Biomedical subjects
Publications and source records attributed to F D Daschner.
A PCR identification of methicillin-resistant Staphylococcus aureus (MRSA), obviating the need for subculture on agar media, was investigated. The combination of MRSA detection by mecA femB PCR with prior enrichment in selective broth was tested for 439 swabs. PCR identified 36 MRSA-positive samples, in concordance with conventional methods.
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A sensitive and rapid HPLC-assay for determining the new oxazolidinone antibiotic linezolid in serum and urine is described. HPLC-integrated sample preparation permits the direct injection of serum and urine samples without any pre-treatment. The in-line extraction technique is realized by switching automatically from the extraction column to the analytical column. After the matrix has passed the extraction column the retained analyte will be quantitatively transferred to the analytical column where separation by isocratic HPLC will be performed. Linezolid is detected according to its absorption maximum at 260 nm. The quantification limits are estimated to be 0.3 and 0.5 microg/ml in serum and urine samples, respectively. The described procedure allows sample clean-up and determination of the antibiotic within 20 min, thereby facilitating drug-monitoring in clinical routine.
A sensitive and rapid HPLC assay for the determination of the beta-lactam antibiotics ceftazidime and meropenem in serum and bronchial secretions is described. HPLC-integrated sample preparation allows direct injection of serum samples without any pretreatment. Sputum samples need only a simple homogenisation and volume measurement but no liquefying reagents are necessary. The inline extraction technique is realized by automatically switching from the extraction column to the analytical column. After the matrix passed the extraction column, the retained analyte is quantitatively transferred to the analytical column where separation by isocratic HPLC is performed. Ceftazidime and meropenem are detected according to their absorption maxima at 258 and 296 nm, respectively. The detection limit of both antibiotics is estimated to be better than 0.5 microg/ml in serum as well as in sputum samples. The described procedure allows determination of the antibiotics within 30-45 min, thereby facilitating drug monitoring in clinical routine.
The authors outline the organization of infection control in Germany, focusing on official regulations, the training of infection control staff, and functions of the infection control committee and the availability of guidelines.
An infectious disease consulting service was set up at a large tertiary university hospital in 1996 to evaluate and to improve antibiotic prescription patterns. Treatment guidelines for the most common bacterial infections were implemented. On daily ward rounds antibiotic therapies without evidence of an infectious disease were stopped and inappropriate regimens were changed by an infectious disease specialist. During a 6-month prospective intervention period, 3,528 patients were studied on 13 wards of the department of internal medicine; 513 of these patients (14.5%) received antibiotic therapy. These treatment courses were evaluated as adequate in 394 cases (76.8%) and incorrect in 119 cases (23.2%). Inadequate antibiotic substances were chosen in 72 out of 119 cases (60.5%) and there was no indication for treatment in 38 out of 119 cases (32%). Pathogen-specific therapies were inadequate significantly more often than empirical antimicrobial therapies (p < 0.001). In addition, the duration of the perioperative prophylaxis could be limited to 1 d. Comparing the intervention period with a 3-month control interval without an infectious disease consulting service, a total of 31,510 Euro (including the costs for the infectious disease specialist) could be saved. No increase in infection-related mortality or length of stay was observed. These data show that an infectious disease consulting service optimizes antibiotic usage, and is cost-effective as a result of a significant cost reduction in hospitals, while not interfering with the quality of medical care.
This study compares the in vitro activity of novel fluoroquinolones against clinical Legionella pneumophila isolates. We determined both the MICs and intracellular efficacy of moxifloxacin, trovafloxacin, clinafloxacin and levofloxacin in the Mono Mac 6 infection model. Six legionella strains were tested and all proved highly susceptible to the fluoroquinolones. Clinafloxacin and trovafloxacin were found to have the lowest MICs (0.004 mg/L) followed by levofloxacin and moxifloxacin (0.015-0.03 mg/L). In the Mono Mac 6 infection model, inhibition of L. pneumophila was achieved at concentrations four times below the respective in vitro MICs. Concentrations as low as 0.015 mg/L of moxifloxacin and levofloxacin, 0.004 mg/L of trovafloxacin and 0.002 mg/L of clinafloxacin markedly decreased viable intracellular bacterial counts. These data strongly support further clinical evaluation of new fluoroquinolones for empirical treatment of lower respiratory tract infection including atypical pneumonia caused by L. pneumophila.
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Infection of the lower airways is a major problem in ventilated patients and contributes substantially to morbidity and mortality in the intensive care unit. The selective decontamination of the digestive tract and its effect on the reduction of the gram-negative colonisation rate in patients has been studied widely. However, the findings are inconsistent. Most studies describe an increase in resistant gram-negative bacterial strains and/or an increase in the occurrence of gram-positive strains following selective decontamination of the digestive tract. In light of the unresolved questions concerning the efficacy of selective decontamination of the digestive tract, it would seem that the resultant effect of this treatment on the bacterial flora should be an important consideration when assessing the value of such treatment. To date, none of the studies available for examination have been designed to adequately assess the effect of selective decontamination of the digestive tract on the bacterial flora.
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In hospitals, medical instruments are usually cleaned and disinfected in a washer/disinfector. However, it is not efficient for small hospitals or general practitioners to purchase such machines as they would not be working to capacity. We investigated the possibility of cleaning and disinfecting medical equipment in a conventional household dishwasher modified to achieve a temperature of 71 degrees C. For this purpose we contaminated screws with different test soils containing either bacterial (100 screws) or viral (106 screws) suspensions. Test organisms were re-isolated from 2% of the screws after bacterial contamination and 4.7% of those with viral contamination. In both cases we found dishwasher-processing to be a suitable means of disinfecting medical instruments.
It is a fundamental principle of continuous quality improvement (CQI) that processes should be the objects of quality improvement. The objective of this study was to improve process quality concerning the prevention of hospital-acquired infections in surgical departments and intensive care units by a continuous quality improvement (CQI) approach based mainly on quality circles. This approach was evaluated in a prospective controlled intervention study in medium-size acute care hospitals (four intervention and four control hospitals). During two intervention periods (each 10 months) four external physicians with training in hospital epidemiology and infection control introduced and supervised quality circles in the intervention hospitals. Process quality was assessed by interviewing senior staff members before the first and after the second intervention period using standardized questionnaires. The gold standard process quality was defined on the basis of the CDC/HICPAC-guidelines for the prevention of hospital-acquired infections. Most of the evaluated aspects of process quality belonged to the HICPAC-categories IA and IB respectively, the CDC category I. Fifty quality circle sessions were performed in the four intervention hospitals of which 28 were dealing directly with key subjects in infection control. In the intervention hospitals, 19.8% of evaluated aspects of process quality which concerned the prevention of hospital-acquired infections were improved compared to only 6.9% in the control hospitals (P<0.05). Sixty-six point seven percent of positive changes in process quality were initiated by the results of the quality circles. Our study demonstrates that a CQI approach based on infection control quality circles can lead to a substantial improvement of process quality regarding the prevention of hospital-acquired infections.
In early 1996 a hospital-wide methicillin-resistant Staphylococcus aureus (MRSA) epidemic was recognized in a 900-bed university hospital. In order to investigate hospital-specific transmission routes, a case-control study was carried out. Cases and controls were matched for age (+/- 10 years), sex, admission date (+/- 10 days) and clinical department on admission. Data on potential risk factors, were retrieved by chart review. Between June 1996 and February 1997, 67 patients with hospital-acquired MRSA were identified. Molecular typing showed that 85% of the cases carried an indistinguishable strain. The average time at risk for cases and controls was 17.3 and 23.7 days, respectively (P= 0.01). Seventeen patients (25.4%) developed infection. Conditional multivariate regression analysis showed that intensity of care (P= 0.002), number of transfers (P= 0.019), and fluoroquinolone therapy (P= 0.025) were independently associated with acquisition of MRSA. Intensity of care can be considered as a surrogate marker for a number of manipulations which represent the main risk factors for MRSA transmission. Frequent transfers within the hospital hinder, not only the epidemiological analyses, but also efforts to bring an outbreak under control. Our findings give epidemiological support to recent molecular studies which suggest that fluoroquinolone use may increase the transmissibility of MRSA in hospitals.
We investigated the antimicrobial efficacy of clinically meaningful, low concentrations of azithromycin against intracellular growth of two clinical isolates of Legionella pneumophila. The mature monocytic cell line Mono Mac 6 was used as a model to investigate the effects of antimicrobial agents on L. pneumophila. Extracellular susceptibility was determined by microdilution susceptibility testing in BYEalpha broth after 48 h of incubation. Mono Mac 6 cells infected with L. pneumophila were incubated with various concentrations of azithromycin. After 2 days of incubation, intracellular bacteria were released from the phagocytes and plated on to BCYEalpha agar. Addition of the intracellular-acting antibiotics azithromycin or ciprofloxacin at their MICs (0.5 and 0. 015 mg/L, respectively) resulted in a significant decrease in cfu, of up to approximately 1 log(10) after 48 h of incubation. In contrast, incubation of intraphagocytic L. pneumophila in the presence of antibiotics without intracellular activity (ceftizoxime, imipenem or amoxycillin-clavulanic acid) did not have any effect. Azithromycin inhibited intracellular replication at concentrations as low as 0.125 mg/L, approximately one-quarter of the extracellular MIC. The Mono Mac 6 cell line is a useful infection model for investigating the intracellular activity of antimicrobial agents in vitro. In accordance with clinical data and animal experiments, azithromycin and ciprofloxacin inhibited the intraphagocytic replication of L. pneumophila. In particular, azithromycin killed ingested legionellae in vitro at concentrations below the peak serum concentrations and below the MIC.
The increased incidence of nosocomial Legionnaires' disease in two hospitals prompted investigation of possible environmental sources. In the search for an effective DNA-typing technique for use in hospital epidemiology, the performance and convenience of three methods-SfiI macrorestriction analysis (MRA), amplified fragment length polymorphism (AFLP), and arbitrarily primed PCR (AP-PCR)-were compared. Twenty-nine outbreak-associated and eight nonassociated strains of Legionella pneumophila with 13 MRA types and subtypes were investigated. These strains comprised isolates from bronchoalveolar lavages, from environmental, patient-related sources, and type strains. All three typing methods detected one predominant genotype associated with the outbreaks in both hospitals. All of them correctly assigned epidemiologically associated, environmental isolates to their respective patient specimens. AP-PCR was the least discriminating and least reproducible technique. In contrast, AFLP was demonstrated as being the method with the best interassay reproducibility (90%) and concordance (94%) in comparison to the genotyping standard of MRA and the epidemiological data. Analysis of AFLP fragments revealed 12 different types and subtypes. Because of its simplicity and reproducibility, AFLP proved to be the most effective technique in outbreak investigation.
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In order to identify overall and site-specific nosocomial infection (NI) rates in patients receiving neurosurgical intensive care therapy, a prospective study was started in February 1997 in the eight-bed neurosurgical ICU of the University Hospital of Freiburg, Germany. Case records were reviewed twice a week, all microbiology reports were reviewed and ward staff was consulted. NI were defined according to the CDC-criteria and were categorised into specific infection sites. Within 20 months, 545 patients with a total of 5,117 patient days were investigated (mean length of stay: 9.4 days). 113 NI were identified in 90 patients (72 pts. with one, 13 with two and 5 with three infections, respectively). A moderate to high overall incidence (20.7/100 pts.) and a moderate incidence density (22.1/1,000 patient days) of NI in the neurosurgical ICU could be documented; these figures are well within the range of published data. Site specific incidence rates and incidence densities were: 1 bloodstream infection per 100 patients (0.9 central line-associated BSIs per 1,000 central line-days), 9 pneumonias per 100 patients (15.1 ventilator-associated pneumonias per 1,000 ventilator-days), 7.3 urinary tract infections per 100 patients (8.5 urinary catheter-associated UTIs per 1,000 urinary catheter-days). Additionally, 1.1 cases of meningitis, 0.7 brain abscesses/ventriculitis, and 1.7 other infections (surgical site infection, bronchitis, catheter related local infection, diarrhoea) were documented per 100 patients, respectively. 14.6% of isolated pathogens were E. coli, 10.2% enterococci, 9.6% S. aureus, 6.4% CNS, 6.4% Klebsiella spp., 5% Enterobacter spp. and 5% Pseudomonas spp. In 11 cases of NI no pathogen could be isolated.