Chest
Volume 116, Issue 5, November 1999, Pages 1278-1281
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Clinical Investigations
INFECTION
The Impact of Blood Cultures on Antibiotic Therapy in Pneumococcal Pneumonia

https://doi.org/10.1378/chest.116.5.1278Get rights and content

Introduction

The cost-effectiveness of blood cultures in community-acquired pneumonia (CAP) has been questioned. Although penicillin-resistant Streptococcus pneumoniae is an increasing problem, penicillin therapy, where appropriate, reduces cost and may reduce antibiotic resistance. Blood cultures, however, can only reduce cost if physicians are prepared to alter therapy based on the results. We reviewed our experience to determine how often physicians changed management based on blood culture results positive for S pneumoniae.

Methods

Retrospective chart review was performed of all CAP admissions between January 1996 and December 1998 with blood culture results positive for S pneumoniae.

Results

Seventy-four patients out of 1,805 patients admitted with CAP during this period had pneumococcemia. Penicillin resistance was identified in 15 cases (20.3%; high grade in 4 cases) with cephalosporin resistance in 4 of these cases (1 high grade). Fifty-one patients had initial empiric therapy with a third-generation cephalosporin, and 58 patients had empiric coverage of atypical organisms; no patient received empiric penicillin therapy. Blood culture results altered management in 31 patients (41.9%), but in only 2 cases was this due to antibiotic resistance. Fifty-one patients without penicillin allergy grew penicillin-sensitive pneumococci; only 11 patients (21.6%) were changed to penicillin therapy. Thirteen of 35 patients (37.1%) who were given an additional antibiotic for atypical coverage had this antibiotic ceased.

Conclusion

Despite evidence of penicillin-sensitive pneumococcal CAP, physicians were reluctant to narrow antibiotic therapy, potentially adding to treatment cost and reducing the impact of blood culture results on management. The impact of penicillin resistance was reduced by the usual empiric choice of a third-generation cephalosporin. While positive blood culture results can clearly be useful in the management of patients with CAP, their cost-effectiveness needs to be assessed in prospective clinical trials.

Section snippets

Materials and Methods

The medical records of all patients admitted to Methodist Healthcare Central Hospital in Memphis between January 1996 and December 1998 with an admission diagnosis of CAP and at least one positive blood culture for S pneumoniae were retrospectively reviewed. In addition to demographic data, the initial antibiotic treatment, culture results, subsequent modification of treatment, complications, and outcome were recorded. Clinical data sufficient to calculate both the APACHE (acute physiology and

Results

During the review period, 1,805 patients were admitted with a diagnosis of CAP. Of 118 patients identified with positive blood culture results for S pneumoniae, 105 charts were available for review. Seventy-four of these patients (42 female and 32 male) were admitted for CAP; these comprised the study group. Nine of these patients (12.1%) reported a penicillin allergy. Sources of the pneumococcal septicemia in the other 31 patients were meningitis,8 infective endocarditis (2 patients), other (8

Discussion

Not only does the frequent indiscriminate use of broad-spectrum antibiotics increase the cost of treating CAP, it is also very likely a major factor in the growing problem of antibiotic resistance in many bacterial pathogens, particularly Gram-negative organisms such as Pseudomonas aeruginosa and Acinetobacter sp.10 Penicillin, when the pneumococcal strain identified is fully sensitive, is at least as efficacious as the higher-cost broader spectrum agents, such as third generation

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Dr. Waterer has been supported by a grant from the Methodist-Le Bonheur Healthcare Foundation and by the Athelstan and Amy Saw Medical Research Fellowship from the University of Western Australia.

For editorial comment see page 1153.

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