In this study, urinary catheter utilization rates, the causative agents for catheter-associated urinary tract infection (CAUTI) and their antimicrobial susceptibilities in intensive care units (ICUs) in 2009 were investigated at Gazi university hospital. We aimed to determine the causative agents and risk factors for CAUTIs, and antimicrobial susceptibilities of the pathogens; and also sensitivities of Candida spp. to antifungal agents with Microdilution and E-test. The most common etiological agents of CAUTIs were Candida spp. (34.7%). The most frequently isolated Candida spp. was C.albicans (52.4%). All C. albicans spp. were sensitive to fluconazole. Microdilution, used as a reference method to determine the sensitivity to antifungal agents, was compared with E test. E test was found to be sufficient to analyze sensitivity to amphotericin B, caspofungin, fluconazole and voriconazole, but inappropriate for itraconazole. E.coli and Klebsiella spp. were found to be causative agents for CAUTI in 20.6% and 9.9% of cases respectively. Pseudomonas spp. And Acinetobacter spp. were isolated in 14% and 8.2% of the cases, respectively. All E.coli and Klebsiella strains were found sensitive to carbapenems. Carbapenem sensitivity was found in 47.1% and 30% of the cases infected with Pseudomonas and Acinetobacter strains, respectively. According to our results, fluconazole therapy seems to be an appropriate choice for the treatment of CAUTIs caused by C.albicans. Third and fourth generation cephalosporins should not be used for empirical treatment because of the high prevalence of extended spectrum beta-lactamase production among E.coli and Klebsiella isolates.
KEYWORDS: antimicrobial, antifungal susceptibility, microdilution
Bosn J Basic Med Sci. 2014;14(4):227-233. © 2014 ABMSFBIH
Urinary tract infections (UTIs) account for about 30%-40% of all hospital associated infections and are important since they increase mortality, morbidity, duration of hospital stay and health costs [1-3]. The most important risk factor for developing a UTI is urinary catheterization. It is estimated that 15%-25% of all the patients hospitalized in health centers undergo urinary catheterization at least once during their hospital stay and it is reported that the frequency of urinary catheterization has increased in the past 20 years. Patients admitted to intensive care units (ICU) are the most appropriate candidates for UTIs due to their more frequent necessity of urinary catheterization and longer duration of catheter use [1,3,4].
Apart from urinary catheterization, the other risk factors for developing a UTI are identified: Female gender, antibiotic use, diabetes mellitus, renal failure, malnutrition, omissions in urinary catheter care, contamination of drainage bags and periurethral colonization. Bacteriuria associated with duration of urinary catheter use is most commonly caused by a single pathogen, which is mostly a species of Candida or a gram negative enteric bacterium [1,2,4]. Before receiving the antibiotic susceptibility results, the antibiotics that should be considered are the ones that are thought to have the least resistance. After receiving culture results, the antibiotics that the pathogens are susceptible for should be used. The reason for not choosing.
The aim of this study was to determine the incidence of CAUTIs, risk factors, causative agents and their antimicrobial susceptibilities, and sensitivities of Candida spp. to antifungals with Microdilution and E-test in ICUs at Gazi University Hospital.
Gazi University Clinical Research Ethics Committee approved the study in accordance with Helsinki Declaration.
The setting of the study is a university hospital in which all types of patients are treated and followed. Furthermore, it has a capacity of 1081 beds. CAUTIs were diagnosed in 832 patients admitted to five different ICUs (Anesthesiology and Reanimation ICU, Neurosurgery ICU, Internal Medicine ICU, General Surgery ICU, Neurology ICU) at Gazi University Hospital between 1 January and 31 December 2009 according to the criteria issued by the Centre for disease control and prevention (CDC) in 2008 . Out of 101 patients developing CAUTI, 49 (48.5%) were female and 52 (51.5%) were male.
The patients needing a supported respiration or the ones who will be in a need of long-term respiratory support are treated in Anesthesiology and Reanimation ICU. The patients whose vital signs are deteriorated after intracranial operation are treated in Neurosurgery ICU. In General Surgery ICU, the patients whose vital signs are deteriorated or unstable after operations are treated. The patients suffering from chronic diseases and the ones in poor general condition (for example; patients with diabetes mellitus (DM) or kidney failure and immune compromised patients, etc. are treated in Internal Medicine ICU; finally, the patients who had a cerebrovascular incident and the ones who have central nervous system diseases with unstable clinical findings are treated in Neurology ICU.
The information on patients was collected through daily (week days) visits of infection control nurses and was noted in the hospital infection charts. These specified charts contain data such as age and gender; underlying diseases, infection risk factors, the signs of infection, infection development period after hospitalization, the use of foreign objects (e.g.; urinary catheter), survival status, culture and antimicrobial susceptibility results, concomitant nosocomial infections (for example: bacteremia, ventilator-associated pneumonia, bloodstream infections, etc.), the antibiotics used and the treatments taken before the diagnosis of a CAUTI. In intensive care units, urine samples were taken from closed urine drainage systems. In order to prevent disruption of this closed system, urine samples were taken without opening the junction of the catheter collection tube. These samples were then sent to Microbiology or Infection Diseases laboratory. The microorganisms which had been isolated from the patients diagnosed with catheter-associated urinary tract infections were obtained from the Microbiology and Infectious diseases laboratories. The strains isolated from the patients were kept at Micro bank (Pro-Lab, Canada) at -80°C. Antimicrobial susceptibilities of obtained strains were evaluated.
Fungal species were inoculated into Sabouraud Dextrose Agar. Following their inoculation at 37°C for 48 hours, germ tube formation in the resultant colonies was examined and C. albicans and other fungal species were identified. The species other than C. albicans were inoculated in Cornmeal Tween agar. Following their inoculation at 37°C for 48 hours, C. Glabrata was identified under direct microscopic examination. Other fungal species were identified with ID-32C kit (bioMerieux, France).
Bacteria were identified with BBL Crystal Enteric/Nonfermenter ID Kit and BBL Crystal Gram-Positive ID Kit (Becton Dickinson, USA) in addition to conventional methods.
Microdilution and E-test were used to investigate sensitivity to fluconazole, voriconazole and amphotericin B and in both methods, C.parapsilosis ATCC 22019 and C.krusei ATCC 6258 species were used as controls.
a. Microdilution: The sensitivity of Candida species to antifungal agents was investigated as recommended in M27-A3 guidelines by Clinical and Laboratory Standards Institute (CLSI). RPMI 1640 liquid agar with L-glutamine, without sodium bicarbonate was used for inoculation. Since its pH should be 7.0, the agar was tamponated with molar morpholinepropanesulfonic acid (MOPS), the pH of which was 0.165. Fluconazole was diluted in the range of 0.12-64 µ/mL and other drugs were diluted in the range of 0.03-16 µ/mL. Before the test, stock solutions of the drugs were two-fold diluted. Fluconazole and caspofungin solutions were prepared with test agars, and solutions of amphotericin B were prepared with the solvent dimethyl sulphoxide (DMSO); finally, the solutions of other antifungal agents were prepared with water. Exposure of amphotericin B solution to light was prevented. U-shaped polypropylene ninety-well microplaques were used for preparation of the solutions. After 24-hour incubation, the value from the well which looked clear first in absence of growth was considered as minimal concentration value (MCV) for amphotericin B and caspofungin. The value from the well where growth decreased considerably and which became clearer first at least by 50% was considered as MCV for azoles.
b. E-test: E test was performed in RPMI agar with 2% glucose by a commercially available product by AB Biodisk (Solna, Sweden). As in disk diffusion method, the amount of inoculum was prepared as it was equal to 0.5 McFarland turbidity standards and contained 106 inoculum densities CFU/mL. The inoculum was spread on the plaques and inoculated for 48 hours. The first contact on the strip on which inhibition ellipsis appeared was considered as MCV and microcolonies in the zone were disregarded as in disk diffusion test.
c. Comparing microdilution with E-test: Since MICs obtained with E-test could be compared with those with microdilution easily, when a strain was found to be resistant or sensitive with one method and sensitive with the other method depending on the dose, it was considered a small mistake; when a strain was found to be resistant with E -test but sensitive with microdilution, it was considered to be a big mistake; and, finally, when a strain was found to be sensitive with E -test but resistant with microdilution, it was considered a very big mistake .
Sensitivity to antimicrobial agents was tested with Kirby-Bauer disk diffusion in accordance with CLSI standards and Mueller Hinton Agar was used. Antimicrobial agents to be used in sensitivity analyses of microorganisms were selected in accordance with recommendations of CLSI [7,8]. Oxoid disks were used for tigecycline, and Bioanalyse disks fulfilling CLSI standards were used for the others. The cut-off value for sensitivity to antimicrobial agents was based on CLSI, the cut-off value for sensitivity to tigecycline was based on European Committee for Antimicrobial Susceptibility Testing (EUCAST) and the cut-off value for the sensitivity to cefoperazone-sulbactam was set as found in the literature [8-11]. S. aureus ATCC 25923, E. coli ATCC 35218 and P. aeruginosa ATCC 27853 were used as standard strains to check the standardization of the disks.
Statistical Package Program for Social Sciences 15.0 was used for statistical analyses. Descriptive statistics were used to determine patient characteristics; the relation between features of microorganisms and patient characteristics were analyzed using Yates corrected Pearson correlation and Fisher's Chi-square tests. p<0.005 was considered statistically significant.
The study population included 832 patients hospitalized in five different ICUs at Gazi university hospital. A hundred and one patients developing 126 attacks of catheter associated urinary tract infections (CAUTI) were included in the study sample. Of 101 patients, 85% suffered at least one attack of CAUTI, 7% suffered two attacks of CAUTI and 6% suffered three or more attacks of CAUTI.
Out of 101 patients developing a CAUTI, 49 (48.5%) were female and 52 (51.5%) were male. These 101 patients developed a total of 126 attacks of CAUTI. They were aged between 18 years and 89 years (±16.9) with a mean age of 64.9 years. Fifty-four point five percent of the patients were aged 65 years or older. Sixty-two patients (61.4%) were found to have signs of systemic inflammatory response syndrome (SIRS).
Forty-three patients (42.6%) recovered; however, 58 of them (57.4%) died. The rates of ventilator use (p<0.001), vascular interventions (p=0.001), endoscopic interventions (p=0.01), ventilator associated pneumonia (p=0.007), primary blood circulation infections (p=0.03) and SIRS (p=0.04) signs were significantly higher in patients who died.
Of all CAUTIs, 71 (58.7%) were due to gram-negative bacteria, 42 (34.7%) were due to Candida spp. and 8 (6.6%) were due to gram-positive bacteria. The most frequently isolated causative agent was Candida spp. (34.7%), followed by E.coli (20.6%), Pseudomonas spp. (14%), Klebsiella spp. (9.9%) and Acinetobacter spp. (8.2%).
Out of 126 attacks of CAUTI, 42 (34.7%) were caused by Candida spp. and 84 (65.3%) were caused by bacteria. Differences between the patients in whom Candida was isolated and those in whom bacteria were isolated were investigated. When survival and mortality rates were compared, it became evident that mortality rates were significantly higher in patients in whom Candida spp. were identified (p=0.008). As for the underlying diseases, the rate of infection with Candida spp. was significantly higher in patients with diabetes mellitus (DM), but the rate of infection with bacteria was significantly higher in patients without DM (p=0.04), furthermore the rate of infection with Candida spp. was significantly higher in patients requiring ventilation (p=0.01). In addition, the rates of intubation, mechanical ventilation and vascular interventions were significantly higher in patients infected with Candida (p=0.02, p=0.01, p=0.007). The rate of SIRS was significantly higher in patients infected with bacteria (p=0.04).
Table 1 shows MIC values of Candida spp. for amphotericin B and caspofungin and MIC50 and MIC90 values of C.albicans. Sensitivity to amphotericin B and caspofungin was found to be similar with proximate MIC values shown by both microdilution and E-test.
TABLE 1. Sensitivity of Candida spp. isolated from CAUTIs to caspofungin and amphotericin B.
Table 2 shows MIC values of Candida spp. for itrakonazol, fluconazole and voriconazole as shown by both microdilution and E-test. There were differences in MIC values between these three antifungal agents.
TABLE 2. Sensitivities of Candida spp. isolated from CAUTIs to itraconazole, voriconazole and fluconazole
Table 3 shows data from comparisons of ±2 dilution conversions to evaluate consistency between E-test and microdilution.
TABLE 3. Categorical agreement (CA) between 2 methods: MIC Values of Candida spp. obtained with E-test and those obtained with microdilution (n=42).
There was no error in determining the sensitivity to caspofungin and amphotericin B with both E-test and microdilution methods. However, there were different rates of errors in determining the sensitivity to fluconazole, voriconazole and itraconazole (Table 2). Categorical agreement (CA) between 2 tests was above 80%, for fluconazole and voriconazole, while it was below 64.3% for itraconazole.
E.coli and Klebsiella spp., which were found to be the second and the third most frequent causative agents respectively, were not resistant to carbapenems, but they were resistant to piperacillin and tazobactam in 28% and 66.7% of the infections, cefoperazone and sulbactam in 32% and 66.7% of the infections and ceftazidime in 72% and 100% of the infections respectively. E.coli and Klebsiella spp. were found to produce large spectrum betalactamase in 64% and 91.6% of the infections respectively. Pseudomonas and Acinetobacter spp. were resistant to carbapenem in 52.9% and 70% of the infections respectively, but they were not resistant to colistin.
In this study, 48.5% of the patients were female, the mean age of the patients was 64.9 years and 54.5% of the patients were 65 years old or older. Sixty-two patients (61.4%) had signs of SIRS during attacks of UTI. As for other risk factors, of all the patients, 48.5% were had immunosuppression, 18.8% suffered from a malignant disease or trauma, and 17.8% of patients suffered from DM. In Clec’h's, Erben's and Talaat's studies, age over 65 years, female gender, presence of DM, mechanical ventilation, central venous catheterization and unconsciousness were reported to be risk factors [3,12,13]. The results of our study were consistent with the results of other studies in terms of risk factors.
In the present study, the crude mortality rate in patients developing CAUTI was 57.4%. According to data from International Nosocomial Infection Control Consortium, the crude mortality rate is 35.8% and the attributed mortality rate is 20.5 . We could not estimate the mortality rate attributable to CAUTIs since our study did not have a control group.
Catheter-related UTI rate in studies involving European countries was 62.2%. Short-term catheterization (under 30 days) rate was 90.8%. The duration of catheterization was 1-7 days for 44.8% of the cases; 8-30 days for 46% of the cases . In our study, more than 50% of the most common CAUTIs were developed within the first 30 days after the beginning of the hospitalization.
In a study from Turkey by Inan et al., the most frequently isolated causative agents were Candida spp. in 37.1% of the UTIs, E.coli in 21.1% of the UTIs and Pseudomonas spp. in 16.5% of the UTIs . Five out of seven studies on causative agents of CAUTIs revealed that the most frequent agent was Candida spp. and out of the remaining two, one by Gikas et al. revealed that the most frequent agent was P. aeruginosa (30.6%) and the other study by Ko et al. indicated that the most frequent agent was E.coli (23.4%) [3,4,13,16,17-19]. As highlighted above, the most frequently isolated agent was Candida spp., consistent with the findings of our study.
Standard sensitivity of Candida species to antifungal agents is determined by microdilution. Although routine use of E-test is not recommended, in the present study, both E-test and microdilution indicated that Candida spp. had similar MIC values for amphotericin B and caspofungin. However, in this study, these tests revealed different MIC values for azoles; i.e. itraconazole, fluconazole and voriconazole. In the literature, it has been reported that the rate of consistency between these two tests for Candida spp. was 78%-96% [20-25]. The rate of consistency was reported to be 89.3% for fluconazole by Yücesoy et al. and 80.4% for fluconazole, 95.6% for voriconazole, 93.4% for caspofungin and 84.7% for amphotericin B by Özcan et al. [26, 27]. As a result, we found a higher rate of consistency for amphotericin B and caspofungin than it was reported in the literature and a similar rate of consistency for fluconazole and voriconazole then was reported in the literature; also, we found a lower rate of consistency for itraconazole.
In the present study, Klebsiella spp. was found to be the fourth most frequent causative agent that was not resistant to carbapenem, but resistant to piperacillin-tazobactam and cefoperazone-sulbactam in 66.7% of the infections and ceftazidime in 100% of the infections. In a study by NHSN, Klebsiella spp. was reported to be resistant to carbapenem in 10.1% of the infections and to ceftazidime in 21.2% of the infections in 2006-2007 [28,29]. In this study, Klebsiella spp. was found to have a high rate of resistance for ceftazidime.
We found E.coli and Klebsiella spp. produced large spectrum beta-lactamase in 64% and 91.6% of the infections respectively. In a study by Talaat, E.coli and Klebsiella spp. were reported to produce large spectrum beta-lactamase in 78.6% and 56% of the infections respectively . The rate of beta-lactamase producing E.coli spp. in this study were lower than it was reported in the literature but the rate of beta-lactamase producing Klebsiella spp. were higher than reported in the literature.
Among other pathogens we isolated in this study, Pseudomonas and Acinetobacter were found to be resistant to carbapenems in 52.9% and 70% of the infections respectively; neither of these pathogens was found to be resistant to colistin. In a study by Gikas, P. aeruginosa was reported to be resistant to carbapenem in 29.8% of the infections, but A. baumannii was reported not resistant to carbapenem . INICC showed that Pseudomonas and Acinetobacter, which were found to be pathogens responsible for CAUTIs, were reported resistant to carbapenem in 34.7% and 38.9% of the infections respectively in 2003-2008 and 36.5% and 52.2% of the infections respectively in 2004-2009 [30,31]. Colistin seems to be the first option for the empirical treatment of infections due to Pseudomonas and Acinetobacter spp. in hospitals where the resistance rates of these species to carbapenem is high. The second most appropriate alternative for the treatment of the infections caused by Pseudomonas spp. could be amikacin and ceftazidime. However, there is no alternative to colistin for the treatment of the infections due to Acinetobacter spp.
In patients with sepsis early initiation of appropriate antibiotic therapy is lifesaving. Ceftazidime and amikacin as the first option is the probability of microorganisms to be resistant.
According to our results, fluconazole therapy seems an appropriate choice for the treatment of CAUTIs caused by C.albicans. Third and fourth generation cephalosporins should not be used for empirical treatment because of the high prevalence of extended spectrum beta-lactamase production among E.coli and Klebsiella isolates. Colistin seems to be the most appropriate choice for the treatment of CAUTI caused by Pseudomonas and Acinetobacter spp.
The authors declare no conflict of interest.
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