Influence of penicillin resistance on outcome in adult patients with invasive pneumococcal pneumonia: is penicillin useful against intermediately resistant strains?

Efficacy and safety of oral gemifloxacin for the empirical treatment of pneumonia

CONTEXT

Respiratory tract infections (RTI) are common causes of morbidity and mortality worldwide. Initial antibiotic therapy in upper and lower respiratory tract infections is usually empirical. The increasing evidence of antibacterial resistance in the pathogens commonly associated with pneumonia has raised concerns about the efficacy of currently available therapies and poses a challenge to clinicians. Gemifloxacin is a synthetic fluoroquinolone antimicrobial agent exhibiting potent activity against most Gram negative and Gram positive organisms. Hence, this study was planned to evaluate the efficacy of gemifloxacin as an empirical therapy in pneumonia.

MATERIALS AND METHODS

This was an open labelled, single-arm study. Patients with clinical features of community acquired pneumonia (CAP) who fulfilled the inclusion criteria received treatment with oral gemifloxacin 320 mg once daily for 5-7 days. Once enrolled in the study, patients were treated as outpatient or as inpatient depending on clinical need. The primary efficacy was to evaluate the clinical response at the end of therapy, i.e., day 9-11 for CAP. Secondary efficacy parameters included radiological and bacteriological response at the end of therapy. Patients were evaluated three times during the entire course of treatment (Visit 1, Day 0; Visit 2, Day 2-4; Visit 3, Day 9-11) for their clinical, radiological and/or bacteriological response, as well as for safety assessment.

RESULTS

A total of 105 patients received the study medication (gemifloxacin 320 mg orally). Two patients were "lost to follow-up" and one patient had to discontinue medication due to insufficient therapeutic effects. Clinical response at the end of therapy was successful in 99 (96.1%) while clinical failure was reported in 4 (3.9%) patient. As per the radiological response, 77.1% of the total cases showed improvement, 8.6% had no change, and 2.9% cases had deterioration in radiological findings. Gemifloxacin is an effective drug in the management of CAP.

CONCLUSIONS

Gemifloxacin with coverage against both Gram positive and Gram negative organisms as well as atypical pathogens, with once daily oral dosing and minimum side effect is a very effective and economical choice for treating CAP empirically.

Impact of penicillin nonsusceptibility on clinical outcomes of patients with nonmeningeal Streptococcus pneumoniae bacteremia in the era of the 2008 clinical and laboratory standards institute penicillin breakpoints

To investigate the impact of penicillin nonsusceptibility on clinical outcomes of patients with nonmeningeal Streptococcus pneumoniae bacteremia (SPB), a retrospective cohort study was performed. The characteristics of 39 patients with penicillin-nonsusceptible SPB (PNSPB) were compared to those of a group of age- and sex-matched patients (n = 78) with penicillin-susceptible SPB (PSSPB). Susceptibility to penicillin was redetermined by using the revised Clinical and Laboratory Standards Institute (CLSI) penicillin breakpoints in CLSI document M100-S18. Although the PNSPB group tended to have more serious initial manifestations than the PSSPB group, the two groups did not differ significantly in terms of their 30-day mortality rates (30.8% versus 23.1%; P = 0.37) or the duration of hospital stay (median number of days, 14 versus 12; P = 0.89). Broad-spectrum antimicrobial agents, such as extended-spectrum cephalosporins, vancomycin, and carbapenem, were frequently used in both the PNSPB and PSSPB groups. Multivariate analysis revealed that ceftriaxone nonsusceptibility (adjusted odds ratio [aOR] = 4.88; 95% confidence interval [CI] = 1.07 to 22.27; P = 0.041) was one of the independent risk factors for 30-day mortality. Thus, when the 2008 CLSI penicillin breakpoints are applied and the current clinical practice of using wide-spectrum empirical antimicrobial agents is pursued, fatal outcomes in patients with nonmeningeal SPB that can be attributed to penicillin nonsusceptibility are likely to be rare. Further studies that examine the clinical impact of ceftriaxone nonsusceptibility in nonmningeal SPB may be warranted.

Guidelines for the management of adult lower respiratory tract infections--summary

This document is an update of Guidelines published in 2005 and now includes scientific publications through to May 2010. It provides evidence-based recommendations for the most common management questions occurring in routine clinical practice in the management of adult patients with LRTI. Topics include management outside hospital, management inside hospital (including community-acquired pneumonia (CAP), acute exacerbations of COPD (AECOPD), acute exacerbations of bronchiectasis) and prevention. The target audience for the Guideline is thus all those whose routine practice includes the management of adult LRTI.

Guidelines for the management of adult lower respiratory tract infections--full version

This document is an update of Guidelines published in 2005 and now includes scientific publications through to May 2010. It provides evidence-based recommendations for the most common management questions occurring in routine clinical practice in the management of adult patients with LRTI. Topics include management outside hospital, management inside hospital (including community-acquired pneumonia (CAP), acute exacerbations of COPD (AECOPD), acute exacerbations of bronchiectasis) and prevention. Background sections and graded evidence tables are also included. The target audience for the Guideline is thus all those whose routine practice includes the management of adult LRTI.

Risk factors for 30-day mortality in adult patients with pneumococcal bacteraemia, and the impact of antimicrobial resistance on clinical outcomes

The clinical impact of antimicrobial resistance on the outcome of pneumococcal bacteraemia has remained unclear. This study aimed to evaluate risk factors for mortality and determine the impact of antimicrobial resistance on clinical outcomes. A total of 150 adult patients with pneumococcal bacteraemia were identified over a period of 11 years at Seoul National University Hospital. Of the 150 patients, 122 (81·3%) had penicillin-susceptible (Pen-S) strains and 28 (18·7%) penicillin-non-susceptible (Pen-NS) strains; 43 (28·7%) had erythromycin-susceptible (EM-S) strains and 107 (71·3%) erythromycin-non-susceptible (EM-NS) strains. On multivariate analysis, elevated APACHE II score [odds ratio (OR) 1·24, 95% confidence interval (CI) 1·14–1·34, P<0·001) and presence of solid organ tumour (OR 2·99, 95% CI 1·15–7·80, P=0·025) were independent risk factors for mortality. Neither erythromycin resistance nor penicillin resistance had a significant effect on clinical outcomes. However, for the 76 patients with pneumococcal pneumonia, the time required for defervescence was significantly longer in the EM-NS group than in the EM-S group (5·45±4·39 vs. 2·93±2·56, P=0·03 by log rank test). In conclusion, antimicrobial resistance does not have an effect on mortality in adult patients with pneumococcal bacteraemia.

Drug-resistance in Streptococcus pneumoniae isolates among Spanish middle aged and older adults with community-acquired pneumonia

Background

Pneumococcal diseases remain a major cause of morbidity and mortality worldwide. Updated data on drug-resistance from different populations may be important to recognize changes in disease patterns. This study assessed current levels of penicilin resistance among Streptococcus Pneumoniae causing pneumonia in Spanish middle age and older adults.

Methods

Antimicrobial susceptibility was tested for 104 consecutive isolates of Streptococcus pneumoniae recovered from patients 50 years or older with radiographically confirmed pneumonia in the region of Tarragona (Spain) between 2002 and 2007. According to the minimum inhibitory concentration of tested antimicrobials (penicillin, erythromycin, cefotaxime and levofloxacin) strains were classified as susceptible or resistant. Antimicrobial resistance was determined for early cases (2002–2004) and contemporary cases (2005–2007).

Results

Twenty-seven (25.9%) were penicillin-resistant strains (19 strains with intermediate resistance and 8 strains with high resistance). Penicillin-resistance was higher in 2002–2004 than in 2005–2007 (39.5% vs 18.2%, p = 0.017).

Of 27 penicillin-resistant strains, 10 (37%) were resistant to erythromycin, 8 (29.6%) to cefotaxime, 2 (7.4%) to levofloxacin, and 4 (14.8%) were identified as multidrug resistant. Case-fatality rate was higher among those patients who had an infection caused by any penicillin susceptible strain (16.9%) than in those with infections due to penicillin-resistant strains.

Conclusion

Resistance to penicillin among Streptococcus pneumoniae remains high, but such resistance does not result in increased mortality in patients with pneumococcal pneumonia.

Pneumococcal antimicrobial resistance: therapeutic strategy and management in community-acquired pneumonia

Streptococcus pneumoniae has been consistently shown to represent the most frequent causative agent of community-acquired pneumonia (CAP) and pneumococcal antibiotic resistance towards different families of antibiotics continues to be a much-debated issue. Microbial resistance causes a great deal of confusion in choosing an empirical treatment for pneumonia and this makes it necessary to know which factors actually determine the real impact of antimicrobial resistance on the outcome of pneumococcal infections. Several different aspects have to be taken into account when analyzing this matter, such as the study design, the condition of the patient at the time of diagnosis, the choice of the initial antimicrobial regimen (combination or monotherapy) and the pharmacokinetic/pharmacodynamic variables of the chosen antibiotic. It is generally accepted that in the treatment of beta-lactam-resistant pneumococcal infections, the use of standard antipneumococcal beta-lactam agents is unlikely to impact negatively on the outcome of CAP when appropriate agents are given in sufficient doses. As a general rule, for infections with penicillin-sensitive strains, penicillin or an aminopenicillin in a standard dosage will be effective; in the cases of strains with intermediate resistance, beta-lactam agents are still considered appropriate treatment although higher dosages are recommended; finally, 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 areas of high prevalence of high-level macrolide resistance, empirical monotherapy with a macrolide is not optimal for the treatment of hospitalised patients with moderate or moderately-severe CAP. Fluoroquinolones are considered to be excellent antibiotics in the treatment of pneumococcal CAP in adults, but their general recommendation has been withheld due to fears of a widespread development of resistance. Most international guidelines recommend combination therapy (beta-lactam plus a macrolide) for the treatment of hospitalised patients with CAP.

Multidrug-resistant Streptococcus pneumoniae infections: current and future therapeutic options

Antibacterial resistance in Streptococcus pneumoniae is increasing worldwide, affecting principally beta-lactams and macrolides (prevalence ranging between approximately 1% and 90% depending on the geographical area). Fluoroquinolone resistance has also started to emerge in countries with high level of antibacterial resistance and consumption. Of more concern, 40% of pneumococci display multi-drug resistant phenotypes, again with highly variable prevalence among countries. Infections caused by resistant pneumococci can still be treated using first-line antibacterials (beta-lactams), provided the dosage is optimised to cover less susceptible strains. Macrolides can no longer be used as monotherapy, but are combined with beta-lactams to cover intracellular bacteria. Ketolides could be an alternative, but toxicity issues have recently restricted the use of telithromycin in the US. The so-called respiratory fluoroquinolones offer the advantages of easy administration and a spectrum covering extracellular and intracellular pathogens. However, their broad spectrum raises questions regarding the global risk of resistance selection and their safety profile is far from optimal for wide use in the community. For multi-drug resistant pneumococci, ketolides and fluoroquinolones could be considered. A large number of drugs with activity against these multi-drug resistant strains (cephalosporins, carbapenems, glycopeptides, lipopeptides, ketolides, lincosamides, oxazolidinones, glycylcyclines, quinolones, deformylase inhibitors) are currently in development. Most of them are only new derivatives in existing classes, with improved intrinsic activity or lower susceptibility to resistance mechanisms. Except for the new fluoroquinolones, these agents are also primarily targeted towards methicillin-resistant Staphylococcus aureus infections; therefore, demonstration of their clinical efficacy in the management of pneumococcal infections is still awaited.

Setting and revising antibacterial susceptibility breakpoints

Clinical microbiology laboratories need to communicate results of antibacterial susceptibility testing to prescribers. Sophisticated prescribers who are knowledgeable of the pharmacokinetics and pharmacodynamics of antibacterials may desire no more information than the MIC of the drug in question. However, most prescribers require interpretation of antibacterial susceptibility testing results. Breakpoints can assist in determining if an antibacterial is potentially useful in the treatment of a bacterial infection. Breakpoints should be set prior to an antibacterial being used clinically. Breakpoint setting requires integration of knowledge of the wild-type distribution of MICs, assessment of the pharmacokinetics/pharmacodynamics of the antibacterial, and study of the clinical outcome of infections when the antibacterial is used. It is mandatory that breakpoints be reviewed when antibacterial agents have been in clinical use for some time, particularly if mechanisms of bacterial resistance to the drug have been described. In general, greater amounts of information on the pharmacokinetics and pharmacodynamics of an antibacterial are available when breakpoints need to be revised. However, the opportunity to conduct randomized clinical studies of an antibacterial declines after the drug has been released commercially. Well-designed observational clinical studies are therefore necessary in order to provide reliable data to inform those reevaluating breakpoints. Breakpoint-setting organizations may also play a role in developing phenotypic tests for detection of resistance mechanisms, as this information may complement use of the breakpoint in some circumstances.

Penicillin Resistance Not a Factor in Outcome from Invasive Streptococcus pneumoniae Community-Acquired Pneumonia in Adults When Appropriate Empiric Therapy Is Started

BACKGROUND

Invasive Streptococcus pneumoniae pneumonia among adults due to penicillin-resistant or intermediate resistant strains was investigated to determine whether these patients responded poorly to common antibiotic regimens compared to pneumonia due to susceptible strains.

METHODS

During a 21-year period (1983-2003), clinical outcome was analyzed among 3 groups of adults, 19 with resistant, 33 with intermediate, and 133 with susceptible invasive S pneumoniae pneumonia admitted to hospitals in Huntington, West Virginia. Adults with resistant and intermediate infections were matched by age and month of admission to a group of 133 adults with penicillin-susceptible infections. All isolates of resistant and intermediate infections were capsular serotypes/serogroups 6, 9, 14, 19, and 23, and isolates of susceptible infections included 24 different serotypes/serogroups. Case fatality rates were calculated for deaths that occurred during the first 7, first 14, and first 21 days of hospitalization. Minimal inhibitory concentration (MIC) was determined by E-test and capsular serotype by Quellung procedures.

RESULTS

The resistant and susceptible groups did not differ in several measures of severity of illness, including admission vital signs, duration of fever, mean total leukocyte count, number of lobes involved, preexisting underlying diseases, and antibiotic treatment regimens. There were no significant differences in case fatality rates between the 3 groups of pneumonia by days in hospital, age, severity of illness, and empiric antibiotic treatment regimen with a cephalosporin and a macrolide, the most common antibiotic regimen.

CONCLUSIONS

These findings provide evidence that combination antibiotic regimens effective in the treatment of invasive susceptible S pneumoniae pneumonia are equally effective in the treatment of invasive resistant (MIC = 2-4 microg/mL) and of intermediate (MIC = 0.1-1 microg/mL) S pneumoniae pneumonia.

Optimizing the management of community-acquired respiratory tract infections in the age of antimicrobial resistance

Community-acquired respiratory tract infections (CARTIs) are the most common reason for prescribing antibiotics in the primary care setting. However, over the last decade, the management of CARTIs has become increasingly complicated by the steady increase in prevalence of drug-resistant pathogens responsible for these infections. As a result, significant attention has been directed at understanding the mechanisms of pathogen acquisition of resistance, drivers of resistance and methods for preventing the development of resistance. Data from recent surveillance studies suggest a slowing or decline in resistance rates to agents, such as beta-lactams, macrolides, tetracyclines and folic acid metabolism inhibitors. However, resistance to one antimicrobial family--the fluoroquinolones--while still low, appears to be on the increase. This is of significant concern given the rapid increase in resistance noted with older antibiotics in recent history. While the clinical implications of antibacterial resistance are poorly understood, the overall rates of antimicrobial resistance, as reported in recent surveillance studies, do not correspond to current rates of failure in patients with CARTIs. This disconnection between laboratory-determined resistance and clinical outcome has been termed the in vitro-in vivo paradox and several explanations have been offered to explain this phenomenon. Solving the problem of antimicrobial resistance will be multifactorial. Important factors in this effort include the education of healthcare providers, patients and the general healthcare community regarding the hazards of inappropriate antibiotic use, prevention of infections through vaccination, development of accurate, inexpensive and timely point-of-care diagnostic tests to aid in patient assessment, institution of objective treatment guidelines and use of more potent agents, especially those with a focused spectrum of activity, earlier in the treatment of CARTIs as opposed to reserving them as second-line treatment options. Ultimately, the single-most important factor will be the judicious use of antibiotics, as fewer antibiotic prescriptions lead to fewer antimicrobial-resistant bacteria.

Severe pneumococcal pneumonia: new strategies for management

PURPOSE OF REVIEW

Streptococcus pneumoniae is the leading cause of community-acquired pneumonia worldwide and is the most likely causative pathogen in patients with community-acquired pneumonia admitted to the intensive care unit. Bacteremic pneumococcal pneumonia is an advanced stage of severe pneumococcal pneumonia. Improvement in the management of bacteremic pneumococcal pneumonia has the potential for improving the survival for severe pneumococcal pneumonia.

RECENT FINDINGS

Non-culture methods, especially the Binax urinary antigen test, can increase the diagnostic yield for pneumococcal pneumonia, allowing targeted antimicrobial therapy (specifically penicillin). In-vitro resistance to penicillin has increased over the past decade; however, it has not led to clinical failure when used for pneumococcal pneumonia.

SUMMARY

Hospitalized patients with community-acquired pneumonia should have blood cultures obtained to confirm the possibility of bacteremic pneumococcal pneumonia. Based on pharmacodynamic properties, parenteral penicillin remains the drug of choice to treat pneumococcal pneumonia regardless of in-vitro resistance. Combination antimicrobial therapy will likely improve survival of patients with bacteremic pneumococcal pneumonia among the subset of critically ill patients.

Impact of initial discordant treatment with beta-lactam antibiotics on clinical outcomes in adults with pneumococcal pneumonia: a systematic review

OBJECTIVE

To systematically examine the available evidence regarding the effect of initial discordant therapy with beta-lactam antibiotics on mortality, clinical success, and bacteriological eradication in patients with pneumococcal pneumonia.

METHODS

We analyzed prospective studies that compared the clinical effectiveness of concordant (active in vitro) beta-lactam monotherapy with discordant (inactive in vitro) monotherapy with the same beta-lactam in patients with pneumococcal pneumonia. Relevant studies were identified from searches of the PubMed database (1950 to November 2005) and references from articles. Outcomes between groups of patients who received concordant and discordant treatment were compared by simple pooling of data and by estimation of pooled odds ratios or risk difference (RD), when applicable.

RESULTS

Six prospective studies were included in our analysis. No statistically significant difference was found in mortality of patients treated with beta-Iactam concordant and discordant therapy (51/275 [19%] vs 9/42 [21%]; P = .66; data from 6 studies; RD, -0.05; 95% confidence interval [CI], -0.23 to 0.12; data from 5 studies). In addition, no statistically significant difference was found regarding clinical success (37/42 [88%] vs 5/6 [83%]; P = .57; odds ratio, 2.57; 95% CI, 0.46 to 14.34; RD, 0.07; 95% CI, -0.36 to 0.50; data from 3 studies) or bacteriological success (24/30 [80%] vs 3/3 [100%]; P = .99; and RD, -0.18; 95% CI, -0.79 to 0.42; data from 2 studies) between concordant and discordant therapy.

CONCLUSION

The initial discordant treatment with beta-lactam antibiotics was not associated with a statistically significant Increase in mortality or clinical or bacteriological failure of therapy for pneumococcal pneumonia.

[Antibiotherapy for acute CAP in adults]

Community acquired pneumonia is one of the most frequent infections. With time, bacterial epidemiology and bacterial resistance evolve and new antibiotics become available. So an up-date on adequate antibiotic use is necessary. We reviewed the epidemiology of pneumonia and the evolution of bacterial resistance. We also collected data on new antibiotics which can be used for this infection such as levofloxacin, moxifloxacin, telithromycin, and pristinamycin. All these drugs are effective on bacteria involved in pneumonia. At this time, only few Streptococcus pneumoniae strains have developed resistance to these drugs. However, resistance to fluoroquinolones is not easily detected with common laboratory techniques. There is no effectiveness difference between the 2 new fluoroquinolones (levofloxacin, moxifloxacin) in clinical studies. However, in bacteriological and pharmacological studies, moxifloxacin seems to be more effective than levofloxacin (500 mg/day). For the treatment of pneumonia due to Legionella pneumophila, fluoroquinolones are now widely recommended. For Streptococcus pneumonia, amoxicillin remain the drug of choice, even for bacteria with a decreased susceptibility to penicillin. The importance of treating atypical pathogens remains to be documented.

Resource utilization of adults admitted to a large urban hospital with community-acquired pneumonia caused by Streptococcus pneumoniae

OBJECTIVE

To determine if penicillin-nonsusceptible Streptococcus pneumoniae, among other variables, was significantly associated with greater hospital costs among patients with community-acquired pneumonia (CAP).

DESIGN

Retrospective, cohort study.

SETTING

Eight hundred ten-bed, urban, private, teaching hospital.

PATIENTS

Adult patients admitted between 1999 and 2003 with CAP caused by S pneumoniae.

INTERVENTION

Clinical criteria and costs (inflated to 2004 dollars) were collected from the medical charts and detailed hospital bills for each individual patient. Costs were compared according to classification by penicillin susceptibility. Multivariate linear regression was utilized to determine variables independently associated with increased hospital costs and length of stay.

RESULTS

Of 168 patients included, 44 patients (26%) had CAP caused by penicillin-nonsusceptible S pneumoniae. Median total hospital costs were 8,654 dollars (25th to 75th percentile, 5,457 dollars to 16,027 dollars), with no difference between susceptible and nonsusceptible groups. Bed costs accounted for 55.6% of total costs, followed by laboratory (9.9%) and pharmacy (9.8%) costs. Regression analyses determined that ICU admission (p < 0.001), unexplained delays in discharge (p = 0.001), and neoplasm (p < 0.04) were independently predictive of both total hospital costs (adjusted r2 = 0.46) and increasing length of stay (adjusted r2 = 0.30). Hospital mortality, bacteremia, and congestive heart failure were also associated with at least one of the dependent variables.

CONCLUSION

In the current era in which more potent antibiotics are empirically utilized to treat CAP, it does not appear that a simple classification of penicillin nonsusceptibility complicates the economic impact of S pneumoniae infection. Focused efforts to reduce length of stay, including minimizing prolonged and unnecessary observation of patients, should have the most profound effect on reducing total costs.

Hospitalized community-acquired pneumonia due to Streptococcus pneumoniae: Has resistance to antibiotics decreased?

STUDY OBJECTIVES

To determine the incidence and trends of pneumococcal community-acquired pneumonia (CAP) resistant to antibiotics, to describe clinical and microbiological features of pneumococcal CAP, and to ascertain prognostic risk factors in a third-level hospital.

DESIGN AND SETTING

We performed a prospective study of all well-defined pneumococcal CAP hospitalizations in the Hospital Clínic de Barcelona (Spain) over 2 years of follow-up, and results were compared with a previous study.

MEASUREMENTS AND RESULTS

One hundred twenty-five patients were included (mean age, 59.6 years; 71.2% male and 28.8% female). Mortality was 7% (n = 9). Twenty-four percent were HIV-1 seropositive (n = 30), and 53% had at least one comorbidity (n = 65). Nonsusceptibility to penicillin, ceftriaxone, and erythromycin accounted for 34%, 9%, and 33%, respectively. A decrease in penicillin (p = 0.01) and cephalosporin (p < 0.001) resistance was observed on comparison with a previous study, while macrolide resistance remained unchanged. Serotype 1 infection was overrepresented (8%, n = 10). A bad outcome was related to female gender (relative risk [RR], 9.1; confidence interval [CI], 1.3 to 61.3), pleural effusion (RR, 13.35; CI, 1.9 to 93.1), and prior oral corticoid intake (RR, 10.59; CI, 1.2 to 91.2), whereas drug-resistant strains were not.

CONCLUSIONS

We found a decrease in drug resistance compared with a previous report and a relatively high incidence of serotype 1 pneumococcal CAP. We also observed a high prevalence of HIV-1 infection among individuals with pneumococcal pneumonia. We confirm the lack of association of drug resistance with mortality and length of hospitalization. Mortality was associated with female gender, pleural effusion, and previous oral corticoid treatment. These results should be better ascertained in further studies.

Controversies in the treatment of pneumococcal community-acquired pneumonia

Community-acquired pneumonia remains an important cause of disease and death both in the developed and the developing worlds, despite the ready availability of potent antimicrobial agents to which the organisms remain susceptible. Furthermore, disease management is complicated by emerging resistance of the common pathogens to the various classes of commonly prescribed antimicrobial agents. Much recent research in the field of community-acquired pneumonia has focused attention on optimal treatment, evaluating the impact of antibiotic resistance, as well as of antimicrobial choices, on the outcome of these infections. In addition, efforts have been directed towards finding adjunctive therapies to antibiotics that may improve the prognosis of these patients. This article reviews some of these research areas, highlighting controversies that still exist with regard to final recommendations, and in particular with regard to infections with Streptococcus pneumoniae, the most common bacterial cause of community-acquired pneumonia.

Clinical outcomes of bacteremic pneumococcal infections in an area with high resistance

In a retrospective study designed to gather information in a region with high antimicrobial resistance, the outcomes of 216 episodes of laboratory-confirmed pneumococcal bacteremia treated in Hong Kong between 1995 and 2001 were assessed. The patients had a mean age (+/-standard deviation) of 40+/-33.7 years. In all patients, the clinical diagnosis was confirmed by isolation of Streptococcus pneumoniae from blood (n=216), cerebrospinal fluid (n=7) and/or other sterile sites (n=12). Penicillin nonsusceptibility was found in 37.5% of the isolates (20.8% intermediate and 16.7% resistant). Penicillin nonsusceptibility was not a risk factor for inpatient mortality (p=0.7), nor did it affect duration of fever (p=0.4), requirement for intensive care unit admission (p=0.4) or development of suppurative complications (p=0.2). Advanced age (OR 11.3, 95%CI 4.5-28.2, p<0.01), critical illness (OR 11.3, 95%CI 4.5-28.2, p<0.001) and discordant therapy (OR 4.3, 95%CI 1.7-10.9, p<0.002) involving agents with poor anti-pneumococcal activity (but not penicillins and broad-spectrum beta-lactam agents) were significantly associated with mortality.

Managing acute lower respiratory tract infections in an era of antibacterial resistance

Respiratory tract infections account for more than 116 million office visits and an estimated 3 million visits to hospital EDs annually. Patients presenting at EDs with symptoms suggestive of lower respiratory tract infections of suspected bacterial etiology are often severely ill, thus requiring a rapid presumptive diagnosis and empiric antimicrobial treatment. Traditionally, clinicians have relied on beta-lactam or macrolide antibiotics to manage community-acquired lower respiratory tract infections. However, the emerging resistance of Streptococcus pneumoniae to beta-lactams and/or macrolides may affect the clinical efficacy of these agents. Inappropriate use of antibiotics and use of agents with an overly broad spectrum of antimicrobial activity have contributed to the emergence of antibiotic resistance. When treating respiratory infections, clinicians need to prescribe antimicrobial agents only for those individuals with infections of suspected bacterial etiology; to select agents with a targeted spectrum of activity that ensures coverage against typical S pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis strains, including antibiotic-resistant strains and atypical pathogens; and to consider agents with specific chemical properties that limit the development of antimicrobial resistance and that achieve concentrations at sites of infection that exceed those required for bactericidal activity. Newer classes of antimicrobial agents, such as the oxazolidinones and ketolides, will likely play a significant role in this era of antimicrobial resistance.

The Impact of Penicillin Resistance on Short-Term Mortality in Hospitalized Adults with Pneumococcal Pneumonia: A Systematic Review and Meta-Analysis

BACKGROUND

The clinical impact of penicillin resistance on the outcome of pneumococcal pneumonia has remained controversial. We performed a meta-analysis of prospective cohort studies to examine the association between penicillin resistance and short-term all-cause mortality for pneumococcal pneumonia.

METHODS

We retrieved studies published in any language by a comprehensive search of the Medline, Current Contents, and Embase databases for all appropriate articles published up to January 2005. We also manually reviewed bibliographies of retrieved articles, recent national treatment guidelines, and review articles. We included prospective cohort studies that involved adult subjects, and we examined the association between penicillin resistance and short-term mortality for pneumococcal pneumonia. Two reviewers independently extracted data on crude and adjusted risk estimates of all-cause mortality for pneumococcal infections with different levels of penicillin resistance and assessed the methodological quality of selected studies. We also contacted authors to obtain additional information. We performed meta-analyses using a random-effect model.

RESULTS

Of 1152 articles identified in the search, 10 studies that involved 3430 patients (most of whom were hospitalized) were included. The mortality rate was 19.4% in the penicillin-nonsusceptible Streptococcus pneumoniae group and 15.7% in the penicillin-susceptible S. pneumoniae group. The combined relative risks of all-cause mortality for the penicillin-nonsusceptible, -intermediate, and -resistant S. pneumoniae groups, compared with the penicillin-susceptible S. pneumoniae group, were 1.31 (95% confidence interval [CI], 1.08-1.59), 1.34 (95% CI, 1.13-1.60), and 1.29 (95% CI, 1.01-1.66), respectively. The combined adjusted relative risks of mortality for penicillin-nonsusceptible versus penicillin-susceptible S. pneumoniae group was 1.29 (95% CI, 1.04-1.59) for the 6 studies that adjusted for age, comorbidities, and severity of illness. There was minimal between-study heterogeneity in these analyses.

CONCLUSION

Penicillin resistance is associated with a higher mortality rate than is penicillin susceptibility in hospitalized patients with pneumococcal pneumonia. Additional efforts are needed to understand the mechanisms of this association.

Penicillins for Treatment of Pneumococcal Pneumonia: Does In Vitro Resistance Really Matter?

BACKGROUND

The rate of in vitro bacterial resistance to antimicrobial agents is escalating among pathogens that cause the most serious respiratory tract infections. Many reports published during the past few years suggest that this has direct clinical implications. In particular, resistance of Streptococcus pneumoniae to beta-lactam antibiotic therapy has assumed a prominent role in the evolution of guidelines for the initial treatment of respiratory tract infection.

METHODS

I conducted a critical review of the published medical literature.

RESULTS

There is only a single report of documented microbiologic failure of parenteral penicillin-class antibiotics in the treatment of pneumococcal pneumonia in patients with or without bacteremia, whereas there are numerous well-documented reports of treatment failure with quinolone-class (n > or = 21) and macrolide-class (n > or = 33) antibiotics in the treatment of pneumococcal pneumonia.

CONCLUSION

The recommended optimal in-hospital therapy for community-acquired pneumonia should continue to be a beta-lactam antibiotic (penicillin, aminopenicillin, cefotaxime, or ceftriaxone) administered with a macrolide or a fluoroquinolone agent for adjunctive treatment of infection with potential atypical pathogens.

Sinn und Unsinn der Antibiotikatherapie respiratorischer Infekte

Whether an antibiotic successfully eradicates pathogens depends on the pathogens involved, on pharmacokinetics and bioavailability in the target tissue, and on the antimicrobial resistance of the pathogen. Other determinants are drug interactions, individual risk factors, age and compliance with respect to correct dosage and duration of therapy. In many cases, antimicrobial therapy is begun on an empirical basis, because the responsible pathogen can be identified in only half of all respiratory infections. The eradication of the pathogen has to be the first aim if treatment is to be curative and the development of resistance prevented. Long-term prevention of antimicrobial resistance will require a more critical prospective evaluation of the prescription of antibiotics. This paper considers rational and irrational measures in the antimicrobial therapy of respiratory infections.