Risk factors for acquisition of multiply drug-resistant gram-negative bacteria

Use of biofilm model systems to study antimicrobial susceptibility

There are many laboratory biofilm models available which can be used to assess the susceptibility of these distinctive resistant phenotypes. The complexities of these models vary considerably and indeed, the antimicrobial susceptibility of biofilms grown in these different models are also not standardised. It is clear that such methods are necessary for the testing of antibiotics and antimicrobial agents since these persistent communities are far more resistant than their planktonic counterparts. Therefore, it is now apparent that standardised tests such as MIC are no longer appropriate on their own to fully characterise susceptibility. There has also been a growing realisation that bacteria are growing as biofilms in almost every health-care setting and are, thus, a major contributing factor to the difficulty of treating infections. There is a pressing need for the models outlined in this chapter to test both current and novel anti-biofilm compounds and materials.

Antimicrobial use and resistance among Gram-negative bacilli in an Italian intensive care unit (ICU)

Gram-negative bacilli antimicrobial resistance remains a significant problem for patients in the intensive care unit (ICU). We performed a retrospective analysis of microbiological data and antibiotic consumption over a 4-year period (2000-2003) in an Italian ICU. Pseudomonas aeruginosa and Klebsiella pneumoniae represented approximately 40% of all isolates. The most significant trend in antimicrobial use was an increase in use of 3(rd )generation cephalosporins, imipenem, and ciprofloxacin. A significant trend toward an increase in resistance rates to piperacillin, 3( rd )generation cephalosporins and ciprofloxacin was observed for K. pneumoniae and a positive correlation between resistance and drug-usage was evident for K. pneumoniae and piperacillin, cefotaxime, ceftazidime, cefepime, and ciprofloxacin, but not for piperacillin/tazobactam. No statistically significant correlations were evidenced for P. aeruginosa. Trends in resistances were studied also for Serratia spp and Proteus spp. Isolation rates of extended-spectrum beta-lactamase (ESBL)-producing strains in pathogens studied were high, especially for K. pneumoniae (72%, 160/222) and Proteus spp (41%, 18/43). In conclusion, the study showed high resistance among Gram-negative organisms isolated in the ICU and significant ESBL production. A significant correlation between antibiotic consumption and increasing resistance was evident for K. pneumoniae.

Multidrug-resistant Pseudomonas aeruginosa: risk factors and clinical impact

Pseudomonas aeruginosa, a leading nosocomial pathogen, may become multidrug resistant (MDR). Its rate of occurrence, the individual risk factors among affected patients, and the clinical impact of infection are undetermined. We conducted an epidemiologic evaluation and molecular typing using pulsed-field gel electrophoresis (PFGE) of 36 isolates for 82 patients with MDR P. aeruginosa and 82 controls matched by ward, length of hospital stay, and calendar time. A matched case-control study identified individual risk factors for having MDR P. aeruginosa, and a retrospective matched-cohort study examined clinical outcomes of such infections. The 36 isolates belonged to 12 PFGE clones. Two clones dominated, with one originating in an intensive care unit (ICU). Cases and controls had similar demographic characteristics and numbers of comorbid conditions. A multivariate model identified ICU stay, being bedridden, having high invasive devices scores, and being treated with broad-spectrum cephalosporins and with aminoglycosides as significant risk factors for isolating MDR P. aeruginosa. Having a malignant disease was a protective factor (odds ratio [OR] = 0.2; P = 0.03). MDR P. aeruginosa was associated with severe outcomes compared to controls, including increased mortality (OR = 4.4; P = 0.04), hospital stay (hazard ratio, 2; P = 0.001), and requirement for procedures (OR = 5.4; P = 0.001). The survivors functioned more poorly at discharge than the controls, and more of the survivors were discharged to rehabilitation centers or chronic care facilities. The epidemiology of MDR P. aeruginosa is complex. Critically ill patients that require intensive care and are treated with multiple antibiotic agents are at high risk. MDR P. aeruginosa infections are associated with severe adverse clinical outcomes.

Evaluation of the Inhibitory Effect of Triphala on PMN-Type Matrix Metalloproteinase (MMP-9)

BACKGROUND

This study evaluated the inhibitory activity of triphala on PMN-type matrix metalloproteinase (MMP-9) expressed in adult periodontitis patients and compared its activity with another ayurvedic drug, kamillosan, and doxycycline, which has known inhibitory activity.

METHODS

Matrix metalloproteinases (MMPs) were extracted from gingival tissue samples from 10 patients (six males, four females) with chronic periodontitis. Tissue extracts were treated with the drug solutions, the inhibition was analyzed by gelatin zymography, and the percentage of inhibition was determined by a gel documentation system.

RESULTS

The activity of MMPs was significantly decreased with the use of the drugs. Triphala showed a 76.6% reduction of MMP-9 activity, whereas kamillosan showed a 46.36% reduction at a concentration of 1,500 microg/ml (crude extract) and doxycycline showed a 58.7% reduction at a concentration of 300 microg/ml (pure drug).

CONCLUSION

The present study showed the strong inhibitory activity of triphala on PMN-type MMPs involved in the extracellular matrix (ECM) degradation during periodontitis.

Clinical implications of extended-spectrum beta-lactamase-producing Klebsiella pneumoniae bacteraemia

To identify the clinical implications of extended-spectrum beta-lactamase (ESBL) production, 162 cases of Klebsiella pneumoniae bacteraemia in 154 adults were analysed. Of these cases, 44 (27.2%) were ESBL-producing (ESBLKP). Common sources of ESBLKP bacteraemia included primary bacteraemia (34.1%) and biliary infection (29.5%). The placement of a biliary drainage catheter, nosocomial acquisition, and prior antibiotic therapy were independently associated with ESBL production in multivariate analysis. More cases of ESBLKP than non-ESBLKP received inappropriate antibiotic therapy before culture results were reported (54.5 vs. 3.4%; P = 0.001). In 19 cases of ESBLKP, no significant difference in mortality was observed between patients who received appropriate empiric antibiotic therapy and those who did not (26.3 vs. 20.8%; P = 0.67). The mean length of hospital stay after the onset of bacteraemia was longer in the cases of ESBLKP than in the cases of non-ESBLKP (39.6 vs. 23.9 days; P = 0.008). Directly related mortality was not significantly different between the cases of ESBLKP and the cases of non-ESBLKP (23.3 vs. 20.0%; P = 0.65). None of the patients with biliary infection due to ESBLKP died (0/12; P = 0.03). In conclusion, ESBL production was not significantly associated with death but it had a considerable impact on patients with K. pneumoniae bacteraemia.

Nosocomial bloodstream infections in a Turkish university hospital: study of Gram-negative bacilli and their sensitivity patterns

Treatment of nosocomial bacteraemia is usually governed by the surveillance results of the particular unit. Such results are especially important when antimicrobial resistance rates are high. Multiresistant isolates including Gram-negatives producing extended-spectrum beta-lactamases have been frequently reported in tertiary care units in Turkey. In this study, antimicrobial susceptibilities of Gram-negative blood isolates (n=348) were determined by microbroth dilution tests. The results showed carbapenems (meropenem and imipenem) to be uniformly more potent in vitro than any other drug against the Enterobacteriaceae. Quinolone antibiotics were more active in vitro than aminoglycosides against a range of bacteria. Gram-negative bloodstream isolates were highly resistant to many antimicrobial agents in the hospital. In order to prevent hospital infection and antimicrobial resistance, surveillance of aetiological agents must be performed regularly.

Protection against Helicobacter pylori and other bacterial infections by garlic

Louis Pasteur was the first to describe the antibacterial effect of onion and garlic juices. Historically, garlic has been used worldwide to fight bacterial infections. Allium vegetables, particularly garlic (Allium sativum L.) exhibit a broad antibiotic spectrum against both gram-positive and gram-negative bacteria. Noteworthy results published include the following: 1) raw juice of garlic was found to be effective against many common pathogenic bacteria-intestinal bacteria, which are responsible for diarrhea in humans and animals; 2) garlic is effective even against those strains that have become resistant to antibiotics; 3) the combination of garlic with antibiotics leads to partial or total synergism; 4) complete lack of resistance has been observed repeatedly; 5) even toxin production by microorganisms is prevented by garlic. Helicobacter pylori (H. pylori) is a bacterium implicated in the etiology of stomach cancer and ulcers. The incidence of stomach cancer is lower in populations with a high intake of allium vegetables. We have demonstrated in vitro that H. pylori is susceptible to garlic extract at a fairly moderate concentration. Even some antibiotic-resistant H. pylori strains are susceptible to garlic. Clinical trials are necessary to explore the possibility of using garlic as a low-cost remedy for eradicating H. pylori.

High antibiotic consumption in Danish intensive care units?

Decreased antibiotic susceptibility among microorganisms isolated from intensive care unit (ICU) patients is found to be associated with high total antibiotic consumption or inappropriate use of antibiotics in the ICUs. The aims of this study were: 1) to characterize the antibiotic consumption in Danish ICUs, and in four ICUs with expectedly large differences in levels of antibiotic consumption, 2) to estimate the association between antibiotic susceptibility among isolated microorganisms and antibiotic consumption. This was done by: 1) a retrospective questionnaire study of the annual supply of antibiotics in 1995 to 30 ICUs in Denmark, and 2) a 2-month prospective study of patients and microbiological samples in four Danish ICUs in 1996. We found that the supply of antibiotics to Danish ICUs was substantial, with a median value of 124 DDD/100 patient days. No association was found between high consumption of antibiotics and decreased antibiotic susceptibility in the four ICUs.

New species-related MIC breakpoints for early detection of development of resistance among gram-negative bacteria in Swedish intensive care units

The frequency of decreased antibiotic susceptibility among 534 Gram-negative aerobic bacilli from patients admitted to intensive care units at eight hospitals in Sweden during 1997 was evaluated. MICs of cefepime, ceftazidime, ceftriaxone, ciprofloxacin, gentamicin, imipenem and piperacillin-tazobactam were determined using Etest. Reduced susceptibility (resistant and intermediate/indeterminate susceptible strains) was defined according to the MIC breakpoints of the British Society for Antimicrobial Chemotherapy (BSAC), the National Committee for Clinical Laboratory Standards (NCCLS) and the new species-related breakpoints of the Swedish Reference Group for Antibiotics (SRGA). The BSAC/NCCLS/SRGA breakpoints for susceptible category (mg/L) of Enterobacteriaceae are: cefepime, not available (NA)/8/0.5; ceftazidime, 2/8/2; ceftriaxone, NA/8/0.5; ciprofloxacin, 1/1/0.12; gentamicin, 1/4/2; imipenem, 4/4/1; and piperacillin-tazobactam, NA/16/16. The most frequently isolated organisms were Escherichia coli (n = 160; 30%), Klebsiella spp. (n = 84; 16%), Enterobacter spp. (n = 77; 14%), Pseudomonas aeruginosa (n = 64; 12%) andProteus spp. (n = 28; 5%). Decreased susceptibility among E. coliusing the BSAC/NCCLS/SRGA respective breakpoints (%) were: cefepime, NA/0/2; ceftazidime, 2/2/2; ceftriaxone, NA/1/2; ciprofloxacin, 2/2/8; gentamicin, 21/0/3; imipenem, 0/0/2; and piperacillin-tazobactam, NA/4/4. Corresponding levels of decreased susceptibility (%) among Klebsiellaspp. were: cefepime, NA/0/5; ceftazidime, 2/1/2; ceftriaxone, NA/1/10; ciprofloxacin, 4/4/19; gentamicin, 25/2/5; imipenem, 0/0/0; and piperacillin-tazobactam, NA/10/10; and among Enterobacter spp. were: cefepime, NA/1/19; ceftazidime, 30/29/30; ceftriaxone, NA/30/36; ciprofloxacin, 3/3/15; gentamicin,18/0/0; imipenem, 0/0/5; and piperacilllin-tazobactam, NA/27/27. In conclusion, the species-related SRGA breakpoints detected Gram-negative isolates with decreased susceptibility in comparison with the native population with higher frequency than did the NCCLS breakpoints. The BSAC breakpoints for susceptible organisms were similar to NCCLS for ciprofloxacin and imipenem, and similar to SRGA for ceftazidime but lower than both NCCLS and SRGA for gentamicin, causing a much higher frequency of decreased susceptibility to gentamicin.

Health effects of vegetables and fruit: assessing mechanisms of action in human experimental studies

Epidemiologic data support the association between high intake of vegetables and fruits and low risk of chronic disease. There are several biologically plausible reasons why consumption of vegetables and fruit might slow or prevent the onset of chronic diseases. Vegetables and fruit are rich sources of a variety of nutrients, including vitamins, trace minerals, and dietary fiber, and many other classes of biologically active compounds. These phytochemicals can have complementary and overlapping mechanisms of action, including modulation of detoxification enzymes, stimulation of the immune system, reduction of platelet aggregation, modulation of cholesterol synthesis and hormone metabolism, reduction of blood pressure, and antioxidant, antibacterial, and antiviral effects. Although these effects have been examined primarily in animal and cell-culture models, experimental dietary studies in humans have also shown the capacity of vegetables and fruit and their constituents to modulate some of these potential disease-preventive mechanisms. The human studies have relied on intermediate endpoints related to disease risk. Design methodologies used include multiple-arm trials, randomized crossover studies, and more compromised designs such as nonrandomized crossovers and pre- and posttreatment analyses. Length of treatment ranged from a single dose to years depending on the mechanism of interest. Stringency of dietary control varied from addition of supplements to a habitual diet to provision of all food for the duration of a treatment. Rigorously conducted experimental dietary studies in humans are an important link between population- and laboratory-based research.

Molecular epidemiology of ceftazidime-resistant gram-negative bacilli on inanimate surfaces and their role in cross-transmission during nonoutbreak periods

We described the molecular epidemiology of expanded-spectrum cephalosporin-resistant gram-negative bacilli (RGN) recovered from inanimate surfaces. RGN were isolated from 9% of environmental cultures. Numerous species, each with multiple unique strains, were recovered. Epidemiological links between environmental, personnel, and patient strains suggested the exogenous acquisition of RGN from the hospital environment.

Colonization with broad-spectrum cephalosporin-resistant gram-negative bacilli in intensive care units during a nonoutbreak period: prevalence, risk factors, and rate of infection

OBJECTIVE

To define the epidemiology of broad-spectrum cephalosporin-resistant gram-negative bacilli in intensive care units (ICUs) during a nonoutbreak period, including the prevalence, the risk factors for colonization, the frequency of acquisition, and the rate of infection.

DESIGN

Prospective cohort study.

SETTING

Tertiary care hospital.

PATIENTS

Consecutive patients admitted to two surgical ICUs.

MAIN OUTCOME MEASUREMENTS

Serial patient surveillance cultures screened for ceftazidime (CAZ) resistance, antibiotic and hospital exposure, and infections.

RESULTS

Of the 333 patients enrolled, 60 (18%) were colonized with CAZ-resistant gram-negative bacilli (CAZ-RGN) at admission. Clinical cultures detected CAZ-RGN in only 5% (3/60) of these patients. By using logistic regression, CAZ-RGN colonization was associated with duration of exposure to cefazolin (odds ratio, 10.3; p < or = .006) and to broad-spectrum cephalosporins/penicillins (odds ratio, 2; p < or = .03), Acute Physiology and Chronic Health Evaluation III score (odds ratio, 1.2; p < or = .008), and previous hospitalization (odds ratio, 3.1; p < or = .006). Of the 100 patients who remained in the surgical ICU for > or = 3 days, 26% acquired a CAZ-RGN. Of the 14 infections caused by CAZ-RGN, 11 (79%) were attributable to the same species present in surveillance cultures at admission to the surgical ICU.

CONCLUSIONS

Colonization with CAZ-RGN was common and was usually not recognized by clinical cultures. Most patients colonized or infected with CAZ-RGN had positive surveillance cultures at the time of admission to the surgical ICU, suggesting that acquisition frequently occurred in other wards and institutions. Patients exposed to first-generation cephalosporins, as well as broad-spectrum cephalosporins/penicillins, were at high risk of colonization with CAZ-RGN. Empirical treatment of nosocomial gram-negative infections with broad-spectrum cephalosporins, especially in the critically ill patient, should be reconsidered.

High incidence of antibiotic resistance among bacteria in 4 intensive care units at a university hospital in Sweden

The frequency of antibiotic resistance among bacteria in 4 intensive care units (ICUs) at a university hospital in Sweden was investigated annually from 1993 to 1996. An increase in ampicillin-resistant enterococci from 1993 to 1995 was seen which was due to a shift from Enterococcus faecalis to Enterococcus faecium. After a special infection control programme was instituted, the rate of ampicillin resistance among enterococci and the number of E. faecium isolates declined during 1996. The oxacillin resistance rates for Staphylococcus aureus were < or = 2%, while most of the coagulase-negative staphylococci (CNS) were oxacillin resistant. No vancomycin-resistant enterococci or staphylococci were seen. The ciprofloxacin resistance rate for CNS and Enterococci spp. were high. Relatively, high levels of resistance to cefotaxime and piperacillin/tazobactam among Enterobacter spp. were also seen. During 1995 and 1996 Pseudomonas aeruginosa showed increasing resistance to ceftazidime, ciprofloxacin and piperacillin/tazobactam. This was due to an outbreak among rather few patients. The overall resistance rates for Gram-negative bacteria were low for aminoglycosides and imipenem. From 1993 to 1996 the total antibiotic consumption decreased by 27% in the whole hospital and 16.5% in the ICUs. However, the reduced antibiotic consumption was paralleled with a 23% decrease in the total number of patients treated in the hospital from 1993 to 1996. In contrast there was an 11.5% increase in the number of ICU patients treated during this period. The conclusion is that all ICUs within a hospital should have a programme for 'on-line' antibiotic resistance surveillance of drugs used in that unit in order to change the empiric treatment when there is an increase in antibiotic resistance. It is also important to survey the antibiotic consumption in the ICUs in order to avoid further selective pressure on bacteria showing increased resistance rates.

The molecular and clinical epidemiology of enterobacteriaceae-producing extended-spectrum beta-lactamase in a tertiary care hospital

To describe the epidemiology of Enterobacteriaceae-producing extended-spectrum beta-lactamase (EP-ESBL) in a non-outbreak setting, and to define the risk factors associated with colonization, a 5-month surveillance study was initiated. Ten of 333 patients were colonized with EP-ESBL, as defined by isoelectric focusing. Klebsiella sp. and Escherichia coli were the species most commonly harbouring these plasmid-mediated enzymes. Of the 16 SHV-producing isolates, 10 were SHV-3-like (pI 7.0) and six were SHV-5-like (pI 8.2). All isolates were resistant to ceftriaxone. Ceftazidime resistance was detected in 50% and 100% of SHV-3-like and SHV-5-like producing isolates, respectively. One patient was colonized with four different SHV-5-like producing Enterobacteriaceae. These isolates carried plasmids that were indistinguishable by restriction endonuclease analysis, indicating broad plasmid transfer within the patient. By logistic regression, haemodialysis was a strong risk factor for colonization with EP-ESBL, suggesting that, in our hospital, horizontal transmission is an important mechanism of dissemination of these resistant pathogens.

Patterns of antimicrobial use and antimicrobial resistance among healthy children in Bolivia

OBJECTIVE

To determine the incidence of antimicrobial-resistant, nonpathogenic Escherichia coli among healthy children aged 6-72 months in Camiri town and a rural village, Javillo, in south-eastern Bolivia.

METHOD

A community-based survey: stool samples were obtained from 296 healthy children selected by modified cluster sampling in Camiri and all 25 eligible children in Javillo. E. coli isolates were tested for antimicrobial susceptibility according to the standard disc diffusion method. By a questionnaire survey of 12 pharmacies and by using simulated patients, we investigated the antimicrobial availability and the usage patterns in Camiri town.

RESULTS

In Camiri, over 90%, and in Javillo over 70% of children carried E. coli resistant to ampicillin, trimethoprim-sulphamethoxazole (TMP/SMX) or tetracycline. Overall, 63% of children carried E. coli with multiple resistance to ampicillin, TMP/SMX, tetracycline and chloramphenicol. In the simulated patients study, antimicrobials were dispensed inappropriately for 92% of adults and 40% of children with watery diarrhoea, and were under-prescribed for males with urethral discharge (67%) or females with fever and dysuria (58%). The dose and/or duration of antimicrobials dispensed was almost always too low.

CONCLUSION

Our study showed a disturbingly high prevalence of carriage of nonpathogenic E. coli resistant to antimicrobials. The prevalence of resistance to ampicillin and TMP/SMX was higher than that previously reported in developing countries. The existence of a large reservoir of resistance genes in healthy individuals in developing countries represents a threat to the success of antimicrobial therapy throughout the world. Programmes to improve rational and effective drug use in developing countries are urgently needed.

Microbiologic activity of the newer macrolide antibiotics

In vitro susceptibility testing has demonstrated good activity of the azalide azithromycin and the macrolide clarithromycin against Gram-positive and -negative pathogens as well as atypical organisms involved in the etiology of upper and lower respiratory tract infections. One difference between these drugs in terms of their antimicrobial spectrum is the activity of azithromycin against Haemophilus influenzae. This organism is 2 to 8 times more susceptible in vitro to azithromycin than to clarithromycin or to erythromycin, the prototypical macrolide antibiotic. A principal concern in the management of respiratory tract infections today is the emergence of penicillin-resistant strains of Streptococcus pneumoniae. Both azithromycin and clarithromycin are active against penicillin-susceptible S. pneumoniae, although the activity of azithromycin is somewhat less than that of erythromycin and clarithromycin. Results of susceptibility testing of resistant organisms have varied among centers; in some areas all of the intermediately and some of the highly penicillin-resistant S. pneumoniae isolates are susceptible to the newer macrolides, whereas in other areas they are not. High tissue antibiotic concentrations achieved with these drugs may contribute to their effectiveness against some of the resistant S. pneumoniae isolates.

High frequency of antibiotic resistance among Gram-negative isolates in intensive care units at 10 Swedish hospitals

OBJECTIVE: To investigate the resistance rates among Gram-negative isolates in Swedish intensive care units (ICUs). METHODS: During 1994-95, members of the Swedish Study Group collected, on clinical indication, 502 consecutive initial isolates of Gram-negative bacteria from patients admitted to ICUs at 10 Swedish hospitals and performed minimal inhibitory concentration (MIC) determinations with the Etest. Breakpoints were defined according to the criteria of the Swedish Reference Group for Antibiotics (SRGA). RESULTS: The distribution of bacterial species was: Escherichia coli > Klebsiella spp. > Enterobacter spp. > Pseudomonas aeruginosa > Haemophilus spp. > Proteus spp. > Stenotrophomonas maltophilia > Citrobacter spp. > Acinetobacter > Pseudomonas spp. > Morganella morganii > Serratia spp. Together these constituted 97% of all isolates. The frequencies of resistance for all the initial Gram-negative isolates were: ceftazidime 6.8%, cefotaxime 14.9%, ceftriaxone 18.5%, cefuroxime 44.1%, ciprofloxacin 4.2%, co-trimoxazole 17.8%, gentamicin 5.8%, imipenem 8.6%, piperacillin 20.2%, piperacillin/tazobactam 12.9% and tobramycin 5.8%. CONCLUSIONS: Among Gram-negative isolates in Swedish ICUs, a very high frequency of resistance was seen to cefuroxime, and rather high frequencies of resistance to cefotaxime, ceftriaxone, piperacillin and piperacillin/tazobactam. These drugs cannot be recommended for further use as empirical monotherapy for severe ICU-acquired Gram-negative infections in ICUs in Sweden.

Risk factors for nosocomial infections caused by gram-negative bacilli. The Hellenic Antibiotic Resistance Study Group

Two hundred and ninety-nine Gram-negative hospital-acquired infections from 257 patients, consecutively identified during one month (November 1992) in five hospitals in the greater Athens area, were divided into four groups on the basis of the bacterium isolated: Group 1 (Escherichia coli group) included infections owing to E. coli, Group 2 (Proteus group) consisted of infections owing to Proteus spp. and Providencia spp., Group 3 (Kiebsiella/Enterobacter group) involved infections owing to Kiebsiella spp., Enterobacter spp., Citrobacter spp. and Serratia spp. Infections owing to Pseudomonas spp. and other non-fermenters were allocated into Group 4 (non-fermenters group). The four groups were studied in relation to risk factors including the duration of hospitalization, type of ward, underlying disease, history of operation, medical procedures/devices and antimicrobial therapy. A stepwise multiple logistic regression technique (SPSS Inc) was used to analyse the data, and the three groups (the Proteus group, the Klebsiella/Enterobacter group and the non-fermenters group) were analysed separately against the E. coli group. Infections with the Kiebsiella/Enterobacter group were associated with: (a) length of hospital stay before the infection, (b) treatment with newer antibiotics, and (c) hospitalization in an intensivecare unit (ICU). Infections with non-fermenters were associated with: (a) length of hospital stay before infection, (b) a urinary catheter, (c) type of disease (chronic infection being negatively associated), (d) treatment with newer antibiotics and (e) hospitalization in an ICU. Proteus group infections were associated with (a) length of hospital stay before infection, (b) treatment with newer antibiotics and (c) operation during present hospitalization (negative association). Interestingly, no specific hospitals were identified as risk factors. Identification of patients at risk for acquiring an infection owing to a nosocomial pathogen is vital in the development of a preventive strategy for hospital-acquired infections.