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Objectives: The aim was to analyse the population pharmacokinetics of colistin and to explore the relationship between colistin exposure and time to death., Methods: Patients included in the AIDA randomized controlled trial were treated with colistin for severe infections caused by carbapenem-resistant Gram-negative bacteria. All subjects received a 9 million units (MU) loading dose, followed by a 4.5 MU twice daily maintenance dose, with dose reduction if creatinine clearance (CrCL) < 50 mL/min. Individual colistin exposures were estimated from the developed population pharmacokinetic model and an optimized two-sample per patient sampling design. Time to death was evaluated in a parametric survival analysis., Results: Out of 406 randomized patients, 349 contributed pharmacokinetic data. The median (90% range) colistin plasma concentration was 0.44 (0.14-1.59) mg/L at 15 minutes after the end of first infusion. In samples drawn 10 hr after a maintenance dose, concentrations were >2 mg/L in 94% (195/208) and 44% (38/87) of patients with CrCL ≤120 mL/min, and >120 mL/min, respectively. Colistin methanesulfonate sodium (CMS) and colistin clearances were strongly dependent on CrCL. High colistin exposure to MIC ratio was associated with increased hazard of death in the multivariate analysis (adjusted hazard ratio (95% CI): 1.07 (1.03-1.12)). Other significant predictors included SOFA score at baseline (HR 1.24 (1.19-1.30) per score increase), age and Acinetobacter or Pseudomonas as index pathogen., Discussion: The population pharmacokinetic model predicted that >90% of the patients had colistin concentrations >2 mg/L at steady state, but only 66% at 4 hr after start of treatment. High colistin exposure was associated with poor kidney function, and was not related to a prolonged survival., (Copyright © 2020 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Background: Amoxicillin has been in use since the 1970s; it is the most widely used penicillin both alone and in combination with the β-lactamase clavulanic acid., Objectives: In this narrative review, we re-examine the properties of oral amoxicillin and clavulanic acid and provide guidance on their use, with emphasis on the preferred use of amoxicillin alone., Sources: Published medical literature (MEDLINE database via Pubmed)., Content: While amoxicillin and clavulanic acid have similar half-lives, clavulanic acid is more protein bound and even less heat stable than amoxicillin, with primarily hepatic metabolism. It is also more strongly associated with gastrointestinal side effects, including Clostridium difficile infection, and, thus, in oral combination formulations, limits the maximum daily dose of amoxicillin that can be given. The first ratio for an amoxicillin-clavulanic acid combination was set at 4:1 due to clavulanic acid's high affinity for β-lactamases; ratios of 2:1, 7:1, 14:1 and 16:1 are currently available in various regions. Comparative effectiveness data for the different ratios are scarce. Amoxicillin-clavulanic acid is often used as empiric therapy for many of the World Health Organization's Priority Infectious Syndromes in adults and children, leading to extensive consumption, when some of these syndromes could be handled with a delayed antibiotic prescription approach or amoxicillin alone., Implications: Using available epidemiological and pharmacokinetic data, we provide guidance on indications for amoxicillin versus amoxicillin-clavulanic acid and on optimal oral administration, including choice of combination ratio. More data are needed, particularly on heat stability, pharmacodynamic effects and emergence of resistance in 'real-world' clinical settings., (Copyright © 2019 European Society of Clinical Microbiology and Infectious Diseases. Published by Elsevier Ltd. All rights reserved.)

Objectives: The rise in carbapenem resistance among Gram-negative bacteria has renewed interest in colistin. Recently, the EUCAST-CLSI Polymyxin Breakpoints Working Group declared that broth microdilution (BMD) is the only valid method for colistin susceptibility testing. BMD is not easily incorporated into the routine work of clinical laboratories, and usually this test is incorporated serially, resulting in delayed susceptibility reporting. We tested a strategy of combining VITEK ® 2 with a 2 μg/mL colistin agar dilution (VITEK ® 2/AD) screening plate to improve performance and time to reporting of colistin susceptibility., Methods: Colistin susceptibility for 364 clinical isolates was determined by VITEK ® 2/AD and compared with the reference standard BMD according to the ISO 20776-1:2007 and CLSI guidelines. The EUCAST colistin susceptibility breakpoint of ≤2 μg/mL was used. Escherichia coli NCTC 13846 served as quality control strain. Agreement, very major error (VME) and major error rates were determined using ISO 20776-2:2007., Results: The VME rate for VITEK ® 2 alone was 30.6% (15/49, 95% CI 18.3-45.4%), and was reduced to 10.2% (5/49, 95% CI 3.4-22.2%) using the VITEK ® 2/AD combined testing. The combined testing had categorical agreement with BMD of 97% (354/364, 95% CI 95.0-98.7%), and a major error (ME) rate of 1.6% (5/315, 95% CI 0.5-3.7%). Using the combined testing, even against challenging strains, 349 (95.8%, 95% CI 93.3-97.7%) colistin susceptibility results could be reported, and only 15 isolates required further analysis by BMD., Discussion: Our method is simple to apply and allows rapid reporting of colistin susceptibility., (Copyright © 2018 European Society of Clinical Microbiology and Infectious Diseases. Published by Elsevier Ltd. All rights reserved.)

Background: The emergence of azole-resistant Aspergillus fumigatus isolates is a matter of significant concern in Europe, with countries reporting resistance rates (which can be as high as 30%) in hospitalized patients. Consequently, the treatment guidelines in The Netherlands, the country with the highest documented prevalence of azole-resistant A. fumigatus, has just been revised to now recommend initial therapy with combination therapy until the susceptibility pattern is known. Therefore, susceptibility testing of clinically relevant isolates has been strongly recommended in the ESCMID-EFISG aspergillosis guidelines. Furthermore, mixed azole-susceptible and azole-resistant (isogenic as well as non-isogenic) infections have been reported to occur, which implies that colonies of clinical cultures may harbour various phenotypes of azole susceptibility., Objectives: The EUCAST-AFST (European Committee on Antimicrobial Susceptibility Testing Subcommittee on Antifungal Susceptibility Testing) has released a new screening method document (E.Def 10.1) for the detection of azole-resistant A. fumigatus isolates and updated the QC tables for antifungal susceptibility testing with associated QC endpoints. This review described in detail how to perform the screening test., Sources: This "How to document" is based on the EUCAST azole agar screening method document E.Def 10.1 and the QC tables for antifungal susceptibility testing document, v 2.0 (available at http://www.eucast.org/ast&#95;of&#95;fungi/qcafsttables/) CONTENTS: The method is based on the inoculation of azole-containing and azole-free agars and visual determination of fungal growth after one and two days of incubation. It can easily be implemented in routine laboratories of clinical microbiology and has been validated for simultaneous testing of up to five A. fumigatus colonies using itraconazole and voriconazole (mandatory), and posaconazole (optional)., Implications: This easy-to-use screening procedure for the detection of azole resistance in clinical A. fumigatus isolates will allow rapid testing in the daily routine of the microbiology laboratory and thus facilitate earlier appropriate therapy., (Copyright © 2018 European Society of Clinical Microbiology and Infectious Diseases. Published by Elsevier Ltd. All rights reserved.)

Objectives: Rezafungin (CD101) is a new long-acting echinocandin allowing weekly dosing, currently undergoing phase-II clinical trials for invasive candidiasis. The aim of this study was to assess rezafungin's in vitro activity against the most frequent Candida species following the EUCAST methodology., Methods: The susceptibility of 2018 clinical Candida isolates was determined at four European laboratories. In parallel, six control strains were repeatedly tested. Wild-type upper limits (WT-ULs), defined as the MIC value where the wild-type distribution ends, were determined following the principles for EUCAST ECOFF-setting., Results: The lowest rezafungin MICs (geometric MIC (GM-MIC), MIC range (mg/L)) were observed for C. albicans (0.016, 0.002-0.125) and the highest for C. parapsilosis (1.657, 0.063->4). MICs for the remaining species were in between these values (GM-MICs 0.048-0.055). Visual and statistical WT-ULs were identical for C. glabrata (0.125), C. krusei (0.125), C. parapsilosis (4), and C. tropicalis (0.25). If adopting these WT-ULs for classification into WT and non-WT populations, 1/413 C. glabrata, 1/402 C. krusei, 1/398 C. parapsilosis, and 1/402 C. tropicalis isolates were categorized as non-WT, all of which derived from Laboratory 1. For C. albicans unexplained laboratory variation was observed (WT-UL: 0.063-0.125 in Laboratories 1 and 2 versus 0.016 in Laboratories 3 and 4). A similar systematic difference was observed comparing the MICs for the three C. albicans QC strains, specifically, obtained in Laboratories 1and 2 with those in Laboratories 3 and 4., Discussion: Rezafungin displayed species-specific activity similar to other echinocandins. Interlaboratory variation was observed for the most susceptible species C. albicans clinical and QC strains, an observation that warrants further investigation., (Copyright © 2018 European Society of Clinical Microbiology and Infectious Diseases. Published by Elsevier Ltd. All rights reserved.)

Objectives: Fosfomycin is increasingly being prescribed for treatment of uncomplicated urinary tract infections in an era of emerging drug resistance. Surprisingly, little is known of the urinary concentrations of fosfomycin and its interindividual variation after the standard single 3-g oral dose. We aimed to gain more insight into urinary fosfomycin pharmacokinetics to evaluate its effectiveness., Methods: Three grams of fosfomycin trometamol was administered to 40 healthy female volunteers with an estimated mean glomerular filtration rate of >90 mL/min/1.73m 2 . Urine samples were collected from every urination during 48 hours, and then twice daily for up to 7 days. Time, volume, and pH were recorded. Concentrations were quantified with UPLC-MS/MS. Effectiveness was evaluated based on urinary concentrations and the target MIC of E. coli, the most common uropathogen., Results: A high interindividual variability was found. Peak concentration was 1982.0 ± 1257.4 mg/L, urinary half-life 12.4 ± 5.7 hours, and excretion rate over 48 hours 29.9 ± 7.1 mg/h. Recovery was 44.5 ± 12.6% after 48 hours and 47.0 ± 10.4% after 7 days. Concentrations remained above the EUCAST breakpoint of 32 mg/L in 100% of the volunteers over the first 24 hours, 67.5% for 48 hours, and 30% for 72 hours. A high urinary output was associated with low urinary concentrations and consequently reduced time > MIC, AUC 0-7days /MIC, and C max /MIC values., Conclusions: Considerable interindividual variability observed in the pharmacokinetics of fosfomycin signifies a risk for inadequate drug exposure in a significant proportion of the population. The current dosing regimen should therefore be reevaluated., (Copyright © 2017 European Society of Clinical Microbiology and Infectious Diseases. Published by Elsevier Ltd. All rights reserved.)

Objectives: Nitrofurantoin has been used for the prevention of urinary tract infection (UTI) for over 60 years. We conducted a systematic review and meta-analysis to assess its efficacy and safety in the prophylaxis of UTI., Methods: We performed a systematic review of all controlled trials in humans assessing nitrofurantoin for UTI prophylaxis published from 1946 to 2015. We further reviewed population-level cohort studies evaluating nitrofurantoin's toxicity. Meta-analyses assessing efficacy and adverse events were conducted on controlled trials., Results: Twenty-six controlled trials including 3052 patients fulfilled entry criteria for the systematic review and meta-analysis on efficacy and toxicity, and 16 population-level cohort studies were identified for review of toxicity. Overall quality was poor, with all studies at increased risk for various biases. When compared with no prophylaxis, nitrofurantoin is effective in the prevention of UTI (risk ratio 0.38 in favour of nitrofurantoin, 95% CI 0.30-0.48). Its prophylactic efficacy is superior to that of methenamine hippurate and comparable to that of other antibacterials. Compared with patients receiving other antibacterials, those receiving nitrofurantoin had an increased risk of 2.24 (95% CI 1.77-2.83) for a non-severe adverse effect. In all controlled trials, only one patient experienced a severe adverse effect (interstitial pneumonia). Cohort studies reported severe adverse effect frequencies of 0.02-1.5 per 1000 nitrofurantoin users., Conclusions: Nitrofurantoin is effective in the prevention of UTI. Its use may be associated with increased non-severe adverse effects; severe adverse effects occur infrequently. The risk of severe toxicity seems to increase with the duration of nitrofurantoin prophylaxis., (Copyright © 2016 European Society of Clinical Microbiology and Infectious Diseases. Published by Elsevier Ltd. All rights reserved.)

Objectives: Given the increasing number of antifungal drugs and the emergence of resistant Aspergillus isolates, objective, automated and high-throughput antifungal susceptibility testing is important. The EUCAST E.Def 9.3 reference method for MIC determination of Aspergillus species relies on visual reading. Spectrophotometric reading was not adopted because of concern that non-uniform filamentous growth might lead to unreliable and non-reproducible results. We therefore evaluated spectrophotometric reading for the determination of MICs of antifungal azoles against Aspergillus fumigatus., Methods: Eighty-eight clinical isolates of A. fumigatus were tested against four medical azoles (posaconazole, voriconazole, itraconazole, isavuconazole) and one agricultural azole (tebuconazole) with EUCAST E.Def 9.3. The visually determined MICs (complete inhibition of growth) were compared with spectrophotometrically determined MICs and essential (±1 twofold dilution) and categorical (susceptible/intermediate/resistant or wild-type/non-wild-type) agreement was calculated. Spectrophotometric data were analysed with regression analysis using the E max model, and the effective concentration corresponding to 5% (EC 5 ) was estimated., Results: Using the 5% cut-off, high essential (92%-97%) and categorical (93%-99%) agreement (<6% errors) was found between spectrophotometric and visual MICs. The EC 5 also correlated with the visually determined MICs with an essential agreement of 83%-96% and a categorical agreement of 90%-100% (<5% errors)., Conclusions: Spectrophotometric determination of MICs of antifungal drugs may increase objectivity, and allow automation and high-throughput of EUCAST E.Def 9.3 antifungal susceptibility testing of Aspergillus species., (Copyright © 2016 European Society of Clinical Microbiology and Infectious Diseases. Published by Elsevier Ltd. All rights reserved.)

The Subcommittee on Antifungal Susceptibility Testing (AFST) of the ESCMID European Committee for Antimicrobial Susceptibility Testing (EUCAST) has determined breakpoints for isavuconazole and Aspergillus and for itraconazole and Candida spp., released a new document summarizing existing and new minimum inhibitory concentration ranges for quality control strains and revised the method documents for yeast and mould susceptibility testing. This technical note is based on the EUCAST isavuconazole and itraconazole rationale documents, version 1.0 of the routine and extended internal quality control for antifungal susceptibility testing as recommended by EUCAST, and the E.Def 7.3, E.Def 9.2 and E.Def 9.3 method documents (http://www.eucast.org)., (Copyright © 2016 European Society of Clinical Microbiology and Infectious Diseases. Published by Elsevier Ltd. All rights reserved.)

Because of the increase in bacterial resistance to commonly used antibacterial drugs, old antibiotics are being 'revived' and, once again, are attracting interest. Many of these old antibiotics were approved long ago, in an era when there was no clear process for development, and requirements for efficacy to be demonstrated in rigorous clinical trials did not exist. At the time of these approvals, pharmacokinetic and pharmacodynamic principles were largely unknown, and did not inform the dose-finding process or recommendations for optimal usage. Indeed, the task of generating basic vital information for these old antibiotics remains to be performed. In this review, we provide a brief overview of the most essential data needed for dose justification and optimization. An overview of the shortage of data for selected old antibiotics illustrates the scope of the problem. In order to prevent harming patients with clinical decisions based on inadequate evidence, a redevelopment procedure for old antibiotics is urgently needed, including a regulatory framework., (Copyright © 2015 European Society of Clinical Microbiology and Infectious Diseases. Published by Elsevier Ltd. All rights reserved.)

EUCAST expert rules have been developed to assist clinical microbiologists and describe actions to be taken in response to specific antimicrobial susceptibility test results. They include recommendations on reporting, such as inferring susceptibility to other agents from results with one, suppression of results that may be inappropriate, and editing of results from susceptible to intermediate or resistant or from intermediate to resistant on the basis of an inferred resistance mechanism. They are based on current clinical and/or microbiological evidence. EUCAST expert rules also include intrinsic resistance phenotypes and exceptional resistance phenotypes, which have not yet been reported or are very rare. The applicability of EUCAST expert rules depends on the MIC breakpoints used to define the rules. Setting appropriate clinical breakpoints, based on treating patients and not on the detection of resistance mechanisms, may lead to modification of some expert rules in the future., (© 2011 The Authors. Clinical Microbiology and Infection © 2011 European Society of Clinical Microbiology and Infectious Diseases.)

Clinical breakpoints are used in clinical microbiology laboratories to categorize microorganisms as clinically susceptible (S), intermediate (I) or resistant (R) dependent on the quantitative antimicrobial susceptibility as indicated by the MIC value determined in a well-defined standard test system. The laboratory report, with the designations of S, I or R for each antimicrobial agent, provides guidance to clinicians with respect to the potential use of agents in the treatment of patients, and clinical breakpoints should therefore distinguish between patients that are likely or unlikely to respond to antimicrobial treatment. In Europe, clinical breakpoints are set by the European Committee on Antimicrobial Susceptibility Testing (EUCAST), following a defined procedure. This includes evaluation of efficacy in experimental settings and clinical studies to derive pharmacodynamic targets such as the fAUC/MIC ratio or %fT > MIC required for efficacy, the pharmacokinetic properties of the agent, Monte Carlo simulations to estimate exposures of the antimicrobial agent in the target patient population and commonly used dosing regimens. The probability of target attainment is subsequently determined for a range of pharmacodynamic targets and the results from the Monte Carlo simulations. The breakpoints derived are subsequently evaluated with respect to the wild-type population of the target microorganisms, specific resistance mechanisms and other relevant data. In this paper, we provide an overview of the EUCAST process and considerations for setting pharmacokinetic/pharmacodynamic breakpoints. These are the breakpoints that in the EUCAST breakpoint tables are referred to as 'non-species-related breakpoints'., (© 2011 The Authors. Clinical Microbiology and Infection © 2011 European Society of Clinical Microbiology and Infectious Diseases.)

Ceftazidime and cefotaxime are beta-lactam antibiotics with dose-related affinities for penicillin-binding protein (PBP)-3 and PBP-1. At low concentrations, these antibiotics inhibit PBP-3, leading to filament formation. Filaments are long strands of non-dividing bacteria that contain enhanced quantities of endotoxin molecules. Higher concentrations of ceftazidime or cefotaxime cause inhibition of PBP-1, resulting in rapid bacterial lysis, which is associated with low endotoxin release. In the present study, 37 isolates of Escherichia coli, Klebsiella spp., Pseudomonas aeruginosa and Acinetobacter spp. were studied over a 4-h incubation period in the presence of eight concentrations of ceftazidime or cefotaxime. As resistance of Gram-negative bacteria is an emerging problem in clinical practice, 14 isolates of E. coli and Klebsiella pneumoniae that produced extended-spectrum beta-lactamases (ESBLs) were also investigated. Morphological changes after exposure to the beta-lactam antibiotics revealed recognisable patterns in various bacterial families, genera and isolates. In general, all isolates of Enterobacteriaceae produced filaments within a relatively small concentration range, with similar patterns for E. coli and K. pneumoniae. Pseudomonas and Acinetobacter spp. produced filaments in the presence of clinically-relevant concentrations of both antibiotics as high as 50 mg/L. In all genera, filament-producing capacity was clearly related to the MIC. Ceftazidime induced filament production in more isolates and over wider concentration ranges than did cefotaxime. Interestingly, ESBL-producing isolates were not protected against filament induction. The induction of filament production may lead to additional risks during empirical treatment of severe infections.

This study compared the in-vitro properties and in-vivo effects of Escherichia coli filaments, spheroplasts and normal cells in a murine thigh infection model. E. coli was exposed to ceftazidime, meropenem or saline to obtain filaments, spheroplasts or normal bacilli, which were then injected into neutropenic mice. After 24 h, morphology, CFUs, local and circulating endotoxin levels, cytokine levels and mortality were recorded, and correlations between bacterial and host parameters of infection were investigated. Filaments and spheroplasts contained more endotoxin/CFU than controls. Histological studies showed that morphologically altered bacteria changed into rod-shaped cells in the absence of antibiotics. Bacterial spread to the liver was significantly higher in mice challenged with rod-shaped cells, compared with antibiotic-exposed bacteria (p 0.007). Muscle endotoxin levels correlated significantly with circulating interleukin (IL)-6 and tumour necrosis factor (TNF)-alpha, and both pro-inflammatory cytokines were correlated significantly (p 0.011). Despite a tendency toward higher local and systemic concentrations of endotoxin in the filament group, inflammatory responses and survival did not differ between groups. It was concluded that morphologically altered bacteria contain more endotoxin and can regain a rod shape after withdrawal of antibiotics, while non-antibiotic-exposed bacteria show greater spread to the liver. There was a clear intra-individual relationship between local endotoxin, systemic endotoxin, TNF-alpha and IL-6 production, but these parameters did not differ among groups.

The main objectives of the European Committee on Antimicrobial Susceptibility Testing (EUCAST) are to harmonise breakpoints for antimicrobial agents in Europe, and to act as the breakpoint committee for the European Medicines Agency (EMEA) during the registration of new antimicrobial agents. Detailed EUCAST procedures for harmonising and setting breakpoints for antimicrobial agents are available on the EUCAST website. Beginning with the current issue, a series of EUCAST Technical Notes will be published in CMI, based on the rationale documents produced by EUCAST for each of the antimicrobial agents studied, with the aim of highlighting important background information underlying decisions on breakpoints made by EUCAST.

In total, 881 presumptive clinical isolates of Streptococcus pneumoniae collected from throughout The Netherlands were analysed to determine their mechanisms of macrolide resistance. Isolates were identified initially by participating laboratories using their own standard identification technique, followed by determination of MICs with Etests. Only 797 isolates were confirmed as pneumococci following bile-solubility tests, lytA PCR and 16S rRNA sequencing. Of these confirmed pneumococci, 59 (7.4%) isolates were macrolide-resistant. Analysis by PCR indicated that 34 (57.6%) isolates harboured only the erm(B) gene and 16 (27.1%) only the mef gene. Three (5.1%) isolates carried both erm(B) and mef, while six (10.2%) isolates were negative for both mechanisms. Of the six negative isolates, three had a mutation in the 23S rRNA gene, and three were negative for all mechanisms tested. No isolates with the erm(A) subclass erm(TR) gene were detected. Among the 19 mef-positive isolates, 14 (73.7%) carried the mef(A) gene, and only five (26.3%) carried the mef(E) gene. No linezolid cross-resistance or multiresistance (resistance to more than two classes of antibiotics) was observed.

Objective: To evaluate bacterial susceptibility to linezolid in the Netherlands in comparison with other antibiotics., Methods: Bacterial strains were isolated between September 1999 and January 2000 from patients presumed to require antibiotic treatment. The in vitro activity of 1226 strains from 34 participating laboratories was tested against linezolid, vancomycin, teicoplanin, oxacillin, penicillin, erythromycin, ampicillin and other antibiotics against enterococci, coagulase-negative staphylococci, Staphylococcus aureus and Streptococcus pneumoniae. Minimal inhibitory concentrations (MIC) were obtained with the E test on Mueller-Hinton agar: every laboratory included control strains. For vancomycin and teicoplanin only, brain-heart infusion agar and an inoculum of 2.0 McFarland was used for Staphylococcus aureus, coagulase-negative staphylococci and enterococci to support a better growth and clear recognition of hetero-resistant colonies., Results: The values of MIC90 for linezolid were 1.5, 0.75, 0.75 and 1 mg/L for Staphylococcus aureus, coagulase-negative staphylococci, Streptococcus pneumoniae and enterococci, respectively. Six enterococcal strains with decreased susceptibility against vancomycin or teicoplanin were identified as Enterococcus faecium, E. gallinarum and E. casseliflavus (two strains each) and they were found to harbor vanA, vanC1 and vanC2/3 genes, respectively. Nine per cent of Streptococcus pneumoniae (an increase from 1% 4 years ago) showed decreased susceptibility to erythromycin, of both the ermB and mefE type; there was no cross-resistance with linezolid. Twelve coagulase-negative staphylococcal strains were resistant to teicoplanin., Conclusion: Linezolid is a promising drug in the treatment of infections caused by Gram-positive cocci. Cross-resistance with other antibiotics tested was not found.

Background: The unexpected conversion to HBsAg seropositivity of three cardiac allograft recipients prompted us to conduct a multidisciplinary study to identify the source, transmission mode, and extent of the hepatitis B virus (HBV) infection among the 256 cardiac allograft recipients of our hospital., Methods: All recipients were retrospectively screened for serum markers of HBV infection. A selected genomic region defining subtypes of the viruses involved was amplified and sequenced. An epidemiologic case-control study for possible risk factors was conducted to identify the mode of transmission., Results: Eighteen additional HBV-infected patients were identified, none of whom had shown symptoms of HBV infection. The involvement of one virus (subtype ayw 3) was shown in 20 of the 21 HBV-infected patients. This virus is found in less than 10% of HBV-infected individuals in The Netherlands. The demonstration of a common source of infection, combined with results of the epidemiologic study, identified posttransplantation endomyocardial biopsy procedures as the most likely mode of transmission. However, we also found evidence of secondary virus transmission by cardiac catheterization procedures to nonallograft recipients., Conclusions: The immunosuppressive therapy practiced in these patients to prevent allograft rejection may have not only facilitated virus transmission by causing high levels of viremia but also left the spreading of HBV undetected by causing a subclinical course of the infection. These findings stress the necessity of strict hygienic precautions during intravascular diagnostic procedures and indicate that vaccination against and routine monitoring for certain bloodborne infections in cardiac allograft recipients should be considered.

The molecular epidemiology of Pseudomonas aeruginosa infection in cystic fibrosis (CF) siblings was analysed by DNA fingerprinting using arbitrary primed polymerase chain reaction. A total of 306 strains collected from six pairs of siblings over a period of 20-126 months (median 64) was studied. Fifty-four different P. aeruginosa genotypes were recognized. Two out of six pairs of siblings were ultimately colonized by identical strains, and it was shown that a single P. aeruginosa clone can persist in an individual patient for over ten years. No overlap in P. aeruginosa genotypes was encountered between families, whereas in all families at least transient cross-colonization with the same genotype was observed. This finding demonstrates that P. aeruginosa cross-infection or acquisition of the same strain from an identical environmental source exists within the family situation, but does not always result in a long-term colonization by identical genotypes in all family members suffering from CF.