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Alejandro Cravioto

Publications and source records attributed to Alejandro Cravioto.

11 recordsLinked to original sources
PubMed2006

Urban dust fecal pollution in Mexico City: antibiotic resistance and virulence factors of Escherichia coli.

Fecal pollution of settled dust samples from indoor and outdoor urban environments, was measured and characterized by the presence of fecal coliforms (FC), and by the characterization of Escherichia coli virulence genes, adherence and antibiotic resistance traits as markers. There were more FC indoors than outdoors (mean values 1089 and 435MPN/g). Among indoor samples, there were more FC in houses with carpets and/or pets. Using a PCR-based assay for six enteropathogenicity genes (belonging to the EAEC, EHEC and EPEC pathotypes) on randomly selected E. coli isolates, there was no significant difference between isolates from indoors and outdoors (60% and 72% positive to at least one gene). The serotypes commonly associated with pathogenic strains, such as O86 and O28, were found in the indoor isolates; whereas O4, O66 and O9 were found amongst outdoor isolates. However, there were significantly more outdoor isolates resistant to at least one antibiotic (73% vs. 45% from indoors) among the strains positive for virulence factors, and outdoor isolates were more commonly multiresistant. There was no relationship between the presence of virulence genes and resistance traits. These results indicate that outdoor fecal bacteria were more likely from human sources, and those found indoors were related to pets and maintained in carpets. This study illustrates the risk posed by fecal bacteria from human sources, usually bearing virulence and resistance traits. Furthermore, the high prevalence of strains carrying genes associated to EAEC or EHEC pathotypes, in both indoor and outdoor environments, adds to the health risk.

Drug Resistance, Bacterial↗
PubMed2006

Changes, trends and challenges of medical education in Latin America.

This paper briefly reviews the current situation of Latin American medical schools and the search to improve the quality and professionalism of medical education through the region. Institutional evaluation and accreditation programs based on nationally ongoing developing standards have been accepted, now optimized and complemented by the framework of the Global & International Standards of Medical Education working jointly with the WFME. More recently, the process has evolved to look into the quality of the outcomes of the medicals as seen by examinations implemented at the end of medical studies and the initiation of medical practice. In addition, there is vision for the application of new programs such as the global minimum essential requirements advanced by the Institute for International Medical Education (IIME). The PanAmerican Federation of Associations of Medical Schools (PAFAMS), an academic, non-governmental organization, is fostering the exchange of ideas and experiences among members, associations and affiliated medical schools geared to focus on the quality and professionalism of the graduates of medical schools in Latin America. These actions also aim to consolidate databases of information on medical education and innovative endeavors in continuing professional education and development through e-learning projects in the region.

Accreditation↗
PubMed2006

Serogroups, K1 antigen, and antimicrobial resistance patterns of Aeromonas spp. strains isolated from different sources in Mexico.

A total of 221 strains of Aeromonas species isolated in Mexico from clinical (161), environmental (40), and food (20) samples were identified using the automated system bioMérieux-Vitek. Antisera for serogroups O1 to 044 were tested using the Shimada and Sakazaki scheme. The K1 antigen was examined using as antiserum the O7:K1C of Escherichia coli. Besides, we studied the antimicrobial patterns according to Vitek AutoMicrobic system. Among the 161 clinical strains 60% were identified as A. hydrophila, 20.4% as A. caviae, and 19.25% as A. veronii biovar sobria. Only A. hydrophila and A. veronii biovar sobria were found in food (55 and 90% respectively) and environmental sources (45 and 10% respectively). Using "O" antisera, only 42.5% (94/221) of the strains were serologically identified, 55% (121/221) were non-typable, and 2.5% (6/221) were rough strains. Twenty-two different serogroups were found, O14, O16, O19, O22, and O34 represented 60% of the serotyped strains. More than 50% of Aeromonas strain examined (112/221) expressed K1 encapsulating antigen; this characteristic was predominant among Aeromonas strains of clinical origin. Resistance to ampicillin/sulbactam and cephazolin was detected in 100 and 67% of Aeromonas strain tested for their susceptibility to antibiotics. In conclusion, antibiotic-resistant Aeromonas species that possess the K1 encapsulating antigen and represent serogroups associated with clinical syndrome in man are not uncommon among Aeromonas strains isolated from clinical, food and environmental sources in Mexico.

Aeromonas↗
PubMed2004

Phenotypic profiles of enterotoxigenic Escherichia coli associated with early childhood diarrhea in rural Egypt.

Enterotoxigenic Escherichia coli (ETEC) causes substantial diarrheal morbidity and mortality in young children in countries with limited resources. We determined the phenotypic profiles of 915 ETEC diarrheal isolates derived from Egyptian children under 3 years of age who participated in a 3-year population-based study. For each strain, we ascertained enterotoxin and colonization factor (CF) expression, the O:H serotype, and antimicrobial susceptibility. Sixty-one percent of the strains expressed heat-stable enterotoxin (ST) only, 26% expressed heat-labile enterotoxin (LT) alone, and 12% expressed both toxins. The most common CF phenotypes were colonization factor antigen I (CFA/I) (10%), coli surface antigen 6 (CS6) (9%), CS14 (6%), and CS1 plus CS3 (4%). Fifty-nine percent of the strains did not express any of the 12 CFs included in our test panel. Resistance of ETEC strains to ampicillin (63%), trimethoprim-sulfamethoxazole (52%), and tetracycline (43%) was common, while resistance to quinolone antibiotics was rarely detected. As for the distribution of observed serotypes, there was an unusually wide diversity of O antigens and H types represented among the 915 ETEC strains. The most commonly recognized composite ETEC phenotypes were ST CS14 O78:H18 (4%), ST (or LTST) CFA/I O128:H12 (3%), ST CS1+CS3 O6:H16 (2%), and ST CFA/I O153:H45 (1.5%). Temporal plots of diarrheal episodes associated with ETEC strains bearing common composite phenotypes were consistent with discrete community outbreaks either within a single or over successive warm seasons. These data suggest that a proportion of the disease that is endemic to young children in rural Egypt represents the confluence of small epidemics by clonally related ETEC strains that are transiently introduced or that persist in a community reservoir.

Anti-Bacterial Agents↗
PubMed2003

Antibody responses to Escherichia coli O157 and other lipopolysaccharides in healthy children and adults.

In Mexico, diarrheal disease due to different serotypes of Escherichia coli is highly prevalent, with only sporadic isolation of O157 non-H7 strains. This could be due to exposure to the O157 or related E. coli lipopolysaccharide (LPS), such as O7 or O116, at an early age. By using enzyme-linked immunosorbent assay (ELISA) and Western blotting, the present study analyzed 605 serum samples from Mexican adults and infants without clinical symptoms of disease for the presence of antibodies to these three E. coli LPSs. The bactericidal activities of homologous and heterologous rabbit and human serum samples against O7, O116, and O157 E. coli LPSs were also determined. By using a cutoff point of 0.7, it was found by the ELISAs that 28 of 562 (5%) of the serum samples from adolescents and adults and 2 of 43 (5%) of the serum samples from infants less than 1 year of age reacted with the O157 LPS. By using cutoff points between 0.4 and 0.699, the proportion of serum samples from both age groups that reacted with the O157 LPS increased to 20%. Western blotting analysis of selected serum samples that showed an intermediate response against the O157 LPS by the ELISAs showed that 61 of 88 (69%) reacted with the same LPS. A similar result was observed for maternal milk samples. The bactericidal activities of rabbit serum samples against the O7, O116, and O157 LPSs showed that they were positive for both homologous and heterologous antigens. Similar results were observed with the human serum samples. O157 non-H7 strains were identified in only 10% of the E. coli strains isolated from 263 Mexican children with and without diarrhea over the past 15 years. This absence of O157:H7 strains in Mexico may be associated with the presence of antibodies against O157 or related E. coli LPSs.

Adult↗
PubMed2003

Abortion, contraceptive use, and adolescent pregnancy among first-year medical students at a major public university in Mexico City.

OBJECTIVE: If properly trained, medical students could become future opinion leaders in health policy and could help the public to understand the consequences of unwanted pregnancies and of abortions. The objective of this study was to analyze the frequency of unwanted pregnancies and induced abortions that had occurred among women who were first-year medical students at a major public university in Mexico City and to compare the experiences of those women with the experiences of the general population of Mexican females aged 15 to 24. METHODS: In 1998 we administered a cross-sectional survey to all the first-year medical students at the National Autonomous University of Mexico, which is the largest university in Latin America. For this study we analyzed 549 surveys completed by female students. RESULTS: Out of the 549 women, 120 of them (22%) had been sexually active at some point. Among those 120 sexually active students, 100 of them (83%) had used a contraceptive method at some time, and 19 of the 120 (16%) had been pregnant. Of those 19 women who had been pregnant, 10 of them had had an illegal induced abortion (in Mexico, abortions are illegal except under a small number of extenuating circumstances). The reported abortion rate among the female medical students, 2%, was very low in comparison with the 11% rate for women of similar ages in the Mexican general population. CONCLUSIONS: The lower incidence of abortion among the female medical students indicates that when young Mexican women have access to medical information and are highly motivated to avoid unintended pregnancy and abortion, they can do so.

Abortion, Illegal↗
PubMed2002

Bleeding peptic ulcers and presence of Helicobacter pylori by various tests: a case-control study.

BACKGROUND: Virulence factors of Helicobacter pylori are associated with peptic ulcer disease and may be also associated with bleeding peptic ulcers (BPU). AIM: To determine whether H. pylori and/or the cytotoxin-associated gene (cagA) can increase the risk of bleeding in peptic ulcers. PATIENTS: Sixty-seven patients were studied. Thirty had BPU, 20 had non-bleeding peptic ulcers (NBPU), and 17 were control subjects (NPU). METHODS: The prevalence of H. pylori was assessed by the urease fast test, histological examination, serology, and 16S ribosomal RNA and cagA gene amplification by polymerase chain reaction (PCR). RESULTS: Histology and PCR showed greater sensitivity for diagnosis of H. pylori under bleeding circumstances when compared with other tests. Association of H. pylori was greater in the NBPU group (odds ratio [OR] 4.91, P = 0.06) than in the BPU group (OR 1.27, P = NS) when compared with the control group. When the BPU and NBPU groups were compared, H. pylori was found more often in the NBPU group (OR 0.26, P < 0.10 ). The cagA-positive gene showed a similar distribution in the three groups. The titres for anti-CagA immunoglobulin A (IgA) antibodies were higher in NBPU patients (83%) than in BPU or control patients. Furthermore, anti-urease immunoglobulin G (IgG) was detected more frequently among BPU and NBPU patients. CONCLUSIONS: NBPU patients had the highest prevalence of H. pylori by PCR. It seems unlikely that either H. pylori or the cagA-positive gene act as significant risk factors for bleeding in peptic ulcers. The lower prevalence of the microorganism among patients who bleed cannot be explained as an artificial finding.

Antigens, Bacterial↗
PubMedDate not supplied

The use of microarrays for studying the pathogenesis of Helicobacter pylori.

At present, the genomes of various microorganisms have been completely sequenced, and many others are in progress. The availability of this level of information and the computational analysis of the described sequences have led to the development of new genomic areas such as: analysis in silico, comparative genomics, functional genomics, transcriptomics, proteomics, and pharmacogenomics. Microarray technology is a powerful tool for analyzing the expression profile of thousands of genes in a global way and can be applied to the study of various biological systems. Using the complete sequences for both the H. pylori and human genome that are available in the data bases, a number of researchers have revealed important information. Some of these data offer a glimpse into the great genetic diversity of H. pylori, the differential genetic expression between the strains that shows the complexity of the response of microorganisms to different conditions of development, and into the association of gene cluster expression with clinical outcome. Other groups have examined the global transcriptional response of gastric epithelial cells to H. pylori. The majority of these studies report an alteration in gene expression related to transcription functions, transduction signals, cell cycle regulation and differentiation, development factors, proliferation/apoptosis balance, expression of membrane proteins, and inflammatory response.

Animals↗