**3. Microbiologic diagnosis of CAUTI**

80% is due to CAUTI [2]. CAUTI causes about 20% of episodes of health-care acquired bacteraemia in intensive care facilities and over 50% in long term care facilities [3]. The microbiology of biofilm on an indwelling catheter is dynamic with continuing turnover of organisms in the biofilm. Patients continue to acquire new organisms at a rate of about 3–7%/day. In long term catheterization that is by the end of 30 days CAUTI develops in 100% patients usually with 2 or more symptoms or clinical sign of haematuria, fever, suprapubic or loin pain, visible biofilm in character or catheter tube and acute confusion all state [4]. In CAUTI the incidence of infection is *Escherichia coli* in 24%, Candida in 24%, Enterococcus in 14% Pseudomonas in 10%, Klebsiella in 10% and remaining part with other organisms [5]. Bacteraemia occurs in 2–4% of CAUTI patients where case fatality is three times higher than nonbacteremic patients [6]. Adhesions in bacteria initiate attachment by recognizing host cell receptors on surfaces of host cell or catheter. Adhesins initiate adherence by overcoming the electrostatic repulsion observed between bacterial cell membranes and surfaces to allow intimate interactions to occur [7]. A biofilm is an aggregate of micro-organisms in which cells adhere to each other on a surface embedded within a self-produced matrix of extracellular polymeric substance [8]. In biofilm microorganisms growing in colonies within an extra-cellular mucopolysaccharide substance which they produce. Tamm-Horsfall protein and magnesium and calcium ions are incorporated into this material. Immediately after catheter insertion, biofilm starts to form and organisms adhere to a conditioning film of host proteins along the catheter surface. Both the inner and outer surfaces of catheter are involved. In CAUTI biofilms are initially formed by one organism but in prolonged Catheterization multiple bacteria's are present. In biofilm main mass is formed by extra cellular polymeric substance (EPS) within which organisms live. So there are three layers in biofilm, where deeper layer is abiotic, than environmental zone and on surface biotic zone [9]. Growth of bacteria in biofilms on the inner surface of catheters promotes encrustation and may protect bacteria from antimicrobial agents and the consequence is more drug resistance of biofilm organisms. When antibiotic treatment ends the biofilm can again shed bacteria, resulting recurrent acute infection. The patients may present as asymptomatic bacteriuria or symptomatic. In symptomatic bacteriuria patient present with fever, suprapubic or costovertebral angle tenderness, and systemic symptoms such as altered mentation, hypotension, or evidence of a systemic inflammatory response syndrome. In asymptomatic CAUTI diagnosis is made with presence of 10<sup>5</sup> cfu/mL of one bacterial species in a single catheter urine specimen [10]. In

24 Microbiology of Urinary Tract Infections - Microbial Agents and Predisposing Factors

symptomatic CAUTI bacteriological criteria is present with clinical symptoms.

be cultured from the catheter, for this swab is taken from inner side of catheter.

It is recommended that urine specimens be obtained through the catheter port using aseptic technique or, if a port is not present, puncturing the catheter tubing with a needle and syringe in patients with short term catheterization [11]. In long term indwelling catheterization, the ideal method of obtaining urine for culture is to replace the catheter and collect the specimen from the freshly placed catheter. In a symptomatic patient, this should be done immediately prior to initiating antimicrobial therapy. Culture specimens from the urine beg should not be obtained [10, 12]. Urine sample can be collected from suprapubic puncture also. Biofilm can

**2. The collection of specimens**

Catheter Associated Asymptomatic Bacteriuria (CA-ASB) is diagnosed when one or more organisms are present at quantitative counts ≥105 cfu/mL from an appropriately collected urine specimen in a patient with no symptoms [13]. Lower quantitative counts may be isolated from urine specimens prior to ≥105 cfu/mL being present, but these lower counts likely reflect the presence of organisms in biofilm forming along the catheter, rather than bladder bacteriuria [14]. Thus, it is recommended that the catheter be removed and a new catheter inserted, with specimen collection from the freshly placed catheter, before antimicrobial therapy is initiated for symptomatic infection [13]. In biofilm culture, most biofilm contains mixed bacterial communities meaning polymicrobial colonization.

Patients who remain catheterized without having antimicrobial therapy and who have colony counts ≥10 <sup>2</sup> cfu/mL (or even lower colony counts), the level of bacteriuria or candiduria uniformly increases to >10<sup>5</sup> cfu/mL within 24–48 h [14]. Given that colony counts in bladder urine as low as 102 cfu/mL are associated with symptomatic UTI in non-catheterized patients [15], untreated catheterized patients and those who have colony counts ≥10<sup>2</sup> cfu/mL or even lower, the level of bacteriuria or candiduria uniformly increases to >10<sup>5</sup> cfu/mL within 24–48 h [10, 16]. Colony counts as low as 102 cfu/mL in bladder urine may be associated with symptomatic UTI in non-catheterized patients. Whereas low colony counts in catheter urine specimens are likely to be contaminated by periurethral flora, and the colony counts will increase rapidly if untreated. Low colony counts in catheter urine specimens are also reflective of significant bacteriuria in patients with intermittent catheterization [14].
