C Wendt

Publications of C Wendt

• Survival of MRSA on sterile goods packaging.

  Authors: B Dietze, A Rath, C Wendt, H Martiny

  The Journal of hospital infection. 01/2002; 49(4):255-61.

  For many years, MRSA (methicillin-resistant Staphylococcus aureus) has been a world-wide problem. Stringent infection control regimens need to be followed to prevent spread. One such measure is theFor many years, MRSA (methicillin-resistant Staphylococcus aureus) has been a world-wide problem. Stringent infection control regimens need to be followed to prevent spread. One such measure is the disposal of unused, MRSA-contaminated single-use items, which is quite expensive. An alternative, less costly measure is to store these items temporarily, re-using them once the organism is non-viable. To establish survival times of MRSA on sterile goods packaging, paper and foil samples were contaminated with MRSA (approximately 10(8)-10(9) cfu/sample). The number of pathogens recoverable from the samples was measured at defined times. MRSA was demonstrated to survive on sterile goods packaging for more than 38 weeks. No MRSA was recoverable after 50 weeks. Temporary storage of MRSA-contaminated single-use items for such a long period of time is not an appropriate or reliable means of decontamination, but many be considered for items that would be costly to replace.

• Polyclonal bacteremia due to gram-negative rods.

  Authors: C Wendt, W J Grunwald

  Clinical infectious diseases : an official publication of the Infectious Diseases Society of America. 09/2001; 33(4):460-5.

  The frequency of, risk factors for, and outcome of polyclonal gram-negative bacteremia are still unknown. We investigated them in a prospective cohort study of patients for whom a blood cultureThe frequency of, risk factors for, and outcome of polyclonal gram-negative bacteremia are still unknown. We investigated them in a prospective cohort study of patients for whom a blood culture yielded >/=1 species of gram-negative aerobic rod. For each patient, pulsed field gel electrophoresis (PFGE) was performed on 4 colonies of each morphologic type. Episodes of bacteremia were considered polyclonal if caused by >1 PFGE type of the same species. Ten (6.5%) of 153 investigated patients had polyclonal bacteremia. Bacteremia due to nonfermenting rods was the single significant risk factor for polyclonal bacteremia. Complications were equally frequent in all patient groups. However, patients with polyclonal bacteremia received more extensive antibiotic therapy than did patients with monoclonal bacteremia. Nearly 20% of episodes of bacteremia due to nonfermenting rods were polyclonal, but it remains unclear why nonfermenting rods were more likely to cause polyclonal bacteremia than were other gram-negative rods.

• Genetic variability and prevalence of Bartonella henselae in cats in Berlin, Germany, and analysis of its genetic relatedness to a strain from Berlin that is pathogenic for humans.

  Authors: M Arvand, A J Klose, D Schwartz-Porsche, H Hahn, C Wendt

  Journal of clinical microbiology. 03/2001; 39(2):743-6.

  Nineteen Bartonella henselae strains and one Bartonella clarridgeiae strain were isolated from blood samples of 97 pet cats and 96 stray cats from Berlin, Germany, indicating prevalence rates of 1Nineteen Bartonella henselae strains and one Bartonella clarridgeiae strain were isolated from blood samples of 97 pet cats and 96 stray cats from Berlin, Germany, indicating prevalence rates of 1 and 18.7%, respectively, for B. henselae and 0 and 1%, respectively, for B. clarridgeiae. Eighteen of 19 B. henselae isolates corresponded to 16S rRNA type II. Pulsed-field gel electrophoresis (PFGE) analysis revealed seven different PFGE types among the feline B. henselae strains. Interestingly, all feline isolates displayed low genetic relatedness to B. henselae strain Berlin-1, which is pathogenic for humans.

• An outbreak of pyodermas among neonates caused by ultrasound gel contaminated with methicillin-susceptible Staphylococcus aureus.

  Authors: K Weist, C Wendt, L R Petersen, H Versmold, H Rüden

  Infection control and hospital epidemiology : the official journal of the Society of Hospital Epidemiologists of America. 01/2001; 21(12):761-4.

  OBJECTIVE: To investigate an outbreak of methicillin-susceptible Staphylococcus aureus (MSSA) infections in a neonatal clinic. DESIGN: Prospective chart review, environmental sampling, and genotypingOBJECTIVE: To investigate an outbreak of methicillin-susceptible Staphylococcus aureus (MSSA) infections in a neonatal clinic. DESIGN: Prospective chart review, environmental sampling, and genotyping by two independent methods: pulsed-field gel electrophoresis (PFGE) and randomly amplified polymorphic DNA polymerase chain reaction (RAPD-PCR). A case-control study was performed with 31 controls from the same clinic. SETTING: A German 1,350-bed tertiary-care teaching university hospital. RESULTS: There was a significant increase in the incidence of pyodermas with MSSA; 10 neonates in good physical condition with no infection immediately after birth developed pyodermas. A shared spatula and ultrasound gel were the only identified infection sources. The gel contained MSSA and was used for hip joint sonographies in all neonates. PFGE and RAPD-PCR patterns from 6 neonates and from the gel were indistinguishable and thus genetically related clones. The case-control study revealed no significant risk factor with the exception of cesarean section (P=.006). The attack rate by days of hip-joint sonography between April 15 and April 27, 1994, was 11.8% to 40%. CONCLUSIONS: Inappropriate hygienic measures in connection with lubricants during routine ultrasound scanning may lead to nosocomial S. aureus infections of the skin. To our knowledge this source of S. aureus infections has not previously been described.

• [Antibiotic susceptibility of Neisseria gonorrhoeae isolates in Berlin]

  Authors: J Wagner, B Tebbe, R Hörnle, M Chahin, M Arvand, C Wendt, C E Orfanos, H Hahn

  Der Hautarzt; Zeitschrift für Dermatologie, Venerologie, und verwandte Gebiete. 10/2000; 51(9):666-9.

  BACKGROUND AND OBJECTIVE: Because of the increasing resistance of Neisseria gonorrhoeae, we studied the actual resistance of isolates in Berlin. PATIENTS/METHODS: 85 Neisseria gonorrhoeae isolatesBACKGROUND AND OBJECTIVE: Because of the increasing resistance of Neisseria gonorrhoeae, we studied the actual resistance of isolates in Berlin. PATIENTS/METHODS: 85 Neisseria gonorrhoeae isolates were collected between 1995 and 1997. Susceptibility testing was performed for penicillin G, tetracycline, spectinomycin, ceftriaxone, ciprofloxacin and azithromycin by agar dilution. RESULTS: 18.8% isolates were resistant or intermediately resistant to penicillin G (including 6 PPNG). 12.9% isolates were resistant, 43.5% intermediately resistant to tetracycline. One strain was resistant against ciprofloxacin, 4 isolates showed increased MIC values (0.06-0.5 mg/l), whereas 78 isolates were fully susceptible (< 0.007 mg/l). All isolates were susceptible to spectinomycin, ceftriaxone, and azithromycin. CONCLUSIONS: Penicillin G and tetracycline should be given only in cases of proven sensibility. Resistance against ciprofloxacin may occur, especially in isolates acquired in south-east Asia. Ceftriaxone, spectinomycin and azithromycin were active against all isolates. The actual resistance situation should be monitored.

• Prevalence of colonization with vancomycin-resistant enterococci in various population groups in Berlin, Germany.

  Authors: C Wendt, C Krause, L U Xander, D Löffler, H Floss

  The Journal of hospital infection. 08/1999; 42(3):193-200.

  In order to prevent the spread of vancomycin-resistant enterococci (VRE), the epidemiology of this micro-organism must be defined. The prevalence of colonization with VRE in various population groupsIn order to prevent the spread of vancomycin-resistant enterococci (VRE), the epidemiology of this micro-organism must be defined. The prevalence of colonization with VRE in various population groups in Berlin was investigated and the risk factors associated with VRE colonization assessed. In a cross-sectional study, rectal swabs were taken from seven population groups (healthy students, outpatients, home nursing patients, normal care and critical care patients of a community hospital and university hospital). Every one completed a questionnaire (age, gender, previous hospital stays, antibiotic therapy). Rectal swabs were examined for the presence of normal gut flora and VRE. All VRE isolates were typed by pulsed-field gel electrophoresis (PFGE). VRE colonization prevalence ranged from 0.9% (students) to 4.2% (nursing-home patients) in non-hospitalized subjects; in hospitalized patients prevalence ranged from 1.8% (regular care ward of a community hospital) to 16.3% (ICU patients of a university hospital). Location (university hospital, OR = 3.5) and age (> or = 60 years, OR = 2.2) were independent risk factors for VRE colonization. Within one population group, isolates with identical PFGE patterns were found in up to three people; one strain was found in four subjects belonging to different groups. Our findings suggest that VRE are imported from the community into hospitals with subsequent spread within the institution.

• Validity of screening procedures for glycopeptide-resistant enterococci.

  Authors: C Wendt, C Krause, H Floss

  European journal of clinical microbiology & infectious diseases : official publication of the European Society of Clinical Microbiology. 07/1999; 18(6):422-7.

  Screening agars containing different vancomycin concentrations and different susceptibility testing procedures were compared to determine their validity for the detection of glycopeptide-resistantScreening agars containing different vancomycin concentrations and different susceptibility testing procedures were compared to determine their validity for the detection of glycopeptide-resistant enterococci (GRE). Direct streaking of rectal swabs over the surface of a commercially available agar (Enterococcosel; Becton Dickinson, Germany) containing 4 microg/ml and 16 microg/ml vancomycin was followed by incubation for 24 to 48 h. Susceptibility tests were done by microbroth dilution, disk diffusion, and the E test (AB Biodisk, Sweden). The microbroth dilution method according to National Committee for Clinical Laboratory Standards (NCCLS) was used as the gold standard for detection of GRE. Resistant and intermediately susceptible enterococcal isolates were differentiated to the species level. To detect resistance genes, the polymerase chain reaction was performed on all intermediately resistant isolates, on all isolates of VanB phenotype, and on 30% of isolates of VanA phenotype. Screening agar containing 4 microg/ml vancomycin displayed high sensitivity (97.6%) but only low specificity (35%) for the detection of GRE. Screening agar containing 16 microg/ml vancomycin had a high specificity of 89.3% and only a slightly lower sensitivity (92.7%) than the screening agar containing 4 microg/ml vancomycin. For the disk diffusion test, a breakpoint of < 16 mm yielded the optimal combination of sensitivity (98.8%) and specificity (99.6%). Both sensitivity and specificity of the E test for GRE detection were 100%. However, the E test is too expensive for testing of all enterococci. In conclusion, the combination of an inexpensive screening agar with either the E test or the disk diffusion test constitutes a valid and cost-effective method for the detection of GRE from screening specimens.

• Efficacy of hand disinfectants against vancomycin-resistant enterococci in vitro.

  Authors: G Kampf, M Höfer, C Wendt

  The Journal of hospital infection. 06/1999; 42(2):143-50.

  Vancomycin-resistant enterococci (VRE) may be spread within a hospital via the contaminated hands of the healthcare worker. Effective hand disinfectants are necessary to break chains of transmission.Vancomycin-resistant enterococci (VRE) may be spread within a hospital via the contaminated hands of the healthcare worker. Effective hand disinfectants are necessary to break chains of transmission. We determined the bactericidal activity of 1-propanol, chlorhexidine digluconate (0.5 and 4%). Sterillium (45% 2-propanol, 30% 1-propanol and 0.2% mecetronium etilsulphate), Skinsept F (70% 2-propanol, 0.5% chlorhexidine digluconate and 0.45% hydrogen peroxide) and Hibisol (70% 2-propanol and 0.5% chlorhexidine gluconate) against 11 clonally distinct enterococcal isolates in a quantitative suspension test. Four isolates were vancomycin susceptible, four were vanA and the remainder vanB positive. Eight isolates were identified as Enterococcus faecium, two as Enterococcus faecalis and one as Enterococcus gallinarum. The investigator was blinded to the species and the genotype. Four parallel experiments were carried out for each isolate, each preparation, each dilution and each reaction time. 1-Propanol (60%), Sterillium, Skinsept F and Hibisol were all highly bactericidal after 15 and 30 s against VRE and vancomycin-susceptible enterococci (VSE) with reduction factors (RF) > 6.4, even in dilution of 50% (v/v). No significant difference was observed between vanA isolates, vanB isolates and VSE. Chlorhexidine digluconate (0.5% and 4%) was found to be less bactericidal after 30, 60 and 300 sec (RF < or = 2.5). The vanB genotype isolates were found to be significantly more susceptible to chlorhexidine (0.5%) than the vanA isolates (60 sec; one-way ANOVA model; P = 0.05). After 300 sec the vanB genotype isolates were found to be significantly more susceptible to chlorhexidine (0.5%) than the other two genotype isolates (P = 0.016). The vanA isolates were found to be significantly more susceptible to chlorhexidine (4%) than the vanB isolates (300 s; P = 0.024). E. faecium was found to be less susceptible to chlorhexidine than E. faecalis at all concentrations and reaction times, but significant differences between RF were only observed at 60 sec for both chlorhexidine concentrations (P < 0.05; t-test for independent samples). Propanol is much more effective against enterococci than chlorhexidine and combination of the two may be useful in providing an immediate and long lasting effect.

• Recurrent gram-negative bacteremia: incidence and clinical patterns.

  Authors: C Wendt, S A Messer, R J Hollis, M A Pfaller, R P Wenzel, L A Herwaldt

  Clinical infectious diseases : an official publication of the Infectious Diseases Society of America. 04/1999; 28(3):611-7.

  Fifty-eight patients who had at least two episodes of gram-negative bacteremia were evaluated to define the epidemiology of recurrent bacteremia caused by these organisms. Thirty-two patients (55%)Fifty-eight patients who had at least two episodes of gram-negative bacteremia were evaluated to define the epidemiology of recurrent bacteremia caused by these organisms. Thirty-two patients (55%) had single relapses, 16 (28%) had one reinfection, and 10 (17%) had more than one recurrence of bacteremia. Intravenous catheters were the most common probable source of bacteremia. Relapses occurred earlier after the initial episode than did reinfections (58 days vs. 292 days; P = .002). The duration of antibiotic therapy for the first episode was shorter for patients with relapses than for those with reinfections (13.9 days vs. 17.5 days; P = .046). Microorganisms causing recurrent bacteremic episodes were not unusually resistant to antimicrobial agents. Reinfections may be difficult to prevent because they are associated with the severity of the underlying illness, which may not improve. The frequency of relapses might be reduced by increasing the duration of antibiotic therapy and eliminating foci of infection.

• Molecular epidemiology of gram-negative bacteremia.

  Authors: C Wendt, S A Messer, R J Hollis, M A Pfaller, R P Wenzel, L A Herwaldt

  Clinical infectious diseases : an official publication of the Infectious Diseases Society of America. 03/1999; 28(3):605-10.

  We did pulsed field gel electrophoresis (PFGE) and antibiotic susceptibility testing on 202 gram-negative isolates obtained from blood cultures between 1 January 1989 and 31 December 1993.We did pulsed field gel electrophoresis (PFGE) and antibiotic susceptibility testing on 202 gram-negative isolates obtained from blood cultures between 1 January 1989 and 31 December 1993. Seventy-eight patients had at least two gram-negative isolates of the same species recovered from blood drawn one or more days apart and met the other study criteria. Twenty patients had only 1 bloodstream infection, 48 patients had 1 recurrence of bacteremia, and 10 patients had > 1 recurrence of bacteremia. Of 80 recurrences of bacteremia, 52 (65%) were relapses and 28 (35%) were reinfections. Seventy-eight percent of the episodes of bacteremia occurring < or = 300 days apart were relapses, and 100% occurring > 300 days apart were reinfections (P < .001). Organisms causing recurrent bacteremia were not more resistant than those causing initial episodes. In conclusion, most episodes of recurrent gram-negative bacteremia were relapses. Relapses and reinfections could not be distinguished only by the length of time between episodes or by antimicrobial susceptibility patterns.

• Survival of vancomycin-resistant and vancomycin-susceptible enterococci on dry surfaces.

  Authors: C Wendt, B Wiesenthal, E Dietz, H Rüden

  Journal of clinical microbiology. 01/1999; 36(12):3734-6.

  We compared the abilities of Enterococcus faecium strains (three vancomycin-resistant enterococci [VRE] and five vancomycin-susceptible enterococci [VSE]) and Enterococcus faecalis strains (one VREWe compared the abilities of Enterococcus faecium strains (three vancomycin-resistant enterococci [VRE] and five vancomycin-susceptible enterococci [VSE]) and Enterococcus faecalis strains (one VRE and 10 VSE) to survive under dry conditions. Bacterial suspensions of the strains were inoculated onto polyvinyl chloride and stored under defined conditions for up to 16 weeks. All strains survived for at least 1 week, and two strains survived for 4 months. A statistical model was used to distribute the 19 resulting survival curves between two types of survival curves. The type of survival curve was not associated with the species (E. faecalis versus E. faecium), the source of isolation (patient versus environment), or the susceptibility to vancomycin (VRE versus VSE). Resistance to dry conditions may promote the transmissibility of a strain, but VRE have no advantages over VSE with respect to their ability to survive under dry conditions.

• Microbicidal activity of a new silver-containing polymer, SPI-ARGENT II.

  Authors: G Kampf, B Dietze, C Grosse-Siestrup, C Wendt, H Martiny

  Antimicrobial agents and chemotherapy. 10/1998; 42(9):2440-2.

  The survival of three bacterial species and Candida albicans was studied on SPI-ARGENT II. The immediate recovery from silver-impregnated polymer and control polymer (1 cm2) was approximately 10(6)The survival of three bacterial species and Candida albicans was studied on SPI-ARGENT II. The immediate recovery from silver-impregnated polymer and control polymer (1 cm2) was approximately 10(6) to 10(7) microorganisms. After incubation (37 degreesC) and neutralization of silver with horse serum (5%), surviving organisms were recovered. The survival of the microorganisms on the polymer was not found to be influenced by the silver implantation.

• Epidemiology of polyclonal gram-negative bacteremia.

  Authors: C Wendt, S A Messer, R J Hollis, M A Pfaller, L A Herwaldt

  Diagnostic microbiology and infectious disease. 10/1998; 32(1):9-13.

  Polyclonal bacteremic episodes are caused by more than one genotype of the same species. We conducted a study to estimate the frequency and to describe the epidemiology of polyclonal Gram-negativePolyclonal bacteremic episodes are caused by more than one genotype of the same species. We conducted a study to estimate the frequency and to describe the epidemiology of polyclonal Gram-negative bacteremia in our patient population. We reviewed the patients' medical records. We also did pulsed field gel electrophoresis on 66 Gram-negative isolates obtained from the 28 patients (29 episodes) who had more than one morphologically different isolate of the same Gram-negative species in a blood culture obtained between January 1, 1989 and December 31, 1993. Nine of 29 (31%) bacteremic episodes evaluated were polyclonal. The source of bacteremia was not significantly different among patients with polyclonal and monoclonal bacteremic episodes. Patients with polyclonal bacteremic episodes were younger and were more likely to have rapidly fatal diseases than were those with monoclonal bacteremic episodes; however, neither of these differences reached statistical significance. Patients with polyclonal bacteremic episodes were significantly more likely to have leukemia than were those with monoclonal bacteremic episodes (odds ratio = 18.67; 95% confidence interval, 1.92 to 255.80). Three of nine patients who had polyclonal bacteremia died compared with 2 of 19 patients who had monoclonal bacteremia (odds ratio = 4.25; 95% confidence interval, 0.41 to 50.80). Polyclonal Gram-negative bacteremia is more common than previously thought. Despite their younger age, patients with polyclonal bacteremic episodes were more likely to die than those with monoclonal bacteremic episodes. Thus, polyclonal bacteremia may be either an indicator or a risk factor for poor prognosis.

• Characterization of Bartonella henselae isolated from bacillary angiomatosis lesions in a human immunodeficiency virus-infected patient in Germany.

  Authors: M Arvand, C Wendt, T Regnath, R Ullrich, H Hahn

  Clinical infectious diseases : an official publication of the Infectious Diseases Society of America. 07/1998; 26(6):1296-9.

  Infections with Bartonella (Rochalimaea) henselae can result in a variety of clinical entities, including bacillary angiomatosis in immunocompromised hosts. The fastidious nature of this bacteriumInfections with Bartonella (Rochalimaea) henselae can result in a variety of clinical entities, including bacillary angiomatosis in immunocompromised hosts. The fastidious nature of this bacterium has so far prevented the culture of many clinical isolates. We report the recovery of the first European B. henselae isolate associated with bacillary angiomatosis. The isolate was cultured in a frozen skin biopsy specimen from a human immunodeficiency virus (HIV)-infected patient and was characterized by means of biochemical, bacteriologic, immunologic, and molecular biological methods including pulsed-field gel electrophoresis. This strain was compared with two B. henselae strains isolated in the United States to determine the relationship between the isolates. We found that it was phenotypically and genotypically indiscernible from B. henselae Houston-1, a blood culture isolate from an HIV-infected patient in Houston. These data suggest that one B. henselae clone is associated with human infections in Europe and the United States.

• Survival of Acinetobacter baumannii on dry surfaces.

  Authors: C Wendt, B Dietze, E Dietz, H Rüden

  Journal of clinical microbiology. 07/1997; 35(6):1394-7.

  Acinetobacter spp. have frequently been reported to be the causative agents of hospital outbreaks. The circumstances of some outbreaks demonstrated the long survival of Acinetobacter in a dry,Acinetobacter spp. have frequently been reported to be the causative agents of hospital outbreaks. The circumstances of some outbreaks demonstrated the long survival of Acinetobacter in a dry, inanimate environment. In laboratory experiments, we compared the abilities of five Acinetobacter baumannii strains, three Acinetobacter sp. strains from the American Type Culture Collection (ATCC), one Escherichia coli ATCC strain, and one Enterococcus faecium ATCC strain to survive under dry conditions. Bacterial solutions of the 10 strains were inoculated onto four different material samples (ceramic, polyvinyl chloride, rubber, and stainless steel) and stored under defined conditions. We investigated the bacterial counts of the material samples immediately after inoculation, after drying, and after 4 h, 1 day, and 1, 2, 4, 8, and 16 weeks of storage. A statistical model was used to distribute the 40 resulting curves among four types of survival curves. The type of survival curve was significantly associated with the bacterial strain but not with the material. The ability of the A. baumannii strains to survive under dry conditions varied greatly and correlated well with the source of the strain. Strains isolated from dry sources survived better than those isolated from wet sources. An outbreak strain that had caused hospital-acquired respiratory tract infections survived better than the strains from wet sources, but not as well as strains from dry sources. Resistance to dry conditions may promote the transmissibility of a strain, but it is not sufficient to make a strain an epidemic one. However, in the case of an outbreak, sources of Acinetobacter must be expected in the dry environment.

• Comparative evaluation of an automated ribotyping system versus pulsed-field gel electrophoresis for epidemiological typing of clinical isolates of Escherichia coli and Pseudomonas aeruginosa from patients with recurrent gram-negative bacteremia.

  Authors: M A Pfaller, C Wendt, R J Hollis, R P Wenzel, S J Fritschel, J J Neubauer, L A Herwaldt

  Diagnostic microbiology and infectious disease. 06/1996; 25(1):1-8.

  Ribotyping and macrorestriction analysis of chromosomal DNA using pulsed-field gel electrophoresis (PFGE) are among the more useful molecular epidemiologic typing methods. Because these techniquesRibotyping and macrorestriction analysis of chromosomal DNA using pulsed-field gel electrophoresis (PFGE) are among the more useful molecular epidemiologic typing methods. Because these techniques are labor intensive, automation of one or more steps may allow clinical laboratories to apply molecular typing methods. We compared the recently developed automated ribotyping system, the RiboPrinter Microbial Characterization System (DuPont), with PFGE as a means of typing clinical isolates of E. coli and P. aeruginosa. A total of 22 E. coli and 24 P. aeruginosa were typed by both PFGE and the RiboPrinter. When compared with PFGE typing of E. coli and P. aeruginosa, the RiboPrinter was less sensitive in identifying different strains, particularly among the isolates of P. aeruginosa. The RiboPrinter was completely automated and allowed up to 32 isolates to be typed within an 8-hour period. The pattern of results obtained in this study suggests that a heirarchical approach to molecular typing using the RiboPrinter Microbial Characterization System plus PFGE might be feasible. The RiboPrinter Microbial Characterization System promises to be a very useful addition to the expanding molecular typing armamentarium.

• [Field study to obtain Legionella-free water from showers and sinks of a transplantation unit by a system of water filters]

  Authors: C Wendt, K Weist, E Dietz, P Schlattmann, H Rüden

  Zentralblatt für Hygiene und Umweltmedizin = International journal of hygiene and environmental medicine. 04/1995; 196(6):515-31.

  The efficiency of filters for elimination of Legionella was examined in a ten month field study. Showers and sinks of twelve patient rooms were equipped with nylon 66-polyamid filters. BeforeThe efficiency of filters for elimination of Legionella was examined in a ten month field study. Showers and sinks of twelve patient rooms were equipped with nylon 66-polyamid filters. Before filtration the total number of colonies was very high with an arithmetical mean of 1131 cfu/ml. This could be reduced by filtration at the sinks (mean = 205 cfu/ml). After equipping showers with filters we found a significant increase in the total number of colonies (mean = 1961 cfu/ml). In non-filtered water we found Legionella in nearly 90% of the 648 samples, the concentration extended to 300 cfu/ml (mean = 51 cfu/ml). After filtration the concentration of Legionella was up to 280 cfu/ml in 7.3% of the 665 samples. We calculated a logistic regression model to examine the effects of the age of the filters and the duration of their use since the last sterilization. These parameters were calculated from the time of the break through or retrograde contamination with Legionella. There were clear differences between shower and sink filters. Assuming a 5% probability of break through or retrograde contamination with Legionella, the sink filters should be sterilized every 3 weeks without regards to the age of the filters. In contrast the shower filters may be used for 3 weeks if they are sterilized weekly. If weekly sterilization is not feasible they should be used for 2 weeks only. In our study it was not possible to achieve Legionella-free water by changing either the frequency of sterilization or the age of the filters.

• Comparative evaluation of an automated ribotyping system versus pulsed-field gel electrophoresis for epidemiological typing of clinical isolates of Escherichia coli and Pseudomonas aeruginosa from patients with recurrent gram-negative bacteremia

  Authors: M.A. Pfaller, C. Wendt, R.J. Hollis, R.P. Wenzel, S.J. Fritschel, J.J. Neubauer, L.A. Herwaldt

  Diagnostic Microbiology and Infectious Disease.

  Ribotyping and macrorestriction analysis of chromosomal DNA using pulsed-field gel electrophoresis (PFGE) are among the more useful molecular epidemiologic typing methods. Because these techniquesRibotyping and macrorestriction analysis of chromosomal DNA using pulsed-field gel electrophoresis (PFGE) are among the more useful molecular epidemiologic typing methods. Because these techniques are labor intensive, automation of one or more steps may allow clinical laboratories to apply molecular typing methods. We compared the recently developed automated ribotyping system, the RiboPrinter™ Microbial Characterization System (DuPont), with PFGE as a means of typing clinical isolates of E. coli and P. aeruginosa. A total of 22 E. coli and 24 P. aeruginosa were typed by both PFGE and the RiboPrinter™. When compared with PFGE typing of E. coli and P. aeruginosa, the RiboPrinter™ was less sensitive in identifying different strains, particularly among the isolates of P. aeruginosa. The RiboPrinter™ was completely automated and allowed up to 32 isolates to be typed within an 8-hour period. The pattern of results obtained in this study suggests that a hierarchical approach to molecular typing using the RiboPrinter™ Microbial Characterization System plus PFGE might be feasible. The RiboPrinter™ Microbial Characterization System promises to be a very useful addition to the expanding molecular typing armamentarium.