Ten-year survey of quinolone resistance inEscherichia coli causing urinary tract infections

In a ten-year survey (1983–1992) of quinolone resistance inEscherichia coli causing urinary tract infections in a general practice patient population, 9,934 strains were tested. Resistance increased remarkably from 1989 onwards. The rate of resistance to pipemidic acid was 6 % before 1989 and 18 % in 1992; the rate of resistance to ciprofloxacin (MIC4mg/l) was 0.8 % in 1989 and 7.1 % in 1992. Although the consumption of older quinolones decreased the total consumption of quinolones increased yearly.     

Association between Escherichia coli with NotI-restriction resistance and urinary tract infections

BackgroundEscherichia coli is the most common cause of urinary tract infections (UTIs). It is widely accepted that uropathogenic E. coli (UPEC) mainly emerge from the distal gut microbiota. Identification of bacterial characteristics that are able to differentiate UPEC from fecal commensal strains will facilitate the development of novel strategies to detect and monitor the spread of UPEC.MethodsFifty fecal commensal, 83 UTI-associated and 40 biliary tract infection (BTI)-associated E. coli isolates were analyzed. The NotI restriction patterns of chromosomal DNA in the isolates were determined by pulse-field gel electrophoresis. The phylogenetic types and the presence of 9 known virulence genes of each isolate were determined by PCR analyses. Additionally, the susceptibilities of the isolates to antibiotics were revealed. Then the associations of NotI resistance with UTI-associated isolates, phylotypes, and antibiotic resistance were assessed.ResultsNotI resistance was correlated with UTI-associated isolates, compared to the fecal isolates. Consistently, NotI-resistant isolates harbored a greater number of virulence factors and mainly belonged to phylotype B2. Additionally NotI resistance was correlated with chloramphenicol resistance among the bacteria. Among the fecal, UTI-associated and BTI-associated groups, the distribution of NotI-resistant group B2 isolates was correlated with UTI-associated bacteria.ConclusionNotI resistance alone is a potential marker for distinguishing fecal strains and UPEC, while the combination of NotI resistance and B2 phylogeny is a candidate marker to differentiate UPEC from fecal and other extraintestinal pathogenic E. coli. Additionally, NotI resistance may be valuable for assessing the potential of chloramphenicol resistance of E. coli.     

Escherichia coli biofilm formation and recurrences of urinary tract infections in children

It has been suggested that biofilm formation by uropathogenic Escherichia coli (UPEC) isolates is associated with recurrence and persistence of urinary tract infection (UTI). We compared the in vitro biofilm formation of UPEC isolates from children with acute or recurrent UTI. Employing 206 consecutive clinical UPEC isolates from children with proven UTI, i.e., pyelonephritis (n?=?78), recurrent pyelonephritis (n?=?10), cystitis (n?=?84) or recurrent cystitis (n?=?34), we applied 1 % crystal violet staining to polystyrene microtitre plates at 72 h and measured the optical density (OD) values. The method had been validated to measure biofilm formation against confocal laser scanning microscopy and scanning electron microscopy. The OD values were lower in the recurrent cystitis group than in the other groups (mean OD 0.36, SD 0.21 vs mean 0.47, SD 0.36, P?=?0.04) and higher in the recurrent pyelonephritis group than in the other groups (mean OD 0.69, SD 0.33 vs mean OD 0.44, SD 0.34, P?=?0.006) indicating biofilm formation of strains causing recurrent pyelonephritis. It appears that the properties of UPEC isolates required for effective biofilm growth on an abiotic surface are important for recurrent pyelonephritis, but not for recurrent cystitis. It would be valuable in the future to analyze whether the biofilm properties of E. coli observed in vitro predict a slower clinical response to antimicrobial treatment and increased renal scar formation after UTI.     

Prevalence and pathogenesis of extended-spectrum beta-lactamase producing Escherichia coli causing urinary tract infection in hospitalized patients

A total of 296 E. coli strains isolated from hospitalized patients with urinary tract infection were included in this study. These strains were tested for their resistance to 22 antimicrobial drugs and the presence of ESBLs genes coding for TEM, SHV, OXA, and CTX-M. We further characterized them for their interaction with a renal cell line (A-498) and a gastrointestinal cell line (Caco-2). Strains were also typed using a combination of RAPD-PCR, PhP-typing and phylogenetic grouping. Only eight strains (2.7?%) were confirmed as ESBLs producers. The most common clonal type contained 35 isolates and only two of them were ESBLs producers and both showed a high degree of adhesion to both cell lines but only one was able to translocate in Caco-2 cells. These strains belonged to phylogenetic group B2, were resistant to nine antibiotics and carried CTX-M-type of ESBL. The remaining six strains belonged to single clones with different phylogenetic groups and ESBL genotypes and were resistant to between 12 and 15 antibiotics. They also showed a high rate of adhesion to A-498 cells (19?±?2 to 35?±?3?CFU/cell) and all translocated in this cell line. The rate of adhesion of ESBL-producing strains to Caco-2 cells (11?±?3.4?CFU/cell) was significantly lower than A-498 cells (26?±?8?CFU/cell) (p?=?0.0002) and only four of them translocated in Caco-2 cells. Our results suggest that the ESBL-producing clones of E. coli have a potential to translocate and cause septicemia in hospitalized patients with UTI.     

Adhesion, hemagglutination, and virulence of Escherichia coli causing urinary tract infections.

The capacity of 453 Escherichia coli strains to agglutinate erythrocytes and yeast cells and to attach to human urinary tract epithelial cells was tested. The strains were isolated from the urine of patients with acute pyelonephritis, acute cystitis, or asymptomatic bacteriuria and from the stools of healthy school children. Three main patterns of hemagglutination were found: (i) mannose-resistant agglutination of human erythrocytes alone or simultaneously with mannose-sensitive agglutination of guinea pig erythrocytes; (ii) only mannose-sensitive agglutination of guinea pig and other erythrocytes; and (iii) no agglutination. Strains with mannose-resistant agglutination of human erythrocytes alone or in combination with mannose-sensitive hemagglutination attached in high numbers to human urinary tract epithelial cells. Bacteria inducing only mannose-sensitive hemagglutination attached in low numbers, and non-agglutinating strains did not bind to the urinary tract epithelial cells. The bacterial surface antigen(s) mediating mannose-resistant hemagglutination of human erythrocytes and attachment to human urinary tract epithelial cells may be one factor selecting for E. coli from among the fecal flora which infect the urinary tract. The highest proportion of strains with this property was found among acute pyelonephritis isolates (77%), and the lowest proportion of strains with this property was found among normal fecal E. coli (16%).     

Imipenem resistance in nonfermenters causing nosocomial urinary tract infections

Nonfermenting gram-negative bacilli (nonfermenters) have emerged as important nosocomial pathogens causing opportunistic infections in immunocompromised hosts. These organisms show high level of resistance to b-lactam agents, fluoroquinolones and aminoglycosides. Imipenem is a carbapenem antibiotic, which can be very useful for treatment of infections caused by nonfermenters. Eighty-five nonfermenters causing nosocomial UTI were tested for MIC to imipenem by agar dilution method. Resistance to other antimicrobial agents was compared between imipenem sensitive (S) and resistance (R) groups. Overall 36.4% of nonfermenters were resistant to imipenem. Forty two percent of P. aeruginosa and 18.5% of Acinetobacter baumanii were imipenem resistant. Other nonfermenters showed variable resistance, resistance in Alcaligenes spp. being very high. More than 70% of the nonfermenters were resistant to ceftazidime, gentamicin and ciprofloxacin. Piperacillin and amikacin had the best in vitro susceptibility. No significant difference was found in the antibiotic susceptibility profile among imipenem sensitive (S) or resistant (R) strains.     

Integrons and multidrug resistance among Escherichia coli causing community-acquired urinary tract infection in southern India

Antimicrobial resistance genes are often clustered in integrons, genetic elements capable of recombination. There is a paucity of data on the prevalence and role of integrons from community-acquired infections in developing countries where resistance to co-trimoxazole is high. We determined the prevalence of integrons among Escherichia coli causing community-acquired urinary tract infection (UTI). Consecutive isolates of E. coli obtained from UTI of pregnant women at the Christian Medical College Hospital, Vellore, India, during 2002 were included. All isolates were tested for susceptibility to 16 antimicrobials using the disc diffusion method and for integrons of classes 1 and 2 by PCR. Of the 58 isolates tested, 28 (48.3%) were resistant to co-trimoxazole and trimethoprim. All these isolates carried integrons. Three additional isolates were sulfonamide resistant but integron negative. Class 1 integrons were present in 21 (36.2%) isolates. Resistance to ampicillin (p=0.000), nalidixic acid (p=0.001), chloramphenicol (p=0.02), tetracycline (p=0.004) and gentamicin (p=0.02) was significantly more common in isolates with integrons. DNA sequencing of two isolates with integrons showed the presence of aadA, dfr1 and dfr7 genes. This study demonstrated that integrons are widely prevalent in India and that they might play a role in multidrug resistance in E. coli from community-acquired UTI.     

Alpha-hemolytic strains of Escherichia coli isolated in urinary tract infections in small children]

The authors focused attention on testing of biological properties of alpha-haemolytic strains of E. coli in infections of the urinary pathways in children and on the antibody response against alpha-haemolysin. The strains belonged into serogroups 02, 04, 06, 018, 075, 0112. The majority of strains had fimrial adhesins, i.e. P fimbriae, or fimbriae type 1. Alpha-haemolysin one of the factors of UPEC virulence induces anti-alphahaemolysin formation in serum (ANTI AH). Titres of ANTI AH in sera of children with acute uroinfection were from 1:32 to 1:1024. Lower titres were recorded in infections of the lower urinary pathways higher ones in renal infections, whereby the dynamics of ANTI AH titres depend on the development of the disease.     

Escherichia coli clonal group A causing bacteraemia of urinary tract origin

Escherichia coli clonal group A (CgA) causes disease in humans. This is the first study investigating the prevalence of CgA among E. coli from non-urine, extraintestinal infections in a northern European country. E. coli blood (n = 196) and paired urine (n = 195) isolates from the same patients with bacteraemia of urinary tract origin were analysed. The isolates were collected from January 2003 through May 2005 at four hospitals in Copenhagen, Denmark. Pulsed-field gel electrophoresis (PFGE) patterns, antimicrobial resistance and patient characteristics were determined for all CgA isolates; presence of virulence-associated genes (VAGs) and serotypes were determined for the blood CgA isolates. Thirty blood isolates (15%) belonged to CgA. CgA blood isolates were associated with female patients and sulfamethoxazole-trimethoprim resistance and they harboured a distinctive VAG profile. The blood and urine isolates from each pair were found to be related in 26 of 27 CgA blood/urine pairs, confirming a urinary tract origin of infection. Furthermore, a relationship between the PFGE patterns of CgA blood/urine isolates and CgA isolates from UTI patients in general practice and a CgA isolate from a community-dwelling human reported previously, was found, suggesting a community origin of CgA. The finding of CgA strains in 15% of the E. coli bloodstream infections with a urinary tract origin in Denmark suggests that CgA constitutes an important clonal lineage among extraintestinal pathogenic E. coli. A reservoir of this pathogenic E. coli group in the community causing not only UTI but also more severe infections such as bacteraemia has implications for public health.     

Aerobactin production of serotyped Escherichia coli from urinary tract infections

Aerobactin production was examined by a bioassay in 467 Escherichia coli urinary strains from girls. All strains were of known OKH serotype. 139, 119 and 112 strains were isolates from pyelonephritis (Py), cystitis (Cy) and asymptomatic bacteriuria (ABU), respectively, and 97 were from fecal samples of healthy girls (FN). The incidence of aerobactin production was significantly higher among Py strains than among ABU and FN strains (P<0.001) and also significantly higher than among Cy strains (P<0.01). Aerobactin production was associated with serotype, e.g. the majority of 06K2H1 strains and of 016K1H6 were positive while e.g. the 06K13H1 strains were negative. There was no consistent pattern of coappearance of aerobactin and hemolysin.     

Aerobactin production of serotyped Escherichia coli from urinary tract infections

Aerobactin production was examined by a bioassay in 467 Escherichia coli urinary strains from girls. All strains were of known O:K:H serotype. 139, 119 and 112 strains were isolates from pyelonephritis (Py), cystitis (Cy) and asymptomatic bacteriuria (ABU), respectively, and 97 were from fecal samples of healthy girls (FN). The incidence of aerobactin production was significantly higher among Py strains than among ABU and FN strains (P less than 0.001) and also significantly higher than among Cy strains (P less than 0.01). Aerobactin production was associated with serotype, e.g. the majority of O6:K2:H1 strains and of O16:K1:H6 were positive while e.g. the O6:K13:H1 strains were negative. There was no consistent pattern of coappearance of aerobactin and hemolysin.     

Identification of Escherichia coli genes associated with urinary tract infections

Escherichia coli is the most common cause of urinary tract infections (UTIs). E. coli genes epidemiologically associated with UTIs are potentially valuable in developing strategies for treating and/or preventing such infections as well as differentiating uropathogenic E. coli from nonuropathogenic E. coli. To identify E. coli genes associated with UTIs in humans, we combined microarray-based and PCR-based analyses to investigate different E. coli source groups derived from feces of healthy humans and from patients with cystitis, pyelonephritis, or urosepsis. The cjrABC-senB gene cluster, sivH, sisA, sisB, eco274, and fbpB, were identified to be associated with UTIs. Of these, cjrABC-senB, sisA, sisB, and fbpB are known to be involved in urovirulence in the mouse model of ascending UTI. Our results provide evidence to support their roles as urovirulence factors in human UTIs. In addition, the newly identified UTI-associated genes were mainly found in members of phylogenetic groups B2 and/or D.     

Antimicrobial resistance pattern of Escherichia coli causing urinary tract infections,and that of human fecal flora,in the southeast of Iran

Sensitivity of 500 Escherichia coli isolates from urinary tract infections (UTIs, 311 isolate) and fecal samples (189 isolates) was tested against 12 antimicrobial agents using the standard disk diffusion method. Although the rate of resistance to antimicrobial agents was higher in the UTIs, in comparison with the fecal samples, the only significant difference was found in cases of tetracycline (p = 0.008), nalidixic acid (p = 0.038), and trimethoprim-sulfamethoxazole (Sxt,p = 0.05). The pattern of sensitivity to antimicrobial agents with respect to statistically significant difference in the number of sensitive isolates (p < or = 0.01) was: ceftizoxime (99.4%) and ceftriaxone (99.2%) > gentamicin (97.8%), ciprofloxacin (93%) and nitrofurantoin (92%) > cefazoline (85.2%) and nalidixic acid (84.6%) > chloramphenicol (71.6%), cephradine (69.6%) and tetracycline (63.2%) > Sxt (41.6%) > ampicillin (23.2%). Sensitivity of the isolates in respect to sex and age was also determined and compared during this study. Resistance to three or more antimicrobial agents (multidrug resistance, MDR) was found in 209 (41.8%) of the isolates. The high rate of resistance to Sxt and the presence of a high rate of MDR isolates in this area suggest that a reevaluation of the first-line therapeutic may be necessary for the treatment of UTIs in this area.     

Hemagglutination by Escherichia coli in septicemia and urinary tract infections.

The agglutination of erythrocytes from various animal species by Escherichia coli was studied. The 405 strains of E. coli were isolated from urine in patients with urinary tract infections, from blood in septicemic patients, or from feces in persons without intestinal or urinary disorders. In urinary tract infections, d-mannose-resistant agglutination (MRHA) of human erythrocytes was the most common finding (23% of the strains). The highest frequency of mannose-sensitive hemagglutination (MSHA) attributed to type I (common type) pili occurred with guinea pig erythrocytes (11.5%). Of the 78 E. coli strains isolated from blood cultures, 11 (14%) produced MRHA of human erythrocytes and only one gave MSHA. In the stool cultures, only 1 of 170 E. coli strains was MSHA reacting, whereas 28 strains (16.5%) showed MRHA of human erythrocytes. No MRHA strain reacted with antiserum against colonization factor antigen (CFA)/I of pilus nature in enterotoxigenic human E. coli strains (O78:H12). MRHA of bovine erythrocytes, reputedly typical of enterotoxigenic E. coli of serogroups O6 and O8, was shown by only two strains, neither of which agglutinated with CFA/II antiserum. The most common hemagglutinating pattern of E. coli from urine and blood thus was MRHA for human erythrocytes. This agglutination may have been caused by pili or other surface properties of one or more serotypes. These may represent a new class of colonization-promoting antigens (adhesins).