Antimicrobial resistance patterns in urinary isolates from nursing home residents. Fifteen years of data reviewed

M. Vromena, A. J. A. M. Van der Venb, A. Knolsc and M. E. E. Stobberinghb,*

a Foundation Nursing Homes SVB, PO Box 522, 6460 AM Kerkrade b University Hospital Maastricht, Department of Medical Microbiology, PO Box 5800, 6202 AZ Maastricht c Nursing Home Zeven Bronnen, Lovendaalhoeve 30, 6225 AG Maastricht, The Netherlands


    Abstract
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 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
The antibiotic resistance patterns of Gram-negative bacteria isolated from nursing home patients between 1983 and 1997 were analysed. Escherichia coli was the most prevalent isolate (48%) followed by Proteus spp. (26%) and other Enterobacteriaceae (20%). During the study period, the susceptibility of E. coli decreased for co-trimoxazole (79% to 62%), increased for nitrofurantoin (79% to 91%) and remained unchanged for amoxycillin (41%). Susceptibility to norfloxacin, available from 1990, decreased from 87% to 71%. Similar trends were observed when the susceptibilities of all Gram-negative urinary pathogens were combined. The changes in susceptibility can probably be attributed to the empirical prescribing practices in the nursing homes studied.


    Introduction
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
Antimicrobial agents are among the most frequently prescribed drugs in nursing homes (approximately 40% of all systemic agents used), most commonly for urinary tract infections (UTI). 1 The high consumption of often inappropriately prescribed antibiotics, combined with crowding, multiple pathology and frequent use of invasive devices, is a major factor contributing to high levels of resistance. Several studies of nursing home populations, reviewed by Nicolle et al., 2 have reported highly resistant isolates of bacteria, belonging to genera that are usually susceptible to most antimicrobial agents. In comparison with the extensive data on antibiotic susceptibility of urinary isolates in hospital patients, few reports are available for nursing homes. Data collected between 1988 and 1997, on antibiotic resistance of urinary pathogens isolated from patients presenting to general practitioners with symptoms of acute uncomplicated urinary tract infection, in Southern Netherlands, showed no increase in resistance 3,4 (L. F. H. M. Verest, W. M. J. van Esch, J. van Ree and E. Stobberingh unpublished data). In this study, antibiotic resistance patterns of Gram-negative urinary bacteria isolated from nursing home patients in the same area of the Southern Netherlands from 1983 to 1997 were analysed.


    Materials and methods
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 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
The study was performed in two nursing homes in the Southern Netherlands, which provide care facilities for 204 and 396 residents respectively. In the first home equal numbers of residents live in single, two or four bedded rooms. In the second, the distribution is 15%, 35% and 50% respectively. Seven physicians (including A. K.), specializing in the care of the elderly, are responsible for the medical care of the residents including antibiotic prescribing.

Most antibiotics prescribed were oral compounds, i.e. amoxycillin, co-amoxyclav, doxycycline, norfloxacin and co-trimoxazole. Intravenous therapy, i.e. cefuroxime, piperacillin and gentamicin, was used in cases of severe sepsis only. Urine cultures were performed when clinically undecided, e.g. in the presence of fever, urinary frequency, haematuria or supra pubic pain in the absence of other foci of infection. Microscopy and culture of urine specimens was performed, using standard methods, in the laboratory of one of the nursing homes. Antibiotic susceptibilities were determined by a disc diffusion method using Rosco neo-sensitabs (A/S Rosco, Taastrup, Denmark) for the agents indicated in Table I. The breakpoints used were those defined by the Dutch Working Party on antimicrobial susceptibility testing. 5Escherichia coli ATCC 25922 and ATCC 35218 were used as reference strains. The results of all urine cultures from 1983 to 1997 were available. The first 100 positive urine cultures for each year were used for this study (approximately one-third of all isolates obtained). Mixed infections and cultures with Gram-positive organisms were excluded.


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Table I. Antibiotic susceptibility of the bacteria isolated
 

    Results
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 Materials and methods
 Results
 Discussion
 References
 
The numbers of Gram-negative bacteria isolated from urine during the study period, with their antibiotic sensitivities, are shown in Table I. E. coli was the most prevalent organism (774/1600, 48%) followed by Proteus spp. (26%) and other Enterobacteriaceae (20%).

Less than 50% of isolates of E. coli and Proteus spp. were susceptible to amoxycillin. The highest susceptibility rates were found to be for cefotaxime (85% for Proteus spp., 95% for E. coli and other Enterobacteriaceae). More than 80% of all Enterobacteriaceae and Providencia stuartii, and 72% of Pseudomonas spp., were sensitive to gentamicin.

Changes in antibiotic susceptibility during the study period for E. coli are shown in Figure 1: susceptibility to co-trimoxazole decreased (79% to 62%), nitrofurantoin showed an increase (79% to 91%), whereas for amoxycillin no change was observed (41%). The susceptibility to norfloxacin, available from 1990, decreased from 87% to 71%. Trends similar to those demonstrated for E. coli were observed for the sensitivity patterns of all the isolates studied.



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Figure 1. Antibiotic susceptibility (%) of Escherichia coli isolated from 1983 to 1998. •, amoxycillin; {circ}, nitrofurantoin; {blacktriangledown}, co-trimoxazole; {triangledown}, norfloxacin; dashed line, regression line.

 

    Discussion
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 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
The prevalences of different urinary pathogens isolated in nursing home patients during the study period showed little change. E. coli and Proteus spp. were the most common. Similar results were reported from the western part of the Netherlands. 6 P. stuartii, an important pathogen in patients with urinary catheters, 2,7was isolated only 15 times. Unfortunately, no precise data were available for the frequency of urinary catheter use in the patients studied. Use of these devices is restricted in the two nursing homes (less than 4% of the residents).

The decrease in susceptibility to co-trimoxazole and increase to nitrofurantoin are most likely to be due to the pattern of empirical prescribing in the study nursing homes. The first choice agent was, and is still, co-trimoxazole. Nitrofurantoin is less frequently used, because of side effects such as nausea. Since 1990, norfloxacin has also been used as empirical therapy, especially in complicated UTI.

In contrast to the changes in antibiotic susceptibility in the present study, the susceptibility of isolates from patients with acute uncomplicated UTI, attending their general practioners in the same area, has not changed in 10 years. Around 80% of the isolates remain susceptible to amoxycillin, 12% to trimethoprim and co-trimoxazole, and 97% to nitrofurantoin 4 (L. F. H. M. Verest, W. M. J. van Esch, J. van Ree and E. Stobberingh unpublished data). Resistance to norfloxacin was not observed. The differences in antibiotic susceptibility between the isolates from general practice patients and nursing home residents can be attributed to the presence of additional risk factors for antibiotic resistance in the latter group. These include frequent antibiotic use, overcrowding, underlying pathology and the presence of invasive devices. 2 Differences in ages of the two populations may also be contributory. Nursing home patients are over 75 years old, whereas general practice patients presenting with UTIs have an average age of 30 years.

The observed decrease in susceptibility to norfloxacin, which is similar to that seen for co-trimoxazole, is worrying. During the relatively short time that norfloxacin has been available, there has been a 25% increase in resistance rates. Resistance to norfloxacin implies cross resistance to other fluoroquinolones, or the rapid development of resistance if those agents are used. 8 Prudent use of norfloxacin and other fluoroquinolones is essential. These compounds should only be used when resistance to other agents has been demonstrated, and not as initial blind therapy.

Antibiotic use must be prudent, if the emergence of antibiotic resistance is to be controlled. This is particularly pertinent in an ageing population, with additional risk factors for acquisition of infection. 9 To achieve this, evidence-based guidelines for antibiotic use, guided by surveillance studies of target bacteria, need to be developed and implemented. 10



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Figure 2. Antibiotic susceptibility (%) of all Gram-negative bacteria isolated from 1983 to 1998. •, amoxycillin; {circ}, nitrofurantoin; {blacktriangledown}, co-trimoxazole; {triangledown}, norfloxacin; dashed line, regression line.

 

    Notes
 
* Corresponding author. Tel: +31-43-3874644; Fax: +31-43-3876643; E-mail: pter{at}lmib.azm.nl Back


    References
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 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
1 . Wayne, S. J., Rhyne, R. L. & Stratton, M. (1992). Longitudinal prescribing patterns in a nursing home population. Journal of the American Geriatrics Society 40, 53–6.[ISI][Medline]

2 . Nicolle, L. E., Strausbaugh, L. J. & Garibaldi, R. A. (1996). Infections and antibiotic resistance in nursing homes. Clinical Microbiology Reviews 9, 1–17.[Abstract]

3 . Stobberingh, E. E. & Houben, A. W. (1988). Antibiotic resistance and antibiotic utilization of urinary tract infection in 11 family practices in Maastricht. Nederlands Tijdschrift voor Geneeskunde 132, 1793–7.[Medline]

4 . Trienekens, T., Stobberingh, E., Beckers, F. & Knottnerus, A. (1994). The antibiotic susceptibility patterns of uropathogens isolated from general practice patients in southern Netherlands. Journal of Antimicrobial Chemotherapy 33, 1064–6.[ISI][Medline]

5 . Van Klingeren, B. & Mouton, R. P. (1990). Standardization of Susceptibility Testing. Report of the Working Group on Susceptibility Testing. National Institute for Public Health and Environmental Hygiene, Bilthoven, Netherlands.

6 . Achterberg, W. P., Peerbooms, P. G. H. & Brühl, K. G. B. (1997). Direct antibiotic sensitivity testing in the treatment of urinary tract infections in a nursing home. Tijdschrift voor Gerontologie en Geriatrie 28, 7–10.[Medline]

7 . Garibaldi, R. A., Brodine, S. & Matumiya, S. (1991). Infections among patients in nursing homes: policies, prevalence, problems. New England Journal of Medicine 305, 731–5.[Abstract]

8 . Muder, R. R., Brennen, C., Goetz, A. M., Wagener, M. M. & Rihs, J. D. (1991). Association with prior fluoroquinolone therapy of widespread ciprofloxacin resistance among Gram-negative isolates in a Veterans Affairs Medical Center. Antimicrobial Agents and Chemotherapy 35, 256–8.

9 . American Society for Microbiology. (1995). Report of the ASM task force on antibiotic resistance. Antimicrobial Agents and Chemotherapy 39, Suppl., 1–23.[Free Full Text]

10 . House of Lords Select Committee on Science and Technology. (1998). Resistance to Antibiotics and other Antimicrobial Agents. Stationery Office, London.

Received 12 August 1998; returned 23 November 1998; revised 22 December 1998; accepted 4 March 1999