Ceftazidime therapy in patients with cystic fibrosis and multiply-drug-resistant pseudomonas

Outcome measures for airway clearance techniques in children with chronic obstructive lung diseases: a systematic review

BACKGROUND

Airway clearance techniques (ACTs) are an important aspect of the treatment of children with chronic obstructive lung diseases. Unfortunately, a sound evidence base is lacking and airway clearance strategies are largely based on clinical expertise. One of the reasons for the limited evidence is the lack of appropriate outcome measures specifically related to the effectiveness of ACTs. This review discusses all outcome measures applied in previous research in the pediatric population to provide a baseline for future studies.

DATA SOURCES

A systematic literature search was performed in PubMed, Web of Science and EMBASE databases. Search terms included chronic obstructive lung diseases and ACTs.

STUDY SELECTION

Studies were independently selected by the investigators according to the eligibility criteria. After screening, 49 articles remained for further analysis.

RESULTS AND CONCLUSIONS

Data are summarized according to the type of outcome measure. 48 (98%) studies performed pulmonary function tests, 19 (39%) assessed expectorated sputum, 10 (20%) parameters related to disease exacerbation, 8 (16%) oxygenation, 8 (16%) patient-reported outcomes, 5 (10%) exercise capacity and 5 (10%) applied imaging techniques. The synthesis of results showed a high discrepancy between studies due to differences in study design, population and the application of techniques. Since no 'gold standard' method could be identified, a combination of different outcome measures is recommended to gain a better understanding and to identify the potential effects of ACTs. An overview of important considerations has been provided to assist researchers in their choice of outcomes in future studies.

Clinical and in vitro evidence for the antimicrobial therapy in Burkholderia cepacia complex infections

Treatment of infections caused by Burkholderia cepacia complex (Bcc) in cystic fibrosis (CF) patients poses a complex problem. Bcc is multidrug-resistant due to innate and acquired mechanisms of resistance. As CF patients receive multiple courses of antibiotics, susceptibility patterns of strains from CF patients may differ from those noted in strains from non-CF patients. Thus, there was a need for assessing in vitro and clinical data to guide antimicrobial therapy in these patients. A systematic search of literature, followed by extraction and analysis of available information from human and in vitro studies was done. The results of the analysis are used to address various aspects like use of antimicrobials for pulmonary and non-pulmonary infections, use of combination versus monotherapy, early eradication, duration of therapy, route of administration, management of biofilms, development of resistance during therapy, pharmacokinetics-pharmacodynamics correlations, therapy in post-transplant patients and newer drugs in Bcc-infected CF patients.

Treatment of pulmonary exacerbations in adult cystic fibrosis patients: a review

Cystic fibrosis (CF) is a complex multisystemic disease requiring specialized care. It is characterized by progressive pulmonary decline, with intermittent worsening of lung function, often called pulmonary exacerbations. Eighty-five percent of all deaths from CF are a result of pulmonary disease, and pulmonary exacerbations are associated with decline in lung function. Treating pulmonary exacerbations requires a multifaceted approach and includes a multidisciplinary team composed of a physician, nurse, respiratory therapist, physical therapist, and nutritionist. Recently, the Cystic Fibrosis Foundation published guidelines addressing the comprehensive treatment of pulmonary exacerbations. This article outlines the treatment goals established by these guidelines, including the evaluation and treatment of comorbid conditions (eg, CF-related diabetes) and serious complications associated with CF exacerbations (eg, pneumothorax). Proper treatment of pulmonary exacerbations in CF patients will continue to improve their health and quality of life.

Population pharmacokinetic comparison and pharmacodynamic breakpoints of ceftazidime in cystic fibrosis patients and healthy volunteers

Despite the promising activity of ceftazidime against Pseudomonas aeruginosa and Burkholderia cepacia, there has not yet been a study that directly compared the pharmacokinetics (PK) of ceftazidime in cystic fibrosis (CF) patients and healthy volunteers by population PK methodology. We assessed the population PK and PK/pharmacodynamic (PD) breakpoints of ceftazidime in CF patients and healthy volunteers. Eight CF patients (total body weight [WT] [average +/- standard deviation] = 42.9 +/- 18.4 kg) and seven healthy volunteers (WT = 66.2 +/- 4.9 kg) received 2 g ceftazidime as a 5-min intravenous infusion. High-performance liquid chromatography (HPLC) was used for drug analysis, and NONMEM (results reported), S-ADAPT, and NPAG were used for parametric and nonparametric population PK modeling. We considered linear and allometric body size models to scale clearance and volume of distribution. Monte Carlo simulations were based on a target time of non-protein-bound plasma concentration of ceftazidime above MIC of > or =65%, which represents near-maximal killing. Unscaled total clearance was 19% lower in CF patients, and volume of distribution was 36% lower. Total clearance was 7.82 liters/h for CF patients and 6.68 liters/h for healthy volunteers with 53 kg fat-free mass. Allometric scaling by fat-free mass reduced the between-subject variability by 32% for clearance and by 18 to 26% for volume of both peripheral compartments compared to linear scaling by WT. A 30-min ceftazidime infusion of 2 g/70 kg WT every 8 h (q8h) achieved robust (> or =90%) probabilities of target attainment (PTAs) for MICs of < or =1 mg/liter in CF patients and < or =3 mg/liter in healthy volunteers. Alternative modes of administration achieved robust PTAs up to markedly higher MICs of < or =8 to 12 mg/liter in CF patients for 5-h infusions of 2 g/70 kg WT q8h and < or =12 mg/liter for continuous infusion of 6 g/70 kg WT daily.

Therapeutic options for Burkholderia cepacia infections beyond co-trimoxazole: a systematic review of the clinical evidence

Burkholderia cepacia complex (BCC) is an important group of pathogens affecting patients with cystic fibrosis and chronic granulomatous disease as well as immunocompromised and hospitalised patients. Therapeutic options are limited owing to high levels of resistance of the organism, either intrinsic or acquired, to many antimicrobial agents. Co-trimoxazole (trimethoprim/sulfamethoxazole) has been a drug of choice. However, in some cases it cannot be administered because of allergic or hypersensitivity reactions, intolerance or resistance. We systematically searched for relevant publications including clinical data in PubMed and Scopus. The search identified 48 relevant case reports (57 cases) and 8 cohort studies or trials. Nineteen (33.3%) of 57 patients included in the case reports received ceftazidime-based regimens, 14 (73.7%) of whom were cured. Meropenem was administered in seven patients (12.3%), one (14.3%) of whom improved and five (71.4%) were cured. Seven (12.3%) of 57 cases were treated with penicillins, four of which were piperacillin (all had a favourable outcome). Based on the data reported in the eight relevant cohort studies or trials identified, favourable outcomes were observed in 68.4% (26/38) to 100% (16/16) of cases treated with ceftazidime and 66.7% (6/9) of cases treated with meropenem. Also, 9/12 (75%) of patients receiving penicillins improved. Thus, Ceftazidime, meropenem and penicillins, mainly piperacillin, either alone or in combination with other antimicrobial agents, may be considered as alternative options for BCC infections, according to the in vitro antimicrobial susceptibility patterns and clinical results. However, the available clinical data are not sufficient and further clinical experience is required to clarify the appropriateness of these antibiotics for BCC infections.

Defining a pulmonary exacerbation in cystic fibrosis

OBJECTIVES

Despite the central importance of pulmonary exacerbations (PExs) as an outcome measure in cystic fibrosis clinical trials, no standardized definition of PEx exists. We conducted a prospective, multicenter study to establish a standardized PEx definition and score for use in clinical trials, based on clinical status rather than on treatment decisions.

STUDY DESIGN

Subjects were 246 patients enrolled in the placebo arm of a randomized, controlled trial of tobramycin for inhalation. Physician-investigators completed PEx questionnaires on all subjects at scheduled intervals during the 6-month study, indicating new or worsening symptoms, physical examination findings, and impression of PEx status (presence or absence and severity). Logistic regression was used to assess the relative importance of each of the characteristics in predicting a PEx.

RESULTS

We developed 2 PEx scores that use easily ascertained symptoms and chest examination findings; one also includes change in forced expiratory volume in 1 second over the preceding month. Both scores were sensitive and specific for predicting the presence of a PEx (sensitivity, 86%; specificity, 86%). The scores were validated in subjects in the intervention arm of the trial.

CONCLUSION

We hope that the proposed PEx score might serve as a standardized outcome measure for future clinical trials in cystic fibrosis, allowing meaningful comparisons of study results.

Aminoglycosides and renal magnesium homeostasis in humans

BACKGROUND

The use of aminoglycosides has been linked with hypomagnesaemia in scattered reports. The objective of the study was to measure prospectively the effect of treatment with the aminoglycoside amikacin on renal magnesium homeostasis.

METHODS

Twenty-four cystic fibrosis patients (aged 9-19 years) admitted because of exacerbation of pulmonary symptoms caused by Pseudomonas aeruginosa were treated with the aminoglycoside amikacin and the cephalosporin ceftazidime for 14 days. Renal values and plasma and urinary electrolytes were measured before and at the end of the systemic anti-pseudomonal therapy.

RESULTS

In the patients with cystic fibrosis, treatment with amikacin and ceftazidime did not modify plasma creatinine or urea and plasma or urinary sodium, potassium and calcium. Treatment with amikacin and ceftazidime significantly decreased both plasma total magnesium (from 0.77 (0. 74-0.81) to 0.73 (0.71-75) mmol/l; median and interquartile range) and ionized magnesium (from 0.53 (0.50-0.55) to 0.50 (0.47-0.52) mmol/l) concentration and increased fractional urinary magnesium excretion (from 0.0568 (0.0494-0.0716) to 0.0721 (0.0630-0.111)) and total urinary magnesium excretion (from 30.7 (26.5-38.0) to 38.5 (31. 5-49.0) micromol/l glomerular filtration rate).

CONCLUSIONS

The present study demonstrates that systemic therapy with amikacin plus ceftazidime causes mild hypomagnesaemia secondary to renal magnesium wasting even in the absence of a significant rise in circulating creatinine and urea.

A pilot study of the efficacy of constant-infusion ceftazidime in the treatment of endobronchial infections in adults with cystic fibrosis

STUDY OBJECTIVE

To compare the efficacy of constant-infusion ceftazidime (CTZ) with that of traditional intermittent dosing in a pilot trial.

DESIGN

Prospective, crossover trial.

SUBJECTS

Five adults with cystic fibrosis requiring intravenous antibiotic therapy for pulmonary exacerbations of the disease.

INTERVENTIONS

Patients were initially treated with standard CTZ 2 g 3 times/day for 10 days. At the next hospitalization patients were crossed over and CTZ was administered as a constant infusion at a rate determined to achieve a serum concentration 6.6 times the minimum inhibitory concentration (MIC) of the least susceptible Pseudomonas aeruginosa isolate.

MEASUREMENTS AND MAIN RESULTS

The pharmacokinetics of CTZ were determined, as were MICs for all P. aeruginosa isolates. Outcome parameters of interest were changes with therapy in white blood cell count, P aeruginosa density in sputum, and pulmonary function test results. Differences in these parameters for the two forms of administration were not significant. With the exception of one patient who received 6 g/day with both regimens, the average reduction in dosage with the constant infusion was 50%.

CONCLUSION

These preliminary data suggest that constant-infusion CTZ may be as safe and efficacious as intermittent dosing.

Comparison of the flutter device to standard chest physiotherapy in hospitalized patients with cystic fibrosis: a pilot study

STUDY OBJECTIVE

A preliminary study comparing the efficacy and safety of the flutter device (Flutter) to standard, manual chest physiotherapy (CPT) in hospitalized cystic fibrosis (CF) patients undergoing an acute pulmonary exacerbation.

DESIGN

Open label, comparative trial with alternate assignment.

SETTING

Community and childrens' hospital acute-care wards.

PARTICIPANTS

Twenty-two CF patients (ages 8 to 44 years) undergoing a total of 33 hospitalizations for acute pulmonary exacerbation.

INTERVENTIONS

Complete pulmonary function tests (PFTs) were done at baseline (admission), weekly, and upon discharge from the hospital. Clinical score (CS) was determined at the time of hospital admission and at discharge. Participants were assigned to receive supervised Flutter therapy or standard, manual CPT four times per day during the hospitalization. Patients were monitored for complications, including hemoptysis, hypoxemia, and pneumothorax.

RESULTS

The groups (CPT and Flutter) did not differ at baseline in demographics or Shwachman score, nor was length of hospitalization different. Significant improvements were noted from admission to discharge in CS and PFT results within each group. Mean percent change in CS and PFT results between CPT and Flutter groups showed no significant difference from hospital admission to discharge. Subsequent power analysis using the observed difference in percent change from admission to discharge for FEV1 indicated that to attain 80% power at alpha = 0.05, a sample of 219 subjects in each group would be necessary.

SUMMARY

Comparative trials of airway clearance techniques with sufficient sample size are lacking. Although the Flutter appears to be a useful device for independent, cost-effective, and safe administration of CPT in this pilot study, a much larger clinical trial would be necessary to make definitive conclusions.

Outcome measures for clinical trials in cystic fibrosis. Summary of a Cystic Fibrosis Foundation consensus conference

The CFF Consensus Conference concluded with a summary of those outcome measures that would be most useful in studies of patients 6 years of age and older and those measures that would be most useful in studies of the younger population (< 6 years of age) (Table). These measures were further divided into biologic markers most appropriate for initial (phase I and phase II) clinical trials and those especially useful in large, multicenter (phase III) pivotal trials. There is an ongoing need to improve the accuracy and validity of currently available measures of biologic activity and clinical efficacy in CF, especially in the younger population. The conference participants recommended that the following eight issues be addressed as soon as possible: (1) definition of pulmonary exacerbation, (2) broadly applicable methods of testing pulmonary function in small children (ideally a single test for all ages), (3) a comprehensive severity-of-disease score for young children, (4) reliable methods of quantifying chest x-ray and CT scan changes in young patients, (5) simple, inexpensive measures of lung inflammation, (6) a centralized, uniform approach to the establishment of data monitoring committees, (7) a quality of well-being scale for small children, and (8) reliable, reproducible aerosol delivery systems with defined characteristics. In addition, participants recommended that better methods be developed for assessing patients' adherence to research protocols.

Lack of unique ciprofloxacin pharmacokinetic characteristics in patients with cystic fibrosis

The single-dose pharmacokinetics of oral ciprofloxacin 750 mg were evaluated in six subjects with cystic fibrosis (CF subjects) and six age, sex and approximate weight-matched control subjects (controls). In addition, the effect of concurrently administered oral pancreatic enzyme replacement on the pharmacokinetics of ciprofloxacin was studied in 12 CF subjects. Ciprofloxacin t1/2, VSSF, CLF, and CLR in the matched CF subjects averaged 4.5 hours, 2.8 L/kg, 2.73 mL/min/kg and 5.7 mL/min/kg, respectively. Forty-two percent of the ciprofloxacin dose was excreted in the urine (0-48 hours) as the parent compound. No statistically significant differences in these ciprofloxacin pharmacokinetic parameter estimates were observed between CF and control subjects. In three CF subjects and two controls, the urinary excretion of ciprofloxacin and four of its metabolities were similar. In contrast, CF subjects demonstrated a prolonged tmax (2.3 versus 1.3 hours P less than .05) though ciprofloxacin Cmax was similar (4.7 versus 3.8 mg/L, NS). The concurrent administration of oral pancreatic enzyme replacement had no effect on the pharmacokinetics of ciprofloxacin. Apparent ciprofloxacin pharmacokinetic parameters in sputum were similar to those observed in serum. Sputum ciprofloxacin concentrations lagged behind serum concentrations but, on average, exceeded serum concentrations for 20 hours of the 24-hour sampling period. These sputum ciprofloxacin concentrations exceeded the reported MIC90 for Pseudomonas aeruginosa for approximately 15 hours. These data suggest an oral ciprofloxacin dose of 750 mg administered q8h to promote accumulation and maintenance of sputum drug concentrations well above pathogen MICs for the majority of a dosing interval in patients with CF.

Clinical pharmacology of antibiotics and other drugs in cystic fibrosis

The disposition of many drugs in cystic fibrosis is abnormal. In general, changes in pharmacokinetics include: increased volume of distribution, decreased plasma concentration, and enhanced renal and sometimes non-renal elimination of drugs. Pathophysiology of the disease important for drug disposition includes: (a) hypersecretion of gastric acid and duodenal secretions which are of small volume, viscous and low in bicarbonate; (b) increased intestinal permeability to some sugars and probe substances; (c) hypergammaglobulinaemia and sometimes hypoalbuminaemia; (d) significant elevation of free fatty palmitoleic acid level and decreased low-density and high-density serum lipoproteins; (e) an average increase by 30 to 45% in plasma volume in patients with cystic fibrosis who have moderately severe pulmonary disease, right ventricle hypertrophy and dilatation, which occurs in 15 to 35% of patients with a Shwachman score of 81 to 100; (f) abnormal bile acid metabolism and enterohepatic recirculation; and (g) enlarged kidneys and glomerulomegaly with increased glomerular filtration rate, tubular clearance and urine flow rate in some patients with cystic fibrosis. Delayed absorption from the gastrointestinal tract has been reported in patients with cystic fibrosis for cloxacillin, epicillin, clindamycin, ciprofloxacin and probably for cephalexin, para-aminobenzoic acid and chloramphenicol. A possible increased absorption was reported for cimetidine. Of 7 drugs studied only theophylline had significantly decreased plasma protein binding. An increased volume of distribution and increased renal clearance reported for several drugs is caused mainly by increases in plasma volume and urine flow rate in many of these patients. Possible increased elimination of some drugs in bile (which probably results from bile acid malabsorption) and in bronchial secretions (which are abundant in some cystic fibrosis patients with acute pulmonary infection) may explain enhanced non-renal elimination of these drugs. The metabolism of cimetidine in cystic fibrosis was reported not to be changed significantly compared to control subjects.

The epidemiology of Pseudomonas cepacia in patients with cystic fibrosis

Pseudomonas cepacia has emerged as an important nosocomial pathogen colonizing and infecting the respiratory tract of patients with cystic fibrosis (CF). Although assessment of outcomes associated with P. cepacia colonization has been difficult, controlled studies have shown that colonized patients experience more adverse outcomes compared with those not colonized. In the United States, an increasing trend in national incidence and prevalence of P. cepacia colonization has been shown, but cases have been unevenly distributed in a few centers. These estimates, however, may be biased by intercenter differences in laboratory methods for detecting P. cepacia in patient sputum. The source and mode of transmission of P. cepacia have not been adequately demonstrated, and may vary from center to center. Until further studies elucidate the epidemiology of P. cepacia in patients with CF, it may be prudent for CF centers to consider the use of selective media to isolate P. cepacia from sputa of patients with CF, to conduct investigations of clusters of P. cepacia-colonized patients, and to consider adopting infection control precautions recommended for control of multiply resistant gram negative organisms.

Randomized trial of ceftazidime versus placebo in the management of acute respiratory exacerbations in patients with cystic fibrosis

A randomized trial of ceftazidime versus placebo was conducted in patients with cystic fibrosis hospitalized for acute respiratory exacerbations. Patients 12 years of age or older were included if they had mild to moderately severe illness according to the following criteria: erythrocyte sedimentation rate less than or equal to 50 mm/hr and less than three other abnormalities (leukocyte count greater than or equal to 15,000/microliter, pulse greater than or equal to 100 beats/min, respirations greater than or equal to 30/min, or temperature greater than or equal to 38.5 degrees C). In all 16 episodes treated with ceftazidime, the patients were rated improved in comparison with 10 of 12 patients treated with placebo. Three placebo-treated patients dropped out of the study within 3 to 5 days because they wanted antibiotic therapy. None of the 15 placebo-treated patients showed clinical deterioration. There were no significant differences in rate of improvement of symptom score, weight gain, or pulmonary function between the two treatment groups. There was no difference in the course during the 6 to 24 months after the study period. Intravenous antibiotics are not essential in the management of all acute respiratory exacerbations of mild to moderate severity in patients with cystic fibrosis.

Mechanism of Pseudomonas aeruginosa persistence during treatment with broad-spectrum cephalosporins of lung infections in patients with cystic fibrosis

Beta-lactam resistance in Pseudomonas aeruginosa detected only during ceftazidime therapy of cystic fibrosis patients was studied. Evaluation of resistant and susceptible isolates from one patient and resistant laboratory derivatives indicated that elevated beta-lactamase levels were the primary determinant of resistance. Susceptible isolates outgrew resistant isolates on antibiotic-free medium.

Randomized double-blind evaluation of ceftazidime dose ranging in hospitalized patients with cystic fibrosis

Eighty-five patients with cystic fibrosis who were experiencing an acute infectious exacerbation of their disease were randomized in double-blind fashion to receive either 50 or 75 mg of ceftazidime per kg (body weight) per dose administered intravenously every 8 h for 14 days. Three patients were dropped from the study within 4 days of enrollment for reasons unrelated to drug administration. The total daily dose of ceftazidime administered was restricted by protocol design and was independent of the body weight of the patient. Thus, for datum analysis, patients were separated into three ceftazidime dosage groups (denoted as range of milligrams per kilogram per dose): group 1, 22 to 44.5; group 2, 46.3 to 56.6; and group 3, 66.7 to 80.6. Ceftazidime monotherapy had no effect on sputum colony counts for any Pseudomonas cepacia isolate. In contrast, a substantial reduction in Pseudomonas aeruginosa sputum colony counts was observed, and from 19 to 31% of isolates were suppressed greater than or equal to 10(5) CFU/ml after 14 days of therapy. Bacterial resistance in vitro was not observed, although a trend for increasing ceftazidime MICs was observed for group 1 patients (P less than 0.05). Overall, clinical response appeared independent of drug dose, and no relationship could be identified between the reduction in P. aeruginosa sputum colony counts and clinical outcome. Adverse effects of ceftazidime were mild and transient, necessitating drug discontinuation in one patient. These data suggest that the clinical response to ceftazidime in patients with cystic fibrosis may be maximal with 50 mg/kg per dose (150 mg/kg per day) up to a total daily dose of 6 g.

Therapeutic evaluation of piperacillin for acute pulmonary exacerbations in cystic fibrosis

The efficacy and pharmacokinetics of piperacillin monotherapy were studied in 46 patients with cystic fibrosis. Two patients were dropped from the study within 24 hr of enrollment because of drug-associated nausea and vomiting. Initially fourteen older patients (greater than 12 years) receiving piperacillin 450 mg/kg/day underwent a preliminary evaluation. Based on the results, 30 younger patients (less than or equal to 12 years) randomized in a double-blind fashion received either 600 or 900 mg/kg/day of piperacillin in six divided doses. Pharmacokinetic parameter estimates for t1/2 Vdss, and Cl were similar for first dose and steady-state evaluations. In 27 patients, approximately 43% of the administered dose was recovered in the urine after 4 hr. Piperacillin CiR averaged 49% of the total Cl. No difference in overall clinical efficacy could be identified between 600 and 900 mg/kg/day of piperacillin using two different objective scoring systems. Although a reduction in sputum Pseudomonas colony counts was greater following the 900 mg/kg/day regimen, this appeared to be independent of clinical effect. In 14 patients (32%), a distinct adverse serum-sicknesslike reaction was observed. The incidence of this reaction appeared to increase as the dose of piperacillin increased. All signs and symptoms of this reaction resolved within 36 hr of discontinuing piperacillin administration but recurred immediately on rechallenge in four patients. All patients with the adverse reaction were subsequently treated with beta-lactam antibodies without ill effect. Overall, clinical improvement appeared to be independent of the piperacillin dose. Our data support the use of total daily piperacillin dosages not exceeding 600 mg/kg.

Differences in drug susceptibility between isolates of Pseudomonas cepacia recovered from patients with cystic fibrosis and other sources and its relationship to beta-lactamase focusing pattern

Pseudomonas cepacia, a significant pulmonary pathogen among children with cystic fibrosis (CF), often possesses an inducible beta-lactamase. The beta-lactamase isoelectric focusing pattern and beta-lactam susceptibility of CF and non-CF isolates of P. cepacia were compared. Against all of the test strains, ceftazidime and piperacillin were more effective than aztreonam. More CF isolates were resistant to 8 micrograms/ml of ceftazidime than non-CF isolates. Isoelectric focusing of cefoxitin-induced, cell-free preparations of the CF isolates produced significantly more bands than comparable preparations of non-CF isolates. Organisms producing a beta-lactamase band that focused in the pH range of 8.5 to 8.7 were significantly more resistant to 8 micrograms/ml of ceftazidime than other isolates. The increased resistance of CF isolates of P. cepacia to ceftazidime may be the result of the production of a specific bacterial beta-lactamase.

Pseudomonas cepacia: biology, mechanisms of virulence, epidemiology

Pseudomonas cepacia, originally described as a plant pathogen, has emerged as an important cause of infection in altered hosts, particularly in the hospital setting. This organism's ability to survive and proliferate in a variety of solutions, medications, and even disinfectants and antiseptics has resulted in numerous clusters of common-source nosocomial infections. Many patients exposed to P. cepacia are merely colonized, but serious infections, including surgical and burn wound infections, bacteremia, meningitis, pneumonia, peritonitis, and urinary tract infections, are not rare. The virulence properties of this pathogen remain poorly characterized. Recently, P. cepacia has been reported in some cystic fibrosis centers as an increasingly frequent pulmonary pathogen. This trend has caused considerable concern because of reports of occasional cases of fulminant necrotizing pneumonia and bacteremia. Conversely, many patients with CF who become colonized with this organism have no ill effects. The epidemiology of P. cepacia in the CF population is unclear, but some patients probably acquire the organism from colonized siblings with CF. Circumstantial evidence suggests that the organism may also be acquired in the hospital. Treatment of infections is exceedingly difficult, particularly in patients with CF, because P. cepacia is resistant to a broad range of antibiotics.

Cephalosporin therapeutics in cystic fibrosis

Cephalosporins modified at the C-3 and C-7 positions of the cephem-nucleus have high antimicrobial activity and are safe. With evolution through first, second, and third generations, they have gained increasing gram-negative activity, but often at the expense of potency against gram-positive organisms. All third-generation cephalosporins have some intrinsic anti-Pseudomonas activity, indicating their potential benefit in the treatment of acute pulmonary exacerbations in patients with cystic fibrosis. Rational therapy in this clinical setting requires recognition of the pharmacodynamic and pharmacokinetic idiosyncrasies intrinsic to this patient population. When these priorities are recognized, only two of the available agents, cefsulodin and ceftazidime, appear to be of any therapeutic value. Both agents have been evaluated extensively in the treatment of acute pulmonary exacerbation in cystic fibrosis, and both have been found to be safe and effective.