modelo Senft-Schmidt-Petrescu. Este se fundamenta en el acoplamiento de los modelos de Senft-Schmidt y de Petrescu, usados para el calculo de la potencia en motores de ciclo Stirling. El modelo propuesto involucra tanto parametros termodinamicos como geometricos y permite estimar en su conjunto las perdidas de presion por friccion y por estrangulamiento del flujo. Tomando como base los datos del prototipo de un motor Robinson de aproximadamente 2 W de potencia, se analizaron teoricamente sus parametros principales y se optimizo su eficiencia termica en funcion de la minima generacion de entropia. Despues de realizada la optimizacion, la eficiencia termica del motor aumento a mas del doble. Se concluye que el modelo Senft-Schmidt-Petrescu propuesto puede ser util en el analisis y rediseno de motores Robinson.