Regional trends in antimicrobial resistance among clinical isolates of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis in the United States: results from the TRUST Surveillance Program, 1999-2000

Activities of ceftobiprole, a novel broad-spectrum cephalosporin, against Haemophilus influenzae and Moraxella catarrhalis

Ceftobiprole, a broad-spectrum pyrrolidinone-3-ylidenemethyl cephem currently in phase III clinical trials, had MICs between 0.008 microg/ml and 8.0 microg/ml for 321 clinical isolates of Haemophilus influenzae and between < or =0.004 microg/ml and 1.0 microg/ml for 49 clinical isolates of Moraxella catarrhalis. Ceftobiprole MIC(50) and MIC(90) values for H. influenzae were 0.06 microg/ml and 0.25 microg/ml for beta-lactamase-positive strains (n = 262), 0.03 microg/ml and 0.25 microg/ml for beta-lactamase-negative strains (n = 40), and 0.5 microg/ml and 2.0 microg/ml for beta-lactamase-negative ampicillin-resistant strains (n = 19), respectively. Ceftobiprole MIC(50) and MIC(90) values for beta-lactamase-positive M. catarrhalis strains (n = 40) were 0.12 microg/ml and 0.5 microg/ml, respectively, whereas the ceftobiprole MIC range for beta-lactamase-negative M. catarrhalis strains (n = 9) was < or =0.004 to 0.03 microg/ml. Ceftriaxone MICs usually were generally at least twofold lower than those of ceftobiprole, whereas amoxicillin-clavulanate MICs usually were higher than those of ceftobiprole. Azithromycin and telithromycin had unimodal MIC distributions against H. influenzae, with MIC(90) values of azithromycin and telithromycin of 2 microg/ml and 4 microg/ml, respectively. Except for selected quinolone-nonsusceptible H. influenzae strains, moxifloxacin proved highly active, with MIC(90) values of 0.12 microg/ml. Time-kill analyses showed that ceftobiprole, ceftriaxone, cefpodoxime, amoxicillin-clavulanate, azithromycin, telithromycin, and moxifloxacin were bactericidal at 2x MIC by 24 h against all 10 H. influenzae strains surveyed. Only modest increases in MICs were found for H. influenzae or M. catarrhalis clones after 50 serial passages in the presence of subinhibitory concentrations of ceftobiprole, and single-passage selection showed that the selection frequency of H. influenzae or M. catarrhalis clones with elevated ceftobiprole MICs is quite low.

A comparison of 5 days of therapy with cefdinir or azithromycin in children with acute otitis media: a multicenter, prospective, single-blind study

BACKGROUND

Short-course therapy for acute otitis media (AOM) improves adherence and may reduce secondary bacterial resistance.

METHODS

In this multicenter, prospective, investigator-blinded study, patients between the ages of 6 months and 6 years with a clinical diagnosis of AOM were randomized to receive cefdinir oral suspension 7 mg/kg q12h for 5 days or azithromycin oral suspension 10 mg/kg once daily on day 1 and 5 mg/kg once daily on days 2 through 5. Clinical response was assessed at the end-of-therapy (EOT) visit (days 7-9) and the follow-up visit (days 20-25).

RESULTS

Three hundred fifty-seven patients were enrolled in the study. The treatment groups were similar at baseline with respect to demographic characteristics (mean [SD] age, 3.0 [1.7] years; 55% male), incidence of bilateral AOM (45%), and presenting signs and symptoms. The majority of evaluable children (77%) had previously received conjugated heptavalent pneumococcal vaccine (PCV7) against Streptococcus pneumoniae. At the EOT visit, clinical cure rates were comparable for cefdinir and azithromycin (87% [151/174] and 85% [149/176], respectively; 95% CI, -5.5 to 9.8). In addition, clinical cure rates at the EOT visit in the children who had been vaccinated with PCV7 were comparable between cefdinir and azithromycin (86% vs 83%; 95% CI, -6.5 to 11.8). No significant difference in clinical cure rates was observed at the follow-up visit (76% and 86%; 95% CI, -18.9 to 0.0). Parental satisfaction was similar between treatment groups with regard to ease of use, taste, compliance, health care resource utilization, and missed days of work and day-care. Both antibiotics were well tolerated; diarrhea and abnormal stools were the most common antibiotic-related adverse events (< or = 7% each).

CONCLUSIONS

Short courses (5 days) of therapy with cefdinir or azithromycin were comparable in these children with AOM based on clinical end points, parental preferences, and health care utilization.

Severe sepsis and septic shock: review of the literature and emergency department management guidelines

Severe sepsis and septic shock are as common and lethal as other acute life-threatening conditions that emergency physicians routinely confront such as acute myocardial infarction, stroke, and trauma. Recent studies have led to a better understanding of the pathogenic mechanisms and the development of new or newly applied therapies. These therapies place early and aggressive management of severe sepsis and septic shock as integral to improving outcome. This independent review of the literature examines the recent pathogenic, diagnostic, and therapeutic advances in severe sepsis and septic shock for adults, with particular relevance to emergency practice. Recommendations are provided for therapies that have been shown to improve outcomes, including early goal-directed therapy, early and appropriate antimicrobials, source control, recombinant human activated protein C, corticosteroids, and low tidal volume mechanical ventilation.

Should patients with acute exacerbation of chronic bronchitis be treated with antibiotics? Advantages of the use of fluoroquinolones

The pathological changes in chronic bronchitis (CB) produce airflow obstruction, reduce the effectiveness of the mucocilliary drainage system and lead to bacterial colonisation of bronchial secretion. The presence of bacteria induces an inflammatory response mediated by leukocytes. There is a direct relationship between the degree of impairment of the mucocilliary drainage system, the density of bacteria in mucus and the number of leukocytes in the sputum. Purulent sputum is a good marker of a high bacterial load. Eventually, if the number of leukocytes is high, their normal activity could decrease the effectiveness of the drainage system, increase the bronchial obstruction and probably damage the lung parenchyma. Whenever the density of bacteria in the bronchial lumen is >or=10(6) CFU/mL, there is a high probability that the degree of inflammatory response will lead to a vicious cycle which in turn tends to sustain the process. This situation can arise during the clinical course of any acute exacerbation of CB, independently of its aetiology, provided the episode is sufficiently severe and/or prolonged. Fluoroquinolones of the third and fourth generation are bactericidal against most microorganisms usually related to acute exacerbations of CB. Their diffusion to bronchial mucus is adequate. When used in short (5-day) treatment they reduce the bacterial load in a higher proportion than is achieved by beta-lactam or macrolide antibiotics given orally. Although the clinical cure rate is similar to that obtained with other antibiotics, the time between exacerbations could be increased.

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.

Pharmacoeconomics of treatment with the newer anti-Gram-positive agents

The unmet medical need of emerging resistance among Gram-positive pathogens, such as methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci and penicillin-resistant Streptococcus pneumoniae, has driven industry towards the identification and development of novel anti-Gram-positive agents. Among the newer agents are improved quinolones, a lipopeptide, an oxazolidinone and novel glycopeptides. Scientific distinctions between these drugs, which impact on the placement, usage and, ultimately, the pharmacoeconomics of several of these new agents, may lead to further consideration despite poor initial observations of minimal improvement. Key differences in the characteristics of these drugs (i.e., spectrum, activity, resistance emergence, efficacy, target, safety) provide a basis for an emerging pharmacoeconomic-based distinction between these newer anti-Gram-positive agents.

Comparison of censored regression and standard regression analyses for modeling relationships between antimicrobial susceptibility and patient- and institution-specific variables

In order to identify patients likely to be infected with resistant bacterial pathogens, analytic methods such as standard regression (SR) may be applied to surveillance data to determine patient- and institution-specific factors predictive of an increased MIC. However, the censored nature of MIC data (e.g., MIC < or = 0.5 mg/liter or MIC > 8 mg/liter) imposes certain limitations on the use of SR. In order to investigate the nature of these limitations, simulations were performed to compare a regression tailored for censored data (censored regression [CR]) and one tailored for an SR. By using a model relating piperacillin-tazobactam MICs against Enterobacter spp. to patient age and hospital bed capacity, 200 simulations of 500 isolates were performed. Various MIC censoring patterns were imposed by using 26 left- or right-censored (L,R) pairs (i.e., MICs < or = 2 mg/liter(L) [2L] or MICs > 2 mg/liter(R) [2R], respectively). Data were fit by CR and SR for which censored MICs were either (i) excluded, (ii) replaced by 2L or 2R, or (iii) replaced by 2(L - 1) or 2(R + 1). Total censoring for the 26 pairs ranged from 7 to 86%. By CR, deviations of average parameter estimates from the true parameter values were <0.10 log2 (mg/liter) for all parameters for each of the 26 pairs. By SR, these deviations were >0.10 log2 (mg/liter) for at least 18 of the 26 pairs for all but one parameter. Two-standard-error confidence intervals for individual parameters contained as little as 0% of cases for all SR approaches but > or = 91.5% of cases for the CR approach. When censored MIC data are modeled, CR may reduce or eliminate biased parameter estimates obtained by SR.

Synthesis and antibacterial activity of 6-O-heteroarylcarbamoyl-11,12-lactoketolides

A new series of erythromycin A derivatives, the 6-O-heteroarylcarbamoyl-11,12-lactoketolides, with activity against macrolide-resistant streptococci, are described. Structurally, these macrolide antibiotics are characterized by a heteroaryl side chain attached to the macrolactone core through a carbamate linkage at the C6 position, as well as 11,12-gamma-lactone and 3-keto functionalities. The synthesis and antibacterial activity of this new series of ketolides are discussed.

Optimal pharmacological therapy for community-acquired pneumonia: the role of dual antibacterial therapy

The optimal pharmacological therapy of community-acquired pneumonia (CAP) is one of the most ardently debated issues in medicine. Presently, most guidelines recommend either a fluoroquinolone alone or dual therapy with a third-generation cephalosporin plus a macrolide in patients hospitalised with CAP, but few provide clinicians with specific considerations for selecting from these agents. Despite a similar spectrum of activity and favourable resistance patterns (for fluoroquinolones and third-generation cephalosporins) against CAP pathogens, there is emerging evidence that dual therapy may be superior to monotherapy in certain populations.In patients with non-severe CAP, the evidence supports the use of either monotherapy or dual therapy in most patients; however, patients with severe CAP or bacteraemic pneumococcal CAP experience improved survival when treated with dual therapy. It is unclear from this evidence if any specific combination of agents is the most effective, but the combination of a third-generation cephalosporin plus a macrolide is the most extensively studied. Dual therapy was superior to monotherapy irrespective of the susceptibility of the aetiological pathogen, thus insufficient antimicrobial spectrum does not explain the disparity. The most likely explanation for improved outcomes with dual therapy is the combined effect of optimised antimicrobial spectrum (including atypicals), decreased impact of resistance to a single agent and the immunomodulatory effects of macrolides. Increasing resistance in patients with non-severe CAP warrants the consideration of dual therapy and perhaps a reappraisal of agents usually reserved for second-line therapy, including doxycycline, in these populations as well. In light of the available evidence, dual therapy should be strongly considered in all patients with severe CAP, especially when complicated by pneumococcal bacteraemia.

Low-dose aerosol model of pneumococcal pneumonia in the mouse: utility for evaluation of antimicrobial efficacy

Current mouse models of pneumococcal infection have two disadvantages: (1) those that are not based on lung infections do not take into account the tissue pharmacokinetics of drugs in the lung parenchyma; and (2) those that are pneumonia models typically use large infectious doses to produce fulminant infections. The objective of this study was to determine the utility of a low-dose aerosol pneumonia model for evaluation of antimicrobial efficacy. Mice infected with penicillin-susceptible or non-susceptible pneumococci were left untreated or treated for 2.5 days with ertapenem in a range of doses. Efficacy was determined by the change in log10 colony-forming unit (CFU) counts and survival. Low-dose aerosol infection with the penicillin-susceptible strain 6303 produced an indolent pneumonia that was reliably lethal 1-2 weeks after infection. Ertapenem demonstrated bactericidal activity and prevented mortality over a range of doses after infection with strain 6303, but demonstrated only bacteriostatic activity at the highest doses used against the more resistant 1980 strain. A beneficial effect on survival was seen at doses approaching bioequivalence with the standard human dosage. The low-dose aerosol model of pneumococcal pneumonia in the mouse is a viable alternative model for the evaluation of antimicrobial efficacy. It may be particularly useful in the evaluation of drugs that concentrate in the alveolar epithelial lining fluid or lung parenchyma.

Efficacy of moxifloxacin for treatment of penicillin-, macrolide- and multidrug-resistant Streptococcus pneumoniae in community-acquired pneumonia

This pooled analysis of six prospective, multicentre trials aimed to determine the efficacy of moxifloxacin in community-acquired pneumonia (CAP) due to penicillin-, macrolide- and multidrug-resistant Streptococcus pneumoniae (MDRSP). At a central laboratory, isolates were identified and antimicrobial susceptibility determined (microbroth dilution). MDRSP was defined as resistance > or =3 drug classes. Patients received oral or sequential intravenous/oral 400 mg moxifloxacin once daily for 7-14 days. The primary endpoint was clinical success at test-of-cure for efficacy-valid patients with proven pretherapy S. pneumoniae infection. Of 140 S. pneumoniae isolated (112 respiratory, 28 blood), 23 (16.4%) were penicillin resistant, 26 (18.6%) macrolide resistant and 31 (22.1%) MDRSP. The moxifloxacin MIC90 was 0.25 microg/ml. Clinical cure with moxifloxacin was 95.4% (125/131) overall, and 100% (21/21) for penicillin-, 95.7% (22/23) for macrolide- and 96.4% (27/28) for multidrug-resistant strains. Moxifloxacin provided excellent clinical and bacteriological cure rates in CAP due to drug-resistant pneumococci.

Antimicrobial resistance of Streptococcus pneumoniae isolates in Athens, Greece

In order to determine the current antibiotic susceptibility of Streptococcus pneumoniae strains in Greece, the present study was performed on 282 clinical isolates collected from patients at the Sotiria Chest Hospital of Athens, Greece, during the years 1997-2003. Susceptibility testing revealed that 52 (18.4%) isolates were not susceptible to penicillin, with 13.1% demonstrating intermediate and 5.3% high-level resistance. One of the penicillin-non-susceptible isolates was also resistant to cefotaxime. Comparison with results of a previous study conducted at the same hospital during the period 1992-1993 showed that penicillin resistance had increased by 4.5%. The results of this study indicate the antimicrobial susceptibility of Streptococcus pneumoniae continues to change in Greece and continuous surveillance remains important for guiding empirical antibiotic therapy.

Pneumonia in the Nursing Home

Pneumonia syndromes may be caused by infection or the aspiration of food, acid, or particulate material. Antibiotic-resistant organisms or recurrent aspiration should be considered if the response to treatment is poor. Clinicians should consider discontinuing antibiotics if the resident's status rapidly returns to baseline after a noninfectious macro-aspiration event. The natural history of this process, however, is not well characterized. Diagnostic procedures including sputum gram stain, culture, and urinary antigen testing should be pursued to diagnose pathogens not covered by empiric therapy or to focus therapy with narrow spectrum agents. Sources of aspiration, including pharyngeal dysphagia, periodontal disease, and gastric regurgitation, should be identified and treated in hopes of preventing recurrence.

Bacteriological efficacy of 5-day therapy with telithromycin in acute maxillary sinusitis

Increasing resistance among the key pathogens responsible for community-acquired respiratory tract infections, namely Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis, has the potential to limit the effectiveness of the antibacterial agents available to treat these infections. Moreover, there are regional differences in the susceptibility patterns observed and, as treatment is usually empirical, choosing an effective treatment can be challenging. Telithromycin, the first ketolide to be approved for clinical use, offers an activity profile that covers the key respiratory pathogens including penicillin- and macrolide-resistant S. pneumoniae as well as beta-lactamase-producing H. influenzae and M. catarrhalis. In a pooled analysis of three large controlled clinical trials involving patients with acute maxillary sinusitis, the bacteriological efficacy of 5- or 10-day treatment with telithromycin and 10-day treatment with comparators was evaluated. Telithromycin administered as a once-daily 800 mg dose for 5 days achieved eradication rates of 91.8, 87.5 and 92.9% for S. pneumoniae, H. influenzae and M. catarrhalis, respectively. Bacteriological eradication of 8/10 and 12/14 isolates of S. pneumoniae resistant to penicillin and erythromycin, respectively, was also reported following 5-day treatment with telithromycin. The clinical efficacy of this regimen was equivalent to that of a 10-day regimen of telithromycin or standard 10-day courses of amoxicillin-clavulanic acid or cefuroxime axetil. Telithromycin 800mg given for 5 days was well tolerated, with the majority of adverse events being of mild or moderate intensity. These data suggest that telithromycin provides effective first-line therapy for use in patients with acute maxillary sinusitis in a short and convenient once-daily dosage regimen.

Efficacy of Telithromycin in Community-Acquired Pneumonia Caused by Pneumococci with Reduced Susceptibility to Penicillin and/or Erythromycin

BACKGROUND

The efficacy of oral telithromycin was assessed in patients with community-acquired pneumonia (CAP) caused by Streptococcus pneumoniae with reduced susceptibility to penicillin and/or erythromycin.

METHODS

Patients with CAP who had received telithromycin 800 mg once daily for 5 or 7-10 days (n = 2,289) in eight phase III clinical trials, or telithromycin 800 mg once daily for 7 days (n = 50) in a phase II study were included in this pooled analysis. Patients with S. pneumoniae as the cause of infection were identified, with particular focus on those infected with strains with reduced susceptibility to penicillin (intermediate, minimal inhibitory concentration (MIC) 0.12-1.0 mg/l; resistant, MIC >or=2.0 mg/l) and/or resistance to erythromycin (MIC >or=1.0 mg/l). Per-protocol clinical and bacteriological outcomes were assessed 7-14 days post-therapy in the phase III studies, and at 7-21 days post-therapy or at the end of therapy in the phase II study.

RESULTS

Of the 327 telithromycin-treated patients with S. pneumoniae infection, 61 (19%) were infected with strains with reduced susceptibility to penicillin and/or erythromycin. Clinical cure and bacterial eradication rates in these patients were 91.8% (56/61) and 93.4% (57/61), respectively. Corresponding clinical cure and bacterial eradication rates overall for all isolates of pneumococci were 94.5% (309/327) and 96.0% (314/327), respectively. All isolates with reduced susceptibility to penicillin and/or erythromycin were susceptible to telithromycin (MIC <or=1.0 mg/l).

CONCLUSION

These results indicate that telithromycin is an effective oral antibacterial for the treatment of CAP caused by pneumococci with reduced susceptibility to penicillin and/or erythromycin.

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.

A Chiral Benzoquinolizine-2-carboxylic Acid Arginine Salt Active against Vancomycin-Resistant Staphylococcus aureus

There is an urgent medical need for novel antibacterial agents to treat hospital infections, specially those caused by multidrug-resistant Gram-positive pathogens. The need may also be fulfilled by either exploring antibacterial agents having new mechanism of action or expanding known classes of antibacterial drugs. The paper describes a new chemical entity, compound 21, derived from hitherto little known "floxacin". The choice of the entity was made from a series of synthesized prodrugs and salts of the active chiral benzoquinolizine carboxylic acid, S-(-)-nadifloxacin. The chemistry, physicochemical characteristics, and essential bioprofile of 21 qualifies it for serious consideration as a novel drug entity against hospital infections of multi-drug-resistant Staphylococcus aureus, and its progress up to clinical phase I trials in humans is described.

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.

Gatifloxacin: a review of its use in the treatment of bacterial infections in the US

Gatifloxacin (Tequin) is an 8-methoxy fluoroquinolone approved in the US for use in the treatment of community-acquired pneumonia (CAP), acute exacerbations of chronic bronchitis (AECB), acute sinusitis, uncomplicated and complicated urinary tract infections (UTIs), pyelonephritis, gonorrhoea and uncomplicated skin and skin structure infections. Gatifloxacin has a broad spectrum of antibacterial activity in vitro and good clinical and bacteriological efficacy in patients with indicated infections following once-daily administration by the intravenous or oral routes. It is generally well tolerated; the most common adverse events are associated with the gastrointestinal tract and CNS. Recent approvals for the use of gatifloxacin in the treatment of CAP due to multidrug-resistant Streptococcus pneumoniae (MDRSP) and in uncomplicated skin and skin structure infections extend the role of this drug in the treatment of bacterial infections in the US.

A nationwide survey of physician office visits found that inappropriate antibiotic prescriptions were issued for bacterial respiratory tract infections in ambulatory patients

OBJECTIVE

Correlations between probabilities of resistance and the frequencies with which antibiotics were prescribed for treating bacterial respiratory infections were examined in a nationwide ambulatory population.

STUDY DESIGN AND SETTING

The data of a nationwide probability sample survey of visits to physician offices in the United States in 1999 were used to conduct this study of drug use. A clinical pharmacologist identified antibiotics prescribed during those visits using a large online database. The participating physicians diagnosed the bacterial respiratory infections. An infectious disease expert determined the probabilities of bacterial resistance from a nationwide antibiotic surveillance database.

RESULTS

Various bacterial respiratory infections were diagnosed during 6.5% of physician office visits in 1999. One or more antibiotics were prescribed during 51.0% of those visits. The probabilities of resistance to the most frequently prescribed antibiotics varied from 20% to 40% and showed a weak positive correlation with the frequencies of antibiotic prescriptions.

CONCLUSION

A significant number of inappropriate antibiotic prescriptions were issued for infections with a high probability of bacterial resistance to the prescribed antibiotics.

Antimicrobial resistance and treatment of community-acquired pneumonia

This article discusses the problem of antimicrobial resistance and how it affects the management of community-acquired pneumonia (CAP). The discussion is limited to infection with Streptococcus pneumoniae and to the treatment of patients hospitalized in a medical ward or an intensive care unit because of pneumococcal CAP.

A novel plasmid (pEMCJH03) isolated from moraxella catarrhalis possibly useful as a cloning and expression vector within this species

A preliminary screening study of six Moraxella catarrhalis isolates from primary school children in the Netherlands identified a small 3.5 kb plasmid (pEMCJH03), containing four open reading frames, which encoded three mobilizing and one replicase protein. Insertion of a kanamycin containing transposon (yielding pEMCJH04) allowed selection and isolation of the plasmid in Escherichia coli. Natural transformation of pEMCJH04 into M. catarrhalis was successful for 25% (3/12) of non-isogenic isolates, with no link between (lack of) transformability and genetic lineage or (lack of) transformability and complement phenotype, though the transformation efficiency was found to be rather low at approximately 615CFU/microg (range=60-1040CFU/microg ). This is only the second publication detailing a plasmid isolated from this important respiratory pathogen, and the ability to clone and express foreign proteins in M. catarrhalis using pEMCJH04 could help in the development of a vaccine expression vector, as well as providing a useful tool for studying promoter activity and in complementation studies of gene knockout mutants.

Cefdinir versus levofloxacin in patients with acute rhinosinusitis of presumed bacterial etiology: a multicenter, randomized, double-blind study

BACKGROUND

Treatment guidelines for acute bacterial rhinosinusitis (ABRS) recommend 10 to 14 days of therapy with high-dose amoxicillin, amoxicillin/clavulanate, cefdinir, cefpodoxime, cefuroxime, a macrolide, or a newer fluoroquinolone, among other agents.

OBJECTIVE

This study compared the clinical efficacy and tolerability of cefdinir and levofloxacin in patients with a diagnosis of acute rhinosinusitis of presumed bacterial origin.

METHODS

In this multicenter, double-blind, noninferiority study, ambulatory adult patients who had signs and symptoms for >7 to 21 days before the screening visit and radiographic findings consistent with acute rhinosinusitis were randomized to receive cefdinir 600 mg or levofloxacin 500 mg, each once daily for 10 days. Clinical and radiologic response rates were determined at the test-of-cure (TOC) visit, which took place 9 to 14 days after the completion of treatment.

RESULTS

Two hundred seventy-one patients (138 cefdinir, 133 levofloxacin) were enrolled and randomized to treatment at 27 study centers in the United States and Poland between November 2003 and March 2004. Of these, 241 (123 cefdinir, 118 levofloxacin) were clinically evaluable. The cefdinir group consisted of 75 women and 48 men, of whom 117 were white and 6 black; their mean (SD) age was 42.5 (14.3) years. The levofloxacin group consisted of 71 women and 47 men, of whom 111 were white and 7 black; their mean age was 40.4 (13.6) years. The 2 groups were similar in terms of presenting signs and symptoms and baseline radiographic findings. The most common presenting symptoms were sinus pain, sinus pressure, and purulent nasal discharge, each of which was reported by > or =89% of patients. Clinical cure rates at the TOC visit in the cefdinir and levofloxacin groups were 83% (102/123) and 86% (101/118), respectively (95% Cl for the difference in cure rates, -12.3 to 7.0). Cefdinir and levofloxacin were comparable in the treatment of infections classified as moderate to severe. The incidence of drug-related adverse events was generally comparable in the 2 treatment groups, although there were significant differences between cefdinir and levofloxacin in the incidence of vaginal moniliasis in women (11% vs 0%, respectively; P = 0.003), drug-related diarrhea (8% vs 1%; P = 0.005), and insomnia (0% vs 4%; P = 0.027). Only 2% of patients discontinued therapy prematurely as a result of a drug-related adverse event.

CONCLUSION

In this population of patients with ABRS, the extended-spectrum cephalosporin cefdinir was as efficacious as the fluoroquinolone levofloxacin, suggesting that cefdinir may be a suitable alternative to the currently recommended fluoroquinolones.

Gemifloxacin: a new fluoroquinolone

Gemifloxacin is a dual targeted fluoroquinolone with potent in vitro activity against Gram-positive, -negative and atypical human pathogens--pathogens considered to be important causes of community-acquired respiratory tract infections. Gemifloxacin demonstrates impressive minimal inhibitory concentrations (MIC 90 ) values against clinical isolates of Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, Chlamydia pneumoniae and Legionella spp., with MIC 90 values reported to be 0.016-0.06, < 0.0008-0.06, 0.008-0.3, 0.25, 0.125 and 0.016-0.07 microg/ml, respectively. Gemifloxacin is also active in vitro against a broad range of Gram-negative bacilli with MIC 90 values against the Enterobacteriaceae in the range of 0.016 to > 16 microg/ml ( Escherichia coli and Providencia stuartii, respectively), with the majority of the genus having MIC 90 drug concentrations < 0.5 microg/ml. The in vitro activity of gemifloxacin against anaerobic organisms is variable. The MIC values for gemifloxacin are not affected by beta-lactamase production nor by penicillin or macrolide resistance in S. pneumoniae. Gemifloxacin is approved by the FDA to be clinically efficacious against multi-drug resistant S. pneumoniae. The pharmacokinetics of gemifloxacin are such that the drug can be administered orally once-daily to yield or achieve sustainable drug concentrations exceeding the MIC values of clinically important organisms. Gemifloxacin has been shown to target both DNA gyrase (preferred target) and topoisomerase IV (secondary target) - enzymes critical for DNA replication and organism survival - against clinical isolates of S. pneumoniae. This dual targeting activity is thought to be important for reducing the likelihood for selecting for quinolone resistance. Gemifloxacin has been investigated and approved for therapy in patients with community-acquired pneumonia (CAP) and acute exacerbations of chronic bronchitis. In one study, more patients receiving gemifloxacin compared to clarithromycin remained free of exacerbations for longer periods of time (p < 0.016) and gemifloxacin had a shorter time to eradication of H. influenzae than did clarithromycin (p < 0.02). From efficacy studies, gemifloxacin was found to have an adverse profile that was comparable with other compounds. The most frequent side effects were diarrhoea, abdominal pain and headache. Gemifloxacin is a welcomed addition to currently available agents for the treatment of community-acquired lower respiratory tract infections. Other potential indications appear to be within the spectrum of this compound.

Trends in drug resistance, serotypes, and molecular types of Streptococcus pneumoniae colonizing preschool-age children attending day care centers in Lisbon, Portugal: a summary of 4 years of annual surveillance

Of the nasopharyngeal cultures recovered from 942 day care center (DCC) attendees in Lisbon, Portugal, 591 (62%) yielded Streptococcus pneumoniae during a surveillance performed in February and March of 1999. Forty percent of the isolates were resistant to one or more antimicrobial agents. In particular, 2% were penicillin resistant and 20% had intermediate penicillin resistance. Multidrug resistance to macrolides, lincosamides, and tetracycline was the most frequent antibiotype (17% of all isolates). Serotyping and molecular typing by pulsed-field gel electrophoresis were performed for 202 out of 237 drug-resistant pneumococci (DRPn). The most frequent serotypes were 6B (26%), 14 (22%), 19F (16%), 23F (10%), and nontypeable (12%). The majority (67%) of the DRPn strains were representatives of nine international clones included in the Pneumococcal Molecular Epidemiology Network; eight of them had been detected in previous studies. Fourteen novel clones were identified, corresponding to 26% of the DRPn strains. The remaining 7% of the strains were local clones detected in our previous studies. Comparison with studies conducted since 1996 in Portuguese DCCs identified several trends: (i) the rate of DRPn frequency has fluctuated between 40 and 50%; (ii) the serotypes most frequently recovered have remained the same; (iii) nontypeable strains appear to be increasing in frequency; and (iv) a clone of serotype 33F emerged in 1999. Together, our observations highlight that the nasopharynxes of children in DCCs are a melting pot of successful DRPn clones that are important to study and monitor if we aim to gain a better understanding on the epidemiology of this pathogen.

Increasing prevalence of multidrug-resistant Streptococcus pneumoniae in the United States over a 10-year period: Alexander Project

The Alexander Project is a global surveillance study conducted from 1992 to 2001. Minimum inhibitory concentrations and percent resistance to a panel of antimicrobial agents were determined according to National Committee for Clinical Laboratory Standards methodology. Resistance to penicillin (PEN-R) and erythromycin (ERY-R) have increased in the period 1992-2001 by 3.9 and 4.5 times to 20.7% and 27.9%, respectively. Joint PEN-ERY-R has increased 4.9 times, up to 15.3%. In 1992, 57.1% of all PEN-R isolates were also ERY-R, whereas in 2001, 75.8% were ERY-R. Resistance to only 1 antibiotic increased slightly, from 8% in 1992 to 12% in 2001, whereas resistance to more than 1 antibiotic increased 4.3 times, from 6.4% in 1992 to 27.8% of all strains in 2001. Multidrug-resistant pneumococci are an increasingly common finding in the United States. Three of four PEN-R isolates are also multiresistant. The rate of growth of multidrug resistance is higher than that of single antibiotic resistance.

Effectiveness of amoxicillin, azithromycin, cefprozil and clarithromycin in the treatment of acute otitis media in children: a population-based study

Population-based studies may give results different from randomized clinical trials assessing the efficacy of antibiotics.

OBJECTIVE

To determine the effectiveness of amoxicillin, azithromycin, cefprozil and clarithromycin in the treatment of acute otitis media (AOM) in children.

METHODS

Using Quebec Health Insurance databases (RAMQ), we selected a cohort of children aged < or = 6 years, with a first episode of AOM between 1999 and 2002. The index AOM was defined as a medical service claim with a diagnosis of AOM and an antibiotic dispensation in the following 72 hours. Failures were defined as a new antibiotic dispensation, a hospitalization or outpatient visit for complications related to AOM in the 30 days after the index AOM. Data were analyzed using logistic regression.

RESULTS

Overall, 12,693 failures occurred among 60,513 first episodes of AOM. Azithromycin was the only antibiotic that was associated with a decreased risk of failure overall, when compared to amoxicillin (OR 0.88, 95% CI: 0.82, 0.94). However in the first 3 days of treatment (n = 680), azithromycin was more associated with treatment failure (OR 1.6, 95% CI: 1.3, 2.0). Compared to amoxicillin, post-therapy failures (n = 9387) were more likely to occur with cefprozil (OR 1.2, 95%CI: 1.2, 1.3) but were less with azithromycin (OR 0.8 95% CI: 0.8, 0.9).

CONCLUSIONS

Azithromycin had the lowest risk of failure 30 days after the onset of treatment but an increased risk of failure during the first few days of treatment. Amoxicillin remains an effective first-line drug for treating first AOM episodes.

In vitro activities of novel 2-fluoro-naphthyridine-containing ketolides

In vitro activities of erythromycin A, telithromycin, and two investigational ketolides, JNJ-17155437 and JNJ-17155528, were evaluated against clinical bacterial strains, including selected common respiratory tract pathogens. Against 46 macrolide-susceptible and -resistant Streptococcus pneumoniae strains, the MIC(90) (MIC at which 90% of the isolates tested were inhibited) of the investigational ketolides was 0.25 microg/ml, twofold lower than that of telithromycin and at least 64-fold lower than that of erythromycin A. Against erm(B)-containing pneumococci, the MIC(90) of all the ketolides was 0.06 microg/ml. The MIC(90) of the investigational ketolides against mef(A)-containing pneumococci or pneumococci with both mef(A) and erm(B) was 0.25 microg/ml, two-and fourfold lower, respectively, than that of telithromycin. In contrast, the MICs of the investigational ketolides against macrolide-resistant S. pneumoniae strains with ribosomal mutations were similar to or, in some cases, as much as eightfold higher than those of telithromycin. Against Haemophilus influenzae, MICs of all the ketolides were < or =2 microg/ml. Against three Moraxella catarrhalis isolates, the MIC of the ketolides was 0.25 microg/ml. The ketolides inhibited in vitro protein synthesis, with 50% inhibitory concentrations ranging from 0.23 to 0.27 microM. In time-kill studies against macrolide-susceptible and erm- or mef-containing pneumococci, the ketolides were bacteriostatic to slowly bactericidal, with 24-h log(10) decreases ranging from 2.0 to 4.1 CFU. Intervals of postantibiotic effects for the ketolides against macrolide-susceptible and -resistant S. pneumoniae were 3.0 to 8.1 h.

Trends in antimicrobial resistance in 1,968 invasive Streptococcus pneumoniae strains isolated in Spanish hospitals (2001 to 2003): decreasing penicillin resistance in children's isolates

To address the public health problem of antibiotic resistance, the European Union (EU) founded the European Antimicrobial Resistance Surveillance System. A network of 40 hospitals that serve approximately 30% of the Spanish population (about 12 million) participated. Each laboratory reported data on antimicrobial susceptibility testing using standard laboratory procedures that were evaluated by an external quality control program. The antibiotic consumption data were obtained from the National Health System. We compared the antibiotic susceptibility of Spanish isolates of invasive Streptococcus pneumoniae (2001 to 2003) with antibiotic consumption. Invasive S. pneumoniae was isolated from 1,968 patients, 20% of whom were children at or below the age of 14 years. Of non-penicillin-susceptible strains (35.6%; 95% confidence interval, 34 to 37.2), 26.4% were considered intermediate and 9.2% were considered resistant. Between 2001 and 2003, penicillin resistance decreased from 39.5 to 33% overall and from 60.4 to 41.2% in children at or below the age of 14 years (P = 0.002). Resistance to erythromycin was at 26.6%, and coresistance with penicillin was at 19.1%. Of total isolates, the ciprofloxacin MIC was >2 mug/ml for 2.1%, with numbers increasing from 0.4% (2001) to 3.9% (2003). Total antibiotic use decreased from 21.66 to 19.71 defined daily doses/1,000 inhabitants/day between 1998 and 2002. While consumption of broad-spectrum penicillins, cephalosporins, and erythromycin declined, use of amoxicillin-clavulanate and quinolones increased by 17.5 and 27%, respectively. The frequency of antibiotic resistance in invasive S. pneumoniae in Spain was among the highest in the EU. However, a significant decrease in penicillin resistance was observed in children. This decrease coincided with the introduction of a heptavalent conjugate pneumoccocal vaccine (June 2001) and with a global reduction in antibiotic consumption levels.

Drug treatment of pneumococcal pneumonia in the elderly

Streptococcus pneumoniae has been recognised as a major cause of pneumonia since the time of Sir William Osler. Drug-resistant S. pneumoniae (DRSP), which have gradually become resistant to penicillins as well as more recently developed macrolides and fluoroquinolones, have emerged as a consequence of indiscriminate use of antibacterials coupled with the ability of the pneumococcus to adapt to a changing antibacterial milieu. Pneumococci use cell wall choline components to bind platelet-activating factor receptors, colonise mucosal surfaces and evade innate immune defenses. Numerous virulence factors that include hyaluronidase, neuraminidase, iron-binding proteins, pneumolysin and autolysin then facilitate cytolysis of host cells and allow tissue invasion and bloodstream dissemination. Changes in pneumococcal cell wall penicillin-binding proteins account for resistance to penicillins, mutations in the ermB gene cause high-level macrolide resistance and mutations in topoisomerase IV genes coupled with GyrA gene mutations alter DNA gyrase and lead to high-level fluoroquinolone resistance. Risk factors for lower respiratory tract infections in the elderly include age-associated changes in oral clearance, mucociliary clearance and immune function. Other risks for developing pneumonia include poor nutrition, hypoalbuminaemia, bedridden status, aspiration, recent viral infection, the presence of chronic organ dysfunction syndromes including parenchymal lung disease and recent antibacterial therapy. Although the incidence of infections caused by DRSP is rising, the effect of an increase in the prevalence of resistant pneumococci on mortality is not clear. When respiratory infections occur, rapid diagnosis and prompt, empirical administration of appropriate antibacterial therapy that ensures adequate coverage of DRSP is likely to increase the probability of a successful outcome when treating community-acquired pneumonia in elderly patients, particularly those with multiple risk factors for DRSP. A chest x-ray is recommended for all patients, but other testing such as obtaining a sputum Gram's smear is not necessary and should not prolong the time gap between clinical suspicion of pneumonia and antibacterial administration. The selection of antibacterials should be based upon local resistance patterns of suspected organisms and the bactericidal efficacy of the chosen drugs. If time-dependent agents are chosen and DRSP are possible pathogens, dosing should keep drug concentrations above the minimal inhibitory concentration that is effective for DRSP. Treatment guidelines and recent studies suggest that combination therapy with a beta-lactam and macrolide may be associated with a better outcome in hospitalised patients, and overuse of fluoroquinolones as a single agent may promote quinolone resistance. The ketolides represent a new class of macrolide-like antibacterials that are highly effective in vitro against macrolide- and azalide-resistant pneumococci. Pneumococcal vaccination with the currently available polysaccharide vaccine is thought to confer some preventive benefit (preventing invasive pneumococcal disease), but more effective vaccines, such as nonconjugate protein vaccines, need to be developed that provide broad protection against pneumococcal infection.

Levofloxacin versus ceftriaxone plus clarithromycin in the treatment of adults with community-acquired pneumonia requiring hospitalization

Consecutive adult patients admitted to the hospital with community-acquired pneumonia from January 2000 to September 2003 were included in this prospective observational cohort study. A total of 459 patients, 259 treated with levofloxacin in single drug therapy at a dose of 500 mg once a day and 209 with the combination of ceftriaxone plus clarithromycin at a dose of 2 g once a day and 500 mg every 12 h, respectively, were included. The hospital admission decision was made using a clinical guideline based on the Pneumonia Severity Index (PSI). Fifteen (6%) patients died in the group treated with levofloxacin in single drug therapy and 25 (12%) in the group treated with ceftriaxone plus clarithromycin (P = 0.024). The mortality differences between both treatment groups, adjusted by the PSI score, show an OR of 0.39 (95% CI 0.17-0.87). There were no statistically significant differences between the duration of treatments or hospital stay. These data suggest that levofloxacin as single drug therapy is more effective than the combination of ceftriaxone plus clarithromycin in the treatment of moderate to severe pneumonia that requires hospitalization.

Relationship between increased levofloxacin use and decreased susceptibility of Streptococcus pneumoniae in the United States

Increasing reports of fluoroquinolone-non-susceptible Streptococcus pneumoniae are of clinical concern. We examined the relationship between outpatient fluoroquinolone use and susceptibility of community-acquired S. pneumoniae isolates. Using multivariable general linear modeling, US SENTRY Antimicrobial Surveillance Program and Intercontinental Medical Statistics data (1997-2002) were analyzed to determine the influence of selected patient-, institution-, and geographic region-specific factors, including local fluoroquinolone usage, on the minimum inhibitory concentration (MIC) of levofloxacin against S. pneumoniae. Levofloxacin MIC50, MIC90, and MIC range (n = 384 from 26 hospitals) were 1, 1, and < or =0.5 to >4 microg/mL, respectively. Variables associated with changes in geometric mean MIC included geographical region (P < 0.0001), medical service (P = 0.0002), study year (P = 0.0006), primary diagnosis group (P = 0.02), and 2 interactions (duration of hospital stay before isolate collection by bed capacity, P = 0.06, and levofloxacin use by geographical region, P = 0.08; P < 0.001 when study year was removed from the model). MIC increased with levofloxacin use across all geographical regions, with increases of 54% and 126% in the southwest and west, respectively. In contrast to other fluoroquinolones, increased levofloxacin use, along with other variables, was associated with decreased pneumococcal susceptibility. Given the US environment of increasing pneumococcal resistance, these data may be useful in better understanding factors related to emergence of fluoroquinolone resistance.

Guide to selection of fluoroquinolones in patients with lower respiratory tract infections

Newer fluoroquinolones such as levofloxacin, moxifloxacin, gatifloxacin and gemifloxacin have several attributes that make them excellent choices for the therapy of lower respiratory tract infections. In particular, they have excellent intrinsic activity against Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis and the atypical respiratory pathogens. Fluoroquinolones may be used as monotherapy to treat high-risk patients with acute exacerbation of chronic bronchitis, and for patients with community-acquired pneumonia requiring hospitalisation, but not admission to intensive care. Overall, the newer fluoroquinolones often achieve clinical cure rates in > or =90% of these patients. However, rates may be lower in hospital-acquired pneumonia, and this infection should be treated on the basis of anticipated organisms and evaluation of risk factors for specific pathogens such as Pseudomonas aeruginosa. In this setting, an antipseudomonal fluoroquinolone may be used in combination with an antipseudomonalbeta-lactam. Concerns are now being raised about the widespread use, and possibly misuse, of fluoroquinolones and the emergence of resistance among S. pneumoniae, Enterobacteriaceae and P. aeruginosa. A number of pharmacokinetic parameters such as the peak concentration of the antibacterial after a dose (C(max)), and the 24-hour area under the concentration-time curve (AUC24) and their relationship to pharmacodynamic parameters such as the minimum inhibitory and the mutant prevention concentrations (MIC and MPC, respectively) have been proposed to predict the effect of fluoroquinolones on bacterial killing and the emergence of resistance. Higher C(max)/MIC or AUC24/MIC and C(max)/MPC or AUC24/MPC ratios, either as a result of dose administration or the susceptibility of the organism, may lead to a better clinical outcome and decrease the emergence of resistance, respectively. Pharmacokinetic profiles that are optimised to target low-level resistant minor subpopulations of bacteria that often exist in infections may help preserve fluoroquinolones as a class. To this end, optimising the AUC24/MPC or C(max)/MPC ratios is important, particularly against S. pneumoniae, in the setting of lower respiratory tract infections. Agents such as moxifloxacin and gemifloxacin with high ratios against this organism are preferred, and agents such as ciprofloxacin with low ratios should be avoided. For agents such as levofloxacin and gatifloxacin, with intermediate ratios against S. pneumoniae, it may be worthwhile considering alternative dose administration strategies, such as using higher dosages, to eradicate low-level resistant variants. This must, of course, be balanced against the potential of toxicity. Innovative approaches to the use of fluoroquinolones are worth testing in further in vitro experiments as well as in clinical trials.

Use of Macrolides and Tetracyclines for Chronic Inflammatory Diseases

OBJECTIVE:

To review the efficacy of macrolides and tetracyclines in several chronic inflammatory conditions.

DATA SOURCES:

Searches of MEDLINE (1966–March 2004) and an extensive bibliography search were undertaken. Key terms included acne, blepharitis, cardiovascular disease, cystic fibrosis, periodontitis, rosacea, and rheumatoid arthritis.

STUDY SELECTION AND DATA EXTRACTION:

Data were obtained primarily from randomized placebo-controlled trials upon which key recommendations are based.

DATA SYNTHESIS:

Antibiotics are often prescribed for months or even years for treatment of chronic inflammatory conditions such as acne, blepharitis, cardiovascular disease, cystic fibrosis, periodontitis, rosacea, and rheumatoid arthritis. Randomized controlled trials have shown that azithromycin is useful in the management of cystic fibrosis and the tetracyclines are beneficial in the management of rheumatoid arthritis, acne, blepharitis, and periodontitis. Several large, randomized controlled trials have failed to show any benefit of macrolides in the secondary prevention of cardiovascular disease. No randomized placebo-controlled clinical trials have been performed to assess the efficacy of macrolides or tetracyclines in patients with rosacea.

CONCLUSIONS:

The use of tetracyclines and macrolides for rosacea is based primarily on anecdotal reports or open-label trials. Limited clinical trials support the use of tetracyclines or macrolides in acne, blepharitis, periodontitis, rheumatoid arthritis, and cystic fibrosis. Trials to date do not support the use of antibiotics for secondary prevention of cardiovascular disease.

Macrolides and ketolides: azithromycin, clarithromycin, telithromycin

The advanced macrolides, azithromycin and clarithromycin, and the ketolide telithromycin are structural analogues of erythromycin. They have several distinct advantages when compared with erythromycin including enhanced spectrum of activity, more favorable pharmacokinetics and pharmacodynamics, once daily administration, and improved tolerability. This article reviews the pharmacokinetics, antimicrobial activity, clinical use, and adverse effects of these antimicrobial agents.

Patterns of health care resource utilization after macrolide treatment failure: Results from a large, population-based cohort with acute sinusitis, acute bronchitis, and community-acquired pneumonia

BACKGROUND

Macrolide antibiotics are used as first-line therapy for the treatment of respiratory tract infections. The recent emergence of macrolide-resistant pathogens is a major concern.

OBJECTIVE

This study quantifies the frequency of macrolide treatment failure in respiratory infections and examines its impact on health care use.

METHODS

Patients with respiratory infections treated with macrolides in outpatient clinics from January to December 2002 were identified from a health insurance claims database. Macrolide treatment failure was defined as the receipt of a second antibiotic, different from the first, within 4 weeks after the initial macrolide. The end points were numbers of hospitalizations and emergency department and office visits within 1 month after the initial macrolide. We examined diagnostic codes on claim forms for posttreatment hospitalizations and visits to identify those most likely to be related to treatment failure as opposed to other causes. Utilization data were analyzed by Poisson regression to control for confounding variables.

RESULTS

The patients were divided into acute sinusitis (n = 111,135), acute bronchitis (n = 157,360), and community-acquired pneumonia (n = 36,212). Of these respective groups, 11,285 (10.2%), 15,498 (9.9%), and 4144 (11.4%) received a second antibiotic within 4 weeks. This subgroup with macrolide treatment failure was older, included more women, and had used more medical care before the index visit compared with patients with treatment success. After adjustment for age, sex, and previous health care use, patients experiencing treatment failure were more likely to be admitted to the hospital or to use emergency department or outpatient care after the index visit. This association was strongest for admissions and visits pertaining to the care of respiratory infections.

CONCLUSIONS

By our definition, about 10% of patients with respiratory infections who were treated with macrolide antibiotics experienced treatment failure within 4 weeks. Macrolide treatment failure was associated with increased health care utilization.

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.

Septic arthritis in the adult caused by Streptococcus pneumoniae: A report of 4 cases and review of the literature

OBJECTIVES

To identify coexistent diseases, clinical features, approaches to management, and predictors of outcome in patients with pneumococcal septic arthritis.

METHODS

Case series of 4 adults with Streptococcus pneumoniae septic arthritis seen at a university hospital, plus a review of 115 adults with pneumococcal septic arthritis reported in the medical literature from 1973 through 2003.

RESULTS

Among our 4 patients, 3 had polyarticular infections, joint prostheses were involved in 1, 3 had underlying joint diseases, and 1 had concurrent meningitis. Infection was caused by penicillin-intermediate/cephalosporine-susceptible S pneumoniae in 1 patient and penicillin-resistant/cephalosporine-intermediate S. pneumoniae in 1 patient. After a mean treatment duration of 6 weeks, all patients were clinically cured of infection. Review of the literature identified 115 cases of S pneumoniae septic arthritis in adults. Clinical data were available for 107 patients. Twenty-nine cases were polyarticular (26%), joint prostheses were involved in 15 patients (13%), and 61 patients had underlying joint disease (57%). Meningitis was a concurrent infection in 15 cases. The presumed primary focus of infection was the respiratory tree in 44 patients. Ninety-six percent of cases were caused by penicillin-susceptible organisms. Cure of infection with survival was achieved in 83% (79 of 95) of patients with native joint septic arthritis and in 67% (8 of 12) of patients with prosthetic joint infection. A good functional outcome (full range of motion or return to baseline range of motion) after infection was achieved by 44 of 71 patients (62%) with native joint infection and by 4 of 7 patients (57%) with infections of prosthetic joints. The likelihood of cure of infection or good functional outcome was not influenced by method of joint drainage.

CONCLUSIONS

S pneumoniae is an uncommon, but not rare, cause of septic arthritis in the adult. Many patients have underlying joint disease (especially rheumatoid arthritis) and coexistent alcoholism. Although most infections involve native joints, prosthetic joint infections comprise 13% of cases. Polyarticular disease occurs in approximately one quarter of patients. Most patients have a preceding or concurrent extra-articular focus of pneumococcal infection. To date, the majority of reported infections are caused by penicillin-susceptible organisms, so penicillin G or a third-generation cephalosporine such as ceftriaxone remains the appropriate treatment option. However, infection with drug-resistant organisms is likely to be an increasing problem in the future. With directed antimicrobial therapy and appropriate joint drainage, the outcome is generally good for patients with native joint infections. In contrast, only two thirds of patients with infections of prosthetic joints survive their infections. Approximately 40% of surviving patients experience functional impairment or chronic pain as a sequelae of their infection.

The Changing Face of Antibiotic Prescribing: The Mutant Selection Window

OBJECTIVE

To describe the mutant selection window, discuss supporting evidence and limitations, and suggest potential applications for clinical practice.

DATA SOURCES

A MEDLINE search (1990–December 2003) of the English-language literature was conducted using the key words antibiotic, antimicrobial, resistance, mutant, selection window, prevention, MPC, and MSW in various combinations. Original investigations and reviews evaluating the mutant selection window, including abstracts and proceedings, were considered for inclusion. Published articles were also cross-referenced, and experts were contacted to locate additional pertinent data.

STUDY SELECTION AND DATA EXTRACTION

All data sources identified were evaluated and all information deemed relevant was included.

DATA SYNTHESIS

Until recently, physicians have had few ways to preserve antimicrobials from resistance other than by prescribing the agents less often. The mutant selection window hypothesis may modify this paradigm by shifting the focus to dosing strategies that reduce the growth of resistant mutants. Conventional dosing strategies have been formulated on the likelihood of curing an individual patient. Unfortunately, doses that cure patients appear to enrich resistant subpopulations of bacteria, thus promoting resistance. Antimicrobial—pathogen combinations can be identified that minimize mutant selection and cure patients while possibly restricting the progression of resistance.

CONCLUSIONS

The mutant selection window hypothesis provides a framework for considering the contribution of dosing to resistance, and it offers ideas for restricting the enrichment of resistant mutants and antimicrobial resistance.

In vitro and bactericidal activities of ABT-492, a novel fluoroquinolone, against Gram-positive and Gram-negative organisms

In vitro activities of ABT-492, ciprofloxacin, levofloxacin, trovafloxacin, moxifloxacin, gatifloxacin, and gemifloxacin were compared. ABT-492 was more potent against quinolone-susceptible and -resistant gram-positive organisms, had activity similar to that of ciprofloxacin against certain members of the family Enterobacteriaceae, and had comparable activity against quinolone-susceptible, nonfermentative, gram-negative organisms. Bactericidal activity of ABT-492 was also evaluated.

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.

Antibiotic agents in the elderly

Diagnosis and treatment of infections in the elderly is challenging and complicated because of age-related physiologic changes and lack of classical clinical symptoms. Elderly patients are more vulnerable to infections because of their underlying diseases. This article reviews the pharmacologic issues in treating the elderly with antibiotics, the most frequently encountered infections in this patient population, and the suggested antibiotic regimens. The discussion also includes the special challenges of treating these most frequently encountered infections in the elderly who reside in long-term care facilities.

Optimal use of antibiotic resistance surveillance systems

Increasing concern about the emergence of resistance in clinically important pathogens has led to the establishment of a number of surveillance programmes to monitor the true extent of resistance at the local, regional and national levels. Although some programmes have been operating for several years, their true usefulness is only now being realised. This review describes some of the major surveillance initiatives and the way in which the data have been used in a number of different settings. In the hospital, surveillance data have been used to monitor local antibiograms and determine infection control strategies and antibiotic usage policies. In the community, surveillance data have been used to monitor public health threats, such as infectious disease outbreaks involving resistant pathogens and the effects of bioterrorism countermeasures, by following the effects of prophylactic use of different antibiotics on resistance. Initially, the pharmaceutical industry sponsored surveillance programmes to monitor the susceptibility of clinical isolates to marketed products. However, in the era of burgeoning resistance, many developers of antimicrobial agents find surveillance data useful for defining new drug discovery and development strategies, in that they assist with the identification of new medical needs, allow modelling of future resistance trends, and identify high-profile isolates for screening the activity of new agents. Many companies now conduct pre-launch surveillance of new products to benchmark activity so that changes in resistance can be monitored following clinical use. Surveillance data also represent an integral component of regulatory submissions for new agents and, together with clinical trial data, are used to determine breakpoints. It is clear that antibiotic resistance surveillance systems will continue to provide valuable data to health care providers, university researchers, pharmaceutical companies, and government and regulatory agencies.

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

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

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.

Clarithromycin in 2003: sustained efficacy and safety in an era of rising antibiotic resistance

Data from surveillance studies show increasing prevalence of respiratory pathogens resistant to commonly used antibiotics. Thus, a Medline search was conducted to identify studies of clarithromycin, especially those addressing macrolide resistance. Changing trends of in vitro susceptibility have not affected clinical efficacy with clarithromycin. Over the last 12 years, clarithromycin study results have shown consistent rates of clinical cure and bacteriological eradication, which are similar to those observed with comparator agents. The incidence of clarithromycin treatment failure in patients infected with Streptococcus pneumoniae is substantially less than that predicted by macrolide resistance rates from surveillance programmes. In summary, despite widespread use since its introduction, clarithromycin remains active both in vitro and in vivo against clinically relevant respiratory tract pathogens.

Quinolone-Resistant Haemophilus influenzae in a Long-Term Care Facility: Clinical and Molecular Epidemiology

We describe a clonal outbreak of quinolone-resistant Haemophilus influenzae (QRHI) from an affiliated long-term care facility (LTCF-A); the outbreak was associated with the clinical use of levofloxacin, which was determined to be a risk factor for acquisition of QRHI. The minimum inhibitory concentration to which 90% of isolates were susceptible (MIC90), as determined by broth microdilution, was >4 microg/mL for levofloxacin, >2 microg/mL for moxifloxacin, >2 microg/mL for gatifloxacin, and 8 microg/mL for gemifloxacin. The MIC90, as determined by Etest (AB Biodisk), was >32 microg/mL for levofloxacin, ciprofloxacin, moxifloxacin, and gatifloxacin. Having been a resident at LTCF-A and having chronic obstructive pulmonary disease were significant risk factors for acquisition of QRHI at our 500-bed hospital (New York Hospital Queens). All QRHI isolates were found to be genetically related by pulsed-field gel electrophoresis, were nontypeable, were susceptible to ceftriaxone and azithromycin, and were negative for beta -lactamase production. Emphasis on patient contact and respiratory isolation and placing colonized or infected patients in cohorts yielded a marked reduction in the prevalence of QRHI at LTCF-A.

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

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