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Bacterial Infections
Management of Bacteremic Community-acquired Pneumonia
a report by
Aydin Uzunpinar, MD and Mark L Metersky, MD
Division of Pulmonary and Critical Care, University of Connecticut School of Medicine
Streptococcus pneumoniae is the most commonly detected pathogen in Diagnosis
cases of community-acquired pneumonia (CAP). It is also responsible for up Clinical manifestations and epidemiological risk factors have not
to 60% of all cases of bacteremic CAP.
1
Although modern data are scarce, been useful in predicting the etiology of CAP in a given patient.
data accumulated in the pre-antibiotic era suggest that one in five cases Similarly, severity of illness is not a reliable predictor of bacteremic
of pneumococcal pneumonia is bacteremic.
2
In a review of 12 studies of pneumococcal pneumonia.
11
Urinary antigen testing appears to be a
hospitalized CAP patients,
3
blood cultures yielded a micro-organism in promising method for the diagnosis of pneumococcal pneumonia, since
330 of 2,935 patients (11%), 67% of which were S. pneumoniae. The it is rapid and simple and has >90% specificity.
12,13
The test may be
incidence of bacteremic pneumococcal pneumonia increases with age, especially helpful in patients who have received antimicrobial treatment
reaching about 60 cases per 100,000 in patients aged 80 years and over.
4
prior to blood cultures, since it remains positive after three days in 83%
of patients with documented pneumococcal bacteremia.
14
However, the
The advent of modern antibiotic treatments led to an initial dramatic clinical impact of S. pneumoniae urinary antigen testing or other tests
decrease in pneumococcal pneumonia mortality.
5,6
However, fatality rates that could help determine the presence of bacteremia at the initial
of bacteremic pneumococcal pneumonia have shown little improvement in presentation, such as DNA detection of S. pneumoniae in blood,
15
are not
the past three decades, remaining between 19 and 28%.
7–9
In fact, yet well defined.
S. pneumoniae is the most common cause of death in patients with CAP,
accounting for about two-thirds of all deaths.
10
The persistent high Since S. pneumoniae should always be addressed in empirical treatment
mortality can be explained partly by an increase in the number of elderly regimens, the performance of blood cultures has not been definitively
patients with comorbidities and immunosuppressed populations, including shown to improve outcomes.
16,17
Furthermore, false-positive blood culture
chemotherapy recipients and those with AIDS. It is also known that some results are associated with a longer hospital stay and more vancomycin
patients succumb to their infection before antibiotic treatment can change use for Gram-positive cocci, which in many cases later prove to be
the course of their illness, since the mortality rate from bacteremic S. coagulase-negative staphylococci.
18
These results suggest that targeting
pneumoniae pneumonia is highest in the first 48 hours of hospitalization.
6
the performance of blood cultures to patients with a higher likelihood of
In summary, bacteremic pneumococcal pneumonia continues to have bacteremia might lessen the frequency of these negative consequences.
significant clinical importance, and methods to improve outcomes have Therefore, there have been recent recommendations that depart from
been an area of intense debate. the long-standing practice of obtaining blood cultures from all patients
admitted to the hospital with pneumonia.
Aydin Uzunpinar, MD, is a Fellow in the Division of Pulmonary
Medicine and Critical Care at the University of Connecticut
The most recent CAP guidelines
19
suggest that blood cultures should not
School of Medicine. His clinical interests include severe be routinely performed on hospitalized patients with CAP, but
pneumonia, management of respiratory failure, and long-term
recommend them to be performed in patients with specific clinical
mechanical ventilation. Dr Uzunpinar is a graduate of the
Hacettepe Faculty of Medicine in Ankara, Turkey.
features that suggest a higher risk of bacteremia. These include a history
of asplenia, chronic liver disease, active alcohol use, cavitary infiltrates,
and pleural effusions on chest X-ray, and those with leukopenia and a
positive pneumococcal urinary antigen test. Blood cultures are also
Mark L Metersky, MD, is a Professor of Medicine in the
recommended for all patients admitted to intensive care units. Among
Division of Pulmonary and Critical Care at the University of
these patients with severe CAP, the overall yield of blood cultures is
Connecticut School of Medicine, where he is Director of the
higher and the possibility of identifying pathogens not included in the
Pulmonary/Critical Care Fellowship Program. He serves on
the Technical Expert Panel for the Centers for Medicare and
empirical antibiotic treatment is greater.
20–22
Medicaid Services National Pneumonia Project, is Past Chair
of the Chest Infections Network of the American College of
Antimicrobial Therapy
Chest Physicians (ACCP), is a member of the American
Thoracic Society, and is on the Executive Committee of
Recent literature focuses on two main issues with regard to appropriate
the Connecticut Thoracic Society.
antibiotic choices in the management of CAP that are also relevant to the
E: metersky@nso.uchc.edu
specific issue of bacteremic pneumonia: the relevance of drug resistance
in S. pneumoniae, and the value of combination therapy.
56 © TOUCH BRIEFINGS 2008
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