Nosocomial infections (NIs) have long been the bane of hospitals and hospital-like nursing homes and hospices. The increasing tendency to the development of antibiotic-resistant strains is just a final complication to a huge underlying clinical and socio-economic challenge. By far the biggest source of NI is associated with the use of indwelling catheters, in particular those used for central venous catheterisation (CVC) or urinary tract catheterisation (UTC). Despite the size of the problem created by urinary tract infections (UTIs), no solid epidemiological data are available regarding the prevalence of microorganisms involved, their antimicrobial susceptibility, etc. Over the last few years, the European Study Group for Nosocomial Infections (ESGNI) has been conscientiously collating information from hospitals throughout Europe and is establishing an information bank that will be of great use in the establishment of data-based preventative strategies. In the meantime, tightening up on the criteria that are currently used to decide to insert urinary tract catheters in the first place (and for how long they should be used) could significantly reduce the overall incidence of UTIs and the associated morbidity and mortality.
Urinary tract infections (UTIs) are the most common nosocomial infections in both acute-care and long-term care facilities, with the results of several European national prevalence studies showing that they account for 23-49% of all nosocomial infections [1]. The costs of prevention, detection and treatment of UTIs can significantly affect healthcare budgeting so that even a small decrease in the UTI rate can have important socio-economic implications.
The biggest single cause of nosocomial UTI is associated with the use of indwelling catheters [Figure 1], [1]. Despite this close association with infections, it was shown as long ago as 1995 that the placement of urinary catheters was not justified in 21% of cases and that continued catheterisation was not justified in an astonishing 47% of patients. Where at all possible, catheterisation of the urinary tract for nursing convenience should clearly be avoided.
Compilation of general data regarding nosocomial infections is somewhat complicated by the fact that the majority of underlying catheter-associated infections are missed, with symptomatic infections frequently only being detected (if culturing is being used as the method for the detection of the infection) when clinical symptoms are already apparent.
The routes of entry of uropathogens are either via the outside of the lumen of the catheters or intraluminally via a breakage in the catheter itself or of the urine collecting bag [Figure 2]. An additional factor that complicates precise analysis is the fact that the data are frequently fragmented, for example being derived from either intensive care (IC) units or non-IC units, but not both. Similarly, many studies report incidences and prevalence of nosocomial infections (NIs) according to the causative organism, whether the patient population was geriatric or not or what the underlying pathology was.
Likewise, data on additional costs created by UTIs’ indwelling catheters focus primarily on the increased cost due to the additional length of stay in the hospital. Comparatively few studies have attempted to compare the relative contribution of nursing care, increases in laboratory use, drugs and diet towards the total costs. Despite these uncertainties, there is however no doubt about the overall gravity of the catheter-associated UTI problem and its economic consequences, to say nothing of the associated morbidity and mortality.
To address these issues, several European working groups have been set up, notably the European Study Group for Nosocomial Infections (ESGNI), itself drawn from members of the European Society of Clinical Microbiology and Infectious Diseases (ESCMID). The starting point of ESGNI’s mission was simply to gather the data specific to urinary tract nosocomial infections. In particular, a study was set up to determine the prevalence of nosocomial UTI and to obtain information on the microbiology workload, the aetiology and the antimicrobial susceptibility [2]. This study (ESGN-003) was designed as a one-day prevalence study that involved the sending of a questionnaire to the microbiology laboratories of every European hospital where one or more ESCMIFD members worked. Data were received from a total of 228 hospitals from 29 European countries.
The questionnaire asked for information on the population served by the hospital, the total number of beds, the total number of admissions, the total number of urine samples processed and the total number of significant positive samples found. The most common microorganisms involved in UTIs are shown in Table 1. In this study, positivity was determined by culture methods, and the results expressed as the number of colony-forming units per mL of urine.
The ESGNI 003 study was complicated by the fact that no clear consensus existed as to what constituted a positive cut-off value. Several cut-off values had previously been used, but since these had been established on the basis of specific populations, extrapolation to other populations was considered not to be valid. In the ESGNI 003 study, the majority of participating labs used cut-off values of >104–105cfu/mL for bacteria and greater than 103 cfu/mL for yeasts.
In addition to highlighting the need for a European consensus on the practice and interpretation of the results of culture analysis of urine, the study also emphasised the significant contribution to the overall workload that catheter-associated UTIs created in the microbiology lab. More ominously, the study confirmed the changes in the patterns of antimicrobial resistance, an observation that had already been reported in smaller, more local studies.
Many studies have revealed changes in the aetiology of nosocomial infection. The ESGNI group found that E. coli, Enterococcus and Candida species were, in decreasing order, the top three pathogens isolated from patients with nosocomial UTI. Staphylococcus aureus was the second most common Gram-positive pathogen isolated responsible for nosocomial UTI in this European study. With the exception of P. aeruginosa, which was more frequently isolated among non-EU patients, the distribution of UTI pathogens was comparable between EU and non-EU countries [Table 1].
In another study (ESGNI - 005), the group correlated data on antimicrobial resistance patterns. Results broadly confirm the data reported in other studies. Although caution must be exercised in the interpretation of the data since susceptibility-testing was not confirmed by uniform methods in a central laboratory and the number of isolates was limited, certain trends could nevertheless be seen. Resistance to ampicillin, one of the most commonly used agents for the empirical treatment of UTIs, was as high as 54.8% in the case of E. coli. The overall resistance rate to ampicillin in Gram-negatives was 66%. Twenty-one per cent of the E. coli isolates were resistant to cotrimoxazole; a resistance rate similar to those from other European studies, but higher than those reported from the USA.
Conclusion
The data being compiled by the ESGNI are at last providing a quantified analysis of the nature of the problem caused by nosocomial infections related to indwelling catheters and are providing a solid basis for the development of data-based preventative strategies. In the meantime, however, the situation could already be improved simply by the adoption of common-sense procedures such as restricting the use of indwelling catheters to those cases that really need them.
References
1. Gastmeier. Nosocomial urinary tract infections: many unresolved questions. Clin Microbiol and Infection 2001; 7: 521.
2. Hazelett SE et al. The asscoiation between indwelling urinary catheter use in the elderly and urinary tract infection in acute care. BMC Geriatrics 2006; 6:15.
3. Bousza et al. A European perspective on nosocomial urinary tract infections 1. Report on the microbiology workload, aetiology and antimicrobial susceptibility. ESGN - 003 study. Clinical Microbiol and Infection 2001;7: 523.
4 Bouza et al. A European perspective on intravscular catheter-related infections: report on the microbiology workload, aetiology and antimicrobial susceptibility (ESGNI - 005). Clinical Microbiol and Infection 2004;10: 838.
