The etiology of community-acquired pneumonia at an urban public hospital: influence of human immunodeficiency virus infection and initial severity of illness.

In a prospective study, the etiology of community-acquired pneumonia (CAP) was investigated among consecutive patients admitted to an academic, urban public hospital in Seattle. The study population was uniquely young, was predominantly male, and had high rates of homelessness, cigarette smoking, alcoholism, injection drug use, and human immunodeficiency virus (HIV) infection. Leading causes of CAP among HIV-negative patients were aspiration, followed by Streptococcus pneumoniae, Legionella species, and Mycoplasma pneumoniae. Among HIV-positive patients, Pneumocystis carinii, Mycobacterium tuberculosis, S. pneumoniae, and M. pneumoniae were the most common etiologic agents. Severe CAP was associated with typical bacterial infections and aspiration pneumonia but not Legionella infection among HIV-negative patients and with Pseudomonas aeruginosa infections among HIV-positive patients. These findings emphasize the need to tailor empirical antibiotic therapy according to local patient populations and individual risk factors and highlight the importance of recognizing underlying HIV infection in patients who are hospitalized with CAP.     

唐山农村地区老年社区获得性肺炎住院患者病原学分析

目的分析唐山农村地区老年社区获得性肺炎(CAP)住院患者病原学构成并初步分析合并常见基础疾病的病原体构成。方法选择在唐山市3家三级医院住院的唐山市农村地区老年CAP住院患者359例,分析患者痰培养结果,病原学构成,同时分析合并有常见基础疾病的老年CAP患者的病原学特点。结果 359例老年CAP住院治疗患者中,以革兰氏阴性细菌感染占72.9%,伴COPD、脑血管后遗症、糖尿病的老年CAP患者最常见为肺炎克雷伯杆菌感染,支扩中最常见病原体为铜绿假单胞菌。结论老年CAP住院患者以革兰氏阴性菌感染为主,其伴随的基础疾病影响病原学结果。     

The controversy of combination vs monotherapy in the treatment of hospitalized community-acquired pneumonia

BACKGROUND: The majority of community-acquired pneumonia (CAP) patients (about 80%) will be treated as outpatients, because therapy with a single agent will work. For the remaining 20% of patients requiring hospitalization, there is some growing debate regarding the efficacy of different management approaches. For hospitalized patients, monotherapy with a respiratory fluoroquinolone agent seems to be gaining popularity, but dual therapy combining a beta-lactam and an advanced macrolide still represents a good choice. Indeed, this regimen was recommended for all of the inpatient categories in the latest Infectious Disease Society of America CAP guidelines in 2003. AIM: The purpose of this review was to examine the current clinical evidence to support one option or the other by gathering all of the available published literature. We will review the existing controversies in terms of microbiology, immunology, and clinical outcomes comparing dual therapy (ie, with any combination of beta-lactams, macrolides, or fluoroquinolones) with monotherapy in the treatment of CAP. RESULTS: For the vast majority of patients with CAP (ie, outpatients and inpatients on medical wards), the type of antibiotic regimen prescribed does not have any significant impact. For patients with severe pneumonia, for which there is no accepted definition so far, the controversy remains alive. Mortality from pneumococcal pneumonia has been reduced over the last decades, but despite improved medical care, bacteremic pneumococcal pneumonia is still as lethal as ever, probably because of the aging population, the greater number of immunocompromised patients, and the number of patients with frequent comorbid conditions. Worldwide, the increasing rates of resistance of Streptococcus pneumoniae to antibiotics are also a serious concern, and the clinical implications are not always obvious. Although limited in number, the four studies showing the importance of adding a macrolide to a beta-lactam regimen for the treatment of bacteremic S pneumoniae pneumonia are retrospective and nonblinded, the findings are consistent, and they point to a trend that has to be explored more thoroughly. Studies published in the last few years suggest that combination therapy may be superior for bacteremic S pneumoniae pneumonia. CONCLUSION: In the meantime, for practical purposes, patients hospitalized with a diagnosis of severe CAP may benefit from a dual antibiotic therapy combining a third-generation cephalosporin and a macrolide. For the majority of hospitalized patients with CAP who are not severely ill, fluoroquinolone monotherapy remains an approved, tested, and reliable option. Indeed, the time for more aggressive outpatient fluoroquinolone therapy may reduce the number of patients who are hospitalized with CAP. Independent prospective studies comparing combination therapy with standard monotherapy are urgently required for hospitalized patients with severe CAP.     

老年社区获得性肺炎住院患者的临床资料分析

目的总结老年社区获得性肺炎（CAP）患者的临床表现、病原学及预后相关资料。方法回顾性分析2002年1月-2006年1月中山大学附属第三医院收治的成人CAP患者的临床资料,比较老年CAP患者（年龄〉65岁）与中青年CAP患者（年龄≤65岁）临床特征的异同。结果成人CAP患者302例,年龄（68±21）岁。老年CAP患者216例,其中67．1％的患者合并基础疾病,175例（81．0％）患者在Fine危险分级Ⅳ～Ⅴ级,住院病死率为12．0％。肺炎链球菌仍是老年CAP患者最主要的致病菌。与86例中青年CAP患者相比,老年CAP患者入院时出现呼吸困难、急性意识障碍、心率增快及呼吸急促的比例明显增多,病原体分布与中青年CAP患者存在差异。结论老年CAP患者发病率高、并发症多、预后差。临床表现、病原学具有其特殊性,应予足够重视。     

Etiologies and treatment outcomes in patients hospitalized with community-acquired pneumonia (CAP) at Srinagarind Hospital, Khon Kaen, Thailand

Local epidemiological data on the etiologies of in-patients who are hospitalized with CAP is needed to develop guidelines for clinical practice. This study was conducted to determine the pattern of microorganisms causing community-acquired pneumonia (CAP) in adult patients admitted to Srinagarind Hospital, Khon Kaen, Thailand, between January 2001 and December 2002. Altogether, 254 patients (124 males, 130 females) averaging 56.4 (SD 19.8) years were included. Eighty-six of them (33.8%) presented with severe CAP on initial clinical presentation. The etiologies for the CAP cases were discovered by isolating the organisms from the blood, sputum, pleural fluid, and other sterile sites. Serology for Chlamydia pneunmoniae and Mycoplasma pneumoniae were performed to diagnose current infection. The causative organisms were identified in 145 patients (57.1%). Streptococcus pneumoniae was the commonest pathogen, identified in 11.4% of the cases, followed by Burkholderia pseudomallei (11.0%) and Klebsiella pneumoniae (10.2%). The atypical pathogens, C. pneumoniae and M. pneumoniae, accounted for 8.7% and 3.9% of the isolates, respectively. Sixteen patients (6.3%) had dual infections; C. pneumoniae was the most frequent coinfecting pathogen. The average length of hospital stay was 12.9 (SD 14.0) days, with 27.9% staying more than 2 weeks. Overall, 83.9% of the patients improved with treatment, 10.2% did not improve and 5.9% died. The most common complications were acute respiratory failure (31.1%) and septic shock (20.9%). We conclude that initial antibiotic use should cover the atypical pathogens, C. pneumoniae and M. pneumoniae, in hospitalized CAP patients. B. pseudomallei is an endemic pathogen in Northeast Thailand, and should be considered in cases of severe CAP.     

老年社区获得性肺炎住院患者临床资料分析

目的总结老年社区获得性肺炎（CAP）患者的临床表现、病原学及预后相关资料。方法回顾分析2002年1月~2007年10月我院收治的CAP患者的临床资料,比较老年CAP患者（年龄）≥60岁）与中青年患者（年龄≤60岁）临床特征的异同。结果成人CAP患者321例,年龄（67±22）岁。老年CAP患者231例,其中73.4%患者合并基础疾病,住院死亡率为12%,肺炎链球菌仍是老年CAP患者的最主要致病菌。与90例中青年CAP患者相比,老年CAP患者入院时出现呼吸困难、急性意识障碍、心率增快及呼吸急促的比例明显增多,病原体分布与中青年CAP患者存在差异。结论老年CAP患者发病率高、并发症多、预后差。临床表现、病原学具有其特殊性,应予足够重视。     

Etiology and outcome of community-acquired pneumonia in relation to age and severity in hospitalized adult patients]

The aim of this study was to determine the etiology and outcome of community-acquired pneumonia (CAP) in relation to age and severity in hospitalized patients. Overall, 652 consecutive patients with CAP were studied retrospectively during a 4-year period from 2002. Severity of pneumonia was classified according to the guidelines of the Japanese Respiratory Society (JRS 2005) and American Thoracic Society (ATS 2001). The etiology was identified in 401 of 652 (61.5%) cases. The four most frequent pathogens were Streptococcus pneumoniae (26.2%), influenza virus (12.4%), Mycoplasma pneumoniae (10.9%), and Haemophilus influenzae (5.9%). The most common pathogen in the younger (15-44 years) group and very severe patients (JRS) was Mycoplasma pneumoniae (38.4%) and influenza virus (28.6%), respectively. The three most frequent pathogens in severe CAP patients (ATS) were Streptococcus pneumoniae (29.0%), influenza virus (17.4%), and Legionella species (13.0%). The overall mortality was 6.4%. The mortality of CAP patients among aged 1544, 45-64, 65-74, and 75 years or older was 1.4%, 3.3%, 6.9% and 9.3%, respectively. The mortality of mild, moderate, severe, and very severe patients (RS) was 0%, 4.1%, 15.5%, and 53.6%, respectively. The mortality of non-severe and severe patients (ATS) was 1.8% and 23.9%, respectively. Age and severity had influence on the prevalence of the main microbial pathogens. Streptococcus pneumoniae remained the most important pathogen that needs consideration in initial antibiotic therapy in patients with CAP of all ages and severities. Pathogens identified in patients with severe CAP in Japan were similar to those of Western countries, except for the high incidence of the influenza virus.     

不同时期老年社区获得性肺炎患者不典型病原检测结果分析

目的 调查3个时期老年社区获得性肺炎(CAP)住院患者病毒、支原体、衣原体及军团菌感染状况,为临床流行病学研究提供参考. 方法 选取2001年10月至2004年6月[称为围严重急性呼吸综合征(SARS)期]、2005年7月至2007年10月及2008年1月至2010年12月(称为围甲流期)于河北联合大学附属医院住院的492例老年患者作为研究对象,于入院当天及入院后7～10d行血清支原体、衣原体、军团菌IgM抗体及7种常见病毒IgM抗体检查,对3个期间的资料进行分析. 结果 492例患者支原体IgM抗体阳性80人次(16.26％)、衣原体IgM抗体阳性46人次(9.35％)、军团菌IgM抗体阳性25人次(5.08％)、病毒IgM抗体阳性118人次(23.99％).“围SARS期”不典型病原体总检出率及军团菌、合胞病毒、巨细胞病毒、单纯疱疹病毒及风疹病毒检出率明显高于其他2个时期.不典型病原体抗体在起病20d内的检出率较高. 结论 不典型病原体仍为老年CAP的重要致病原,其中以支原体感染最为常见.前后对比围SARS期间病毒感染更为普遍.老年CAP患者不典型病原体感染率无明显上升,部分有下降趋势.在起病20 d内多数不典型病原体感染患者IgM抗体可检出阳性.     

Microbiologic diagnosis of community-acquired pneumonia in adults

Microbiological analysis allows us to identify the etiology of pneumonia and its in vitro susceptibility pattern. Antibiotic treatment directed against a known pathogen enables us to narrow antibacterial spectrum of action, and to reduce costs, drug adverse effects risk and antibiotic resistance. However it is unnecessary to perform extended microbiological studies in all patients with community acquired pneumonia (CAP). Etiological studies must be based in pneumonia severity, epidemiological risk factors and clinical response to empirical treatment. Routine microbiological analysis for ambulatory patients is not recommended. In patients with persistent cough and worsening in their general conditions, a sputum sample must be obtained to perform an acid-fast smear and Mycobacterium culture. The risk of complications and death of patients hospitalized with CAP justifies basic microbiological exploration (sputum Gram staining and culture, blood cultures, pleural fluid culture) intending to obtain a more accurate etiology of pulmonary infection and to guide specific antibiotic treatment. Paired serum samples obtained to document atypical pathogen infections (Mycoplasma pneumoniae, Chlamydia pneumoniae) and urine sample to detect Legionella pneumophila antigenuria are recommended in all CAP severely ill patients that are admitted to ICU, in those not responding to betalactamic drug treatment and in selected patients with specific epidemiological risks. A microbiological study would be useful in management of patients with severe CAP pneumonia outbreaks with clinical-epidemiological particular characteristics, and in-patients with empirical antimicrobial treatment failure.     

Community-acquired pneumonia in elderly patients

CAP in elderly patients carries a significant economic and clinical burden and will be more commonly encountered in the future as the US population ages. Diagnosis may be obscured by a nonclassic presentation in an elderly patient, and the clinician needs to be especially suspicious of pneumonia whenever the clinical status of an elderly patient deteriorates. The single most important clinical decision is the site of care; this determination is not always based on clinical factors but also on social factors. Severity assessment is key to stratifying appropriate therapy and to predicting outcome. Timely and appropriate empiric therapy enhances the likelihood of a good clinical outcome, although clinical resolution may be more delayed than in younger patients. Newly emerging patterns of antibiotic resistance have altered recent guidelines for CAP treatment; DRSP is now a consideration in elderly patients because an age older than 65 years is a well-described risk factor for infection with this organism. Prevention should always be implemented, with a focus on pneumococcal and influenza vaccination.     

Etiology of community-acquired pneumonia in hospitalized patients in chile: the increasing prevalence of respiratory viruses among classic pathogens

BACKGROUND AND STUDY OBJECTIVES: The range and relative impact of microbial pathogens, particularly viral pathogens, as a cause of community-acquired pneumonia (CAP) in hospitalized adults has not received much attention. The aim of this study was to determine the microbial etiology of CAP in adults and to identify the risk factors for various specific pathogens. METHODS: We prospectively studied 176 patients (mean [+/- SD] age, 65.8 +/- 18.5 years) who had hospitalized for CAP to identify the microbial etiology. For each patient, sputum and blood cultures were obtained as well as serology testing for Mycoplasma pneumoniae and Chlamydophila pneumoniae, urinary antigen testing for Legionella pneumophila and Streptococcus pneumoniae, and a nasopharyngeal swab for seven respiratory viruses. RESULTS: Microbial etiology was determined in 98 patients (55%). S pneumoniae (49 of 98 patients; 50%) and respiratory viruses (32%) were the most frequently isolated pathogen groups. Pneumococcal pneumonia was associated with tobacco smoking of > 10 pack-years (odds ratio [OR], 2.6; 95% confidence interval [CI], 1.2 to 5.4; p = 0.01). Respiratory viruses were isolated more often in fall or winter (28%; p = 0.011), and as an exclusive etiology tended to be isolated in patients >/= 65 years of age (20%; p = 0.07). Viral CAP was associated with antimicrobial therapy prior to hospital admission (OR, 4.5; 95% CI, 1.4 to 14.6). CONCLUSIONS: S pneumoniae remains the most frequent pathogen in adults with CAP and should be covered with empirical antimicrobial treatment. Viruses were the second most common etiologic agent and should be tested for, especially in fall or winter, both in young and elderly patients who are hospitalized with CAP.     

Lower respiratory tract infection and pneumonia in the community.

Community-acquired pneumonia (CAP) is common. There is no entirely satisfactory way of defining pneumonia using clinical criteria alone. New focal chest signs on examination in the presence of a systemic illness that is suggestive of a lower respiratory tract infection seems to be the best clinical finding that indicates pneumonia. Progress has been made in identifying simple clinical features that relate to prognosis and allow the general practitioner to decide whether care in the community is appropriate or hospital referral is required. Psychosocial factors for the patient will also remain important. Most patients who have CAP that is mild enough to be managed in the community will require few, if any, investigations. A chest radiograph is appropriate in all patients to exclude an underlying lung tumor. Measurement of surrogate markers of acute infection, such as C-reactive protein, may prove useful to the general practitioner if near testing were to become feasible. The antibiotic management for CAP for patients well enough to be managed at home can be simple and logical, providing general practitioners have some knowledge regarding likely pathogens and etiologic and epidemiological clues. Any antibiotic chosen must suppress Streptococcus pneumoniae, which remains the most common cause of CAP.     

Limited value of routine microbiological diagnostics in patients hospitalized for community-acquired pneumonia

Current guidelines recommend microbiological diagnostic procedures as a part of the management of patients hospitalized for community-acquired pneumonia (CAP), but the value of such efforts has been questioned. Patients hospitalized for CAP were studied retrospectively, focusing on the use of aetiological diagnostic methods and their clinical impact. Adult patients, without known human immunodeficiency virus infection, admitted to hospital for CAP during 12 months, were evaluated with regard to the importance of aetiological diagnosis for tailoring antibiotic therapy, antibiotic-associated diarrhoea, Clostridium difficile disease, length of hospital stay and mortality. Of the 605 studied patients, 482 (80%) were subjected to Mycoplasma pneumoniae and/or respiratory virus serology and/or cultures of blood and/or sputum. They had a better prognosis than patients not subjected to microbiological diagnostics (mortality within 3 months was 9% vs 24%, p = 0.001), apparently reflecting differences in general health (e.g. less dementia diagnosis) but not the outcome of diagnostics. A presumptive aetiology was obtained only in 132 of the 482 patients, Streptococcus pneumoniae and M. pneumoniae being the most common agents (in 49 and 36 patients, respectively). Establishing an aetiological diagnosis had no impact on the number of in-hospital changes of therapy, on the proportion of new regimens having a narrower antimicrobial spectrum than the initial one or on the outcome. Therapy was changed to a drug directed specifically against the identified pathogen in only 16 out of these 132 patients and again without any overall improvement in the outcome variables. In a setting with a low frequency of antibiotic-resistant respiratory tract pathogens current routine microbiological diagnostics were found to be of limited value for the clinical management of patients hospitalized for CAP. Improved diagnostics in CAP are urgently needed, as establishing an aetiological diagnosis carries a potential for optimizing the antibiotic therapy.     

老年人社区获得性肺炎病原学的调查

目的探讨老年人社区获得性肺炎（CAP）发病相关的主要因素及病原学特点。方法对151例老年人CAP住院患者,总结其基础疾病及其病原学分布特点。结果老年人CAP住院患者多有基础疾病,病原学检查检出率为76．1％,致病菌以G-杆菌为主,检出率依次为肺炎克雷白杆菌、肺炎链球菌、铜绿假单胞菌、大肠埃希菌,流感嗜血杆菌、非典型致病菌等。结论老年人CAP住院患者基础疾病多、临床表现不典型、病原菌复杂,应当引起临床医生的高度重视。     

Community-acquired pneumonia: An overview

Community-acquired pneumonia (CAP) accounts for a significant number of hospitalizations and outpatient visits, as well as substantial health care expenditures. CAP is particularly common among the elderly who account for more than 90% of deaths due to pneumonia. Streptococcus pneumoniae is believed to be the most common microbial etiology of CAP, but recent studies suggest that the atypical pathogens may be more common than previously thought, particularly among ambulatory patients. Recent studies have provided data regarding risk of mortality and process of care and outcomes. Increasing resistance among strains of S. pneumoniae has impacted the approach to the empiric therapy of CAP. The Infectious Diseases Society of America published guidelines for the evaluation and management of CAP this past year. Pathogen-specific therapy guided by the results of sputum gram stain and culture is emphasized. Despite enthusiasm for practice guidelines and clinical pathways, there remains insufficient published data to determine their impact on quality and cost of care in patients with CAP.     

Impact of alcohol abuse in the etiology and severity of community-acquired pneumonia

BACKGROUND AND STUDY OBJECTIVES: Alcohol consumption is known to affect both systemic and pulmonary immunity, predisposing the patient to pulmonary infections. The aim of this study was to compare the etiology of disease, the antibiotic resistance of Streptococcus pneumoniae, the severity of disease, and the outcome of patients with alcohol abuse to those of nonalcoholic (NA) patients who have been hospitalized for community-acquired pneumonia (CAP). METHODS: From 1997 to 2001, clinical, microbiological, radiographic, and laboratory data, and follow-up variables of all consecutive patients who had been hospitalized with CAP were recorded. Patients were classified as alcoholic (A) [n = 128] or ex-alcoholic (EA) patients (n = 54) and were compared to NA patients (n = 1,165). RESULTS: S pneumoniae was found significantly more frequently in all patients with alcohol misuse. As regards the rates of antibiotic resistance, invasive pneumococcal disease, and other microorganisms, no differences were found. The severity criteria for CAP according to the American Thoracic Society were more frequent in A patients, but mortality did not differ significantly. Multivariate analysis showed an independent association between pneumococcal CAP and alcoholism (A patients: odds ratio [OR], 1.6; p = 0.033; EA patients: OR, 2.1; p = 0.016). CONCLUSIONS: We found an independent association between pneumococcal infection and alcoholism. Current alcohol abuse was associated with severe CAP. No significant differences were found in mortality, antibiotic resistance of S pneumoniae, and other etiologies.     

Community-acquired pneumonia in younger patients is an entity on its own

Community-acquired pneumonia (CAP) is now most frequent in elderly patients. CAP in the younger patient has attracted much less attention. Therefore, we compared patients with CAP aged 18 to <65 yrs with those aged ≥ 65 yrs. Data from the prospective multicentre Competence Network for Community Acquired Pneumonia Study Group (CAPNETZ) database were analysed for potential differences in baseline characteristics, comorbidities, clinical presentation, microbial investigations, aetiologies, antimicrobial treatment and outcomes. Overall, 7,803 patients were studied. The proportion of younger patients (aged <65 yrs) was 52.3% (18 to <30 yrs 6.4%; <40 yrs 17.1%; <50 yrs 29.4%). Comorbidity was present in only half of the younger patients (46.6% versus 88.2%). Fever and chest pain were more common. Most younger patients presented with mild CAP (74.0% had a CURB-65 score of 0 (confusion of new onset, urea >7 mmol · L(-1), respiratory rate of ≥ 30 breaths · min(-1), blood pressure <90 mmHg or diastolic blood pressure ≤ 60 mmHg, age ≥ 65 yrs)). Overall, Streptococcus pneumoniae and Mycoplasma pneumoniae were the most frequent pathogens in the younger patients. Short-term mortality was very low (1.7% versus 8.2%) and even lower in patients without comorbidity (0.3% versus 2.4%). Long-term mortality was 3.2% versus 15.9%, also lower in patients without comorbidity (0.8% versus 6.1%). Most of the differences found clearly arise after the fifth or within the middle of the sixth decade. CAP in the younger patient is a clinically distinct entity.     

Dual infection with Streptococcus pneumoniae and Mycobacterium tuberculosis in HIV-seropositive patients with community acquired pneumonia.

Pulmonary infections with more than one organism are common in human immunodeficiency virus (HIV) seropositive patients. We describe nine cases of dual infection with Streptococcus pneumoniae and Mycobacterium tuberculosis in HIV-seropositive patients presenting with community acquired pneumonia (CAP). It is important to exclude pulmonary tuberculosis in HIV-seropositive patients with CAP who fail to respond appropriately to initial antibiotic therapy, even if another etiological pathogen has been found.     

Management of patients with community-acquired pneumonia treated in hospital in Sweden

To investigate the management of patients with community-acquired pneumonia (CAP) treated in hospital in Sweden, a multicentre retrospective cohort study was performed with medical record review of 982 patients (mean age 63 y) at 17 departments of infectious diseases at hospitals in Sweden. Information on antimicrobial therapy, demographic characteristics, comorbid conditions, physical examination findings, and laboratory and microbiological test results were recorded. Outcome measures were in-hospital mortality and length of hospital stay (LOS). Cultures were obtained from blood in 80% and from sputum in 22% of the patients. A microbiological aetiology was determined for 23% of the patients, with Streptococcus pneumoniae as the dominating agent (9%). The initial antibiotic treatment was mostly given intravenously (78%). Penicillin (50%) or a cephalosporin (30%) was the most common choice. Both of these drugs were usually given as a single agent. The overall mortality was 3.5% and the mean LOS was 6.4 d. Thus, the outcome was favourable despite the empirical antibiotic treatment having a narrow spectrum compared with the broader approach recommended in most recent guidelines on the management of CAP. These findings suggest that a majority of patients who are hospitalized with moderately severe pneumonia can be treated initially with penicillin alone.     

Community-acquired pneumonia in patients requiring hospitalization

OBJECTIVE: This study aimed to investigate the microbial aetiology of community-acquired pneumonia (CAP) in patients requiring hospitalization. METHODOLOGY: A prospective study of consecutive non-immunocompromised patients aged 12 years and above admitted with CAP from August 1997 to May 1999 was undertaken. RESULTS: Of 127 patients hospitalized for CAP, an aetiological diagnosis was achieved in 53 cases (41.7%). Klebsiella pneumoniae was the most frequently isolated pathogen and caused 10.2% of all the cases, followed by Streptococcus pneumoniae (5.5%), Haemophilus influenzae (5.5%), Mycoplasma pneumoniae (3.9%) and Pseudomonas aeruginosa (3.9%). Gram-negative bacilli were significantly more frequently identified in patients aged 60 years or older and in patients with comorbid illnesses. Twelve of 13 patients who died from CAP had other comorbid illnesses compared to 63 of 114 patients who survived (P = 0.014). Three of eight bacteraemic patients died compared with 10 of 119 non-bacteraemic patients (P = 0.035). CONCLUSIONS: The microbiology of CAP in patients requiring hospitalization in Malaysia appears to be different from that in Western countries. Gram-negative bacilli were more frequently isolated in older patients and in those with comorbidity. Mortality from CAP is more likely in patients with comorbidity and in those who are bacteraemic.