ANTIMICROBIAL RESISTANCE AND BIOFILM FORMATION BY ESCHERICHIA COLI IN URINE
Background to the Study
Urinary tract infections (UTIs) are among the most common infections affecting humans today. The presence of bacteria in the urinary system results in serious infections that can cause kidney failure, and in some cases death Karkkainen, U. M., Kauppinen (1998). The first step in infection is the adhesion of bacteria to uroepithelium where bacterial cells can multiply and colonize different organs of the urinary system4. Conventional methods to treat UTIs rely on the use of antibiotics. However, many bacteria can develop antibiotic resistance Dyer, I. E., Sankary, (1994). The use of antibiotics to treat infections can also become a major environmental problem since the human body does not process these substances completely, and therefore they persist in wastewater.
Other therapeutic methods are currently being investigated for the prevention and treatment of UTIs, where the use of natural products has shown signs of becoming a promising alternative. For example, cranberries have been used as a remedy to prevent and treat UTIs for many years. Limited clinical evidence has suggested that cranberries can be used as a prophylactic treatment to prevent recurrent UTIs, since they may prevent bacteria from adhering to uroepithelium. Limited in vitro studies have been done to investigate the mechanisms responsible for this anti-adhesive activity Stothers, L. A (2002)
Escherichia coli is the most common infecting agent in the urinary tract, targeting most frequently neonates, preschool girls, sexually active women and elderly women1. While UTIs can be caused by other bacterial strains, including Pseudomonas aeruginosa, Klebsiella spp., Enterococcus spp., and Proteus mirabilis, Escherichia coli is identified as the etiologic agent in at least 75% of women who present symptoms of cystitis. E. coli also accounts for 90 to 100% of bacterial infection in the kidneys or acute pyelonephritis.
The first step in the development of a UTI is the adhesion of bacteria to uroepithelium4. In the case of E. coli, these bacteria have extracellular compounds that interact with the surface of uroepithelial cells1. These compounds, known as fimbriae, are protein structures that act as adhesins that bind to receptors of different cells. E. coli can express several types of fimbriae that bind to specific receptors. Acute pyelonephritis has been found to be caused by E. coli that have fimbriae of type P. This type of fimbriae binds to receptors in P blood antigens that are found on the surface of uroepithelial cells. The P blood antigen is present in over 99.9% of the world‟s population.
Urinary Tract Infections (UTI’s) pose a serious health threat with respect to antibiotic resistance and high recurrence rates. Generally there is an agreement among the authors in the literature that the predominant uropathogens acquired from any source are gram negative bacteria with Escherichia coli accounting for the highest prevalence in most instances (Moges et al., 2002). Community and hospital acquired UTI’s are among the frequently encountered infectious diseases (Sobel and Kaye, 2000). Chronic Kidney Disease which is the cause of morbidity and mortality worldwide is also highly prevalent among children, where the main cause is identified due to the poor healthcare system (Mortazavi and Rafiee, 2010). Uropathogenic E. coli form intracellular bacterial communities with biofilm like properties within the bladder epithelium (Anderson et al., 2004). A biofilm is a population of cells growing on a surface and enclosed within an exopolymer matrix that can restrict the diffusion of substances and bind antimicrobials. This will provide effective resistance for biofilm cells against large molecules such as antimicrobial proteins lysozyme and complement (Ishida et al., 1998). According to a recent public announcement from National Institutes of Health, “more than 60% of all microbial infections are caused by biofilms” (Lewis, 2001). The armament of therapeutic agents available to treat bacterial infections today is restricted to antibiotics developed specifically to kill or stop the growth of individual bacteria (Sritharan and Sritharan, 2004). Antibiotic resistance is the most problematic and costly characteristics of biofilm. Biofilm formation occurs when microorganism attach to a surface and through growth and continuing colonization, spread over the surface (McLean et al., 1999). Biofilms can vary in thickness to from a mono cell layer of 6 to 8 cm thick but mostly on an average of about 100 μm thickness (Kumar and Prasad, 2006). Antibiotic resistance of urinary tract pathogens has been known to increase worldwide, especially against commonly used antimicrobials (Kahlmeter, 2003). The antibiotic sensitivity patterns of either one or more of the organisms have been determined to one or more of the commonly used antimicrobial drugs in UTI cases (Gordon et al., 2003). Bacteria embedded within biofilms present a challenge to surface decontamination by conventional means (Salamitou et al., 2009). In modern clinical microbiology, establishment of bacterial biofilms is considered a pathogenicity trait during chronic infections (Sritharan and Sritharan, 2004). The difficulty in eradicating a chronic infection associated with biofilm formation lies in the fact that biofilm bacteria are able to resist higher antibiotic concentration than bacteria in suspension (Gristina et al., 1987). The intracellular biofilm like properties allows bacteria to outlast a strong immune response to establish a dormant reservoir of pathogens inside the bladder cells (Anderson et al., 2003).