Risk factors for pneumococcal endocarditis.

Bacteremia is one of the most common manifestations of invasive pneumococcal disease (IPD). One complication of bacteremia is endocarditis; yet, few studies have evaluated the overall incidence and risk factors for IPD-associated endocarditis. Thus, we evaluated the overall incidence and risk factors of endocarditis compared to those without endocarditis in a large population of IPD patients. We prospectively collected all IPD cases from 2000 to 2014 in Northern Alberta, Canada. Descriptive statistics were used to compare sociodemographic variables, clinical characteristics, and IPD-related outcomes between patients with and without endocarditis. Endocarditis complicated the course of only 28 (0.3%) of 3251 adult patients with IPD. Endocarditis patients were more likely to use illicit drugs and have a higher severity of illness at presentation (i.e., higher rate of altered mental status and rate of intensive care unit [ICU] utilization, p < 0.05); however, no other major risk factors were identified. New murmur development among endocarditis patients was common: 39.3% compared to 2.2% of non-endocarditis patients (p < 0.001). The mortality rate of 39.3% was more than twice that of the rate of 14.7% for the patients with IPD but without endocarditis. There was no pneumococcal serotype predilection for endocarditis. Endocarditis is an uncommon complication of IPD, but, when present, is associated with a significantly increased risk of mortality. Overall, few specific risk factors were identified for IPD-related endocarditis, with the exception of illicit drug use.

Invasive Pneumococcal Disease: Still Lots to Learn and a Need for Standardized Data Collection Instruments.

Background. Large studies of invasive pneumococcal disease (IPD) are frequently lacking detailed clinical information. Methods. A population-based 15-year study of IPD in Northern Alberta. Results. 2435 patients with a mean age of 54.2 years formed the study group. Males outnumbered females and Aboriginal and homeless persons were overrepresented. High rates of smoking, excessive alcohol use, and illicit drug use were seen. Almost all (87%) had a major comorbidity and 15% had functional limitations prior to admission. Bacteremia, pneumonia, and meningitis were the most common major manifestations of IPD. Almost half of the patients had alteration of mental status at the time of admission and 22% required mechanical ventilation. Myocardial infarction, pulmonary embolism, and new onset stroke occurred in 1.7, 1.3, and 1.1% of the patients, respectively; of those who had echocardiograms, 35% had impaired ventricular function. The overall in-hospital mortality was 15.6%. Conclusions. IPD remains a serious infection in adults. In addition to immunization, preventative measures need to consider the sociodemographic features more carefully. A standard set of data need to be collected so that comparisons can be made from study to study. Future investigations should target cardiac function and pulmonary embolism prevention in this population.

The impact of multimorbidity on short-term events in patients with community-acquired pneumonia: prospective cohort study.

The impact of multimorbidity on patients with community-acquired pneumonia has not been well characterised. Thus, our aim was to explore the relationship between multimorbidity and adverse events within 90 days of discharge. Data were prospectively collected for a population-based cohort of all adults discharged from any of the seven emergency departments (ED) or six hospitals in Edmonton (Alberta, Canada) with community-acquired pneumonia. Multivariable Cox regression models were used to examine the independent association between multimorbidity (defined as two or more chronic conditions) and subsequent 90-day mortality, hospitalisation, or ED visits after treatment of pneumonia. The cohort included 5565 patients, mean age was 57 years (SD 20), 54% were male, and 59% were treated as outpatients; 1602 (29%) patients had multimorbidity. Within 90 days, 255 (5%) patients died, 1205 (22%) were hospitalised, 1280 (23%) died or were hospitalised, and 2049 (37%) were admitted to the ED. The presence of multimorbidity was independently associated with an increased risk of death or hospitalisation within 90 days (37% vs. 17% for those without multimorbidity, adjusted hazard ratio: 1.43, 95% confidence interval: 1.26 to 1.62) as well as ED visits (45% vs. 34%, adjusted hazard ratio: 1.40, 95% confidence interval: 1.26 to 1.56). Multimorbidity was present in one-third of all patients with pneumonia in our study, and it was independently associated with death, hospitalisation, or return to ED within 90 days of discharge. Our findings suggest that multimorbidity is strongly related to prognosis and should be considered when making site-of-care decisions in the ED or deciding upon readiness for discharge.

Recurrent pneumonia: a review with focus on clinical epidemiology and modifiable risk factors in elderly patients.

Community-acquired pneumonia (CAP) is one of the most common reasons for physician visits and hospitalizations in North America. Rates of CAP increase with age and CAP is associated with significant morbidity and mortality, especially in the elderly. Though there is much written about the epidemiology and risk factors of incident (first episode) pneumonia, much less is known about recurrent pneumonia. Rates of recurrent pneumonia within 3-5-years of an episode of CAP are 9-12% with a median time to recurrence of 123-317 days and mortality ranging from 4 to 10%. Age ≥65-years-old and impaired functional status are the only patient characteristics that are independently associated with increased risk of recurrence. In terms of modifiable risk factors, only the use of proton-pump inhibitors and systemic and inhaled corticosteroids have consistently been associated with increased risk of recurrent pneumonia, while angiotensin-converting enzyme (ACE) inhibitors may exert a protective effect. Many chronic medical conditions typically associated with increased incident pneumonia-such as chronic obstructive pulmonary disease (COPD), neurological disease (resulting in dysphagia or silent aspiration), and heart failure-were not associated with increased risk of recurrent pneumonia. However, those who are immune-suppressed (e.g., immunoglobulin deficiencies) may be at increased risk of recurrent pneumonia. In summary, among those who survive an episode of pneumonia, recurrence is not uncommon, particularly in the elderly. Following recovery from an episode of pneumonia, patients should be evaluated for risk factors that would predispose to a second episode including seeking evidence of immunosuppression in younger patients and medication optimization, particularly in the elderly.

Rates and risk factors for recurrent pneumonia in patients hospitalized with community-acquired pneumonia: population-based prospective cohort study with 5 years of follow-up.

BACKGROUND: The rates and risk factors for developing recurrent pneumonia following hospitalization with community-acquired pneumonia (CAP) are poorly understood. METHODS: We examined a population-based cohort of patients with CAP who survived hospital admission and who were free of pneumonia for at least 3 months. We collected clinical, functional, and medication-related information and pneumonia severity index (PSI). Using linked databases we followed patients for 5 years and captured any clinical episode of pneumonia 90 days or more post-discharge. We used Cox proportional hazards models (adjusted for age, sex, PSI, functional status, medications) to determine rates and independent correlates of recurrent pneumonia. RESULTS: The final cohort included 2709 inpatients; 43% were 75 years or older, 34% were not fully independent, and 56% had severe pneumonia. Over 5 years of follow-up, 245 (9%; 95% confidence interval [CI], 8%-10%) patients developed recurrent pneumonia, and 156 (64%) of these episodes required hospitalization. Rate of recurrence was 3.0/100 person-years and median time to recurrence was 317 days (interquartile range, 177-569); 32 (13%) patients had 2 or more recurrences. In multivariable analyses only age >75 years (adjusted P = .047) and less than fully independent functional status (12% recurrence rate with impaired functional status vs 7% for fully independent; adjusted hazard ratio, 1.7; 95% CI, 1.3-2.2; P < .001) were significantly associated with recurrent pneumonia. CONCLUSIONS: One of 11 patients who survived CAP hospitalization had recurrent pneumonia over 5 years and those with impaired functional status were at particularly high risk. Recurrent pneumonia is common and more attention to preventive strategies at discharge and closer follow-up over the long-term seem warranted.

Impact of guideline-concordant antibiotics and macrolide/ß-lactam combinations in 3203 patients hospitalized with pneumonia: prospective cohort study.

For patients hospitalized with pneumonia, guidelines provide empirical antibiotic recommendations and some studies suggest that macrolide/ß-lactam combinations are preferable. We hypothesized that guideline-concordant regimens, particularly macrolide/ß-lactams, would reduce mortality and ICU admissions. All patients hospitalized with pneumonia in Edmonton, Alberta, Canada, were managed according to a clinical pathway and enrolled in a population-based registry. Clinical data, Pneumonia Severity Index and treatments were collected. Guideline-concordant regimens were macrolides/ß-lactams or respiratory fluoroquinolone monotherapy. The main outcome was in-hospital mortality. The study included 3203 patients and most had severe pneumonia (63% PSI Class IV-V). Three hundred and twenty-one (10.0%) patients died, 306 (9.6%) were admitted to the ICU and 570 (17.8%) achieved the composite of death or ICU admission. Most (n = 2506) patients received guideline-concordant antibiotics. Receipt of guideline-concordant antibiotics was not associated with a reduction in mortality alone (231 (9.2%) vs. 90 (12.9%); adjusted odds ratio (aOR), 0.82; 95% CI, 0.61-1.09; p 0.16), but was associated with decreased death or ICU admission (14.7% vs. 29.0%; aOR, 0.44; 95% CI, 0.36-0.54; p < 0.0001). Within guideline-concordant subgroups, there was no difference in mortality between macrolide/ß-lactams and respiratory fluoroquinolone monotherapy (22 (8.3%) vs. 209 (9.3%); aOR, 1.09; 95% CI, 0.66-1.81; p 0.73) but macrolide/ß-lactams were associated with increased odds of death or ICU admission (17.4% vs. 14.4%; aOR, 1.58; 95% CI, 1.09-2.27; p 0.01). In conclusion, guideline-concordant antibiotics were not associated with decreased mortality for patients hospitalized with pneumonia, but were associated with a decrease in the composite endpoint of death or ICU admission. Our findings do not support any clinical advantage of macrolide/ß-lactam compared with respiratory fluoroquinolone monotherapy.

Obesity and outcomes in patients hospitalized with pneumonia.

Studies suggest obesity is paradoxically associated with better outcomes for patients with pneumonia. Therefore, we examined the impact of obesity on short-term mortality in patients hospitalized with pneumonia. For 2 years clinical and radiographic data were prospectively collected on all consecutive adults admitted with pneumonia to six hospitals in Edmonton, Alberta, Canada. We identified 907 patients who also had body mass index (BMI, kg/m(2)) collected and categorized them as underweight (BMI < 18.5), normal (18.5 to <25), overweight (25 to <30) and obese (>30). Overall, 65% were >65 years, 52% were female, and 15% reported recent weight loss. Eighty-four (9%) were underweight, 358 (39%) normal, 228 (25%) overweight, and 237 (26%) obese. Two-thirds had severe pneumonia (63% PSI Class IV/V) and 79 (9%) patients died. In-hospital mortality was greatest among those that were underweight (12 [14%]) compared with normal (36 [10%]), overweight (21 [9%]) or obese (10 [4%], p <0.001 for trend). Compared with those of normal weight, obese patients had significantly lower rates of in-hospital mortality in multivariable logistic regression analyses: adjusted odds ratio (OR), 0.46; 95% CI, 0.22-0.97; p 0.04. However, compared with patients with normal weight, neither underweight (adjusted OR, 1.13; 95% CI, 0.54-2.4; p 0.7) nor overweight (adjusted OR, 0.94; 95% CI, 0.52-1.69; p 0.8) were associated with in-hospital mortality. In conclusion, in patients hospitalized with pneumonia, obesity was independently associated with lower short-term mortality, while neither being underweight nor overweight were. This suggests a protective influence of BMIs > 30 kg/m(2) that requires better mechanistic understanding.

Increased risk of invasive pneumococcal disease in haematological and solid-organ malignancies.

Large-scale population-based studies have reported a significant increase in invasive pneumococcal disease (IPD) in those with underlying haematological or solid-organ malignancy, but limited condition-specific data are available on rates of IPD in the adult population. A retrospective chart review of all patients with IPD (identified prospectively) in the province of Alberta, Canada (population ~3·3 million) was conducted from 2000 to 2004 to study the epidemiology of IPD. Rates of IPD in patients with various haematological and solid-organ malignancies were determined by obtaining the number of these patients at risk from the provincial cancer registry. Compared to the attack rate of IPD in the adult population aged ≥18 years (11·0 cases/100,000 per year, 95% CI 10·44-11·65), there were significantly increased rates of IPD in those with lung cancer (143·6 cases/100,000 per year, OR 13·4, 95% CI 9·3-19·4, P<0·001) and multiple myeloma (673·9 cases/100,000 per year, OR 62·8, 95% CI 39·6-99·8, P<0·001). More modestly increased rates of IPD were found in those with chronic lymphocytic leukaemia, acute myeloid leukaemia, acute lymphoblastic leukaemia, and Hodgkin's and non-Hodgkin's lymphoma. There was an increased prevalence of serotype 6A in those with these underlying malignancies, but no other serotypes predominated. Fifty-three percent (48/83) of cases were caused by serotypes in the investigational 13-valent pneumococcal conjugate vaccine (PCV13), and 57/83 (69%) of the cases were caused by serotypes in the 23-valent pneumococcal polysaccharide vaccine (PPV23). The incidence of IPD in adults with certain haematological and solid-organ malignancies is significantly greater than the overall adult population. Such patients should be routinely given pneumococcal polysaccharide vaccine; this population could also be targeted for an expanded valency conjugate vaccine.

Dysglycaemia and 90 day and 1 year risks of death or readmission in patients hospitalised for community-acquired pneumonia.

AIMS/HYPOTHESIS: The aim of this study was to investigate whether dysglycaemia at admission is associated with adverse events at 90 days or 1 year in a population-based cohort of patients hospitalised with community-acquired pneumonia (CAP). METHODS: Clinical and laboratory data were prospectively collected on all 2,366 adults without diabetes admitted with CAP to six hospitals in Edmonton (AB, Canada) and grouped according to admission glucose: 4.0 to <6.1 mmol/l(n=778, reference group), 6.1 to <7.8 mmol/l (n=924); 7.8 to<11.1 mmol/l (n=535); and 11.1 to 20 mmol/l (n=129). Multivariable Cox models were used to examine the relationship between dysglycaemia and mortality or CAP readmission during follow-up. RESULTS: The mean age was 69 (SD 18) years and 48% of participants were female. Compared with those with glucose <6.1 mmol/l (114 [15%] deaths), no differences in 90 day mortality were observed in the dysglycaemia groups: 143 deaths (15%) in the 6.1-7.8 mmol/l group (adjusted HR [aHR] 0.92, 95% CI 0.72-1.18), 111 deaths (21%) in the 7.8-11.1 mmol/l group (aHR 1.05, 0.81-1.37)and 34 deaths (26%) in the 11.1-20 mmol/l group (aHR 1.30, 0.88-1.93). Similarly, compared with those in the <6.1 mmol/l group (198 [25%] deaths), no difference in 1 year mortality was observed: 233 deaths (25%) in the 6.1 to <7.8 mmol/l group (aHR 0.86, 0.71-1.04), 164 deaths (31%) in the 7.8 to <11.1 mmol/l group (aHR 0.92, 0.75-1.14) and 49 deaths (38%) in the 11.1 to 20 mmol/l group (aHR 1.12, 0.81-1.55). Readmissions for CAP were also similar at 1 year: compared with 10% (70/707) in the 6.1 mmol/l group, the frequencies were 8% (66/842), 9% (45/474) and 10% (11/107) in the 6.1 to <7.8 mmol/l, 7.8 to <11.1 mmol/l, and 11.1 to 20 mmol/l groups, respectively (p>0.05 for all comparisons). CONCLUSIONS/INTERPRETATION: Although previously associated with inpatient morbidity and mortality, admission dysglycaemia was not associated with an increased risk of death or CAP readmission at 90 days or 1 year among those who survived hospitalisation for pneumonia.

Does sputum culture affect the management and/or outcome of community-acquired pneumonia?

This prospective study was conducted in 6 hospitals in Edmonton, Canada to determine the factors associated with obtaining sputum for culture and the effect of sputum culture on the management of patients with community-acquired pneumonia (CAP). Participants were 1362 adults who were hospitalized with CAP. Sputum was obtained from 539 (39.6%) patients, of which 507 (94.1%) were good quality, acceptable for culture; 171 (33.7%) of these had a positive sputum culture. Levofloxacin, cefuroxime and azithromycin were the most common antibiotics prescribed for the groups with positive sputum culture and no sputum collection. Positive sputum culture was demonstrated in only a small number of patients with CAP; this did not affect antimicrobial therapy or mortality.

Ovine-associated Q fever.

In Atlantic Canada, the traditional risk factor for acquisition of Q fever infection has been exposure to infected parturient cats or newborn kittens. In this study we describe the first case of Q fever in Nova Scotia acquired as a result of direct exposure to sheep. A serosurvey of the associated flock was undertaken using an indirect immunofluorescence assay (IFA) testing for antibodies to phase I and phase II Coxiella burnetii antigens. This serosurvey revealed that 23 of 46 sheep (50%) were seropositive for the phase II antibody. Four of these sheep had titres of 1:64 including three nursing ewes, one of which had delivered two lambs that died shortly after delivery. Only one ewe had phase I antibodies but had the study's highest phase II antibody titre (1:128). Molecular studies using polymerase chain reaction (PCR) failed to detect C. burnetii DNA in any of the milk specimens.

Does sputum culture affect the management and/or outcome of community-acquired pneumonia?

This prospective study was conducted in 6 hospitals in Edmonton, Canada to determine the factors associated with obtaining sputum for culture and the effect of sputum culture on the management of patients with community-acquired pneumonia [CAP]. Participants were 1362 adults who were hospitalized with CAP. Sputum was obtained from 539 [39.6%] patients, of which 507 [94.1%] were good quality, acceptable for culture; 171 [33.7%] of these had a positive sputum culture.Levofloxacin, cefuroxime and azithromycin were the most common antibiotics prescribed for the groups with positive sputum culture and no sputum collection. Positive sputum culture was demonstrated in only a small number of patients with CAP; this did not affect antimicrobial therapy or mortality

Admission is not always necessary for patients with community-acquired pneumonia in risk classes IV and V diagnosed in the emergency room.

OBJECTIVE: To determine the factors that allow patients with community-acquired pneumonia who are at high risk of mortality (risk classes IV and V) to be treated at home. DESIGN: A prospective, observational study. SETTING: Six hospitals and one free-standing emergency room in Edmonton, Alberta. PARTICIPANTS: The present study included 2354 patients in risk classes IV and V who had a diagnosis of pneumonia made by an emergency room physician or an internist. MEASUREMENTS: Symptoms, signs and laboratory findings, as well as outcome measures of length of stay and mortality. RESULTS: Of the total study group, 319 of the patients (13.5%) were treated on an ambulatory basis. Factors predictive of admission were definite or possible pneumonia on chest radiograph as read by a radiologist, functional impairment, altered mental status, substance abuse, psychiatric disorder, abnormal white blood cell count, abnormal lymphocyte count, oxygen saturation less than 90% and antibiotic administration in the week before admission. If chest pain was present, admission was less likely. Only two of the 319 patients required subsequent admission (both had positive blood cultures) and only two died. CONCLUSIONS: A substantial number of patients in risk classes IV and V can be safely treated at home. Factors that help clinicians to select this subset of patients are discussed.

Addition of a macrolide to a ss-lactam in bacteremic pneumococcal pneumonia.

In the study presented here, data collected prospectively from 340 adult patients hospitalised in five countries with bacteremic pneumococcal CAP and treated with a ss-lactam +/- a macrolide were analysed retrospectively to evaluate the efficacy of this antimicrobial combination. Univariate and multivariate analyses revealed no significant effect on case fatality rate when a macrolide/ss-lactam regimen was used as initial therapy. Results were not affected by severity of illness, or by excluding patients who died within 2 days of admission. Identified predictors of death in a multivariate regression model were age >65 years (OR=2.6), two or more lung lobes affected (OR=2.2), and severity of disease as estimated using the acute physiology score (APS)>8.

Therapeutic implications of macrolide resistance in pneumococcal community-acquired lower respiratory tract infections.

Macrolide anti-bacterials are widely used for the empirical treatment of lower respiratory tract infections (RTIs) due to their activity against Streptococcus pneumoniae and other common respiratory pathogens and good safety/tolerability profile. However, the prevalence of macrolide resistance, particularly pneumococcal macrolide resistance, is increasing all around the world. The mechanisms underlying macrolide resistance include efflux pump, methylase activity and, less commonly, ribosomal mutation, which produce differing levels of resistance. Growth in macrolide resistance has been linked to the increased use of these agents, and several risk factors for the development of resistance have been identified. There are emerging data to suggest that in vitro macrolide resistance may increase the likelihood of treatment failure in patients with lower RTIs. However, at present, treatment failure is rare and randomised; intervention-based trials investigating the impact of anti-bacterial resistance on clinical outcomes are lacking. Strategies to promote appropriate use of macrolides and other anti-bacterials are needed, both to maximise therapeutic impact and to minimise the development of resistance. Furthermore, there is a need for alternative anti-bacterial agents which have high efficacy against respiratory pathogens (including resistant strains) and a low potential to induce resistance.

Deaths in risk classes I-III: a measure of quality of care in patients hospitalised with CAP?

All deaths occurring in patients with community-acquired pneumonia in risk classes I-III were reviewed as a quality-of-care measure. The immediate and underlying causes of death were classified according to the World Health Organization protocol. Eleven (1.8%) of the 608 low-risk patients died. Three of the patients did not have pneumonia, one of whom was admitted with atypical pulmonary oedema due to stenosis of a prosthetic heart valve. Failure to include chronic lung disease in the severity-of-illness scoring system resulted in misclassification of seven patients. The most common underlying causes of death were pulmonary fibrosis at 27%, chronic obstructive lung disease at 18% and cancer at 27%. Respiratory failure was the immediate cause of death in 64% of patients, cardiac causes in 27%, and pneumonia in 9%. To conclude, the review of deaths in patients at low risk for mortality is useful for monitoring the quality of care received by patients who require admission for the treatment of community-acquired pneumonia, and that the pneumonia-specific severity-of-illness scoring system results in misclassification of patients with chronic obstructive lung disease and pulmonary fibrosis.

Utility of blood cultures in the management of adults with community acquired pneumonia discharged from the emergency department.

STUDY OBJECTIVE: To assess the clinical value of blood cultures (BCs) in the management of adult patients discharged from the emergency department (ED) with a diagnosis of community acquired pneumonia (CAP). METHODS: The courses of antibiotic regimens and outcomes of patients with positive BC results were examined to assess their influence on BCs. RESULTS: BCs were obtained from 289 outpatients. Six clinically significant organisms were identified (a yield of 2.1%). Outpatients with CAP who had blood cultures performed had a 0.69% (2 of 289) chance of having a change of treatment directed by the results of the culture. CONCLUSION: BCs have little utility in the ambulatory management of CAP.

Mortality during hospitalisation for pneumonia in Alberta, Canada, is associated with physician volume.

The association of mortality with patient factors (severity of illness, comorbidity), physician factors (specialty training, prehospitalisation visit, in-hospital consultation, volume of patients seen per physician) and healthcare organisation factors (patient-travel distances, regional beds per capita, admitting hospital-bed occupancy, admitting hospital-bed turnover, hospital location, volume of pneumonia cases per hospital) after hospital admission with community-acquired pneumonia was investigated using administrative data from Alberta, Canada from April 1, 1994-March 31, 1999. During the 5-yr study period there were 43,642 pneumonia hospitalisations, with an 11% in-hospital and 26% 1-yr mortality. Patient severity of illness and comorbidity were the strongest predictors of increased mortality. Physicians with the highest in-hospital pneumonia patient volume (>27 patients x yr(-1)) cared for patients with greater severity/comorbidity, but with decreased odds of in-hospital mortality, compared with the lowest volume physicians (less than seven patients per year). The effects of internal medicine specialist or subspecialist care were mixed, with a reduction in deaths for the first 72 h and an increase in in-hospital deaths. Prehospitalisation visit by a physician was associated with decreased mortality. Healthcare organisation factors were the least strong predictor of mortality, demonstrating an effect only for 1-yr mortality in those discharged alive from hospital. Admissions to larger volume or metropolitan hospitals were associated with a decrease in mortality. Severity of illness and comorbidity had the strongest association with mortality. The first association of high-volume physician and pre-hospital care with decreased in-hospital mortality for community-acquired pneumonia is reported.

The effect of C. burnetii infection on the quality of life of patients following an outbreak of Q fever.

Sixty-six cases of Q fever were diagnosed in people affiliated with a goat-farming co-operative in rural Newfoundland in the spring of 1999. Follow-up studies which included administration of the Short Form 36 Health Survey (SF-36) were conducted 3 and 27 months after the initial outbreak to prospectively follow the effects of acute Q fever on the quality of life of the participants. Twenty-seven months after the outbreak 51% of those who had Q fever reported persistent symptoms including seven participants whose symptoms had initially resolved 3 months after the outbreak. Individuals with Q fever had significantly lower scores on five of the eight scales in the SF-36 and lower scores in the mental and physical summary scales compared to uninfected controls. Although this supports the hypothesis of a 'post Q fever fatigue syndrome' (QFFS), further study is warranted.

Chlamydia species as a cause of community-acquired pneumonia in Canada.

Chlamydia pneumoniae has been implicated as a cause of community-acquired pneumonia (CAP) in several studies. However, there has been no comprehensive study of the role of Chlamydia species (C. pneumoniae, C. psittaci (avian and feline strains) and C. pecorum) as a cause of CAP. The aim of the present study was to determine the role of C. pneumoniae, C. psittaci and C. pecorum as causes of CAP. A prospective cohort observational study of CAP was conducted at 15 teaching centres in eight Canadian provinces between January 1996-October 1997. Acute (n=539) and convalescent (n=272) serum samples were obtained for determination of antibody titres to C. pneumoniae, C. psittaci, C. pecorum, C. trachomatis, Mycoplasma pneumoniae, Legionella pneumophila serogroups I-VI, Streptococcus pneumoniae and various respiratory viruses. Twelve of 539 (2.2%) patients had acute C. pneumoniae pneumonia and an additional 32 (5.9%) had possible acute infection. C. pneumoniae was the sole pathogen in 16 of 42 (38.1%) of these patients. The most common copathogens were S. pneumoniae, respiratory syncytial virus and influenza virus type A. C. pneumoniae pneumonia patients were older and more likely to show congestive heart failure compared to bacteraemic S. pneumoniae patients. The latter had a lower mean diastolic blood pressure, a higher white blood cell count and a lower arterial carbon dioxide tension. Two patients had antibody titres suggestive of recent infection with the feline strain of C. psittaci. Although numerically Chlamydia pneumoniae is an important cause of community-acquired pneumonia, no distinctive clinical features associated with this pathogen were detected in the present study. Feline Chlamydia psittaci may cause a few cases of community-acquired pneumonia. Avian Chlamydia psittaci should be considered only if there is a compatible epidemiological history.