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

Large variation in ESBL-producing Escherichia coli carriers in six European countries including Russia

We investigated the faecal carriage prevalence of extended-spectrum β-lactamase production in Escherichia coli (EP-EC) and/or Klebsiella pneumoniae (EP-KP) and risk factors associated with carriage among adult study subjects in Finland, Germany, Latvia, Poland, Russia and Sweden (partner countries). The aim was to get indicative data on the prevalence of ESBL-carriage in specific populations in the region. Faecal samples were collected from four study populations and screened on ChromID-ESBL and ChromID-OXA-48 plates. Positive isolates were further characterised phenotypically. Our results show a large variation in carrier prevalence ranging from 1.6% in Latvia to 23.2% in Russia for EP-EC. For the other partner countries, the prevalence of EP-EC were in increasing numbers, 2.3% for Germany, 4.7% for Finland, 6.6% for Sweden, 8.0% for Poland and 8.1% for all partner countries in total. Carriers of EP-KP were identified only in Finland, Russia and Sweden, and the prevalence was < 2% in each of these countries. No carriers of carbapenemase-producing isolates were identified. This is the first study reporting prevalence of carriers (excluding traveller studies) for Finland, Latvia, Poland and Russia. It contributes with important information regarding the prevalence of EP-EC and EP-KP carriage in regions where studies on carriers are limited.

Trends in human fecal carriage of extended-spectrum β-lactamases in the community: toward the globalization of CTX-M

In the last 10 years, extended-spectrum β-lactamase-producing enterobacteria (ESBL-E) have become one of the main challenges for antibiotic treatment of enterobacterial infections, largely because of the current CTX-M enzyme pandemic. However, most studies have focused on hospitalized patients, though today it appears that the community is strongly affected as well. We therefore decided to devote our investigation to trends in ESBL-E fecal carriage rates and comprehensively reviewed data from studies conducted on healthy populations in various parts of the world. We show that (i) community ESBL-E fecal carriage, which was unknown before the turn of the millennium, has since increased significantly everywhere, with developing countries being the most affected; (ii) intercontinental travel may have emphasized and globalized the issue; and (iii) CTX-M enzymes, especially CTX-M-15, are the dominant type of ESBL. Altogether, these results suggest that CTX-M carriage is evolving toward a global pandemic but is still insufficiently described. Only a better knowledge of its dynamics and biology will lead to further development of appropriate control measures.

Occurrence of endemic plasmids causing β-lactam resistance inEnterobacteriaceae in children’s university hospital in Munich

Susceptibility of 62 clinical isolates of Enterobacteriaceae to 15 aminoglycosides, beta-lactams and fluoroquinolones was determined. The isolates originating from 3 intensive care units (neonatal, pediatric, and surgical) and the Department of Infant Internal Medicine of the Children's University Hospital City Center in Munich (Germany) were collected in August 1999, and March and October 2000. Transferability of antibiotic resistance from donors to their E. coli transconjugants was also demonstrated. The majority of isolates were resistant to ampicillin, cefoxitin, ceftriaxone, cefotaxime, ceftazidime and azthreonam but they were susceptible to cefepime, meropenem, aminoglycosides and fluoroquinolones. The occurrence of beta-lactamases and extended-spectrum beta-lactamases (ESBL) was also shown. In August 1999 75% of isolates produced beta-lactamases and 15% ESBL, in March 2000 95% of isolates produced beta-lactamases and 9% ESBL; in October 2000 all isolates produced beta-lactamases and only 5% produced ESBL. Plasmid DNA analysis in randomly chosen isolates and their transconjugants revealed the presence of plasmids ranging from 19 to 136 kb; in the majority of isolates a 120-kb plasmid was observed. Further analysis using restriction endonuclease suggested a dissemination and persistence of an endemic plasmid at all 4 wards of the large pediatric hospital in the City Center of Munich which may be responsible for resistance to beta-lactams among Enterobacteriaceae isolates.

Extended-spectrum β-lactamase-conferring transferable resistance to different antimicrobial agents inEnterobacteriaceae isolated from bloodstream infections

Twenty (18.5%) out of 108 clinical isolates of the family Enterobacteriaceae responsible for bloodstream infection were extended-spectrum beta-lactamase (ESBL)-positive in two screening tests, the double disk synergy test and the Oxoid Combination Disk method. Eleven out of the 20 ESBL-positive isolates transferred oxyimino-beta-lactam resistance to E. coli K12 C600 recipient strain with a frequency of 10(-8) - 10(-1) per donor cell. PCR analysis revealed that the majority of the transconjugants (9 of 11) express CTX-M-type beta-lactamases. Donor strains and their transconjugants displayed susceptibility patterns typical of ESBL producers. They were resistant to oxyimino-beta-lactams but susceptible to clavulanic acid and carbapenems. Resistances to aminoglycosides, tetracycline and mercuric chloride were, in some cases, co-transferred with oxyimino-beta-lactam resistance, suggesting that various resistance determinants were carried by the same conjugative plasmids.

Curli expression of enterotoxigenicEscherichia coli

One hundred and four enterotoxin producing Escherichia coli strains of wide geographical origin were tested for the expression of curli fimbriae by transmission electronmicroscopy and by ELISA using curli-specific antibodies, as well as for the presence of curli-specific gene sequences by PCR. All isolates, irrespective of the production of the fimbriae, carried sequences specific for the structure (csgA) and for one of the regulator genes (crl) of curli expression, respectively. Curli fimbriae were detected in 56 strains (53.8 %). Thirty-six strains expressed curli only when growing at 30 degrees C, 4 isolates were weakly curliated at 37 degrees C only, while on 16 strains curli was observed at both temperatures. On isolates carrying curli at both temperatures the expression of the fimbria was significantly stronger at 30 degrees C than at 37 degrees C. Curli proficiency significantly, but not completely, correlated with the binding of the Congo Red dye. The expression of curli did not confer epithelial cell invasiveness to ETEC strains but, once expressed at 30 degrees C, it facilitated the adherence of the bacteria to plastic surfaces. Curli present in more than half of the ETEC strains and expressed preferentially at low temperatures could be a factor facilitating the environmental survival of this food- and water-borne pathogen.

Detection of cefotaxime-resistant CTX-M-3 in clinical isolates of Serratia marcescens

Strains of Serratia marcescens (isolated in a hospital during April and August 2000) resistant to ampicillin, chloramphenicol, trimethoprim-sulfamethoxazole, streptomycin, tetracycline, and gentamicin were characterized. Out of a total of 34 clinical isolates 6 (17.6 %) exhibited the extended spectrum beta-lactamases (ESBL) resistance; they were also resistant to cefotaxime (minimum inhibitory concentration, MIC > or = 128 microg/mL) but susceptible to imipenem (MIC < or = 0.5 microg/mL). This multidrug resistance was shown to be transferred by a conjugative plasmid. Transconjugants revealed similar MIC profiles when compared to the parental strains. Isoelectric focusing revealed one major transferable beta-lactamase (pI 8.4) which was further identified as CTX-M-3 by PCR and gene sequencing. The presence of strains with this type of ESBL showed the evolution of bla genes and their dissemination among at least three species of the family Enterobacteriaceae isolated within a single hospital. The predominance of CTX-M type enzymes found in this area of Taiwan appeared to be similar to that described in Poland.

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.