Urinary catheter related nosocomial infections in paediatric intensive care unit.

MS Tullu, CT Deshmukh, SM Baveja 
 Department of Paediatrics, Seth G.S. Medical College, Mumbai. , USA

Correspondence Address:
M S Tullu
Department of Paediatrics, Seth G.S. Medical College, Mumbai.
USA

Full Text

::   Introduction

Invasive monitoring of patients in intensive care units (ICU) is being increasingly done. Urinary catheterization is a routine procedure in an intensive care unit for monitoring urine output of critically ill patients. Hence, it is not surprising to find urinary tract infection as one of the most common site of nosocomial infections along with pneumonia, skin infections etc. in the ICU. The incidence of nosocomial urinary infection varies from 17.2% to 44.0%[1].The present study aimed to determine the incidence, risk factors, mortality and organisms causing urinary catheter related infection (UCRI) in the paediatric intensive care unit (PICU).

::   Material and method

The study was conducted in the PICU of a tertiary care teaching hospital over a period of 6 months. Neonates, trauma cases and pediatric surgical cases were not included. All patients with an indwelling urinary catheter (Foley’s catheter) were included in the study. The urinary catheters were inserted and removed using standard aseptic precautions. Major indications for catheterization were - to monitor urine output in hemodynamically unstable patients and in life threatening diseases like shock, multiorgan failure etc. After removal, the tip of each catheter was cut with a sterile blade and sent in a sterile tube for aerobic bacterial culture. Qualitative method was used for isolation of organisms from the urinary catheter tip. The urinary catheter tip was flushed with one ml of glucose broth. A loopful of the broth was taken and inoculated on blood agar and MacConkey’s agar. The plates were incubated overnight. The organisms were identified depending on the colony characteristics and biochemical reactions. Simultaneously, a gram stained smear was also prepared. Also, urine was collected through the draining portal of the urinary catheter using aseptic precautions (after 48 hours of catheter insertion) and analyzed for aerobic bacterial culture. A suprapubic tap was done (after removal of the catheter) for urine collection in all the patients with positive growth from urinary catheter tip and/or urine collected through the urinary catheter. The urine thus collected was sent for aerobic bacterial culture. None of the patients had local infection or prior urinary tract infection as determined clinically and by routine urine examination. The urine culture was done by semiquantitative method using standard loop method and a colony count of more than 105 colony forming units (CFU) per ml was taken as significant. A blood culture was done in all the patients after 48 hours of insertion of the urinary catheter for detection of bacteremia.

‘Colonization’ of the urinary catheter was defined as positive growth from the urinary catheter tip culture. ‘Bacteriuria’ was defined as a colony count of more than 105 CFU per ml of organism/s from the urine sample collected through the urinary catheter after 48 hours of catheter insertion. Colonization of the urinary catheter and/or bacteriuria were termed as Urinary Catheter Related Infection (UCRI). Urinary catheter related sepsis was diagnosed when the same organism was grown from the blood culture as that colonizing the urinary catheter or same as that isolated in the urine collected through the catheter. Following risk factors were studied to evaluate their significance in UCRI - Age, sex, immuno-compromised status (protein energy malnutrition grade-III/IV by IAP classification and HIV positive cases), duration of catheterization (more than 7 days) and duration of ICU stay (more than 3 days). Chi Square test was used to determine the significance of these risk factors in causing UCRI. Probability value (‘p’ value) was calculated from standard charts and considered to be significant when it was less than 0.05. Antibiotic susceptibility was determined using the Kirby-Bauer method and the results were interpreted as per National Committee for Clinical Laboratory Standards (NCCLS) guidelines[2].

::   Results

A total of 44 patients were studied. The total number of urinary catheters inserted was 51. The catheter was changed once in four patients and thrice in one patient. Mean age of the study group was 6.3 years (two years to 12 years). Nineteen patients were female and 25 were male. Average days of catheter in-situ was 5.16 days per patient (two days to 16 days). Average duration of stay in the PICU was 7.13 days per patient (two days to 24 days). Urinary catheter tip culture was positive (colonization) in 21 out of 51 samples (41.18%) with isolation of 28 organisms. Urine culture collected through the catheter (bacteriuria) was positive in 10 out of 51 samples (19.61%) with isolation of 14 organisms. UCRI was seen in 24 out of 51 samples (47.06%). Suprapubic urine culture was positive only in one patient with Pseudomonas aeruginosa being isolated from that culture. None of the patients had the same organism isolated from the catheter tip culture/culture of urine collected through the catheter and the blood culture. Thus, there was no case of catheter related sepsis. The blood cultures in the patients studied did not show growth of any organism.

Eleven out of 20 patients in age group of 1-5 years and nine out of 24 patients in age group of 5-12 years had UCRI. The difference between the two age groups was not statistically significant. Ten out of 19 female patients and 10 out of 25 male patients developed UCRI. Female sex was not more susceptible than male as regards UCRI. One out of six immunocompromised and 19 out of 38 immuno-competent patients developed UCRI. The immuno-compromised group did not have a higher incidence of UCRI.

Eleven out of 12 patients with catheter in-situ for more than seven days developed UCRI as compared to nine out of 32 with catheter in-situ for less than/equal to seven days. The difference was statistically highly significant (‘p’ value less than 0.01).

Nineteen out of 37 patients (51.35%) with a PICU stay more than three days developed UCRI as compared to one out of seven patients (14.29%) with a PICU stay of less than/equal to three days. There was a higher risk of acquiring UCRI in patients with more than three days of stay in PICU but the ‘p’ value did not reach statistically significant level (‘p’ value near 0.05 but between 0.05 and 0.1)

Thirteen out of 44 patients died in our study (mortality-29.54%). Four out of 20 patients with UCRI died and nine out of 24 patients without UCRI died. The mortality was not significantly higher in patients with UCRI.

The commonest organisms colonizing the tip of the urinary catheter were E. coli (46.43%), Pseudomonas (17.86%), Klebsiella (17.86%), Citrobacter (10.71%) and Acinetobacter (7.14). E. coli isolated from the urinary catheter tip culture was susceptible to amikacin and cefuroxime while Pseudomonas was susceptible to pfloxacin, norfloxocin and ciprofloxacin [Table:1]. Common organisms isolated from urine collected through the catheter (bacteriuria) were E. coli (64.29%), Pseudomonas (14.29%), Proteus (7.14%), Citrobacter (7.14%) and Klebsiella (7.14%). E. coli isolated from the urine collected through the catheter was susceptible to nitrofurantoin and amikacin while Pseudomonas was susceptible to amikacin [Table:2]. The commonest organisms isolated from urinary catheter tip culture and/or urine collected through the catheter (i.e. the organisms causing UCRI) were E. coli (52.38%) and Pseudomonas (16.67%) [Table:3].

::   Discussion

Urinary catheterization is a common procedure done in critically ill patients in the PICU. UCRI is the commonest complication of the procedure.

The micro-organisms can gain entry to the urinary bladder during the catheterization procedure or by migration between the external catheter surface and the urethral epithelium[3]. Thornton et al have suggested that the ascending infection from the lumen of the drainage tube may be the major pathway by which bacteria gain access to the urinary bladder[4].

Our study showed the incidence of colonization of catheter tip to be 41.18% and incidence of bacteriuria to be 19.61%. Colonization and/or bacteriuria (i.e. UCRI) was seen in 47.06% of cases. Mulhall et al, Garibaldi et al and Schaeffer et al have shown the incidence of bacteriuria to be 44%, 23% and 35% respectively[3],[5],[6].

A suprapubic tap was performed for urine culture in all the patients with UCRI after removal of the catheter. Only one patient had positive growth (Pseudomonas) from the culture of urine obtained by suprapubic tap. Rest of the urine samples did not show any growth. This indicates that the incidence of urinary tract infection is low even though colonization or bacteriuria is common.

Age, female sex and immunocompromised status did not increase the incidence of UCRI in our study. Garibaldi et al have documented a higher risk for developing bacteriuria in adult female patients, the elderly and critically ill patients with a urinary catheter[5].

We found a significantly higher risk of acquiring UCRI in patients with catheter in-situ for more than 7 days. Mulhall et al showed that the number of days of the urinary catheter in-situ was a significant factor in acquiring catheter related infection[3]. Garibaldi et al have shown the risk of bacteriuria in indwelling urinary catheters to be 8.1% for each day the catheter remains in-situ[5].

We also found that the duration of stay in the PICU of more than 3 days had higher risk of acquiring UCRI (as compared to those with a PICU stay of 3 days or lesser) though the ‘p’ value was not statistically significant. Longer stay in the PICU increases the colonization of skin and environment of the patient and may be responsible for higher incidence of UCRI.

None of our patients developed urinary catheter related sepsis or bacteremia. Urinary catheter related sepsis is uncommon and has been reported previously[7],[8].

Thirteen out of 44 of our catheterized patients died (mortality 29.54%). Du Pont et al have shown the mortality rate to be 20-50% in urinary catheter related sepsis[8]. None of the patients in our study had urinary catheter related sepsis & the mortality was probably contributed to by the underlying critical condition of the patients rather than the presence of urinary catheter.

E. coli was the commonest organism isolated in UCRI in our study. This observation is similar to that by Schaeffer et al and Igra et al[6],[9]. Schaeffer et al isolated Staphylococcus aureus, Staphylococcus epidermidis and Streptococcus fecalis in addition.[6] We did not isolate Staphylococcus in our study. E. coli isolated in UCRI was susceptible to nitrofurantoin and amikacin. A knowledge of the organisms isolated and their antimicrobial susceptibility helps in decision regarding the antimicrobial therapy.

::   Conclusions

Urinary catheter related infections (colonization of catheter tip and/or bacteriuria) are common in patients in PICU. Duration of catheterization of more than seven days and PICU stay of more than three days increased the risk of UCRI and were the two most important risk factors increasing the incidence of UCRI. E. coli was the commonest infecting organism in our study.

References