Academic journal article Iranian Journal of Public Health

Characterization of Staphylococcus Aureus Biofilm Formation in Urinary Tract Infection

Academic journal article Iranian Journal of Public Health

Characterization of Staphylococcus Aureus Biofilm Formation in Urinary Tract Infection

Article excerpt


Urinary tract infection (UTI) is one of the most common infectious diseases in humans both in the clinical and community settings. Its global incidence is estimated to be 250 million cases each year (1, 2). Escherichia coli is the most prevalent causative organism of UTI, accounting for about 80% of bacterial isolates (3, 4). However, involvement of Gram-positive bacteria cannot be ruled out in relation to UTI. Staphylococcus aureus is one of such agents involved in the infection that is capable of invading the urinary tract. Although S. aureus accounts to 0.5-6% of UTI, but if leave untreated infection can lead to severe lifethreatening condition (5, 6).

Emergence of multidrug-resistant (MDR) S. aureus has become an increasing health concern worldwide (7). Currently, it is estimated that biofilms are responsible for more than 65% of all nosocomial infections and 80% bacterial infections. Bacterial biofilms can play an important role in recurrent urinary tract infections and resistance to antimicrobial agents (8, 9). In addition, the proximity of cells within the biofilm structure can facilitate genetic elements exchange and hence enhance the possible spread of genes responsible for antibiotic resistance (10, 11). S. aureus is known to form biofilms on various surfaces. This pathogen, can invade renal tissue causing UTI by adherence to uroepithelium and formation of biofilm. Since the ability of biofilm production in S. aureus can increase resistance to commonly used antibiotics, hospitalized patients infected with this organism are at significant risk for treatment failure (12, 13).

S. aureus biofilm formation is regulated by expression of polysaccharide intracellular adhesion (PIA), which mediates cell to cell adhesion and is encoded by the icaADBC operon (14). Moreover, surface-associated proteinaceous adhesins can contribute to the adherence, colonization and biofilm formation of S. aureus. This pathogen can express a variety of microbial surface components recognizing adhesive matrix molecules (MSCRAMMs), such as fibronectin-binding proteins A (FnbA), clumping factors A (ClfA) and biofilm-associated protein (Bap) (15, 16). However, the mechanism of biofilm formation and pathogenicity of S. aureus infections in the urinary tract is controversial. Recently, the study of genes involved in biofilm formation and their role in infections caused by S. aureus have attracted great interest (12).

Given the role of biofilm related genes in biofilm formation and antibiotic resistance, the need for study is more than ever. Therefore, the aim of this study was to evaluate of biofilm formation and antimicrobial resistance in S. aureus isolated from urinary tract infection.

Material and Methods

Bacteria isolates

The study was conducted with a total of 39 isolates of S. aureus among UTI patients collected at Sina Hospital, Tehran University of Medical Sciences (TUMS). S. aureus isolates were confirmed using conventional microbiological methods (Gram's stain, catalase, coagulase, DNase tests, and mannitol fermentation on mannitol salt agar [Merck, Germany]). MRSA strains were identified phenotypically using cefoxitin disk diffusion method (30 μg; MAST, UK). This method was performed according to the Clinical and laboratory standards institute (CLSI) guidelines (17).

Antibiotic susceptibility determination

The antibiotic susceptibility patterns of S. aureus isolates were determined by the Kirby-Bauer disk-diffusion method, and the results were interpreted according to CLSI guidelines (17). The antimicrobial agents (MAST, UK) tested in this study included erythromycin (15 μg), tetracycline (30 μg), ciprofloxacin (5 μg), chloramphenicol (30 μg), rifampin (50 μg), nitrofurantoin (300 μg), linezolid (30 μg), quinupristin/dalfopristin (15 μg), clindamycin (2 μg), doxycycline (30 μg), trimethoprim-sulfamethoxazole (25 μg) and gentamicin (10 μg). S. aureus ATCC 25923 was used as a standard strain. …

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