Jorge F. Cerna-Cortes

Presence of some indicator bacteria and diarrheagenic E. coli pathotypes on jalapeño and serrano peppers from popular markets in Pachuca City, Mexico

The chili pepper is a very important crop in Mexico. Diarrheagenic E. coli pathotypes (DEPs) are important foodborne pathogens in different countries including Mexico. No data exists on DEPs presence on fresh jalapeño and serrano pepper and little data have been published on the microbiological quality of these peppers. The frequencies of coliform bacteria (CB), thermotolerant coliforms (TC), E. coli and DEPs were determined for jalapeño and serrano peppers. Of 100 serrano samples, CB, TC, E. coli and DEPs were identified in 100, 90, 58 and 36%, respectively. Of 100 jalapeño samples, CB, TC, E. coli and DEPs were identified in 100, 88, 38 and 14%, respectively. Identified DEPs included enterotoxigenic E. coli (ETEC) and Shiga toxin-producing E. coli (STEC). STEC were isolated from 36% of serrano samples and 14% of jalapeño samples. ETEC were isolated from 12% of serrano samples and 2% of jalapeño samples. Both STEC and ETEC were identified in 14 serrano samples and 2 jalapeño samples. No E. coli O157:H7 were detected in any STEC-positive samples. Jalapeño and serrano peppers could be an important factor contributing to the endemicity of DEPs-caused gastroenteritis in Mexico.

First insights into the genetic diversity of Mycobacterium tuberculosis isolates from HIV-infected Mexican patients and mutations causing multidrug resistance

BackgroundThe prevalence of infections with Mycobacterium tuberculosis (MTb) and nontuberculous mycobacteria (NTM) species in HIV-infected patients in Mexico is unknown. The aims of this study were to determine the frequency of MTb and NTM species in HIV-infected patients from Mexico City, to evaluate the genotypic diversity of the Mycobacterium tuberculosis complex strains, to determine their drug resistance profiles by colorimetric microplate Alamar Blue assay (MABA), and finally, to detect mutations present in kat G, rpo B and inh A genes, resulting in isoniazid (INH) and rifampin (RIF) resistance.ResultsOf the 67 mycobacterial strains isolated, 48 were identified as MTb, 9 as M. bovis, 9 as M. avium and 1 as M. intracellulare. IS6110-RFLP of 48 MTb strains showed 27 profiles. Spoligotyping of the 48 MTb strains yielded 21 patterns, and 9 M. bovis strains produced 7 patterns. Eleven new spoligotypes patterns were found. A total of 40 patterns were produced from the 48 MTb strains when MIRU-VNTR was performed. Nineteen (39.6%) MTb strains were resistant to one or more drugs. One (2.1%) multidrug-resistant (MDR) strain was identified. A novel mutation was identified in a RIF-resistant strain, GAG → TCG (Glu → Ser) at codon 469 of rpo B gene.ConclusionsThis is the first molecular analysis of mycobacteria isolated from HIV-infected patients in Mexico, which describe the prevalence of different mycobacterial species in this population. A high genetic diversity of MTb strains was identified. New spoligotypes and MIRU-VNTR patterns as well as a novel mutation associated to RIF-resistance were found. This information will facilitate the tracking of different mycobacterial species in HIV-infected individuals, and monitoring the spread of these microorganisms, leading to more appropriate measures for tuberculosis control.

MicroRNAs in cervical cancer: evidences for a miRNA profile deregulated by HPV and its impact on radio-resistance.

Cervical carcinoma (CC) is one of the most common cancers and a leading cause of mortality in women worldwide. Epidemiologic and experimental data have clearly demonstrated a causal role of high-risk Human Papillomavirus (HR-HPV) types in CC initiation and progression, affecting the cellular processes by targeting and inactivating p53 and pRB host proteins. HR-HPV E5, E6 and E7 oncoproteins have the ability to deregulate several cellular processes, mostly apoptosis, cell cycle control, migration, immune evasion, and induction of genetic instability, which promote the accumulation of mutations and aneuploidy. In this scenario, genomic profiles have shown that aberrant expression of cellular oncogenic and tumor suppressive miRNAs have an important role in CC carcinogenesis. It has been stated that HPV infection and E6/E7 expression are essential but not sufficient to lead to CC development; hence other genetic and epigenetic factors have to be involved in this complex disease. Recent evidence suggests an important level of interaction among E6/E7 viral proteins and cellular miRNA, and other noncoding RNAs. The aim of the current review is to analyze recent data that mainly describe the interaction between HR-HPV established infections and specific cellular miRNAs; moreover, to understand how those interactions could affect radio-therapeutic response in tumor cells.

Differential Macrophage Response to Slow- and Fast-Growing Pathogenic Mycobacteria

Nontuberculous mycobacteria (NTM) have recently been recognized as important species that cause disease even in immunocompetent individuals. The mechanisms that these species use to infect and persist inside macrophages are not well characterised. To gain insight concerning this process we used THP-1 macrophages infected with M. abscessus, M. fortuitum, M. celatum, and M. tuberculosis. Our results showed that slow-growing mycobacteria gained entrance into these cells with more efficiency than fast-growing mycobacteria. We have also demonstrated that viable slow-growing M. celatum persisted inside macrophages without causing cell damage and without inducing reactive oxygen species (ROS), as M. tuberculosis caused. In contrast, fast-growing mycobacteria destroyed the cells and induced high levels of ROS. Additionally, the macrophage cytokine pattern induced by M. celatum was different from the one induced by either M. tuberculosis or fast-growing mycobacteria. Our results also suggest that, in some cases, the intracellular survival of mycobacteria and the immune response that they induce in macrophages could be related to their growth rate. In addition, the modulation of macrophage cytokine production, caused by M. celatum, might be a novel immune-evasion strategy used to survive inside macrophages that is different from the one reported for M. tuberculosis.

The organization of two rRNA (rrn) operons of the slow-growing pathogen Mycobacterium celatum provides key insights into mycobacterial evolution

The slow-growing Mycobacterium celatum is known to have two different 16S rRNA gene sequences. This study confirms the presence of two rrn operons and describes their organization. One operon (rrnA) was found to be located downstream from murA and the other (rrnB) was found downstream from tyrS. The promoter regions were sequenced, and also the intergenic transcribed spacer (ITS1 and ITS2) regions separating the 16S rRNA, 23S rRNA and 5S rRNA gene coding regions. Analysis of the RNA fraction revealed that rrnA is regulated by two (P1 and PCL1) promoters and rrnB is regulated by one (P1). These data show that the two rrn operons of M. celatum are organized in the same way as the two rrn operons of classical fast-growing mycobacteria. This information was incorporated into a phylogenetic analysis of the genus based on both 16S rRNA gene sequences and (where possible) the number of rrn operons per genome. The results suggest that the ancestral Mycobacterium possessed two (rrnA and rrnB) operons per genome and that subsequently, on two separate occasions, an operon (rrnB) was lost, leading to two clusters of species having a single operon (rrnA); one cluster includes the classical pathogens and the other includes Mycobacterium abscessus and Mycobacterium chelonae.

Consumption of street-vended beverage a potential exposure risk for non-O157 enterohemorrhagic Escherichia coli infection: the importance of testing for virulence loci.

To the Editor—We read with great interest the article by Hadler et al [1] that established international travel as the main exposure risk for non-O157 Shiga toxin–producing Escherichia coli (STEC) infection compared with patients with O157 STEC infection (15.3% vs 2.5%, respectively; P , .01). Up to 60% of US visitors to Mexico develop travelers’ diarrhea [2], which has been associated with non-O157 STEC infections [3]. In Mexico, non-O157 STEC strains have been isolated from persons with diarrheal episodes [4] and from food items [5], but the frequency of nonO157 STEC and other diarrheagenic E. coli pathotypes (DEPs) among beverages is unknown. We recently analyzed 56 samples of street-vended beverages for enteropathogens, by standard methods [6], and for DEPs, by polymerase chain reaction identification of virulence loci [7, 8]; STEC strains were further characterized by the Oxoid agglutination test for the O157 serotype. Samples were collected during September–December 2010 at La Villa, a major tourist attraction north of Mexico City that has a high concentration of street-food vendors and an estimated average of 20 million national and international visitors per year. We found that 26 (46.4%) of the 56 samples were contaminated with E. coli. The most frequently contaminated beverages were horchata (a rice-based traditional Mexican beverage), with 13 of 21 positive samples (62%), and fresh strawberry drink, with 6 of 10 positive samples (60%). In 3 of the 26 E. coli– positive samples (11.5%), we isolated non-O157 STEC strains in sufficient numbers to cause disease (.2.8 3 10 colony-forming units per liter of sample; Table 1); no other DEP was identified from these beverages. Another 3 of 21 (14%) Horchata samples harbored other enteropathogens (1 sample had Citrobacter freundii, 1 had Aeromonas hydrophila, and 1 had group B Salmonella and A. hydrophila). Of note, as shown in Table 1, all of the non-O157 STEC strains isolated had stx1 and/or stx2 genes and were positive for the gene encoding intimin (ie, eaeA). Together, the presence of Shiga toxin and intimin genes defines enterohemorrhagic E. coli (EHEC), a subset of pathogenic STEC strains that can cause hemorrhagic colitis and hemolytic uremic syndrome [9]. Our study shows that consumption of street-vended beverages is a potential source of non-O157 EHEC for both the local population and for individuals from industrialized countries who visit Mexico. A recent report associated beverages containing ice cubes with a higher risk for travelers’ diarrhea [10]. Furthermore, our study highlights the importance of characterizing virulence loci for STEC/EHEC identification, as has been shown by other studies [3–5]. Strategies to improve the safety of streetvended beverages and food, such as educational interventions for food handlers and consumers, as well as continuous surveillance for both the main pathogens and sources of contamination, will reduce the risk posed by these items.

A microRNA expression signature for clinical response in locally advanced cervical cancer

OBJECTIVE Nearly 50% of patients who are diagnosed with locally advanced cervical cancer have an unfavorable pathological response to conventional treatment. MicroRNAs (miRNAs) are potential biomarkers in cervical cancer; however, their role in identifying patients who do not respond to conventional treatment remains poorly investigated. Here, we identify a set of miRNAs that can be used as molecular markers to predict the pathological response in locally advanced cervical cancer patients receiving radiation and chemotherapy treatment. METHODS Forty-one patients diagnosed with locally advanced cervical cancer were invited to participate in this study and enrolled after they signed an informed consent. Two patient cohorts were randomized for miRNA expression profiling, a discovery cohort (n=10) and a validation cohort (n=31); profiling was performed by means of a miScript miRNA PCR Array. After a median clinical follow-up of 45months, statistical analysis was performed to identify miRNAs that could discriminate non-responders from complete pathological responders to conventional treatment. RESULTS miRNA expression profiling identified 101 miRNAs that showed significant differences between non-responders and complete pathological responders (p<0.05). Seven differentially expressed miRNAs were selected, and their expression patterns were confirmed in the validation phase; thus, miR-31-3p, -3676, -125a-5p, -100-5p, -125b-5p, and -200a-5p and miR-342 were significantly associated with clinical response. Expression of this miRNA signature above the median level was a significant predictor of non-response to standard treatment (p<0.001). CONCLUSIONS These seven validated miRNA signatures could be used as molecular biomarkers of chemo- and radio-resistance in locally advanced cervical cancer patients.

Isolation of Mycobacterium mucogenicum from street-vended chili sauces: a potential source of human infection.

Recently human illnesses due to nontuberculous mycobacteria (NTM) have increased worldwide, but the sources of transmission have not been well established. Street-vended food is widely consumed in Mexico, and chili sauces are the most typical dressings for this food. Thus, we examined street-vended chili sauces as a possible source for NTM. Fifty-one street-vended chili sauces were collected in different areas of Mexico City during the spring of 2007. NTM were recovered from 6% (3 of 51) of samples, and in all cases the identified species was Mycobacterium mucogenicum. This mycobacterium has been associated with human illness; therefore, street-vended chili sauces are a potential source of NTM infection.

Molecular basis of oxidative stress in gouty arthropathy

Gout is a disorder of urate metabolism in which persistent high urate levels in the extracellular fluids result in the deposition of monosodium urate (MSU) crystal in joints and periarticular tissues. In recent years, this disease represents an increasingly common health problem, so the pace of investigation in the field has accelerated tremendously. New research advances in the pathogenesis of hyperuricemia and in the understanding of how MSU crystals induce an acute gouty attack have been focused in this review on the processes of inflammation and involvement of the innate immune response; in addition, we discuss new knowledge about the role of the reactive oxygen species in establishing oxidative stress in MSU crystal-induced arthritis.

Microbiological Quality of Ready-to-Eat Vegetables Collected in Mexico City: Occurrence of Aerobic-Mesophilic Bacteria, Fecal Coliforms, and Potentially Pathogenic Nontuberculous Mycobacteria

The aims of this study were to evaluate the microbiological quality and the occurrence of nontuberculous mycobacteria (NTM) in a variety of salads and sprouts from supermarkets and street vendors in Mexico City. Aerobic-mesophilic bacteria (AMB) were present in 100% of RTE-salads samples; 59% of samples were outside guidelines range (>5.17 log10 CFU per g). Although fecal coliforms (FC) were present in 32% of samples, only 8% of them exceeded the permissible limit (100 MPN/g). Regarding the 100 RTE-sprouts, all samples were also positive for AMB and total coliforms (TC) and 69% for FC. Seven NTM species were recovered from 7 salad samples; they included three M. fortuitum, two M. chelonae, one M. mucogenicum, and one M. sp. Twelve RTE-sprouts samples harbored NTM, which were identified as M. porcinum (five), M. abscessus (two), M. gordonae (two), M. mucogenicum (two), and M. avium complex (one). Most RTE-salads and RTE-sprouts had unsatisfactory microbiological quality and some harbored NTM associated with illness. No correlation between the presence of coliforms and NTM was found. Overall, these results suggest that RTE-salads and RTE-sprouts might function as vehicles for NTM transmission in humans; hence, proper handling and treatment before consumption of such products might be recommendable.