Alberto Villaseñor-Sierra

Mexican Institute of Social Security, Ciudad de México, The Federal District, Mexico

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Publications (25)25.29 Total impact

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    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.
    No preview · Article · May 2014 · Scandinavian Journal of Infectious Diseases
  • Alberto Villaseñor-Sierra · Abiel Homero Mascareñas-De Los Santos

    No preview · Article · May 2013 · Archives of medical research

  • No preview · Article · Apr 2013
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    ABSTRACT: Objective Identifying factors associated with respiratory tract infection in indigenous migrant day-laborer families'children living inthe sugarcane sector in Colima, Mexico. Methods This was a cross-sectional study. Having given theirinformed consent, 71 mothers were interviewed for compiling pertinentsociodemographic data and a history of respiratory tract infection in their children during the harvest period 2010-2011. Anthropometry for 176 children aged 0-14 years was recorded and they were clinically examinedfor upper and lower respiratory tract infection. Frequencies, percentages, Chi-square, odds ratio (crude and adjusted) and 95 % confidence intervals were calculated for the resulting data. Results 52.3 % of the children in the sample had a history of respiratory infection occurring during the last six months. Respiratory infectionrates were statistically significant regarding temporary residence in shelters/hostels. The factors associated with a background of infection were being aged less than four years (AOR 4.06 (2.03-8.09) 95 % CI) and having been involved in temporary residence in a shelter,thereby leading tomore overcrowding and an increased use of wood stoves for cooking (AOR 1.92 (1.01-3.63) 95 % CI). Conclusion Indigenous migrant day-laboring families'children are vulnerable to respiratory infection. Prevention programs should target their activities by age-group, emphasizing younger children, and promote improved sanitary conditions in the shelters.
    No preview · Article · Apr 2013 · Revista de salud publica (Bogota, Colombia)
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    ABSTRACT: Indigenous migrant workers (IMWs) have a high vulnerability to HIV and STDs due to poverty and marginalization. This study examined factors associated with sexual risk behavior (SRB) according to type of partner in transnational young male IMWs at a sugar cane agro-industrial complex in western Mexico. A total of 192 sexually active IMWs were recruited from four laborer shelters to participate in a sexual partner survey. The IMWs were interviewed about their sexual partners and practices over the last 12 months during which it emerged that they had had a total of 360 sexual partners. Multiple linear regression analyses were performed to identify factors related to SRB in 222 main (spouse, mistress and girlfriend) and 138 casual partners (colleague, friend, casual encounter and sex worker). Results showed a significantly higher SRB score with casual partners. For the main partner regression model, prior exposure to HIV- and STD-preventive information and sexual intercourse with higher employment status partners (formal workers vs. self-employed in informal activities and unemployed) were associated with lower SRB scores, but if the sexual relations occurred in Mexico (vs. the U.S.), the SRB scores increased. For the casual partner model, the practice of survival sex (sex in exchange for basic needs), sexual relations in Mexico (vs. the U.S.), and being a circular migrant (person traveling for temporary work to return home when the contract is over) were related to higher SRB scores. Findings support the implementation of preventive interventions using different messages depending on the type of partners, main or casual, within the labor migrant context.
    Full-text · Article · Aug 2012 · AIDS and Behavior
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    ABSTRACT: We measured anti-Haemophilus influenzae type a capsular polysaccharide serum immunoglobulin G antibodies in cord blood sera from Mexican (n = 68) and Chilean mothers (n = 72) by enzyme-linked immunosorbent assay. Measurable antibodies were found in 79.3% of samples. Immunoglobulin G antibodies correlated with serum bactericidal activity (r = 0.66). This enzyme-linked immunosorbent assay can be used for the evaluation of adaptive immune responses to Haemophilus influenzae type a and serosurveillance studies in populations at risk.
    No preview · Article · Apr 2012 · The Pediatric Infectious Disease Journal
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    ABSTRACT: To compare the prevalence, phenotypes, and genes responsible for erythromycin resistance among Streptococcus pyogenes isolates from Mexico and the USA. 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. 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. 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.
    Full-text · Article · Jan 2012 · International journal of infectious diseases: IJID: official publication of the International Society for Infectious Diseases
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    ABSTRACT: 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. 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. 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. 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.
    Full-text · Article · Sep 2010 · International journal of infectious diseases: IJID: official publication of the International Society for Infectious Diseases
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    ABSTRACT: Late-onset sepsis (occurring after 3 days of age) either cross-infection (CI) or perinatal is the first cause of morbidity and mortality in neonatal intensive care units (NICU) around the world. Our objective was to determine the current incidence of CI risk factors in neonates admitted to the NICU of the Hospital Civil de Guadalajara during a 9-month period. A case-control study with 114 newborns; 38 with CI and 76 controls. Odds ratio with 95 % confidence interval were calculated. Associated risk factors were total parenteral nutrition (OR = 16.54, CI = 6.30-43.39, p < 0.001); weight < 1000 g (OR = 7.33, CI = 2.15-25.01, p < 0.001); intravascular catheter (OR = 6.79, CI = 2.68-17.00, p < 0.001); gestational age < 30 weeks (OR = 4.54, CI = 1.61-12.81, p < 0.003); intratracheal intubation and mechanical ventilation with (OR = 6.98, CI = 2.94-16.5, p < 0.001). Total parenteral nutrition and weight < 1000 g showed the greatest association with cross-infection; in this study, male gender was not a risk factor.
    No preview · Article · Sep 2009 · Revista medica del Instituto Mexicano del Seguro Social
  • Mayra Guadalupe Quiñonez-Alvarado · Alberto Villaseñor-Sierra
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    ABSTRACT: to evaluate the prevalence of nasopharyngeal S. pyogenes (SP) carriers among children attending a day care center (DCC) and the spread of specific clones (SC) among caretakers and relatives. nasopharyngeal cultures were performed in children with SP positive culture (306), family members (51) and caretakers (73) at time 0, and four and seven months later. Differences among SP strains were determined. Descriptive statistics and Fisher exact test were performed. SP prevalence in carrier children, caretakers and relatives was 10, 0 and 4 %. Three pairs of children, from two different classrooms, shared SP strains SC I, II and III. A clone VII was isolated from a relative. In the second survey, the SP prevalence was 4, 0 and 0 %. Two classmates shared clone I and other two from a different classroom shared clone V. In the third, the prevalence was 2, 4 and 14 %. Strains of clones II and VII were isolated from children. A sister of one child, who did not attend to DCC, was a carrier of clone II found in her brother. Clone III was isolated in one caretaker. the SP carrier prevalence was similar to other reports. The sharing of identical clones of SP was found among children in close physical contact.
    No preview · Article · Jan 2009 · Revista medica del Instituto Mexicano del Seguro Social
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    ABSTRACT: 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.
    Preview · Article · Aug 2008 · Salud publica de Mexico
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    ABSTRACT: Serum immunoglobulin G concentrations and avidities specific to Haemophilus influenzae type b (Hib) were measured in 208 children living in Guadalajara and Mexico City. Protective concentrations were found in 98.9% and 100.0% of participants, respectively. Geometric mean concentrations differed between both populations and/or among age groups. Mean avidities differed only among the 7- to 12-month-old children. Diphtheria-tetanus-whole-cell pertussis-hepatitis B-Hib primary vaccination seems to induce protection in Mexican children.
    Full-text · Article · Jul 2008 · Clinical and vaccine Immunology: CVI
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    ABSTRACT: to develop a multivariate model to predict the Streptococcus pyogenes isolation in patients with acute tonsillitis. cross-sectional analytic study on patients with acute tonsillitis without a recent history of antimicrobial consumption. We evaluated 14 signs and 18 symptoms. A pharyngeal culture was realized on 5% sheep blood agar. Group A streptococci was identified by standard methods. Statistical analysis: sensitivity, specificity, predictive values, chi2, Fisher's exact test, crude and adjusted odds ratio (OR) with 95% CI using dichotomical logistic regression with direct method and Hosmer and Lemeshow-goodness-fit test. there were 213 participants, 37% were males; a mean age of 14.9 years. We isolated Streptococcus pyogenes in 15%, and 84 % of them had received antimicrobials. We identified signs and symptoms associated with Streptococcus pyogenes isolation: painful swallowing (OR=4.45, 95% CI = 1.13-17.53); tonsils with exudates (OR=3.20, 95% CI = 1.22-8.43); smelly breath (OR=2.78, 95% CI = 1.09-7.10); painful neck nodes (OR=2.70, 95% CI = 1.05-6.96). The presence of nasal symptoms was a protective factor (OR=0.25, 95% CI = 0.09-0.71). the prevalence of Streptococcus pyogenes tonsillitis was similar to other reports. We found signs and symptoms associated to Streptococcus pyogenes isolation that allowed us to elaborate a decision algorithm.
    No preview · Article · Jul 2008 · Revista medica del Instituto Mexicano del Seguro Social
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    ABSTRACT: To identify serotypes and susceptibility of S. pneumoniae strains from 48 children with invasive infections and 50 carriers. Typing was performed by the Quellung reaction and susceptibility by Kirby-Bauer and Etest according to CLSI standards. 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. A 10-valent conjugate vaccine could offer a better coverage for meningeal strains.
    Preview · Article · Jul 2008 · Salud publica de Mexico
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    ABSTRACT: 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.
    Preview · Article · Oct 2007 · Salud publica de Mexico
  • Alberto Villaseñor-Sierra · Mayra G Quiñonez-Alvarado · José Ramiro Caballero-Hoyos
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    ABSTRACT: 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. 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. 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. 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.
    No preview · Article · Sep 2007 · Salud publica de Mexico
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    ABSTRACT: To evaluate the degree of identification of main signs and symptoms of streptococcal pharyngitis by resident doctors, general practitioners, family physicians and pediatricians. A prospective, cross-sectional and comparative study was done. A validated questionnaire was applied including the following topics: social demographic, main signs and symptoms, clinical cases; and clinical pictures. We interviewed resident doctors (n = 40), general physicians (n = 21), family physicians (n = 35) and pediatricians (n = 19) from different institutions (SSa, ISSSTE, IMSS) in Guadalajara, Mexico, from March to August 2005. Scores were interpreted as very good, good, regular and poor, and these scores were related with the specialty and clinical years of experience. Statistical analysis: chi2, student t test and linear regression. This study included 115 physicians between 22 to 60 years old (mean = 39) and with 0 to 31 (mean = 10) clinical years of experience. Regarding the conceptual identification of main signs and symptoms, tonsil exudates were recognized by 33 to 61% of physicians, and a clinical case of streptococcal tonsillitis was recognized by 50 to 70%. A clinical picture of tonsil caseum was misinterpreted as streptococcal tonsillitis by 13 to 35% of the physicians. There was no association between years of clinical experience and the scores obtained in clinical cases (r = 0.20) or clinical pictures (r = 0.09). The clinical identification of streptococcal tonsillitis was regular to poor among all the interviewed physicians, and there had no correlation with the years of clinical experience. The reinforcement in teaching to recognize the key signs and symptoms of streptococcal tonsillitis at medical school would result in better recognition, more rational use of antimicrobials and reduction in health institutions costs.
    No preview · Article · Nov 2006 · Revista medica del Instituto Mexicano del Seguro Social
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    ABSTRACT: To evaluate the seroprevalence, seroconversion, anamnesic response and events temporally associated with immune status pre and post immunization with measles and rubella vaccine in health personnel from a public University in Guadalajara, Mexico. We carried out a prospective, longitudinal and comparative study from May to June 2000 among 120 healthy volunteers. Informed consent was obtained from all participants. We administered measles (Schwarz) and rubella (RA 27/3) vaccines. Weekly phone calls during six weeks were recorded from each volunteer to assess local and systemic events temporally associated with immunization non attributable to any other disease. Serum samples were obtained before and after vaccination in 75 volunteers. Antibodies against measles and rubella were measured by an enzyme immunoassay kit (Behring) with cut-off points of 300mUI/mL 8UI/mL respectively. Statistical analysis included mean, standard deviation and paired Student's t-test (P < 0.05). 105/120 participants (87.5%) were followed during 6 weeks. 87.4% were health personnel and 44.6% were males. The age range was 17-71 years (median = 21). We found a prior history of measles in 57.1%. Local events included pain, heat, redness and induration and were reported by 4/105. Systemic events such as fever, exanthema, pain in joints and arthritis was reported by 9/105. The proportion of study subjects with protective antibodies against measles and rubella prior to vaccination was 90.7 and 94.7% respectively. Both groups reached 100% after vaccination. The proportion of non-immune health personnel was low and similar to other reports. However, the potential spread of measles and rubella virus from a non-immunized infected health care provider could be amplified by the number of patients seen daily during the peak period of 3-5 days. The vaccination of health personnel should be encouraged.
    No preview · Article · Jan 2005 · Gaceta medica de Mexico
  • Ramiro Caballero-Hoyos · Alberto Villaseñor-Sierra
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    ABSTRACT: To describe the knowledge of HIV/AIDS among adolescents from different socioeconomic strata (SS), using cultural consensus analysis. A cross-sectional descriptive and analytic study was conducted from July 1995 to March 1996, among 758 adolescents from Guadalajara, México. 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. 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. Knowledge was homogeneous and mainly medically oriented across all SS. Nevertheless, there were elements of doubt and uncertainty that require differentiated informative interventions.
    No preview · Article · Feb 2003 · Salud publica de Mexico
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    ABSTRACT: OBJETIVO: Evaluar la asociación de conocimientos objetivo y subjetivo sobre VIH/SIDA con el uso del condón. MATERIAL Y MÉTODOS: Se analizó la base de datos de una encuesta aleatoria, anónima y autoaplicada en 1 410 adolescentes de cuatro estratos socioeconómicos de Guadalajara, Jalisco, México, entre 1995 y 1996. El conocimiento objetivo se evaluó mediante 24 preguntas sobre VIH/SIDA y el "subjetivo" con la pregunta: "?(spanish)qué tanto crees conocer sobre el SIDA?" Las variables predictoras del uso del condón se identificaron mediante regresión logística y cálculo de la razón de momios con IC 95%. RESULTADOS: El nivel de conocimiento objetivo fue regular y tuvo diferencias por estratos (p< 0.001) favoreciendo al medio y superior (p= 0.008). Del conocimiento subjetivo, los de estratos alto, medio y bajo percibieron saber "algo", y los del marginado "poco". Los varones dijeron usar más el condón (35.4%) que las mujeres (15.3%) (p< 0.001), y los de estratos superiores (p< 0.005). Aunque conocimiento objetivo y subjetivo se correlacionaron (r= 0.37, p< 0.001), un mayor conocimiento subjetivo se asoció con el uso del condón (p< 0.001). CONCLUSIONES: Conocimiento subjetivo, pertenecer al estrato alto o medio y ser varón, predijeron el uso constante del condón. Su uso fue diferencial por género y estrato socioeconómico.
    Full-text · Article · Jan 2003 · Salud publica de Mexico