BACTERIOLOGICAL AND CLINICAL PROFILE OF COMMUNITY ACQUIRED PNEUMONIA IN HOSPITALIZED PATIENTS

The aim of our study was to obtain comprehensive insight into the bacteriological and clinical profile of community-acquired pneumonia requiring hospitalization. The patient population consisted of 100 patients admitted with the diagnosis of community-acquired pneumonia (CAP), as defined by British Thoracic society, from December 1998 to Dec 2000, at the Sher- i-Kashmir institute of Medical Sciences Soura, Srinagar, India. Gram negative organisms were the commonest cause (19/29), followed by gram positive (10/29). In 71 cases no etiological cause was obtained. Pseudomonas aeruginosa was the commonest pathogen (10/29), followed by Staphylococcus aureus (7/29), Escherichia coli (6/29), Klebsiella spp. (3/29), Streptococcus pyogenes (1/29), Streptococcus pneumoniae (1/29) and Acinetobacter spp. (1/29). Sputum was the most common etiological source of organism isolation (26) followed by blood (6), pleural fluid (3), and pus culture (1). Maximum number of patients presented with cough (99%), fever (95%), tachycardia (92%), pleuritic chest pain (75%), sputum production (65%) and leucocytosis (43%). The commonest predisposing factors were smoking (65%), COPD (57%), structural lung disease (21%), diabetes mellitus (13%), and decreased level of consciousness following seizure (eight per cent) and chronic alcoholism (one per cent). Fourteen patients, of whom, nine were males and five females, died. Staphylococcus aureus was the causative organism in four, Pseudomonas in two, Klebsiella in one, and no organism was isolated in seven cases. The factors predicting mortality at admission were - age over 62 years, history of COPD or smoking, hypotension, altered sensorium, respiratory failure, leucocytosis, and staphylococcus pneumonia and undetermined etiology. The overall rate of identification of microbial etiology of community-acquired pneumonia was 29%, which is very low, and if serological tests for legionella, mycoplasma and viruses are performed the diagnostic yield would definitely be better. This emphasizes the need for further studies (including the serological tests for Legionella, mycoplasma and viruses) to identify the microbial etiology of CAP.

The most common isolate from blood culture was Klebsiella pneumoniae 7 (6.8%) followed by Pseudomonas aeruginosa and E.coli 6 (5.8%) each. A total of 10 patients, 6 males and 4 females, died. The microbial etiology in 4 of the 10 patients who died during hospitalization could not be ascertained.

Discussion:
CAP still remains a major reason for admission and a common cause of death particularly in developed countries. With various epidemiological data world wide still an in-depth survey is lacking touching crucial aspects of CAP particularly in southern parts of the Indian subcontinent. The number of patients may also be under reported as CAP is not included as a notifiable disease, and local physicians often rely on 4 clinical presentation of the patient. In routine laboratory testing, fastidious organisms such as Chlamydia, Mycoplasma and Legionella species cannot be grown, unless special culture 5,6,7 8 media are used. A study by RC She et al claims that the recovery of Mycoplasma pneumoniae and Chlamydia pneumoniae in culture is low, hence only serology or molecular methods are good to clinch the diagnosis. Technically, the diagnosis of CAP is often cumbersome and often missed due to poor sample 9,10 quality, lack of history and the overall often low yield.
Here we discuss the diversity of this disease in comparison with studies within India and abroad. It could still be the tip of the iceberg phenomenon as population based studies although have been reported, there still remains very little information of outpatients being treated in other primary 11 health care centres or even by family physicians. The rural and semi-urban health facilities do not routinely advise radiographs and an empiric antibiotic therapy will invariably be started regardless of the etiology. Specialist services for microbiological diagnosis by culture and occasionally supported 12 by serology remains a rural health centres dream.
CAP is a triad of fever or chills and leukocytosis, signs or symptoms localized to the respiratory system ( cough, increased sputum production, shortness of breath, chest pain, or abnormal pulmonary examination ), and a new or changed infiltrate as observed on radiography usually accurately identifies a patient with CAP. Diagnosis of CAP in patients with lung cancer, pulmonary fibrosis, chronic infiltrative lung diseases or congestive heart failure can be challenging. An atypical presentation and pathogens also play a vital role in 13 misdiagnosis.
Time tested scoring systems are available to classify CAP patients requiring hospitalization or intensive care unit ( ICU ) care.14,15 Pneumonia Severity Index (PSI) 16 and CURB-65 score ( a measure of confusion, blood urea nitrogen, respiratory rate, 17 and blood pressure in a patient ≥ 65 years of age ), and certain guidelines by Infectious Diseases Society of America or the American Thoracic Society (IDSA/ATS) will enhance uniform 18,19 patient care.
In our study CAP was 34% when compared to studies by Bashir et al at 29%.1 and 47.7% and 75.6% in two north 20 21 Indian studies at Ludhiana and Shimla respectively. Most cases were in the 60-75 years age group as seen in earlier studies and in community based studies in Finland, where the 22 rate of CAP increased for each year of age over 50 years. The most common pre-disposing factor identified in our study 23 was diabetes mellitus in 25% but a study by Jindal et al showed it to be smoking. 30% of our cases did present with CAP triad apart from a few atypical presentations. In the diagnosis of pneumonia a good sputum sample or an induced sputum sample that satisfies the Bartlett scoring criteria is 25 essential to provide a vital clue to the causative organism.
During an influenza outbreak, the circulating influenza virus becomes the principal cause of CAP that is serious enough to require hospitalization, with secondary bacterial infection as a 26,27,28 major contributor. but it may be unclear to what extent some of these organisms are causing the disease or have predisposed 29,30,31,32 the patient to secondary infection by bacterial pathogens. Thus some of our undiagnosed cases could have been of viral etiology. The converse is true that just like viruses there are other CAP pathogens which are non cultivable on a routine basis and this could be the reason for the low yield of organisms in our study.
The increased sputum positivity could be attributed to the good samples that were submitted and a possibility that prior antibiotic therapy was not initiated at any other health care centre. Our blood culture positivity of 19% is comparable to studies by 36,37 Wollschlager et al 10-24%.
Interestingly, acid fast bacilli ( AFB ) positivity was not observed in our study but were identified in 5% cases of acute pneumonia by Oberi et al in India 20 and Ishida T in Japan. 38 The reason for this could probably be the frequent use of fluoroquinolones as an initial empiric antibiotic therapy and exclusion of patients with clinical and radiological presentation suggestive of tuberculosis.
We were unable to isolate Haemophilus influenzae, Mycoplasma pneumoniae, Chlamydia species, Legionella pneumophila and viruses. Newer techniques such as Pneumococcal antigen detection, using a coagglutination test like Phadebact Pneumo coccus test, Pharmacia Diagnostics AB, Sweden, antib odies to Legionella spp by indirect immunofluorescent antibody test ( IFA ), microimmunofluorescence for Chlamydia pneumoniae with antibodies to Mycoplasma pneumoniae, and respiratory tract viruses ( Respiratory syncytial virus, Parainfluenza virus, Influenza A and B virus, and Adenovirus ) with enzyme immunoassays and 39 molecular methods would have helped in clinching the diagnosis. The antibiotics that were useful in most of our cases were Cephalosporins and aminoglycosides. The mortality rate in our study was 10% with varying rates in various hospital based studies , being 5.7% in a British Thoracic Society multi-centric 41,42 study 40 to a higher mortality of (21-25%) in other studies.

Conclusion:
Many issues still remain with respect to the diagnosis of CAP. The etiological agents varies from cultivable to non cultivable pathogens thus requiring supportive serological tests and molecular intervention. Together with the available diagnostic modalities, a good knowledge of the clinical presentations and common risk factors of CAP will go a long way in effective management of these cases.