Occurrence and genetic association of selected virulence factors in clinical Escherichia coli isolates

Escherichia coli Strains with Virulent Factors Typical for Uropathogens were Isolated from Sinuses from Patients with Chronic Rhinosinusitis-Case Report

Escherichia coli were isolated from three patients with chronic rhinosinusitis (CRS) by intraoperative sinus tissue biopsy. Taking into account the unusual replicative niche and previous treatment failures, it was decided to focus on the virulence and drug resistance of these bacteria. The strains turned out to be multi-sensitive, but the rich virulence factors profile of bacteria typical for phylogenetic group B2 deserved attention. Tests were carried out for the presence of 32 genes using the PCR method. Particularly noteworthy are the toxins Cnf-1, HlyA, Usp-an extensive iron uptake system (enterobactin, salmochelin, yersiniabactin and outer membrane hemin receptor ChuA)-SPATE autotransporters such as vat and pic, Ag43 autoaggregative protein-important for biofilm formation-and TosA/B which enhance the fitness of E.coli. All these virulence factors are identified predominantly in UPEC strains and provide a fitness advantage during colonization of the sinuses. Patients with CRS should be asked for past or present UTI. The specific virulence factors of E. coli that facilitate the colonization of the GI tract and urinary tract may also favor the colonization of a new ecological niche (sinuses) as a result of microbial imbalance or dysbiosis.

Virulence factors of uropathogenic Escherichia coli of urinary tract infections and asymptomatic bacteriuria in children

BACKGROUND/PURPOSE

The clinical aspects of virulence genes of uropathogenic Escherichia coli (UPEC) are not fully understood. This study compared the presence of virulence genes in UPEC isolated from urinary tract infections (UTIs) and asymptomatic bacteriuria (ABU) in children.

METHODS

The study included children with UTI (n = 15) or ABU (n = 49) treated at Chung-Ang University Yongsan Hospital between 2010 and 2011. The strains were acquired from each urine sample collected, and 18 major virulence genes were detected by polymerase chain reaction. Antimicrobial susceptibility of all UPEC isolates was determined.

RESULTS

Sixty-four E. coli strains were isolated from the urine samples. The most commonly identified virulence gene in both groups was fimH (100.0% in the UTI group and 95.9% in the ABU group). The UTI isolates showed a higher prevalence of papEF and fyuA, and a lower prevalence of feoB than ABU isolates (p < 0.01 for all). The profile of virulence gene, fimH(+)kpsMTII(+)feoB(+) also showed a significant difference between the two groups (p < 0.01). Isolates from ABU were more resistant to most antimicrobials tested. The presence of papEF, feoB, and fyuA also correlated with the antimicrobial susceptibility of UPEC.

CONCLUSION

The virulence gene repertoire was different in the UPEC of UTI and ABU. The papEF, feoB, and fyuA genes showed meaningful differences between the two groups and may have an important role in the pathogenesis of overt UTI.

PCR assay for detection and differentiation of K88ab(1), K88ab(2), K88ac, and K88ad fimbrial adhesins in E. coli strains isolated from diarrheic piglets

Primers were designed and prepared and conditions were determined for PCR detection and differentiation of enterotoxigenic E. coli bacterial strains isolated from diarrheic pigs. Primers K88/1 and K88/2 are 25 bp oligomers that correspond to a region of genes encoding one of serological variants of the K88 antigen (K88ab(1), K88ab(2), K88ac or K88ad). A positive result of PCR is an amplificate of 792 bp in size for K88ab and K88ad variant or 786 bp for K88ac variant. The individual serological variants of genes of the K88 antigen could be differentiated by cutting the obtained PCR amplificates by restriction endonucleases. The PCR analysis of 674 E. coli strains isolated from diarrheic pigs showed that 184 strains were K88 positive. By using restriction endonucleases the K88-positive strains were in 4 cases classified as K88ab variant, 180 as K88ac variant and none contained gene for the K88ad variant. Ninety-five % coincidence with serological examination using K88ab, K88ac and K88ad specific antibodies was shown.

Aggregation of Lactobacilli and Bifidobacteria with Escherichia coli O157

A total of 5 Bifidobacterium spp. isolated from pig and children' feces and 6 Lactobacillus spp. from chicken feces were examined for expression of aggregation, cell surface hydrophobicity (CSH) and adherence to intestinal mucin. Co-aggregation activity was seen in 3 strains of auto-aggregative bifidobacteria and 4 auto-aggregative strains of Lactobacillus spp. with 2 enterohemorrhagic E. coli (O157). CSH correlated with Lactobacillus auto-aggregating activity and adherence to mucin but the correlation between Bifidobacterium adherence to mucin and CSH was not confirmed.

Proteolytic activity in Serratia marcescens clinical isolates

Exoproteinase production was demonstrated in 64 clinical isolates of S. marcescens. A significant relationship was found between the site of origin (autopsy material, hemocultures, various other sources), proteinase activity, and LD50 of the analyzed isolates. The number of exoproteinases varied during a 14-h incubation in batch cultures; the most frequently found was a 57.5-kDa proteinase which was observed in all analyzed strains. The exoproteinase production was shown to be related to strain virulence.

Enteroaggregative and cell-detachingEscherichia coli strains among polish children with and without diarrhea

To determine the association of enteroaggregative (EAEC) and cell-detaching (CDEC) Escherichia coli with diarrhea of unknown origin among children from Wrocław (Poland), E. coli strains isolated from stool specimens of children with diarrhea were examined for mannose-resistant adherence to HEp-2 cells. EAEC were isolated from 10 of 39 (26%) children examined with diarrhea and 4 of 20 (20%) age-matched controls. CDEC were present in 14 (36%) cases of diarrhea and 7 (35%) healthy subjects. Cell-detaching activity was distinctly associated with hemolysin production. Among hemolytic CDEC strains cytotoxic necrotizing factor 1 (CNF1) synthesis prevailed among isolates obtained from cases of diarrhea (57%) in comparison with isolates obtained from healthy controls (14.3%). Although neither EAEC nor CDEC E. coli strains were associated with diarrhea of children in this setting, there were differences among EAEC and CDEC strains isolated from children with and without diarrhea.

Occurrence of extended-spectrum beta-lactamases among Escherichia coli isolates from hospitalized and healthy children

The prevalence of extended-spectrum beta-lactamases (ESBL) was determined among isolates of Escherichia coli (n = 63) isolated from hospitalized (43) and healthy (20) children. Ten isolates (21%) were ESBL-positive for two screening tests, the double disk-synergy test and the Oxoid Combination Disk method. One ESBL-positive isolate came from a healthy child. The transfer frequency of oxyimino-beta-lactam resistance from ESBL-producing isolates to E. coli K12 C600 recipient strain ranged from 10(-8) to 10(-5) per donor cell. Donor strains and transconjugants displayed susceptibility patterns typical of ESBL producers. They were resistant to oxyimino-beta-lactams but susceptible to clavulanic acid and carbapenems. Seven out of the 10 ESBL-positive isolates were found to produce MR/MS fimbria, which may play an important role in the colonization of the human intestinal mucosa.

Detection of Shiga toxins, intimin and enterohemolysin in Escherichia coli strains isolated from children in eastern Slovakia

Fifty Escherichia coli strains isolated from stool samples of 51 healthy children, 143 strains isolated from stool samples of 327 children with diarrhea and 24 strains isolated from stool samples of 21 children with suspected hemolytic uremic syndrome were examined for the presence of Shiga toxin-producing E. coli virulence factors (shiga toxin 1 and 2, intimin and enterohemolysin) and their genes. Vero-cell assay and latex agglutination were used for detection of Shiga toxin 1 and 2, TSB agar with washed erythrocytes was used for detection of enterohemolysin; genes encoding shiga toxin 1 and 2, intimin and enterohemolysin were detected using multiplex PCR. The presence of E. coli strains harboring genes encoding shiga toxin 1 and 2 (12 strains), intimin (34 strains) and enterohemolysin (12 strains) was demonstrated.

Detection of pap-, sfa- and afa-specific DNA sequences in Escherichia coli strains isolated from extraintestinal material

P-fimbriae, S-fimbriae and AFA-adhesins are virulence factors responsible for adherence of Escherichia coli strains to extraintestinal host-cell surface. Detection of pap-, sfa- and afa-specific sequences performed by PCR revealed 74% pap+, 65% sfa+, and 8.3% afa+ strains in a group of 84 extraintestinal E. coli isolates. Detection in a group of fecal strains showed 29% pap+, 21% sfa+ and 4% afa+ strains. pap together with sfa were found as the most frequent combination (56%) among extraintestinal isolates probably due to localization of pap- and sfa-operons on a common pathogenicity island. The occurrence of afa-specific sequence among 56 urine strains was 11%, although no afa+ strain was detected among 28 gynecological isolates. No strains with detected adhesin operons were found among twenty (24%) extraintestinal E. coli strains.