Extended Characterization of Human Uropathogenic Escherichia coli Isolates from Slovenia

Abstract

Escherichia coli (E. coli) is a very diverse bacterial species found naturally in the intestinal tract of humans and many other animal species. Even though E. coli is known to be part of the normal gut microbiota, some strains – that are pathogenic – cause a wide variety of different intestinal and extraintestinal diseases (Marrs et al., 2005). Typical extraintestinal infections due to E. coli include urinary tract infections (UTI), diverse intra-abdominal infections, pneumonia, surgical-site infection, meningitis, osteomyelitis, soft-tissue infections, bacteremia (Russo & Johnson, 2006). UTIs are one of the most frequently acquired bacterial infections and E. coli accounts for as many as 90% of all community-acquired UTIs. Approximately 50% of all women have had a UTI by their late 20s. About 20–30% of women with first UTI will have two or more infections; while 5%, will develop chronic recurring infections which greatly disrupt a woman’s life (Marrs et al., 2005). In Slovenia E. coli is the causative agent of approximately 80% of uncomplicated UTIs (Lindic, 2005). E. coli isolates that cause UTI exhibit a number of specific characteristics and are classified, as uropathogenic E. coli (UPEC), a subgroup of extraintestinal pathogenic E. coli (ExPEC) (Russo & Johnson, 2000). UPEC strains mainly belong to the B2 phylogenetic group and to a lesser extent to the D group, while commensal strains belong to groups A and B1 (Picard et al., 1999). Further, some O-antigens (O1, O2, O4, O6, O7, O18 and O83) are more prevalent among uropathogenic E. coli strains and are therefore associated with UTI (Moreno et al. 2006). In comparison to commensal E. coli strains, UPEC possess an array of virulence factors namely, adhesins, toxins, polysaccharide coatings, invasins, iron uptake systems and systems to evade host immune responses (Oelschlaeger et al., 2002). Of serious concern and an increasing health problem, on a global scale, is the appearance and spread of antimicrobial resistance. One of the major health care concerns is emergence of multidrug resistant bacteria and clinical microbiologists increasingly agree that multidrug resistant Gram-negative bacteria pose the greatest risk to public health (Kumarasamy et al., 2010). Therefore, it is essential to determine susceptibility of pathogenic strains for antimicrobial agents and association of antimicrobial resistance with virulence genes. One of the means for acquiring specific virulence factor genes and antimicrobial resistance genes, is via mobile DNA (e. g. conjugal plasmids, transposons/integrons) (Alekshun &