Humberto Guerra

Resazurin Microtiter Assay Plate: Simple and Inexpensive Method for Detection of Drug Resistance in Mycobacterium tuberculosis

ABSTRACT A method for detecting multidrug-resistant Mycobacterium tuberculosis by using a reduction of resazurin is described. Eighty clinical isolates were evaluated against isoniazid and rifampin; results at 7 days were compared with those of the proportion method. Specificity and sensitivity were excellent. The method is simple, inexpensive, and rapid and might be used with other antituberculosis drugs.

Natural Leishmania infection of Lutzomyia spp. in Peru

Natural infection of Lutzomyia spp. with Leishmania was studied with the aid of the polymerase chain reaction (PCR) in Chaute, Lima, Perú, a locality endemic for Andean cutaneous leishmaniasis (uta). The PCR, with primers specific for the L. braziliensis complex, was applied to sandfly pools. Sandflies were sampled from April 1990 to May 1991 with CDC light traps in homes, and from near homes with a Shannon trap using protected human bait. Lu. verrucarum (4 pools) and Lu. peruenis (2 pools) from the anthropophilic collections, and Lu. verrucarum (2 pools) from indoors were found to be infected with Leishmania. The majority of infected sandflies were recorded mainly in April 1991 (4 pools), coinciding with the highest sandfly densities and the maximum number of new cases of uta (7). Non-infected sandflies were found from May to October 1990 and January to March 1991. Thus, these 2 sandfly species play a role in the spread of leishmaniasis among humans and other animals in Chaute.

The brucellae and their success as pathogens.

Brucellae are tiny, aerobic, slow growing, catalase and oxidase positive Gram negative coccobacilli or small rods, which may reach man through exposure to tissues of mammalian hosts via cuts or aerosols, or as food infections mostly through dairy products. As parasites brucellae are extraordinarily successful, causing very long-lasting infections in all mammalian social animals, such as ungulates, canids, and rodents; recently they have been found to also cause disease in pinnipeds and cetaceans. Brucellae as members of the alpha Proteobacteria, have suffered major losses of genomic material as they adapted to their facultative intracellular parasite role, and are able to initiate infection with minimal disturbance of the innate immune system, thus reaching a privileged intracellular niche where they multiply. Brucellae are likely to be among the toughest organisms to control through public health and agricultural policies, even involving detection-slaughter strategies.

Identification of bloodmeal sources of Lutzomyia spp. in Peru.

Bloodmeal sources of Lutzomyia spp. were determined, using the bloodmeal analysis precipitin test, in Chaute, Lima, Peru, an area endemic for cutaneous leishmaniasis (uta). From April 1990 to May 1991, sandflies were sampled in and around the village houses, with CDC light traps and a Shannon trap with protected human bait, respectively. Overall, 1424 sandflies were collected engorged. In indoor collections, human blood (N = 275) was the most frequent bloodmeal found, followed by cow (171) and cat (152). The most frequent bloodmeals of the flies caught in the Shannon trap collections were from cow (31), man (23) and cat (23). Of the two predominant sandfly species in the area, Lutzomyia peruensis was more anthropophilic than Lu. verrucarum (chi 2 = 14.13, P < 0.001). The sandflies from Chaute appear to be opportunistic feeders; 16 different hosts were identified. There was evidence of bloodmeals from more than one host in each of 151 sandflies, including bloodmeals containing blood from an animal only present within the houses mixed with blood from animals only present in the corrals near the house. Some sandflies must therefore have flown from the corrals to the houses (or vice versa) to take the last bloodmeals before their capture.

Surveillance of bacterial pathogens associated with acute diarrhea in Lima Peru.

OBJECTIVESnA study was conducted in Lima, Peru, from January to April 1995, to determine the bacterial pathogens associated with acute diarrhea in adults, their susceptibility to common antimicrobials, the risk factors involved in cholera transmission, and the best clinical predictors of cholera.nnnMETHODSnA random sample of adult patients with acute diarrhea was studied. Epidemiologic and clinical data and risk factors to acquire diarrheal diseases were evaluated. Identification of bacteria and susceptibility to antimicrobials were determined.nnnRESULTSnThe study included 336 patients. Vibrio cholerae O1 (52.7%), Shigella spp. (4. 8%), and Salmonella spp (2.7%) were the pathogens most commonly isolated. No resistance to antimicrobials was observed. Patients with cholera had less access to municipal water (P = 0.0018) and were less likely to have homes connected to a sewage system (P = 0. 0003) or to have indoor toilet facilities (P = 0.0001) than those without cholera. Liquid stools (odds ratio [OR] = 16.51; confidence interval [CI] = 13.71-19.02; P = 0.003), severe dehydration (OR = 2. 48; CI = 1.57-3.38; P = 0.0083), generalized cramps (OR = 4.63; CI = 3.10-6.17, P < 0.0001), and washerwomans hands (OR = 2.45; CI = 1. 55-3.34; P = 0.017) were the best clinical predictors of cholera in this setting.nnnCONCLUSIONSnCholera is still prevalent in Lima, and people living in environments with low sanitary conditions are especially at risk. Clinical signs of severe dehydration and liquid stools were the best predictors of cholera.

Novel hypertonic saline–sodium hydroxide (HS–SH) method for decontamination and concentration of sputum samples for Mycobacterium tuberculosis microscopy and culture

This study evaluated a new decontamination and concentration (DC) method for sputum microscopy and culture. Sputum samples from patients with suspected pulmonary tuberculosis (TB) (n=106) were tested using the proposed hypertonic saline-sodium hydroxide (HS-SH) DC method, the recommended N-acetyl-L-cysteine-sodium citrate-sodium hydroxide (NALC-NaOH) DC method and unconcentrated direct smear (Ziehl-Neelsen) techniques for the presence of mycobacteria using Löwenstein-Jensen culture and light microscopy. Of 94 valid specimens, 21 (22.3%) were positive in culture and were further characterized as Mycobacterium tuberculosis. The sensitivity for acid-fast bacilli (AFB) smears was increased from 28.6% using the direct method to 71.4% (HS-SH) and 66.7% (NALC-NaOH) using DC methods. Both concentration techniques were highly comparable for culture (kappa=0.794) and smear (kappa=0.631) for AFB. Thus the proposed HS-SH DC method improved the sensitivity of AFB microscopy compared with a routine unconcentrated direct smear; its performance was comparable to that of the NALC-NaOH DC method for AFB smears and culture, but it was methodologically simpler and less expensive, making it a promising candidate for evaluation by national TB control programmes in developing countries.

Rhinoscleroma: eight Peruvian cases

Rhinoscleroma is a rare infection in developed countries; although, it is reported with some frequency in poorer regions such as Central Africa, Central and South America, Eastern and Central Europe, Middle East, India and Indonesia. Nowadays, rhinoscleroma may be erroneously diagnosed as mucocutaneos leishmaniasis, leprosy, paracoccidioidomycosis, rhinosporidiasis, late syphilis, neoplasic diseases or other upper airway diseases. From 1996 to 2003, we diagnosed rhinoscleroma in eight patients attended in the Dermatologic and Transmitted Diseases service of Cayetano Heredia National Hospital, in Lima, Peru. The patients presented airway structural alterations producing nasopharyngeal, oropharyngeal and, in one patient, laryngeal stenosis. Biopsy samples revealed large vacuolated macrophages (Mikulicz cells) in all patients. Ciprofloxacin 500 mg bid for four to 12 weeks was used in seven patients and oxytetracycline 500 mg qid for six weeks in one patient. After follow-up for six to 12 months the patients did not show active infection or relapse, however, all of them presented some degree of upper airway stenosis. These cases are reported because of the difficulty diagnosing the disease and the success of antibiotic treatment.

Gelatin particle indirect agglutination and enzyme-linked immunosorbent assay for diagnosis of strongyloidiasis using Strongyloides venezuelensis antigen

Routine microscopical examination of stool specimens for diagnosis of strongyloidiasis is insensitive and serological methods using Strongyloides stercoralis antigen are at present not available for field studies. We evaluated 2 techniques, enzyme-linked immunosorbent assay (ELISA) and gelatin particle indirect agglutination (GPIA), using an antigen obtained from the rodent parasite, S. venezuelensis. Fifty-four Peruvian patients with different clinical forms of strongyloidiasis were studied: 12 asymptomatic, 31 symptomatic, and 11 hyperinfection cases. Our results demonstrate that both ELISA and GPIA using S. venezuelensis antigen are useful for diagnosis of strongyloidiasis, with sensitivities of 74.1% and 98.2%, respectively and a specificity of 100% for both techniques. We found that GPIA is a highly sensitive test for patients with suspected chronic infection and/or hyperinfection. In the hyperinfection cases, significantly lower concentrations of specific immunoglobulin antibodies and eosinophils (P < 0.001) were found compared with the asymptomatic and symptomatic cases.

Prevalence and risk factors associated with pediculosis capitis in an impoverished urban community in lima, peru.

Background: Pediculosis capitis is a ubiquitous parasitic skin disease associated with intense pruritus of the scalp. In developing countries it frequently affects children and adults, but epidemiological data at the community level are rare. Objectives: To assess prevalence and risk factors associated with pediculosis capitis in a resource-poor community in Lima, Peru. Materials and Methods: In total, 736 persons living in 199 households in a circumscribed neighbourhood were examined for head lice and nits by visual inspection. At the same time, socio-demographic data were collected using a structured questionnaire. Variables associated with pediculosis were identified by performing a bivariate analysis, followed by a multivariate logistic regression analysis. Results: Prevalence of pediculosis capitis was 9.1% (95% confidence interval (CI): 7.0-11.2 %) in the general population and 19.9% (CI: 15.4-24.4%) in children ≤15 years of age. Multivariate analysis showed that pediculosis capitis was significantly associated with age ≤ 15 years (OR: 16.85; CI:7.42-38.24), female sex (OR: 2.84; CI: 1.58-5.12), household size of >4 persons (OR: 1.98; CI: 1.11-3.55), low quality of house construction material (OR:2.22; CI: 1.20-4.12), and presence of animals in the household (OR: 1.94; CI: 1.11-3.39). Conclusion: Pediculosis capitis was a very common disease in the studied community in Lima, Peru. Our logistic regression analysis affirms that young age is the most important risk factor for pediculosis capitis. Moreover, female sex, large household size, living in wooden houses and the presence of animals were identified as being significantly associated with head lice infestation.

Brucellar uveitis: intraocular fluids and biopsy studies

BACKGROUNDnOcular brucellosis is usually diagnosed by clinical criteria and serological tests. Little is known with regard to the ocular immunology of brucellosis and the use of intraocular diagnostic tests. We report retrospectively the laboratory findings of patients with ocular involvement associated with brucellosis.nnnMATERIALS AND METHODSnPatients with uveitis with no evident etiologic diagnosis were evaluated at the Instituto de Medicina Tropical Alexander von Humboldt of the Universidad Peruana Cayetano Heredia and the Hospital Nacional Cayetano Heredia. Patients were tested for brucellosis, tuberculosis, syphilis, toxoplasmosis, toxocariasis, and human T-cell lymphotropic virus-1. Blood and intraocular fluid samples were examined. Patients with a diagnosis of brucellar uveitis were selected as cases and patients with a diagnosis of uveitis of other etiology were included as controls. The Goldmann-Witmer coefficient was determined.nnnRESULTSnTwelve patients with clinical and laboratory findings suggestive of brucellar uveitis were considered as cases. Seven patients with uveitis of other etiology were selected as controls. Four (33.3%) patients with ocular brucellosis had negative ocular agglutinations and eight (66.7%) had positive agglutinations. No control cases had positive agglutinations for Brucella melitensis. The sensitivity of the test was 66.7% and the specificity 100%. Only one patient had a positive culture for B. melitensis in subretinal fluid. The Goldmann-Witmer coefficient was calculated in six cases of brucellosis uveitis and five uveitis controls. It was highly positive in three patients with ocular brucellosis. Tissue samples showed lymphoplasmacytic infiltrates.nnnCONCLUSIONSnIntraocular serological tests could be used to support the diagnosis of ocular brucellosis.