Lázaro Agustín Vélez

University of Antioquia, Santa Fe de Antioquia, Antioquia, Colombia

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Publications (16)24.54 Total impact

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    ABSTRACT: Introduction: Part of the success of methicillin-resistant Staphylococcus aureus (MRSA) as a pathogen responds to the rapid spread of pandemic lineages with diverse virulence and antimicrobial susceptibility profiles. In Colombia, several healthcare-associated MRSA (HA-MRSA) clones have been found, including the pediatric clone (CC5-ST5-SCC mec IV), the Brazilian clone (CC8-ST239-SCC mec III), and the Chilean/Cordobés clone (CC5-ST5-SCC mec I). Moreover, the community-associated MRSA (CA-MRSA) clone USA300 has been reported as causing hospital-acquired infections. Objective: To describe the changes over time in the distribution of MRSA clones from a university hospital in Medellín collected at two time points a decade apart. Materials and methods: A total of 398 MRSA strains were analyzed. Of these, 67 strains were collected in 1994, while the remaining 331 strains were collected between 2008 and 2010. Species identification and methicillin resistance were confirmed by detection of nuc and mec A genes, respectively. Molecular characterization included spa typing, SCC mec typing, PFGE and MLST. Results: Analysis of the MRSA strains collected in 1994 revealed that they belonged to a single clone, the CC5-SCC mec IV, whereas among the isolates from 2008-2010, two dominant clones were identified: CC8-SCC mec IVc, which included spa types t008 and t1610 and is closely related to the USA 300 clone, and CC5-SCC mec I ( spa type t149), related to the Chilean clone. The ST5-SCC mec IV clone from 1994 was not detected. Conclusions: This study identifies temporal dynamics in MRSA clone diversity, and highlights the importance of local surveillance and dissemination of results, especially in countries like Colombia where MRSA is prevalent and knowledge regarding its epidemiology is still insufficient.
    Biomédica: revista del Instituto Nacional de Salud 04/2014; 34(Suppl 1):34-40. · 0.32 Impact Factor
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    ABSTRACT: Most studies on Staphylococcus aureus have focused on the molecular epidemiology of methicillin-resistant S. aureus (MRSA) infections. In contrast, little information is available regarding the molecular epidemiology of currently circulating methicillin-susceptible S. aureus (MSSA) isolates in hospital settings, an epoch when the epidemiology of S. aureus has undergone significant changes. We conducted a cross-sectional study to compare the clinical, epidemiological, and genetic characteristics of MSSA and MRSA isolates at 3 tertiary-care hospitals in Medellín, Colombia, from February 2008 to June 2010. The infections were classified according to the Centers for Disease Control and Prevention (CDC) definitions. Genotypic analysis included spa typing, multilocus sequence typing (MLST) and staphylococcal cassette chromosome (mec) (SCCmec) typing. A total of 810 patients was enrolled. One hundred infections (12.3%) were classified as community-associated (31 CA-MSSA, 69 CA-MRSA), 379 (46.8%) as healthcare-associated community-onset (136 HACO-MSSA, 243 HACO-MRSA), and 331 (40.9%) as healthcare-associated hospital-onset (104 HAHO-MSSA, 227 HAHO-MRSA). Genotype analyses showed a higher diversity and a more varied spa type repertoire in MSSA than in MRSA strains. Most of the clinical-epidemiological characteristics and risk factors evaluated did not allow for discriminating MRSA- from MSSA-infected patients. The lack of equivalence among the genetic backgrounds of the major MSSA and MRSA clones would suggest that the MRSA clones are imported instead of arising from successful MSSA clones. This study emphasizes the importance of local surveillance to create public awareness on the changing S. aureus epidemiology.
    International journal of medical microbiology: IJMM 01/2013; · 4.54 Impact Factor
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    ABSTRACT: To determine the incidence of pulmonary tuberculosis (TB) in inmates, factors associated with TB, and the time to sputum smear and culture conversion during TB treatment. Prospective cohort study. All prisoners with respiratory symptoms (RS) of any duration were evaluated. After participants signed consent forms, we collected three spontaneous sputum samples on consecutive days. We performed auramine-rhodamine staining, culturing with the thin-layer agar method, Löwestein-Jensen medium and MGIT, susceptibility testing for first-line drugs; and HIV testing. TB cases were followed, and the times to smear and culture conversion to negative were evaluated. Of 9,507 prisoners held in four prisons between April/30/2010 and April/30/2012, among them 4,463 were screened, 1,305 were evaluated for TB because of the lower RS of any duration, and 72 were diagnosed with TB. The annual incidence was 505 cases/100,000 prisoners. Among TB cases, the median age was 30 years, 25% had <15 days of cough, 12.5% had a history of prior TB, and 40.3% had prior contact with a TB case. TB-HIV coinfection was diagnosed in three cases. History of prior TB, contact with a TB case, and being underweight were risk factors associated with TB. Overweight was a protective factor. Almost a quarter of TB cases were detected only by culture; three cases were isoniazid resistant, and two resistant to streptomycin. The median times to culture conversion was 59 days, and smear conversion was 33. The TB incidence in prisons is 20 times higher than in the general Colombian population. TB should be considered in inmates with lower RS of any duration. Our data demonstrate that patients receiving adequate anti-TB treatment remain infectious for prolonged periods. These findings suggest that current recommendations regarding isolation of prisoners with TB should be reconsidered, and suggest the need for mycobacterial cultures during follow-up.
    PLoS ONE 01/2013; 8(11):e80592. · 3.53 Impact Factor
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    ABSTRACT: Recent reports highlight the incursion of community-associated MRSA within healthcare settings. However, knowledge of this phenomenon remains limited in Latin America. The aim of this study was to evaluate the molecular epidemiology of MRSA in three tertiary-care hospitals in Medellín, Colombia. An observational cross-sectional study was conducted from 2008-2010. MRSA infections were classified as either community-associated (CA-MRSA) or healthcare-associated (HA-MRSA), with HA-MRSA further classified as hospital-onset (HAHO-MRSA) or community-onset (HACO-MRSA) according to standard epidemiological definitions established by the U.S. Centers for Disease Control and Prevention (CDC). Genotypic analysis included SCCmec typing, spa typing, PFGE and MLST. Out of 538 total MRSA isolates, 68 (12.6%) were defined as CA-MRSA, 243 (45.2%) as HACO-MRSA and 227 (42.2%) as HAHO-MRSA. The majority harbored SCCmec type IVc (306, 58.7%), followed by SCCmec type I (174, 33.4%). The prevalence of type IVc among CA-, HACO- and HAHO-MRSA isolates was 92.4%, 65.1% and 43.6%, respectively. From 2008 to 2010, the prevalence of type IVc-bearing strains increased significantly, from 50.0% to 68.2% (p = 0.004). Strains harboring SCCmec IVc were mainly associated with spa types t1610, t008 and t024 (MLST clonal complex 8), while PFGE confirmed that the t008 and t1610 strains were closely related to the USA300-0114 CA-MRSA clone. Notably, strains belonging to these three spa types exhibited high levels of tetracycline resistance (45.9%). CC8 MRSA strains harboring SCCmec type IVc are becoming predominant in Medellín hospitals, displacing previously reported CC5 HA-MRSA clones. Based on shared characteristics including SCCmec IVc, absence of the ACME element and tetracycline resistance, the USA300-related isolates in this study are most likely related to USA300-LV, the recently-described 'Latin American variant' of USA300.
    PLoS ONE 01/2012; 7(6):e38576. · 3.53 Impact Factor
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    ABSTRACT: Traditional reading of chest X-rays usually has a low prognostic value and poor agreement. This study aimed to determine the interobserver and intraobserver agreement using two reading formats in patients with community-acquired pneumonia, and to explore their association with etiology and clinical outcomes. A pulmonologist and a radiologist, who were blind to clinical data, interpreted 211 radiographs using a traditional analysis format (type and location of pulmonary infiltrates and pleural findings), and a quantitative analysis (pulmonary damage categorized from 0 to 10). For both, the interobserver and intraobserver agreement was estimated (Kappa statistic and intraclass correlation coefficient). The latter was assessed in a subsample of 25 radiographs three months after the initial reading. Finally, the observers made a joint reading to explore its prognostic usefulness via multivariate analysis. Seventy-four chest radiographs were discarded due to poor quality. With the traditional reading, the mean interobserver agreement was moderate (0.43). It was considered good when the presence of pleural effusion, and the location of the infiltrates in the right upper lobe and both lower lobes, were evaluated; moderate for multilobar pneumonia; and poor for the type of infiltrates. The mean intraobserver agreement for each reviewer was 0.71 and 0.5 respectively. The quantitative reading had an agreement between good and excellent (interobserver 0.72, intraobserver 0.85 and 0.61). Radiological findings were neither associated to a specific pathogen nor to mortality. In patients with pneumonia, the interpretation of the chest X-ray, especially the smallest of details, depends solely on the reader.
    The Brazilian journal of infectious diseases: an official publication of the Brazilian Society of Infectious Diseases 12/2011; 15(6):540-6. · 1.04 Impact Factor
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    Emerging Infectious Diseases 10/2011; 17(10):1970-1. · 6.79 Impact Factor
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    ABSTRACT: The diagnosis of Pneumocystis jirovecii pneumonia is based on observation of the microorganism using several staining techniques in respiratory samples, especially bronchoalveolar lavage and induced sputum. Recently, the fungus also has been detected in oropharyngeal wash samples, but only using molecular tests. The diagnostic yield of two microscopic stains, toluidine blue O and direct fluorescent antibody, was compared in bronchoalveolar lavage and oropharyngeal wash samples for the detection of P. jirovecii in immunocompromised patients with pneumonia. Cross-sectional evaluation diagnostic tests were used in 166 immunosuppressed patients with suspected P. jirovecii. By protocol, bronchoscopic bronchoalveolar lavage and oropharyngeal wash samples were prepared by cytocentrifugation, and slides were stained with toluidine blue and fluorescent antibody. The proportion of positive results from each stain and concordance between them were determined. Twenty-four cases (14.5%) of P. jirovecii were detected in bronchoalveolar lavage samples. Of them, 21 were positive by both toluidine blue and fluorescent antibody stains, whereas 3 cases were detected by fluorescent antibody alone. None of the 166 oropharyngeal wash samples were positive by either of these techniques. No significant differences were found between proportions from positive results (p=0.63). Concordance (kappa coefficient) between both stains was 0.92 (95% CI: 0.84-1.00). Both techniques were useful to diagnose P. jirovecii in bronchoalveolar lavage samples. However, toluidine blue stain did not detect 12% of fluorescent antibody positive cases. Oropharyngeal wash samples do not provide sufficient material for the microscopic identification of this fungus.
    Biomédica: revista del Instituto Nacional de Salud 06/2011; 31(2):222-31. · 0.32 Impact Factor
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    ABSTRACT: Introduction: histoplasmosis is an endemic mycosis in Colombia and a relatively common complication in HIV patients. The aim of this study was to identify clinical and epidemiological characteristics and mortality risk factors in patients infected with histoplasmosis and HIV.
    Infectio. 12/2010; 14:s99-s106.
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    ABSTRACT: Microbiological diagnosis of pneumonia allows the optimal use of antibiotics in mechanically ventilated patients. That is why samples of bronchoscopic bronchoalveolar lavage had been quantitatively cultivated, but this procedure is not always possible. To evaluate the microbiological concordance between respiratory samples obtained by non-bronchoscopic protected bronchoalveolar lavage compared to the bronchoscopic ones, and to find out whether concordance was affected by previous use of antibiotics or the time of pneumonia onset. Prospective study conducted at Hospital Universitario San Vicente de Paúl, in 38 patients with suspected pneumonia in mechanical ventilation. Bronchoalveolar lavage specimens were taken by two methods, the traditional one and non-bronchoscopic bronchoalveolar lavage, using a telescoping preformed tip catheter (Balcath). All samples were processed using conventional microbiologic protocols. Considering flexible bronchoscopy with bronchoalveolar lavage as the gold standard, cultures allowed the identification of at least one respiratory pathogen in 60.5% of cases. Diagnostic agreement was achieved in 82% of patients and 79% of microbiologic isolates. Using the Cohen's kappa coefficient, general concordance between both methods was 0.76 [0.60-0.93]; but in those who received previously antibiotics was 0.26 [0.05-0.48], versus 1.0 in those who did not (p<0.0001). Concordance did not differ significantly when cases of early or late pneumonia were compared. Concordance between non-bronchoscopic and bronchoscopic bronchoalveolar lavage is good in mechanically ventilated patients with pneumonia. However, the use of antibiotics previously, but not the time of pneumonia presentation, significantly decreases that concordance.
    Biomédica: revista del Instituto Nacional de Salud 12/2008; 28(4):551-61. · 0.32 Impact Factor
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    ABSTRACT: Prophylaxis against tuberculosis has been recognized as important for preventing clinical forms of tuberculosis, mainly in HIV positive patients. However, in countries with high tuberculosis prevalence, prophylaxis application and effectiveness remains controversial. Effectiveness was established for two prophylaxis regimens -isoniazid treatment for nine months and pirazinamid/rifampin for 60 days. Two cohort groups of patients diagnosed with HIV/AIDS were compared. One consisted of 131 volunteer patients, who received one of the two prophylactic regimens -pirazinamid/rifampin or isoniazid. The tuberculosis treatment drugs were self-administered and independent of tuberculin response tests. The second group consisted of 200 patients selected from the records of a HIV/AIDS control program. Follow up for both groups was conducted over a two-year period through clinical records. The 2 groups were similar with respect to clinical and demographic variables. A higher proportion of patients in the control group had CD4 counts <200/ml and viral load >100,000 copies. In the prophylactic group, 8% of patients reported adverse effects due to the drug, and one person had tuberculosis in that group (0.8%). Ten persons in the control group contracted tuberculosis (5%) RR=0.15, 95%CI 0.02-1.18, p=0.07. The prophylaxis protective level was calculated to be 80%, after taking into account CD4, viral load, and effective antiretroviral therapy. The prophylaxis against tuberculosis was effective in HIV positive patients, independently of the immune status, viral load, and highly effective antiretroviral therapy.
    Biomédica: revista del Instituto Nacional de Salud 01/2008; 27(4):515-25. · 0.32 Impact Factor
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    ABSTRACT: PREVIOUS PRESENTATION: This study was presented in part at the 47th Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC); September 17, 2007; Chicago, Ill. CONFLICT OF INTEREST STATEMENT: Lázaro Vélez has received research funding from Astra-Zeneca and Roche Colombia, and has been a consultant for Pfizer. Other authors did not declare conflicts of interest. BACKGROUND: Community Acquired Pneumonia (CAP) is an important reason to prescribe antibiotics in hospitals. Since etiologic diagnosis is cumbersome, most clinicians use initial broad coverage as suggested by local/international guidelines. This approach may induce overprescription of antibiotics, increasing costs, resistance and adverse effects. Our aim was to quantify the impact that overprescription of antibiotic has on the implementation of IDSA/ATS 2007 guidelines. METHODS: A prospective cohort study conducted at 11 hospitals in Medellín, Colombia, 2005-06. We included 205 adult CAP patients with an identified pathogen. Four categories of appropriateness were established: appropriate, insufficient, excessive and useless. To quantify the magnitude of antibiotic prescription, we compared the Defined Daily Doses (DDD) of antibiotics suggested for the empiric treatment by IDSA/ATS 2007 guidelines according to severity (mild, moderate and severe CAP) with the DDD of the antibiotics that would be prescribed based on the identified respiratory pathogen. FINDINGS: Empiric coverage recommended by IDSA/ATS resulted appropriate in 24.9%, insufficient in 2.4%, excessive in 57.6% and useless in 15.1%. Total antibiotic consumption for the included patients, according to identified pathogens, would be 2.255 DDD. Predicted antibiotic use based on IDSA/ATS guidelines would increase to 4.440 (97% more). The DDD raise was higher in moderate and severe categories compared to mild CAP (130%, 129.4% and 53.9%, respectively). INTERPRETATION: Implementation of IDSA/ATS 2007 guidelines for the treatment of CAP induces a considerable increase in antibiotic prescription, especially in moderate and severe cases. A judicious clinical assessment and better diagnostic tools should be used to optimize antibiotic therapy in CAP. FUNDING: This study was supported by research grant 1115- 04-16498 from Colciencias and University of Antioquia, Medellín, Colombia.
    Iatreia 01/2008;
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    ABSTRACT: Introduction. Microbiological diagnosis of pneumonia allows the optimal use of antibiotics in mechanically ventilated patients. That is why samples of bronchoscopic bronchoalveolar lavage had been quantitatively cultivated, but this procedure is not always possible. Objective. To evaluate the microbiological concordance between respiratory samples obtained by non-bronchoscopic protected bronchoalveolar lavage compared to the bronchoscopic ones, and to find out whether concordance was affected by previous use of antibiotics or the time of pneumonia onset. Materials and methods. Prospective study conducted at Hospital Universitario San Vicente de Paúl, in 38 patients with suspected pneumonia in mechanical ventilation. Bronchoalveolar lavage specimens were taken by two methods, the traditional one and non-bronchoscopic bronchoalveolar lavage, using a telescoping preformed tip catheter (Balcath®). All samples were processed using conventional microbiologic protocols. Results. Considering flexible bronchoscopy with bronchoalveolar lavage as the gold standard, cultures allowed the identification of at least one respiratory pathogen in 60.5% of cases. Diagnostic agreement was achieved in 82% of patients and 79% of microbiologic isolates. Using the Cohen´s Kappa coefficient, general concordance between both methods was 0.76 [0.60-0.93]; but in those who received previously antibiotics was 0.26 [0.05-0.48], versus 1.0 in those who did not (p
    Biomédica: revista del Instituto Nacional de Salud 01/2008; 28(4):-. · 0.32 Impact Factor
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    ABSTRACT: Fast and accurate etiologic diagnosis of pneumonia in immunocompromised patients is essential for a good outcome. Utility of bronchoalveolar lavage (BAL) samples has already been established, but studies about them are scarce and limited to few countries. We aimed to evaluate the accuracy of a diagnostic protocol, emphasizing on local epidemiology, rapidity, and yield of different techniques. One year prospective study of 101 consecutive immunosuppressed patients admitted with suspected pneumonia to a university hospital. They all had bronchoscopic BAL (n=109) and respiratory sampling. Conventional microbiological studies, cytomegalovirus pp65 antigenemia and transbronchial biopsy (TBB), whenever considered pertinent, were done. Results were analyzed along with other diagnostic procedures, clinical course and final outcome. HIV/AIDS infection was the most frequent cause of inclusion (n=80). Infections accounted for 79 out of 122 final diagnoses (64.8%). Our protocol identified 60 infectious and 3 noninfectious pathologies (general yield: 51.6%). Sensitivity in pulmonary infections was 75.9% (IC95%: 64.8-84.6%), specificity 86.0% (72.6-93.7%), positive predictive value 89.6% (79.1-95.3%), negative predictive value 69.4% (56.2-80.1%), accuracy 79.8% (71.7-86.2%). Mycobacterium spp. (n=27), bacteria (n=19), Pneumocystis jirovecii (n=18) and other fungi (histoplasmosis: 6, aspergillosis: 5, cryptococosis: 3) were the most common infectious pathogens. Direct microscopy allowed an early definite/presumptive diagnosis in 36/49 fungal and mycobacterial infections (73.5%). Up to 30% of mycobacterial infections were missed. Systematical study of BAL samples has a high diagnostic yield in our immunocompromised patients with suspected pneumonia. As economical and epidemiological conditions of regions are different, it should be tried everywhere.
    Respiratory Medicine 11/2007; 101(10):2160-7. · 2.59 Impact Factor
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    ABSTRACT: Introduction. Prophylaxis against tuberculosis has been recognized as important for preventing clinical forms of tuberculosis, mainly in HIV positive patients. However, in countries with high tuberculosis prevalence, prophylaxis application and effectiveness remains controversial. Objective. Effectiveness was established for two prophylaxis regimens -isoniazid treatment for nine months and pirazinamid/rifampin for 60 days. Materials and methods. Two cohort groups of patients diagnosed with HIV/AIDS were compared. One consisted of 131 volunteer patients, who received one of the two prophylactic regimens - pirazinamid/rifampin or isoniazid. The tuberculosis treatment drugs were self-administered and independent of tuberculin response tests. The second group consisted of 200 patients selected from the records of a HIV/AIDS control program. Follow up for both groups was conducted over a two-year period through clinical records. Results. The 2 groups were similar with respect to clinical and demographic variables. A higher proportion of patients in the control group had CD4 counts 100,000 copies. In the prophylactic group, 8% of patients reported adverse effects due to the drug, and one person had tuberculosis in that group (0.8%). Ten persons in the control group contracted tuberculosis (5%) [RR=0.15, 95%CI 0.02-1.18, p=0.07]. The prophylaxis protective level was calculated to be 80%, after taking into account CD4, viral load, and effective antiretroviral therapy. Conclusion. The prophylaxis against tuberculosis was effective in HIV positive patients, independently of the immune status, viral load, and highly effective antiretroviral therapy.
    Biomédica: revista del Instituto Nacional de Salud 01/2007; 27(4):515-525. · 0.32 Impact Factor
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    ABSTRACT: Immunofluorenscence methods to detect pp65 antigenemia were implemented for identifying the circulating virus-infected cells in individuals known to have cytomegalovirus infection and disease symptoms. Between December-2002 and July-2003, 110 peripheral blood samples were obtained from 46 immunosuppressed patients. pp65 antigenemia and the presence of circulating cells were determined by indirect immunofluorescence using a commercial kit to detect CMV pp65 antigen in peripheral blood leukocytes. Antigenemia was positive when one or more cells was observed with multilobulated, homogenous fluorescent stain in the nucleus. The presence of infected circulating cells (peripheral blood mononuclear cells) was determined when an extended pattern of fluorescent stain was observed throughout the cytoplasm in cells of 35 to 50 microm. Eight antigenemias from 7 patients (15%) were positive. Of these, 4 (57%) were also positive for circulating infected cells and consisted of 3 kidney transplant recipients and 1 liver transplant recipient. The number of positive cells in antigenemia was greater in kidney-transplant recipients than in the rest of immunosupressed patients (457 vs. 1.96, p < 0.005). No association was seen between the presence of infected circulating cells, morbidity, mortality or the development of GVHD (p < 0.001). No correlation was observed between the presence of infected cells, antigenemia and mortality. To substantiate the lack of correlation amongst these factors, prospective studies with larger sample sizes are necessary. These studies will aid in better defining the clinical application in immunosupressed patients.
    Biomédica: revista del Instituto Nacional de Salud 04/2005; 25(1):129-35. · 0.32 Impact Factor
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    Biomédica: revista del Instituto Nacional de Salud 01/2005; 25(1):129-135. · 0.32 Impact Factor