Frequency and expression of genes involved in adhesion and biofilm formation in Staphylococcus aureus strains isolated from periodontal lesions.

BACKGROUND/PURPOSE: The aim of this study was to characterize the Staphylococcus aureus strains isolated from periodontal lesions of patients, to determine the expression of genes involved in cell adhesion upon their infection of human epithelial cells using an in vitro model, its biofilm formation, and its resistance to antibiotics. METHODS: S. aureus was analysed by PCR, Kirby-Bauer, and pulsed-field gel electrophoresis (PFGE), measuring gene expression by real-time PCR after infection of human cells in vitro. RESULTS: S. aureus was identified in 18.6% (50/268) of the samples. All strains (n = 50) possessed the virulence genes spa (Staphylococcal protein A), coa (coagulase), and icaAB (intercellular adhesin); 96% (n = 48) possessed clfB (clumping factor B), and 88% (n = 44) possessed ebps (elastin-binding protein) and sdrD (serine aspartate repeat protein D). All strains were resistant to methicillin, ampicillin, dicloxacillin, cefotaxime, and penicillin, and were multidrug resistant to 6-12 antibiotics. PFGE analysis showed 37 different pulsed-field types and most strains (60.4%) had a unique pulsed-field type. Twenty-four distinct combinations of virulence genes and antibiotic-resistant phenotypes were identified. CONCLUSION: Although S. aureus has been considered a transient member of the oral microbiota, our results indicate a high-level expression of virulence genes and multidrug resistance in the strains isolated from periodontal lesions. These strains might complicate the successful treatment of the disease.

Virulence factors, antibiotic resistance phenotypes and O-serogroups of Escherichia coli strains isolated from community-acquired urinary tract infection patients in Mexico.

BACKGROUND/PURPOSE: Uropathogenic Escherichia coli (UPEC) strains isolated from patients with community-acquired urinary tract infections (UTIs) were assessed to determine the prevalence of virulence genes, antibiotic resistance, and the O-serogroup of the strains. METHODS: Consenting patients with community-acquired UTI were enrolled at Unidad Médica Familiar Number 64 (Instituto Mexicano del Seguro Social, Estado de Mexico, Mexico) and 321 urine samples were collected. Polymerase chain reaction (PCR) was used to assess 24 virulence genes and 14 O-serogroups. The Kirby-Bauer method was used to evaluate the antibiotic susceptibility of the isolated strains to 12 commonly used antibiotics. RESULTS: A total of 194 strains were identified as E. coli using standard biochemical tests, followed by PCR amplification of 16S ribosomal RNA gene. Only 58.2% of the strains belonged to the assessed 14 O-serogroups. The serogroups O25, O15, O8, and O75 were present in 20.6%, 17%, 6.1%, and 4.6% of strains, respectively. The most frequently occurring virulence genes among UPEC strains included kpsMT (92.2% strains), usp (87.1%), irp2 (79.3%), iha (64.9%), fim (61.3%), set (36%), astA (33.5%), pap (24.7%), and papGII (21.1%). In addition, 97% of the strains were multi-drug resistant (coresistance to 3-11 antibiotics). CONCLUSION: The isolated UPEC strains predominantly belonged to three serogroups (O25, O15, and O8), harboured numerous virulence genes, and are multiresistant to antibiotics. The findings of this study could be used to orient UTI treatment strategies and in epidemiological studies in Mexico.

Comprehensive expression analysis of pathogenicity genes in uropathogenic Escherichia coli strains.

In this study, we investigated distinct expression patterns of genes encoding iron-acquisition systems, adhesins, protectins, and toxins in human uroepithelial cells infected with 194 uropathogenic Escherichia coli (UPEC) strains in vitro. We assessed the association of these genes with antibiotic resistance genes in this group of UPEC strains, previously characterised by polymerase chain reaction (PCR). Strains were isolated from patients with urinary tract infections (UTIs) from Unidad Médica Familiar de Salud Pública, located in Estado de México, México. Antibiotic resistance genes were identified by PCR, and the expression of virulence genes was detected by reverse-transcriptase-PCR after in vitro infection of cultured A431 human keratinocytes derived from a vulvar epidermoid carcinoma. The most frequently expressed virulence genotypes among the investigated UPEC strains included usp (68%), iha (64.9%), kpsMT (61.3%), fim (58.2%), irp2 (48.4), papC (33.5%), set (31.4%) and astA (30.9%), whereas the most frequently detected antibiotic resistance genes were tet(A) (34%), sul1 (31.4%) and TEM (26.3%). Furthermore, the most abundant pattern of gene expression (irp2/fim/iha/kpsMT/usp), associated with 8 different combinations of antibiotic resistance genotypes, was exhibited by 28 strains (14.4%). Taken together, these results indicate collective participation of distinct virulence UPEC genotypes during in vitro infection of cultured human epithelial cells, suggesting their potential involvement in UTI pathogenesis.

Frequency of vacA, cagA and babA2 virulence markers in Helicobacter pylori strains isolated from Mexican patients with chronic gastritis.

BACKGROUND: Helicobacter pylori has been strongly associated with chronic gastritis, peptic and duodenal ulcers, and it is a risk factor for gastric cancer. Three major virulence factors of H. pylori have been described: the vacuolating toxin (VacA), the cytotoxin-associated gene product (CagA) and the adhesion protein BabA2. Since considerable geographic diversity in the prevalence of H. pylori virulence factors has been reported, the aim of this work was to establish the H. pylori and vacA, cagA and babA2 gene status in 238 adult patients, from a marginal urban area of Mexico, with chronic gastritis. METHODS: H. pylori was identified in cultures of gastric biopsies by nested PCR. vacA and cagA genes were detected by multiplex PCR, whereas babA2 gene was identified by conventional PCR. RESULTS: H. pylori-positive biopsies were 143 (60.1%). All H. pylori strains were vacA+; 39.2% were cagA+; 13.3% were cagA+ babA2+ and 8.4% were babA2+. Mexican strains examined possessed the vacA s1, m1 (43.4%), s1, m2 (24.5%), s2, m1 (20.3%) and s2, m2 (11.9%) genotypes. CONCLUSION: These results show that the Mexican patients suffering chronic gastritis we have studied had a high incidence of infection by H. pylori. Forty four percent (63/143) of the H. pylori strains analyzed in this work may be considered as highly virulent since they possessed two or three of the virulence markers analyzed: vacA s1 cagA babA2 (9.8%, 14/143), vacA s1 babA2 (4.9%, 7/143), and vacA s1 cagA (29.4%, 42/143). However, a statistically significant correlation was not observed between vacAs1, cagA and babA2 virulence markers (chi2 test; P > 0.05).

FIZ15 bacteriophage increases the adhesion of pseudomonas aeruginosa to human buccal epithelial cells

FIZ15 es un bacteriófago temperado que causa conversión lisogénica en la cepa PAO1 de Pseudomonas aeruginosa. Este fago induce un cambio superficial en el antigeno O de su lisógena ( que es el receptor fágico) el cual es responsable de que ésta presente una disminución en a sensibilidad a la fagocitosis y al efecto bactericida del suero. En este trabajo reportamos que al lisogenizar a la cepa PAO1 el fago FIZ15 aumenta 1.5 veces su adherencia in vitro a células bucopiteliales humanas mediante un mecanismo, adicional al mediado por pili, que requiere que las bacterias estén metabólicamente activas, puesto que el incremento en la adhesión que presentó la lisógena no ocurrió cuando se adicionó un desacoplante de la fosforilación oxidativa a la mezcla célula-bacteria durante el ensayo de adhesión, tratamiento que no afectó la adhesión de la cepa no lisógena. Una mutante espontánea de PAO1 resistente a FIZ15 (sin receptor fágico o con receptor alterado) mostró una adhesión 4 veces mayor que PAO1 en ausencia de desacoplante. Cuando se adicionó el desacoplante, la adhesión de la mutante que el antigeno O de Pseudomonas aeruginosa juega un importante papel en a adhesión de este bacilo a células bucopiteliales humanas mediante un mecanismo dependiente de energia y constituyen otro ejemplo de conversión lisogénica