Relación entre la variabilidad genotípica de los factores de virulencia vacA y cagA y la susceptibilidad antimicrobiana de cepas de Helicobacter pylori aisladas de adultos mexicanos con padecimientos gástricos

Helicobacter pylori (H. pylori) es una bacteria Gram negativa, microaerofílica que coloniza el estómago de los humanos. Es el agente causal de la gastritis, úlcera péptica y cáncer gástrico. En México, la erradicación de la infección por Helicobacter pylori es una prioridad debido a la elevada seroprevalencia, sin embargo existe poca información acerca de las tasas de resistencia a antibióticos en aislamientos de H. pylori en nuestro país. El incremento en la resistencia a antibióticos constituye un problema mundial y dificulta el tratamiento de las infección por H. pylori. Con el objetivo de determinar la relación entre la resistencia, la presencia y variabilidad de los genes de virulencia vacA y cagA; analizamos la frecuencia de la resistencia a los antibióticos claritromicina, metronidazol y amoxicilina en cepas de H. pylori aisladas de pacientes con diferentes padecimientos gástricos. Se realizó la caracterización de un total de 49 aislamientos clínicos de H. pylori provenientes de 49 pacientes con padecimientos de gastritis crónica activa, gastritis crónica activa folicular, metaplasia intestinal y cáncer gástrico, los cuales fueron reclutados en el servicio de endoscopía del Instituto Nacional de Cancerología (INCAN) en 1997, 2000 y 2001. Se analizó la susceptibilidad a los antimicrobianos claritromicina, metronidazol y amoxicilina. Todos los aislamientos fueron susceptibles a amoxicilina, mientras que 28 (57%) fueron resistentes a metronidazol y 2 (4%) fueron resistentes a metronidazol y claritromicina. La prevalencia de la resistencia a metronidazol incrementó del 35% en 1997, a 54% en 2000 y 74% en 2001. El análisis de la secuencia del gen que codifica para la subunidad 23S del RNA ribosomal de las dos cepas de H. pylori resistentes a metronidazol y claritromicina mostró que una de ellas tenía la mutación A2142G y la otra las mutaciones A2143G y T2182C. Todas las cepas presentaron el gen vacA y el 77.5% de las muestras el gen cagA. El 84.8% de las cepas citotóxicas son cagA + , de las cuales el 89.2% tienen el genotipo s1m1. La resistencia a metronidazol se asoció con cepas cagA – con una frecuencia de 82% (9/11). No se encontró una correlación significativa entre los alelos vacA s/m y la resistencia a metronidazol. El análisis del polimorfismo genético de los aislamientos, mediante la amplificación al azar de DNA polimórfico (RAPD), no mostró relación genética entre las cepas.Helicobacter pylori (H. pylori) is a Gram-negative microaerophilic bacteria, that inhabits the stomach of humans. H. pylori is the causal agent of gastritis, peptic ulcer and gastric cancer. Eradication of Helicobacter pylori infection in Mexico is a priority due to the elevated seroprevalence, however, there is yet very little information about antibiotic resistance rates in H. pylori isolates in our country. The increased prevalence of antibiotic resistance has become a world wide problem and makes difficult the treatment of H. pylori infection. The aim of this study was to determine the relation between antibiotics resistance and presence and variability of the virulence associated vacA and cagA genes. Susceptibility to clarithromycin, metronidazole, and amoxicillin of H. pylori strains isolated from patients with different clinical outcome was analyzed. We made the characterization of 49 H. pylori strains isolated from patients with active chronic gastritis, active chronic gastritis with lymphoid follicles, intestinal metaplasia and gastric cancer, and all patients were recruited in the Instituto Nacional de Cancerologia (INCAN) at endoscopy unit during 1997, 2000 and 2001. Antimicrobial susceptibility to clarithromycin, metronidazole and amoxicillin was analyzed. All isolated strains were susceptible to amoxicillin, 28 (57%), metronidazole resistant and 2 (4%) were both clarithromycin and metronidazole resistant. The prevalence of resistance to metronidazole increased from 35% in 1997 to 54% in 2000 and to 74% in 2001. Sequence analysis of the 23S rRNA encoding gene of the two clarithromycin resistant strains showed the A2142G mutation in one, and the A2143G and T2182C mutations in the other. The vacA gene was detected in all the studied strains and cagA gene could be identified in 77.5% of the strains. With regard to cytotoxicity 84.8% were cagA + , of which 89.2% had the s1m1 genotype. Metronidazole resistance was associated with cagA – strains with a frequency of 82 % (9/11). No significant correlation was found between vacA s/m alleles and metronidazole resistance. Typing by random amplified polymorphic DNA (RAPD) showed no genetic relation among the strains

Serological Biomarkers for the Prediction and Detection of Human Papillomavirus Associated Cancers

High-risk human papillomavirus (HPV) types are not only associated to uterine cervical cancer, but also to a fraction of cancers of the vulva, vagina, penis, anus, head and neck. An HPV infection generates a protective humoral immune response against the capsid proteins L1 and L2; however, an immune response against other HPV early proteins is also generated. This latter is not a protective response, but those antibodies can be useful as biomarkers of the status of the infection and/or the stage of the cancer lesion. Until now, there are no conclusive results regarding the use of anti-HPV antibodies as biomarkers in diagnosis. In this review, we hereby summarized the actual panorama of the humoral immune response against different HPV early proteins during the development of the disease as possible biomarkers for the prediction and detection of HPV-associated cancers

Clonal and Horizontal Dissemination of Klebsiella pneumoniae Expressing SHV-5 Extended-Spectrum β-Lactamase in a Mexican Pediatric Hospital

One hundred eighty-four clinical isolates of Klebsiella pneumoniae were recovered from August 1996 to October 1997 at the Pediatric Hospital of the Instituto Mexicano del Seguro Social in Mexico City, Mexico. Most of the isolates were collected from the neonatal intensive care unit and infant wards, which are located on the same floor of the hospital. Isolates were genotypically compared by pulsed-field gel electrophoresis with XbaI restriction of chromosomal DNA. Of 184 clinical isolates, 91 belonged to cluster A and comprised three subtypes (A1, A2, and A3), while 93 isolates, comprising two minor clones, B (10 isolates) and C (7 isolates), and 76 unique patterns, were considered unrelated isolates (URI). Susceptibility patterns were indistinguishable in both groups. Fifty extended-spectrum β-lactamase-producing isolates, including 34 from clone A and 16 from URI, were examined for further studies. Molecular and genetic analysis showed that 47 of 50 clinical isolates expressed the SHV-5 β-lactamase. This enzyme, in combination with TEM-1, was encoded in a ≥170-kb conjugative plasmid. Results indicate that dissemination of this resistance was due to clonal and horizontal spread