Epidemiologic profile and clinical course of four confirmed rickettsiosis cases in Southern Mexico during 2016.

Domestic animals can carry ticks or fleas, which constitute common vectors of rickettsial infections. The contact with them should be considered as suggestive of rickettsial infections in symptomatic patients. Misdiagnosis might occur in regions where other vector-borne diseases are endemic. Anamnesis is essential for an accurate clinical diagnosis.

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.

Dengue Patients Treated with Doxycycline Showed Lower Mortality Associated to a Reduction in IL-6 and TNF Levels.

OBJECTIVE: To determine the effect of doxycycline treatment on cytokine levels, including tumor necrosis factor (TNF) and interleukin 6 (IL-6), and mortality in dengue patients at high risk of complication. METHODS: A group of dengue hemorrhagic fever patients (n=231) were randomized to receive either standard supportive care or supportive care in addition to oral doxycycline twice daily for 7 days. Dengue virus infection was confirmed by PCR using multiple primers. Serum samples were obtained at days 0, 3, 5 and 7 and tested for levels of TNF and IL-6. RESULTS: Doxycycline-treated group presented a 46% lower mortality than that observed in the untreated group (11.2% [13/116] vs 20.9% [24/115], respectively, p=0.05). Moreover, administration of doxycycline resulted in a significant (p<0.01) decrease in levels of TNF and IL-6 versus controls in the tests performed during follow-up (day 3, 5 and 7). Patients who died in both groups possessed significantly (p<0.01) higher levels of TNF and IL-6 compared to those who survived at all-time points. CONCLUSION: The above findings suggest that doxycycline can provide a clinical benefit to dengue patients at high risk of complications. This effect could be mediated by decreasing pro-inflammatory cytokine levels.

Human rickettsialpox, southeastern Mexico.

The detection of Rickettsia akari in 2 human patients increased the diversity of rickettsioses affecting the public health in the southeast of Mexico. Rickettsialpox should be considered in the differential diagnosis with other febrile illnesses for the correct diagnosis and accurate treatment of this potential threat to human health.

Murine typhus in child, Yucatan, Mexico.

A case of murine typhus in Yucatan was diagnosed in a child with nonspecific signs and symptoms. The finding of Rickettsia typhi increases the number of Rickettsia species identified in Yucatan and shows that studies are needed to determine the prevalence and incidence of rickettsioses in Mexico.

A dog naturally infected with Rickettsia akari in Yucatan, México.

Rickettsia akari is the causative agent of rickettsialpox, a primarily urban mite-borne rickettsiosis that is encountered in the United States and in a few countries around the world. Its vector is the mite Liponyssoides sanguineus, which is found on rats and mice, which serve as reservoirs for the disease. In this work we report a severe animal case of R. akari infection with two unusual features: R. akari was found in a dog, and its potential vector was a tick.

Short report: Rickettsia felis outer membrane protein A: a potential tool for diagnosis of patients with flea-borne spotted fever.

Rickettsia felis infection in humans has been detected worldwide, causing an illness that could be confused with other viral and bacterial infections such as dengue fever. Despite the high incidence of infection in humans, reservoirs, and vectors, the definitive diagnosis of R. felis infection currently requires polymerase chain reaction and sequencing because its antigens are closely related to other rickettsiae, making serologic diagnosis problematic. In this work, we report the immune reactivity of sera from four patients infected with R. felis with recombinant peptides representing regions of outer membrane protein A of R. felis.

An increase in human cases of spotted fever rickettsiosis in Yucatan, Mexico, involving children.

The first human case of infection caused by Rickettsia in Yucatan was detected in 1996, and it was determined that the species was R. felis. Since then, passive epidemiologic surveillance was implemented to search for human cases in the public hospitals of the state, and in 2005, the first human case of Rocky Mountain spotted fever was detected. During the following 2 years, eight new confirmed cases and one probable case were identified. Seven cases involved children younger than 12 years of age, with a fatal outcome in three of the cases. Children are a particularly vulnerable population for this serious emerging infection.

Rickettsia felis as emergent global threat for humans.

Rickettsia felis is an emergent pathogen belonging to transitional group rickettsiae. First described in 1990, R. felis infections have been reported to occur worldwide in fleas, mammals, and humans. Because clinical signs of the illness are similar to those of murine typhus and other febrile illnesses such as dengue, the infection in humans is likely underestimated. R. felis has been found throughout the world in several types of ectoparasites; cat fleas appear to be the most common vectors. R. felis infection should be considered an emergent threat to human health.

Fatal human infection with Rickettsia rickettsii, Yucatán, Mexico.

The first fatal Rickettsia rickettsii infection was diagnosed in the southwest of Mexico. The patient had fever, erythematous rash, abdominal pain, and severe central nervous system involvement with convulsive crisis. The diagnosis of R. rickettsii infection was established by immunohistochemistry and specific polymerase chain reaction.

Transcription of the Rickettsia felis ompA gene in naturally infected fleas.

Rickettsia felis is maintained transovarially in Ctenocephalides felis fleas in a widespread geographic distribution and is transmitted to humans and animals, including opossums. This rickettsia is phylogenetically a member of the spotted fever group, most closely related to Rickettsia akari and R. australis. An unusual feature of this rickettsia is that the gene for the outer membrane protein A (OmpA) is interrupted by stop codons. To determine if this putatively dying gene is expressed, mRNA was extracted from laboratory-maintained, R. felis-infected cat fleas. Reverse transcriptase-polymerase chain reaction amplification of three segments of the ompA gene indicated that mRNA of ompA is actively transcribed in fleas. The cDNA sequences expressed represented mRNA of the first 1860-basepair segment of ompA, which includes domains I and II, part of domain III, the region from site 1836 to site 2180, despite the presence of several stop codons, and the open reading frame from site 2788 to site 3837. The detected sequences showed several differences in the amino acid composition when compared with the previously reported sequence.

Kinetoplast DNA-binding protein profile in the epimastigote form of Trypanosoma cruzi.

BACKGROUND: The Trypanosomatidae family possesses one of the most unusual DNAs found in nature: the kinetoplast genome. It consists of a few dozen maxicircles that encode for some subunits of mitochondrial enzymes and rRNAs in a cryptic pattern and thousands of minicircles that encode for the guide RNAs (gRNAs), all catenated and constituting a dense network. The complexity of kinetoplast genome based on its intricate DNA structure is well known; however, only a small number of proteins associated with kinetoplast DNA (kDNA) have been described, and the majority are related with the replication process. METHODS: We describe the protein profile obtained using formaldehyde as a cross-linking agent to obtain the kinetoplast DNA-protein complex, and Southwestern assay to identify the kDNA binding proteins present in the complex. RESULTS: We identified seven proteins eluted from the kDNA complex fixed by formaldehyde. Polyclonal antiserum developed against the kDNA-protein complex recognized only four proteins in crude extracts of epimastigote stage, suggesting immunogenic differences among these proteins and/or their availability in the kinetoplast genome. Southwestern assay using minicircle fragments showed nine kDNA binding proteins in crude extracts of Trypanosoma cruzi epimastigote. CONCLUSIONS: We describe several proteins associated with the kDNA. Some could be involved in the essential process for parasite life and also could be a good target for drug or vaccine development. The results contribute to understanding the organization of the kinetoplast genome.

Importancia de la caracterización de cepas de Trypanosoma cruzi / The importance of the characterisation of Trypanosoma cruzi strains

El trypanosoma cruzi (T. cruzi) es un protozoario hemoflagelado, considerado el agente causal de la enfermedad de Chagas y es transmitido a los hospederos mamíferos por medio de insectos vectores del género Triatoma. El T. cruzi presenta un pleomorfismo natural, al cual se ha atribuido a la diferencia de severidad con que se presenta la enfermedad en el hospedero humano y otros mamíferos. Considerando este aspecto han sido varios los trabajos sobre caracterización de cepas de T. cruzi, abarcando aspectos biológicos, bioquímicos y moleculares para poder establecer un método de clasificación de las diferentes cepas de dicho parásito, de manera que las cepas que pertenezcan a un mismo grupo compartan estos aspectos y así una cepa pudiera ser representativa de ese grupo, simplificando los estudios a realizar. Esta revisión pretende dar un panorama de los diferentes métodos de caracterización de la cepas T. cruzi, para tratar de agruparlas para su mejor estudio y control