In vitro susceptibilities of Bordetella pertussis and Bordetella parapertussis to six new oral cephalosporins

Pharmacotherapy for Bordetella pertussis infection. I. A synthesis of laboratory sciences

There is considerable history and practice experience both with laboratory susceptibility testing for Bordetella pertussis and clinical treatment. This two-part narrative review provides a synthesis of the laboratory and clinical sciences as they apply to this bacterium and the clinical consequences of treating infection. It is generally held that antibiotic susceptibility testing for B. pertussis is not sufficiently standardised, but there has not been an urgent need to consolidate the same given the lack global experience with major resistance profiles. Experience in China, however, has provided concern for high-level macrolide resistance. The nature of and frequency of such resistance has raised the bar for reconsideration of susceptibility testing given that first-line treatment may be regionally compromised. Disk diffusion and Etest susceptibility testing can be recommended for screening resistance among individual isolates of B. pertussis and on an ad hoc manner. Disk diffusion, Etest and/or critical agar dilution testing can be recommended for large-scale studies. Standards for inoculum, growth atmosphere, timing of interpretation, preferred testing media and controls can be extrapolated from the publications to date. Such methods should be able to detect high-level resistance to several antibiotics, but especially macrolides. Concern for intermediate-susceptible categories requires consideration as well as the correlation with bacteriological and clinical outcomes. Provisional standards can be applied at this time, and modification or fine-tuning of any such standards are open to future investigation.

Current pharmacotherapy of pertussis

Human infection with Bordetella pertussis and Bordetella parapertussis causes significant morbidity and mortality. While universal immunisation represents the mainstay of prevention, the purpose of this review is to summarise the current options for antimicrobial chemotherapy of pertussis. Several chemotherapeutic approaches have an important place in therapy and in infection control. Supportive treatment including nasopharyngeal suction, oxygen and parenteral fluids, is essential for infants < 1 year who are at greatest risk of complications and permanent sequelae. Steroids and beta2-agonists are also used in the management of severe neonatal pertussis. Several antibiotics have been shown to reduce the level of bacterial colonisation of the respiratory tract, however, erythromycin is accepted to be the treatment of choice. Erythromycin reduces severity and duration of disease, even if started during the paroxysmal phase. A 14 day course is recommended although side effects may limit compliance; a recent study indicates that a 7 day course may have similar efficacy in terms of eradication and prevention of relapse. Alternatives to erythromycin are clarithromycin, azithromycin and trimethoprim-sulfamethoxazole. Fluoroquinolones have good in vitro activity against both B. pertussis and B. parapertussis and may be useful in the treatment of adult patients with pertussis, although there are no supporting clinical data at present. Erythromycin prophylaxis is also recommended for close household contacts of patients with pertussis.

Ceftibuten: a new expanded-spectrum oral cephalosporin

OBJECTIVE

To review the antimicrobial activity, pharmacokinetics, clinical efficacy, and tolerability of ceftibuten, a new expanded-spectrum oral cephalosporin.

DATA SOURCES

Literature was identified by a MEDLINE search (January 1983-June 1996) of the medical literature, review of English-language literature and bibliographies of these articles, and data on file.

STUDY SELECTION

Clinical efficacy data were selected from all published and unpublished trials and abstracts that mentioned ceftibuten. Additional information concerning in vitro susceptibility, safety, chemistry, and pharmacokinetic profile of ceftibuten also was reviewed.

DATA SYNTHESIS

Ceftibuten, an oral expanded-spectrum cephalosporin, has a broad spectrum of activity against many gram-negative and selected gram-positive organisms, including Streptococcus pneumoniae, Streptococcus pyogenes, Moraxella catarrhalis, and Haemophilus influenzae. Ceftibuten is stable to hydrolysis by many common beta-lactamases. Ceftibuten is rapidly and almost completely absorbed from the gastrointestinal tract and is primarily eliminated renally as unchanged drug. The elimination half-life of ceftibuten is slightly longer than 2 hours. Efficacy has been demonstrated in a number of clinical trials in adults and children with upper and lower respiratory tract infections (e.g., acute otitis media, pharyngitis, sinusitis, bronchitis) and urinary tract infections. The adverse effect profile is equal to that of comparator agents.

CONCLUSIONS

Ceftibuten is an alternative to other antimicrobial agents with convenient once-daily dosing in the treatment of upper and lower respiratory tract infections. Similar to other oral expanded-spectrum cephalosporins, ceftibuten has antimicrobial activity against common pathogens of the respiratory tract and is stable in the presence of many beta-lactamases. The clinical choice of an oral expanded-spectrum cephalosporin will be based on patient acceptance, frequency of administration, and cost.

In vitro susceptibilities of Bordetella pertussis and Bordetella parapertussis to four fluoroquinolones (levofloxacin, d-ofloxacin, ofloxacin, and ciprofloxacin), cefpirome, and meropenem

The in vitro activities of levofloxacin, ofloxacin, d-ofloxacin, ciprofloxacin, cefpirome, and meropenem against 34 clinical isolates each of Bordetella pertussis and Bordetella parapertussis were determined by agar dilution on Mueller-Hinton agar supplemented with 5% horse blood. Levofloxacin was as active as ciprofloxacin against both species (MIC, 0.06 microgram/ml) and more active than ofloxacin and d-ofloxacin. Cefpirome was more active against B. pertussis (MIC, 1.0 microgram/ml) than against B. parapertussis (MIC, > 2 micrograms/ml), while the reverse was true for meropenem (MIC, 2.0 micrograms/ml against B. pertussis and 1.0 microgram/ml against B. parapertussis).

Comparison of media for agar dilution susceptibility testing of Bordetella pertussis and Bordetella parapertussis

Antimicrobial susceptibility testing of the fastidious species Bordetella pertussis and Bordetella parapertussis is not standardized. In an attempt to find the optimal medium for agar dilution testing, the activity of erythromycin against Bordetella pertussis and Bordetella parapertussis (34 isolates each) was assessed using homologous broth/agar combinations of Bordet-Gengou, charcoal, Iso-Sensitest (Oxoid) and Mueller-Hinton media. Each medium was supplemented with 5% and 20% whole defibrinated horse blood. Mueller-Hinton medium supplemented with 5% horse blood performed best overall.

Ceftibuten. A review of its antibacterial activity, pharmacokinetic properties and clinical efficacy

Ceftibuten is an orally active third generation cephalosporin which has a broad spectrum of in vitro antibacterial activity, encompassing the majority of Gram-negative pathogens and streptococci, and which shows greater stability than several other cephalosporins against bacteria producing extended-spectrum beta-lactamases. In clinical studies, ceftibuten (generally 400 mg/day in adults or 9 mg/kg/day in children, administered once daily) was effective in the treatment of acute uncomplicated or complicated urinary tract infections, demonstrating an efficacy similar to that of cefaclor (1500 mg/day), and similar or superior to that of cotrimoxazole (trimethoprim/sulfamethoxazole; 8/40 mg/kg/day) in children. The majority of patients with acute or chronic lower respiratory tract infections responded to treatment with ceftibuten, and response rates were similar to those achieved with cefaclor (750 or 1500 mg/day). Ceftibuten 9 mg/kg/day was at least as effective as cefaclor and as effective as amoxicillin/clavulanic acid (both 40 mg/kg/day) in children with acute otitis media, and was superior to phenoxymethylpenicillin (penicillin V; 25 mg/kg/day) in children and adolescents with streptococcal pharyngitis or scarlet fever caused by Group A beta-haemolytic streptococci. Ceftibuten was well tolerated in most patients, with adverse events (mostly mild to moderate gastrointestinal disturbances) generally occurring in 5 to 10% of patients. Thus, ceftibuten, with a once- or twice-daily oral dosage regimen, good tolerability profile and activity against a wide range of bacterial organisms, offers a promising alternative to other agents (including cefaclor, cotrimoxazole, amoxicillin/clavulanic acid, bacampicillin and phenoxymethylpenicillin) for the treatment of patients with urogenital and respiratory tract infections. Its place in therapy will be more clearly defined following further large comparative trials, in which it is likely to prove most useful in patients with infections caused by beta-lactamase-producing pathogens.

Ceftibuten pharmacokinetics and pharmacodynamics. Focus on paediatric use

Ceftibuten is an extended-spectrum, cephem antimicrobial agent formulated for oral administration. Ceftibuten is absorbed by carrier-mediated processes and passive diffusion. The absorption of ceftibuten is described adequately by a first-order process. Following oral administration, peak serum ceftibuten concentrations are reached within 2 to 3 hours. Although the absolute bioavailability of ceftibuten in humans is not known, its relative bioavailability indicates that there is relatively rapid and complete absorption of the drug. Administration of ceftibuten with food may decrease the rate of absorption and, in the case of high fat meals, may decrease the extent of absorption by approximately 20 to 30%. The results of limited studies indicate that the drug distributes well into various body tissues and fluids, with relatively high concentrations being achieved in organs that receive a significant portion of the cardiac output. In adults with normal renal function or chronic renal failure, the apparent volume of distribution (Vd/F) for ceftibuten ranges from 0.2 to 0.4 L/kg and the total plasma clearance (CL/F) ranges from approximately 61 to 75 ml/min (3.7 to 4.5 L/h). Studies of ceftibuten elimination in adults have demonstrated positive linear correlation between CL/F and creatinine clearance. Following administration of a single dose of ceftibuten, approximately 67 to 94% of the drug has been recovered in the urine unchanged. The elimination half-life (t1/2 beta) of ceftibuten in adults with normal renal function is approximately 2.5 hours. Significant accumulation of ceftibuten does not occur with repeated administration. Despite the fact that the mean time taken to achieve maximal serum concentration (tmax) [1.1 to 2 hours] and t1/2 beta (2.1 hours) following administration of a single dose of ceftibuten to infants and children were similar to values previously reported in adults, the Vd/F (0.42 L/kg) and CL/F (3.1 ml/h/kg) were considerably greater in children younger than 5 years. Additionally, the apparent nonrenal clearance of ceftibuten in paediatric patients (52% of CL/F) was greater than reported for adults (approximately 32% of CL/F) with normal renal function. Thus, developmental differences appear to affect the pharmacokinetic profile of ceftibuten. Ceftibuten has a wide spectrum of antimicrobial activity against both Gram-positive and Gram-negative pathogens, and is stable to hydrolysis by a large number of beta-lactamases. Notable exceptions with regard to the Gram-positive spectrum for ceftibuten include relative or documented resistance for most strains of Listeria, Staphylococcus aureus, S. epidermidis, penicillin-resistant strains of Streptococcus pneumonia and S. enterococcus.(ABSTRACT TRUNCATED AT 400 WORDS)

Loracarbef. A review of its antimicrobial activity, pharmacokinetic properties and therapeutic efficacy

Loracarbef is an orally administered member of a new synthetic class of beta-lactam antibiotics, the carbacephems, which is characterised by enhanced chemical stability. At low concentrations (< 2 mg/L) in vitro, it inhibits Streptococcus pneumoniae, S. pyogenes, beta-haemolytic streptococci groups B, C and G. Proteus mirabilis and Moraxella catarrhalis, including beta-lactamase-producing strains. At therapeutic plasma concentrations it is also active in vitro against most strains of Staphylococcus aureus, S. saprophyticus, Escherichia coli and beta-lactamase-positive and -negative strains of Haemophilus influenzae. Like other beta-lactams, loracarbef is inactive against methicillin-resistant strains of S. aureus. When administered at dosages of 200 to 400 mg twice daily, the clinical and bacteriological efficacy of loracarbef is comparable with that of amoxicillin and amoxicillin/clavulanic acid in patients with upper or lower respiratory tract infections, and comparable with that of cefaclor in treating infections of the lower respiratory tract, skin and skin structures and urinary tract. Loracarbef and phenoxymethylpenicillin (penicillin V) were equally effective in treating streptococcal pharyngitis and tonsillitis. Loracarbef is generally well tolerated by all age groups and causes less diarrhoea than amoxicillin/clavulanic acid. It is administered twice daily. It offers a suitable alternative to other orally administered antibiotics for the treatment of mild to moderate infections caused by susceptible organisms.

Cefetamet pivoxil. A review of its antibacterial activity, pharmacokinetic properties and therapeutic use

Cefetamet pivoxil is an oral third-generation cephalosporin which is hydrolysed to form the active agent, cefetamet. Cefetamet has excellent in vitro activity against the major respiratory pathogens Streptococcus pneumoniae, Haemophilus influenzae, Moraxella (Branhamella) catarrhalis and group A beta-haemolytic streptococci; it is active against beta-lactamase-producing strains of H. influenzae and M. catarrhalis, but has poor activity against penicillin-resistant S. pneumoniae. Cefetamet has marked activity against Neisseria gonorrhoeae and possesses a broad spectrum of activity against Enterobacteriaceae. Both staphylococci and Pseudomonas spp. are resistant to cefetamet. Cefetamet pivoxil has been investigated in the treatment of both upper and lower community-acquired respiratory tract infections and has demonstrated equivalent efficacy to a number of more established agents, namely cefaclor, amoxicillin and cefixime. In patients with group A beta-haemolytic streptococcal pharyngotonsillitis, a 7-day course of cefetamet pivoxil was as effective as a 10-day course of the standard agent, phenoxymethylpenicillin, in this indication. In complicated urinary tract infections, cefetamet pivoxil showed similar efficacy to cefadroxil, cefaclor and cefuroxime axetil. Cefetamet pivoxil was effective in the treatment of otitis media, pneumonia, pharyngotonsillitis and urinary tract infections in children. Preliminary data indicate that single dose cefetamet pivoxil can effectively eradicate N. gonorrhoeae from both men and women. Cefetamet pivoxil has a tolerability profile similar to that of other oral cephalosporins, with gastrointestinal effects being the most commonly reported adverse events. To date, no symptoms of carnitine deficiency have been reported with cefetamet pivoxil. Cefetamet pivoxil offers effective alternative oral therapy for outpatient treatment of community-acquired respiratory tract infections, with the advantage of improved activity against H. influenzae and increased beta-lactamase stability. However, its use in areas with a high incidence of penicillin-resistant S. pneumoniae is likely to be limited. Cefetamet pivoxil is also effective in the treatment of urinary tract infections, although further trials are required to define any comparative advantages over other oral agents.

Loracarbef: a new orally administered carbacephem antibiotic

OBJECTIVE

To discuss the in vitro activity, pharmacokinetics, clinical efficacy, adverse effects, and relative merits of loracarbef, a new orally administered carbacephem antibiotic.

DATA SOURCES

Pertinent literature was identified by a review of selected journals and a MEDLINE search. Additional information was provided by the manufacturer of loracarbef.

STUDY SELECTION

All studies that have evaluated the clinical efficacy of loracarbef were included. In vitro studies were included if they used similar methodologies. Additional information was incorporated regarding the chemistry, pharmacokinetics, and adverse effects of loracarbef.

DATA SYNTHESIS

Loracarbef has antibacterial activity against most community-acquired respiratory tract, skin and skin structure, and urinary tract pathogens. The drug is well absorbed after oral administration and plasma concentrations achieved in patients are greater than the in vitro minimum inhibitory concentrations for most of the above bacteria. Although the majority of the clinical studies with loracarbef have methodologic deficiencies, loracarbef therapy has demonstrated similar efficacy in the treatment of upper respiratory tract (except otitis media), lower respiratory tract, skin and skin-structure, and urinary tract infections compared with accepted antibiotics. Potential advantages of the new carbacephem may be improved patient compliance with its less frequent dosing schedule (once or twice a day, depending on the infection), and a low incidence of adverse effects.

CONCLUSIONS

Preliminary data indicate that loracarbef may be an alternative agent for the treatment of a variety of community-acquired infections. Additional clinical experience and rigorously controlled comparative clinical trials are necessary to enable practitioners to fully define the therapeutic role of loracarbef.

Cefprozil. A review of its antibacterial activity, pharmacokinetic properties, and therapeutic potential

Cefprozil is an orally active cephalosporin which has demonstrated activity against a wide range of organisms in vitro. It is particularly active against the Gram-positive organisms Streptococcus pyogenes, pneumoniae and agalactiae and against methicillin-susceptible Staphylococcus aureus. Strains of methicillin-resistant S. aureus are not susceptible to cefprozil. Cefprozil is also moderately active against Haemophilus influenzae, Moraxella catarrhalis, Neisseria gonorrhoeae, many Enterobacteriaceae and certain anaerobic organisms, and is relatively stable to hydrolysis by a number of beta-lactamases. In comparative trials, the clinical and bacteriological efficacy of cefprozil 500mg or 20 mg/kg administered once or twice daily has been comparable with multiple daily dosage regimens of erythromycin in patients with tonsillitis or pharyngitis, with cefaclor and amoxicillin/clavulanate in lower respiratory tract infections, with amoxicillin/clavulanate and erythromycin in skin and skin-structure infections and with cefaclor in acute uncomplicated urinary tract infections. The clinical efficacy of cefprozil is similar to that of cefaclor in patients with tonsillitis or pharyngitis but the bacteriological efficacy of cefprozil is significantly greater than that of cefaclor. Cefprozil is clinically more effective than cefuroxime axetil in the treatment of lower respiratory tract infections and demonstrated greater efficacy than cefaclor in one of 2 comparative studies when administered twice daily in patients with skin and skin-structure infections. In children with acute otitis media, cefprozil 15 mg/kg twice daily was as effective as cefaclor or amoxicillin/clavulanate 13.3 mg/kg 3 times daily and was as effective as cefixime 8 mg/kg once daily. The most frequently reported adverse effects associated with cefprozil, diarrhoea and nausea, are usually mild to moderate in severity and discontinuation of treatment is rarely necessary. Thus, cefprozil with its convenient administration regimen appears to be a suitable alternative to cefaclor, cefixime, amoxicillin/clavulanate or erythromycin for the treatment of upper and lower respiratory tract infections, skin and skin-structure infections, and otitis media in children. While cefprozil has shown similar efficacy to cefaclor in the treatment of uncomplicated urinary tract infections, well-controlled clinical trials comparing its efficacy with that of cotrimoxazole (trimethoprim+sulfamethoxazole) in this indication are required.

Current trends in bacterial respiratory pathogens

The relationship of virulence and antimicrobial susceptibility with morbidity due to bacterial respiratory pathogens is complex and evolving. Ultimately, decreasing the incidence of pneumonia due to bacterial pathogens will be dependent on successful preparation and distribution of effective vaccines. Until effective vaccines are widely available, control of a majority of respiratory infections will depend on promotion of rational therapeutic strategies. Though limited to a few specific serotypes and strains, changes in virulence of bacterial respiratory pathogens have been noted. Co-infections due to multiple respiratory pathogens may increase morbidity; however, the epidemiology of co-infections is not clear. Relationships between respiratory viruses and bacteria may exist that increase virulence of both agents, but information regarding these relationships awaits further investigation. Resistance of respiratory pathogens to the more commonly used antimicrobials, such as penicillin, erythromycin, chloramphenicol, and cotrimoxazole, is being documented globally with increasing frequency. The evolution of antimicrobic resistance, especially among strains of Streptococcus pneumoniae, the most common and deadly agent of lower respiratory tract infections, provides impetus to develop and promote effective pneumococcal vaccines and to search for new and effective antimicrobials.

Antibacterial activity of cefpodoxime in comparison with cefixime, cefdinir, cefetamet, ceftibuten, loracarbef, cefprozil, BAY 3522, cefuroxime, cefaclor and cefadroxil

The new oral cephalosporins cefpodoxime, cefixime, cefdinir, cefetamet and ceftibuten demonstrate enhanced activity against Enterobacteriaceae susceptible to the established compounds as well (e.g. cefuroxime, cefaclor, cefadroxil). In addition, cefpodoxime, cefixime, cefdinir, cefetamet and ceftibuten include in their spectrum species hitherto resistant to oral cephalosporins (Proteus vulgaris, Providencia spp., Yersinia enterocolitica). Besides, the majority of these compounds demonstrate relevant activity (MIC50 equal to or below 2 mg/l) against Enterobacter spp., Citrobacter freundii, Serratia spp. and Morganella morganii. Ceftibuten is the most potent oral cephalosporin against most of the Enterobacteriaceae. Non-fermentative bacilli (Acinetobacter spp., Pseudomonas spp.) remain completely resistant to oral cephalosporins (except some Acinetobacter species against cefdinir and Pseudomonas cepacia against ceftibuten). Antistaphylococcal activity for oral cephalosporins is highest for cefdinir followed by BAY 3522, cefprozil, cefuroxime and cefpodoxime. Loracarbef, cefaclor and cefadroxil are about equally active, while the other compounds are only weakly active (cefixime) or inactive (cefetamet, ceftibuten). Enterococci are insensitive to new generation oral cephalosporins as they have been to established compounds. The most active oral cephalosporins against hemolytic streptococci are cefdinir and cefprozil. Streptococcus pneumoniae, Streptococcus milleri and Streptococcus mitior are most susceptible to cefpodoxime, cefdinir, cefuroxime and BAY 3522. Penicillin resistant pneumococci have to be regarded as resistant to all oral cephalosporins. Fastidious pathogens like Haemophilus spp., Moraxella catarrhalis and Neisseria gonorrhoeae are more susceptible to cefpodoxime, cefixime, cefdinir, cefetamet and ceftibuten than to the other oral cephalosporins. The activity of oral cephalosporins is only weak against Listeria spp., Helicobacter pylori and anaerobic pathogens (except BAY 3522). Bordetella pertussis remains resistant to all absorbable cephalosporins. Progress in antibacterial activity of oral cephalosporins was mainly achieved by cefpodoxime, cefixime, cefdinir, cefetamet and ceftibuten against Enterobacteriaceae and the fastidious pathogens and against staphylococci and the nonenterococcal streptococci by cefdinir, BAY 3522, cefprozil and cefpodoxime.

In vitro susceptibilities of Bordetella pertussis and Bordetella parapertussis to seven fluoroquinolones

The in vitro susceptibilities of Bordetella pertussis and Bordetella parapertussis to seven fluoroquinolones were assessed by the agar dilution method. Ciprofloxacin and temafloxacin were the most active compounds (MIC for 90% of isolates tested [MIC90], 0.06 microgram/ml), while enoxacin and pefloxacin were the least active (MIC90, 0.5 microgram/ml). Fleroxacin, lomefloxacin, and ofloxacin showed intermediate activities (MIC90s, 0.125 to 0.25 microgram/ml). These results suggest a possible role for the fluoroquinolones in the treatment of pertussis, at least in adult patients.