Colicin insensitivity correlates with a higher prevalence of extraintestinal virulence factors among Escherichia coli isolates from skin and soft-tissue infections

Abstract

Colicins are toxic proteins with a narrow killing spectrum that are produced by colicinogenic Escherichia coli strains. The aim of this study was to analyse systematically whether extraintestinal virulence potential is linked to colicin (in)sensitivity. In total, 102 well-characterized E. coli isolates from skin and soft-tissue infections (SSTIs) were exposed to 17 single-colicinproducing strains, and the correlation between insensitivity to colicin and phylogenetic group as well as the extra-intestinal virulence potential of the SSTI strains was examined. The results showed that SSTI strains belonging to the B2 phylogenetic group were statistically significantly associated with insensitivity to at least ten colicins, and several colicin insensitivities were correlated with virulence factors. As far as is known, this is the first study to report such correlations. INTRODUCTIONEscherichia coli is a diverse bacterial species found naturally in the intestinal tract of humans and many other animal species. However, some strains are pathogenic and cause a wide variety of different intestinal as well as extra-intestinal diseases (Marrs et al., 2005). Extra-intestinal pathogenic E. coli (ExPEC) isolates are a medically significant group of pathogens responsible for significant morbidity, mortality and cost to the healthcare system as a result of urinary tract infections (UTIs), diverse intra-abdominal infections, pneumonia, surgical-site infections, meningitis, osteomyelitis, skin and soft-tissue infections (SSTIs) and bacteraemia (Russo & Johnson, 2006). As the causative agent of~90 % of all UTIs among ambulatory female patients (Johnson & Stamm, 1989), it is not surprising that the UTI subgroup of ExPEC has been studied the most extensively. Among SSTIs, E. coli is the third most prevalent species isolated (Moet et al., 2007). Nevertheless, strains from these infections have not been characterized extensively. All ExPEC strains have a common phylogenetic background deriving typically from phylogenetic groups B2 and D, and share the same spectrum of virulence determinants (Russo & Johnson, 2000).Colicins are narrow-killing-spectrum bacteriocins produced by E. coli. Each colicin is unique in its characteristics (see Table 1 for some examples) and they do not share the same killing efficiencies (Feldgarden & Riley, 1998). Whilst it has been shown that colicins prevent the growth of intestinal and uropathogenic E. coli isolates Schamberger et al., 2004; Stahl et al., 2004), a high prevalence of insensitivities to colicins among microbial populations isolated from animals, humans and patients with UTIs has also been reported (Feldgarden & Riley, 1998;Rijavec, 2010;Riley & Gordon, 1992). To our knowledge, the correlation between colicin insensitivity and virulence potential has not yet been investigated. Therefore, the prevalence of colicin insensitivity among E. coli SSTI isolates with known virulence potential was determined systematically by exposing 102 strains to 17 different colicins. Furthermore, for the first time,...

Bacteriocin-encoding genes and ExPEC virulence determinants are associated in human fecal Escherichia coli strains

“…At the same time, several studies have shown an association between the production of some types of bacteriocins and pathogenic E. coli strains [20-23]. Previous studies have found that genes encoding colicin E1, as well as microcins H47, M, I47, E492 and V were associated with extraintestinal pathogenic E. coli strains [20-23].…”

“…Previous studies have found that genes encoding colicin E1, as well as microcins H47, M, I47, E492 and V were associated with extraintestinal pathogenic E. coli strains [20-23]. Colicin E1 is also known to have toxic effects on eukaryotic cells and is considered to be a virulence factor in UPEC strains [21,24,25].…”

The importance of the “V”-Factor:Escherichia colibacteremia and sepsis

“…Other groups have published similar findings, looking at the relationship of microcins and bacteriocin synthesis with VFs in human disease. [12][13][14] The blaTEM findings from the following article examined antibiotic resistance gene expression and found that in their population blaTEM was associated with increased risk of severe sepsis.…”

The therapeutic potential of bacteriocins as protein antibiotics

“…These antimicrobial peptides or proteins are diverse and widespread among Gram-positive and Gram-negative bacteria [11]. It is becoming evident that they are linked to pathogenesis as they play a role in displacing bacterial flora, enhancing colonization and therefore infection ( [11][12][13] and Sharp et al unpublished data). In fact, protein bacteriocin-encoding genes can be found in the genomes of most Gram-negative pathogens, including P. aeruginosa, E. coli and K. pneumoniae ( [14] and Sharp et al unpublished data).…”