Susceptibility of European respiratory tract isolates to trovafloxacin, ciprofloxacin, clarithromycin, azithromycin and ampicillin

Beta-lactam/beta-lactamase inhibitor combinations in empiric management of pediatric infections

Beta-lactam antibiotics have long played a central role in the management of pediatric infections. However, widespread beta-lactam resistance among community- and hospital-acquired pathogens, mainly due to beta-lactamase production, has reduced the usefulness of these trusted and well-tolerated agents. Many regions have reported an increase in beta-lactamase-mediated resistance to cephalosporins and carbapenems as well as penicillins among clinically important Gram-positive and Gram-negative aerobes and anaerobes. For some pathogens such as Moraxella catarrhalis, Klebsiella species and Pseudomonas aeruginosa, virtually all strains worldwide are beta-lactamase producers. The development of beta-lactamase inhibitors for co-administration with a number of established beta-lactam agents has restored their usefulness in pediatric patients. The combination of ampicillin plus sulbactam has broad anti-aerobic and anti-anaerobic activity in vitro and achieves high concentrations in many body tissues and fluids. The availability of a mutual oral prodrug, sultamicillin, has enabled the development of an oral formulation. Excellent clinical response and bacterial eradication rates with ampicillin/sulbactam and sultamicillin have been demonstrated for upper and lower respiratory tract infections, urinary tract infections, osteomyelitis, and meningitis in pediatric patients and neonates. Furthermore, many studies have demonstrated an excellent tolerability profile. Thus, ampicillin/sulbactam has an important role in the management of pediatric infections.

Community-acquired pneumonia in ambulatory patients: relative importance of atypical pathogens

The presence of atypical pathogens in community-acquired pneumonia is difficult to diagnose; culture is time-consuming and requires considerable expertise and serological identification may be inaccurate. Nevertheless, the increasing importance of atypical organisms has been recognised in recent years. Variations in aetiology have been detected in different geographical regions and different patient populations. The season of the year may also influence aetiology, and some infections follow a cyclical pattern. When an atypical pathogen is suspected, a macrolide antibiotic is an appropriate choice as, in addition to activity against these organisms, they are usually effective against the Gram-positive and Gram-negative respiratory pathogens implicated in community-acquired pneumonia.

The clinical impact of macrolide resistance in pneumococcal respiratory infections

By the 1960s, several reports of bacteria with reduced susceptibility to antibiotics were published. In recent years, the problem of antibiotic resistance has magnified. In the treatment of respiratory tract infections, the development of resistance is of particular concern; 67% of antibiotic use in adults and 87% in children is for the treatment of such infections. Streptococcus pneumoniae is the most common cause of community-acquired pneumonia and is a frequently isolated bacterial species in patients with other respiratory tract infections. Increasing levels of resistance may have important implications in the clinical setting. Physicians need to consider local susceptibility data, in addition to the pharmacokinetic and pharmacodynamic features of compounds, when selecting appropriate antibiotics for the treatment of bacterial infections.

Worldwide guidelines for respiratory tract infections: community-acquired pneumonia

The management of respiratory tract infections is a complex process. Concern over increasing levels of bacterial resistance and the inappropriate use of antibiotics has led to the development of clinical guidelines for the treatment of respiratory tract infections. Despite the development of these guidelines, a consensus on the optimal care for lower respiratory tract infections has not been attained. Guidelines for the management of community-acquired pneumonia (CAP) have been developed since the 1990s in the USA, Canada, and a number of European countries. Constant re-evaluation of guidelines for CAP is necessary to ensure that the recommendations that were made in the early 1990s still hold true in the new millennium.

Prevalence of antimicrobial resistance in Haemophilus influenzae, Streptococcus pneumoniae, Moraxella catarrhalis and Streptococcus pyogenes: results of a multicentre study in Turkey

The in vitro activities of several antimicrobial agents against clinical isolates of Streptococcus pneumoniae (283), Haemophilus influenzae (272), Moraxella catarrhalis (179) and Streptococcus pyogenes (256) were determined in a multicentre study with the participation of five hospitals from four cities in Turkey. Penicillin resistance in S. pneumoniae was evaluated using the E-test and the remaining agents by disk diffusion. For S. pneumoniae overall 25.8% of the isolates were intermediately and 3.9% were highly resistant to penicillin and resistance to chloramphenicol, azithromycin and trimethoprim/sulphamethoxazole (TMP/SMX) was 3.8, 2.1 and 55.4%, respectively. Seven percent of H. influenzae produced beta-lactamase and all were susceptible to cefotaxime and azithromycin; the highest rate of resistance, 23.5%, was for TMP/SMX. Eighty-one percent of M. catarrhalis isolates produced beta-lactamase, 18.4% were resistant to TMP/SMX and all were susceptible to sulbactam/ampicillin combination. Resistance to chloramphenicol and azithromycin of S. pyogenes was 2.2 and 1.9%, respectively.

Role of sultamicillin and ampicillin/sulbactam in the treatment of upper and lower bacterial respiratory tract infections

The emergence of beta-lactamase-mediated resistance to beta-lactam antibiotics among key respiratory tract pathogens has threatened the usefulness of the beta-lactam agents familiar to physicians as being clinically effective and well tolerated. This article reassesses the clinical usefulness of ampicillin when administered in combination with the beta-lactamase inhibitor sulbactam, either intravenously or orally (as the mutual prodrug sultamicillin), in the treatment of upper and lower respiratory tract infections. Numerous clinical studies and several meta-analyses indicate that ampicillin/sulbactam and sultamicillin are clinically effective and well tolerated in both adults and children, in agreement with published North American and European guidelines.

Comparative study of treatment with penicillin, ceftriaxone, trovafloxacin, quinupristin-dalfopristin and vancomycin in experimental endocarditis due to penicillin- and ceftriaxone-resistant Streptococcus pneumoniae

The efficacy of different antibiotics was compared in an experimental model of aortic valve endocarditis in rabbits, using a serotype 19 strain of Streptococcus pneumoniae resistant to penicillin (MIC 12 mg/L) and ceftriaxone (MIC 12 mg/L). The results were compared with those of a control group, which received no treatment. One hundred and nineteen animals were treated with one of the following antibiotic regimens: im procaine penicillin G at a dosage of 300,000 U/kg weight/12 h (16 animals); iv trovafloxacin, 13.3 mg/kg/12 h (31 animals); iv ceftriaxone, 75 mg/kg/24 h (21 animals); iv vancomycin, 20 mg/kg/12 h (15 animals) and im quinupristin-dalfopristin, 30 mg/kg/8 h (20 animals). All the antibiotics used in this study proved to be efficient in reducing numbers of S. pneumoniae and in increasing the percentage of aortic vegetations that were rendered sterile compared with the control group. Penicillin at the dosage used in our study was capable of achieving serum concentrations two or three times greater than the MIC, thus demonstrating its effectiveness as an antibiotic for this endocarditis model. No significant difference was observed between the effects of vancomycin, quinupristin-dalfopristin and penicillin. Vancomycin proved to be more efficient than trovofloxacin in reducing the bacterial load and increasing the numbers sterilized. There was also a tendency for this antibiotic to be more effective than ceftriaxone in reducing the bacterial load of the vegetations. There was a statistically significant correlation between the weight of the vegetations and their bacterial load. In the light of these results, vancomycin and quinupristin-dalfopristin may be considered suitable alternatives to penicillin for the treatment of penicillin-resistant S. pneumoniae endocarditis.

Ability of laboratories to detect emerging antimicrobial resistance: proficiency testing and quality control results from the World Health Organization's external quality assurance system for antimicrobial susceptibility testing

The accuracy of antimicrobial susceptibility data submitted by microbiology laboratories to national and international surveillance systems has been debated for a number of years. To assess the accuracy of data submitted to the World Health Organization by users of the WHONET software, the Centers for Disease Control and Prevention distributed six bacterial isolates representing key antimicrobial-resistance phenotypes to approximately 130 laboratories, all but one of which were outside of the United States, for antimicrobial susceptibility testing as part of the World Health Organization's External Quality Assurance System for Antimicrobial Susceptibility Testing. Each laboratory also was asked to submit 10 consecutive quality control values for several key organism-drug combinations. Most laboratories were able to detect methicillin (oxacillin) resistance in Staphylococcus aureus, high-level vancomycin resistance in Enterococcus faecium, and resistance to extended-spectrum cephalosporins in Klebsiella pneumoniae. Many laboratories, particularly those using disk diffusion tests, had difficulty in recognizing reduced susceptibility to penicillin in an isolate of Streptococcus pneumoniae. The most difficult phenotype for laboratories to detect was reduced susceptibility to vancomycin in an isolate of Staphylococcus epidermidis. The proficiency testing challenge also included a request for biochemical identification of a gram-negative bacillus, which most laboratories recognized as Enterobacter cloacae. Although only a small subset of laboratories have submitted their quality control data, it is clear that many of these laboratories generate disk diffusion results for oxacillin when testing S. aureus ATCC 25923 and S. pneumoniae ATCC 49619 that are outside of the acceptable quality control range. The narrow quality control range for vancomycin also proved to be a challenge for many of the laboratories submitting data; approximately 27% of results were out of range. Thus, it is important to establish the proficiency of laboratories submitting data to surveillance systems in which the organisms are tested locally, particularly for penicillin resistance in pneumococci and glycopeptide resistance in staphylococci.

Antipseudomonal antibiotics

Pseudomonas aeruginosa is responsible for a variety of nosocomial infections associated with high morbidity and mortality, involving the immunocompromised and immunocompetent host. There are several groups of antipseudomonal antibiotics available today: antipseudomonal penicillins (carboxy and ureido penicillins), antipseudomonal cephalosporins, monobactams, quinolones, aminoglycosides, and carbapenems. This article reviews the newer antipseudomonal compounds and focuses on recent and important pieces of information for older compounds. Antibacterial spectrum, with particular emphasis on contemporary resistance mechanisms, and recent global resistance surveillance reports, pharmacokinetics, in vitro combination studies and in vivo interactions, and adverse effects and dosage schedules are described in an effort to approach the clinicians' needs.

Sensibilidade a antimicrobianos de bactérias isoladas do trato respiratório de pacientes com infecções respiratórias adquiridas na comunidade: resultados brasileiros do Programa SENTRY de Vigilância de Resistência a Antimicrobianos dos anos de 1997 e 1998

O tratamento da pneumonia adquirida na comunidade (PAC) é habitualmente empírico e o uso de antimicrobianos é baseado em estudos de vigilância. O programa SENTRY foi desenhado para monitorar a resistência a antimicrobianos através de uma rede internacional de laboratórios. Três centros no Brasil participaram do Programa SENTRY em 1997 e em 1998. Métodos: Um total de 344 isolados bacterianos coletados de pacientes com PAC em 1997 e 1998 foram testados contra mais de 20 agentes antimicrobianos pelo método de microdiluição em caldo. Resultados: Entre os S. pneumoniae (176 isolados), 71,6% foram sensíveis à penicilina. Alto nível de resistência à penicilina e resistência à cefotaxima foram encontrados em 2,3 e 4,0%, respectivamente. As novas quinolonas levofloxacina (MIC90, 2mig/mL) e gatifloxacina (MIC90, 0,5mig/mL) foram ativas contra 100% dos isolados testados. Entre os outros antimicrobianos não beta-lactâmicos testados, os mais ativos foram (% de sensibilidade): cloranfenicol (97,5%) > clindamicina (94%) > azitromicina (90,3%) > claritromicina (89,4%) > tetraciclina (76,4%) > sulfametoxazol/trimetoprim (60,2%). A percentagem de Haemophilus influenzae (101 isolados) resistentes à amoxicilina foi de 90,1%, enquanto entre Moraxella catarrhalis (67 isolados) somente 9,0% foram sensíveis. O ácido clavulânico restaurou a atividade de amoxicilina contra H. influenzae e M. catarrhalis. Porém, H. influenzae demonstrou níveis aumentados de resistência para sulfametoxazol/trimetoprim (55,1% de sensibilidade), claritromicina (80,4% de sensibilidade) e cefaclor (88,2% de sensibilidade). Todos os isolados de H. influenzae e M. catarrhalis foram sensíveis à levofloxacina (MIC90, <= 0,5mig/mL para ambos) e gatifloxacina (MIC90, <= 0,06mig/mL para ambos) apresentando MICs muito baixos. Conclusões: Os resultados indicam que a prevalência de S. pneumoniae com alto grau de resistência à penicilina é ainda baixa no Brasil; porém, a prevalência de S. pneumoniae com resistência intermediária à penicilina e resistência cruzada a outras classes de antimicrobianos é relativamente alta em nosso meio. Por outro lado, as novas quinolonas são altamente ativas contra S. pneumoniae e outros patógenos responsáveis por infecções respiratórias adquiridas na comunidade.

Azithromycin versus pivampicillin in the treatment of acute exacerbations of chronic bronchitis: a single-blind, double-dummy, multicentre study

This single-blind, double-dummy, multicentre study compared oral azithromycin, administered as tablets, 500 mg once daily for 3 days, versus oral pivampicillin, 700 mg twice daily for 10 days, in adults with acute exacerbations of chronic bronchitis (not needing parenteral antibiotic therapy, hospitalization or oxygen support). Clinical success (cure + improvement) rates were similar for both groups at the end of treatment (day 10; azithromycin, 124 of 133 [93%]; pivampicillin, 79 of 92 [86%]) and at follow-up (day 52; 98 of 126 [78%] versus 66 of 81 [81%]). The treatments produced similar levels of pathogen eradication at the end of treatment (49 of 54 [91%] versus 32 of 37 [86%]). Azithromycin-treated patients had significantly reduced chest discomfort at the end of treatment, and a trend towards improved lung function. The two groups were similar with respect to improvements in other clinical symptoms and patient well-being, and to the incidences of adverse events and treatment discontinuations. This oral azithromycin regime is an effective treatment for acute exacerbations of chronic bronchitis, similar in efficacy to the longer pivampicillin regime and may offer superior patient compliance.

Azithromycin: indications for the future?

The global challenge of optimally treating bacterial infections is continuously evolving. Azithromycin, the first azalide antibiotic, presents pharmacokinetics and pharmacodynamics that allow for a simple dosing regimen with minimal side effects. Current azithromycin uses include a variety of community-acquired respiratory tract, skin and soft tissue, and sexually transmitted disease infections. Azithromycin has also demonstrated substantial activity against atypical organisms such as Mycobacterium avium complex (MAC) and Chlamydia trachomatis. Due to a never-ending need for new antibiotic therapies, several other potential indications for azithromycin are being researched. This article will present various current research associated with azithromycin's potential use for malaria, trachoma, coronary artery disease (CAD), Pseudomonas aeruginosa infections, erythema migrans, short-term therapy for respiratory infections, typhoid, cryptosporidiosis, pelvic inflammatory disease, acne, Mediterranean spotted fever and MAC. As bacterial and parasite resistance patterns fluctuate globally, azithromycin may be an alternative therapy for the previously mentioned indications, which will also enhance patient compliance and therefore effectively eradicate infection worldwide.

Beta-lactamases and beta-lactamase inhibitors

Penicillin, the first of the beta-lactam antibiotics, was introduced into medical practice in the 1940s. Since then, a large number of different beta-lactams, including penicillins, cephalosporins, monobactams, and carbapenems, have been developed, all of which are structurally related through the presence of a core beta-lactam ring. Resistance to beta-lactam antibiotics among target pathogens developed early in the history of their use. Of the mechanisms of resistance, the most widespread and most important is the destruction of the beta-lactam ring, which is mediated by beta-lactamases. The fact that these resistance enzymes may be coded on plasmids means that they are mobile within a bacterial community, and that they have spread widely. Resistance to beta-lactams mediated by beta-lactamases can be overcome successfully with the use of beta-lactamase inhibitors. The combination of beta-lactams with beta-lactamase inhibitors restores the activity of the beta-lactams, allowing their continued clinical use. The development of beta-lactamase inhibitors allows clinicians to rely on the well-tolerated, clinically effective beta-lactam antibiotics to treat a variety of bacterial infections.

The macrolides: erythromycin, clarithromycin, and azithromycin

In addition to erythromycin, macrolides now available in the United States include azithromycin and clarithromycin. These two new macrolides are more chemically stable and better tolerated than erythromycin, and they have a broader antimicrobial spectrum than erythromycin against Mycobacterium avium complex (MAC), Haemophilus influenzae, nontuberculous mycobacteria, and Chlamydia trachomatis. All three macrolides have excellent activity against the atypical respiratory pathogens (C. pneumoniae and Mycoplasma species) and the Legionella species. Azithromycin and clarithromycin have pharmacokinetics that allow shorter dosing schedules because of prolonged tissue levels. Both azithromycin and clarithromycin are active agents for MAC prophylaxis in patients with late-stage acquired immunodeficiency syndrome (AIDS), although azithromycin may be the preferable agent because of fewer drug-drug interactions. Clarithromycin is the most active MAC antimicrobial agent and should be part of any drug regimen for treating active MAC disease in patients with or without AIDS. Although both azithromycin and clarithromycin are well tolerated by children, azithromycin has the advantage of shorter treatment regimens and improved tolerance, potentially improving compliance in the treatment of respiratory tract and skin or soft tissue infections. Intravenously administered azithromycin has been approved for treatment of adults with mild to moderate community-acquired pneumonia or pelvic inflammatory diseases. An area of concern is the increasing macrolide resistance that is being reported with some of the common pathogens, particularly Streptococcus pneumoniae, group A streptococci, and H. influenzae. The emergence of macrolide resistance with these common pathogens may limit the clinical usefulness of this class of antimicrobial agents in the future.

Trovafloxacin versus high-dose amoxicillin (1 g three times daily) in the treatment of community-acquired bacterial pneumonia

Once-daily trovafloxacin 200 mg was compared with high-dose amoxicillin, 1 g three times daily, given for 7 to 10 days. At end of treatment (day 10), the response was clinically successful (cure + improvement) in 93% of 152 clinically evaluable trovafloxacin patients and in 89% of 160 amoxicillin patients. At study end (day 35), respective rates were 91% and 81% (95% confidence interval: 1.6, 17.6; P=0.01). In evaluable patients with positive baseline radiographs, 93% of trovafloxacin and 88% of amoxicillin patients demonstrated radiological resolution at end of treatment. Streptococcus pneumoniae and Haemophilus influenzae eradication rates were comparable at end of treatment in both treatment groups, but at study end Streptococcus pneumoniae eradication rates were higher in trovafloxacin patients (100% vs 81%). At study end, all four trovafloxacin patients with baseline penicillin-resistant Streptococcus pneumoniae were clinically cured with pathogen eradication, whereas two of five amoxicillin patients with baseline penicillin-resistant Streptococcus pneumoniae were clinical failures with pathogen persistence. For patients in whom no pathogen was identified, trovafloxacin was significantly more effective at end of treatment (P=0.096) and study end (P=0.013). Treatment-related adverse events were comparable; the most common were headache, vomiting and dizziness in trovafloxacin patients, and diarrhoea. headache and abdominal pain in amoxicillin patients.