Microbial Etiology Of Community-acquired Pneumonia Research Articles

Microbial aetiology of community-acquired pneumonia in hospitalised adults: A prospective study utilising comprehensive molecular testing

ObjectivesThis study aimed to describe the microbial aetiology of community-acquired pneumonia (CAP) in adults admitted to a tertiary care hospital and assess the impact of syndromic polymerase chain reaction (PCR) panels on pathogen detection. MethodsConducted at Haukeland University Hospital, Norway, from September 2020 to April 2023, this prospective study enrolled adults with suspected CAP. We analysed lower respiratory tract samples using both standard-of-care tests and the BIOFIRE® FILMARRAY® Pneumonia Plus Panel (FAP plus). The added value of FAP Plus in enhancing the detection of clinically relevant pathogens, alongside standard-of-care diagnostics, was assessed. ResultsOf the 3238 patients screened, 640 met the inclusion criteria, with 384 confirmed to have CAP at discharge. In these patients, pathogens with proven or probable clinical significance were identified in 312 (81.3%) patients. Haemophilus influenzae was the most prevalent pathogen, found in 118 patients (30.7%), followed by SARS-CoV-2 in 74 (19.3%), and Streptococcus pneumoniae in 64 (16.7%). Respiratory viruses were detected in 186 (48.4%) patients. The use of FAP plus improved the pathogen detection rate from 62.8% with standard-of-care methods to 81.3%. ConclusionsPathogens were identified in 81% of CAP patients, with Haemophilus influenzae and respiratory viruses being the most frequently detected pathogens. The addition of the FAP plus panel, markedly improved pathogen detection rates compared to standard-of-care diagnostics alone.

Value of sputum Gram stain, sputum culture, and bronchoalveolar lavage fluid Gram stain in predicting single bacterial pathogen among children with community-acquired pneumonia

BackgroundCurrently, the microbial etiology of community-acquired pneumonia in children remains challenging. While Gram stain and sputum culture are commonly used to detect bacterial pathogens, it is unclear whether these approaches can predict single pathogen from bronchoalveolar lavage fluid (BALF) culture.MethodsA retrospective study involving 287 children hospitalized for pneumonia was conducted. Sputum specimens were collected on admission; and BALF specimens were collected within 24 h after admission. Taking BALF culture as the reference standard, the sensitivity and specificity of Sputum Gram stain (SGS), sputum culture, and BALF Gram stain (BGS) were calculated. The agreement between these approaches and BALF culture was compared using kappa statistics.ResultsFor SGS, the specificity was 23%. The overall sensitivity was 70%, including 87% for Gram-positive (G+) cocci, 56% for Gram-negative (G-) cocci, and 50% for G-bacilli. For sputum culture, the specificity was 70%. The overall sensitivity was 64%, including 71% for Streptococcus pneumoniae, 71% for Moraxella catarrhalis, and 64% for Haemophilus influenzae. For BGS, the specificity was 71%. The overall sensitivity was 60%, including 77% for G+cocci, 38% for G-cocci, and 44% for G-bacilli. While SGS had poor agreement with BALF culture, both sputum culture and BGS had moderate agreement with BALF culture.ConclusionsBoth sputum culture and BGS are helpful in predicting single bacterial pathogen from BALF culture among children with community-acquired pneumonia. Sputum cultures and BGS can provide early clues for BALF pathogen when BALF culture results are pending or bronchoscopy is not performed.

The Microbial Etiology of Community-Acquired Pneumonia in Adults: from Classical Bacteriology to Host Transcriptional Signatures.

All modern advances notwithstanding, pneumonia remains a common infection with substantial morbidity and mortality. Understanding of the etiology of pneumonia continues to evolve as new techniques enable identification of already known organisms and as new organisms emerge. We now review the etiology of pneumonia (at present often called "community-acquired pneumonia") beginning with classic bacteriologic techniques, which identified Streptococcus pneumoniae as the overwhelmingly common cause, to more modern bacteriologic studies, which emphasize Haemophilus influenzae, Staphylococcus aureus, Moraxella catarrhalis, Enterobacteriaceae, Pseudomonas, and normal respiratory flora. Urine antigen detection is useful in identifying Legionella and pneumococcus. The low yield of bacteria in recent studies is due to the failure to obtain valid sputum samples before antibiotics are administered. The use of high-quality sputum specimens enables identification of recognized ("typical") bacterial pathogens as well as a role for commensal bacteria ("normal respiratory flora"). Nucleic acid amplification technology for viruses has revolutionized diagnosis, showing the importance of viral pneumonia leading to hospitalization with or without coinfecting bacterial organisms. Quantitative PCR study of sputum is in its early stages of application, but regular detection of high counts of bacterial DNA from organisms that are not seen on Gram stain or grown in quantitative culture presents a therapeutic dilemma. This finding may reflect the host microbiome of the respiratory tract, in which case treatment may not need to be given for them. Finally, host transcriptional signatures might enable clinicians to distinguish between viral and bacterial pneumonia, an important practical consideration.

1484. Microbial Etiology of Community-acquired Pneumonia in Immunocompromised Patients

BackgroundCommunity-acquired pneumonia (CAP) is a leading cause of infection related mortality. Few studies have specifically evaluated the microbial etiology of CAP in immunocompromised patients. Using a large national inpatient database, we compared the microbial etiology of CAP in immunocompromised patients compared to immunocompetent patients.MethodsWe included adult patients admitted with pneumonia from 2010-2015 to 176 US hospitals participating in Premier. Patients were identified as having CAP if they had a chest X-ray and were on antimicrobials on the first day. Immunocompromised was defined by the receipt of immunosuppressive medications or ICD-9 codes for neutropenia/ hematological malignancy/ organ transplantation or comorbidities with AIDS. For microbial etiology, patients were included if they had a positive culture or test collected by hospital day 0 through 3. Patients with identical bacteria in blood and urine were excluded.ResultsA total of 168,159 patients had a diagnosis of CAP with a culture/test performed on first 3 days. A pathogen was detected in 18.8% of patients. Among pathogen positive patients, 4,851 patients were identified as immunocompromised and 26,752 as immunocompetent. Almost all patients (99%) had at least one culture, blood (96%) and respiratory (51%). Among patients who were immunocompromised, the most common bacterial pathogens (compared to immunocompetent patients) were, S. pneumoniae (17.7% vs 19.0%), MRSA (13.1% vs 14.4%), MSSA (12.0% vs 11.8%), P. aeruginosa (12.0% vs 9.9%), E. coli (7.4% vs 6.4%), K. pneumoniae (5.8% vs 4.9%), H. influenzae (5.5% vs 5.5%), M. pneumoniae (3.0% vs 3.0%) and L. pneumophila (0.93% vs 1.2%). Among viral pathogens, while the most common were influenza virus (12.9% vs 14.1%) followed by rhinovirus (1.5% vs 0.89%), immunocompromised patients has a higher prevalence of noninfluennza viruses (3.42% vs 2.43%).ConclusionIn a large US inpatient sample, the causative organisms in immunocompromised patients did not differ much from those in immunocompetent patients. CAP pathogens in immunocompromised patients were more likely to involve gram-negative bacilli such as P.aeruginosa and E.coli, than gram-positive cocci. These findings may have implications when deciding on empiric therapy in these patients.DisclosuresAbhishek Deshpande, MD, PhD, Ferring Pharmaceuticals (Advisor or Review Panel member)Merck (Consultant)

Incidence, Etiology, and Outcomes of Community-Acquired Pneumonia: A Population-Based Study.

BackgroundThe microbial etiology of community-acquired pneumonia (CAP) is often unclear in clinical practice, and previous studies have produced variable results. Population-based studies examining etiology and incidence are lacking. This study examined the incidence and etiology of CAP requiring hospitalization in a population-based cohort as well as risk factors and outcomes for specific etiologies.MethodsConsecutive admissions due to CAP in Reykjavik, Iceland were studied. Etiologic testing was performed with cultures, urine-antigen detection, and polymerase chain reaction analysis of airway samples. Outcomes were length of stay, intensive care unit admission, assisted ventilation, and mortality.ResultsThe inclusion rate was 95%. The incidence of CAP requiring hospitalization was 20.6 cases per 10000 adults/year. A potential pathogen was detected in 52% (164 of 310) of admissions and in 74% (43 of 58) with complete sample sets. Streptococcuspneumoniae was the most common pathogen (61 of 310, 20%; incidence: 4.1/10000). Viruses were identified in 15% (47 of 310; incidence: 3.1/10000), Mycoplasmapneumoniae were identified in 12% (36 of 310; incidence: 2.4/10000), and multiple pathogens were identified in 10% (30 of 310; incidence: 2.0/10000). Recent antimicrobial therapy was associated with increased detection of M pneumoniae (P < .001), whereas a lack of recent antimicrobial therapy was associated with increased detection of S pneumoniae (P = .02). Symptoms and outcomes were similar irrespective of microbial etiology.ConclusionsPneumococci, M pneumoniae, and viruses are the most common pathogens associated with CAP requiring hospital admission, and they all have a similar incidence that increases with age. Symptoms do not correlate with specific agents, and outcomes are similar irrespective of pathogens identified.

Microbial etiology in hospitalized North Indian adults with community-acquired pneumonia.

Background:There is a paucity of literature regarding the microbial etiology of community-acquired pneumonia (CAP) in India. The current study was aimed to study the microbial etiology of hospitalized adults with CAP.Methods:The study was conducted in a 700-bedded North Indian hospital. Consecutive adults admitted with CAP over a period of 2 years from 2013 to 2015 were recruited for the study, and apart from clinical evaluation underwent various microbiological studies in the form of blood culture, sputum culture, urinary antigen for pneumococcus and Legionella, serology for Mycoplasma and Chlamydia and real-time reverse transcriptase polymerase chain reaction for influenza viruses. Radiographic studies were performed in all patients and repeated as required. The patients were treated with standard antibiotic/antiviral therapy and outcomes were recorded.Results:A total of 225 patients (median age: 59 years) were enrolled. Streptococcus pneumoniae was the most common organism found (30.5%), followed by Legionella pneumophila (17.5%), influenza viruses (15.4%), Mycoplasma pneumoniae (7.2%), Chlamydia pneumonia (5.5%), Mycobacterium tuberculosis (4.8%), Klebsiella pneumoniae (4.8%), methicillin-resistant Staphylococcus aureus (3.5%), Pseudomonas aeruginosa (3.1%), methicillin-sensitive S. aureus (1.7%), and Acinetobacter sp. (0.8%) with 4% of patients having multiple pathogens etiologies. High Pneumonia Severity Index score correlated with the severity and outcome of the CAP but was not predictive of any definite etiological pathogen. In-hospital mortality was 8%.Conclusion:Streptococcus pneumoniae, Legionella, and influenza constitute the most common etiological agents for north Indian adults with CAP requiring hospitalization. Appropriate antibiotic therapy and preventive strategies such as influenza and pneumococcal vaccination need to be considered in appropriate groups.

Microbial Etiology of Community-Acquired Pneumonia Among Infants and Children Admitted to the Pediatric Hospital, Ain Shams University.

BackgroundWhile recognizing the etiology of community-acquired pneumonia is necessary for formulating local antimicrobial guidelines, limited data is published about this etiology in Egyptian pediatric patients.ObjectivesTo determine the frequency of bacterial and viral pathogens causing community-acquired pneumonia (CAP) among immunocompetent Egyptian infants and preschool children.MethodsNinety infants and preschool-age children admitted to our hospital with CAP were prospectively included in the study. Etiological agents were identified using conventional bacteriological identification methods and IgM antibodies detection against common atypical respiratory bacteria and viruses.ResultsAn etiology was identified in 59 patients (65.5%). Bacterial pathogens were detected in 43 (47.8%) of the cases while viral pathogens were detected in 23 (25.5%). Coinfection with more than one etiologic agent was evident in seven patients (7.8%). The most common typical bacterial cause of pneumonia was Staphylococcus aureus (n = 12, 13.3%), followed by Streptococcus pneumoniae and Klebsiella pneumoniae (n = 7, 7.8%, each). The commonest atypical bacterium was Mycoplasma pneumoniae (n = 10, 11.1%), whereas the commonest viral etiology was influenza viruses (n = 11, 12.2%).ConclusionAlthough we could not determine the causative agent in some studied cases, this study provides preliminary data regarding the spectrum and frequency of microorganisms causing CAP in Egyptian infants and preschool children.

Aetiology of community-acquired pneumonia in the ICU setting and its effect on mortality, length of mechanical ventilation and length of ICU stay: a 1-year retrospective review

Community-acquired pneumonia (CAP) is the most common infectious reason for admission to ICUs and has mortality of up to 37% [1]. Highest mortality rates are in Gram-negative infections with lower rates in Streptococcus pneumoniae and viral infections [2]. Microbiology is difficult to establish with most prospective studies identifying agents in only 50% of cases [3]. We analysed microbial aetiology of CAP in ICU over 1 year and assessed its effects on inpatient mortality, length of mechanical ventilation and length of ICU stay.

Pneumococcal serotypes and respiratory failure: soil or seed?

When considering the microbial aetiology of community-acquired pneumonia (CAP) we seldom think beyond the name (genus and species) of the causative organism. In a recent study of CAP aetiology in outpatients, Streptococcus pneumoniae was reported to be the most frequent pathogen [1]; unchanged from previous studies. The knowledge that S. pneumoniae is the commonest cause is sufficient to assist the choice of appropriate antibiotics; the most important management decision required for most patients. However, there is a lot more to this bacterial species than the name might imply. In fact, there are now known to be >90 distinct pneumococcal serotypes, each characterised by a slightly different structure in the pneumococcal capsular polysaccharide. These small molecular differences are an important determinant of immune response; therefore, immunity is serotype specific. Studies in the pre-antibiotic era dealt in depth with serotype distributions, as at that time serotype specific serum was the only available therapy. With the advent of antibiotics, pneumococcal serotypes have received much less attention. Now with the development of pneumococcal vaccines, and the importance of matching vaccines to causative serotypes, this subject is having a renaissance. From this we are starting to understand that there is more to the different serotypes than just a difference in polysaccharide structure. Indeed, the serotype is increasingly being linked, not just with the immune response, but also with the clinical phenotype in individual patients. In this issue of the European Respiratory Journal , Burgos et al. [2] describe an investigation into the risk factors for respiratory failure (defined as …

Gastric Acid Suppressive Therapy and Community-Acquired Pneumonia, Etiology and Outcome

Background: Community acquired pneumonia (CAP) is an infection of the pulmonary parenchyma that can be caused by various microbial pathogens. Co-morbidity and medication are related to specific pathogens. Patients on gastric acid suppressive therapy have an increased risk to develop CAP. We aimed to assess whether there are specific pathogens independently associated with gastric acid suppressive therapy and its impact on infection severity. Methods: From December 2007 to January 2010, all subjects consulting the emergency care unit of a general hospital in the south of the Netherlands with a suspected CAP were prospectively registered. Each patient underwent chest radiography. Sputum, urine, nose swabs and blood samples were obtained for microbial culture, antigen detection and polymerase chain reaction techniques, respectively. To study the severity of CAP upon presentation, the validated CURB-65 score was calculated. Furthermore, we assessed hospital or intensive care admission, length of hospitalization and in-hospital mortality. We evaluated the association between use of acid suppressive therapy and microbial aetiology of CAP and severity of illness with logistic regression analysis. Results: The final cohort comprised 463 patients with CAP, defined as presence of infiltrate on chest radiography and/ or microbial aetiology. Overall 136 patients (29%) used acid suppressive therapy, mainly proton pump inhibitors (97%). Patients with acid suppressive therapy more frequently had an infection with Streptococcus pneumoniae (28% vs. 14%) and Haemophilus influenzae (10% vs. 6%), and less frequently with Coxiella burnetii (8% vs. 19%) or H1N1 influenza A virus (2% vs. 7%) in comparison to those without acid suppressive therapy. After adjustment for baseline differences, the risk of proton pump inhibitor users being infected with S. pneumonia was 2.18 times (95%Confidence Interval(CI): 1.2-3.6) higher compared to those not on acid suppressive therapy. Patients using more than one defined daily dose of a PPI had a 1.48-fold increased risk of a S. pneumoniae infection compared with patients using the defined daily dose (95%CI:1.1-2.0). No risk between PPI use and any other microbial pathogen was found. Patients with acid suppressive therapy had on average higher CURB-65 scores, longer hospital stay and subsequently a case fatality rate of 11% vs. 4% compared to those not using acid suppressive therapy. Conclusions. Proton pump inhibitor therapy predisposes with community acquired S. pneumoniae pneumonia, and was associated with higher morbidity.

Microbial aetiology of community-acquired pneumonia and its relation to severity

BackgroundThe distribution of the microbial aetiology and mortality of community-acquired pneumonia (CAP) was investigated in relation to the clinical setting and severity scores (pneumonia severity index (PSI) and confusion, blood...

Etiology of Community‐Acquired Pneumonia: Increased Microbiological Yield with New Diagnostic Methods

BackgroundThe microbial etiology of community-acquired pneumonia (CAP) is still not well characterized. During the past few years, polymerase chain reaction (PCR)-based methods have been developed for many pathogens causing respiratory tract infections. The aim of this study was to determine the etiology of CAP among adults—especially the occurrence of mixed infections among patients with CAP—by implementing a new diagnostic PCR platform combined with conventional methods.MethodsAdults admitted to Karolinska University Hospital were studied prospectively during a 12-month period. Microbiological testing methods included culture from blood, sputum, and nasopharyngeal secretion samples; sputum samples analyzed by real-time quantitative PCR for Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis; nasopharyngeal specimens analyzed by use of PCR; serological testing for Mycoplasma pneumoniae, Chlamydophila pneumoniae, and viruses common in the respiratory tract; and urine antigen assays for detection of pneumococcal and Legionella pneumophila antigens.ResultsA microbial etiology could be identified for 67% of the patients (n = 124). For patients with complete sampling, a microbiological agent was identified for 89% of the cases. The most frequently detected pathogens were S. pneumoniae (70 patients [38]) and respiratory virus (53 patients [29]). Two or more pathogens were present in 43 (35%) of 124 cases with a determined etiology.ConclusionsBy supplementing traditional diagnostic methods with new PCR-based methods, a high microbial yield was achieved. This was especially evident for patients with complete sampling. Mixed infections were frequent (most commonly S. pneumoniae together with a respiratory virus).

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.

Prior outpatient antibiotic use as predictor for microbial aetiology of community-acquired pneumonia: hospital-based study.

ObjectiveThe causative micro-organism in community-acquired pneumonia (CAP) is often difficult to predict. Different studies have examined chronic morbidity and clinical symptoms as predictors for microbial aetiology of pneumonia. The aim of our study was to assess whether prior outpatient antimicrobial treatment is predictive for determining the microbial aetiology of CAP.MethodsThis was a hospital-based prospective observational study including all patients admitted with CAP between 1 October 2004 and 1 August 2006. Microbial investigations included sputum, blood culture, sputum PCR, antigen testing and serology. Exposure to antimicrobial drugs prior to hospital admission was ascertained through community pharmacy dispensing records. Multivariate logistic regression analysis was conducted to assess whether prior outpatient antimicrobial treatment is a predictor of microbial aetiology. Patient demographics, co-morbidities and pneumonia severity were considered to be other potential predictors.ResultsOverall, 201 patients were included in the study. The microbial aetiology was determined in 64% of the patients. The five most prevalent pathogens were Streptococcus pneumoniae, Heamophilus influenzae, Legionella spp., Mycoplasma pneumoniae and Influenza virus A+B. Forty-seven of the patients (23%) had received initial antimicrobial treatment as outpatients. Multivariate analyses revealed that initial outpatient beta-lactam treatment was associated with a threefold increased chance of finding atypical pathogens and a threefold decreased probability of pneumococcal infection; the corresponding odds ratios were 3.51 (95% CI 1.25–9.99) and 0.30 (95% CI 0.10–0.90), respectively. Patients who received macrolides prior to hospitalisation had an increased probability of viral pneumonia.ConclusionPrior outpatient antimicrobial therapy has a predictive value in the diagnostic workup aimed at identifying the causative pathogen and planning corresponding antimicrobial treatment in patients hospitalised for pneumonia.

Culturing Chlamydophila pneumoniae

Chlamydophila pneumoniae (formerly Chlamydia pneumoniae) is an intracellular pathogen responsible for respiratory tract infection. A recent British survey of the microbial aetiology of community-acquired pneumonia (CAP) indicated that C. pneumonia is responsible for 13% of CAP and is the second highest bacterial cause of CAP 1. It has been associated with bronchitis, pharyngitis, sinusitis, myocarditis, endocarditis and coronary artery disease 2. In order to treat C. pneumoniae infections it is first essential to know the efficacy of the available antimicrobial agents against this pathogen. Minimum inhibitory concentration (MIC) tests are used to investigate the in vitro capabilities of antimicrobial agents on bacteria. Therefore, MIC testing of C. pneumoniae needs to be carried out before an antimicrobial agent is used to treat the infection. Culturing of C. pneumoniae must occur before MIC tests can be performed. C. pneumoniae is known to be very difficult to culture and is far more difficult than other chlamydial species 2. Many methods of culturing C. pneumoniae have been proposed with differing cell lines, centrifugation conditions and incubation times. There is no standard method for culturing C. pneumoniae nor for testing the MIC of antimicrobial agents against it. There is no agreement on optimal culture conditions between different Journal of Chemotherapy Vol. 14 n. 3 (312-313) 2002

Community-acquired pneumonia in patients requiring hospitalization.

This study aimed to investigate the microbial aetiology of community-acquired pneumonia (CAP) in patients requiring hospitalization. A prospective study of consecutive non-immunocompromised patients aged 12 years and above admitted with CAP from August 1997 to May 1999 was undertaken. 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). 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.

Microbial etiology of community-acquired pneumonia in the adult population of 4 municipalities in eastern Finland.

To determine the etiology of community-acquired pneumonia in the adult population of a defined area, specific antibody responses in paired serum samples, levels of circulating pneumococcal immune complexes in serum samples, and pneumococcal antigen in urine were measured. Samples (304 paired serum samples and 300 acute urine samples) were obtained from 345 patients > or =15 years old with community-acquired, radiologically confirmed pneumonia, which comprised all cases in the population of 4 municipalities in eastern Finland during 1 year. Specific infecting organisms were identified in 183 patients (including 49 with mixed infection), as follows: Streptococcus pneumoniae, 125 patients; Haemophilus influenzae, 12; Moraxella catarrhalis, 8; chlamydiae, 37 (of which, Chlamydia pneumoniae, 30); Mycoplasma pneumoniae, 30; and virus species, 27. The proportion of patients with pneumococcal infections increased and of those with Mycoplasma infections decreased with age, but for each age group, the etiologic profile was similar among inpatients and among outpatients. S. pneumoniae was the most important etiologic agent. The annual incidence of pneumococcal pneumonia per 1000 inhabitants aged > or =60 years was 8.0.

Community-acquired pneumonia: the evolving challenge

Community-acquired pneumonia (CAP) is a common disorder that has been the focus of a major international research effort to define its epidemiology, etiology and management. The microbial etiology of CAP is complex and severity assessment is important in identifying at-risk populations as well as defining therapeutic strategies. Laboratory investigations rarely influence initial therapy, which remains empirical. Guidelines have been developed in many countries in response to the need to optimize management and outcomes. However, many of these guidelines have been based on expert opinion rather than robust evidence. New evidence-based guidelines have been developed that take into account disease severity, the local distribution of pathogens and their likely susceptibility to antimicrobials, and that include newer treatment options. Macrolide and fluoroquinolone antimicrobials feature heavily in these new treatment recommendations. Promising new therapies continue to emerge that may offer advantages over fluoroquinolones and macrolides, in particular with regard to the problem of resistance. Of these, the ketolides are of special interest. Telithromycin, the first ketolide antibacterial, has been evaluated in the treatment of > 700 patients with CAP. A once-daily oral dose of telithromycin 800 mg for 7-10 days produces clinical and bacteriological success rates > 90% and equivalent to standard comparator agents, whilst maintaining efficacy against resistant pathogens.

Microbial aetiology of community-acquired pneumonia in hospitalised patients.

Adult patients hospitalised with community-acquired pneumonia were studied prospectively to determine the microbial aetiology of pneumonia. Between April 1996 and March 1997, blood and sputum samples were collected for culture. Throat swabs were obtained for isolation of viruses and for detection of antigens of Chlamydia pneumoniae, influenza viruses A and B, respiratory syncytial virus and parainfluenza virus. Antibodies against Legionella spp., Mycoplasma pneumoniae, Chlamydia pneumoniae, Chlamydia psittaci, Coxiella burnetii, influenza viruses A and B, respiratory syncytial virus, adenovirus and parainfluenza virus were tested in serum samples. Two hundred eleven patients were included in the study; paired sera were available from 152 patients. Blood culture was positive in 23 (10.9%) patients, Streptococcus pneumoniae being the bacterium isolated most frequently. A fourfold or greater rise or fall in the Chlamydia pneumoniae IgG and/or IgM antibody titre was found in 20 (9.5%) patients and a high antibody titre (> or = 1:512) in the first and/or the second serum sample in 18 (18.5%) patients. Antibodies confirming acute Mycoplasma pneumoniae infection were found in 12 (5.7%) patients, Legionella spp. in six (2.8%), Chlamydia psittaci in two and Coxiella burnetii in one. Three patients had pulmonary tuberculosis. Only two patients had a virus present in the throat swab (adenovirus in one patient and echovirus in the other), and in nine patients, viral antigen was detected. Acute viral infection was confirmed in 51 (24.1%) patients. Bacterial pneumonia was diagnosed in 84 (39.8%) patients, 23 of whom had concurrent viral infection. Acute viral pneumonia without any other identified pathogen was diagnosed in 28 patients. Streptococcus pneumoniae and Chlamydia pneumoniae were the most frequently identified microorganisms.