Catheter Associated Urinary Tract Infection Offending Pathogens, Antimicrobial Sensitivity, and Complications : Nigerian Journal of Surgical Sciences

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Catheter Associated Urinary Tract Infection Offending Pathogens, Antimicrobial Sensitivity, and Complications

Odoemene, Charles Azuwike; Adiri, C. O.1

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Nigerian Journal of Surgical Sciences 29(1):p 6-13, Jan–Dec 2019. | DOI: 10.4103/njss.njss_6_20
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Catheter-associated urinary tract infection (CAUTI) is a source of morbidity in patients on indwelling urinary catheters. Patients in both outpatient and inpatient general wards can be on indwelling urinary catheters at one time or the other due to various underlying pathologies. These indwelling urinary catheters can attract microorganisms into the urinary tract causing CAUTI. The aim is to determine the offending pathogens, antimicrobial sensitivity, and complications in CAUTI.

Patients and Methods: 

This was a prospective interventional study involving catheterized patients without prior urinary tract infection. The catheters were inserted due to various underlying pathologies either on an outpatient basis or on admission in the general ward. On suspicion of infection by the presence of any of these, cloudy urine, pericatheter pain, suprapubic pain, fever, chills or hematuria, and urine samples were aseptically collected by the laboratory scientist for culture and sensitivity. Any significant bacteriuria either asymptomatic or symptomatic was documented, and the offending pathogens also identified. Antimicrobial sensitivity patterns were recorded, and any complications noted in the patients were recorded.


A total of 460 patients, 376 (81.7%) males and 84 (18.3%) females were recruited into the study. The prostatic disease was the most common pathology necessitating urinary catheterization, accounting for 59.5% of all the cases. There were 100% recorded cases of CAUTI in the study. Escherichia coli was the most common organism isolated 45.2%. There was asymptomatic bacteriuria in 81% of the patients, while in 19%, it was symptomatic. There was multidrug resistance to the commonly used antimicrobials.


CAUTI still poses enormous challenges to both the outpatients and general inpatients. To minimize CAUTI, indiscriminate use of urinary catheters should be discouraged and urinary catheters should be removed immediately; they serve the purpose for which they were inserted.


Catheter-associated urinary tract infection (CAUTI) is a well-recognized burden in terms of morbidity and mortality in patients on indwelling catheter devices. The urinary tract is a common site for infection and accounts for about 40% of nosocomial infections worldwide, and out of this CAUTI accounts for about 80%.[12] CAUTI occurs because urethral catheters inoculate organisms into the urinary bladder promoting colonization by producing a surface for bacterial adhesion, thereby causing mucosal irritation.[3] Most microorganisms causing CAUTI are derived from patients' own colonic and perineal flora and the hands of health care workers.[24] The risk factors for the development of CAUTI include the duration of catheterization, female gender, postpartum state, diabetes mellitus, renal insufficiency, low hemoglobin, and immune-compromised and debilitated states.[45] The entry of bacteria into the urinary bladder can occur during insertion of the catheter through the lumen of the catheter (intraluminal), reported to occur in 34% of cases or along the catheter urethral interface (extraluminal), reported to occur in 66% of cases.[6] CAUTI may be asymptomatic or symptomatic. When the latter is the case, complications such as catheter encrustations, epididymorchitis, prostatitis, cystitis, bladder stones, pyelonephritis, endocarditis, and meningitis may occur.[567] Furthermore, CAUTI leads to a prolonged hospital stay with its economic implications. The cost of treating the associated infections in the USA is between $340 and $450 million dollars annually.[56]

We report the findings of a prospective study of newly catheterized patients with various pathologies in a tertiary institution in South-Eastern Nigeria. The aims of the study are to determine the offending pathogens, antimicrobial sensitivity, and complications in CAUTI.


Approval for the study was obtained from the ethical committee of the hospital. Between June 2017 and June 2019, a total of 460 patients were recruited for the study. These patients were seen at the outpatient clinics of the hospital, while some were inpatients. These patients were recruited into the study by an individual direct approach and obtaining written informed consent from all of them. Before catheter insertion, urine samples were sent for culture and those found to have urinary tract infection (UTI) were excluded from the study. Those already on indwelling catheters at presentation were also excluded.

Demographic and clinical data such as age, sex, date of admission, and underlying pathology necessitating catheterization were recorded in a pro forma.

Diagnosis of CAUTI in these patients on indwelling urinary catheters was made if they had A, B, and C below:

  1. An indwelling urinary catheter for >2 days, day 1 being the day of catheter insertion
  2. One sign or symptom including fever, suprapubic tenderness costovertebral angle pain, or tenderness
  3. Urine culture with ≥105 colony-forming units (CMF)/ml of one bacterial species.[78]

A and C above is required for asymptomatic infection. While A, B, and C are required for symptomatic infection.

All silicone and latex catheters of various sizes were used for urethral and suprapubic routes observing strict aseptic precautions. The patients on admission were monitored daily for any of these, cloudy urine, pericatheter pain, suprapubic pain, fever, chills or blood in urine, and urine samples were collected from all the patients depending on the time any of these symptoms was noted 48 h after the placement of urinary catheter. For those with bladder outlet obstruction awaiting surgery, the catheters were changed every 3 weeks, and at each visit, urine samples were collected for culture and sensitivity. Prophylactic antibiotics were not used. Any infection detected after insertion of the catheter was treated guided by antibiotic sensitivity and the microorganism involved recorded. The infection was also documented as either asymptomatic or symptomatic. Once the infection is detected in a patient, he or she ceases to participate in the study and the duration of catheterization, complications such as retained catheter, encrustations, catheter blockage, and bladder stone encountered recorded.

Asceptic urethral catheterization

A tray containing the materials for the procedure was set by the nurse. The doctor scrubbed his hands and wore sterile gloves. The patient's glans penis was scrubbed with cetrimide. The patient was draped. Fifteen milliliter (ml) of 2% plain xylocaine gel was introduced into the urethra and allowed to stay for 5 min. The sterile 2-way Foley catheter, either size 16F or 18F was introduced into the external meatus with the phallus pulled up. The catheter was introduced into the urinary bladder up to the Y bifurcation and urine is seen coming out of the catheter. Urine bag was connected to the catheter. Ten milliliter of sterile water was introduced into the balloon channel. The catheter was pulled gently until it wedges on the internal meatus.

Suprapubic cystostomy

The patient was under anesthesia, which was either local or spinal.

After scrubbing and gowning by the surgeon, the suprapubic region was scrubbed with cetrimide and povidone-iodine. The patient was draped. An infra umbilical midline incision 2 cm above the symphysis pubis was made and deepened up to the anterior bladder wall. A purse-string is put on the anterior urinary bladder wall using vicryl 0. The anterior bladder wall was opened at the center of the purse-string using a surgical blade. The catheter connected to the urine bag was introduced into the bladder and fixed using the purse-string vicryl 0. The balloon of the catheter was inflated with 20 ml of sterile water. The wound was closed in layers with nylon to skin.

Collection of the urine sample

The laboratory scientist wearing gloves clamps the catheter for about 30 min to allow urine to collect upstream in the bladder, the urine bag was disconnected, the clamp removed and the urine collected into a sterile universal bottle. The bottle was labeled with the patients name, the gender, and the duration of catheterization. The sterile universal bottle was taken to the laboratory within 30 min of collection of the urine sample.

Culture and sensitivity

The urine sample was taken in a sterile universal bottle to the laboratory. With a sterile calibrated loop, 0.01 ml of the urine sample was delivered into each of the media MacConkey and blood agar plates. It was incubated aerobically at 37°C for 24–48 h. Significant bacteriuria was when there was ≥105 colony-forming units per milliliter of urine. Using the disc diffusion method, antibiotic susceptibility was determined for each of the antibiotics used in this study.

Statistical analysis

The collected data were analyzed using both descriptive and inferential statistics. Frequency and percentage were the descriptive statistics used, while the Chi-square test of association was the inferential statistics used.

Chi-square test of association was used to ascertain if significant relationship/association existed between variables. The level of significance for the Chi-square tests was 5%. Hence, significance existed if P < 0.05 otherwise, no significance.

These analyses were performed with the aid of the Statistical Package for the Social Science (SPSS) version 25 (SPSS Inc., Chicago, Illinois, USA).


A total of 460 newly catheterized patients who met the inclusion criteria were involved. There were 376 (81.7%) males and 84 (18.3%) females giving a male-to-female ratio of 4.5:1. The age range was 3–92, with a median of 61 years. The highest number of patients 157 (34%) was in the eighth decade of life, followed by the seventh decade 142 (30.9%) [Table 1 and Figure 1].

Figure 1:
Graphical representation of age distribution
Table 1:
Age distribution of patients

Table 2 shows the underlying pathology that necessitated catheterization. There were more cases of benign prostatic hyperplasia (32.3%) and prostate cancer (27.2%), as shown in Table 2.

Table 2:
Underlying pathology necessitating catheterization

Table 3a shows the routes of insertion of the catheter. Urethral catheterization was done in 360 (78.3%) patients, while in 100 (21.7%) patients, the catheters were placed suprapubically. In 110 (23.9%) patients, latex catheters were used while 350 (76.1%) patients had 100% all silicone catheters passed into the urinary bladder. There was a significant relationship between the duration of catheterization and the route in the study. Suprapubic route was associated mainly with 15–21 days of catheterization (67.0%), while the urethral route is mainly between 8 and 14 days (25.3%), 15–21 days (36.4%) and 22–28 days (26.1%), and >28 days (10.3%). Chi square is 41.532 (P <.001) as shown in Table 3b.

No title available.

A significant relation was found in the study between the duration of catheterization and the type of infection. Those with asymptomatic infection were associated mainly with 15–21 days of catheterization (47.5%) followed by 8–14 days (26.3%) and 22–28 days (24.4%), respectively. Symptomatic infection was associated mainly with >28 days catheterization (42.5%) followed by 22–28 days (33.3%) and 15–21 days (24.1%). Chi square is 194.192 (P < 0.001) as indicated in Table 3c. The longest duration of catheterization was 96 days in a patient who defaulted in changing the catheter due to financial constraints.

Table 4 shows the frequency of isolation of offending pathogens. Escherichia coli was most isolated (45.2%); Klebsiella (18.0%), Pseudomonas aeruginosa (16.5%), and Proteus (15.0%). In 269 (58.5%) patients, bacterial growth was reported as heavy. There was isolation of Candida albicans in 6 (1.3%) patients.

Table 4:
Pathogens isolated

[Table 5a and b] show the antibiotic sensitivities of the organisms isolated in the UTIs. Meropenem was the antibiotic that had the highest number of cultures exhibiting sensitivity to (26.2%), followed by imipenem (18.5%), ceftriaxone (15.2%), and levofloxacin (15.0%); no culture was sensitive to ampicillin.

No title available.

Table 6 shows the symptoms in those that had the symptomatic infection. Peri-catheter pain along the urethra was the most common symptom followed by pyuria.

Table 6:
Symptoms in patients with symptomatic catheter associated urinary tract infection

The most common complication encountered in this series was catheter encrustation [Figure 2] followed by catheter retention. There were bladder stones in 2 (0.4%) patients, as shown in [Table 7 and Figure 3], showing the stones removed from one patient.

Table 7:
Complications of catheter associated urinary tract infection encountered
Figure 2:
Catheter encrustation in one of the patient with catheter associated urinary tract infection
Figure 3:
Bladder stone in one of the patients with catheter associated urinary tract infection


CAUTIs are a significant source of morbidity to both the outpatient and the general in-patient population. The catheter serves as a portal of entry for the pathogen and if not aseptically inserted in healthy patients, CAUTI is asymptomatic, while in susceptible patients, it leads to symptomatic infection with risk of complications.[910] Furthermore, the risk of infection in the 24 h following the insertion of the catheter is 7.4%, with a steady 8.1% risk increase daily for the first 7 days.[7] There was a 100% infection rate in our series. Alem et al., in their series, also had 100% infection rate.[10] In this study of 460 patients, 376 (82%) were male, while 84 (18%) patients were female. This is explained by the fact that a greater number of the patients were male urological patients suffering from prostatic diseases. This is in line with other studies where there was male preponderance.[41112] More than 50% of patients in this series were above 50 years and those in the eighth decade of life, all males constituted the largest group on the indwelling catheter. These are patients suffering from bladder outlet obstruction from prostatic diseases with indications for urinary catheterization. These findings are in agreement with two previous studies by Taiwo and Aderounmu and Oni et al.[413] However, this is a reversal of what is to be expected in patients on indwelling catheters with asymptomatic bacteriuria in the general population where females are at a greater risk. Females are at a greater risk because of easier access of the perennial flora to the urinary bladder along the outside of the urethral catheter as it ascends the shorter female urethra. Furthermore, the woman's anus being closer to the urethra makes it easier for bacteria to spread into her urethra, causing an infection.[11] Furthermore, the small number of females 84 (18.3%) patients in this study contributed to more CAUTI in males, as was the case in another study.[11]

CAUTI is caused by various pathogens, which include E. coli, Pseuodomonas, C. albicans, Enterobacter, Proteus, Enterococi, Enterobacter, and Serratia.[14911] In this series, E. coli was the most common pathogen isolated (45.2%), followed by Klebsiella (18%) and P. aeruginosa (16.5%). Other studies isolated E. coli as the most common pathogen.[14151617] However, Taiwo and Aderounmu in their series isoilated Klebsiella as the most common pathogen followed by pseudomonas species.[4] Verma et al. and Zahran et al., in their study, found candida as the most common pathogen causing CAUTI.[1218]

In this study, the duration of the indwelling catheter was an independent risk factor for CAUTI. The longer the duration of the indwelling catheter, the more tendency for the CAUTI to be increasing in frequency from asymptomatic to symptomatic. With the increasing duration of indwelling catheter, there are higher chances of ascending infections either intra- or extraluminal.[5] All the CAUTI encountered in the first 14 days of catheterization were asymptomatic (22.8%). However, after 28 days, all the CAUTI was symptomatic. Other studies have found that the duration of catheterization increased the chances of CAUTI because of increased chances of ascending intra-luminal and extraluminal infections getting into the urinary bladder.[457]

It was of interest to note that all the types of catheters used in this study; all silicone and latex were all vulnerable to CAUTI. Furthermore, all of them were involved in encrustations and biofilm formation. Stickler, in his review, noted that all types of catheters are affected by CAUTI, biofilm formation, and encrustation.[19] Biofilm formation occurs along the catheter surface and begins immediately after catheter insertion.[20] It is the most important cause of bacteriuria and is critical for initiating and maintaining CAUTI.[6] Biofilm is a complex organic material that comprises microorganisms growing in colonies within an extracellular mucopolysaccharide substance produced by the bacteria themselves with urine components including Tamm–Horsfall protein, magnesium, and calcium ions incorporated.[1920] The biofilm is advantageous to the organisms within that they are relatively protected from antimicrobial and host defenses. Furthermore, the biofilm of an indwelling catheter has dynamic microbiology with a continuing turnover of organisms within the biofilm as the catheter remains in situ, with new organisms acquiring rate at 3%–7% per day.[20]

Resistance to the commonly used antibiotics, ciprofloxacin, gentamycin, augmentin was noted in this study with increased sensitivity to imipenem and meropenem. Resistance to ampicillin was 100%, ciprofloxacin 97.3%, gentamycin 94.3%, augmentin 96%, nitrofurantoin 96%, and cefuroxime 98%. This pattern of resistance was noted by Taiwo and Aderounmu in their study.[4] The following bacteria have been implicated in the production of biofilm in catheterized patients, E. coli, Klebsiella, Enterococcus faecalis, Stapholococus aureus, Proteus mirabilis, and P. aeruginosa.[21] These are the same pathogens isolated in this study and may account for the multidrug resistance observed. Kazi et al. and Mishra and Rao in their respective studies, reported multidrug resistance.[2223] Other studies also found a correlation between biofilm production and multidrug resistance.[1024] In this series, 81% of the infections were asymptomatic, while 19% were symptomatic. In other studies, asymptomatic infections were >90%.[102425] The reason for the relatively higher incidence of cases of symptomatic infections in this series is that some of the patients carry their indwelling catheters for upward of 12 weeks and above with a resultant symptomatic infection manifesting. A controversy exists among physicians as regards the treatment of asymptomatic bacteriuria. This controversy hinges on striking a balance between the prevention of UTI-related morbidity and the emergence of antimicrobial resistance.[6] Furthermore, the presence of bacteriuria serves as a bacterial reservoir for possible progression into a symptomatic infection.[6] Because in this study, about 91% of these patients are surgical patients awaiting intervention, we treated all asymptomatic bacteriuria to prevent complications such ass cystitis, pyelonephritis, and urosepsis. The most common complication seen in this study was catheter encrustations. These patients had indwelling urethral catheters for more than 12 weeks. The bacteria isolated from these patients are implicated in the production of crystalline biofilms. These crystalline biofilms on catheters are composed of struvite (magnesium ammonium phosphate) and apatite (a hydroxylated form of calcium phosphate in which some of the phosphate ions are replaced by carbonate).[2627] This crystallization is hinged on urease, which hydrolyzes urea into ammonia and carbon dioxide resulting in urine PH rise.[2627] Crystallization of magnesium and calcium phosphate occurs. Accumulating crystalline deposits block the flow of urine through the catheter with serious consequences. P. mirabilis is most commonly associated with catheter encrustation, and its urease can hydrolyze urea several times faster than the urease produced by other organisms leading to faster catheter encrustation and bladder stones.[2627] Bladder stones were encountered in 2 (0.4%) patients. These were spinal cord injured patients on long-term catheterization. Urinary isolates were P. mirabilis. A study on spinal cord injured patients highlighted the prolonged use of indwelling urethral catheters associated with infection with Proteus and stone formation.[28]

As the most important step to prevent CAUTI is the avoidance of catheter use, institutions must develop guidelines showing indications for catheter use. When a catheter is indicated and is inserted, it should be removed promptly once it is no longer needed.[20]


CAUTI still poses enormous challenges to both the outpatients and general inpatients as enumerated above. The most common offending pathogen from this study was E. coli followed by Klebsiella. Most of the organisms encountered were multi drug-resistant to the commonly used antibiotic. The major complications encountered were catheter encrustations and bladder stones. Finally, to minimize CAUTI, indiscriminate use of urinary catheters should be discouraged, and urinary catheters should be removed immediately; they serve the purpose for which they were inserted.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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Encrustations; Escherichia coli; multi drug resistance; urinary catheter; urinary tract infection

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