Implications for macrolide treatment in community-acquired pneumonia. Hopkins CAP Team

Beta-lactam versus beta- lactam/macrolide therapy in pediatric outpatient pneumonia

OBJECTIVE

The objective was to evaluate the comparative effectiveness of beta-lactam monotherapy and beta- lactam/macrolide combination therapy in the outpatient management of children with community-acquired pneumonia (CAP).

METHODS

This retrospective cohort study included children, ages 1-18 years, with CAP diagnosed between January 1, 2008 and January 31, 2010 during outpatient management in the Geisinger Health System. The primary exposure was receipt of beta-lactam monotherapy or beta-lactam/macrolide combination therapy. The primary outcome was treatment failure, defined as a follow-up visit within 14 days of diagnosis resulting in a change in antibiotic therapy. Logistic regression within a propensity score- restricted cohort was used to estimate the likelihood of treatment failure.

RESULTS

Of 717 children in the analytical cohort, 570 (79.4%) received beta-lactam monotherapy and 147 (20.1%) received combination therapy. Of those who received combination therapy 58.2% of children were under 6 years of age. Treatment failure occurred in 55 (7.7%) children, including in 8.1% of monotherapy recipients, and 6.1% of combination therapy recipients. Treatment failure rates were highest in children 6-18 years receiving monotherapy (12.9%) and lowest in children 6-18 years receiving combination therapy (4.0%). Children 6-18 years of age who received combination therapy were less likely to fail treatment than those who received beta-lactam monotherapy (propensity-adjusted odds ratio, 0.51; 95% confidence interval, 0.28, 0.95).

CONCLUSION

Children 6-18 years of age who received beta- lactam/macrolide combination therapy for CAP in the outpatient setting had lower odds of treatment failure compared with those who received beta-lactam monotherapy.

Extended release amoxicillin/clavulanate: optimizing a product for respiratory infections based on pharmacodynamic principles

Acute bacterial respiratory tract infections cause a great deal of human morbidity and mortality. Treatment guidelines for these infections include macrolides, doxycycline, beta-lactams and beta-lactam/beta-lactamase inhibitor combinations such as amoxicillin/clavulanic acid to provide coverage for the common respiratory pathogens, including penicillin and macrolide nonsusceptible Streptococcus pneumoniae, as well as beta-lactamase-producing Haemophilus influenzae and Moraxella catarrhalis. In response to recent guidelines recommending higher dose amoxicillin to extend coverage to a higher percentage of S. pneumoniae, a new formulation of amoxicillin/clavulanic acid was developed. This formulation includes a higher amoxicillin dose, with part of the amoxicillin dose being in an extended release formulation, without increasing the clavulanate dose, for twice-daily oral treatment of these infections. Clinical studies of community-acquired pneumonia and acute rhinosinusitis have shown that the new formulation is well tolerated and highly efficacious, with clinical outcomes equivalent to comparators.

Pediatric respiratory infections by Mycoplasma pneumoniae

Mycoplasma pneumoniae is one of the most common agents of community-acquired pneumonia in children and young adults. Although M. pneumoniae is a small bacterium that can reproduce in an artificial culture medium and is known to be sensitive to certain antibiotics in vitro as well as in vivo, the immunopathogenesis of M. pneumoniae in the human host is not fully understood. The epidemiologic characteristics, including periodic epidemics, and some clinical characteristics of M. pneumoniae are similar to those observed in systemic viral infections. Many experimental and clinical studies have suggested that the pathogenesis of lung injuries in M. pneumoniae infection is associated with a cell-mediated immune reaction, including high responsiveness to corticosteroid therapy. This paper presents an overview of M. pneumoniae infections, with emphasis on epidemiology, pathogenesis and treatment.

Seroprevalence of Mycoplasma pneumoniae in HIV-infected patients using a microparticle agglutination test

Mycoplasma pneumoniae is increasingly recognized as a common and important pathogen in community settings, and is responsible for various pulmonary and extrapulmonary conditions in the normal population. However, the seroepidemiology of acute M. pneumoniae infection in HIV-infected individuals is still unclear worldwide. This study examined the seroprevalence of antibodies to M. pneumoniae in HIV-infected patients admitted with respiratory complaints at a tertiary AIDS care centre in Chennai, India. A commercial gelatin microparticle agglutination test (Serodia-Myco II, Fujirebio) was used for the determination of antibodies against M. pneumoniae in acute serum specimens. Of the 200 HIV-infected patients with underlying pulmonary conditions tested, 34 (17 % positivity; 95 % CI 12-23 %) had antibodies specific to M. pneumoniae, while among the 40 patients with no underlying pulmonary symptoms, five (12.5 % positivity; 95 % CI 4-27 %) had evidence of anti-M. pneumoniae antibody. This shows that the incidence of M. pneumoniae seropositivity is greater in patients with underlying pulmonary complaints. Most positive titres were found in the age group 28-37 years in the symptomatic and symptom-free groups (64.7 and 60 %, respectively). The positive titres ranged from 40 to >20 480. High titres (> or =320) were found in 10 out of the 39 patients (25.6 %). This seroprevalence study reports a 16.2 % prevalence of M. pneumoniae infections in HIV-infected patients by a particle agglutination test.

Routine use of pleural fluid cultures. Are they indicated? Limited yield, minimal impact on treatment decisions

In pleural infection, it has been recommended that Gram stain and cultures should be obtained on a routine basis. However, this recommendation has not been tested prospectively. We evaluated the yield of microbiological studies in 259 patients with parapneumonic pleural effusion. Microbiological studies were positive on the pleural fluid of 50 patients (19.3%). In 48 of the 50 patients with positive microbiological results (96%), the need for pleural drainage was correctly predicted by pleural fluid parameters. There were no differences in hospital stay (9.5+/-2.5 days versus 9.9+/-3.2 days, P=0.68) or in mortality (2 deaths in each group, P=0.58) between the group of patients in which antibiotic treatment was changed according to microbiological results and the group of patients in which it is not. In conclusion, this study demonstrates that, at least in our institution, routine microbial investigation of pleural fluid adds very little to the standard management of parapneumonic effusions.

Comparison between pathogen directed antibiotic treatment and empirical broad spectrum antibiotic treatment in patients with community acquired pneumonia: a prospective randomised study

BACKGROUND

There is much controversy about the ideal approach to the management of community acquired pneumonia (CAP). Recommendations differ from a pathogen directed approach to an empirical strategy with broad spectrum antibiotics.

METHODS

In a prospective randomised open study performed between 1998 and 2000, a pathogen directed treatment (PDT) approach was compared with an empirical broad spectrum antibiotic treatment (EAT) strategy according to the ATS guidelines of 1993 in 262 hospitalised patients with CAP. Clinical efficacy was primarily determined by the length of hospital stay (LOS). Secondary outcome parameters for clinical efficacy were assessment of therapeutic failure on antibiotics, 30 day mortality, duration of antibiotic treatment, resolution of fever, side effects, and quality of life.

RESULTS

Three hundred and three patients were enrolled in the study; 41 were excluded, leaving 262 with results available for analysis. No significant differences were found between the two treatment groups in LOS, 30 day mortality, clinical failure, or resolution of fever. Side effects, although they did not have a significant influence on the outcome parameters, occurred more frequently in patients in the EAT group than in those in the PDT group (60% v 17%, 95% CI -0.5 to -0.3; p<0.001).

CONCLUSIONS

An EAT strategy with broad spectrum antibiotics for the management of hospitalised patients with CAP has comparable clinical efficacy to a PDT approach.

Value of intensive diagnostic microbiological investigation in low- and high-risk patients with community-acquired pneumonia

In a prospective study to evaluate the diagnostic yield of different microbiological tests in hospitalised patients with community-acquired pneumonia, material for microbiological investigation was obtained from 262 patients. Clinical samples consisted of the following: sputum for Gram staining, culture, and detection of pneumococcal antigen; blood for culture and serological tests; urine for detection of Legionella pneumophila serogroup 1 antigen and pneumococcal antigen; and specimens obtained by fiberoptic bronchoscopy. A pathogen was identified in 158 (60%) patients, with Streptococcus pneumoniae (n=97) being the most common causative agent of community-acquired pneumonia. In 82% of the 44 patients with an adequate sputum specimen, a positive Gram stain was confirmed by positive sputum culture. S. pneumoniae infections were detected principally when adequate sputum specimens were examined by Gram stain and culture and when adequate and inadequate sputum specimens were tested for the presence of pneumococcal antigen (n=58; 60%). The urinary pneumococcal antigen test was the most valuable single test for detection of S. pneumoniae infections (n=52; 54%) when sputum pneumococcal antigen determination was not performed. Fiberoptic bronchoscopy was of additive diagnostic value in 49% of the patients who did not expectorate sputum and in 52% of those in whom treatment failed. Investigation of sputum by a combination of Gram stain, culture, and detection of pneumococcal antigen was the most useful means of establishing an aetiological diagnosis of community-acquired pneumonia, followed by testing of urine for pneumococcal antigen. Fiberoptic bronchoscopy may be of additional value when treatment failure occurs.

Monotherapy versus combination antimicrobial therapy for pneumococcal pneumonia

PURPOSE OF REVIEW

In the past 5 years a number of studies have suggested that combination antibiotic therapy may be superior to monotherapy for pneumococcal pneumonia. This review outlines the major findings for and against combination therapy.

RECENT FINDINGS

The evidence for a benefit of multiple antibiotics is strongest in patients with severe, bacteremic pneumococcal disease. All of these studies have limitations due to their retrospective or uncontrolled design. Unfortunately prospective, randomized, double-blind, controlled studies have not been performed in an appropriately severe disease cohort and are therefore urgently needed. Several viable mechanisms for a benefit of combination therapy have been proposed, especially related to non-antibiotic effects of macrolides. There is also some evidence that third-generation cephalosporins may be superior to penicillins as the non-macrolide component of combination therapy.

SUMMARY

Although based on retrospective and observational data, there is substantial evidence to support combination antibiotic therapy, at least in patients with severe bacteremic pneumococcal pneumonia. What evidence is available supports a cephalosporin/macrolide combination as being associated with the highest survival, but proper prospective studies in patients with severe pneumonia are urgently required to clarify this issue.

Lower mortality among patients with community-acquired pneumonia treated with a macrolide plus a beta-lactam agent versus a beta-lactam agent alone

A cohort of 1,391 patients with community-acquired pneumonia of unknown etiology, atypical pneumonia, Legionella pneumophila pneumonia, viral pneumonia, or pneumococcal pneumonia was studied according to a standard protocol to analyse whether the addition of a macrolide to beta-lactam empirical treatment decreases mortality rates. Patients admitted to the intensive care unit were excluded. Severity was assessed using the PORT score. An etiological diagnosis was achieved in 498 (35.8%) patients (292 infections due to Streptococcus pneumoniae). Treatment was chosen by the attending physician according to his/her own criteria: beta-lactam agent in 270 and beta-lactam agent plus a macrolide in 918 cases. The mortality rate was 13.3% in the group treated with a beta-lactam agent alone and 6.9% in the group treated with a beta-lactam agent plus a macrolide (p=0.001). The percentage of PORT-group V patients was 32.6% in the group treated with a beta-lactam agent alone compared to 25.7% in the group who received a beta-lactam agent plus a macrolide (p=0.02). After controlling for PORT score, the odds of fatal outcome was two times higher in patients treated with a beta-lactam agent alone than in those treated with a beta-lactam agent plus a macrolide (adjusted OR = 2, 95%CI 1.24-3.23). The results suggest that the addition of a macrolide to an initial beta-lactam-based antibiotic regimen is associated with lower mortality in patients with community-acquired pneumonia, independent of severity of infection, thus supporting the recommendation of a beta-lactam-agent plus a macrolide as empirical therapy.

Effectiveness of beta lactam antibiotics compared with antibiotics active against atypical pathogens in non-severe community acquired pneumonia: meta-analysis

OBJECTIVE

To systematically compare beta lactam antibiotics with antibiotics active against atypical pathogens in the management of community acquired pneumonia.

DATA SOURCES

Medline, Embase, Cochrane register of controlled trials, international conference proceedings, drug registration authorities, and pharmaceutical companies. Review methods Double blind randomised controlled monotherapy trials comparing beta lactam antibiotics with antibiotics active against atypical pathogens in adults with community acquired pneumonia. Primary outcome was failure to achieve clinical cure or improvement.

RESULTS

18 trials totalling 6749 participants were identified, with most patients having mild to moderate community acquired pneumonia. The summary relative risk for treatment failure in all cause community acquired pneumonia showed no advantage of antibiotics active against atypical pathogens over beta lactam antibiotics (0.97, 95% confidence interval 0.87 to 1.07). Subgroup analysis was undertaken in those with a specific diagnosis involving atypical pathogens. We found a significantly lower failure rate in patients with Legionella species who were treated with antibiotics active against atypical pathogens (0.40, 0.19 to 0.85). Equivalence was seen for Mycoplasma pneumoniae (0.60, 0.31 to 1.17) and Chlamydia pneumoniae (2.32, 0.67 to 8.03).

CONCLUSIONS

Evidence is lacking that clinical outcomes are improved by using antibiotics active against atypical pathogens in all cause non-severe community acquired pneumonia. Although such antibiotics were superior in the management of patients later shown to have legionella related pneumonia, this pathogen was rarely responsible for pneumonia within the included trials. beta lactam agents should remain the antibiotics of initial choice in adults with non-severe community acquired pneumonia.

Role of beta-lactam agents in the treatment of community-acquired pneumonia

Community-acquired pneumonia (CAP) is a common illness associated with high rates of morbidity and mortality worldwide. The beta-lactam antibacterial agents have been the mainstay of therapy for CAP for over four decades and remain as first-line therapy. However, the impact of the substantial prevalence of resistance seen among the common respiratory pathogens, particularly penicillin and macrolide resistance among Streptococcus pneumoniae, is now an area for concern. CAP treatment guidelines often recommend the use of a macrolide or fluoroquinolone in conjunction with, or as an alternative to, beta-lactam agents, but whether this is necessary is uncertain. This review outlines the historical use of beta-lactam antibacterial agents in the treatment of CAP along with their ongoing therapeutic utility.

Diagnostic test for etiologic agents of community-acquired pneumonia

Diagnostic tests for the detection of the etiologic agent of pneumonia are neither recommended nor done for most outpatients with CAP (Table 4).Most of these patients have no clear diagnosis but seem to do well with empiric antibiotic treatment, which often costs less than the diagnostic tests. For hospitalized patients, a pre-treatment blood culture and an expectorated sputum gram stain and culture should be done. Testing for Legionella spp is appropriate in hospitalized patients, especially those who are seriously ill. New tests that merit use in selected patients are the urinary antigen assay for S pneumoniae and the PCR test for L pneumophila. Anticipated developments in the near future are PCR tests for detection of C pneumoniae and M pneumoniae.

Guidelines for community-acquired pneumonia: are they reflected in practice?

Community-acquired pneumonia (CAP) is common, costly, and clinically serious. Several national and international practice guidelines have been developed to promote more appropriate, cost-effective care for patients with CAP. This article compares and contrasts eight international practice guidelines for the management of CAP, describes the extent to which recommendations are reflected in practice, and proposes explanations for non-adherence to guidelines. We found consistency in recommendations across all the guidelines for the management of patients with CAP requiring intensive care. In this setting, all guidelines recommend chest radiography, sputum Gram stain and culture, blood cultures, testing for Legionella pneumophila, and timely administration of antibiotics active against both typical (i.e. Streptococcus pneumoniae, Hemophilus influenzae) and atypical organisms (i.e. Legionella spp., Mycoplasma pneumoniae, and Chlamydia pneumoniae). Recommendations for the management of the average inpatient with pneumonia were more variable, with the greatest differences between the North American and European guidelines. The North American guidelines (in contrast to European ones), recommended empiric treatment of typical and atypical organisms in all inpatients. There were also differences in policies regarding the necessity of chest radiography, sputum studies, and serologic testing. Some guidelines explicitly embrace the use of prediction rules to inform the decision to hospitalize, while others do not. Some of these admission decision algorithms focus on identifying low risk patients, while others are most concerned with high risk patients. There was also considerable variation in the specificity and operationalization of clinical criteria for switching from parenteral to oral antibiotics or judging appropriateness for discharge. Many recommendations for key management decisions tended to lack explicit, objective, and actionable criteria that could be easily implemented in real world practice. Review of the pneumonia literature revealed that physician performance of guideline-recommended best practices is often suboptimal. Administration of timely antibiotics (< or =8 hours of presentation) and use of first-line antibiotics occurred in 75-85% and 18-79% of cases, respectively. Collection of blood cultures within 24 hours of presentation and prior to administration of antibiotics was achieved in 69-83% and 63-82% of cases, respectively. Screening the eligibility of CAP patients for hospital-based pneumococcal and influenza vaccination occurred on average in 11 and 14% of hospitalizations, respectively, in the US. Lack of awareness of guidelines, conflicting advice among them, and lack of specific, objective, actionable recommendations most likely contribute to nonadherence to CAP guidelines. Increased attention to these factors will be needed if professional society practice guidelines are to fulfill their promise as tools for improving the quality and outcomes of care for patients with pneumonia.

Evolution of amoxicillin/clavulanate in the treatment of adults with acute bacterial rhinosinusitis and community-acquired pneumonia in response to antimicrobial-resistance patterns

Current treatment guidelines for community-acquired respiratory tract infections no longer depend solely on the characteristics of the patient and the clinical syndrome, but on those of the offending pathogen, including presence and level of antimicrobial resistance. The most common respiratory tract pathogens known to cause acute bacterial rhinosinusitis (ABRS) and community-acquired pneumonia (CAP) include Streptococcus pneumoniae and Haemophilus influenzae. The prevalence of antimicrobial resistance, especially b-lactum and macrolide resistance, among S pneumoniae and H influenzae has increased dramatically during the past 2 decades, diminishing the activity of many older antimicrobials against resistant organisms. A pharmacokinetically enhanced formulation of amoxicillin/clavulanate has been developed to fulfill the need for an oral b-lactam antimicrobial that achieves a greater time that the serum drug concentration exceeds the minimum inhibitory concentration (T > MIC) of antimicrobials against pathogens than conventional formulations to improve activity against S pneumoniae with reduced susceptibility to penicillin. The b-lactamase inhibitor clavulanate allows for coverage of b-lactamase-producing pathogens, such as H influenzae and M catarrhalis. This article reviews the rationale for, and evolution of, oral amoxicillin clavulanate for ABRS and CAP

Monotherapy versus Dual Therapy for Community-Acquired Pneumonia in Hospitalized Patients

Several medical-specialty professional societies have suggested that combination therapy with a beta -lactam plus a macrolide or doxycycline or monotherapy with a "respiratory quinolone" (i.e., levofloxacin, gatifloxacin, moxifloxacin, or gemifloxacin) are optimal first-line therapy for patients hospitalized with community-acquired pneumonia. These recommendations are based predominantly on retrospective studies that suggest improved rates of morbidity and mortality and hospital length of stay among patients treated in such a fashion. Well-designed, prospective, randomized studies confirming this tenet of therapy have not been published, although numerous prospective studies have provided indirect confirmation. The biological rationale for such a differential response (i.e., favoring combination therapy or fluoroquinolone therapy) includes the immunomodulatory effects of macrolides or more-optimal treatment of primary infection or coinfection with atypical pathogens. Well-designed, prospective, randomized trials are required to best define the effectiveness of combination therapy with a beta -lactam plus macrolide or doxycycline or with a respiratory quinolone in hospitalized patients with community-acquired pneumonia.

Guidelines for Empiric Antimicrobial Prescribing in Community-Acquired Pneumonia

Empiric antimicrobial prescribing for community-acquired pneumonia remains a challenge, despite the availability of treatment guidelines. A number of key differences exist between North American and European guidelines, mainly in the outpatient setting. The North American approach is to use initial antimicrobial therapy, which provides coverage for Streptococcus pneumoniae plus atypical pathogens. Europeans tend to focus on providing pneumococcal coverage with less emphasis on covering for an atypical pathogen. Ambulatory patients without comorbidity are more likely to receive macrolide therapy in North America, whereas in Europe these patients would probably receive a beta-lactam agent. Major issues that are fundamental to this difference include the importance of providing therapy for atypical pathogens and the clinical significance of macrolide-resistant S pneumoniae. Prospective data are required to evaluate which of these two approaches offers clinical superiority.

Impact of Atypical Coverage for Patients with Community-Acquired Pneumonia Managed on the Medical Ward: Results from the United States Community-Acquired Pneumonia Project

STUDY OBJECTIVE

As current guidelines for treatment of community-acquired pneumonia (CAP) recommend empiric antimicrobial coverage for atypical pathogens, we evaluated the need for atypical coverage by examining length of hospital stay (LOS) and mortality in patients with CAP who were managed on the medical ward.

METHODS

Medical records of patients with CAP admitted from January 1, 1997-December 31, 2001, from 176 United States nonteaching community hospitals were reviewed. Patients were divided into one of three mutually exclusive groups on the basis of intravenous antimicrobials received on days 1 or 2 of hospital stay: ceftriaxone monotherapy, ceftriaxone plus a macrolide, or levofloxacin. Variables evaluated for their ability to predict outcome were patient age, year of hospital admission, geographic region, preadmission setting, preadmission antimicrobial treatment, timing of antimicrobial administration, comorbid disease, and duration of intravenous antimicrobial treatment. The impact of initial antimicrobial regimen on LOS and mortality was evaluated in regression models while controlling for significant predictors of outcome.

RESULTS

Of 8975 patients evaluated, 2453 met the inclusion criteria. Significant differences were noted among patients who received ceftriaxone (932 patients), ceftriaxone plus a macrolide (872), and levofloxacin (649) with respect to mean +/- SD age (72 +/- 16, 67 +/- 18, and 70 +/- 17 yrs, respectively; p<0.0001), admission from a nursing home (21%, 11%, and 15%, respectively; p<0.0001), and duration of intravenous antimicrobial treatment (4.4 +/- 2.7, 4.0 +/- 2.6, and 3.6 +/- 2.5 days, respectively; p<0.0001). The LOS predictors were age, geographic region, coexisting heart failure, and duration of intravenous antimicrobial therapy. Mortality predictors were age, admission from a nursing home, coexisting heart failure, and coexisting cancer. After controlling for these predictors of outcome, no significant differences were noted among the three groups for LOS (5.5 +/- 3.5, 4.8 +/- 2.9, and 4.8 +/- 2.9 days, respectively; p=0.2791) or mortality (3.1%, 2.0%, and 2.6%, respectively; p=0.8461).

CONCLUSION

Initial coverage for atypical pathogens does not affect LOS or mortality among patients with CAP managed on the medical ward.

Moraxella catarrhalis bacteraemia associated with Mycoplasma pneumoniae infection and pneumonia

This report describes a case of severe pneumonia associated with Mycoplasma pneumoniae infection and Moraxella catarrhalis bacteraemia in a 44-y-old woman with undiagnosed breast carcinoma. M. pneumoniae is increasingly recognized as a co-pathogen but to the authors' knowledge this is the first reported case of M. catarrhalis bacteraemia associated with M. pneumoniae infection.

International guidelines for the treatment of community-acquired pneumonia in adults: the role of macrolides

The significance of community-acquired pneumonia (CAP) has led to the publication of guidelines from numerous international organisations. Because the macrolide class of antimicrobials is active against most of the key pathogens associated with CAP, agents from this class are commonly included in recommendations from these guidelines. However, there are differences among the various guidelines concerning the positioning of the macrolides for empirical therapy. An important factor concerning the use of macrolides for CAP is the emergence of resistance of Streptococcus pneumoniae over the past decade. The rate of S. pneumoniae resistance to macrolides ranges from 4 to 70% of strains in worldwide surveillance studies. The most common mechanisms of resistance include methylation of a ribosomal target encoded by the erm gene and efflux of the macrolides by a cell membrane protein transporter, encoded by the mef gene. S. pneumoniae strains with the mef gene are resistant at a lower level (with minimum inhibitory concentration [MIC] values generally 1-16 microg/ml) than erm resistant strains; and it is possible that such strains may be inhibited if sufficiently high levels of macrolide can be obtained at the infected site. Currently mef-associated resistance predominates in North America, whereas erm predominates in Europe. Until recently, reports of failure of treatment of CAP with macrolides has been rare, particularly for patients with low-risk for drug-resistant strains. However, since 2000, several patients treated with an oral macrolide who have subsequently required admission to the hospital for macrolide-resistant S. pneumoniae (MRSP) bacteraemia have been reported in the literature. Major issues, which are fundamental to the use of the macrolides as recommended in the various guidelines, include the importance of providing therapy for 'atypical' pathogens and the clinical significance of MRSP. Presently, the macrolides are more prominently recommended in the North American guidelines than in other parts of the world. The difference in the emphasis placed on the importance of the atypical pathogens as well as the expression of MRSP in North America compared with Europe partly explains this variance.

The contribution of blood cultures to the clinical management of adult patients admitted to the hospital with community-acquired pneumonia: a prospective observational study

STUDY OBJECTIVE

To assess the clinical usefulness of blood cultures (BCs) in the management of patients hospitalized with community-acquired pneumonia (CAP).

DESIGN

A prospective, observational study to investigate the contribution of BCs to the management and outcomes of adult patients presenting with CAP.

SETTING

Nineteen Canadian hospitals.

PATIENTS

Adults admitted to the hospital with CAP between January 1, 1998, and July 31, 1998.

INTERVENTIONS

The courses of therapy in patients for whom BC results yielded organisms considered to be clinically significant were analyzed to determine whether the BCs had contributed to management or outcome.

MEASUREMENTS AND RESULTS

Forty-three of 760 patients had significantly positive BC results. Patients with CAP who had BCs performed had a 1.97% chance (15 of 760 patients) of having a change of therapy directed by BC results. Patients in whom BCs yielded positive results had a 34.8% chance (15 of 43 patients) of having a change in therapy determined by BC results, and had a 58.1% chance (25 of 43 patients) of having a course of therapy contraindicated by BC results. Severity of illness, as measured by the pneumonia severity index, correlated poorly with the yield of BCs. BC results were positive in 8.0% of patients in risk classes I and II, 6.2% of patients in risk class III, 4.6% of patients in risk class IV, and 5.2% of patients in risk class V.

CONCLUSION

BCs have limited usefulness in the routine management of patients admitted to the hospital with uncomplicated CAP.

Addition of a macrolide to a beta-lactam-based empirical antibiotic regimen is associated with lower in-hospital mortality for patients with bacteremic pneumococcal pneumonia

To assess the association between inclusion of a macrolide in a beta-lactam-based empirical antibiotic regimen and mortality among patients with bacteremic pneumococcal pneumonia, 10 years of data from a database were analyzed. The total available set of putative prognostic factors was subjected to stepwise logistic regression, with in-hospital death as the dependent variable. Of the 409 patients analyzed, 238 (58%) received a beta-lactam plus a macrolide and 171 (42%) received a beta-lactam without a macrolide. Multivariate analysis revealed 4 variables to be independently associated with death: shock (P<.0001), age of >or=65 years (P=.02), infections with pathogens that have resistance to both penicillin and erythromycin (P=.04), and no inclusion of a macrolide in the initial antibiotic regimen (P=.03). For patients with bacteremic pneumococcal pneumonia, not adding a macrolide to a beta-lactam-based initial antibiotic regimen is an independent predictor of in-hospital mortality. However, only a randomized study can definitively determine whether this association is due to a real effect of macrolides.

The efficacy and safety of oral pharmacokinetically enhanced amoxycillin–clavulanate 2000/125 mg, twice daily, versus oral amoxycillin–clavulanate 1000/125 mg, three times daily, for the treatment of bacterial community-acquired pneumonia in adults

This double-blind, double-dummy, parallel-group study was designed to show that a pharmacokinetically enhanced formulation of oral amoxycillin-clavulanate (16:1, 2000/125 mg), twice daily, is at least as effective clinically and microbiologically as oral amoxycillin-clavulanate 1000/125 mg, three times daily, in the 10 day treatment of community-acquired pneumonia (CAP) in adults. The pharmacokinetically enhanced formulation is designed to provide higher serum concentrations of amoxycillin for a longer period than standard dosing to achieve coverage of Streptococcus pneumoniae isolates with amoxycillin-clavulanic acid minimum inhibitory concentrations (MICs) up to and including 4 mg/l. A total of 344 patients with CAP from 77 centres received amoxycillin-clavulanate 2000/125 mg twice daily for 10 days (169 patients) or amoxycillin-clavulanate 1000/125 mg three times daily for 10 days (175 patients). The most common pathogen isolated was S. pneumoniae (52.3% of patients, amoxycillin-clavulanate 2000/125 mg group; 46.8% of patients, amoxycillin-clavulanate 1000/125 mg group). In the clinical per-protocol (PP) population at test of cure (days 18-39), the clinical success rate in the amoxycillin-clavulanate 2000/125 mg group was at least as good as in the amoxycillin-clavulanate 1000/125 mg group (91.5 and 93.0%, respectively; 95% CI, -8.3, 5.4). The radiological and bacteriological success rates at test of cure for the PP populations were 92.4 and 90.6% in the amoxycillin-clavulanate 2000/125 mg group and 93.9 and 84.4% in the amoxycillin-clavulanate 1000/125 mg group, respectively. The clinical, bacteriological and radiological success rates at the end of therapy (days 11-17) for the PP populations were all over 85%. Both regimens were well tolerated, with no differences in adverse events between the groups. Amoxycillin-clavulanate 2000/125 mg, twice daily, is well tolerated and at least as effective clinically as amoxycillin-clavulanate 1000/125 mg, three times daily, in patients with CAP and may also be appropriate for the treatment of infections due to S. pneumoniae strains with high-level penicillin resistance.

Clinical relevance of macrolide-resistant Streptococcus pneumoniae for community-acquired pneumonia

Macrolides are often the first choice for empirical treatment of community-acquired pneumonia. However, macrolide resistance among Streptococcus pneumoniae has escalated at alarming rates in North America and worldwide. Macrolide resistance among pneumococci is primarily due to genetic mutations affecting the ribosomal target site (ermAM) or active drug efflux (mefE). Prior antibiotic exposure is the major risk factor for amplification and perpetuation of resistance. Clonal spread facilitates dissemination of drug-resistant strains. Data assessing the impact of macrolide resistance on clinical outcomes are spare. Many experts believe that the clinical impact is limited. Ribosomal mutations confer high-grade resistance, whereas efflux mutations can likely be overridden in vivo. Favorable pharmacokinetics and pharmacodynamics, high concentrations at sites of infections, and additional properties of macrolides may enhance their efficacy. In this article, we discuss the prevalence of macrolide resistance among S. pneumoniae, risk factors and mechanisms responsible for resistance, therapeutic strategies, and implications for the future.

The emerging role of atypical pathogens in community-acquired pneumonia

Community-acquired pneumonia (CAP) constitutes a major cause of morbidity and mortality. Although Streptococcus pneumoniae remains the bacterium most commonly implicated in CAP, the atypical respiratory pathogens Mycoplasma pneumoniae, Legionella species, and Chlamydia pneumoniae are being isolated with increasing frequency Contrary to previous beliefs, these agents are capable of causing severe as well as mild-to-moderate illness. Moreover, they can affect all age groups. Indeed, atypical pathogens are implicated in up to 40% of CAP cases and commonly occur as copathogens in mixed-infection CAP, an etiology associated with particularly high mortality (up to 25%). Laboratory methods for detecting atypical pathogens are slow, and there is significant overlap between atypical and typical CAP manifestations. For these reasons, accurate prediction of etiology cannot be made purely on clinical or radiologic grounds. Consequently, empiric antimicrobial therapy for atypical pathogens (with agents such as macrolides, fluoroquinolones, in some cases tetracyclines, or the new ketolides) warrants careful consideration and now is recommended for the treatment of CAP.

The role of atypical pathogens in community-acquired pneumonia

The atypical pathogens in community-acquired pneumonia traditionally have included Mycoplasma pneumoniae, Chlamydia pneumoniae, and Legionella spp. Recent studies documenting their epidemiology and clinical characteristics have shown that these organisms are indistinguishable from the pneumococcus. Furthermore, therapy no longer depends on the specific bacterial cause of community-acquired pneumonia. Etiologic diagnosis is still difficult, although new methods are becoming available. This article focuses on these issues and on why the term atypical is no longer meaningful.

Evaluation of the Winthrop-University Hospital criteria to identify Legionella pneumonia

STUDY OBJECTIVE

To measure the ability of a set of clinical parameters, the Winthrop-University Hospital (WUH) criteria, to identify Legionella pneumonia while discriminating against bacteremic pneumococcal pneumonia at the time of hospitalization for community-acquired pneumonia (CAP).

DESIGN

Retrospective case-control study.

SETTING

An urban county hospital and a tertiary-care Veterans Affairs hospital.

PATIENTS

Thirty-seven patients with Legionella pneumonia (diagnosed by a positive result of a urinary Legionella antigen test) and 31 patients with bacteremic pneumococcal pneumonia. A subgroup of patients with all required laboratory criteria were studied further.

RESULTS

The WUH criteria correctly identified 29 of 37 patients with Legionella pneumonia (sensitivity, 78%; 95% confidence interval [CI], 61 to 90%), while successfully excluding legionellosis in 20 of 31 patients with bacteremic pneumococcal pneumonia (specificity, 65%; 95% CI, 45 to 80%). The positive and negative predictive values, adjusted for a relative prevalence of 1:3 between Legionella and Streptococcus pneumoniae bacteremia, were 42% (95% CI, 25 to 61%) and 90% (95% CI, 74 to 97%), respectively. In the subgroup analysis, the WUH criteria were successful in identifying 20 of 23 patients with Legionella pneumonia (sensitivity, 87%; 95% CI, 65 to 97%), while excluding legionellosis in 9 of 18 patients with bacteremic pneumococcal pneumonia (specificity, 50%; 95% CI, 27 to 73%). The adjusted positive and negative predictive values for a 1:3 relative prevalence were 37% (95% CI, 20 to 59%) and 92% (95% CI, 62 to 98%), respectively. The predictive values were changed in the directions expected for an increased relative prevalence of 1:1. The areas under the receiver operating characteristic curves were 0.72 +/- 0.06 for the entire study group and 0.68 +/- 0.09 for the subgroup.

CONCLUSIONS

Although the WUH criteria discriminated fairly well between cases (mean +/- SE) and control subjects, the sensitivity is not high enough to exclude legionellosis confidently. These results suggest that empiric therapy for Legionella pneumonia should be included in the initial antibiotic regimen for hospitalized patients with CAP.

Empiric antibiotic therapy and mortality among medicare pneumonia inpatients in 10 western states : 1993, 1995, and 1997

STUDY OBJECTIVES

To examine the association of empiric inpatient antibiotic treatment of community-acquired pneumonia (CAP) with mortality, and whether this association varies from year to year.

DESIGN

Population-based, retrospective study adjusting for demographics, comorbidities, and clinical characteristics.

SETTING

Acute-care hospitals in 10 western states.

PATIENTS

A group of 10,069 Medicare beneficiaries aged > or = 65 years who were hospitalized with CAP during fiscal years 1993, 1995, and 1997.

MEASUREMENTS AND RESULTS

We examined the risk for mortality during the 30 days after admission to the hospital. The impact of specific antibiotic regimens varied greatly from year to year. In 1993, therapy with a macrolide plus a beta-lactam was associated with significantly lower mortality than therapy with either a beta-lactam alone (adjusted odds ratio [AOR], 0.42; 95% confidence interval [CI], 0.25 to 0.69) or other regimens that did not include a macrolide, beta-lactam, or fluoroquinolone (AOR, 0.35; 95% CI, 0.20 to 0.62). Those associations were not observed in 1995 or 1997. Lower mortality was associated with fluoroquinolone monotherapy compared with beta-lactam monotherapy in 1997 (AOR, 0.27; 95% CI, 0.07 to 0.96) and with macrolide monotherapy compared with other regimens in 1995 (AOR, 0.24; 95% CI, 0.06 to 0.93), but the number of patients who received these regimens was small.

CONCLUSIONS

The inclusion of a macrolide or a fluoroquinolone in initial empiric CAP treatment was associated with improved survival, but this association varied from year to year, perhaps as a result of a temporal variation in the incidence of atypical pathogen pneumonia. Improved testing and surveillance for atypical pathogen pneumonia are needed to guide empiric therapy.

Etiology, reasons for hospitalization, risk classes, and outcomes of community-acquired pneumonia in patients hospitalized on the basis of conventional admission criteria

We performed an observational analysis of prospectively collected data on 533 nonseverely immunosuppressed adult patients who were hospitalized for community-acquired pneumonia on the basis of conventional admission criteria. For this population, we correlated etiology, reasons for admission, and outcomes using the Pneumonia Severity Index (PSI), to identify major discrepancies between the PSI risk class and the conventional criteria for deciding the site of care. PSI classes and corresponding mortality rates were as follows: class I, 51 patients (0%); class II, 62 (2%); class III, 117 (3%); class IV, 198 (10%); and class V, 105 (29%). We identified significant discrepancies between both methods. Overall, 230 patients (40%) who were hospitalized according to conventional criteria were assigned to low-risk classes. Of these 230 patients, 137 (60%) needed supplementary oxygen or had pleural complications; for the remaining patients, there were no irrefutable reasons for admission. This latter group deserves prospective evaluation in randomized studies that compare ambulatory and in-hospital management.

Mycoplasma pneumoniae infections

Mycoplasma pneumoniae is a frequent cause of community-acquired respiratory infections in children and adults. Although the organism is felt to be the most frequent 'atypical' pathogen responsible for community-acquired pneumonia in adults, the prevalence of M. pneumoniae varies greatly from study to study, depending on the population and the diagnostic methods used. Recent studies have found the prevalence of M. pneumoniae in adults with pneumonia to range from 1.9 to over 30%. M. pneumoniae is also a frequent cause of outbreaks of respiratory disease in institutional settings. However, the diagnosis of M. pneumoniae infection is hampered by the lack of standardized, rapid, specific methods. This problem was illustrated by the results of an investigation of an outbreak of M. pneumoniae infection in a federal training facility. Accurate diagnosis required a combination of polymerase chain reaction and serology, as IgM antibodies were not present early in the course of the infection in many patients. Several papers evaluating various serological and polymerase chain reaction assays were published during the period of this review. An assessment of the actual performance of these tests was also hampered by the lack of standardized comparative methods. M. pneumoniae is susceptible in vitro to macrolides, tetracyclines and quinolone antibiotics; however, data are limited on the microbiological efficacy of these agents. Several pneumonia treatment studies were published during this period, practically all of them based the diagnosis of M. pneumoniae infection on serology; different methods and criteria were used in each study, and thus the microbiological efficacy could not be assessed. The Infectious Disease Society of America recently stated in their revised Practice Guidelines for the Management of Community-Acquired Pneumonia in Adults that, as there were no diagnostic tests available that reliably and rapidly detect M. pneumoniae, therapy must usually be empirical.

Community-acquired pneumonia. Diagnostic and therapeutic approach

Optimal empiric therapy of CAP is with appropriate monotherapy (e.g., doxycycline, levofloxacin). Combination therapy is problematic because of potential side effects and high cost. Empiric coverage should have a high degree of activity against both typical and atypical pathogens. The antibiotic selected should have an excellent side-effect profile and be relatively inexpensive. Clinicians should be selective in their choice of antibiotic for CAP and choose an antimicrobial that has little or no resistance potential, is relatively inexpensive, and permits i.v.-to-PO switch monotherapy.

Legionella and community-acquired pneumonia: a review of current diagnostic tests from a clinician's viewpoint

Many physicians are unaware of the limitations of the available tests for diagnosing infections with Legionella organisms. Geographic differences in the importance of nonpneumophila Legionella species as pathogens are underrecognized, in part because available diagnostic tests are biased toward the detection of pneumophila serogroup 1. Routine laboratory practices reduce the likelihood of culturing Legionella species from clinical isolates. Failure of seroconversion is common, particularly with nonpneumophila species; even when seroconversion occurs, it may take much longer than 4 weeks. Urinary antigen testing has insufficient sensitivity to affect clinical management in most regions of the United States, as it can reliably detect only L. pneumophila serogroup 1 infections. Polymerase chain reaction-based techniques offer hope of providing highly sensitive, rapid diagnostic tests for all Legionella species, but limitations in the current tests will make validating them difficult.

Importance of atypical pathogens of community-acquired pneumonia

The atypical clinical presentation of patients with community-acquired pneumonia (CAP) was first recognized and reported by astute clinicians 50 years ago. The cause of pneumonia in this group eventually was shown to be Mycoplasma pneumoniae. More recently, Chlamydia pneumoniae also has been recognized as a cause of CAP. Legionella has been lumped together with M. pneumoniae and C. pneumoniae because of its antimicrobial susceptibility pattern. This group of organisms is susceptible to the macrolides, tetracycline, and the newer fluoroquinolones. However, Legionnaires' disease frequently presents a more acute clinical picture than either mycoplasmal or chlamydial infections. Recent data suggest that in the Medicare population hospitalized with pneumonia, morbidity and mortality can be decreased if initial therapy includes coverage for atypical pathogens (i.e., macrolides or fluoroquinolones). Unfortunately, few studies use culture methodology for atypical pathogens. Future studies of the efficacy of macrolide or fluoroquinolone therapy for CAP should include aggressive diagnostic studies for M. pneumoniae, C. pneumoniae, and Legionella species.

Effect of macrolides as part of initial empiric therapy on medical outcomes for hospitalized patients with community-acquired pneumonia

OBJECTIVE

The goal of this study was to compare the outcomes of hospitalized patients receiving a nonpseudomonal third-generation cephalosporin with or without a macrolide for the treatment of community-acquired pneumonia (CAP).

BACKGROUND

The initial treatment of CAP is usually based on empirically selected antibiotic therapy. The need for coverage of atypical pathogens in hospitalized patients is widely debated, and regional variations may exist.

METHODS

All patients admitted to a community hospital or to a university hospital for 1 year who were aged > or =18 years and had a principal discharge diagnosis of pneumonia with no organism specified according to the International Classification of Diseases, Ninth Revision, Clinical Modification were evaluated. Each patient's medical chart was reviewed by a clinical pharmacist at each facility. The following information was collected for each patient using a standardized form: demographic characteristics, coexisting illnesses, length of hospital and intensive care unit stays, antibiotic regimens, length of parenteral and oral therapy, laboratory and radiographic findings (ie, blood urea nitrogen, glucose, hematocrit, sodium, PO2, pH, and pleural effusion), physical examination results, and mortality. Patients treated with a nonpseudomonal third-generation cephalosporin with or without a macrolide were included in this analysis. Categoric variables were compared using the chi-square test or the Fisher exact test, and continuous variables were compared using the Mann-Whitney U test. A P value < 0.05 was considered statistically significant.

RESULTS

A total of 213 patients met the entry criteria and were treated with a nonpseudomonal third-generation cephalosporin with (116 patients) or without (97 patients) a macrolide. The mean (+/- SD) age of the patients was 62.2+/-19.6 years; 47% were male. The most common comorbid conditions were chronic obstructive pulmonary disease, diabetes mellitus, congestive heart failure, and cerebrovascular accident (CVA). Of the 116 patients who received a macrolide, the majority (66%) received erythromycin. Other macrolides used were clarithromycin (19%) and oral azithromycin (15%). There were no statistical differences between patients who did and did not receive a macrolide in terms of comorbid illnesses, length of hospital stay (5.2+/-2.8 vs 5.2+/-3.4 days, respectively), length of intravenous antibiotic therapy (4.4+/-2.5 vs 4.1+/-2.3 days, respectively), or mortality (0.9% vs 3.1%, respectively; P = 0.333). The only difference between the groups was in age. Those patients who received a macrolide were significantly younger than those who received only a nonpseudomonal third-generation cephalosporin (57.4+/-19.2 years vs 67.9+/-18.5 years; P < 0.001). However, when age and severity of illness were taken into account, no difference existed between the patients who received a nonpseudomonal third-generation cephalosporin alone or in combination with a macrolide.

CONCLUSIONS

We concluded that the addition of a macrolide to a nonpseudomonal third-generation cephalosporin as initial therapy for the treatment of CAP may not be necessary. A randomized, prospective clinical trial comparing a nonpseudomonal third-generation cephalosporin alone and in combination with a macrolide is warranted.

Activity of quinolones against Chlamydia pneumoniae

Quinolones are currently being used as empirical therapy for the treatment of community-acquired pneumonia and other respiratory infections as they cover a broad range of conventional bacterial and 'atypical' pathogens, including Chlamydia pneumoniae. C. pneumoniae has been associated with 10 to 20% of community-acquired pneumonia in adults and recently has been implicated as being associated with several nonrespiratory conditions, including atherosclerosis. However, data on the treatment of even respiratory infection due to C. pneumoniae are limited. Although currently available quinolones have good activity against C. pneumoniae in vitro, all published treatment studies have relied on serological diagnosis, thus microbiological efficacy has not been assessed. Anecdotal experience suggests that in vitro activity may not always correlate with efficacy in vivo.

The impact of blood cultures on antibiotic therapy in pneumococcal pneumonia

INTRODUCTION

The cost-effectiveness of blood cultures in community-acquired pneumonia (CAP) has been questioned. Although penicillin-resistant Streptococcus pneumoniae is an increasing problem, penicillin therapy, where appropriate, reduces cost and may reduce antibiotic resistance. Blood cultures, however, can only reduce cost if physicians are prepared to alter therapy based on the results. We reviewed our experience to determine how often physicians changed management based on blood culture results positive for S pneumoniae.

METHODS

Retrospective chart review was performed of all CAP admissions between January 1996 and December 1998 with blood culture results positive for S pneumoniae.

RESULTS

Seventy-four patients out of 1,805 patients admitted with CAP during this period had pneumococcemia. Penicillin resistance was identified in 15 cases (20.3%; high grade in 4 cases) with cephalosporin resistance in 4 of these cases (1 high grade). Fifty-one patients had initial empiric therapy with a third-generation cephalosporin, and 58 patients had empiric coverage of atypical organisms; no patient received empiric penicillin therapy. Blood culture results altered management in 31 patients (41.9%), but in only 2 cases was this due to antibiotic resistance. Fifty-one patients without penicillin allergy grew penicillin-sensitive pneumococci; only 11 patients (21.6%) were changed to penicillin therapy. Thirteen of 35 patients (37.1%) who were given an additional antibiotic for atypical coverage had this antibiotic ceased.

CONCLUSION

Despite evidence of penicillin-sensitive pneumococcal CAP, physicians were reluctant to narrow antibiotic therapy, potentially adding to treatment cost and reducing the impact of blood culture results on management. The impact of penicillin resistance was reduced by the usual empiric choice of a third-generation cephalosporin. While positive blood culture results can clearly be useful in the management of patients with CAP, their cost-effectiveness needs to be assessed in prospective clinical trials.

Atypical pathogens in community-acquired pneumonia

The atypical pathogens are an important and significant cause of CAP. The clinical and radiologic manifestations of CAP caused by these pathogens are modulated by the immunologic and physiologic status of the host, and therefore are not pathogen-specific. The range of frequencies found in various studies for the atypical pathogens among the causes of CAP is broad. These frequencies are affected by very important factors that should be recognized. In a significant percentage of patients, an atypical pathogen can be identified together with an additional cause. The significance of multiple causes has not been clarified sufficiently. The principal diagnostic techniques in use today for the causative diagnosis of CAP are serologic tests. Different serologic methods have been used in various studies and diagnostic criteria are not standardized. In the future it is likely that diagnostic testing will be based on the PCR technique on serum samples. The effectiveness and importance of antimicrobial therapy in some patients with atypical pathogen CAP are unclear. The accepted therapy today for atypical pathogen CAP, which is based on erythromycin, will probably be changed in the near future in favor of the new generations of fluoroquinolone or the new macrolide preparations.