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* From the Pulmonary Division, St. Joseph’s Hospital and Medical Center (Drs. Theerthakarai, El-Halees, Ismail, and Solis), Paterson, NJ; and Seton Hall University, School of Graduate Medical Education (Dr. Khan), South Orange, NJ.
Correspondence to: M. Anees Khan, MD, FCCP, Chief, Pulmonary Division, St. Joseph’s Hospital and Medical Center, 703 Main St, Paterson, NJ 07503
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Abstract |
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 TOP Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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Design: A prospective study of 74 adult patients hospitalized with nonsevere CAP empirically treated according to the American Thoracic Society guidelines (ATS-GL) and evaluated with Gram’s stains and cultures of valid sputum specimens and blood cultures.
Setting: University-affiliated community hospital.
Results: Gram’s stain of a valid sputum specimen failed to identify the etiologic agent in all patients. Sputum cultures identified pathogens in only four patients (5%). The results of all blood cultures were negative. All patients responded to the initial empiric antibiotic coverage selected according to the ATS-GL, and the results of the initial MBS had no clinical impact.
Conclusion: The initial MBS, such as sputum Gram’s stains, sputum cultures, and blood cultures, have no value in the management of nonsevere CAP without comorbid factors.
Key Words: community-acquired pneumonia • microbiology • sputum culture • sputum Gram’s stain
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Introduction |
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TOPAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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A closer look at the studies recommending the use of sputum Gram’s stains and sputum cultures in the evaluation of CAP shows that the studied groups consisted of heterogeneous patients of all ages with a myriad of comorbid factors, including chronic obstructive lung disease, malignancy, diabetes mellitus, neurologic disease, and immune compromise.5 6 Additionally, complicated pneumonias, including necrotizing pneumonias, lung abscesses, pleural effusions, empyemas, and those with life-threatening infections and respiratory failure, also are included in these studies. Consequently, it seems inappropriate to extrapolate the results from such heterogeneous groups to those with simple (ie, uncomplicated) nonsevere CAP without associated comorbid factors.
In order to assess the value of the initial MBS (ie, sputum Gram’s stain, sputum culture, and blood culture) in the diagnosis and management of uncomplicated CAP without associated comorbid factors, we prospectively studied a group of 74 adult patients hospitalized with this diagnosis and managed according to the American Thoracic Society guidelines (ATS-GL),10 as regards empiric antibiotic coverage.
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Materials and Methods |
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TOPAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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65 years of age were excluded (Table 1
). Patients with complicated pneumonia
(ie, cavitary disease and pleural effusion), patients with
prior antibiotic use within 2 weeks before admission to the hospital,
and patients with severe pneumonia also were excluded (Table 1)
. Severe
CAP was defined according to the ATS-GL. Only those patients who
provided valid sputum specimens (ie, specimens with 20
neutrophils and < 10 squamous epithelial cells per low-power field)
were included in the study. The screening process thus yielded 74
patients for further analysis. Applying the ATS-GL criteria of severity
and the decision for hospitalization, these patients were further
subdivided into a group with clinically justifiable hospitalization and
another group in which hospitalization seemed unnecessary.
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20 neutrophils and < 10 squamous epithelial cells were
included in the study. Specimens thus screened were examined further
for bacteria and were cultured. The technique of sputum culture
consisted of the incubation of the remaining purulent portion of the
sputum specimen on chocolate agar for 48 h, on blood agar, and on
MacConkey agar. Chocolate agar was incubated in 5%
CO2 for the first 24 h. Blood cultures were
processed by conventional microbiological techniques. All chest
roentgenograms were examined by a radiologist, and the location and
extent of pneumonic infiltrates were documented. Empiric antibiotic
coverage was initiated after the sputum samples were collected. Empiric
antibiotic coverage on admission to the hospital consisted of a
macrolide with a second-generation or third-generation cephalosporin in
all patients, as recommended by the ATS-GL for the management of
hospitalized patients with CAP. |
Results |
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TOPAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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All patients experienced improvement in their symptoms within 48 h and became afebrile in 96 h, with improvement in the findings of their chest roentgenograms. No patient required a change in the empiric antibiotic coverage instituted on the day of admission.
All 74 valid sputum specimens (100%) showed mixed flora on Gram’s
stains without a predominant organism or an intracellular organism. Of
the 74 valid sputum samples cultured, 70 (95%) demonstrated normal
respiratory flora consisting of a few colonies of 
-streptococci,
-streptococci, Neisseria catarrhalis, and Lactobacillus.
Only four sputum cultures (5%) yielded the following pathogens:
Streptococcus pneumoniae, 1 patient (1%); Klebsiella
pneumoniae, 2 patients (3%); and Haemophilus
influenzae, 1 patient (1%). All blood cultures were devoid of
microbial growth.
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Discussion |
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TOPAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Studies recommending the use of sputum Gram’s stain and sputum culture in the initial evaluation of CAP generally consist of heterogeneous groups of patients of all ages with several comorbid factors.5 6 Boerner and Zwadyk,5 in a study of 89 patients with CAP, concluded that sputum Gram’s stain is a sensitive and reliable indicator with which to guide therapy and to predict outcome. The patient population in their study consisted of mostly elderly subjects with a high prevalence of alcoholism, smoking, malignant neoplasia, neurologic disease, and diabetes mellitus. Some had extensive infiltrates, cavitations, or pleural effusions demonstrated on the chest roentgenograms. Clearly, these patients were quite different from those with nonsevere and uncomplicated CAP who were younger and otherwise healthy. Another prospective study recommending the use of valid sputum Gram’s stain to guide the initial antibiotic therapy in CAP consisted of 59 bacteremic patients with a mean age of 65 years.6 Information regarding the severity of illness, the presence of other comorbid factors, or the extent of roentgenographic involvement was not provided. Bacteremia is a marker of severe illness and conceivably indicates a larger bacterial load in the patient’s lung and in the sputum. It would, therefore, seem inappropriate to extrapolate the results from these studies to those studies of patients with nonsevere CAP without comorbidity, who are the subject of our investigation.
Conversely, there have been several other reports the conclusions of which do not support the need for these MBS.7 8 9 10 11 12 Bates and coworkers,8 in a study of 52 patients with bacterial pneumonia of whom only 34 were able to produce sputum, found only 5 patients (9%) that yielded a pathogen. Similarly, Chalasani and coworkers,11 in a retrospective study of 517 patients with CAP, found that blood cultures did not have a significant impact on medical management. In another study of 184 patients with CAP without comorbid factors, even though 23% of sputum cultures and 11% of blood cultures yielded positive results among patients with nonsevere CAP, the authors did not endorse the use of MBS in the initial management of these patients.12
The striking finding in this study is that among 74 patients with CAP without comorbid factors, not a single sputum Gram’s stain or blood culture and only four sputum cultures (5%) yielded a pathogen. Such low yields from MBS cannot be ascribed to poor processing of the specimens or to suboptimal laboratory techniques of smear examination and culture, since similarly handled and processed specimens from other categories of patients with infectious disease show higher yields in the same laboratory. All sputum specimens were procured under the supervision of the medical residents and were transported to the laboratory and processed immediately. All microbiological procedures were conducted by qualified technicians, under the supervision of a microbiologist who was in charge of the hospital laboratory, with strict quality controls. Prior use of antibiotics as a cause of low yield also can be ruled out since patients with previous antibiotic use for 2 weeks prior to hospitalization were excluded from this study. The inclusion of relatively younger patients in this study may have skewed the etiology toward an atypical pathogen such as Mycoplasma, Chlamydia, or even Legionella, for which a sputum Gram’s stain, a sputum culture, and a blood culture obviously would be wasted endeavors. Therefore, it is logical to conclude that bacterial pneumonias in our patients escaped detection by the conventional MBS, including sputum Gram’s stain, sputum culture, and blood culture.
Applying the ATS-GL criteria for hospitalization, we found that 28% of our hospitalized patients with CAP could have been treated as outpatients. This is a consistent finding in almost all studies including the original pneumonia-severity index study by Fine et al.13 Patients with nonsevere, uncomplicated CAP without comorbid factors who are appropriate for outpatient therapy similarly can safely forgo MBS. These tests merely add an incremental cost to patient care without significant benefit.
Besides providing a low diagnostic yield in otherwise healthy patients with nonsevere CAP, these MBS do not affect the outcome when the initial antibiotic regimens are selected based on severity of illness and comorbid factors, as recommended by the ATS-GL. In the study of 184 patients hospitalized for CAP without comorbid factors by Sanyal and colleagues,12 when initial antibiotic selection was based on the ATS-GL, only 14% of patients did not respond. There was no difference in mortality between those nonresponders whose antibiotics were changed empirically and those with microbiologically guided changes.
In summary, our results indicate that the sputum Gram’s stains, sputum cultures, and blood cultures in patients with nonsevere CAP without comorbid factors do not provide diagnostically useful information, and they do not help in guiding initial therapy. Furthermore, these tests do not have any impact on the clinical outcome when the initial empiric antibiotic selection is based on a severity index, coexisting illness, and age, as recommended by the ATS-GL. These tests may be reserved for other categories of patients such as those excluded from our study. These conclusions obviously pertain only to a narrowly defined segment of patients with CAP and must not be applied to the management of patients with severe CAP or to those patients who have comorbid factors.
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Footnotes |
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Presented in part at the 1998 Annual Meeting of the American College of Physicians, San Diego, CA.
Received for publication February 4, 2000. Accepted for publication July 10, 2000.
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