Clinical outcomes of bacteremic pneumococcal pneumonia in the era of antibiotic resistance

Clinical implications and treatment of multiresistant Streptococcus pneumoniae pneumonia

Streptococcus pneumoniae is the leading bacterial cause of community-acquired respiratory tract infections. Prior to the 1970s this pathogen was uniformly susceptible to penicillin and most other antimicrobials. However, since the 1990s there has been a significant increase in drug-resistant Streptococcus pneumoniae (DRSP) due, in large part, to increased use of antimicrobials. The clinical significance of this resistance is not definitely established, but appears to be most relevant to specific MICs for specific antimicrobials. Certain beta-lactams (amoxicillin, cefotaxime, ceftriaxone), the respiratory fluoroquinolones, and telithromycin are among several agents that remain effective against DRSP. Continued surveillance studies, appropriate antimicrobial usage campaigns, stratification of patients based on known risk factors for resistance, and vaccination programmes are needed to appropriately manage DRSP and limit its spread.

Application of Pharmacokinetics and Pharmacodynamics to Antimicrobial Therapy of Community-Acquired Respiratory Tract Infections

To achieve bacteriologic and clinical success, sufficient concentrations of antimicrobial at the site of infection must be maintained for an adequate period of time. These dynamics are determined by combining drug pharmacokinetic and pharmacodynamic (PK/PD) data with minimum inhibitory concentrations. Bacteriologically confirmed failures have been reported in otitis media and, with a lesser degree of evidence, in pneumococcal pneumonia with a variety of agents that include beta-lactams, macrolides and fluoroquinolones. These failures have been shown to be due to infection by resistant pathogens or suboptimal therapy. However, no clinical failure has been reported during therapy for bacteremic pneumococcal pneumonia with adequate doses of beta-lactams. The failures reported with macrolides or fluoroquinolones have been due to either preexisting resistance to these agents that cannot be overcome by increasing the dose of the antimicrobial or, more rarely, the emergence of resistance during therapy. In this review, we offer an overview of the most important attributes of the main antimicrobials that are currently used in the treatment of community-acquired respiratory tract infections from a PK/PD perspective.

Epidemiology of community-acquired pneumonia in adult patients at the dawn of the 21st century: a prospective study on the Mediterranean coast of Spain

This study presents data from a prospective study of adult patients with community-acquired pneumonia (CAP). Of 493 patients included in the study, 223 (45.2%) were aged > or = 65 years, and 265 (53.7%) had one or more underlying diseases, mostly chronic obstructive pulmonary disease, diabetes mellitus or dementia. In total, 281 microorganisms were identified in 250 (50.7%) patients, with two or more pathogens detected in 28 (5.7%) cases. Microbial diagnosis varied according to age, severity, co-morbidity and site-of-care, but there was much overlap among groups. Streptococcus pneumoniae was the single most prevalent organism in outpatients, patients admitted to hospital, and patients who died, either as a single pathogen or combined with another organism. Infections caused by 'atypical' pathogens were seen across all groups, including the elderly and patients with co-morbidities. Mortality varied according to the pneumonia severity index (PSI) of the pneumonia patient outcomes research team. Shock (OR 34.48), an age of > 65 years (OR 25) and altered mental status (OR 9.92) were factors associated independently with 30-day mortality. Key findings from this study were the advanced age of the population with CAP, and the high prevalence of dementia as an underlying disease. The study also revealed that microbiological diagnosis of CAP remains problematic. Although certain epidemiological features may help to predict the microbial aetiology, the overlap among groups reduces the usefulness of this information in guiding therapeutic decisions. Greater effort should be made to improve identification methods for microbial pathogens causing CAP.

Streptococcus pneumoniae bacteremia in patients with cancer: disease characteristics and outcomes in the era of escalating drug resistance (1998-2002)

In the current era of multidrug-resistant organisms, the clinical spectrum of Streptococcus pneumoniae infection remains unclear, especially in immunosuppressed patients with cancer. We sought to define the characteristics of pneumococcal bacteremia in patients who were receiving care at a comprehensive cancer center. All consecutive episodes of S. pneumoniae bacteremia between January 1998 and December 2002 were evaluated retrospectively. One hundred thirty-five episodes of pneumococcal bacteremia occurred in 122 patients. Sixty-three (52%) of 122 patients had hematologic malignancies; the others had solid tumors. The median Acute Physiology and Chronic Health Evaluation II score was 14 +/- 5. Twenty-four episodes (18%) occurred during neutropenia (<500 cells/microL). Sixty-five patients (53%) were receiving antineoplastic therapy, and 36 (30%) were receiving systemic corticosteroids. Twelve (41%) of 29 hematopoietic stem cell transplant (HSCT) recipients had received transplantation within 12 months of the infection diagnosis; 11 patients had graft-versus-host disease (chronic in 10). In 27 episodes (22%), S. pneumoniae bacteremia was considered as a breakthrough infection. Nine (56%) of 16 hospital-acquired episodes of S. pneumoniae bloodstream infection occurred in patients with profound neutropenia, whereas 15 (13%) of 119 episodes of community-acquired infection occurred during neutropenia (p < 0.0002). In 91 episodes (67%), patients had radiographic evidence of pneumonia. Infected catheters were associated with 21 episodes (16%). Forty-eight (36%) of 135 isolates were not susceptible to penicillin (minimum inhibitory concentration [MIC] > or = 2 microg/mL); 9 (7%) showed intermediate susceptibility to ceftriaxone (MIC >0.5 and <2.0 microg/mL). Nineteen patients (16%) died within 2 weeks of diagnosis; 18 deaths were attributed to systemic pneumococcal infection. Univariate analysis showed no significant increase in the risk of short-term death in patients with infection due to penicillin non-susceptible organisms (OR [odds ratio], 1.47; 95% confidence intervals [CI], 0.53-4.05; p < 0.46), initially discordant treatment (OR, 1.0; 95% CI, 0.62-665.4; p < 0.16), presence of pneumonia (OR, 1.19; 95% CI, 0.39-3.62; p < 0.76), neutropenia (OR, 1.0; 95% CI, 0.28-4.09; p < 0.92), systemic corticosteroid use (OR, 1.96; 95% CI, 0.69-5.60; p < 0.21), or antineoplastic therapy (OR, 1.45; 95% CI, 1.52-4.05; p < 0.47). Similarly, patients with hematologic cancers compared to those with solid cancers (OR, 1.0; 95% CI, 0.49-3.70; p < 0.56) and recipients of HSCT compared to those with no history of transplantation (OR, 1.0; 95% CI 0.59-12.71; p < 0.20) did not have a less favorable outcome. In conclusion, most pneumococcal bloodstream infections were community acquired, although hospital-acquired infections were common in neutropenic patients. It is noteworthy that initially discordant therapy, penicillin non-susceptible S. pneumoniae, and other conventional predictors of unfavorable outcome were not associated with increased mortality rates in these high-risk patients with cancer.

The Controversy of Combination vs Monotherapy in the Treatment of Hospitalized Community-Acquired Pneumonia

BACKGROUND

The majority of community-acquired pneumonia (CAP) patients (about 80%) will be treated as outpatients, because therapy with a single agent will work. For the remaining 20% of patients requiring hospitalization, there is some growing debate regarding the efficacy of different management approaches. For hospitalized patients, monotherapy with a respiratory fluoroquinolone agent seems to be gaining popularity, but dual therapy combining a beta-lactam and an advanced macrolide still represents a good choice. Indeed, this regimen was recommended for all of the inpatient categories in the latest Infectious Disease Society of America CAP guidelines in 2003.

AIM

The purpose of this review was to examine the current clinical evidence to support one option or the other by gathering all of the available published literature. We will review the existing controversies in terms of microbiology, immunology, and clinical outcomes comparing dual therapy (ie, with any combination of beta-lactams, macrolides, or fluoroquinolones) with monotherapy in the treatment of CAP.

RESULTS

For the vast majority of patients with CAP (ie, outpatients and inpatients on medical wards), the type of antibiotic regimen prescribed does not have any significant impact. For patients with severe pneumonia, for which there is no accepted definition so far, the controversy remains alive. Mortality from pneumococcal pneumonia has been reduced over the last decades, but despite improved medical care, bacteremic pneumococcal pneumonia is still as lethal as ever, probably because of the aging population, the greater number of immunocompromised patients, and the number of patients with frequent comorbid conditions. Worldwide, the increasing rates of resistance of Streptococcus pneumoniae to antibiotics are also a serious concern, and the clinical implications are not always obvious. Although limited in number, the four studies showing the importance of adding a macrolide to a beta-lactam regimen for the treatment of bacteremic S pneumoniae pneumonia are retrospective and nonblinded, the findings are consistent, and they point to a trend that has to be explored more thoroughly. Studies published in the last few years suggest that combination therapy may be superior for bacteremic S pneumoniae pneumonia.

CONCLUSION

In the meantime, for practical purposes, patients hospitalized with a diagnosis of severe CAP may benefit from a dual antibiotic therapy combining a third-generation cephalosporin and a macrolide. For the majority of hospitalized patients with CAP who are not severely ill, fluoroquinolone monotherapy remains an approved, tested, and reliable option. Indeed, the time for more aggressive outpatient fluoroquinolone therapy may reduce the number of patients who are hospitalized with CAP. Independent prospective studies comparing combination therapy with standard monotherapy are urgently required for hospitalized patients with severe CAP.

Community-acquired bacteraemic pneumococcal pneumonia in adults: effect of diminished penicillin susceptibility on clinical outcome

Pneumococcal pneumonia remains a common disease with a high mortality rate. Between 1995 and 2000, we prospectively analyzed 95 consecutive adult cases of community-acquired bacteraemic pneumococcal pneumonia treated in a single centre. The incidence of pneumococcal resistance to penicillin increased from 19 to 50% during the study period. Multivariate analysis showed that only age and recent hospitalization were independently associated with fatal outcome. The proportion of penicillin-resistant strains was slightly but not significantly higher among patients who died before the fourth hospital day than among those who died later. Patients who died before D4 were more likely to have a recent history of hospitalization, cancer and/or chemotherapy. It thus appears that infection by a resistant pneumococcal strain is not in itself a gravity factor in this setting, but that their acquisition is associated with pejorative clinical features.

Antimicrobial treatment of community-acquired pneumonia

Community-acquired pneumonia (CAP) is a clinical diagnosis that has a significant impact on health care management around the world. Early clinical suspicion and prompt empiric antimicrobial therapies are mandatory in patients with CAP. This article provides a review of recent studies and guidelines addressing antimicrobial therapy for hospitalized patients with CAP.

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.

[Guidelines for the management of community pneumonia in adult who needs hospitalization]

Community acquired pneumonia is still an important health problem. In Spain the year incidence is 162 cases per 100,000 inhabitants with 53,000 hospital admission costing 115 millions of euros per year. In the last years there have been significant advances in the knowledge of: aetiology, diagnostic tools, treatment alternatives and antibiotic resistance. The Spanish Societies of Intensive and Critical Care (SEMICYUC), Infectious Diseases and Clinical Microbiology (SEIMC) and Pulmonology and Thoracic Surgery (SEPAR) have produced these evidence-based Guidelines for the management of community acquired pneumonia in Adults. The main objective is to help physicians to make decisions about this disease. The different points that have been developed are: aetiology, diagnosis, treatment and prevention.

Nonresponses and treatment failures with conventional empiric regimens in patients with community-acquired pneumonia

Although most patients with suspected CAP respond to empiric therapy,a small number of patients do not respond in the expected fashion. Age and underlying comorbid conditions have a strong influence on the course of illness. Less common causes of treatment failures include overwhelming infection, antimicrobial resistance, and misdiagnosis. It is a common practice for empiric antimicrobial treatment of CAP to be initiated without microbiologic studies. Clinicians carefully should observe these patients for unusual or slow responses and should be ready to pursue a more extensive search for the cause of treatment failure.

Antibacterial drug resistance: implications for the treatment of patients with community-acquired pneumonia

In contrast to the tremendous number of articles and meetings devoted to elucidating the mechanisms of antibacterial drug resistance and describing the emergence of drug resistance patterns, little research has been completed on the impact of bacterial drug resistance on clinical outcomes. Moreover.among the studies that have been completed, the better-designed studies generally have failed to detect an effect of most current levels of antibacterial drug resistance on clinical outcomes for patients who have CAP. Yet, practice patterns are shifting in response to the perception that current levels of drug resistance necessitate changes in treatment patterns. This is unfortunate because it severely limits one's ability to continue to monitor the effectiveness of available therapies in light of changing patterns of antibacterial drug resistance. If levels of drug resistance continue to rise, it is likely that outcomes from those drug treatments will be affected adversely. In this regard, the recent licensing of a 7-valent pneumococcal conjugate vaccine for infants and young children may have an important effect on future trends in antibacterial drug resistance. The vaccine reduces childhood carriage of vaccine serotypes,which are among the most common serotypes found among drug-resistant isolates, and may reduce transmission of these serotypes to adults [65]. In conclusion, antibacterial drug resistance has not reduced substantially the effectiveness of first-line treatments for CAP. Whether levels of drug resistance will continue to increase or decline is unknown. Therefore,carefully designed outcomes studies likely will continue to be essential to help define optimal therapy for patients who have CAP.

Community-acquired pneumonia: new management strategies for evolving pathogens and antimicrobial susceptibilities

Community-acquired pneumonia (CAP) is still one of the leading causes of mortality and morbidity. The most common bacterial cause of CAP is Streptococcus pneumoniae. The increase in antimicrobial resistance has raised concerns about the efficacy of available therapies, and a call for the reassessment of both existing and newer therapeutic agents. Although microbiological breakpoints are useful for monitoring the emergence of resistance, the current National Committee for Clinical Laboratory Standards (NCCLS) guidelines make no distinction between clinical and microbiological breakpoints. Recent changes in NCCLS breakpoints for extended spectrum cephalosporins have provided a more meaningful approach to susceptibility testing and to consideration of the site of infection. Further controversy surrounds the clinical guidelines relating to CAP in terms of which antimicrobial agents should be given empirically to which types of patients. Within this review, the role of monotherapy versus the need for combination antimicrobial therapy, which often includes a macrolide and an extended spectrum cephalosporin such as ceftriaxone, is discussed. This review also discusses the various aspects of antimicrobial susceptibilities of S. pneumoniae, the drivers and influences of increasing resistance, the clinical relevance of this resistance and possible therapeutic options in the face of changing susceptibilities and mixed bacterial aetiologies. New guidelines from the IDSA attempt to embrace these changes.

Factores relacionados con la mortalidad de la enfermedad neumocócica invasiva

BACKGROUND AND OBJECTIVE

To analyze the risk factors associated with mortality in invasive pneumococcal disease in the university hospital Fundación Jiménez Díaz (Madrid, Spain) during 11 years.

PATIENTS AND METHOD

We performed a retrospective study of patients attending the emergency service of the hospital from January 1993 to August 2003. We registered data on mortality, clinical and microbiological evolution and relapses.

RESULTS

We studied 263 patients with pneumococcal baceteremia and invasive disease caused by Streptococcus pneumoniae (pneumonia, meningitis, sepsis, bacteremia of unknown origin and oligoarthritis). Mortality was 12.5%. Variables associated with mortality in a logistic regression analysis included absence of leukocytosis (p = 0.04), acidosis (p < 0.01), respiratory signs and symptoms (tachypnea, pleuritic pain) (p = 0.02), and neurologic manifestations (decreased consciousness level; (p < 0.01).

CONCLUSION

Patients at highest risk of death because of invasive pneumococcal disease are critically ill, with no leukocytosis, with severe respiratory or neurological symptoms and undergoing invasive procedures such as mechanical ventilation and tracheostomy.

Reference group choice and antibiotic resistance outcomes

Two types of cohort studies examining patients infected with methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE) were contrasted, using different reference groups. Cases were compared to uninfected patients and patients infected with the corresponding, susceptible organism. VRE and MRSA were associated with adverse outcomes. The effect was greater when uninfected control patients were used.

Streptococcus pneumoniae and community-acquired pneumonia: a cause for concern

Community-acquired pneumonia (CAP) is the sixth most common cause of death in the United States and the leading cause of death from infectious diseases. It is associated with significant morbidity and mortality, and poses a major economic burden to the healthcare system. Streptococcus pneumoniae is the leading cause of CAP. Other common bacterial causes include Haemophilus influenzae as well as atypical bacteria (Mycoplasma pneumoniae, Chlamydia pneumoniae, and Legionella species). Increasing resistance to a variety of antimicrobial agents has been documented in S. pneumoniae and is common in H. influenzae as well. Successful empiric therapy is paramount to the management of CAP to avoid treatment failure and subsequent associated costs. Given that resistance is increasing among respiratory pathogens, and S. pneumoniae is the most common etiologic agent identified in CAP, strategies for antimicrobial therapy should be based on the likely causative pathogen, the presence of risk factors for infection with resistant bacteria, and local resistance patterns.

Serotype-specific mortality from invasive Streptococcus pneumoniae disease revisited

Background

Invasive infection with Streptococcus pneumoniae (pneumococci) causes significant morbidity and mortality. Case series and experimental data have shown that the capsular serotype is involved in the pathogenesis and a determinant of disease outcome.

Methods

Retrospective review of 464 cases of invasive disease among adults diagnosed between 1990 and 2001. Multivariate Cox proportional hazard analysis.

Results

After adjustment for other markers of disease severity, we found that infection with serotype 3 was associated with an increased relative risk (RR) of death of 2.54 (95% confidence interval (CI): 1.22–5.27), whereas infection with serotype 1 was associated with a decreased risk of death (RR 0.23 (95% CI, 0.06–0.97)). Additionally, older age, relative leucopenia and relative hypothermia were independent predictors of mortality.

Conclusion

Our study shows that capsular serotypes independently influenced the outcome from invasive pneumococcal disease. The limitations of the current polysaccharide pneumococcal vaccine warrant the development of alternative vaccines. We suggest that the virulence of pneumococcal serotypes should be considered in the design of novel vaccines.

Penicillin and macrolide resistance in pneumococcal pneumonia: does in vitro resistance affect clinical outcomes?

In vitro resistance to antimicrobial agents is escalating among pathogens responsible for the most serious respiratory tract infections. Some reports have suggested that this has direct clinical implications. Because of penicillin and macrolide resistance in Streptococcus pneumoniae, current guidelines for the initial treatment of respiratory tract infections advocate less reliance on the use of either of these classes of drugs in single-agent therapy. Recent studies that have assessed the impact of beta -lactam and macrolide resistance on clinical outcomes in community-acquired pneumonia fail to provide incontrovertible evidence for a direct link between in vitro resistance and treatment failure. However, there are anecdotal reports of breakthrough bacteremia due to macrolide-resistant pneumococci among patients receiving macrolide therapy, unlike the situation for beta -lactams and penicillin-resistant pneumococci. Continued efforts, including in vitro surveillance, appropriate antibiotic use campaigns, and immunization programs, will be important in limiting the spread of drug-resistant S. pneumoniae.

Clinical relevance of antimicrobial resistance in the management of pneumococcal community-acquired pneumonia

Streptococcus pneumoniae remains the most common bacterial cause of community-acquired pneumonia, and these infections are associated with significant morbidity and mortality worldwide. A major concern is the increasing incidence of antibiotic resistance among pneumococcal isolates, which, in the case of certain of the antibiotic classes, has been associated with treatment failure. Yet despite multiple reports of infections with penicillin-resistant pneumococcal isolates, no cases of bacteriologic failure have been documented with the use of penicillin or ampicillin in the treatment of pneumonia caused by penicillin-resistant pneumococci. Current prevalence and levels of penicillin resistance among pneumococal isolates in most areas of the world do not indicate a need for substantial treatment changes with regard to the use of the penicillins. For infections with penicillin-sensitive strains, penicillin or an aminopenicillin in a standard dosage will still be effective for treatment. In the cases of strains with intermediate resistance, beta-lactam agents are still considered appropriate treatment, although higher dosages are recommended. Infections with isolates of high-level penicillin resistance should be treated with alternative agents such as the third-generation cephalosporins or the new antipneumococcal fluoroquinolones. In the case of the cephalosporins, pharmacodynamic/pharmacokinetic parameters help predict which of those agents are likely to be successful, and the less active agents should not be used. Debate continues in the literature with regard to the impact of macrolide resistance on the outcome of pneumococcal pneumonia, with some investigators providing evidence of an "in vivo-in vitro paradox," referring to discordance between reported in vitro resistance and clinical success of macrolides/azalide in vivo. However, several cases of macrolide/azalide treatment failure have been documented, and many clinicians recommend that these agents not be used on their own in areas with a high prevalence and levels of macrolide/azalide resistance. However, evidence is emerging to show beneficial effects on outcome with combination therapy, especially that of a beta-lactam agent and a macrolide given together to sicker, hospitalized patients with pneumococcal pneumonia. In an attempt to prevent the emergence of resistance, it has been recommended by some that the new fluoroquinolones not be used routinely as first-line agents in the treatment of community-acquired pneumonia; instead, they say, these agents should be reserved for patients who are allergic to the commonly used beta-lactam agents, for infections known to be or suspected of being caused by highly resistant strains, and for patients in whom initial therapy has failed.

Changes in the epidemiology of pneumococcal bacteremia in a Swiss university hospital during a 15-year period, 1986-2000

OBJECTIVE

To evaluate changes in epidemiological characteristics and outcome of patients with pneumococcal bacteremia during a 15-year period in a Swiss university hospital.

PATIENTS AND METHODS

We reviewed the medical records of all hospitalized adults at the University Hospital Basel, Basel, Switzerland, whose blood culture yielded Streptococcus pneumoniae from January 1, 1986, through December 31, 2000.

RESULTS

We analyzed 405 episodes of pneumococcal bacteremia in 394 patients. The mean annual incidence of 1.78 episodes per 1000 hospital admissions was inversely related to the mean atmospheric temperature of the area. During the study period, penicillin nonsusceptibility increased from 0% to 17%. The overall case-fatality rate was 25%, which decreased from 33% to 17% between the first and the second half of the study period (P<.001). The proportion of women with pneumococcal bacteremia increased from 37% to 52%. Independent risk factors for fatal outcome were coronary artery disease (P<.001; relative risk [RR], 4.3; 95% confidence interval [CI], 3.4-5.1), neutropenia (P=.001; RR, 3.2; 95% CI, 1.9-4.8), and age 65 years or older (P=.001; RR, 2.9; 95% CI, 1.8-4.2), whereas prior respiratory tract infection (P=.03; RR, 0.3; 95% CI, 0.1-0.5) and the occurrence of pneumococcal bacteremia in the second half of the study period (P=.01; RR, 0.4; 95% CI, 0.2-0.6) were independent predictors of survival. The case-fatality rate in human immunodeficiency virus (HIV)-infected patients was significantly lower than in patients not infected with HIV or in those with unknown HIV status (9% vs 27%; P=.006), which correlated with the younger mean +/- SD age of HIV-infected patients (33.2+/-6.6 years) compared with patients not infected with HIV (63.1+/-18.1 years) (P<.001).

CONCLUSIONS

The case-fatality rate of patients with pneumococcal bacteremia decreased significantly between the first and second half of the study period, despite the increased prevalence of penicillin-nonsusceptible isolates. Independent risk factors for fatal outcome were coronary artery disease, neutropenia, and age 65 years or older, whereas prior respiratory tract infection and the occurrence of pneumococcal bacteremia in the second half of the study period were independent predictors of survival. HIV infection was a predisposing factor for pneumococcal bacteremia but was not a risk factor for fatal outcome.

Clinical response to antibiotic therapy for community-acquired pneumonia

Childhood community-acquired pneumonia is a common and potentially serious problem worldwide. Unless the patient has bacteraemia or pleural empyema, aetiological diagnostics are limited and antibiotic treatment is empirical. Published data on expected response to therapy are scarce. To determine the clinical response to antibiotic treatment in a developed country in otherwise healthy children with community-acquired pneumonia, we conducted a prospective study of 153 hospitalised children with pneumonia. The role of 17 microbes as potential causative agents was evaluated. The duration of fever (>37.5 degrees C) and hospitalisation were studied as objective measures of recovery. A potential aetiology was found in 83% of 153 patients: 29% of the patients had sole viral and 26% sole bacterial and 29% mixed viral-bacterial infections. The median duration of fever after the onset of antibiotic treatment (mainly penicillin G) was 14 h and the median duration of hospitalisation was 48 h. Patients with mixed viral-bacterial infection became afebrile more slowly than those with either sole viral or sole bacterial infections.

CONCLUSION

the findings indicate that in a developed country, children with pneumonia make a rapid, uneventful recovery needing only a short hospital stay. Expensive and time-consuming microbiological investigations are not required once bacterial sepsis has been excluded.

Prospective observational study of bacteremic pneumococcal pneumonia: Effect of discordant therapy on mortality*

STUDY OBJECTIVE

To evaluate the effect of discordant empirical therapy on outcome in bacteremic pneumococcal community-acquired pneumonia.

DESIGN

Prospective observational study.

SETTING

A 600-bed teaching hospital with a reference area of 400,000 inhabitants.

PATIENTS

All patients aged > or =18 yrs with a diagnosis of community-acquired pneumonia whose blood cultures, obtained within the first 48 hrs of hospitalization, demonstrated growth of Streptococcus pneumoniae were included in the study.

METHODS

Discordant therapy was defined as failure to administer an antibiotic with in vitro activity against the isolated strain within 24 hrs of hospital admission. The 2002 breakpoints recommended for respiratory infections by the National Committee for Clinical Laboratory Standards were used to classify therapy.

RESULTS

A total of 100 patients with bacteremic pneumococcal pneumonia were identified. Penicillin- and macrolide-resistant strains were identified in 29 and 18 cases, respectively. Only two strains had minimum inhibitory concentrations of >2 microg/mL for cephalosporins. Discordant therapy was documented in ten patients, five of whom died. Mortality in patients receiving concordant therapy was 14% (13 of 90). Nursing home residence (odds ratio [OR] = 14.8) and immunocompromise (OR = 11.5) were independently (p <.05) associated with discordant therapy. Risk of discordant therapy was significantly higher (p <.05) when empirical therapy did not include cefotaxime or ceftriaxone (OR = 10.4). Discordant therapy (OR = 27.3), multilobar involvement (OR = 14.2), underlying chronic obstructive pulmonary disease (OR = 9.1), and hospitalization during the previous 12 wks (OR = 7.9) were independently associated (p <.05) with death. The excess mortality for initial discordant therapy was estimated to be 35.6% (95% confidence interval, 3.73-67.4).

CONCLUSIONS

Survival in patients with bacteremic community-acquired pneumococcal pneumonia can be improved by avoiding suboptimal therapy. Using the 2002 breakpoints, it is very unlikely that discordant therapy would be given with ceftriaxone or cefotaxime. Clinical outcome is worse in those patients receiving antimicrobial therapy that in vitro testing suggests would be ineffective.

Community-acquired pneumonia

This seminar reviews important features and management issues of community-acquired pneumonia (CAP) that are especially relevant to immunocompetent adults in light of new information about cause, clinical course, diagnostic testing, treatment, and prevention. Streptococcus pneumoniae remains the most important pathogen; however, emerging resistance of this organism to antimicrobial agents has affected empirical treatment of CAP. Atypical pathogens have been quite commonly identified in several prospective studies. The clinical significance of these pathogens (with the exception of Legionella spp) is not clear, partly because of the lack of rapid, standardised tests. Diagnostic evaluation of CAP is important for appropriate assessment of severity of illness and for establishment of the causative agent in the disease. Until better rapid diagnostic methods are developed, most patients will be treated empirically. Antimicrobials continue to be the mainstay of treatment, and decisions about specific agents are guided by several considerations that include spectrum of activity, and pharmacokinetic and pharmacodynamic principles. Several factors have been shown to be associated with a beneficial clinical outcome in patients with CAP. These factors include administration of antimicrobials in a timely manner, choice of antibiotic therapy, and the use of a critical pneumonia pathway. The appropriate use of vaccines against pneumococcal disease and influenza should be encouraged. Several guidelines for management of CAP have recently been published, the recommendations of which are reviewed.

The epidemiology of antibiotic resistance in Streptococcus pneumoniae and the clinical relevance of resistance to cephalosporins, macrolides and quinolones

Invasive non-meningeal pneumococcal infections remain a major cause of morbidity and mortality worldwide. The factors affecting the epidemiology and mortality of pneumococcal infections are discussed. The increase and spread of resistance to antimicrobial agents among pneumococci is a cause of concern to the clinician. There are links between the usage of antibacterial agents and the development of resistance. Resistance to penicillin and other beta-lactams has become widespread but this does not appear to have decreased the efficacy of some of these agents against non-meningeal infections. There is evidence that the good pharmacokinetic and pharmacodynamic features of the third generation cephalosporins (cefotaxime and ceftriaxone) contribute to their efficacy in vivo. New breakpoints for cefotaxime and ceftriaxone against non-meningeal pneumococcal isolates were proposed by the National Committee for Clinical Laboratory Standard (NCCLS, US), based on the clinical evidence of the efficacy of these drugs. In contrast there is increasing evidence that resistance to macrolides can lead to a poor clinical response. Fluoroquinolones have been widely used to treat respiratory tract infections among others, and pneumococcal resistance to these agents in vitro, although currently low, is increasing. There are reports that resistance to fluoroquinolones can develop during treatment and may be reflected in a lack of clinical response. Several clinical and epidemiological variables (e.g. prior antibiotic use) can be useful to identify patients at risk from infections with antibiotic-resistant pneumococci. These patients would be those who would benefit the most from a pneumococcal vaccination programme.

An international prospective study of pneumococcal bacteremia: correlation with in vitro resistance, antibiotics administered, and clinical outcome

We performed a prospective, international, observational study of 844 hospitalized patients with blood cultures positive for Streptococcus pneumoniae. Fifteen percent of isolates had in vitro intermediate susceptibility to penicillin (minimum inhibitory concentration [MIC], 0.12-1 microg/mL), and 9.6% of isolates were resistant (MIC, >or=2 microg/mL). Age, severity of illness, and underlying disease with immunosuppression were significantly associated with mortality; penicillin resistance was not a risk factor for mortality. The impact of concordant antibiotic therapy (i.e., receipt of a single antibiotic with in vitro activity against S. pneumoniae) versus discordant therapy (inactive in vitro) on mortality was assessed at 14 days. Discordant therapy with penicillins, cefotaxime, and ceftriaxone (but not cefuroxime) did not result in a higher mortality rate. Similarly, time required for defervescence and frequency of suppurative complications were not associated with concordance of beta-lactam antibiotic therapy. beta-Lactam antibiotics should still be useful for treatment of pneumococcal infections that do not involve cerebrospinal fluid, regardless of in vitro susceptibility, as determined by current NCCLS breakpoints.

Why do we need to eradicate pathogens in respiratory tract infections?

Evidence from studies in otitis media, acute bacterial sinusitis and acute exacerbations of chronic bronchitis indicate that clinical efficacy is dependent on bacterial eradication. Failure to eradicate bacterial pathogens increases the potential for clinical failure, incurring further costs, and may also select and maintain bacteria that are resistant to a wide range of antimicrobials. Bacteriologically confirmed clinical failures have been reported in pneumococcal pneumonia with both macrolides and older fluoroquinolones (ciprofloxacin, ofloxacin, and levofloxacin). These failures were due to the involvement of resistant pathogens (macrolides) or suboptimal pharmacokinetics/pharmacodynamics (PK/PD) (quinolones). However, persistent positive blood cultures have not been reported during therapy with adequate doses of benzylpenicillins or aminopenicillins. Treatment failure, driven by the failure to eradicate pathogens, leads to both economic and environmental costs, hospitalization being the major cost driver. Failure to achieve bacterial eradication may also lead to the development and spread of resistance. Different types of antimicrobials appear to be driving resistance to different extents, and this may be due to suboptimal PK/PD. In conclusion, factors to consider when prescribing include an accurate diagnosis, knowledge of local epidemiology, the role of PK/PD principles in antimicrobial choice, clinical outcomes in relation to bacteriologic efficacy, and resistance and its bacteriologic and clinical impact. The vicious cycle of infection, inappropriate therapy, bacteriologic failure, selection/spread of resistance and further infection needs to be broken by the use of appropriate treatments to achieve bacterial eradication.

Severe community-acquired pneumonia

Although several pneumonia severity criteria have been firmly established, the exact definition of severe community-acquired pneumonia (CAP) remains elusive. Mortality from CAP remains high, reaching 50% in some series. The particular role of and spp. in severe CAP has been defined more clearly. Microbial diagnosis in the individual patient remains a difficult task. Despite promising new diagnostic tools, concerns about possible mixed origins preclude a change from the currently advocated broad-spectrum approach of antimicrobial treatment. Although there is some evidence that guidelines may optimize outcomes, their role in limiting the spread of resistance has only recently received attention. Finally, although there are promising data on the use of noninvasive positive pressure ventilation to treat pneumonia in patients without chronic obstructive pulmonary disease, its place in the management of acute respiratory failure remains to be defined in randomized studies.

Antibiotic resistance in the intensive care unit

The increase in antibiotic resistance over the past 10 years can be traced to several factors. This includes exogenous transmission of bacteria, usually by hospital personnel. The use of potent antibiotics also can select for resistant bacteria initially present in low quantities. Strategies to reduce antibiotic resistance can be tailored to specific outbreaks in a given ICU. General strategies for reducing antibiotic resistance, on the other hand, include varying the agents used in the ICU over time. Reduction of the duration of therapy may prove to be another method of reducing antibiotic resistance.

The effect of cephalosporin resistance on mortality in adult patients with nonmeningeal systemic pneumococcal infections

PURPOSE

To evaluate the clinical relevance of cephalosporin (ceftriaxone/cefotaxime) resistance among patients with nonmeningeal systemic pneumococcal infection.

SUBJECTS AND METHODS

From January 1994 to October 2000, we prospectively studied 522 episodes of nonmeningeal systemic pneumococcal infections (448 pneumonias) in 499 adults who were treated according to hospital guidelines. In vitro antibiotic susceptibility, as the minimum inhibitory concentration (MIC), was determined by microdilution method. The MIC methods and breakpoints (cutoffs) were established by the National Committee for Clinical Laboratory Standards.

RESULTS

Of the 522 pneumococcal strains, 413 strains (79%) were susceptible to ceftriaxone/cefotaxime, MIC < or =0.5 microg/mL; 79 (15%) were intermediate, MIC = 1 microg/mL; and 30 (6%) were resistant, MIC = 2 microg/mL. After adjusting for several variables, including pneumococcal serogroups/serotypes, infections due to nonsusceptible (intermediate and resistant) pneumococcal strains were independently associated with prior antibiotic therapy, with an odds ratio of 5.9 (95% confidence interval: 2.6 to 13.6). Thirty-day mortality among the 185 patients who were treated with ceftriaxone (1 g/d) or cefotaxime (1.5 g every 8 hours) did not differ by cephalosporin susceptibility: 18% (26/148) among those with susceptible organisms, 13% (3/24) with intermediate organisms, and 15% (2/13) in resistant cases (P = 0.81).

CONCLUSION

Ceftriaxone or cefotaxime were effective in treating patients with nonmeningeal systemic pneumococcal infections caused by strains with MIC < or =2 microg/mL. These results support the newly established ceftriaxone/cefotaxime MIC breakpoints (cutoffs) for nonmeningeal pneumococcal infections.

Treatment of drug-resistant pneumococcal pneumonia

The increasing prevalence of resistance to penicillin and other drugs among pneumococci has considerably complicated the empirical treatment of community-acquired pneumonia. Penicillin resistance has become widespread and is a worldwide occurrence. Resistance to other classes of antibiotics traditionally used as alternatives in the treatment of pneumococcal infections has also increased markedly during recent years. In some areas of the USA, Europe, and east Asia a prevalence of macrolide resistance as high as 35% or more has been reported recently. From the clinical standpoint, a growing number of failures following the use of these agents has been described. Resistance to fluoroquinolones remains low but several failures have been reported in different parts of the world. Pharmacokinetic/pharmacodynamic parameters have become essential at the time of making a rational choice and calculation of dosage. Penicillin G remains the mainstay of therapy for the treatment of penicillin-susceptible pneumococcal pneumonia. Penicillin-resistant pneumococcal pneumonia (minimum inhibitory concentration <4 microg/mL) can be safely treated with adequate betalactams at the right dosage. The new fluoroquinolones are very active and effective in pneumococcal pneumonia. Caution should be exercised in the widespread prescription of these drugs if we are to limit the rate of resistance to these agents.

Management of community-acquired pediatric pneumonia in an era of increasing antibiotic resistance and conjugate vaccines

The antibiotic management of infants and children with pneumonia is based on the clinician's assessment of the most likely infecting pathogens, the susceptibilities of the infecting pathogens and the seriousness of the illness. The bacterial etiology of pneumonia changed significantly following the universal use of protein-conjugated vaccines for Haemophilus influenzae type b. Similar significant changes are likely to occur with universal use of protein-conjugated vaccines for Streptococcus pneumoniae, requiring the clinician to alter assumptions of the risk of invasive bacterial infection in the child who presents with pneumonia. New strategies are likely to require fewer ancillary tests (e.g. white blood cell count, C-reactive protein and blood culture) and suggest a decreased need for empiric antibiotic therapy. Although the majority of lower respiratory tract infections in children have a viral etiology and are not amenable to antibiotic therapy, for the seriously ill child who is thought to be likely to have pneumonia caused by a bacterial pathogen, recent changes in the susceptibility patterns of both common organisms such as S. pneumoniae and more unusual pulmonary pathogens such as Staphylococcus aureus have forced changes in the selection of both empiric and definitive antibiotic therapy. Third generation cephalosporins ceftriaxone and cefotaxime appear to be effective therapy for pneumonia caused by virtually all current isolates of S. pneumoniae. In contrast antibiotic regimens for life-threatening pulmonary infections in which Staphylococcus aureus is a suspected pathogen should include vancomycin.

Efficacy and tolerability of gatifloxacin in community treatment of acute exacerbations of chronic bronchitis

BACKGROUND

Recognizing acute exacerbations of chronic bronchitis (AECB) and selecting appropriate antibiotic treatment for patients who would benefit most is a challenge for community-based physicians.

OBJECTIVE

The Tequin Clinical Experience Study, an open-label, noncomparative, postmarketing trial, assessed the efficacy and tolerability of gatifloxacin, an 8-methoxy fluoroquinolone, in the treatment of AECB in the community-practice setting.

METHODS

Consecutive patients with respiratory tract infections in community-based settings were eligible for participation. Treated patients (N = 2512) included 1107 men (44.1%) and 1405 women (55.9%) aged > or =18 years with a clinical diagnosis of chronic bronchitis. All participants received oral gatifloxacin 400 mg once daily for 7 to 10 days. Clinical response was determined via telephone contact conducted by the investigator or study coordinator using case-report forms or during an office visit after the last dose. The investigator or coordinator collected expectorated or induced sputum specimens that were then smeared on a microscope slide, stored in a tube, and transported to a central reference laboratory for Gram-staining and culture. Of 1388 pretreatment sputum specimens submitted, pathogens were isolated from 424.

RESULTS

The most frequently detected pathogens were Haemophilus influenzae, Moraxella catarrhalis, and Streptococcus pneumoniae. All H. influenzae and 99% of S. pneumoniae isolates tested were susceptible to gatifloxacin. Of the 2267 patients with a determinable clinical response, 2084 (91.9% [95% CI, 90.8%-93.0%]) were cured (all acute symptoms improved or returned to baseline level, no new symptoms present, no additional antibiotic required). The 95.8% cure rate in 166 patients with H. influenzae included 100% of those with beta-lactamase-positive strains. Overall, 89.2% of 111 patients with M. catarrhalis were cured; rates were similar regardless of beta-lactamase production. The clinical cure rate in 74 patients with S. pneumoniae was 98.6% and was independent of the degree of penicillin resistance (minimum inhibitory concentration > or =2.0 microg/ mL). All 6 patients infected with S. pneumoniae fully resistant to penicillin were cured. Gatifloxacin was generally well tolerated, and the majority of adverse events were mild to moderate; only 11 drug-related adverse events in 10 patients (0.4%) were serious. Drug-related nausea (3.0%), dizziness (1.5%), diarrhea (1.2%), and vomiting (0.9%) were the most common adverse events.

CONCLUSIONS

The high clinical cure rate and favorable tolerability support gatifloxacin as a rational choice for the treatment of AECB in patients such as those in this community-based study.

Update on community-acquired pneumonia: impact of antibiotic resistance on clinical outcomes

In contrast to the rapid expansion in the number of published studies reporting the increasing rate of antimicrobial drug resistance among common respiratory pathogens, there remain few controlled studies examining the impact of these trends on clinical outcomes. Those studies that are published are hampered by small sample sizes, biases inherent in observational designs, and the relative infrequency of isolates showing high-level resistance, particularly high-level beta-lactam resistance among clinical isolates of Streptococcus pneumoniae. This update summarizes recent published studies addressing the impact of drug resistance on outcomes for lower respiratory tract infections. The majority of these studies are retrospective cohort studies, focusing on the impact of beta-lactam-resistant pneumococcal infections in patients with community-acquired pneumonia. These studies support the conclusion that current levels of pneumococcal drug resistance do not result in clinical treatment failures for patients with community-acquired pneumonia. However, as patterns of drug resistance evolve, future studies will be needed to address the continued appropriateness of current empirical treatment guidelines for these patients.

Penicillin-resistant pneumococci-implications for management of community-acquired pneumonia and meningitis

Penicillin-nonsusceptible Streptococcus pneumoniae isolates have become increasingly prevalent worldwide. They are well-known agents of community-acquired infections such as otitis media, pneumonia and bacterial meningitis. Therapy of pneumococcal infections is made difficult by the emergence and spread of bacterial resistance to penicillin and other beta-lactams, as well as other antimicrobials such as macrolides. This article reviews current concepts of epidemiology and the implications of penicillin-nonsusceptible pneumococci for management of community-acquired pneumonia and meningitis.

Severe community-acquired pneumonia: current outcomes, epidemiology, etiology, and therapy

Severe community-acquired pneumonia is a clinical diagnosis with a significant impact on healthcare management around the world, with the highest morbidity and mortality of all of the forms of community-acquired pneumonia. Patients with severe pneumonia usually require intensive care unit management, including vasopressors or mechanical ventilation. Early clinical suspicion and prompt empiric antimicrobial therapies are mandatory in patients with severe pneumonia. A number of recent studies and guidelines addressing these issues have been published, and they will be reviewed in this article.