Surveillance of antimicrobial resistance in Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis in the United States in 1996-1997 respiratory season. The Laboratory Investigator Group

Antimicrobial Susceptibility Survey of Invasive Haemophilus influenzae in the United States in 2016

Antibiotics are important for the treatment and prevention of invasive Haemophilus influenzae disease. Reduced susceptibility to clinically relevant drugs, except ampicillin, has been uncommon in the United States. Susceptibility of 700 invasive H. influenzae isolates, collected through population-based surveillance during 2016, was assessed for 15 antibiotics using broth microdilution, according to the CLSI guidelines; a subset of 104 isolates were also assessed for rifampin susceptibility using Etest. Genomes were sequenced to identify genes and mutations known to be associated with reduced susceptibility to clinically relevant drugs. A total of 508 (72.6%) had reduced susceptibility to at least one antibiotic and more than half of the isolates exhibited reduced susceptibility to only one (33.6%) or two (21.6%) antibiotic classes. All tested isolates were susceptible to rifampin, a chemoprophylaxis agent, and <1% (n = 3) of isolates had reduced susceptibility to third generation cephalosporins, which are recommended for invasive disease treatment. In contrast, ampicillin resistance was more common (28.1%) and predominantly associated with the detection of a β-lactamase gene; 26.2% of isolates in the collection contained either a TEM-1 or ROB-1 β-lactamase gene, including 88.8% of ampicillin-resistant isolates. β-lactamase negative ampicillin-resistant (BLNAR) isolates were less common and associated with ftsI mutations; resistance to amoxicillin-clavulanate was detected in <2% (n = 13) of isolates. The proportion of reduced susceptibility observed was higher among nontypeable H. influenzae and serotype e than other serotypes. US invasive H. influenzae isolates remain predominantly susceptible to clinically relevant antibiotics except ampicillin, and BLNAR isolates remain uncommon. IMPORTANCE Antibiotics play an important role for the treatment and prevention of invasive Haemophilus influenzae disease. Antimicrobial resistance survey of invasive H. influenzae isolates collected in 2016 showed that the US H. influenzae population remained susceptible to clinically relevant antibiotics, except for ampicillin. Detection of approximately a quarter ampicillin-resistant and β-lactamase containing strains demonstrates that resistance mechanisms can be acquired and sustained within the H. influenzae population, highlighting the continued importance of antimicrobial resistance surveillance for H. influenzae to monitor susceptibility trends and mechanisms of resistance.

High Prevalence of Antibiotic Resistance in Isolates from the Middle Meatus of Children and Adults with Acute Rhinosinusitis

Background

The pathogens in acute rhinosinusitis are similar worldwide. An increase in antibiotic resistance has been shown in a large number of studies in recent years. The prevalence of resistance varies greatly in different countries. This study was performed to determine the endemic prevalence of antibiotic resistance in pathogens of acute rhinosinusitis in Taiwan.

Methods

Middle meatus discharge was taken for aerobic culture in 133 outpatients with the diagnosis of acute rhinosinusitis.

Results

One hundred two isolates of pathogens were found, including three major bacteria: Haemophilus influenzae (37.3%), Streptococcus pneumoniae (28.4%), and Moraxella catarrhalis (11.8%). Polymicrobial infections and positive cultures occurred more frequently in pediatric patients, as did recovery of M. catarrhalis infection. An extremely high percentage of resistance to first-line antibiotics was noted, viz., penicillin-nonsusceptible S. pneumoniae (PNSSP) (72.4%), ampicillin-resistant H. influenzae (60.5%), and M. catarrhalis (58.3%).

Conclusion

The high prevalence of drug resistance is a great threat to public health. Antibiotic use should be more prudent, especially in pediatric patients, who were found to be more susceptible to bacterial rhinosinusitis and multiple pathogenic infection.

High-Level Macrolide-Resistant Moraxella catarrhalis and Development of an Allele-Specific PCR Assay for Detection of 23S rRNA Gene A2330T Mutation: A Three-Year Study at a Chinese Tertiary Hospital

Previous studies indicate that macrolide resistance in Moraxella catarrhalis isolates is less common in adults than in children. However, few studies have investigated M. catarrhalis macrolide resistance mechanisms in adult patients. In this study, 124 M. catarrhalis isolates were collected from adult patients in a Chinese tertiary hospital, between 2010 and 2013, and investigated for antimicrobial resistance. We found that only seven isolates were macrolide resistant and all exhibited high-level macrolide resistance (minimum inhibitory concentrations >256 μg/ml). Multilocus sequence typing (MLST) suggested that M. catarrhalis has a diverse population; in particular, both pulsed-field gel electrophoresis and MLST revealed that all the seven high-level macrolide-resistant M. catarrhalis belonged to different clones. A 934-bp 23S rRNA gene sequencing showed that only nine isolates (including all the seven macrolide-resistant isolates) had mutations within the studied region, and only the seven macrolide-resistant isolates had mutation of A2330T. No other known macrolide-resistance determinant genes (ermA, ermB, mefA, or mefE) were detected. These findings support previous studies in children on M. catarrhalis macrolide-resistant isolates and suggest that the 23S rRNA gene A2330T mutation is responsible for the high M. catarrhalis macrolide resistance. The findings prompted us to successfully develop a simple allele-specific polymerase chain reaction assay for high-level macrolide-resistant 23S rRNA gene A2330T mutation for future clinical and further surveillance use.

The importance and future of antimicrobial surveillance studies

Surveillance studies provide important information that allows for the identification of trends in pathogen incidence and antimicrobial resistance, including identification of emerging pathogens at national and global levels. Routine surveillance is critical for creating and refining approaches to controlling antimicrobial resistance and for guiding clinician decisions regarding appropriate treatment. The traditional approach has been to monitor pathogen antimicrobial susceptibility; numerous large studies have been performed, and their designs have evolved over time. Longitudinal studies are particularly useful because important information can be obtained by comparing data over time. Another approach to surveillance, that of monitoring antimicrobial use, can help to identify trends in dosing, to prevent the development of resistance. Several studies have incorporated this approach into their methods, and both large and small studies have attempted to correlate antimicrobial use data with antimicrobial resistance data. Overall, care must be taken to coordinate programs for optimal utilization of resources, to avoid duplication of effort.

Streptococcus pneumoniae: An Update on Resistance Patterns in the United States

Streptococcus pneumoniae represents an important pathogen in numerous community-acquired respiratory infections. Penicillin resistance to Streptococcus pneumoniae in the United States has approached 35%. Additionally, there has been a significant increase in Streptococcus pneumoniae resistance among many other antimicrobial agents such as cephalosporins, macrolides, trimethoprim–sulfamethoxazole, clindamycin, tetracyclines, and chloramphenicol. Several nationwide surveillance programs have been implemented to quantify the prevalence of Streptococcus pneumoniae resistance in the United States. Overall, beta-lactam, macrolide, trimethoprim–sulfamethoxazole, and tetracycline resistance has increased over the past decade while later generation fluoroquinolones (levofloxacin and moxifloxacin) resistance has remained low. Controlling the spread of resistant pneumococcal isolates and preventing the development of both fluoroquinolone and multidrug resistant isolates will require a multidisciplinary approach involving physicians, pharmacists, microbiologists, and epidemiologists.

Oral garenoxacin in the treatment of acute bacterial maxillary sinusitis: a Phase II, multicenter, noncomparative, open-label study in adult patients undergoing sinus aspiration

BACKGROUND

Garenoxacin is a des-F(6)-quinolone with in vitro activity against key respiratory pathogens, including Streptococcus pneumoniae, Hemophilus influenzae, Staphylococcus aureus, and Moraxella catarrhalis. Limited data are available regarding the effect of garenoxacin in the treatment of acute bacterial sinusitis.

OBJECTIVE

The aim of this study was to assess the efficacy and tolerability of garenoxacin in adults with acute bacterial maxillary sinusitis undergoing a pre-treatment diagnostic sinus aspirate.

METHODS

This Phase II, multicenter, noncomparative, open-label study was conducted at 30 centers in the United States, Mexico, Argentina, and Europe. Male and female patients aged 18 to 80 years with clinical signs and symptoms lasting >or=5 but <or=28 days and radiologic signs (air-fluid level, opacification, mucosal thickening) of acute maxillary sinusitis were eligible. The entry criteria for the 5-day treatment regimen did not include mucosal thickening of >or=5 mm because it was believed that improvement in mucosal thickening might not be reliably measurable at the 5-day time point. All patients received garenoxacin 400 mg QD for 5 or 10 days. Maxillary sinus needle aspiration for Gram stain, routine culture, and susceptibility testing were performed before treatment, and, if clinically indicated, during and after treatment. Bacteriologic eradication (negative culture on repeat sinus aspiration) and cure rates (complete resolution of all signs and symptoms) were assessed at a test-of-cure visit 5 to 18 days after the end of treatment. The occurrence of adverse events was recorded by the investigators up to 30 days after the last administration of garenoxacin by questioning patients.

RESULTS

A total of 546 patients were enrolled and 543 were randomized (5-day cohort: mean age, 40 years; mean weight, 76 kg; 56% women; 10-day cohort: mean age, 41 years; mean weight, 77 kg; 58% women). Clinically evaluable patients included 253 in the 5-day cohort and 266 in the 10-day cohort. Cure rates were 93% (236/253; 95% CI, 89%-96%) and 91% (243/266; 95% CI, 87%-94%) for evaluable patients in the 5- and 10-day cohorts, respectively. Bacteriologic eradication rates in microbiologically evaluable patients were 94% in both cohorts (5 days, 204/217; 10 days, 182/193). Eradication rates in the 5- and 10-day cohorts were as follows: S pneumoniae, 94% (62/66) and 93% (39/42); H influenzae, 100% (30/30) and 93% (26/28); S aureus, 96% (23/24) and 91% (31/34); and M catarrhalis, 89% (8/9) and 86% (12/14). Of the 9 patients with acute bacterial sinusitis due to multidrug-resistant S pneumoniae, 8 achieved clinical cure with garenoxacin treatment. Adverse events (AEs) most frequently reported were diarrhea (<or=2%), nausea (2%-6%), headache (2%-6%), and dizziness (<or=2%). Two percent of patients withdrew because of an AE (allergic reaction, adverse gastrointestinal effects, dyspnea, dizziness, headache, or elevation in liver enzymes).

CONCLUSION

In this population of patients with signs and symptoms of acute maxillary sinusitis, oral garenoxacin 400 mg QD for 5 or 10 days eradicated 94% of bacterial pathogens associated with acute bacterial sinusitis in this population and appeared to be well tolerated in adults.

Reduction in pediatric invasive pneumococcal disease in the Basque Country and Navarre, Spain, after introduction of the heptavalent pneumococcal conjugate vaccine

This study evaluated the incidence of invasive pneumococcal disease, identified the causal serotypes, and tracked the evolution of the antibiotic susceptibility of Streptococcus pneumoniae isolates in the regions of the Basque Country and Navarre, Spain, before and after the introduction of the heptavalent pneumococcal conjugate vaccine. The study included all children aged between birth and 5 years diagnosed with bacteremia, meningitis, or bacteremic pneumonia caused by pneumococci. By the second year after introduction of the heptavalent pneumococcal conjugate vaccine, compared with the period 1998-2001, the incidence of invasive disease decreased by 64.3% in children less than 12 months of age, by 39.7% in children less than 24 months of age, and by 37.5% in children less than 60 months of age. The prevalence of clinical isolates of S. pneumoniae that lacked susceptibility to penicillin decreased by 58.2% among children less than 60 months of age. With an estimated coverage by four-dose heptavalent pneumococcal conjugate vaccine of 28-45% in 2003, the number of invasive pneumococcal infections in the Basque Country and in Navarre fell significantly after just 2 years of immunization, underscoring the importance of improving vaccination coverage under a universal childhood immunization program.

Otitis media today: a challenge for physicians and the community

Acute otitis media is one of the most common causes of medical consultation worldwide, and has a high economic impact. In this review, a clear definition between acute otitis media and otitis media with effusion is presented. The microbiology and characterization of the main bacterial isolates in acute otitis media and the susceptibility patterns are reviewed, and the latest concepts in antimicrobial treatment are discussed. The need for courses that improve the capability of primary care physicians to diagnose acute otitis media using pneumatic otoscopy, and for parental education is also discussed.

Gram-positive cocci infections in intensive care: guide to antibacterial selection

The incidence of multiresistance in Gram-positive cocci causing infections in critically ill patients admitted to the intensive care unit (ICU) has increased notably in recent years. Thus, therapeutic proposals have been modified according to the emergence of multiresistant cocci and adapted to epidemiological markers of individual infectious processes, geographical variations of these markers, the availability of new antibacterials, and advances in the knowledge of pharmacokinetic and pharmacodynamic aspects of their use. The current management of critically ill patients should consider new therapeutic approaches, such as the "de-escalating strategy", which includes the administration of empirical antibacterials active against multiresistant pathogens followed by directed treatment based on unequivocal data from antibacterial-susceptibility testing. Optimisation of antibacterial treatment should be viewed in the context of the need to determine plasma drug concentrations, pharmacoeconomic considerations and control of drug-related adverse events. Therapeutic proposals should be developed within the framework of the antibacterial policy of each hospital. The present review is focused on the description of the therapeutic strategies for the main infectious processes caused by Gram-positive cocci in severely ill patients admitted to the ICU according to a review of the pertinent literature and the clinical experience of the authors.

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.

Decreasing prevalence of beta-lactamase production among respiratory tract isolates of Haemophilus influenzae in the United States

A total of 986 isolates of Haemophilus influenzae from patients with respiratory tract infections in 45 United States medical centers were characterized during the winter of 2002-2003. beta-Lactamase production was noted with 26.2% of isolates; 14.6% were resistant to trimethoprim-sulfamethoxazole. Resistance to other relevant antimicrobial agents was extremely uncommon. In comparison to the results of four previous national surveys conducted since 1994, the prevalence of beta-lactamase production with this pathogen appears to be decreasing.

Treatment of rhinosinusitis in the outpatient setting

Rhinosinusitis is one of the most common respiratory tract conditions seen by primary care physicians. Each year approximately 20 million cases of acute bacterial rhinosinusitis (ABRS) occur in the United States. Since diagnosis of ABRS relies on clinical evaluation, treatments are usually empirical and include an antibiotic treatment that covers the common bacteria associated with ABRS infection, Streptococcus pneumoniae and Haemophilus influenzae. The Council for Appropriate and Rational Antibiotic Therapy (CARAT) recommends that antimicrobial therapy for rhinosinusitis should combine high susceptibility, clinical effectiveness, safety, and tolerability. The most efficacious antibiotics for ABRS include the respiratory fluoroquinolones gatifloxacin, levofloxacin, and moxifloxacin, as well as ceftriaxone and amoxicillin-clavulanate. The use of fluoroquinolones or high-dose amoxicillin-clavulanate is recommended for patients with mild disease who have had recent antimicrobial therapy or for patients with moderate disease. These drugs are generally well tolerated with mild adverse effects. Resistance to fluoroquinolones in S pneumoniae and H influenzae has remained low in spite of their increased use. Recent studies indicate that short-course, high-dose treatment regimens may reduce total drug use, improve tolerability and adherence, prevent increases in resistance, and increase efficacy. The use of fluoroquinolones or amoxicillin-clavulanate in a short-course, high-dose regimen may represent an exciting new protocol in the treatment of rhinosinusitis.

Etiology of community-acquired pneumonia

Community-acquired pneumonia (CAP) is a serious lower respiratory tract infection associated with significant morbidity and mortality that is characterized by disputes over diagnostic evaluations and therapeutic decisions. With the widespread use of broad-spectrum antimicrobial agents and the increasing number of immunocompromised hosts, the etiology and the drug resistance patterns of pathogens responsible for CAP have changed. Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis remain the leading causes of CAP in immunocompetent patients. Opportunistic infections with organisms such as Pneumocystis jiroveci and Mycobacterium tuberculosis and other opportunistic fungal pneumonias should also be considered in the differential diagnosis of CAP in immunocompromised patients. This article examines the current peer-reviewed literature on etiology, risk factors, and outcomes of patients with CAP.

Large-scale screen highlights the importance of capsule for virulence in the zoonotic pathogen Streptococcus iniae

Zoonotic pathogens have the unique ability to cross the species barrier, causing disease in both humans and specific animal hosts. Streptococcus iniae is a zoonotic pathogen of both fish and humans, and the clinical presentations of S. iniae infections in fish and humans are very similar to those caused by various human-specific streptococcal pathogens. Virulence mechanisms required for infection by this pathogen of either host have yet to be determined. Using the previously reported zebrafish infectious disease model, we performed a large-scale screening to determine genes required for systemic infection. Screening 1,128 signature-tagged transposon mutants through the zebrafish model allowed identification of 41 potential mutants that were unable to survive within the host environment. Greater than 50% of the mutants that could be identified through homology searches were highly homologous to genes found in other human-specific streptococcal pathogens, while 32% were found to have no homology to any sequences found in the databases, suggesting as yet unknown gram-positive bacterial virulence factors. A large percentage of the insertions were found to be located in several putative capsule synthesis genes, an important virulence component for other systemic pathogens. Density gradient assays demonstrated that several of these putative capsule mutants have dissimilar buoyant densities, suggesting different levels of capsule synthesis. Putative capsule mutants were also less resistant to phagocytosis in whole-blood assays than wild-type S. iniae. Our initial large-scale characterization of S. iniae virulence highlights the importance of the capsule for successful infection.

High nasopharyngeal carriage of drug resistant Streptococcus pneumoniae and Haemophilus influenzae in North Indian schoolchildren

OBJECTIVES

To determine the carriage rate of Streptococcus pneumoniae and Haemophilus influenzae in healthy Indian schoolchildren. The prevalence of antibiotic resistant strains in the community may be used to assess the trends of antibiotic resistance in invasive strains. Prevalence of resistance to various antimicrobial drugs among S. pneumoniae and H. influenzae was estimated.

METHODS

Two thousand four hundred subjects, aged 5-10 years, were enrolled from 45 rural and 45 urban schools. A nasopharyngeal swab was collected from each child, after taking informed written consent. Swabs were processed to isolate S. pneumoniae and H. influenzae. All isolates were tested for resistance to chloramphenicol, erythromycin and co-trimoxazole. Streptococcus pneumoniae isolates were also tested against tetracycline and oxacillin while H. influenzae isolates were tested against ampicillin.

RESULTS

Nasopharyngeal carriage of S. pneumoniae and H. influenzae was high in healthy schoolchildren. Stratified analysis showed that nasal carriage of pneumococci in urban children was significantly lower than in rural children [46.8% vs. 53.2%, P<0.001]. Carriage rates of H. influenzae in male and female populations were significantly different (47.8% vs. 52.3%, P<0.04). Penicillin resistance in S. pneumoniae was found low (3.3%), but 22.9% of H. influenzae isolates were ampicillin resistant. Resistance to co-trimoxazole was very high in both S. pneumoniae (81.8%) and H. influenzae (67.3%).

CONCLUSION

There is high nasopharyngeal carriage of drug resistant S. pneumoniae and H. influenzae in schoolchildren of north India. Currently, in India, co-trimoxazole for 5 days is recommended for treatment of non-severe pneumonia and third generation cephalosporins are drug of choice for management of severe pneumococcal/H. influenzae diseases. We found high co-trimoxazole resistance and low penicillin resistance in pneumococcal isolates. This justifies empirical use of penicillin in management of invasive pneumococcal infections in India.

Role of antimicrobial agents in the management of exacerbations of COPD

Acute exacerbations of chronic obstructive pulmonary disease (AECOPD) are a common occurrence and characterize the natural history of the disease. Over the past decade, new knowledge has substantially enhanced our understanding of the pathogenesis, outcome and natural history of AECOPD. The exacerbations not only greatly reduce the quality of life of these patients, but also result in hospitalization, respiratory failure, and death. The exacerbations are the major cost drivers in consumption of healthcare resources by COPD patients. Although bacterial infections are the most common etiologic agents, the role of viruses in COPD exacerbations is being increasingly recognized. The efficacy of antimicrobial therapy in acute exacerbations has established a causative role for bacterial infections. Recent molecular typing of sputum isolates further supports the role of bacteria in AECOPD. Isolation of a new strain of Haemophilus influenzae, Moraxella catarrhalis, or Streptococcus pneumoniae was associated with a considerable risk of an exacerbation. Lower airway bacterial colonization in stable patients with COPD instigates airway inflammation, which leads to a protracted self-perpetuating vicious circle of progressive lung damage and disease progression. A significant proportion of patients treated for COPD exacerbation demonstrate incomplete recovery, and frequent exacerbations contribute to decline in lung function. The predictors of poor outcome include advanced age, significant impairment of lung function, poor performance status, comorbid conditions and history of previous frequent exacerbations requiring antibacterials or systemic corticosteroids. These high-risk patients, who are likely to harbor organisms resistant to commonly used antimicrobials, should be identified and treated with antimicrobials with a low potential for failure. An aggressive management approach in complicated exacerbations may reduce costs by reducing healthcare utilization and hospitalization.

Beta-lactam antibiotics: newer formulations and newer agents

beta-Lactam antibiotics share a common structure and mechanism of action, although they differ in their spectrum of antimicrobial activity and utility in treating different infections. The current classes include the penicillins, the penicillinase-resistant penicillins, the extended- spectrum penicillins, the cephalosporins, the carbapenems, and the monobactams. This article discusses some of the newest beta-lactams available for use in the United States: ertapenem, cefditoren, and cefepime. A new formulation of amoxicillin-clavulanate, which contains higher doses of amoxicillin, is also discussed.

Update on Resistance among Respiratory Tract Pathogens: Results of the Antimicrobial Resistance Management Program

Purpose

This update from the Antimicrobial Resistance Management (ARM) Program reports surveillance data for Streptrococcus pneumoniae and Haemophilus influenzae isolates from 1994 to 2002.

Methods

Antibiograms and sensitivity reports submitted to the ARM program database were reviewed for resistance to commonly prescribed antibiotics

Results

Nationally S. pneumoniae resistance to penicillin was 37.4% (n = 37,688); to erythromycin, 29.6% (n = 18,774); and to clindamycin, 9.9% (n = 5510). Resistance to cefotaxime was 25.5% (n = 10,527) and 16.8% to ceftriaxone (26,594). For H. influenzae, resistance to cefotaxime was 4.3% (n = 4,927) and to ceftriaxone 1% (n = 10,353), a difference seen largely in the Northeast.

Conclusions

Resistance to penicillin appears to have reached a plateau above 40%; however, sparing of beta-lactam antibiotics may occur at the expense of other agents (ie, macrolides). Clindamycin remains active against penicillin-resistant S. pneumoniae (PRSP), but use of agents with antianaerobic properties is discouraged. The ARM program suggests important differences between cefotaxime and ceftriaxone.

Increased Antibiotic Resistance in Respiratory Tract Pathogens: PROTEKT US—An Update

Three major North American surveillance programs have tracked antimicrobial resistance patterns among isolates of Streptococcus pneumoniae and other common respiratory tract pathogens. The Canadian Bacterial Surveillance Network shows the progressive increase in resistance among pneumococcal S. pneumoniae to penicillin, trimethoprim-sulfamethoxazole, macrolides, and fluoroquinolones. The data from the Tracking Resistance in the United States Today study also show a steady rise in pneumococcal resistance among common antibiotics as well as an increase in multidrug-resistant S. pneumoniae. The US component of the Prospective Resistant Organism Tracking and Epidemiology for the Ketolide Telithromycin study has detected increasing resistance to many antimicrobial agents among common respiratory isolates, with marked geographic variations in resistance patterns. The patterns of resistance detected by these major surveillance programs are a warning signal regarding the continued emergence of resistance among community-acquired respiratory tract pathogens.

Susceptibility of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis to 17 oral antimicrobial agents based on pharmacodynamic parameters: 1998-2001 U S Surveillance Study

Pharmacokinetic/pharmacodynamic parameters were used to interpret susceptibility data for the oral agents tested in a clinically meaningful way. Among S pneumoniae isolates, >99% were susceptible to respiratory fluoroquinolones, 91.6% to amoxicillin, 92.1% to amoxicillin/clavulanic acid (95.2% at the extended-release formulation breakpoint), 90.6% to clindamycin, 80.4% to doxycycline, 71.0% to azithromycin, 72.3% to clarithromycin, 71.8% to cefprozil and cefdinir, 72.6% to cefuroxime axetil, 66.3% to cexime, 63.7% to trimethoprim/sulfamethoxazole, and 19.7% to cefaclor. Among H influenzae isolates, 28.6% were b-lactamase positive, but virtually all were susceptible to amoxicillin/clavulanic acid (98.3%, with 99.8% at the extended-release formulation breakpoint), cexime (100%), and uoroquinolones (99.8%), whereas 93.5% were susceptible to cefdinir, 82.8% to cefuroxime axetil, 78.1% to trimethoprim/sulfamethoxazole, 70.2% to amoxicillin, 25.1% to doxycycline, 23.2% to cefprozil, and 5% to cefaclor, azithromycin and clarithromycin. Most isolates of M catarrhalis were resistant to amoxicillin, cefaclor, cefprozil, and trimethoprim/sulfamethoxazole. Thus significant b-lactam and macrolide/azalide resistance in Streptococcus pneumoniae and b-lactamase production and trimethoprim/sulfamethoxazole resistance in untypeable Haemophilus influenzae are still present. The results of this study should therefore be applied to clinical practice based on the clinical presentation of the patient, the probability of the patient's having a bacterial rather than a viral infection, the natural history of the disease, the potential of pathogens to be susceptible to various oral antimicrobial agents, the potential for cross-resistance between agents with S pneumoniae, and the potential for pathogens to develop further resistance. Antibiotics should be used judiciously to maintain remaining activity and chosen carefully based on activity determined by pharmacokinetic/pharmacodynamic-based breakpoints to avoid these bacteria developing further resistance, particularly to fluoroquinolones.

The role of resistance and impact on appropriate antimicrobial use

Antibiotic resistance is a subject of growing concern throughout the medical community. Addressing drug resistance requires that practitioners understand the mechanisms of resistance and the methods of treating infections effectively while minimizing the emergence of resistant organisms. When making antibiotic selections, clinicians should consider a number of factors in addition to the drug's antimicrobial activity. These include the epidemiology of regional resistance and the antibiotic's pharmacokinetic and pharmacodynamic profile. Combination therapies should be considered and appropriate durations of therapy addressed. Developing clear practice guidelines for managing infectious disease can help practitioners reduce inappropriate antibiotic use and minimize the emergence of resistance.

Clinical and bacteriological efficacy of the ketolide telithromycin against isolates of key respiratory pathogens: a pooled analysis of phase III studies

A pooled analysis of data from 13 phase III studies of telithromycin in the treatment of community-acquired pneumonia, acute exacerbations of chronic bronchitis, acute sinusitis or group A beta-haemolytic streptococcal pharyngitis and tonsillitis was undertaken. Causative key respiratory tract pathogens (Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, Staphylococcus aureus and Streptococcus pyogenes) were isolated at entry to the studies from cultures of relevant respiratory samples and tested for their susceptibility to telithromycin, penicillin and macrolides (erythromycin A). The combined clinical and bacteriological efficacy of telithromycin at the post-therapy, test-of-cure visit (days 17-24) was assessed in patients from whom a microbiologically evaluable pathogen was isolated at entry. More than 98% of key respiratory pathogens isolated, including penicillin G- and macrolide (erythromycin A)-resistant strains of S. pneumoniae, demonstrated full or intermediate susceptibility to telithromycin in vitro at the breakpoints of < or = 1.0 mg/L (susceptible) and 2.0 mg/L (intermediate) used for the purpose of evaluating the susceptibility of isolates recovered during the clinical trials. Treatment with telithromycin 800 mg once-daily for 5, 7 or 7-10 days resulted in high rates of clinical cure (88.5%) and a satisfactory bacteriological outcome (88.9%), similar to the figures seen with comparator antibacterial agents. Clinical cure and eradication rates were good for all key respiratory pathogens, including penicillin G- and macrolide (erythromycin A)-resistant S. pneumoniae. The results suggest that telithromycin will provide effective empirical therapy for community-acquired upper and lower respiratory tract infections.

Open label, multicenter study of gatifloxacin treatment of recurrent otitis media and acute otitis media treatment failure

BACKGROUND

Recurrent otitis media and treatment failures of acute infections are refractory to therapy. Newer fluoroquinolones have excellent activity against respiratory pathogens, but their use in children has been limited because of concerns about adverse effects.

METHODS

This was an open label, multicenter trial in which patients with recurrent otitis media or acute otitis media (AOM) treatment failure were treated with 10 mg/kg gatifloxacin oral suspension once daily for 10 days. Before treatment a tympanocentesis or a swab of middle ear fluid was obtained. Nasopharyngeal swabs were obtained at baseline and at the end of therapy. Efficacy was evaluated 3 to 10 days after cessation of treatment and at 3 to 4 weeks. Safety monitoring included special attention to any sign or symptom suggestive of joint or bone abnormality.

RESULTS

The study enrolled 254 patients 6 months to 7 years of age, with one-half (52%) of the patients having recurrent otitis media, 17% having AOM treatment failure and 28% having both. Cure was achieved posttreatment in 88% of 198 clinically evaluable patients, with similar outcomes for patients younger or older than 2 years of age. Of the 45 evaluable patients with Streptococcus pneumoniae, 38 (84%) were cured, including 25 of 28 with penicillin-nonsusceptible strains. Also cured were 89% of those with Haemophilus influenzae and those with Moraxella catarrhalis. No selection of resistance to gatifloxacin was detected among nasopharyngeal pathogens. Eighty-three percent of the children had sustained cure at the 4 weeks follow-up visit. Adverse events were primarily mild gastrointestinal, with no occurrences of arthropathy.

CONCLUSION

Gatifloxacin is safe and effective for treatment of recurrent otitis media and AOM treatment failure in children.

Antimicrobial Resistance among Isolates of Respiratory Tract Infection Pathogens from the Southern United States: Data from the PROTEKT US Surveillance Program 2000/2001

BACKGROUND

PROTEKT US (Prospective Resistant Organism Tracking and Epidemiology for the Ketolide Telithromycin in the United States) was established in 2000 to monitor antimicrobial resistance among respiratory tract pathogens across the United States.

METHODS

During 2000 to 2001, 75 southern US centers collected 3,867 Streptococcus pneumoniae, 1,455 Streptococccus pyogenes and 1,042 Haemophilus influenzae.

RESULTS

Overall, 46.1% of S. pneumoniae isolates were nonsusceptible to penicillin, 35.8% were resistant to erythromycin, and 0.5% were resistant to fluoroquinolones. Against S. pneumoniae the most active agents were telithromycin (99.7% susceptible), linezolid (99.8%) and the fluoroquinolones (levofloxacin 99.4%, gatifloxacin 99.5%). The prevalence of erythromycin-resistant S. pyogenes isolates was 4.5%. Telithromycin, at concentration of < or = 1 mg/L, inhibited 99.9% of S. pyogenes. The prevalence of beta-lactamase positive H. influenzae was 26.2%. Telithromycin was active (MIC90 4 mg/L) against H. influenzae, irrespective of beta-lactamase production.

CONCLUSION

The prevalence of penicillin and macrolide resistance among respiratory tract pathogens from the southern United States is high. Fluoroquinolone resistance is low. Telithromycin is highly active against respiratory tract pathogens with reduced susceptibility to beta-lactams, macrolides, and fluoroquinolones.

Sequential IV/PO moxifloxacin treatment of patients with severe community-acquired pneumonia

BACKGROUND

IV/PO moxifloxacin was evaluated in the treatment of hospitalized patients with severe community-acquired pneumonia (CAP).

METHODS

Data were pooled from two prospective, randomized studies. In the multinational study, patients received 7-14 days IV/PO moxifloxacin 400 mg QD or IV/ PO amoxicillin clavulanate 1200/625 mg TID +/- IV/PO clarithromycin 500 mg BID. In the North American study, patients received 7-14 days IV/PO moxifloxacin 400 mg QD, IV/ PO alatrofloxacin/trovafloxacin 200 mg QD, or IV/PO levofloxacin 500 mg QD. The primary endpoint was clinical success at the test-to-cure visit. Severe CAP was defined according to the 1993 ATS criteria.

RESULTS

In the clinically valid population, clinical success rates were 88% (167/190) for moxifloxacin- and 83% (155/186) for comparator-treated patients (95% CI = -1.9%, 12.2%). Corresponding clinical success rates for the microbiologically valid population were 87% (59/68) and 84% (54/64), respectively (95% CI = 8.6%, 15.0%). A switch from IV to PO therapy was made by day 5 of therapy for 73% of moxifloxacin- vs. 60% of comparator-treated patients (P < 0.01). Clinical success rates were similar in a retrospective analysis using the revised 2001 ATS definition of severe CAP. Mortality rates were 6% (15/241) and 10% (24/238) in the moxifloxacin and comparator treatment groups, respectively. The incidence of drug-related adverse events was similar in both treatment groups.

CONCLUSION

Sequential IV/PO moxifloxacin 400 mg QD is as safe and effective as other fluoroquinolones and a beta-lactam/macrolide combination for treating hospitalized patients with severe CAP.

Fluoroquinolone AUIC break points and the link to bacterial killing rates. Part 1: In vitro and animal models

OBJECTIVE

To review in vitro and animal model studies with fluoroquinolones and the pharmacokinetic and pharmacodynamic relationships that are predictive of clinical and microbiologic outcomes and resistance. Data on fluoroquinolones are summarized and examine the premise that a single area under the inhibitory concentration-time curve (AUIC) target >125 may be used for all fluoroquinolones with concentration-dependent killing actions and against all target organisms.

DATA SOURCES

Primary articles were identified by MEDLINE search (1966-February 2002) and through secondary sources.

STUDY SELECTION AND DATA EXTRACTION

All of the articles identified from the data sources were evaluated, and all information deemed relevant was included.

DATA SYNTHESIS

The fluoroquinolones exhibit concentration-dependent killing. This effect clearly depends on concentrations achieved, and outcomes depend on endpoints established by individual investigators. With AUIC values <60, the actions of fluoroquinolones are essentially bacteriostatic; any observed bacterial killing is the combined effect of low concentrations in relation to minimum inhibitory concentration and the action of host factors such as neutrophils and macrophages. AUIC values >100 but <250 yield bacterial killing at a slow rate, but usually by day 7 of treatment. AUICs >250 produce rapid killing, and bacterial eradication occurs within 24 hours. Disagreements regarding target endpoints are the expected consequences of comparing microbial and clinical outcomes across animal models, in vitro experiments, and humans when the endpoints are clearly not equivalent. Careful attention to time-related events, such as speed of bacterial killing, versus global endpoints, such as bacteriologic cure, allows optimal break points to be defined.

CONCLUSIONS

Evidence from in vitro and animal models favors the use of AUIC values >250 for rapid bactericidal action, regardless of whether the organism is gram-negative or gram-positive.

Efficacy and Tolerability of Telithromycin for 5 or 10 Days vs Amoxicillin/Clavulanic Acid for 10 days in Acute Maxillary Sinusitis

Telithromycin (HMR 3647) is a new ketolide antimicrobial that was developed for the treatment of community-acquired respiratory tract infections. We conducted a randomized, double-blind, multicenter study to compare the clinical efficacy and safety of oral telithromycin, at 800 mg once daily for 5 or 10 days, with that of amoxicillin/clavulanic acid, at 500/125 mg three times daily for 10 days, in adults with acute maxillary sinusitis (AMS). A total of 754 patients with AMS of less than 28 days’ duration were randomized to receive either telithromycin for 5 days followed by placebo for 5 days, telithromycin for 10 days, or amoxicillin/clavulanic acid for 10 days. Clinical outcome was assessed at a test-of-cure (TOC) visit between days 17 and 24 and at a late post-therapy visit between days 31 and 45. Analysis of clinical outcome on a per-protocol basis (n = 434) demonstrated therapeutic equivalence among the three regimens at the TOC visit; in each treatment group, the clinical cure rate was approximately 75%. Only a few patients (3 to 5 in each group) had relapsed by the late post-therapy follow-up visit. Telithromycin was generally safe and well tolerated. The most common adverse events were mild or moderate gastrointestinal effects, which occurred with similar frequency in all three groups. We conclude that 5 or 10 days of telithromycin at 800 mg once daily is as effective clinically and as well tolerated as 10 days of treatment with amoxicillin/clavulanic acid. Telithromycin, therefore, appears to be a valuable option for the treatment of AMS.

Haemophilus influenzae bla(ROB-1) mutations in hypermutagenic deltaampC Escherichia coli conferring resistance to cefotaxime and beta-lactamase inhibitors and increased susceptibility to cefaclor

The clinical use of cefaclor has been shown to enrich Haemophilus influenzae populations harboring cefaclor-hydrolyzing ROB-1 beta-lactamase. Such a selective process may lead to the increased use of extended-spectrum cephalosporins or beta-lactams plus beta-lactamase inhibitors and, eventually, resistance to these agents, which has not previously been observed in H. influenzae. In order to establish which bla(ROB-1) mutations, if any, could confer resistance to extended-spectrum cephalosporins and/or to beta-lactamase inhibitors, a plasmid harboring bla(ROB-1) was transformed into hypermutagenic strain Escherichia coli GB20 (DeltaampC mutS::Tn10), and this construct was used in place of H. influenzae bla(ROB-1). Strain GB20 with the cloned gene was submitted to serial passages in tubes containing broth with increasing concentrations of selected beta-lactams (cefotaxime or amoxicillin-clavulanate). Different mutations in the bla(ROB-1) gene were obtained during the passages in the presence of the different concentrations of the selective agents. Mutants resistant to extended-spectrum cephalosporins harbored either the Leu169-->Ser169 or the Arg164-->Trp164 substitution or the double amino acid change Arg164-->Trp164 and Ala237-->Thr237. ROB-1 mutants that were resistant to beta-lactams plus beta-lactamase inhibitors and that harbored the Arg244-->Cys244 or the Ser130-->Gly130 replacement were also obtained. The cefaclor-hydrolyzing efficiencies of the ROB-1 variants were strongly decreased in all mutants, suggesting that if bla(ROB-1) mutants were selected by cefaclor, this drug would prevent the further evolution of this beta-lactamase toward molecular forms able to resist extended-spectrum cephalosporins or beta-lactamase inhibitors.

Worldwide trends in antimicrobial resistance among common respiratory tract pathogens in children

BACKGROUND

Respiratory tract infections among children are a common reason for health care provider visits and the primary reason for antimicrobial prescribing in this population. The increased prevalence of resistance among Streptococcus pneumoniae and Haemophilus influenzae pathogens poses a serious challenge in the successful treatment of respiratory tract infections caused by these pathogens.

METHODS

This paper reviews worldwide trends in antimicrobial resistance among common respiratory tract pathogens, highlighting data obtained from the pediatric population where available.

RESULTS

S. pneumoniae resistance to beta-lactams is mediated through alterations in the penicillin-binding proteins and macrolide resistance to acquisition of efflux or methylation genes. The mechanisms of resistance to the fluoroquinolones include target enzyme alterations via genetic mutations and transport out of the bacterial cell via an efflux pump. Beta-lactamase production is the primary mechanism of resistance to penicillins among H. influenzae isolates. Although S. pneumoniae with reduced susceptibility to penicillin was first documented > 30 years ago, resistance has increased at an alarming rate worldwide in the past decade. According to recent surveillance data, the worldwide prevalence of S. pneumoniae with reduced susceptibility to penicillin is 18.2%. Beta-lactamase production among H. influenzae ranges from approximately 4% in Russia to 26% in the United States and to 31% in France. The prevalence of beta-lactamase-negative, ampicillin-resistant H. influenzae remains very low (< 1%) worldwide, except in Japan, where the incidence is higher. In general, the highest rates of resistance are observed in isolates obtained from children, and risk factors for infection with a resistant pathogen include young age, the site of infection, day-care center attendance and recent antimicrobial use.

CONCLUSIONS

Increased prevalence of antimicrobial resistance among respiratory tract pathogens isolated from children and adults is evident worldwide. Treatment of infections caused by S. pneumoniae and H. influenzae with older agents or ineffective dosing regimens may not eradicate infections and may contribute to the spread of resistance. These observations confirm the need for appropriate antimicrobial use to halt or at least limit the spread of resistance.

Telithromycin 800 mg once daily for seven to ten days is an effective and well-tolerated treatment for community-acquired pneumonia

OBJECTIVE

This open, multinational study examined the efficacy and tolerability of telithromycin (HMR 3647), the first ketolide antibacterial agent, at an oral dose of 800 mg once daily for seven to ten days (further validated using pharmacokinetic analysis) as an empiric therapy in adults with mild to moderate community-acquired pneumonia (CAP).

METHODS

A total of 240 patients (aged 18-79 years; median 40 years) with clinical signs and symptoms of CAP (radiologically confirmed) were enrolled in the study and received at least one dose of study medication. Sputum and blood samples for bacteriologic documentation were collected within 48 h prior to enrollment. Clinical and bacteriological outcomes were assessed 17-21 days (test of cure visit) and 31-36 days (late post-therapy visit) after treatment initiation. Adverse events were assessed by spontaneous reporting and investigator observation.

RESULTS

At the test of cure visit, 92.9% (95% CI: 88.4-96.1; n= 197) of patients achieved clinical cure in the per-protocol (PP) population. In the modified intent-to-treat (mITT) population, the cure rate was 79.6% (95% CI: 73.9-84.5; n= 240), including 12.5% of undetermined cases categorized as failures. Clinical cure (PP population) remained high in patients >/=65 years (85.7%), and in patients with a Fine score >/=III (92.1%). Among those patients for whom bacteriologic data were available, the majority had a satisfactory outcome (88.9% in the bacteriologic PP; n= 45). Bacterial eradication rates were similarly high (85.5% and 82.7% for the mITT and PP populations, respectively). All patients with infections as a result of atypical/intracellular pathogens Chlamydophila (Chlamydia) pneumoniae, Mycoplasma pneumoniae or Legionella pneumophila had a clinical outcome of cure. Treatment was well tolerated. Adverse events were mainly gastrointestinal in origin and mild in intensity.

CONCLUSION

An oral dose of telithromycin 800 mg once daily for seven to ten days is an effective and well-tolerated first-line treatment for mild to moderate CAP in adults.

Telithromycin in the treatment of community-acquired pneumonia: a pooled analysis

The efficacy of telithromycin has been assessed in six Phase III studies involving adults with mild to moderate community-acquired pneumonia (CAP) with a degree of severity compatible with oral therapy. Patients received telithromycin 800 mg once daily for 7-10 days in three open-label studies (n=870) and three randomized, double-blind, comparator-controlled studies (n=503). Comparator antibacterials were amoxicillin 1000 mg three-times daily, clarithromycin 500 mg twice daily and trovafloxacin 200 mg once daily. Clinical and bacteriological outcomes were assessed 7-14 days post-therapy. Among telithromycin-treated patients, per-protocol clinical cure rates were 93.1 and 91.0% for the open-label and comparative studies, respectively. Telithromycin treatment was as effective as the comparator agents. High eradication and clinical cure rates were observed for infections caused by key pathogens: Streptococcus pneumoniae including isolates resistant to penicillin G and/or erythromycin A (95.4%), Haemophilus influenzae (89.5%) and Moraxella catarrhalis (90%). Telithromycin was also highly effective in patients with infections caused by atypical and/or intracellular pathogens and those at increased risk of morbidity. Telithromycin was generally well tolerated. Telithromycin 800 mg once daily for 7-10 days offers a convenient and well-tolerated first-line oral therapy for the empirical treatment of mild to moderate CAP.

In vitro activities of telithromycin and 10 oral agents against aerobic and anaerobic pathogens isolated from antral puncture specimens from patients with sinusitis

A study of the comparative in vitro activity of telithromycin, a new ketolide, against 155 aerobic and 171 anaerobic antral sinus puncture isolates showed it to be active against a broad range of sinus pathogens. All pneumococci, including erythromycin-resistant strains, were susceptible to telithromycin at < or = 0.5 microg/ml; all Haemophilus influenzae and Eikenella corrodens strains were inhibited by < or = 4 microg of telithromycin/ml; all Moraxella spp. and beta-lactamase-producing Prevotella species strains were inhibited by < or = 0.25 and 0.5 microg of telithromycin/ml, respectively. Among all anaerobes tested, 94% (160 of 171 strains) were susceptible to < or = 4 microg of telithromycin/ml; however, 8 of 17 (47%) Fusobacterium strains, 2 Veillonella strains, and 1 Peptostreptococcus micros strain required > 4 microg of telithromycin/ml for inhibition. Telithromycin may offer a therapeutic alternative for sinus infections, including those due to erythromycin-resistant pneumococci.

Prevalence and clinical significance of community-acquired penicillin-resistant pneumococcal pneumonia in Thailand

OBJECTIVE

The study aimed to evaluate the prevalence, clinical significance and outcome of community-acquired penicillin-resistant Streptococcus pneumoniae (PRSP) pneumonia in Thailand.

METHODOLOGY

We conducted a prospective study in culture-proven pneumococcal pneumonia. Pneumococci were defined as susceptible, intermediate resistance and high resistance according to the definitions of the United States National Committee for Clinical Laboratory Standards (NCCLS).

RESULTS

Forty-six consecutive patients were enrolled. Of the S. pneumoniae isolates collected, 41.3% were resistant to penicillin (37% intermediate resistance and 4.3% high resistance). Resistance to other antibiotics was 13% to ceftriaxone (8.7% intermediate resistance and 4.3% high resistance), 34.8% to erythromycin, 39.1% to tetracycline, 26.1% to chloramphenicol, and 43.5% to trimethoprim -sulfamethoxazole. Prior antibiotic use within 3 months was significantly associated with resistance to penicillin. The overall mortality of pneumococcal pneumonia was 26.1%. Multilobar involvement and requirement for mechanical ventilation proved to be associated with mortality. However, resistance to penicillin or ceftriaxone was not associated with death.

CONCLUSIONS

According to the US NCCLS guidelines, we found a high prevalence of drug-resistant S. pneumoniae in Thai patients with community-acquired pneumonia. Prior antibiotic use was significantly associated with penicillin resistance. However, the outcome was not related to in vitro penicillin susceptibility of S. pneumoniae isolated from the patients.

National surveillance programme on susceptibility patterns of respiratory pathogens in South Africa: moxifloxacin compared with eight other antimicrobial agents

AIMS

The susceptibility patterns of Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, Klebsiella pneumoniae, and Streptococcus pyogenes isolated from specimens submitted to 12 private laboratories in South Africa were determined.

METHODS

Minimum inhibitory concentration (MIC) determinations were performed on the isolates in the microbiology laboratory at Tygerberg Hospital according to the recommendations of the National Committee for Clinical Laboratory Standards (NCCLS).

RESULTS

According to the NCCLS breakpoints, 24% of 729 S pneumoniae isolates were sensitive, 30% intermediate, and 46% resistant to penicillin. Rates of macrolide resistance were high, with 61% of the pneumococci being resistant to clarithromycin and azithromycin. Co-trimoxazole resistance was also high, with 28% of pneumococcal strains being sensitive, 21% intermediate, and 51% resistant. beta Lactamase was produced by 7% of 736 H influenzae isolates and 91% of 256 M catarrhalis isolates. The quinolones, moxifloxacin and levofloxacin, were universally active against all isolates tested, which included S pneumoniae, H influenzae, M catarrhalis, K pneumoniae, and S pyogenes.

CONCLUSIONS

Haemophilus influenzae and S pneumoniae were the most commonly isolated organisms. Resistance to penicillin was one of the highest reported in the world (76%) in S pneumoniae, as was macrolide resistance in pneumonocci, although surprisingly, only 14% of S pyogenes were resistant. The quinolones, moxifloxacin and levofloxacin, were active against all organisms tested, including the penicillin and macrolide resistant strains and moxifloxacin was more active than levofloxacin against pneumococci.

Community-acquired pneumonia in the emergency department: a practical approach to diagnosis and management

Pneumonia is one of the most common conditions for which patients seek emergency care. It is a challenging infection in that the spectrum of illness ranges from the nontoxic patient appropriate for outpatient antibiotics to the critically ill patient requiring intensive care hospitalization. Current data and diagnostic technology provide the emergency physician with the tools for an appropriately rapid evaluation and consideration of the differential diagnosis. Key critical thinking and application of published findings allow for intelligent empirical antibiotic treatment and risk stratification for the best disposition. Although antibiotic-resistant organisms increasingly are being identified, patients continue to benefit from early institution of standard ED treatment. Coverage for atypical organisms improves patient response and outcome. Finally, identification and treatment of the complications of pneumonia and accompanying sepsis must be considered by the ED physician when evaluating critically ill patients.

Antimicrobial susceptibility of 840 clinical isolates of Haemophilus influenzae collected in four European countries in 2000-2001

In 2000-2001, 840 clinical isolates of Haemophilus influenzae were collected from laboratories in France, Germany, Italy and Spain (210 isolates/country). Beta-Lactamase production among the isolates varied considerably by country, ranging from 8.1% in Germany to 34.8% in France. H. influenzae from patients <or=4 years old showed the highest prevalence of beta-lactamase production (23.2%), compared with isolates from patients aged 5-17 years (17.8%) and >or=18 years (16.5%). All isolates were susceptible to amoxicillin-clavulanate, ciprofloxacin and levofloxacin; 99.6% and 98.9% of isolates were susceptible to azithromycin and cefuroxime, respectively. Among the macrolides tested, azithromycin (MIC90, 2 mg/L) was eight-fold more potent than clarithromycin (MIC90, 16 mg/L) and roxithromycin (MIC90, 16 mg/L). Despite variations in beta-lactamase production between different countries, > 99% of all isolates were susceptible to amoxicillin-clavulanate, ciprofloxacin, levofloxacin, and azithromycin.

Antimicrobial susceptibility of community-acquired respiratory tract pathogens in North America in 1999-2000: findings of the PROTEKT surveillance study

The PROTEKT surveillance study commenced in 1999 to examine the antimicrobial susceptibility of community-acquired respiratory pathogens. We report here the results from 2371 isolates collected during 2000 by North American centers (Canada, n = 7; USA, n = 8). Overall, 21.3% of pneumococci (n = 687) were penicillin G-resistant (Canada, 10.3%; USA, 32.6%). Corresponding rates of erythromycin resistance were 16.3% and 31.5%. Telithromycin inhibited all penicillin- and erythromycin-resistant isolates at < or =1 microg/ml. Among 612 Hemophilus influenzae isolates, 22.4% were beta-lactamase-positive. Antimicrobial susceptibility of H. influenzae varied between 82.4% (clarithromycin) and 100% (cefpodoxime, levofloxacin). Importantly, one isolate was found to be resistant to both moxifloxacin and ciprofloxacin. Most Moraxella catarrhalis isolates were highly susceptible to the antimicrobials tested, except ampicillin. All Streptococcus pyogenes isolates (n = 382) were penicillin-susceptible and 5.2% were non-susceptible to erythromycin. S. pyogenes showed cross-resistance to other macrolides yet remained inhibited by telithromycin at < or =0.5 microg/ml. Methicillin resistance among Staphylococcus aureus was common (19.9%), particularly in the USA. The PROTEKT study confirms the widespread prevalence of antimicrobial resistance among common respiratory pathogens in North America, and hence the need for continued surveillance to guide optimal empiric therapy for community-acquired respiratory tract infections.

Health care resource utilization associated with treatment of penicillin-susceptible and -nonsusceptible isolates of Streptococcus pneumoniae

Despite failure to correlate in vitro susceptibility with clinical outcomes for respiratory tract infections and bacteremia, resistance affects management of patients with pneumococcal infections. The economic impact of resistance among pneumococci has not been evaluated. We conducted a single-center, retrospective, observational, cohort study of hospitalized patients infected with Streptococcus pneumoniae isolated from blood or a respiratory source between January 1, 1995, and December 31, 1998. Data were collected for 36 days surrounding the day that the first positive culture was collected. Patients were grouped according to isolate penicillin-susceptibility profile [susceptible minimum inhibitory concentration (MIC) < or = 0.06 microg/ml, nonsusceptible MIC > or = 0.125 microg/ml), and data were analyzed with respect to health care resource utilization patterns. Of 231 patients identified, 142 and 89 had susceptible and nonsusceptible isolates, respectively. Groups were similar with respect to demographics and comorbidities, except that patients infected with a nonsusceptible isolate were more likely to have the isolate obtained from a respiratory source and to have a history of recent antibiotic therapy. No difference was noted with respect to clinical outcome; however, patients infected with a nonsusceptible isolate had a longer median stay (14 vs 10 days, p<0.05). They also had significantly higher total median costs (1600 dollars, 95% confidence interval 257-2943 dollars) due to room and nursing services. Infections caused by penicillin-nonsusceptible pneumococci were not associated with a worse outcome in hospitalized patients but were associated with increased cost of care.

Using hospital antibiogram data to assess regional pneumococcal resistance to antibiotics

Antimicrobial resistance to penicillin and macrolides in Streptococcus pneumoniae has increased in the United States over the past decade. Considerable geographic variation in susceptibility necessitates regional resistance tracking. Traditional active surveillance is labor intensive and costly. We collected antibiogram reports from North Carolina hospitals and assessed pneumococcal susceptibility to multiple agents from 1996 through 2000. Susceptibility in North Carolina was consistently lower than the national average. Aggregating antibiogram data is a feasible and timely method of monitoring regional susceptibility patterns and may also prove beneficial in measuring the effects of interventions to decrease antimicrobial resistance.

Influence of macrolide susceptibility on efficacies of clarithromycin and azithromycin against Streptococcus pneumoniae in a murine lung infection model

We evaluated the activities of clarithromycin and azithromycin against 19 isolates of Streptococcus pneumoniae using a neutropenic lung infection model. The isolates included five susceptible isolates (clarithromycin and azithromycin MICs, </=0.12 micro g/ml), nine isolates exhibiting low-level, mefA-mediated resistance (clarithromycin and azithromycin MICs, 0.5 to 32 micro g/ml), and five isolates expressing high-level, ermB-mediated macrolide resistance (clarithromycin and azithromycin MICs, >/=64 micro g/ml). Infected mice were administered either saline (control), clarithromycin (4, 40, or 200 mg/kg of body weight twice daily or 200 mg/kg once daily), or azithromycin (4, 40, or 200 mg/kg once daily or 40 mg/kg twice daily) by oral gavage for 72 h. Mortality was assessed at regular intervals for 10 days, and survival in each group was compared to that of untreated controls. Animals infected with susceptible isolates demonstrated significant improvement in survival compared to the controls following treatment with either agent at doses of >/=40 mg/kg. In contrast, none of the regimens improved the survival of animals infected with isolates exhibiting high-level macrolide resistance. Among mice infected with strains expressing low-level resistance, significant improvement in survival compared to the controls was noted among isolates treated with clarithromycin at 40 (seven of nine isolates) and 200 (nine of nine isolates) mg/kg twice a day and with azithromycin at 40 (one of nine isolates) and 200 (three of nine isolates) mg/kg once a day. Animals infected with isolates of S. pneumoniae exhibiting low-level, mefA-mediated macrolide resistance responded to treatment with clarithromycin at rates similar to those observed among mice infected with fully susceptible isolates.

Surveillance of resistance in bacteria causing community-acquired respiratory tract infections

Bacterial resistance to antibiotics in community-acquired respiratory tract infections is a serious problem and is increasing in prevalence world-wide at an alarming rate. Streptococcus pneumoniae, one of the main organisms implicated in respiratory tract infections, has developed multiple resistance mechanisms to combat the effects of most commonly used classes of antibiotics, particularly the beta-lactams (penicillin, aminopenicillins and cephalosporins) and macrolides. Furthermore, multidrug-resistant strains of S. pneumoniae have spread to all regions of the world, often via resistant genetic clones. A similar spread of resistance has been reported for other major respiratory tract pathogens, including Haemophilus influenzae, Moraxella catarrhalis and Streptococcus pyogenes. To develop and support resistance control strategies it is imperative to obtain accurate data on the prevalence, geographic distribution and antibiotic susceptibility of respiratory tract pathogens and how this relates to antibiotic prescribing patterns. In recent years, significant progress has been made in developing longitudinal national and international surveillance programs to monitor antibiotic resistance, such that the prevalence of resistance and underlying trends over time are now well documented for most parts of Europe, and many parts of Asia and the Americas. However, resistance surveillance data from parts of the developing world (regions of Central America, Africa, Asia and Central/Eastern Europe) remain poor. The quantity and quality of surveillance data is very heterogeneous; thus there is a clear need to standardize or validate the data collection, analysis and interpretative criteria used across studies. If disseminated effectively these data can be used to guide empiric antibiotic therapy, and to support-and monitor the impact of-interventions on antibiotic resistance.

Telithromycin is as effective as amoxicillin/clavulanate in acute exacerbations of chronic bronchitis

This randomized, double-blind study evaluated the efficacy and safety of a short, 5-day course of telithromycin, a new ketolide antibacterial, compared with a standard 10-day course of amoxicillin/clavulanate, in the treatment of acute exacerbations of chronic bronchitis (AECB). The study enrolled 325 adult patients with AECB and a history of chronic obstructive pulmonary disease (COPD). Patients received either telithromycin 800 mg once daily (qd) for 5 days (followed by placebo for 5 days) or amoxicillin/clavulanate 500/125 mg three times daily (tid) for 10 days. Clinical cure rates for telithromycin post-therapy (Days 17-21, test-of-cure) and late post-therapy (Days 31-36) were 86.1 and 78.1%, respectively; 82.1 and 75.0% for amoxicillin/clavulanate. Excellent clinical cure rates were also observed for high-risk patients. Bacteriologic outcome was satisfactory for 69.2% of telithromycin recipients vs 70.0% for amoxicillin/clavulanate recipients. Both treatments were generally well tolerated, although the frequency of drug-related adverse events was almost two-fold higher for amoxicillin/clavulanate (25.0 vs. 13.1%). Thus, a 5-day course of telithromycin 800 mg qd is an effective and well-tolerated alternative to a standard 10-day course of amoxicillin/clavulanate 500/125 mg tid for first-line empiric treatment of AECB in adults with COPD.