Alberto Villaseñor-Sierra

Conocimiento objetivo y subjetivo sobre el VIH/SIDA como predictor del uso de condón en adolescentes

Objective. To evaluate the association between objective and subjective knowledge on HIV/AIDS and condom use. Material and Methods. Analysis of a database from an anonymous, self-applied, randomized survey conducted between 1995 and 1996. Study subjects were 1 410 adolescents of four socioeconomic strata from Guadalajara, Mexico. Objective knowledge was assessed with 24 questions regarding HIV/AIDS, and subjective knowledge with the question “how much do you think you know about HIV/AIDS?” The variables associated with condom use were identified using logistic regression analysis and by calculating odds ratios with a 95% confidence interval. Results. The degree of objective knowledge was “average”, differentiated by socioeconomic strata (p< 0.001), and was higher in adolescents from medium and high socioeconomic strata (p< 0.008). Regarding subjective knowledge, adolescents from the low, medium, and high socioeconomic strata claimed to know “a little”, and the ones from the lowest stratum claimed to know “very little”. Condom use was higher in males (35.4%), and in adolescents from high socioeconomic strata (p< 0.005), than in females (15.3%) (p< 0.001). Although there was a correlation between ob

Conocimientos sobre VIH/SIDA en adolescentes urbanos: consenso cultural de dudas e incertidumbres

Objective. To describe the knowledge of HIV/AIDS among adolescents from different socioeconomic strata (SS), using cultural consensus analysis. Material and Methods. A cross-sectional descriptive and analytic study was conducted from July 1995 to March 1996, among 758 adolescents from Guadalajara, Mexico. Data were collected using a questionnaire, and analyzed by means of: a) consensus by SS and gender using factorial analysis; and b) identification of the cultural pattern of correct answers, and concordance of individual/group answers using Pearson’s r correlation coefficients. Results. There was a high degree of consensus across SS. The individual/group knowledge concordance was greater in higher SS. The pattern of correct responses showed: a) similar knowledge on casual transmission, AIDS characteristics, and higher risk in sex workers; and b) discrepancies regarding doubts and uncertainties about condom protection, distinction between HIV and AIDS, and HIV transmission in health clinics. Conclusions. Knowledge was homogeneous and mainly medically oriented across all SS. Nevertheless, there were elements of doubt and uncertainty that require differentiated informative interventions.

Phenotypes and genotypes of erythromycin-resistant Streptococcus pyogenes strains isolated from invasive and non-invasive infections from Mexico and the USA during 1999-2010 §

OBJECTIVE To compare the prevalence, phenotypes, and genes responsible for erythromycin resistance among Streptococcus pyogenes isolates from Mexico and the USA. METHODS Eighty-nine invasive and 378 non-invasive isolates from Mexico, plus 148 invasive, 21 non-invasive, and five unclassified isolates from the USA were studied. Susceptibilities to penicillin, erythromycin, clindamycin, ceftriaxone, and vancomycin were evaluated according to Clinical and Laboratory Standards Institute (CLSI) standards. Phenotypes of erythromycin resistance were identified by triple disk test, and screening for mefA, ermTR, and ermB genes was carried out by PCR. RESULTS All isolates were susceptible to penicillin, ceftriaxone, and vancomycin. Erythromycin resistance was found in 4.9% of Mexican strains and 5.2% of USA strains. Phenotypes in Mexican strains were 95% M and 5% cMLS; in strains from the USA, phenotypes were 33.3% iMLS, 33.3% iMLS-D, and 33.3% M. Erythromycin resistance genes in strains from Mexico were mefA (95%) and ermB (5%); USA strains harbored ermTR (56%), mefA (33%), and none (11%). In Mexico, all erythromycin-resistant strains were non-invasive, whereas 89% of strains from the USA were invasive. CONCLUSIONS Erythromycin resistance continues to exist at low levels in both Mexico and the USA, although the genetic mechanisms responsible differ between the two nations. These genetic differences may be related to the invasive character of the S. pyogenes isolated.

Is There Still Room for Novel Viral Pathogens in Pediatric Respiratory Tract Infections

Viruses are the most frequent cause of respiratory disease in children. However, despite the advanced diagnostic methods currently in use, in 20 to 50% of respiratory samples a specific pathogen cannot be detected. In this work, we used a metagenomic approach and deep sequencing to examine respiratory samples from children with lower and upper respiratory tract infections that had been previously found negative for 6 bacteria and 15 respiratory viruses by PCR. Nasal washings from 25 children (out of 250) hospitalized with a diagnosis of pneumonia and nasopharyngeal swabs from 46 outpatient children (out of 526) were studied. DNA reads for at least one virus commonly associated to respiratory infections was found in 20 of 25 hospitalized patients, while reads for pathogenic respiratory bacteria were detected in the remaining 5 children. For outpatients, all the samples were pooled into 25 DNA libraries for sequencing. In this case, in 22 of the 25 sequenced libraries at least one respiratory virus was identified, while in all other, but one, pathogenic bacteria were detected. In both patient groups reads for respiratory syncytial virus, coronavirus-OC43, and rhinovirus were identified. In addition, viruses less frequently associated to respiratory infections were also found. Saffold virus was detected in outpatient but not in hospitalized children. Anellovirus, rotavirus, and astrovirus, as well as several animal and plant viruses were detected in both groups. No novel viruses were identified. Adding up the deep sequencing results to the PCR data, 79.2% of 250 hospitalized and 76.6% of 526 ambulatory patients were positive for viruses, and all other children, but one, had pathogenic respiratory bacteria identified. These results suggest that at least in the type of populations studied and with the sampling methods used the odds of finding novel, clinically relevant viruses, in pediatric respiratory infections are low.

Rhinovirus is an important pathogen in upper and lower respiratory tract infections in Mexican children

BackgroundMost of the studies characterizing the incidence of rhinovirus (RV) have been carried out in hospitalized children and in developed countries. In those studies, RV-C has been associated with more severe respiratory tract infections than RV species A and B. In this study we determined the frequency and diversity of RV strains associated with upper and lower respiratory tract infections (URTI, LRTI) in Mexico, and describe the clinical characteristics of the illness associated with different RV species.MethodsA prospective surveillance of 526 and 250 children with URTI and LRTI was carried out. Respiratory samples were analyzed by RT-PCR for viruses. The 5′ untranslated region of the RV genome was amplified and sequenced.ResultsIn the case of URTI, 17.5% were positive for RV, while this virus was found in 24.8% of LRTI. The RV species was determined in 73 children with URTI: 61.6% were RV-A, 37% RV-C and, 1.4% RV-B; and in 43 children with LRTI: 51.2% were RV-A, 41.8% RV-C, and 7% RV-B. No significant differences in clinical characteristics were found in patients with RV-A or RV-C infections. A high genetic diversity of RV strains was found in both URTI and LRTI.ConclusionsBoth RV-A and RV-C species were frequently found in hospitalized as well as in outpatient children. This study underlines the high prevalence and genetic diversity of RV strains in Mexico and the potential severity of disease associated with RV-A and RV-C infections.

Serotypes and susceptibility of Streptococcus pneumoniae strains isolated from children in Mexico

OBJECTIVE To identify serotypes and susceptibility of S. pneumoniae strains from 48 children with invasive infections and 50 carriers. MATERIAL AND METHODS Typing was performed by the Quellung reaction and susceptibility by Kirby-Bauer and Etest according to CLSI standards. RESULTS Of 31 meningeal strains, serotypes 19F, 3, 6B, 14 and 23F were predominant. Resistance to penicillin and STX was 16 and 58%, respectively; of 17 invasive non-meningeal strains, serotypes 19F and 3 were predominant and resistance to penicillin and SXT was 0 and 82%, respectively; of carrier strains, serotypes 6A, 6B, 19F and 23F were predominant. CONCLUSIONS A 10-valent conjugate vaccine could offer a better coverage for meningeal strains.

Estimación de la Relación Costo-Efectividad de las Vacunas Neumocócicas Conjugadas Prevenar-13 y Synflorix®, Utilizadas en Los Programas de Vacunación de Población Infantil Mexicana

OBJECTIVE To estimate the cost effectiveness associated with the use of pneumococcal conjugated vaccines, Prevenar-13 and Synflorix®, in the Mexican pediatric population. METHODS The cost-effectiveness ratio of instrumenting vaccination programs based upon the use of Prevenar-13 and Synflorix® in the Mexican pediatric population was estimated by using a Markovs simulation model. The robustness of the conclusions reached on cost-effectiveness for both vaccines was assayed through an univariate and probabilistic sensitivity analysis that included all of the parameters considered by the model. RESULTS Synflorix® was dominant over Prevenar-13 in the cost-utility analysis; the former generated more quality-adjusted life years at a lower cost and with a lower incremental cost-utility ratio. Based on the cost-effective analysis, Prevenar-13 generated more life years gained but at a higher cost. The use of Prevenar-13 originated a higher incremental cost-effectiveness ratio and, therefore, it was not cost-effective as compared with Synflorix®. CONCLUSIONS Even though the simulations for Prevenar-13 and Synflorix® revealed both of them to be cost-effective when used to instrument pediatric vaccination campaigns in Mexico, Synflorix® had a better cost-utility/effectiveness profile. In addition, although Prevenar-13 and Synflorix® produced equivalent health outcomes, the overall analysis predicted that Synflorix® would save 360 million Mexican pesos, as compared with Prevenar-13.

Clinical outcomes in Mexican children with febrile acute upper respiratory tract infections: no impact of antibiotic therapy.

OBJECTIVE To compare the clinical outcomes (duration of signs and symptoms) and the microbiology in Mexican children with non-complicated febrile upper respiratory tract infections (URI), with and without the use of antibiotics. METHODS We conducted a prospective cohort study from September 2006 to July 2007. The study population consisted of 880 children aged 6 months to 5 years 11 months, attending four community daycare centers run by the Instituto Mexicano del Seguro Social (IMSS) and three non-IMSS daycare centers. Children with a febrile URI were enrolled before receiving any antimicrobials and were followed up for two weeks. Duration of the fever, cough, runny nose, stuffy nose, irritability, loss of appetite, tiredness, and diarrhea, and isolation of Haemophilus influenzae,Streptococcus pneumoniae, and Streptococcus pyogenes were compared in those children who received antibiotic treatment and those who did not receive antibiotics. RESULTS During the study period, a total of 145 out of 880 children were enrolled, and among those enrolled, 85/145 (59%) children received antibiotics. There was no significant difference in the duration of the signs and symptoms evaluated in the two groups. Although the proportions of S. pneumoniae, H. influenzae, and S. pyogenes isolated in children with and without antibiotics were comparable, those in whom we isolated S. pneumoniae had both a significantly longer episode of URI, as well as longer lasting diarrhea. Similarly, children receiving trimethoprim-sulfamethoxazole treatment experienced significantly longer durations of fever and diarrhea. CONCLUSIONS The mean duration of signs and symptoms and the microbiological isolates of children with febrile URI were comparable among children treated with or without antibiotics, with the exception of a longer duration of URI and diarrhea in those children with an S. pneumoniae isolate. Our findings suggest that in our population, most cases of febrile URI are caused by viral infections, and demonstrate that antibiotics should not be used routinely in children with non-complicated febrile URI.

SCCmec types and pvl gene in methicillin-resistant Staphylococcus aureus strains from children hospitalized in a tertiary care hospital in Mexico

Abstract Background: The aim of this study was to determine the prevalence, SCCmec types, presence of the Panton–Valentine leukocidin (PVL) gene, and susceptibility to antibiotics of methicillin-resistant Staphylococcus aureus (MRSA) strains isolated from hospitalized children. Methods: From August 2009 to September 2011, 291 S. aureus strains were isolated from normally sterile body sites, of which 190 (65%) were MRSA. One hundred and two of the MRSA strains were genetically evaluated. SCCmec genotypes were identified by M-PCR and the PVL gene (pvl) by end-point PCR. Resistance to erythromycin, rifampicin, clindamycin, and trimethoprim–sulfamethoxazole (SXT) was assessed by Kirby–Bauer disk diffusion method in accordance with the Clinical and Laboratory Standards Institute guidelines of 2012. Results: Of the 102 strains evaluated, 97 (95%) were SCCmec type II, 5 (5%) were SCCmec type IVa, and all (100%) were pvl-negative. Resistance to erythromycin, clindamycin, rifampicin, and SXT was 97%, 95%, 0%, and 0%, respectively. Conclusions: The prevalence of hospital-acquired MRSA was high. SCCmec type II was predominant and the pvl gene appeared not to play any role in the virulence of the MRSA strains from hospitalized children.

Interpersonal relationships and group A streptococcus spread in a Mexican day-care center

OBJECTIVE To study the effect of different degrees of centrality on the carrying of identical group A streptococcus (GAS) clones in the nasopharynx of children from a Mexican public day-care center. MATERIAL AND METHODS Nasopharyngeal cultures were performed in children from rooms B (RB) (n = 35) and C (RC) (n = 37). The Restriction Fragment Length Polymorphism (RFLP) patterns were compared among GAS isolates. A social networks questionnaire was filled out for each child and 10 classmates. Structure coefficients were compared among children with and without GAS. RESULTS Four GAS clones were identified; clone I in five children from RC; clone II in two from RC and one from RB; clone III in one from RB and one from RC; and clone IV in one from RC. Social network structure: Density of RB and RC = 0.40 (+/- 0.87) and 0.35 (+/- 0.80), respectively. In RB, the homophily pattern of interaction was different in carriers (0.00), non-carriers (0.47) and both (0.47) p = 0.35. In RC, the homophily pattern was also different in carriers (0.46), non-carriers (0.68) and mixed (0.19), p = .001. In 4/5 with clone I, the values of degree, closeness and betweenness were above the group mean. In 3/3 with clone II, the values of degree and betweenness were also above the mean. In contrast, in those with clone III and IV, the values of degree, closeness and betweenness were below the group mean. CONCLUSION The spread of specific GAS clones was associated with groups of children having a high proportion of ties and a high centrality level. This is evidence that spread of GAS strains among children attending day-care centers is not random but dependent on the degree of communication and physical contact between pairs.