Activity of BMS284756 against 2,681 recent clinical isolates of Haemophilus influenzae and Moraxella catarrhalis: Report from The SENTRY Antimicrobial Surveillance Program (2000) in Europe, Canada and the United States

Nasal carriage of common bacterial pathogens among healthy kindergarten children in Chaoshan region, southern China: a cross-sectional study

BACKGROUND

Nasal colonization with bacterial pathogens is associated with risk of invasive respiratory tract infections, but the related information for Chinese healthy children is scarce.

METHODS

This cross-sectional study was conducted with healthy children from 6 kindergartens in the Chaoshan region, southern China during 2011-2012. Nasal swabs were examined for five common bacterial pathogens: Streptococcus pneumoniae, Haemophilus influenzae, Haemophilus parainfluenzae, Moraxella catarrhalis, and Staphylococcus aureus.

RESULTS

Among 1,088 children enrolled, 79.6 % (866) were target-bacterial carriers, of which 34.4 % (298/866) were positive for ≥2 bacteria species. The most common pathogen in the bacterial carriers was M. catarrhalis (76.6 %), followed by S. pneumoniae (26.6 %), S. aureus (21.8 %), H. parainfluenzae (12.7 %), and H. influenzae (2.3 %). Multiple logistic regression analyses showed negative associations between age and the overall or multiple bacterial carriage, and between the father's education level and multiple bacterial carriage (all p < 0.05). Age was negatively associated with the carriage of M. catarrhalis and S. pneumoniae, and positively associated with the S. aureus carriage (all p < 0.0001).

CONCLUSIONS

This study shows high nasal carriage of common pathogenic bacteria and coexistence of multiple pathogens in healthy Chaoshan kindergarten children, with M. catarrhalis as the commonest colonizer. Increasing age of children and higher paternal education are associated with lower risk of bacterial carriage. Longitudinal follow-up studies would be helpful for better understanding the infection risk in bacterial pathogen carriers.

A Review of New Fluoroquinolones : Focus on their Use in Respiratory Tract Infections

The new respiratory fluoroquinolones (gatifloxacin, gemifloxacin, levofloxacin, moxifloxacin, and on the horizon, garenoxacin) offer many improved qualities over older agents such as ciprofloxacin. These include retaining excellent activity against Gram-negative bacilli, with improved Gram-positive activity (including Streptococcus pneumoniae and Staphylococcus aureus). In addition, gatifloxacin, moxifloxacin and garenoxacin all demonstrate increased anaerobic activity (including activity against Bacteroides fragilis). The new fluoroquinolones possess greater bioavailability and longer serum half-lives compared with ciprofloxacin. The new fluoroquinolones allow for once-daily administration, which may improve patient adherence. The high bioavailability allows for rapid step down from intravenous administration to oral therapy, minimizing unnecessary hospitalization, which may decrease costs and improve quality of life of patients. Clinical trials involving the treatment of community-acquired respiratory infections (acute exacerbations of chronic bronchitis, acute sinusitis, and community-acquired pneumonia) demonstrate high bacterial eradication rates and clinical cure rates. In the treatment of community-acquired respiratory tract infections, the various new fluoroquinolones appear to be comparable to each other, but may be more effective than macrolide or cephalosporin-based regimens. However, additional data are required before it can be emphatically stated that the new fluoroquinolones as a class are responsible for better outcomes than comparators in community-acquired respiratory infections. Gemifloxacin (except for higher rates of hypersensitivity), levofloxacin, and moxifloxacin have relatively mild adverse effects that are more or less comparable to ciprofloxacin. In our opinion, gatifloxacin should not be used, due to glucose alterations which may be serious. Although all new fluoroquinolones react with metal ion-containing drugs (antacids), other drug interactions are relatively mild compared with ciprofloxacin. The new fluoroquinolones gatifloxacin, gemifloxacin, levofloxacin, and moxifloxacin have much to offer in terms of bacterial eradication, including activity against resistant respiratory pathogens such as penicillin-resistant, macrolide-resistant, and multidrug-resistant S. pneumoniae. However, ciprofloxacin-resistant organisms, including ciprofloxacin-resistant S. pneumoniae, are becoming more prevalent, thus prudent use must be exercised when prescribing these valuable agents.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Épidémiologie et évaluation de la sensibilité aux antibiotiques de souches d'Haemophilus influenzae isolées en 2004 en France

OBJECTIVES

The aim of this study was to describe the epidemiology of H. influenzae strains collected in 2004 at the National Reference Center and to evaluate their susceptibility to various antibiotics.

METHODS

Demographic and clinical characteristics, capsular serotyping by slide agglutination with specific antisera, beta-lactamase by a chromogenic cephalosporin test (Nitrocefin) and MICs of amoxicillin, co-amoxiclav, cefpodoxime, cefaclor, cefuroxime, cefotaxime, erythromycin, pristinamycin and telithromycin by agar dilution method on Haemophilus Test Medium were determined for each strain.

RESULTS

807 strains of H. influenzae were identified: 41.8% from bronchial secretions (BS), 16.2% from conjunctivitis, 6.6% from otitis media (OM), 4.2% from CSF and 8.6% from blood cultures. 95.6% of strains was not capsulated and 4.4% was of serotype b, e, or f. 26.3% of strains was beta-lactamase producing (TEM type). 185 isolates (22.8% of total strains) had reduced susceptibility to beta-lactams due to modification of the target associated or not with beta-lactamase production. When beta-lactamase was produced, the MICs of amoxicillin increased, but the activity of the other antibiotics was unchanged. Low BLNAR strains showed an increase in the MICs of all beta-lactams. This increase was weak and variable according to beta-lactams. Pristinamycin and telithromycin activities were unchanged against these strains. Two strains were resistant to erythromycin.

CONCLUSIONS

Theses results show that both beta-lactamase and modifications of the target are widespread among H. influenzae strains isolated in France. Cefpodoxime remains the most active compounds against H. influenzae, whatever the resistance mechanisms, followed by pristinamycin, telithromycin, and co-amoxiclav.

Penetration of moxifloxacin into sternal bone of patients undergoing routine cardiopulmonary bypass surgery

This study investigated plasma and bone concentrations of moxifloxacin following a single intravenous dose of 400mg to consider its potential role in the treatment of osteomyelitis. Eight patients who underwent routine cardiopulmonary bypass surgery were enrolled in the study. Plasma and bone samples were collected 2h and 5h after the end of infusion. High performance liquid chromatography was used for the determination of moxifloxacin concentrations. Mean plasma concentrations were 3.36 microg/mL and 2.93 microg/mL at 2h and 5h after the end of infusion. The concentrations in the body and manubrium of the sternal bone were 1.65 microg/g and 1.64 microg/g at 2h and 1.4 microg/g and 1.45 microg/g at 5h, respectively. Moxifloxacin showed good penetration into bone and could be considered for the treatment of osteomyelitis.

Community-acquired pneumonia in Shanghai, China: microbial etiology and implications for empirical therapy in a prospective study of 389 patients

The aim of this multicenter study was to identify the causative pathogens of community-acquired pneumonia (CAP) in Shanghai, China, and to determine their susceptibility to antimicrobial agents. Pathogens obtained from 389 patients with documented CAP during 2001-2003 were identified by multiple diagnostic tools that included bacterial culture, polymerase chain reaction (PCR), and specific immunological assays. Susceptibility of the bacterial isolates was tested by the broth microdilution method. A specific pathogen was identified in 39.8% (155/389) of the patients: Haemophilus influenzae (n=80), Klebsiella spp. (n=15), Streptococcus pneumoniae (n=12), Staphylococcus aureus (n=6), Moraxella catarrhalis (n=1), other gram-negative organisms (n=9), and atypical pathogens that comprised Mycoplasma pneumoniae (n=42), Chlamydia pneumoniae (n=17), and Legionella pneumophila (n=2). Most H. influenzae isolates were susceptible to ampicillin (88.3%), and all were susceptible to macrolides. Of the S. pneumoniae isolates, 75% (9/12) were susceptible to penicillin, while 25% (3/12) were intermediately susceptible. H. influenzae and atypical pathogens are among the most important pathogens of CAP. Ampicillin, cephalosporins, and the newer fluoroquinolones can be used as empirical therapy for CAP in the Shanghai area. The efficacy of monotherapy with newer macrolides for CAP caused by S. pneumoniae requires further evaluation.

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.

[Epidemiology of Haemophilus influenzae strains identified in 2001 in France, and assessment of their susceptibility to beta-lactams]

The aim of this study was to describe the epidemiology of H. influenzae strains collected in 2001 at the National Reference Center and to evaluate their susceptibility to beta-lactams.

METHODS

The demographic characteristics were recorded for each strain, then were determined their capsular serotyping (slide agglutination with specific antisera), as well as their beta-lactamase production (chromogenic cephalosporin test, Nitrocefin), and their MICs (agar dilution method on Haemophilus Test Medium) for amoxicillin (AMX), co-amoxiclav (AMC), cefpodoxime (CPD), cefaclor (CEC), cefuroxime (CXM), and cefotaxime (CTX).

RESULTS

41.3% of the 752 strains were identified in bronchial secretions, 20.6% in conjunctivitis, 11.3% in otitis media, and 11% in blood cultures. 96.3% of the strains were not capsulated and 3.7% were of type b, d, e or f. 33.8% of the strains were beta-lactamase producers (TEM type), 45.8% of these were identified in otitis pus and 27.7% in bronchial secretions. One hundred and forty-two strains (18.9%) presented reduced susceptibility to beta-lactams (modification of target) associated or not with bla+. MICs 50/90 against bla+ strains were: AMX 1/32, AMC 0.12/1, CTX 0.007/0.03, CPD 0.03/0.12, CEC 1/64, CXM 0.25/1. Against low BLNAR and bla+ strains, MICs 50/90 were: AMX 2/32, AMC 0.25/2, CTX 0.015/0.06, CPD 0.06/0.25, CEC 4/64, CXM 0.25/4. And against low BLNAR strains MICs 50/90 were: AMX 0.25/8, AMC 0.25/8, CTX 0.015/0.12, CPD 0.06/0.50, CEC 4/32, CXM 0.25/4.

CONCLUSIONS

Both bla+ and modifications of PBP are widespread among strains isolated in France. CTX, and CPD remain the most active compounds whatever the resistance mechanisms.

Cefdinir: a review of its use in the management of mild-to-moderate bacterial infections

Cefdinir (Omnicef) is an oral third-generation cephalosporin with good in vitro activity against many pathogens commonly causative in community-acquired infections. The drug provides good coverage against Haemophilus influenzae, Moraxella catarrhalis and penicillin-susceptible Streptococcus pneumoniae, the most common respiratory tract pathogens. Cefdinir is stable to hydrolysis by commonly occurring plasmid-mediated beta-lactamases and retains good activity against beta-lactamase-producing strains of H. influenzae and M. catarrhalis. The drug distributes into various tissues (e.g. sinus and tonsil) and fluids (e.g. middle ear), and has a pharmacokinetic profile that allows for once- or twice-daily administration.Cefdinir, administered for 5 or 10 days, has shown good clinical and bacteriological efficacy in the treatment of a wide range of mild-to-moderate infections of the respiratory tract and skin in adults, adolescents and paediatric patients in randomised, controlled trials. In adults and adolescents, cefdinir is an effective treatment for both lower (acute bacterial exacerbations of chronic bronchitis [ABECB], community-acquired pneumonia) and upper (acute bacterial rhinosinusitis, streptococcal pharyngitis) respiratory tract infections, and uncomplicated skin infections. Its bacteriological and clinical efficacy in patients with lower respiratory tract infections was equivalent to that of comparator agents (cefprozil [bacteriological only], loracarbef, cefuroxime axetil and cefaclor). In one trial in patients with ABECB, cefdinir produced a higher rate of clinical cure than cefprozil (95% CIs indicated nonequivalence). Cefdinir also produced good clinical and bacteriological responses equivalent to responses with amoxicillin/clavulanic acid in patients with acute bacterial rhinosinusitis. In addition, it was at least as effective as penicillin V (phenoxymethylpenicillin) in streptococcal pharyngitis/tonsillitis and as effective as cefalexin in uncomplicated skin infections. In paediatric patients aged > or =6 months, cefdinir showed similar efficacy to that of amoxicillin/clavulanic acid or cefprozil in acute otitis media, and cefalexin in uncomplicated skin infections. Cefdinir given for 5 or 10 days was at least as effective as penicillin V for 10 days in patients with streptococcal pharyngitis/tonsillitis. Cefdinir is usually well tolerated. Diarrhoea was the most common adverse event in trials in all age groups. Although the incidence of diarrhoea in cefdinir recipients was generally higher than in adults and adolescents treated with comparators, discontinuation rates due to adverse events were generally similar for cefdinir and comparator groups. In conclusion, cefdinir is a third-generation cephalosporin with a broad spectrum of antibacterial activity encompassing pathogens that are commonly causative in infections of the respiratory tract or skin and skin structure. Depending on the infection being treated, cefdinir can be administered as a convenient once- or twice-daily 5- or 10-day regimen. Clinical evidence indicates that cefdinir is an effective and generally well tolerated drug with superior taste over comparator antibacterial agents and is therefore a good option for the treatment of adults, adolescents and paediatric patients with specific mild-to-moderate respiratory tract or skin infections, particularly in areas where beta-lactamase-mediated resistance among common community-acquired pathogens is a concern.

Antimicrobial activities of garenoxacin (BMS 284756) against Asia-Pacific region clinical isolates from the SENTRY program, 1999 to 2001

Between 1999 and 2001, 16,731 isolates from the Asia-Pacific Region were tested in the SENTRY Program for susceptibility to six fluoroquinolones including garenoxacin. Garenoxacin was four- to eightfold less active against Enterobacteriaceae than ciprofloxacin, although both drugs inhibited similar percentages at 1 microg/ml. Garenoxacin was more active against gram-positive species than all other fluoroquinolones except gemifloxacin. For Staphylococcus aureus, oxacillin resistance was high in many participating countries (Japan, 67%; Taiwan, 60%; Hong Kong, 55%; Singapore, 52%), with corresponding high levels of ciprofloxacin resistance (57 to 99%) in oxacillin-resistant S. aureus (ORSA). Of the ciprofloxacin-resistant ORSA isolates, the garenoxacin MIC was >4 microg/ml for only 9% of them. For Streptococcus pneumoniae, penicillin nonsusceptibility and macrolide resistance were high in many countries. No relationship was seen between penicillin and garenoxacin susceptibility, with all isolates being susceptible at <2 microg/ml. There was, however, a partial correlation between ciprofloxacin and garenoxacin MICs. For ciprofloxacin-resistant isolates for which garenoxacin MICs were 0.25 to 1 microg/liter, mutations in both the ParC and GyrA regions of the quinolone resistance-determining region could be demonstrated. No mutations conferring high-level resistance were detected. Garenoxacin shows useful activity against a wide range of organisms from the Asia-Pacific region. In particular, it has good activity against S. aureus and S. pneumoniae, although there is evidence that low-level resistance is present in those organisms with ciprofloxacin resistance.

In vitro activities of garenoxacin (BMS-284756) against Haemophilus influenzae isolates with different fluoroquinolone susceptibilities

The in vitro activity of garenoxacin (BMS-284756) against 62 clinical Haemophilus influenzae isolates with different fluoroquinolone susceptibilities was determined by the microdilution susceptibility testing method and compared with the activities of other oral quinolones and nonquinolone oral antimicrobial agents. Cefixime presented the highest intrinsic activity (MIC at which 50% of the isolates tested were inhibited [MIC(50)], 0.01 microg/ml), followed by garenoxacin, moxifloxacin, and ciprofloxacin (MIC(50), 0.06 microg/ml), levofloxacin (MIC(50), 0.12 microg/ml), cefuroxime (MIC(50), 1.0 microg/ml), and amoxicillin-clavulanate (MIC(50), 1.0/0.5 microg/ml), amoxicillin (MIC(50), 2 microg/ml), azithromycin (MIC(50), 4 microg/ml), and erythromycin (MIC(50), 8 microg/ml). In strains with ciprofloxacin MICs of < or =0.06 microg/ml, ciprofloxacin and garenoxacin displayed similar MIC(50)s and MIC(90)s, one dilution lower than those of moxifloxacin and levofloxacin. For strains for which ciprofloxacin MICs were > or = 0.12 microg/ml, MIC(50)s were similar for the four quinolones tested, although garenoxacin presented the widest activity range (0.03 to 32 microg/ml) and the highest MIC at which 90% of the isolates tested were inhibited (16.0 microg/ml). For strains without amino acid changes in the quinolone resistance determining region (QRDR) of GyrA and ParC, garenoxacin MICs were < or =0.03 microg/ml; with a single amino acid change in GyrA, garenoxacin MICs were 0.06 to 0.12 microg/ml; with one amino acid change each in GyrA and ParC, garenoxacin MICs were 0.5 to 2.0 micro g/ml; one amino acid change in ParC combined with two amino acid changes in GyrA increased the MICs to > or = 4 microg/ml for all assayed quinolones. We conclude that garenoxacin has excellent activity against H. influenzae, although progressive acquired resistance was observed by step-by-step mutation in the QRDR of gyrA and parC.

Susceptibility trends of haemophilus influenzae and Moraxella catarrhalis against orally administered antimicrobial agents: five-year report from the SENTRY Antimicrobial Surveillance Program

The assessment of orally administered antimicrobial susceptibilities of common pathogens that cause community-acquired respiratory tract infections (CARTI) has become exceedingly important due to the number of office visits for this indication. Numerous local, regional and global studies have documented the susceptibilities of Haemophilus influenzae, Streptococcus pneumoniae, and Moraxella catarrhalis, the most common CARTI pathogens. SENTRY Antimicrobial Surveillance Program sites in North and Latin America, and Europe were requested to send a combined total of 100 isolates of these pathogens to the local monitor for reference broth microdilution testing (1997-2001). This study compared the susceptibility profiles of H. influenzae and M. catarrhalis isolates (13,370 strains) from the three geographic regions over a five year period. beta-lactamase mediated ampicillin resistance among H. influenzae was highest among North American isolates (27.9%) compared to Latin America and Europe (16.2 to 16.3%), although it was noted that during the five year study period, ampicillin resistance was steadily increasing in the latter two regions. Cefprozil (84.3% susceptible) and clarithromycin (81.1% susceptible) were also less active against North American H. influenzae isolates. Latin American isolates were much less susceptible to trimethoprim/sulfamethoxazole (T/S; 59.3%) compared to the other regions (75.8 to 78.6%). M. catarrhalis isolates were also significantly less susceptible to T/S in Latin America (10.5% resistance). The production of beta-lactamase enzymes among the M. catarrhalis isolates exceeded >95% in all three regions during the five year period. The fluoroquinolones (FQ) remained very active against these two respiratory pathogens with rare isolates with elevated FQ MIC results. It is apparent from this investigation that many commonly prescribed empiric treatments remain viable therapeutic options for CARTI caused by these two Gram-negative respiratory tract pathogens.

Fluoroquinolones in the Treatment of Meningitis

The continuous increase of resistant pathogens causing meningitis has limited the efficacy of standard therapeutic regimens. Due to their excellent activity in vitro and their good penetration into the cerebrospinal fluid (CSF), fluoroquinolones appear promising for the treatment of meningitis caused by gram-negative microorganisms, ie, Neisseria meningitidis and nosocomial gram-negative bacilli. The newer fluoroquinolones (moxifloxacin, gemifloxacin, gatifloxacin, and garenoxacin) have excellent activity against gram-positive microorganisms. Studies in animal models and limited clinical data indicate that they may play a future role in the treatment of pneumococcal meningitis. Analysis of pharmacodynamic parameters suggests that CSF concentrations that produce a C(peak)/minimal bactericidal concentration (MBC) ratio of at least 5 and concentrations above the MBC during the entire dosing interval are a prerequisite for maximal bactericidal activity in meningitis. Of interest, newer fluoroquinolones act synergistically with vancomycin and beta-lactam antibiotics (ceftriaxone, cefotaxime, meropenem) against penicillin-resistant pneumococci in experimental rabbit meningitis, potentially providing a new therapeutic strategy. Clinical trials are needed to further explore the usefulness of quinolones as single agents or in combination with other drugs in the therapy of pneumococcal meningitis.

Five-year analysis of Haemophilus influenzae isolates with reduced susceptibility to fluoroquinolones: prevalence results from the SENTRY antimicrobial surveillance program

The appearance of resistance or reduced susceptibility to fluoroquinolones among Hemophilus influenzae has been documented for nearly a decade. Over this time, the use of fluoroquinolones for the treatment of respiratory infections including commonly isolated bacterial causes of community-acquired infections has markedly increased. The documentation of resistance to fluoroquinolones among Streptococcus pneumoniae and H. influenzae has also become more prevalent as measured by peer-reviewed publications. During 1997-2001, a total of 11,355 H. influenzae isolates were tested by reference broth microdilution methods from strains collected by the SENTRY Antimicrobial Surveillance Program (American and European medical centers). Strains with reduced susceptibility to fluoroquinolones (RSF) were detected during all five study years at an overall rate of 0.15%. Among the tested compounds, sitafloxacin (MIC(50,) 0.03 microg/ml) was the most potent agent against the RSF strains, followed by gemifloxacin (0.12 microg/ml) > garenoxacin = grepafloxacin = levofloxacin = moxifloxacin = trovafloxacin (0.5 microg/ml) > ciprofloxacin = sparfloxacin (1 microg/ml). Gene sequencing of the quinolone resistance determining region and epidemiologic typing of 30 RSF isolates showed diverse mutational events in gyr A and par C and multiple pulsed-field gel electrophoresis (PFGE) patterns among strains that was not consistent with clonal dissemination. Continued surveillance by global or national networks should continue to monitor for H. influenzae isolates that are refractory to fluoroquinolone therapy.

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

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

Actividad in vitro comparativa de garenoxacino (BMS-284756). Programa SENTRY España (1999-2000)

INTRODUCTION

To evaluate the in vitro activity of the new des-fluoro quinolone, garenoxacin (BMS-284756), compared to activities of ciprofloxacin, levofloxacin, and gatifloxacin in clinical isolates recovered over 1999 and 2000 within the SENTRY antimicrobial surveillance program.

METHODS

Quinolone-MICs were performed using the standard NCCLS microdilution technique in 2599 isolates recovered from Hospital Ramón y Cajal (Madrid), Virgen Macarena (Sevilla), and Bellvitge (Barcelona).

RESULTS

The modal MIC range value exhibited by garenoxacin ( < or = 0.03-0.12 mg/L) for Enterobacteriaceae was similar to that of the other quinolones tested. A total of 70% of Pseudomonas aeruginosa isolates were susceptible to garenoxacin and 85% to ciprofloxacin and levofloxacin. Garenoxacin exhibited the highest activity in Staphylococcus aureus, including both methicillin-susceptible and -resistant isolates, with MIC90 values of < or = 0.03 and 2 mg/L, respectively. All Streptococcus pneumoniae isolates were susceptible to garenoxacin, regardless of their penicillin susceptibility status; in terms of MIC90, garenoxacin was 16 times more active than ciprofloxacin and levofloxacin and 4-8 times more active than gatifloxacin. All 6 ciprofloxacin-resistant S. pneumoniae strains showed garenoxacin MIC values ranging from < or = 0.03 to 0.5 mg/L. In Haemophilus influenzae and Moraxella catarrhalis, garenoxacin displayed excellent in vitro activity (MIC < or = 0.06 mg/L), similar to that of the other quinolones tested.

CONCLUSIONS

Garenoxacin activity was similar to the activity of other quinolones in Enterobacteriaceae, but was lower in P. aeruginosa. Garenoxacin activity was clearly higher than that of other quinolones in gram-positive isolates, including methicillin-resistant S. aureus and S. pneumoniae with reduced penicillin susceptibility.

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

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

Microbiology of newer fluoroquinolones: focus on respiratory pathogens

Community-acquired pneumonia, acute exacerbations of chronic bronchitis, and acute sinusitis are among the most common bacterial infections encountered in clinical practice. Pathogens frequently associated with these infections include Streptococcus pneumoniae, Hemophilus influenzae, Moraxella catarrhalis, Chlamydia pneumoniae, Legionella pneumophila, and Mycoplasma pneumoniae. Unfortunately, resistance to antimicrobials commonly used for the treatment of these infections is increasing, limiting the clinical efficacy of these agents. Fluoroquinolones offer several advantages over other classes of antimicrobials used for the treatment of community-acquired respiratory tract infections. In general, fluoroquinolones have excellent in vitro activity against common respiratory pathogens, including some drug-resistant strains of S. pneumoniae. Microbial resistance to the newer fluoroquinolones is relatively uncommon, currently occurring in approximately 1% of clinical isolates in North America. Fluoroquinolones currently in clinical development may offer additional benefits over the marketed agents because they maintain good potency against isolates of S. pneumoniae displaying resistance to older quinolones (i.e., ofloxacin or ciprofloxacin) and may have a lower potential to engender resistance. This article reviews the in vitro activity of several newer fluoroquinolones, including agents currently in clinical development, against common respiratory pathogens, including antimicrobial-resistant strains. The mechanisms and prevalence of resistance of beta-lactam antimicrobials, macrolides, and fluoroquinolones also are reviewed.

Gatifloxacin: a review of its use in the management of bacterial infections

Gatifloxacin is an 8-methoxy fluoroquinolone antibacterial agent. The drug has a broader spectrum of antibacterial activity than the older fluoroquinolones (e.g. ciprofloxacin) and shows good activity against many Gram-positive and Gram-negative pathogens, atypical organisms and some anaerobes. Notably, gatifloxacin is highly active against both penicillin-susceptible and -resistant strains of Streptococcus pneumoniae, a common causative pathogen in community-acquired pneumonia (CAP), acute sinusitis and acute bacterial exacerbations of bronchitis. Gatifloxacin is absorbed well from the gastrointestinal tract (oral bioavailability is almost 100%). Therefore, patients can be switched from intravenous to oral therapy without an adjustment in dosage. High concentrations of gatifloxacin are achieved in plasma and target tissues/fluids. Gatifloxacin has a long plasma elimination half-life, thus allowing once-daily administration. Few clinically significant interactions between gatifloxacin and other drugs have been reported. In patients with CAP, clinical response rates in recipients of intravenous/oral gatifloxacin 400 mg/day ranged from 86.8 to 98.0% and rates of bacterial eradication ranged from 83.1 to 100% (up to 28 days post-treatment). Gatifloxacin showed efficacy similar to that of amoxicillin/clavulanic acid, ceftriaxone (with or without erythromycin) with or without stepdown to clarithromycin, levofloxacin or clarithromycin. Gatifloxacin was as effective as clarithromycin or amoxicillin/clavulanic acid, and was significantly more effective (in terms of clinical response; p < 0.035) than 7 to 10 days' treatment with cefuroxime axetil in the treatment of acute exacerbations of chronic bronchitis. In acute sinusitis, gatifloxacin showed clinical efficacy similar to that of clarithromycin, trovafloxacin or amoxicillin/clavulanic acid. Genitourinary infections were also successfully treated with gatifloxacin. Gatifloxacin is generally well tolerated. Its tolerability profile was broadly similar to those of comparator agents in comparative trials. The most common adverse events are gastrointestinal symptoms (oral formulation) and injection site reactions.

CONCLUSIONS

Gatifloxacin has an extended spectrum of antibacterial activity and provides better coverage of Gram-positive organisms (e.g. S. pneumoniae) than some older fluoroquinolones. The drug has favourable pharmacokinetic properties, is administered once daily and is at least as well tolerated as other fluoroquinolones. Gatifloxacin is a useful addition to the fluoroquinolones currently available for use in the clinical setting and has an important role in the management of adult patients with various bacterial infections. As with other fluoroquinolones, careful control of gatifloxacin usage in the community is important in order to prevent the emergence of bacterial resistance and thus preserve the clinical value of this agent.