Biomedical subjects

Elizabeth Castañeda

Publications and source records attributed to Elizabeth Castañeda.

15 recordsLinked to original sources

PubMed2005

Tracking methicillin-resistant Staphylococcus aureus clones in Colombian hospitals over 7 years (1996-2003): emergence of a new dominant clone.

Worldwide dissemination of methicillin-resistant Staphylococcus aureus (MRSA) clones is a well-characterised phenomenon. Two hundred isolates of MRSA recovered from 17 Colombian hospitals collected between 2001 and 2003 were characterised by pulsed-field gel electrophoresis (PFGE). A new dominant electrophoretic pattern unrelated to previously characterised clones in Colombia was detected in 137 (68.5%) of these isolates. Only 40 (20%) isolates still showed a pattern closely related to a previously described dominant clone. The new electrophoretic pattern was indistinguishable from a cluster of isolates recovered in Chile between 1996 and 1998. Isolates from this clonal cluster exhibited multidrug resistance but were susceptible to linezolid and glycopeptides. The results indicate a shift in the population genetics of Colombian MRSA and confirm dissemination of the Chilean clone for the first time.

Anti-Bacterial Agents↗

PubMed2005

[Environmental distribution of Cryptococcus neoformans in the department of Cundinamarca-Colombia].

Cryptococcus neoformans is an opportunistic fungal pathogen that could cause infection in patients with immunodeficiency and healthy patients. The AIDS epidemic has shown the importance of studying the ecology and epidemiology of this fungus. The aim of this investigation was to determine if there was a relationship between the environmental distribution of the different varieties of C. neoformans and the climate zones in two transects located in department of Cundinamarca, in Colombia. For the isolation and identification of the yeast, conventional phenotypic methods were used and it was determined the population density (CFU/g of sample) and which was the variety of greater prevalence in each altitudinal rank. A total of 765 samples, from 26 municipalities were collected; of these 146 corresponded to pigeon droppings (Columba livia), 437 to Eucalyptus detritus (Eucalyptus camaldulensis and related species) and 182 to detritus of almond trees (Terminalia cattapa). C. neoformans was isolated from 46% of the studied municipalities, in both transects and the climate zones: warm, temperate and cold. The results indicated that the greater frequency of positive isolations came from the last climate zone (cold). The population density in pigeon excrements oscillated between 50 and 9.2 x 1,000,000, in eucalyptus between 500 and 10 x 1,000,000 and in almond trees was 50 CFU/g. Of 100,000 positive isolations 31% were serotype A, 59% serotype B and 10% serotype C; 96% of the isolates grew to 37 degrees C and all showed capsule. In conclusion, C. neoformans prevails in the three habitats studied but it showed a predilection for the cold thermal floor; the population densities did not allow defining a standard pattern of occurrence.

Altitude↗

PubMed2005

Detection and serotyping of Streptococcus pneumoniae from nasopharyngeal samples by PCR-based multiplex assay.

We developed a multiplex PCR-based methodology for nasopharyngeal samples maintained in egg thioglycolate antibiotic and skim milk-tryptone-glucose-glycerol media to identify and serotype the most important serotypes of Streptococcus pneumoniae that cause invasive disease in children. This technique can be used to study the epidemiology of pneumococcal colonization and the effect of conjugate vaccines.

Bacteriological Techniques↗

PubMed2005

Anti-glucuronoxylomannan IgG1 specific antibodies production in Cryptococcus neoformans resistant mice.

BACKGROUND: Cryptococcus neoformans is a widely disseminated fungus shown to be responsible for infections in individuals with impaired cell mediated immunity, such as patients with human immunodeficiency virus (HIV). Cryptococcus neoformans has a polysaccharide capsule composed of glucuronoxylomannan (GXM), which acts as a major virulence factor and is considered to be a thymus independent type-2 antigen (TI-2). OBJECTIVE: In the current study, the production kinetics were evaluated for IgG subclasses specific for GXM, and assessed with the cross reactive antibodies to Streptococcus pneumoniae polysaccharide. In addition, spleen B cell subpopulations were quantified in murine models of cryptococcosis with different susceptibilities to the infection. MATERIALS AND METHODS: Antibodies were detected by ELISA at different time intervals after C. neoformans infection in moderately resistant (Balb/c), highly resistant (CBA/j) and susceptible (C57BL/6) mouse strains. B cells subpopulations were determined by flow cytometry analysis. RESULTS: Early production of IgG1, described as protector antibodies, coincided with a decrease of the number of C. neoformans colony forming units in the lungs. Polysaccharide cross-reactive antibodies were detected in each of the three mouse strains. Antibody titers were highest in the susceptible strain (C57BL/6), a strain which also showed the highest proportion of splenic CD5+ B lymphocytes. In contrast, CBA/J mice showed the highest levels of CD43+ B. CONCLUSIONS: These findings suggest that IgG1 antibodies specific for GXM, are implicated in host protection against C. neoformans infection and may be regulated by CD43+ cells. They also suggest that cross reactivity antibodies are not important in the protection against C. neoformans infection.

Animals↗

PubMed2005

[Isolation of Cryptococcus gattii serotype B from detritus of Eucalyptus trees in Colombia].

INTRODUCTION: Cryptococcus gattii serotype B has been associated with several species of trees in tropical and subtropical regions. Serotype B has been found to be the second most frequently isolated from patients in Colombia, but it has not been isolated from the environment. Therefore, a study was designed to sample plant material from a forest in the province of Cundinamarca, with the aim of establishing the presence and distribution of the C. neoformans complex, specially serotype B. In addition, isolates were evaluated for several phenotypic characteristics associated with virulence. METHODOLOGY: During February and March, 2003, 4 separate sample collections were made. One hundred sixty-seven samples were collected from detritus of eucalyptus and 28 samples from other species of trees. All were processed using the conventional procedure and plated on selective media. The following parameters were measured: cellular and capsular sizes in the filtrates, growth at 37 degrees C, virulence in a mouse animal model system, and mating type as detected by PCR. RESULTS: Cryptococcus gattii serotype B was isolated from 46 eucalyptus samples (27.5%). The cellular size in the filtrates ranged from 3.10 to 4.15 microm and the capsular size from 0.30 and 0.46 microm. The 46 isolates grew at 37 degrees C, but none of them caused the death in the animals during 70-day observation period. All isolates were of mating type a. CONCLUSIONS: This constitutes the first report of the isolation of serotype B, mating type a, from eucalyptus detritus in Colombia.

Animals↗

PubMed2004

[Molecular surveillance of invasive penicillin-resistant Streptococcus pneumoniae Colombian isolates recovered from children less than 5 years of age].

The rapid increase of penicillin-resistant Streptococcus pneumoniae isolates could be a consequence of the spread of clones or due to the antimicrobial selective pressure. The genetic relatedness of 190 invasive isolates S. pneumoniae with reduced susceptibility to penicillin recovered from Colombian children less than 5 years old during a surveillance study from 2000 to 2003 was determined by the use of pulsed-field electrophoresis (PFGE). Overall, 42 different PFGE patterns were identified, but 4 of them included 76% of all isolates. They were related with international clones 1-Spain23F, 2-Spain6B, 3-Spain9V and 26-Colombia23F. Our results indicated that the dissemination of penicillin-resistant S. pneumoniae was the result of the spread of international clones, specially, the 3-Spain9V clone.

Anti-Bacterial Agents↗

PubMed2004

[Cryptococcus spp. DNA extraction from environmental samples].

The genus Cryptococcus encompasses 38 species, but only 3 are associated with disease in humans and animals, Cryptococcus laurentii, Cryptococcus albidus and Cryptococcus neoformans. The last one is the most frequently reported. The disease is acquired by the inhalation of infectious propagules present in the environment. The habitat has been established using extraction techniques with buffer supplemented with antibiotics and plating in selective media. The aim of this work was to evaluate several DNA extraction techniques for Cryptocococus spp. from environmental samples. The control isolates were C. neoformans, C. albidus, C. laurentii and Paracoccidiodes brasiliensis. We also used vermiculita and soil samples contaminated with different yeast concentrations (10 to 10(6) cells/g) and samples naturally contaminated with C. neoformans. DNA was extracted with physical and chemical methods and with a commercial kit, and the DNA was purified with agarose blocks and silica columns. For the PCR amplification we used the CN4-CN5 primers, which are specific for C. neoformans. Only the commercial kit allowed DNA extraction and amplification from contaminated soil samples up to a concentration of 10 cells/g and from one sample naturally colonized. With this work we extracted and amplified DNA from Cryptococcus spp. from environmental samples with appropriate PCR specificity, it will be a tool to establish the ecological areas of C. neoformans in our country.

Case-Control Studies↗

PubMed2003

Molecular typing of IberoAmerican Cryptococcus neoformans isolates.

A network was established to acquire basic knowledge of Cryptococcus neoformans in IberoAmerican countries. To this effect, 340 clinical, veterinary, and environmental isolates from Argentina, Brazil, Chile, Colombia, Mexico, Peru, Venezuela, Guatemala, and Spain were typed by using M13 polymerase chain reaction-fingerprinting and orotidine monophosphate pyrophosphorylase (URA5) gene restriction fragment length polymorphism analysis with HhaI and Sau96I in a double digest. Both techniques grouped all isolates into eight previously established molecular types. The majority of the isolates, 68.2% (n=232), were VNI (var. grubii, serotype A), which accords with the fact that this variety causes most human cryptococcal infections worldwide. A smaller proportion, 5.6% (n=19), were VNII (var. grubii, serotype A); 4.1% (n=14), VNIII (AD hybrid), with 9 isolates having a polymorphism in the URA5 gene; 1.8% (n=6), VNIV (var. neoformans, serotype D); 3.5% (n=12), VGI; 6.2% (n=21), VGII; 9.1% (n=31), VGIII, and 1.5% (n=5) VGIV, with all four VG types containing var. gatii serotypes B and C isolates.

Adult↗

PubMed2003

[Molecular characterization of invasive isolations of penicillin-resistant Streptococcus pneumoniae recovered from adult patients].

Streptococcus pneumoniae penicillin resistance is associated with the international dispersion of specifically identified strains. In Colombia, the presence and circulation of resistant strains Spain23F-1, Spain6B-2, Spain9V and Colombian23F-25 has been demonstrated in children less than 5 years old. Strain identities were established for 80 penicillin resistant S. pneumoniae isolates recovered from Colombian adult patients. Three approaches to genotypic characterization of the strains wrere used: a) chromosomal DNA was digested with Sma 1, and the products subjected to pulse-field gel electrophoresis (PFGE); b) restriction enzyme fragment comparison of the penicillin binding protein genes (pbp 1a, 2b and 2x), and c) pneumococcal surface protein A (PspA) family. The results showed that 2.5% of the isolates were genetically related to Spain23F-1 clone, 10% to Spain6B-2 clone, 37.5% to Spain9V-3, in addition, 14% of the capsular type 23F isolates were related to the Colombia23F-25 clone and demonstrated an intermediate level resistance to penicillin. Wide spread circulation of international strains as well as a Colombian strain highlighted the importance of these clones in maintaining the prevalence of resistance to penicillin in Colombia.

Colombia↗

PubMed2003

[Surveillance of Haemophilus influenzae serotypes and antimicrobial resistance in Colombia, 1994-2002].

Invasive disease caused by Haemophilus influenzae serotype b results in high rates of morbidity and mortality among children. In 1994, the Microbiology Group at the Instituto Nacional de Salud (Colombia) initiated a program to detect antimicrobial resistance in H. influenzae. Invasive isolates were collected by hospitals and public health laboratories as part of surveillance programs for acute respiratory infections and acute bacterial meningitis. To determine the evolution of serotypes and antimicrobial resistance patterns, invasive H. influenzae isolates collected from 1994 to 2002 were compared, and the impact of Hib conjugated vaccine in Colombia was reassessed. The analysis included 683 isolates, 379 (55.5%) were recovered from male patients, 370 (54.2%) from children under one year, 227 (33.2%) from children aged 1 to 5, 19 (2.8%) from children aged 6 to 14, and 38 (5.6%) from children over 14 years; 29 (4.2%) with no age data. Clinical classification recorded 493 (72.2%) of the samples were from patients with meningitis, 181 (26.5%) with pneumonia, and 9 (0.9%) with other diseases. Eighty five percent of isolates corresponded to H. influenzae serotype b, 12.9% were non capsular, and 2.0% corresponded to other serotypes (10 a, 1 d, 1 e and 2 f). Of the total number of isolates, 12.0% produced beta lactamase, 13.9% were resistant to ampicillin, 12.7% to trimethoprim sulfamethoxazole (SXT), 5.4% to chloramphenicol, 1% to cefuroxime. All isolates were susceptible to ceftriaxone. During the 10-year period, resistance to SXT increased from 5% to 13%. A significant decrease in meningitis cases was detected among children under one-year old and in the 1 to 5 age group. Before introducing the vaccine, an annual average of 43 and 23 isolates for each of these groups were received. During 2002, 10 and 6 isolates, respectively, were received for each group. Surveillance of invasive H. influenzae isolates has allowed the evaluation of Hib vaccine impact, as well as the detection of an increase of non-capsular isolates, and changes in resistance patterns.

Adolescent↗

PubMed2003

[Accuracy of the slide agglutination method evaluated with PCR in typing Haemophilus influenzae isolates].

In 1998, the Colombian government initiated an immunization program for children under one year of age with a Haemophilus influenzae capsular type b conjugate vaccine. After two years, the surveillance program of the Colombian Instituto Nacional de Salud Microbiology Group reported a 40% decrease in meningitis cases caused by H. influenzae. This effect was attributed to the vaccination. The surveillance program uses the standardized slide agglutination technique to serotype H. influenzae. The current study validated the accuracy of the slide agglutination method by means of the PCR technique. From children under five years of age, 146 isolates were obtained. These were collected between 1999 and 2002, and were characterized by biochemical tests and serotyped by the INS as part of the surveillance program. PCR confirmed 93% of the H. influenzae serotype b and 92% of the other serotypes. When the slide agglutination technique is conducted under a strict quality control program, it remains a sensitive and specific tool for serotyping H. influenzae.

Agglutination Tests↗

PubMed2003

[Phenotype characterization of environmental Cryptococcus neoformans isolates].

Cryptococcosis is caused by the three varieties of C. neoformans with physiological and virulence differences, some of which have been studied to determine biological aspects of this microorganism. The phenotypical aspects of environmental isolates from varieties grubii and gattii were evaluated to establish differences associated with their life cycle and virulence. To this end, 28 and 31 strains of C. neoformans serotypes A (var. grubii) and C (var. gattii) were studied. The microscopic and macroscopic morphology on Sabouraud agar and soils, growth rate at 37 degrees C, production of 22 extracellular enzymes, haploid fructification, mating type, killer toxin sensitivity patterns and virulence in BALB/c mice were evaluated. No differences were observed between the two varieties regarding microscopic and macroscopic morphology or growth at 37 degrees C (p > 0.05). However, a decrease in the cellular and capsular sizes of yeast in soil, as compared to Sabouraud, was observed (p < 0.05). Additionally, higher enzimatic activity of proteases, phospholipases, phenoloxidase and beta-glucosidase was observed in var. grubii isolates as compared to var. gattii (p < 0.05). In both varieties, structures related with haploid fruitification were observed and all isolates were mating type alpha. Killer toxin sensitivity patterns of the isolates of var. grubii were I and II; in contrast, in var. gattii, seven different patterns were found: I, V, IX-XIII. In the animal model we found that 12 of 22 (54.5%) isolates of var. grubii caused the death of the mice during the observation period, while none of the 14 var. gattii isolates caused it. The decrease in capsular and cellular sizes of the yeast in soil and the frequency of mating type alpha with structures related to haploid fructification suggest an important mechanism of production of infectious particles in nature. Additionally, greater enzimatic activity of var. grubii can be associated with the virulence in the animal model.

Animals↗

PubMed2002

Dissemination of Streptococcus pneumoniae clone Colombia(5)-19 in Latin America.

Streptococcus pneumoniae serotype 5 is the third most common capsular type causing invasive diseases in children younger than 5 years in Latin America. Preliminary data on Colombian serotype 5 isolates indicated a common clonal origin associated with resistance to tetracycline (TET) and chloramphenicol (CHL). We studied 172 S. pneumoniae serotype 5 invasive isolates from Argentina, Brazil, Colombia, Guatemala, Mexico, and Uruguay and confirmed the presence of the Colombia(5)-19 clone throughout Latin America. Fifteen subtypes of a pulsed-field gel electrophoresis pattern and 4 electrophoretic types (ET) were obtained. Most of the isolates from different geographical regions belonged to pattern A (34.3%), subtype A5 (41.9%), and ET1 (91.1%). The A pattern (n = 59) was resistant to TET and had variable resistance to CHL; it was present in Brazil (10.2%), Colombia (78%), Guatemala (8.5%), and Mexico (3.4%). Subtype A5 with variable susceptibility to TET and sensitive to CHL was found in Argentina (29.2%), Mexico (8.3%), and Uruguay (62.5%). Subtypes A1-A4, A7-A8, and A9-A11 (closely related to A) also shared ET1, while subtype A6 was assigned to ET1, ET2, and ET3. Eleven subtypes (n = 21) were found to be specific for one country each. In summary, the S. pneumoniae serotype 5 isolates from Latin American are genetically closely related but show different patterns of antibiotic resistance, probably as a result of horizontal transfer.

Anti-Bacterial Agents↗

PubMed2002

[Acute diarrhea outbreak caused by Shigella flexneri at a school in Madrid, Cundinamarca: phenotypic and genotypic characterization of the isolates].

Shigellosis is an acute diarrhoeal disease that is the main cause of morbidity and mortality in developing countries. In 1997, the Colombian Instituto Nacional de Salud Microbiology Group organized a network surveillance program with the country's Public Health Laboratories (PHLs) to monitor the principal etiological agents responsible for acute diarrhoeal disease. In May, 2001, the PHL of the state of Cundinamarca reported a food poisoning outbreak involving an elementary school community. The main goal of the Microbiology Group involvement was to establish the molecular relationships among the isolates from the outbreak by phenotypic and genotypic methods of characterization. Stool cultures were obtained from 22 of 195 affected individuals. The Microbiology Group confirmed the identification of the isolates by biochemical and serological probes. The antimicrobial susceptibilities were tested against the following battery of antibiotics: chloramphenicol, trimehoprim-sulfamethozazole, cefotaxime, gentamicin, ampicillin and ciprofloxacin. The isolates were subjected to pulsed field gel electrophoresis (PFGE) using the following CDC (U.S. Centers for Disease Control) protocols: Xbal restriction enzyme, Shigella sonnei CDC F2353 as the reference standard, and lambda phage as a molecular weight marker. In 15 of 22 (68%) stool cultures Shigella was recovered, all isolates were identified as Shigella flexneri serotype 6 biotype Newcastle with the same antimicrobial susceptibility profile. PFGE showed that 3 (20%) isolates were identical (100% genetic similarity) and the other 12 (80%) were very closely related (genetic similarity between 86-98%). The network system permitted the INS ready access to the isolates and the implementation of the PFGE permitted a quantitative characterization of the clonal relationship among the isolates from the outbreak.

Acute Disease↗

PubMed2002

[Experimental inoculation of Terminalia catappa seedlings with an environmental isolate of Cryptococcus neoformans var. gattii serotype C ].

In 1997, our laboratory reported for the first time the isolation of Cryptococcus neoformans var. gattii serotype C associated with almond tree (Terminalia catappa) detritus. This finding led to a more detailed follow up of the association between the plant and the yeast. Preliminary data have shown that survival of the yeast in almond trees seedlings goes beyond 100 days. The aim of the present study was to establish if under the conditions previously studied, C. neoformans var. gattii would remain viable for longer periods. A total of 83 almond tree seedings, 20-40 cm high, were inoculated with C. neoformans var. gattii serotype C (INS-755). Assays were carried out inoculating the stem or the soil where the seedlings were planted. Observations were undertaken for a period of up to 12 months. As processing techniques we employed the endophytic fungi procedure (stems), maceration (roots, leaves) and standard suspension method (soils). Additionally, microscopic visualization of the yeast in plant tissues was done with trypan blue plus lactophenol. C. neoformans var. gattii was recovered from the inoculated plants for a period of up to 12 months post-inoculation; additionally, the fungus had the capacity to migrate from the stem to the soil and viceversa, without causing macroscopic or microscopic alterations in the plant tissues. This finding suggests that there appears to be an association between the host plant and C. neoformans var. gattii in the environment.

Coloring Agents↗