**1. General information about CAUTI**

UTI affects approximately 150 million people worldwide, which is most common infection with female predominance [1]. Around 15–25% hospitalized patients receiving indwelling urinary catheter develops CAUTI with prolonged catheterization and in among 40% nosocomial UTI,

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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 symptomatic CAUTI bacteriological criteria is present with clinical symptoms.

**3. Microbiologic diagnosis of CAUTI**

lated from urine specimens prior to ≥105

24–48 h [10, 16]. Colony counts as low as 102

**5. Microorganisms causing CAUTI**

**4. Other laboratory tests**

**5.1. CAUTI with** *E. coli*

*5.1.1. Introduction*

colony counts ≥10 <sup>2</sup>

organisms are present at quantitative counts ≥105

mixed bacterial communities meaning polymicrobial colonization.

Catheter Associated Asymptomatic Bacteriuria (CA-ASB) is diagnosed when one or more

urine specimen in a patient with no symptoms [13]. Lower quantitative counts may be iso-

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

Patients who remain catheterized without having antimicrobial therapy and who have

duria 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

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 reflec-

Pyuria is usually present in CA-UTI, as well as in CA-ASB. The sensitivity of pyuria for detecting infections due to enterococci or yeasts appears to be lower than that for gram-negative bacilli. Dipstick testing for nitrites and leukocyte esterase was also shown to be unhelpful in

It is the most common cause of CAUTI in 24–60% patients [5, 18]. In CAUTI the source of this organism is usually patients own colonic flora. *E. coli* is large and diverse group of bacteria found in environment, foods and intestine of human and animal. Among many species of *E. coli* only a few causes disease in human being. It is beneficial in that it prevents the

patients [15], untreated catheterized patients and those who have colony counts ≥10<sup>2</sup>

or even lower, the level of bacteriuria or candiduria uniformly increases to >10<sup>5</sup>

tive of significant bacteriuria in patients with intermittent catheterization [14].

establishing a diagnosis in catheterized patients hospitalized in the ICU [17].

cfu/mL (or even lower colony counts), the level of bacteriuria or candi-

cfu/mL from an appropriately collected

Microbiology of Catheter Associated Urinary Tract Infection

http://dx.doi.org/10.5772/intechopen.80080

cfu/mL

25

cfu/mL within

cfu/mL being present, but these lower counts likely

cfu/mL in bladder urine may be associated with
