In vitro activity of gemifloxacin (SB 265805) against anaerobes

Post-resection complications: abscesses, empyemas, bronchopleural fistulas

The role of thoracic surgeons in the management of pulmonary infection has evolved over time as the medical treatments have improved. We herein review historical and current management for surgically-treated pulmonary infections-lung abscesses, empyemas, and bronchopleural fistulas. In particular, we review when the surgeons need to be involved for infectious cases, our algorithm/approach to empyemas, and summary of post-operative bronchopleural fistula in tuberculosis cases.

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.

Bacterial Infections in the Elderly Patient: Focus on Sitafloxacin

Sitafloxacin (DU-6859a) is a new-generation oral fluoroquinolone with in vitro activity against a broad range of Gram-positive and -negative bacteria, including anaerobic bacteria, as well as against atypical bacterial pathogens. Particularly in Japan this antibiotic was approved in 2008 for treatment of a number of bacterial infections caused by Gram-positive cocci and Gram-negative cocci and rods, including anaerobia atypical bacterial pathogens. As compared to oral levofloxacin sitafloxacin was non-inferior in the treatment of community-acquired pneumonia and non-inferior in the treatment of complicated urinary tract infections, according to the results of randomized, double-blind, multicentre, non-inferiority trials. Non-comparative studies demonstrated the efficacy of oral sitafloxacin in otorhinolaryngological infections, urethritis in men, cervicitis in women and odontogenic infections. Most common adverse reactions were gastrointestinal disorders and laboratory abnormalities in patients receiving oral sitafloxacin; diarrhea and liver enzyme elevations were among the common. In the Japanese population sitafloxacin covers broad spectrum of bacteria as compared to carbapenems, whereas in the Caucasians its use is currently limited due to the potential for ultraviolet A phototoxicity. Sitafloxacin is a promising therapeutic agent which merits further investigation in randomized clinical trials of elderly patients.

Levofloxacin for the treatment of community-acquired pneumonia

New respiratory fluoroquinolones (FQs), such as levofloxacin, offer many improved qualities over older agents, such as ciprofloxacin. These include retaining excellent Gram-negative bacilli activity, with improved Gram-positive activity. New FQ-like levofloxacin possesses greater bioavailabilty and a longer serum half-life compared with ciprofloxacin, allowing for once-daily dosing, which may improve patient adherence. The high bioavailability of levofloxacin allows for rapid step-down from intravenous administration to oral therapy, minimizing unnecessary hospitalization, which may decrease costs and improve patient quality of life. Levofloxacin has been evaluated for the treatment of community-acquired pneumonia (CAP) in numerous randomized clinical trials. Most published studies have used the 500 mg dose, although more recent studies have investigated the 750 mg dose once daily. These trials demonstrate that levofloxacin is effective and safe for the treatment of CAP, displaying relatively mild adverse effects that are more or less comparable with ciprofloxacin. Levofloxacin has much to offer in terms of bacterial eradication, including for resistant respiratory pathogens. However, ciprofloxacin-resistant organisms are becoming more prevalent so prudence must be exercised when prescribing this agent.

In vitro antianaerobic activity of DX-619, a new des-fluoro(6) quinolone

The in vitro activity of DX-619, a new des-F(6) quinolone, against anaerobic bacteria was evaluated. DX-619 showed potent activity against Bacteroides, Prevotella, Fusobacterium, Micromonas, Actinomyces, and Clostridium spp., with MIC(50)s/MIC(90)s of </=0.03 to 0.25/</=0.03 to 1 microg/ml, respectively. DX-619 was also active against imipenem-resistant Bacteroides spp., with MIC(50)s/MIC(90)s of 0.25/1 microg/ml, respectively.

Antimicrobial therapy of Clostridium difficile-associated diarrhea

Clostridium difficile-associated diarrhea (CDAD) is the most common etiologically-defined cause of hospital-acquired diarrhea. Caused by the toxins of certain strains of C difficile, CDAD represents a growing concern, with epidemic outbreaks in some hospitals where very aggressive and difficult-to-treat strains have recently been found. Incidence of CDAD varies ordinarily between 1 to 10 in every 1,000 admissions. Evidence shows that CDAD increases morbidity, length of stay, and costs. This article described the clinical manifestations of CDAD, related risk factors, considerations for confirming CDAD, antimicrobial and non-antimicrobial treatment of CDAD, and issues related to relapses. The article concludes with a discussion of recent epidemic outbreaks involving CDAD.

Clostridium aldenense sp. nov. and Clostridium citroniae sp. nov. isolated from human clinical infections

One hundred eight isolates were previously identified in our laboratory as Clostridium clostridioforme by colonial and cellular morphology, as well as biochemical tests. Recent studies have indicated that there are actually three different species in this C. clostridioforme group: C. hathewayi, C. bolteae, and C. clostridioforme. Our isolates were reexamined using biochemical and enzymatic tests and molecular methods. Forty-six isolates were reidentified as C. hathewayi, 34 as C. bolteae, five as C. clostridioforme, and one as C. symbiosum. Twenty-two strains were identified only to the genus level by 16S rRNA gene sequencing, and although they are microscopically and morphologically indistinguishable from the above-mentioned three species, they are phenotypically different and only 96 to 98% similar by gene sequencing. Twenty of these 22 strains were indole positive and formed two novel species. We propose Clostridium aldenense sp. nov. and Clostridium citroniae sp. nov. as names for these new species. They are differentiated from each other by results for raffinose, rhamnose, alpha-galactosidase, and beta-galactosidase: positive, negative, positive, and positive, respectively, for the former species and negative, positive, negative, and negative, respectively, for the latter species. The type strain of C. aldenense is RMA 9741 (ATCC BAA-1318; CCUG 52204), and the type strain of C. citroniae is RMA 16102 (ATCC BAA-1317; CCUG 52203).

Fluoroquinolones and Anaerobes

The usefulness of fluoroquinolones for the treatment of mixed aerobic and anaerobic infections has been investigated since these agents started being used in clinical practice. Newer compounds have increased in vitro activity against anaerobes, but clinically relevant susceptibility breakpoints for these bacteria have not been established. Pharmacodynamic analyses and corroboration by new data from clinical trials have enhanced our knowledge concerning the use of fluoroquinolones to treat selective anaerobic pathogens. These studies suggest that newer agents could be useful in the treatment of several types of mixed aerobic and anaerobic infections, including skin and soft-tissue, intra-abdominal, and respiratory infections. The major concerns with expanding the use of fluoroquinolones to treat anaerobic infections have been reports of increasing resistance in Bacteroides group isolates and the impact of these antibiotics on the incidence of Clostridium difficile-associated disease.

Clostridium clostridioforme: a mixture of three clinically important species

Clostridium clostridioforme shows much variability in phenotypic and antimicrobial susceptibility tests, suggesting it may be more than a single species even though all strains share unique morphology. This study was designed to determine if there are multiple species and, if so, to demonstrate the differences that exist between them. A total of 107 strains of C. clostridioforme were investigated by sequencing of the 16S rRNA gene, phenotypic studies, and antimicrobial susceptibility testing. In addition, clinical data from patients whose infections yielded an organism identified as C. clostridioforme was reviewed. Data from the above studies revealed three principal species in what has been called C. clostridioforme: Clostridium bolteae, C. clostridioforme, and Clostridium hathewayi. Each species may be distinguished by certain phenotypic tests. All three species were involved in infections, including bacteremia. C. clostridioforme appears to be associated with more serious or invasive human infections than the other two species in the group. Resistance to penicillin G is common and is due to beta-lactamase production. Resistance to clindamycin and moxifloxacin is also seen. The three species differ in terms of virulence and antimicrobial resistance. "C. clostridioforme" actually represents three distinct species that are different in terms of 16S rRNA sequences, phenotypic characteristics, and antimicrobial susceptibility. It is important for microbiology laboratories to distinguish between these species and for clinicians to be aware of the differences between them.

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.

Gatifloxacin, Gemifloxacin, and Moxifloxacin: The Role of 3 Newer Fluoroquinolones

Gatifloxacin, gemifloxacin, and moxifloxacin are the newest fluoroquinolones and show excellent in vitro activity against a wide variety of respiratory tract pathogens, many gram-negative aerobic organisms, and Bacteroides fragilis. These agents may be administered as oral and/or intravenous formulations with excellent bioavailability. The pharmacodynamics of these 3 new fluoroquinolones is more favorable than that of levofloxacin or ciprofloxacin for Streptococcus pneumoniae. All 3 agents are approved for the treatment of acute exacerbation of chronic bronchitis and community-acquired pneumonia. In addition, gatifloxacin and moxifloxacin are approved for the treatment of sinusitis. The toxicity of these 3 agents appears to be similar to that of the other fluoroquinolones in terms of gastrointestinal and central nervous system disturbances. All 3 agents have a low risk of phototoxicity, but gemifloxacin is associated with an increased risk of skin rash that is not a photoreaction. These agents can be useful for treatment of bacterial respiratory tract infections in patients who are allergic to beta-lactams, but caution must be exercised to avoid the potential for selection of widespread resistance, which may occur with indiscriminate use.

Gemifloxacin Mesylate

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Review of the in vitro activity and potential clinical efficacy of levofloxacin in the treatment of anaerobic infections

The activity of levofloxacin against aerobic bacteria has been well documented both in vitro and clinically, but its anaerobic activity has been infrequently studied. This new fluoroquinolone exhibits good in vitro activity (MIC(S) < or =2.0 microg/mL) against many anaerobic pathogens associated with acute sinusitis, bite wounds, and other soft-tissue infections. It is less active against Bacteroides fragilis (MIC (90)=2-4 microg/mL ) and has poor inhibitory activity against non-fragilis B. fragilis group species that are associated with gastrointestinal and genitourinary tract infections. Levofloxacin does not antagonize the in vitro activity of clindamycin and metronidazole and often provides additive or synergistic activity against anaerobic bacteria with these agents. In pharmacodynamic models, levofloxacin exhibits rapid bactericidal activity at 2-4 times the MIC of anaerobic bacteria. Prolonged killing is observed when the area-under-the concentration-time-curve to MIC ratio is greater than 40. In clinical efficacy trials, levofloxacin has been effective in the treatment of patients with gynecologic, skin and skin-structure, and bone infections involving anaerobic pathogens. Both micro-biologic and pharmacodynamic studies support further evaluations of levofloxacin in the treatment of selective mixed aerobic/anaerobic infections.

In vitro activity of 15 antimicrobial agents against clinical isolates of Clostridium difficile in Kuwait

A total of 73 clinical isolates of Clostridium difficile isolated from stool/rectal swabs of patients admitted to the intensive care units at Mubarak Hospital, Ibn Sina Hospital Burn unit and Haematology wards at the Kuwait Cancer Control Centre, were investigated for their susceptibility to 15 antibiotics using the Etest. Amoxycillin-clavulanic acid, ampicillin, meropenem, metronidazole, penicillin, piperacillin, piperacillin/tazobactam, teicoplanin and vancomycin had excellent activities with MIC(90)s of 0.38, 0.5, 1, 0.19, 1.5, 2, 3, 0.25 and 0.75 mg/l, respectively. Of the 73 C. difficile isolates, 86% were resistant to imipenem (MIC(90) >32 mg/l) and almost 97% were resistant to trovafloxacin (MIC(90)>256 mg/l). Forty eight percent of the isolates were resistant to clindamycin. A total of 18 isolates were highly clindamycin-resistant with an MIC of >256 mg/l; 10 of these were toxin producers. Multiple antibiotic resistance (two or more antibiotics) was noted in 63 isolates. These were more common among the toxigenic strains than the non-toxigenic strains by a ratio of 2.5:1.

Intra-abdominal anaerobic infections: bacteriology and therapeutic potential of newer antimicrobial carbapenem, fluoroquinolone, and desfluoroquinolone therapeutic agents

Intra-abdominal infections are biphasic, synergistic processes with early peritonitis and bacteremia due to aerobes and a later abscess component due to anaerobes. Although Bacteroides fragilis is the most commonly recognized pathogen, other anaerobes, including other members of the B. fragilis-group species, are major components of infection. Anaerobic bacteremia is often associated with an intra-abdominal source. New antimicrobial agents with anaerobic activity are in various stages of development for the therapy of intra-abdominal infections. The in vitro activity and the currently available sparse clinical data are reviewed for a new carbapenem (ertapenem), several fluoroquinolones (trovafloxacin, moxifloxacin, and gemifloxacin), and a desfluoroquinolone (BMS-284756).

A critical review of the fluoroquinolones: focus on respiratory infections

The new fluoroquinolones (clinafloxacin, gatifloxacin, gemifloxacin, grepafloxacin, levofloxacin, moxifloxacin, sitafloxacin, sparfloxacin and trovafloxacin) offer excellent activity against Gram-negative bacilli and improved Gram-positive activity (e.g. against Streptococcus pneumoniae and Staphylococcus aureus) over ciprofloxacin. Ciprofloxacin still maintains the best in vitro activity against Pseudomonas aeruginosa. Clinafloxacin, gatifloxacin, moxifloxacin, sitafloxacin, sparfloxacin and trovafloxacin display improved activity against anaerobes (e.g. Bacteroides fragilis) versus ciprofloxacin. All of the new fluoroquinolones display excellent bioavailability and have longer serum half-lives than ciprofloxacin allowing for once daily dose administration. Clinical trials comparing the new fluoroquinolones to each other or to standard therapy have demonstrated good efficacy in a variety of community-acquired respiratory infections (e.g. pneumonia, acute exacerbations of chronic bronchitis and acute sinusitis). Limited data suggest that the new fluoroquinolones as a class may lead to better outcomes in community-acquired pneumonia and acute exacerbations of chronic bronchitis versus comparators. Several of these agents have either been withdrawn from the market, had their use severely restricted because of adverse effects (clinafloxacin because of phototoxicity and hypoglycaemia; grepafloxacin because of prolongation of the QTc and resultant torsades de pointes; sparfloxacin because of phototoxicity; and trovafloxacin because of hepatotoxicity), or were discontinued during developmental phases. The remaining fluoroquinolones such as gatifloxacin, gemifloxacin, levofloxacin and moxifloxacin have adverse effect profiles similar to ciprofloxacin. Extensive post-marketing safety surveillance data (as are available with ciprofloxacin and levofloxacin) are required for all new fluoroquinolones before safety can be definitively established. Drug interactions are limited; however, all fluoroquinolones interact with metal ion containing drugs (eg. antacids). The new fluoroquinolones (gatifloxacin, gemifloxacin, levofloxacin and moxifloxacin) offer several advantages over ciprofloxacin and are emerging as important therapeutic agents in the treatment of community-acquired respiratory infections. Their broad spectrum of activity which includes respiratory pathogens such as penicillin and macrolide resistant S. pneumoniae, favourable pharmacokinetic parameters, good bacteriological and clinical efficacy will lead to growing use of these agents in the treatment of community-acquired pneumonia, acute exacerbations of chronic bronchitis and acute sinusitis. These agents may result in cost savings especially in situations where, because of their potent broad-spectrum activity and excellent bioavailability, they may be used orally in place of intravenous antibacterials. Prudent use of the new fluoroquinolones will be required to minimise the development of resistance to these agents.

In vitro activity of gemifloxacin compared to seven other oral antimicrobial agents against aerobic and anaerobic pathogens isolated from antral sinus puncture specimens from patients with sinusitis

Using a microbroth method for aerobes and agar dilution for anaerobes, we studied the comparative in vitro activity of gemifloxacin, three fluoroquinolones, two macrolides and two beta-lactams, against 207 aerobic and 162 anaerobic antral sinus puncture isolates. Gemifloxacin was active at < or = 0.25 ug/mL against 198/207 [96%] aerobes and 127/162 [78%] anaerobes or 325/369 [88%] of all isolates and was the most active quinolone on a weight basis against Gram-positive organisms. All Haemophilus and Moraxella species were susceptible to < or =0.06 ug/mL of gemifloxacin. Thirty-five anaerobic isolates [35/162, 22%] required > or =0.5 ug/mL of gemifloxacin for inhibition, including all Prevotella species [all except one strain of P. bivia were susceptible to < or = 2 ug/mL] and occasional strains of Bacteroides uniformis, Bacteroides fragilis, Bilophila wadsworthia, Peptostreptococcus magnus, Peptostreptococcus micros, Propionibacterium acnes, and Veillonella species. All fusobacteria were susceptible to < or =0.25 ug/mL of gemifloxacin. Based on our in vitro study results, we conclude that gemifloxacin may offer a therapeutic alternative for sinus infections.

Pharmacodynamics of trovafloxacin and levofloxacin against Bacteroides fragilis in an in vitro pharmacodynamic model

An in vitro pharmacodynamic investigation was conducted to explore whether the area under the concentration time curve from 0 to 24 h (AUC(0-24))/MIC ratio could predict fluoroquinolone performance against Bacteroides fragilis. An in vitro model was used to generate kill curves for trovafloxacin (TVA) and levofloxacin (LVX) at AUC(0-24)/MIC ratios of 1 to 406 against three strains of B. fragilis (ATCC 25285, ATCC 23745, and clinical isolate M97-117). TVA and LVX were bolused prior to the start of experiments to achieve the corresponding AUC(0-24)/MIC ratio. Experiments were performed in duplicate over 24 h and in an anaerobic environment. Analyses of antimicrobial performance were conducted by comparing the rates of bacterial kill (K) using nonlinear regression analysis with 95% confidence intervals. Statistical significance was defined as a lack of overlap in the 95% confidence limits generated from the slope of each kill curve. For both TVA and LVX, K was maximized once an AUC(0-24)/MIC ratio of > or =40 was achieved and was not further increased despite a 10-fold increase in AUC(0-24)/MIC from approximately 40 to 400 against all three strains of B. fragilis. No significant differences were found in K between AUC(0-24)/MIC ratios of approximately 40 to 200. In experiments where AUC(0-24)/MIC ratios that were > or = 5 and < or = 44 were conducted, 64% demonstrated regrowth at 24 h. Resistant strains were selected in 50% of those experiments, demonstrating regrowth, which resulted in increased MICs of two- to 16-fold for both TVA and LVX. Regrowth did not occur, nor were resistant strains selected in any studies with an AUC/MIC that was > 44. Our findings suggest that fluoroquinolones provide antibacterial effects against B. fragilis in a concentration-independent manner associated with an AUC(0-24)/MIC ratio of > or =40. Also, the potential for the selection of resistant strains of B. fragilis may increase with an AUC(0-24)/MIC ratio of < or =44.

Comparative in vitro activities of gemifloxacin, other quinolones, and nonquinolone antimicrobials against obligately anaerobic bacteria

The in vitro activity of gemifloxacin was compared to that of other quinolone and nonquinolone antimicrobials against 204 anaerobes by the agar dilution technique. The data indicate that gemifloxacin has a rather selective anaerobic activity. Most Peptostreptococcus, Porphyromonas, and Fusobacterium species are susceptible, while gemifloxacin's activity against other gram-negative anaerobes appears to be variable.

Evaluation of the clinical microbiology profile of moxifloxacin

Moxifloxacin is a new broad-spectrum antibacterial agent for treatment of respiratory tract infection of pathogens, including the major pathogens isolated in respiratory tract infections. The pharmacokinetic and pharmacodynamic properties of moxifloxacin are: excellent bioavailability, long half-life, and superior tissue penetration. Consequently, the 90% minimum inhibitory concentration (MIC(90)) values exhibited by moxifloxacin are generally lower than the concentrations of moxifloxacin found in circulation and in pulmonary tissues after a standard 400-mg dose given for up to 30 h. The relationship between moxifloxacin MIC(90) values and clinical response was investigated. The results of 13 clinical trials, performed in 30 countries between 1997 and 1998 and comprising 2618 patients treated with moxifloxacin or a comparator drug, were reviewed. Overall, 94% clinical success and 95% bacterial eradication was observed with moxifloxacin. These results were equivalent or superior to results seen with the comparator drugs. Clinical response rates and bacterial eradication rates with moxifloxacin were not significantly affected by bacterial resistance to other antibiotics (i.e., penicillin, clarithromycin, or amoxicillin). The majority (89%-97%) of the different bacterial strains with MICs for moxifloxacin < or =2 mg/L were successfully eradicated. In conclusion, moxifloxacin has potent in vivo bactericidal activity, and pathogen sensitivity to moxifloxacin is in accordance with US Food and Drug Administration and European suggested breakpoint values.

Clinical utility of the new fluoroquinolones for treating respiratory and urinary tract infections

Increasing antimicrobial resistance among most common urinary and respiratory tract pathogens has been the catalyst for the development of fluoroquinolones that are effective against these prevalent resistant organisms. Important attributes of the newly developed fluoroquinolones include once-daily dosing, maintained extensive tissue penetration and high oral bioavailability added to targeted antibacterial activities, all pharmacodynamic characteristics that may reduce the need for parenteral therapy or prevent patients being hospitalised. Some fluoroquinolones also offer same-dose bioequivalency between iv. and oral formulations, a feature that allows iv.-to-oral dosing (step-down or 'switch' therapy) without the need for dosage adjustments. These features suggest that the newer fluoroquinolones may be near-ideal agents for the empirical treatment of many common infections. This review discusses the efficacy and clinically relevant antimicrobial and pharmacokinetic qualities of the fluoroquinolones in comparison with other agents traditionally used to treat patients with urinary and respiratory tract infections.

Effects of single oral doses of gemifloxacin (320 milligrams) versus trovafloxacin (200 milligrams) on fecal flora in healthy volunteers

Gemifloxacin and trovafloxacin were administered to 12 volunteers in a randomized crossover trial with a 2-week washout period. Stool samples were collected predose and 1, 2, and 3 days postdose. Both quinolones reduced the number of organisms of the family Enterobacteriaceae and aerobic gram-positive organisms. Escherichia coli reduction was greater with gemifloxacin than with trovafloxacin, with postdose isolation of quinolone-resistant strains for which MICs of trovafloxacin were higher than those of gemifloxacin.

Anti-anaerobic activity of antibacterial agents

The first very effective bactericidal anti-anaerobic drug was metronidazole, introduced in clinical practice in the early 1980s. Sometimes penicillin G and chloramphenicol were used successfully in some anaerobic infections. However, this result was most likely due to Gram-positive anaerobic infections (e.g., Clostridium perfringens). Very rapidly, the anti-anaerobic armamentarium was extended with clindamycin, cefoxitin, imipenem and co-amoxyclav or piperacillin-tazobactam. The resistance rate to metronidazole and imipenem remains low but clindamycin has seen an importance decrease in bacterial susceptibility. New additional drugs could be very helpful to overcome resistance and adverse events. The novelties in this field are fluoroquinolones, which exhibit a good activity against Gram-positive cocci and anaerobes.

In vitro activity of gemifloxacin against contemporary clinical bacterial isolates from eleven North American medical centers, and assessment of disk diffusion test interpretive criteria

A total of 5499 contemporary clinical bacterial isolates were tested for susceptibility to gemifloxacin and four comparison agents by the broth microdilution method. Gemifloxacin activity against Enterobacteriaceae was generally comparable to that of ciprofloxacin and trovafloxacin, but because the gemifloxacin susceptible MIC breakpoint is lower, the percent susceptible to gemifloxacin was less than that to the other quinolones for some species. All agents were less active against Pseudomonas spp. Gemifloxacin was the most active agent tested against Gram-positive species, though Corynebacterium jeikeium and vancomycin-resistant enterococci were uniformly resistant to all agents tested. With staphylococci, a bimodal distribution of gemifloxacin MICs corresponded with susceptibility or resistance to ciprofloxacin. The significance of ciprofloxacin-resistant staphylococci that have susceptible gemifloxacin MICs is not known at this time. Disk diffusion tests were performed simultaneously with gemifloxacin and trovafloxacin as a control drug. Gemifloxacin MIC-zone diameter scattergrams indicated that interpretive discrepancy rates based on previously proposed criteria when using < or = 0.5 microg/ml as the susceptible MIC breakpoint was within acceptable limits. However, with the currently proposed MIC breakpoint of < or = 0.25 microg/ml, tentative zone diameter breakpoints of > or = 22 mm for susceptible, 19-21 mm for intermediate and < or = 18 mm for resistant are proposed.

The fluoroquinolone antibacterials: past, present and future perspectives

The history of the development of the quinolones is described from the first quinolone, nalidixic acid, via the first 6-fluorinated quinolone norfloxacin, to the latest extended-spectrum fluoroquinolones. The structural modifications made to the basic quinolone and naphthyridone nucleus and to the side chains have allowed improvements to be made such that the next group of fluoroquinolones after norfloxacin, exemplified by ciprofloxacin, had high activity against gram-negative species and a number of atypical pathogens, good-to-moderate activity against gram-positive species and were well absorbed and distributed. These compounds have been successfully used in the clinic for a decade and the size of the market has risen in recent years to only a little less than that for penicillins and macrolides. Notwithstanding the broad spectrum of these compounds, defects became evident. The growth in understanding of structure activity relationships with fluoroquinolones has enabled the development of even better compounds. The targets in fluoroquinolone research during the last few years include: improvements in pharmacokinetic properties, greater activity against gram-positive cocci and anaerobes, activity against fluoroquinolone-resistant strains, and improvements in activity against non-fermentative gram-negative species. The compounds developed in the recent years have fulfilled some but not all of these goals; improved bioavailability is one target achieved with most of the more recent compounds allowing for once-daily dosing. Gatifloxacin, moxifoxacin and trovafloxacin have all greatly improved the activity against gram-positive cocci, particularly pneumococci, and against anaerobes. They are not quite as active as ciprofloxacin against Enterobacteriaceae, and show no substantial improvements in activity against non-fermentative species. Clinafloxacin, gemifloxacin and sitafloxacin have even better activity against gram-positive cocci and are as active as ciprofloxacin against most gram-negatives, though gemifloxacin is less active than the other new compounds against gram-negative anaerobes. These three compounds do retain some activity against a number of ciprofloxacin-resistant species (gram-positive and gram-negative), but whether this activity will be adequate for clinical use is at present unclear. Both clinafloxacin and sitafloxacin contain a chloro substituent at position 8 of the quinolone nucleus. A halogen at this position in a number of compounds, though giving good activity, has also been associated with phototoxicity. Several fluoroquinolones have had to be withdrawn or strictly limited in their use post-marketing and in some cases no obvious relationship can be seen between the adverse effects and structural features, making this an area for urgent research.

Human necrobacillosis, with emphasis on Lemierre's syndrome

Lemierre's syndrome is the classical presentation of human necrobacillosis. It is characterized by a primary infection in the head in a young, previously healthy person who subsequently develops persistent high fever and disseminated metastatic abscesses, frequently including a septic thrombophlebitis of the internal jugular vein. The main pathogen is Fusobacterium necrophorum, an obligate anaerobic, pleomorphic, gram-negative rod. Clinical microbiologists have a key role in alerting clinicians and advising proper antibiotic treatment when the characteristic microscopic morphology of the pleomorphic F. necrophorum is seen in Gram stains from positive anaerobic cultures of blood and pus. Early diagnosis and prolonged appropriate antibiotic treatment with good anaerobic coverage are crucial to reduce morbidity and mortality. F. necrophorum also causes human necrobacillosis with foci caudal to the head, mainly in elderly patients with high mortality related to age and predisposing diseases, such as cancers of the primary focus.

Gemifloxacin

Gemifloxacin is a fluoroquinolone antibacterial agent which has an enhanced affinity for topoisomerase i.v.. It has potent activity against most Gram-positive bacteria, particularly Streptococcus pneumoniae. Gemifloxacin is over 30-fold more active than ciprofloxacin and 4- to 8-fold more active than moxifloxacin against this pathogen. Gemifloxacin has excellent activity against Haemophilus influenzae and Moraxella catarrhalis, and is unaffected by beta-lactamase production. It is generally 2-fold less active than ciprofloxacin against most Enterobacteriaceae. Atypical respiratory pathogens (Legionella, Mycoplasma and Chlamydia spp.) are highly susceptible to gemifloxacin. Preliminary results from phase II trials show that oral gemifloxacin 320 mg/day produced bacteriological responses of 94.7% in patients with acute exacerbations of chronic bronchitis and 95% of patients with uncomplicated urinary tract infections. Adverse events included nausea, abdominal pain, headache and mild rash in patients and healthy volunteers treated with gemifloxacin 320 mg/day. Gemifloxacin has a low potential for mild phototoxicity (comparable to that of ciprofloxacin).

Activities of gemifloxacin (SB 265805, LB20304) compared to those of other oral antimicrobial agents against unusual anaerobes

The activities of gemifloxacin (SB 265805, LB20304) and comparator agents were determined by an agar dilution method against 419 clinical strains of less-commonly identified species of anaerobes. Gemifloxacin was generally more active than trovafloxacin against gram-positive strains by one to two dilutions. Peptostreptococci (Peptostreptococcus asaccharolyticus, Peptostreptococcus magnus, Peptostreptococcus micros, and Peptostreptococcus prevotii) and Porphyromonas spp. (Porphyromonas asaccharolytica, Porphyromonas canoris, Porphyromonas gingivalis, and Porphyromonas macacae) were all susceptible to </=0.25 microgram of gemifloxacin per ml. The MICs of gemifloxacin at which 90% of the following strains were inhibited (MIC(90)s) were </=2 microgram/ml: Actinomyces israelii, Actinomyces odontolyticus, Clostridium innocuum, Clostridium clostridioforme, Anaerobiospirillum spp., Bacteroides tectum, Bacteroides ureolyticus, Bacteroides gracilis (now Campylobacter gracilis), Prevotella intermedia, Prevotella heparinolytica, and the Prevotella oris-buccae group. Fusobacterium naviforme and Fusobacterium necrophorum were also susceptible to </=2 microgram of gemifloxacin per ml, while Fusobacterium varium strains exhibited a bimodal pattern; the other Fusobacterium species, such as Fusobacterium ulcerans and Fusobacterium russii, as well as Veillonella spp., the Prevotella melaninogenica group, Prevotella bivia, Clostridium difficile, and Bilophila wadsworthia were relatively resistant to gemifloxacin (MIC(90)s, >/=4 microgram/ml).