Viable Leishmania parasites in the absence of an in vitro IFN-γ response in asymptomatic carriers

ABSTRACT Asymptomatic infection (the absence or inapparent signs and symptoms) has been observed in many endemic areas of leishmaniasis, however, little is known about the parasitological and immunological factors associated with this type of infection. This study aimed to identify the in vitro expression of IFN-γ in asymptomatic carriers of viable Leishmania parasites. Asymptomatic infection was identified using the Montenegro skin test in an at-risk population from Yucatan, Mexico. Parasite viability was evinced in the blood by 7SL RNA transcripts amplification. The expression of mRNA IFN-γ was analyzed in peripheral blood mononuclear cells stimulated with soluble Leishmania antigen, using RT-qPCR. Parasite viability was observed in 33.3 % (5/15) of asymptomatic subjects. No differences were found in the expression of IFN-γ between asymptomatic and healthy subjects, and no correlation was found between the presence of viable parasites and the expression of IFN-γ. This study demonstrates the persistence of Leishmania parasites in the absence of an in vitro IFN-γ response in asymptomatic carriers from Mexico.

Rickettsia spp. en garrapatas (Acari: Ixodidae) que infestan perros de una comunidad rural con antecedentes de rickettsiosis, Yucatán, México / Rickettsia spp. in ticks (Acari: Ixodidae) infesting dogs from a rural community with rickettsial diseases reports, Yucatan, Mexico

RESUMEN Introducción: Las bacterias del género Rickettsia son agentes causales de las rickettsiosis, enfermedades zoonóticas transmitidas por ectoparásitos. En Yucatán, ocurrió un brote en habitantes de Bolmay, Valladolid; sin embargo, no se identificó el probable artrópodo vector. Objetivo: Analizar la presencia de Rickettsia spp. en garrapatas que infestan perros domésticos de Bolmay. Material y métodos: Se trabajaron 105 viales con hasta ocho garrapatas. Se extrajo ADN de los ectoparásitos, posterior a la identificación del estadio de desarrollo vital, sexo, género y especie. Se realizaron dos PCR para aislar fragmentos de los genes htrA (17-kDa) y rOmpB, pertenecientes a Rickettsia spp. Los productos positivos fueron secuenciados y analizados con la herramienta BLAST y el algoritmo Megablast. Resultados: Se utilizaron 291 garrapatas de los géneros Amblyomma (55.7%, 162/291), Rhipicephalus (34%, 99/291) e Ixodes (10.3%, 30/291), y las especies Rhipicephalus sanguineus sensu lato, Ixodes affinis y Amblyomma mixtum. La positividad por PCR fue de 11.4% (12/105) para los géneros Amblyomma (66.7%, 8/12), Rhipicephalus (25%, 3/12) e Ixodes (8.3%, 1/12), y las especies A. mixtum, Rh. sanguineus s. l. e I. affinis. Se identificó ADN rickettsial en ninfas, larvas, adultos, machos y hembras. Cada análisis BLAST arrojó un 96% de cobertura e identidad con varias secuencias de Rickettsia spp. como Rickettsia typhi, Rickettsia felis y Rickettsia prowazekii, por lo que no fue posible determinar la especie infectante. Conclusión: Las garrapatas que infestan perros de Bolmay, probablemente están involucrados en el ciclo de transmisión de Rickettsia spp. Se presenta la primera evidencia molecular de Rickettsia spp. en garrapatas I. affinis de Yucatán, México.

ABSTRACT Introduction: Bacteria of the Rickettsia genus are causal agents of the rickettsial diseases, zoonoses transmitted by ectoparasites. In Yucatan, in inhabitants from Bolmay an outbreak occurred; however, the probable vector was not identified. Objective: To analyze the Rickettsia spp. presence in ticks infesting domestic dogs from Bolmay. Material and methods: We used 105 vials with up to eight ticks. Total DNA from the ectoparasites was extracted, after the identification of the life stages, sex, gender, and species. Two PCR to isolate fragments of the htrA (17-kDa) and rOmpB genes belonging to Rickettsia spp., were performed. The positive products were sequenced and analyzed using the BLAST tool and the Megablast algorithm. Results: 291 ticks of the genera Amblyomma (55.7%, 162/291), Rhipicephalus (34%, 99/291), and Ixodes (10.3%, 30/291), and the species Rhipicephalus sanguineus sensu lato, Ixodes affinis, and Amblyomma mixtum, were used. The PCR positivity was 11.4% (12/105) for the genera Amblyomma (66.7%, 8/12), Rhipicephalus (25%, 3/12), and Ixodes (8.3%, 1/12), and the species A. mixtum, Rh. sanguineus s. l., and I. affinis. Rickettsial DNA in nymph, larva, adult, males, and females, were identified. Each BLAST analysis showed an identity and coverage of 96% with several Rickettsia spp. sequences, such as Rickettsia typhi, Rickettsia felis and Rickettsia prowazekii, so it was not possible to determine the infecting species. Conclusion: Ticks infesting dogs from Bolmay are probably involved in the transmission cycle of Rickettsia spp. The first molecular evidence of Rickettsia spp. in I. affinis ticks from Yucatan, Mexico, is presented.

Caso fulminante de rickettsiosis (Rickettsia rickettsii) en una lactante del sureste de México / Fatal case of rickettsiosis in a toddler from southeastern Mexico

La fiebre manchada de las Montañas Rocosas es una enfermedad ocasionada por Rickettsia rickettsii, una bacteria transmitida por garrapatas infectadas, y que se caracteriza por fiebre, exantema, artralgias y mialgias, aunque, ocasionalmente, su presentación es inespecífica. Debido a que su evolución asemeja otras enfermedades exantemáticas, como dengue o chikungunya, su diagnóstico no es de primera intención, a pesar de que países como México tienen las características ecológicas y socioeconómicas propicias para su transmisión, con índices de mortalidad hasta de 30% en pacientes pediátricos. Esta elevada mortalidad se asocia a diagnósticos y terapia retrasados debido al desconocimiento médico acerca de la enfermedad, lo que propicia la aparición de formas atípicas y fulminantes de fiebre manchada de las Montañas Rocosas. El objetivo del presente trabajo es describir un caso clínico fulminante de fiebre manchada de las Montañas Rocosas para que sea considerada en el diagnóstico diferencial, lo cual impactaría directamente en los índices de mortalidad.

Rocky Mountain spotted fever is a disease caused by Rickettsia rickettsii, a bacteria transmitted by infected ticks. It is characterized by fever, exanthema, arthralgias and myalgias; but sometimes its clinical presentation is non specific. Due to its similarities with other exanthematic diseases like dengue or chikungunya, Rocky Mountain spotted fever is not a first line diagnosis, even though countries like Mexico show the ecologic and socioeconomic characteristics that favor its transmission, with a 30% mortality rate among pediatric patients. This mortality rate has been associated to a delayed diagnosis and therapy, due to a poor knowledge among physicians regarding this disease; this favors the occurrence of atypical and fulminant cases. The objective of this work is to describe a fulminant case of Rocky Mountain spotted fever, expecting that this disease could be later considered among the differential diagnosis which could directly impact its mortality rate.

Mecanismos de resistencia antifúngica de los azoles en Candida albicans. Una revisión / Mechanisms of antifungal resistance of azoles in Candida albicans. A review

Resumen Candida albicans es una levadura comensal capaz de causar una infección oportunista en hospederos susceptibles denominada candidiasis. El tratamiento para combatir la candidiasis puede ser tópico o sistémico según el tipo de infección, los antifúngicos más utilizados son los derivados imidazólicos (fluconazol, itraconazol, ketoconazol, miconazol etc.), sin embargo en la actualidad se observa una disminución en la efectividad de estos medicamentos, es decir, un fenómeno de resistencia de parte del microorganismo a estos fármacos, esto debido principalmente, al surgimiento de levaduras resistentes, a la aparición de nuevas especies patógenas, a la prescripción irracional de antimicóticos como profilaxis y al aumento de las dosis terapéuticas. Existen dos mecanismos por los que Candida puede adquirir resistencia a un azol. El primero es por mutaciones moleculares de la enzima diana del antifúngico, como la alteración de las enzimas relacionadas en la síntesis del ergosterol y el segundo por la alteración en las bombas de expulsión: ATP-binding cassette (ABC) y facilitadores mayores (MF). En este trabajo se resumen los principales mecanismos de resistencia en Candida y la importancia de hacer pruebas de susceptibilidad con el fin de brindar un tratamiento adecuado para este tipo de infecciones oportunistas.

Abstract Candida albicans is a commensal yeast capable of causing an opportunistic infection called candidiasis in susceptible hosts. Treatment to combat Candida may be topical or systemic according to the type of infection and the imidazole derivatives (fluconazole, itraconazole, ketoconazole, miconazole, etc.) are the antifungals most widely used. However, resistance to these drugs is observed by a decrement in their effectiveness. This is mainly due to the emergence of resistant yeasts and of new pathogenic species, as well as to the irrational prescribing of antifungal prophylaxis and the use of higher therapeutic doses. There are two mechanisms by which Candida can acquire an azole resistance, the first is by molecular mutations of antifungal target enzyme, as the alteration of enzymes related to the synthesis of ergosterols and the second by change in the efflux pumps, such as those of ATP-binding cassette and the higher facilitators. In this work the main mechanisms of resistance to Candida and the importance of performing susceptibility tests in order to provide an adequate treatment for this type of opportunistic infections are summarized.