Prevalence of ColE1-Like Plasmids and Colicin K Production among Uropathogenic Escherichia coli Strains and Quantification of Inhibitory Activity of Colicin K

Abstract

Colicin K exhibited pronounced inhibitory activity against uropathogenic Escherichia coli (UPEC) strains. Low prevalence of colicin K production and a relatively high prevalence of ColE1-like plasmids were determined among 215 UPEC strains from Slovenia. Sequencing of the colicin K-encoding pColK-K235 revealed a mosaic structure and the presence of the insertion sequence IS2.An increasing health problem is the appearance and spread of antimicrobial resistance. Due to the global concern about antibiotic resistance, novel approaches, one being the use of bacteriocins, are being considered (10, 11). Colicins, bacteriocins produced by and active against Escherichia coli strains, are receiving renewed attention as an alternative means of preventing various E. coli-associated infections, for example, diarrhea, including serotype O157:H7 (15,22,28,29,30), and postweaning diarrhea and edema disease in swine (33). Colicins were recently shown to prevent colonization of urinary catheters (34). To date, no quantitative analysis of the inhibitory activity of colicins against uropathogenic E. coli (UPEC) has been performed.Colicin K is a pore-forming colicin encoded on small ColE1-like plasmids (23). A cluster of three genes codes for the production and release of colicin: cka for colicin activity, cki for immunity, and ckl for lysis (23). The synthesis of colicin K is induced primarily by an increase in the alarmone ppGpp due to nutrient depletion (18,19). Previous investigations found that approximately 30 to 50% of natural E. coli isolates produce colicins (27). Such a high prevalence of colicin production is in itself indicative of an ecological significance. Additionally, a recent study provided evidence that colicins E1 and E2 have an in vivo antagonistic role in promoting microbial diversity within E. coli populations in the mammalian colon (17).In this study, we investigated the inhibitory activity of purified colicin K against 215 UPEC strains from Slovenia as well as the prevalence of colicin K production and ColE1-like plasmids among the studied strains. The nucleotide sequence of plasmid pColK-K235 encoding the investigated colicin K was determined and analyzed.To gain insight into the ecological role of colicin K and to assess its antimicrobial efficacy, we initially determined the MIC of purified colicin K against 215 UPEC strains isolated from humans with urinary tract infections in 2001 and 2002 at the Institute of Microbiology and Immunology, Ljubljana, Slovenia (26). Isolation of the strains was performed according to standard laboratory protocols, and UPEC isolates were from a bacterial urine monoculture of Ͼ10 5 CFU per ml. To elicit infections, extraintestinal pathogenic E. coli strains, including UPEC, possess virulence factors. Therefore, the investigated UPEC strains were PCR screened for virulence factor sequences as described previously (14, 20). As antimicrobial resistance is an increasing health problem, testing of susceptibility to antimicrobial agents was performed as described previously (26).T...

Diversity and distribution of nuclease bacteriocins in bacterial genomes revealed using Hidden Markov Models

“…Using the Plasmid finder database and the Carattoli typing scheme [ 45 ] we could identify plasmid replicons within NB containing contigs. Addition of a conserved region identified for pColE1 replicons [ 46 ] allowed the typing of additional plasmids including large tRNase containing plasmids in E . coli ( S5a Fig ).…”

Plasmid Diversity and Adaptation Analyzed by Massive Sequencing of Escherichia coli Plasmids

“…Less epidemiological attention is normally paid to small mobilizable plasmids. However, they are also carriers of antibiotic resistance genes (110)(111)(112)(113), as well as competition weapons, such as bacteriocins (113)(114)(115)(116) and restriction-modification enzymes (117)(118)(119)(120). They rely on conjugative plasmids as helpers for their conjugative transmission.…”

Accumulation of single-stranded DNA in Escherichia coli carrying the colicin plasmid pColE3-CA38

“…Petkovšek et al (2012) correlated colicin insensitivity with pathogenicity, where resistance appeared to contribute to overcoming competitive exclusion at extraintestinal locations such as the skin. Based upon the elevated incidence of their occurrence in pathogenic strains, Rijavec et al (2007) and Šmajs et al (2010) correlated bacteriocins with the virulence potential in uropathogenic E. coli . In these two cases, colicins apparently act as colonization factors by helping to eliminate preexisting microbes that might otherwise prevent colonization.…”