Comparative in vitro activity and beta-lactamase stability of FK482, a new oral cephalosporin

The Chemical Relationship Among Beta-Lactam Antibiotics and Potential Impacts on Reactivity and Decomposition

Beta-lactam antibiotics remain one of the most commonly prescribed drug classes, but they are limited by their propensity to cause hypersensitivity reactions (e.g., from allergy to anaphylaxis) as well as by the emergence of bacteria with a myriad of resistance mechanisms such as β-lactamases. While development efforts continue to focus on overcoming resistance, there are ongoing concerns regarding cross-contamination of β-lactams during manufacturing and compounding of these drugs. Additionally, there is a need to reduce levels of drugs such as β-lactam antibiotics in waste-water to mitigate the risk of environmental exposure. To help address future development of effective remediation chemistries and processes, it is desired to better understand the structural relationship among the most common β-lactams. This study includes the creation of a class-wide structural ordering of the entire β-lactam series, including both United States Food and Drug Association (US-FDA)-approved drugs and experimental therapies. The result is a structural relational map: the "Lactamome," which positions each substance according to architecture and chemical end-group. We utilized a novel method to compare the structural relationships of β-lactam antibiotics among the radial cladogram and describe the positioning with respect to efficacy, resistance to hydrolysis, reported hypersensitivity, and Woodward height. The resulting classification scheme may help with the development of broad-spectrum treatments that reduce the risk of occupational exposure and negative environmental impacts, assist practitioners with avoiding adverse patient reactions, and help direct future drug research.

Oral cephalosporin and β-lactamase inhibitor combinations for ESBL-producing Enterobacteriaceae urinary tract infections

ESBL-producing Enterobacteriaceae as uropathogens have given rise to a sizeable amount of global morbidity. Community and hospital surveillance studies continue to report increasing proportions of these organisms as causes of urinary tract infection (UTI). Due to limited treatment options and the presence of cross-resistance amongst oral antibiotics of different classes, patients often require IV therapy, thereby increasing healthcare costs and reducing the effectiveness of delivering healthcare. Oral cephalosporin antibiotics are well known for their ability to achieve high urinary concentrations, in addition to achieving clinical success for treatment of uncomplicated UTI with a drug-susceptible pathogen. Novel cephalosporin/β-lactamase inhibitor combinations have been developed and demonstrate good in vitro activity against ESBL-producing isolates. A pooled analysis of in vitro activity of existing oral cephalosporin/clavulanate combinations in ESBL-producing Enterobacteriaceae has shown MIC50s of 0.5-1, 0.125-1 and 0.25 mg/L for cefpodoxime, ceftibuten and cefixime, respectively. A novel cyclic boronic acid β-lactamase inhibitor, QPX7728, was able to produce MIC50 values of 0.5 and ≤0.06 mg/L when paired with cefpodoxime and ceftibuten, respectively. Other novel combinations, cefpodoxime/ETX0282 and ceftibuten/VNRX7145, have also demonstrated excellent activity against ESBL producers. Clinical trials are now awaited.

Cefdinir: an oral cephalosporin for the treatment of respiratory tract infections and skin and skin structure infections

Cefdinir is an oral third-generation cephalosporin (also known as an advanced-spectrum or generation cephem) with good in vitro activity against the pathogens responsible for community-acquired respiratory tract infections and uncomplicated skin and skin structure infections. The drug distributes very well in respiratory tract tissues and fluids, as well as skin blisters and ear fluids; its pharmacokinetic profile allows once- or twice-daily administration. Oral cefdinir 300 mg twice daily or 600 mg once daily in adults and adolescents, or 14 mg/kg/day in one or two daily doses in pediatric patients, administered for 5 or 10 days, has shown good clinical and bacteriological efficacy, at least equivalent to that of other oral agents in randomized controlled trials conducted in patients with community-acquired pneumonia, acute bacterial exacerbation of chronic bronchitis, sinusitis, acute otitis media, pharyngitis and uncomplicated skin and skin structure infections. Cefdinir is well tolerated and the oral suspension has shown superior taste or palatability over other comparator oral antimicrobial agents. Thus, cefdinir continues to represent an important cephalosporin option for the treatment of adult, adolescent and pediatric patients with mild or moderate respiratory tract or cutaneous infections, especially in areas with elevated rates of beta-lactamase production in Haemophilus influenzae and where resistance to other commonly used agents has emerged (e.g., macrolides, penicillins, tetracyclines, fluoroquinolones and trimethoprim-sulfamethoxazole).

Cefdinir

Cefdinir is a third-generation oral cephalosporin antibiotic. Nomenclature, formulae, elemental analysis, and appearance of the drug are mentioned. The uses and applications and the several methods described for its preparation of the drug are outlined. The profile contains the physical characteristics including: pKa value, solubility, X-ray powder diffraction, melting point, and differential scanning calorimetry. The ultraviolet spectrum, vibrational spectrum, nuclear magnetic resonance ((1)H and (13)C NMR) spectra and the mass spectrum and fragmentation patterns of cefdinir together with the corresponding figures and/or tables are all produced. This profile includes the monographs of the Japanese pharmacopeia and the United States pharmacopeia. The several reported analytical methods that had been reported of the analysis of cefdinir include: spectrophotometric, polarographic, voltammetric, and chromatographic methods. The pharmacokinetics and stability of the drug are also provided. About 80 references are listed at end of this comprehensive profile.

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.

Contemporary evaluation of the in vitro activity and spectrum of cefdinir compared with other orally administered antimicrobials tested against common respiratory tract pathogens (2000-2002)

Cefdinir is an oral cephalosporin approved by the Food and Drug Administration in 1997 for the treatment of acute exacerbation of chronic bronchitis, pharyngitis-tonsillitis, community-acquired pneumonia, acute maxillary sinusitis, and uncomplicated skin and skin structure infections in adults and adolescents, and acute otitis media, pharyngitis-tonsillitis, and uncomplicated skin and skin structure infections in children. Although cefdinir showed similar activity to other cephalosporins in the early studies, very limited data has been generated over the last decade. In this report, we summarize the contemporary in vitro activity and spectrum of cefdinir in comparison to numerous other orally administrated antimicrobials available for treatment of community-acquired respiratory infections. A total of 8,326 non-duplicate recent clinical isolates, including Haemophilus influenzae (3,438), Moraxella catarrhalis (1,688), and Streptococcus pneumoniae (3,200), were collected from 35 medical centers in North America during 2000 through 2002, and susceptibility tested by reference broth microdilution methods. Pneumococcal susceptibility patterns for beta-lactams and macrolides were also analyzed according to the year of isolation and the age group of the patients. Cefdinir had the greatest activity against H. influenzae among the cephalosporins tested with susceptibility rates of 97.1 to 99.0%. All of the agents tested had complete or near complete activity against M. catarrhalis. Against S. pneumoniae, cefdinir and other cephalosporins showed similar susceptibility patterns, but improved rates were observed in 2002 (78.5-79.4%) when compared to the previous monitored period (71.8-74.5%). This increase in susceptibility was mainly because of a declining the occurrence of high-level penicillin resistance (MIC >/=2 microg/ml) across all age groups. Macrolide resistance also decreased among S. pneumoniae in 2002 when compared to 2000 through 2001; however, resistance to levofloxacin continued to increase from 0.9% in 2000 to 1.4% in 2002. These results indicate a significant change in emerging beta-lactam resistance patterns (including cefdinir) with a decrease possibly influenced by greater pneumococcal vaccine use in children and the elderly. These rates of increased susceptibility could sustain and enhance the clinical activity of orally administered beta-lactams such as cefdinir.

An alternative procedure for preparation of cefdinir

Cefdinir, a broad spectrum third-generation cephalosporin for oral administration, was prepared by the following synthetic pathway: synthesis of diphenylmethyl 7beta-amino-3-vinyl-3-cephem-4-carboxylate hydrochloride from 7-aminocephalosporanic acid (7-ACA), preparation of sodium 2-(2-tritylaminothiazol-4-yl)-(Z)-2-(tritylhydroxyimino) acetate from ethyl acetoacetate, coupling of both intermediaries to obtain diphenylmethyl 7beta-[2-(2-tritylaminothiazol-4-yl)-(Z)-2-tritylhydroxyimino-3-vinyl-3-cephem-4-carboxylate and final cleavage of trityl and diphenylmethyl protective groups. This procedure allows to obtain better yields of cefdinir and to avoid the use of diketene during the synthesis of this antibiotic by the previously reported method.

Cefdinir: an advanced-generation, broad-spectrum oral cephalosporin

BACKGROUND

Cefdinir is an advanced-generation, broad-spectrum cephalosporin antimicrobial agent that has been approved for the treatment of community-acquired pneumonia, acute bacterial exacerbations of chronic bronchitis, acute maxillary sinusitis, pharyngitis/tonsillitis, acute bacterial otitis media, and uncomplicated skin and skin-structure infections in adult and pediatric patients.

OBJECTIVE

The purpose of this article was to review the in vitro antimicrobial activity, pharmacokinetics, clinical efficacy, safety, and potential role of cefdinir.

METHODS

Studies were identified by a MEDLINE search (January 1983-September 2001) of the English-language medical literature, a review of identified articles and their bibliographies, and a review of data on file with the manufacturer. Clinical efficacy data were selected from all published trials mentioning cefdinir. Information concerning in vitro susceptibility, safety, chemistry, and the pharmacokinetic profile of cefdinir also was reviewed.

RESULTS

Cefdinir has a broad spectrum of activity against many gram-negative and gram-positive aerobic organisms, including Streptococcus pneumoniae, Staphylococcus aureus, Streptococcus pyogenes, Haemophilus influenzae, and Moraxella catarrhalis. Cefdinir is stable to hydrolysis by 13 of the common beta-lactamases. It is rapidly absorbed from the gastrointestinal tract (mean time to peak plasma concentration, 3 hours) and is almost entirely eliminated via renal clearance of unchanged drug. The terminal disposition half-life of cefdinir is approximately 1.5 hours. Efficacy has been demonstrated in 19 clinical trials in adults and children with upper and lower respiratory tract infections (eg, pharyngitis, sinusitis, acute otitis media, acute bronchitis, acute bacterial exacerbation of chronic bronchitis, community-acquired pneumonia), and skin and skin-structure infections. The adverse-event profile is similar to that of comparator agents, although in 4 adult and adolescent studies and 1 adult study, diarrhea occurred significantly more frequently in cefdinir recipients than in recipients of penicillin V, cephalexin, cefaclor, and cefprozil.

CONCLUSIONS

Cefdinir is an alternative to other antimicrobial agents and can be dosed once or twice daily for the treatment of upper and lower respiratory tract infections and skin and skin-structure infections. Similar to other oral expanded-spectrum cephalosporins, cefdinir has activity against common pathogens of the respiratory tract and skin and is stable in the presence of selected beta-lactamases. The clinical choice of an oral expanded-spectrum cephalosporin will be based on patient acceptance, frequency of administration, and cost.

Cefdinir: an expanded-spectrum oral cephalosporin

OBJECTIVE

To review the antimicrobial activity, pharmacokinetics, clinical efficacy, and tolerability of cefdinir, an expanded-spectrum oral cephalosporin.

DATA SOURCES

Literature was identified by a MEDLINE search (January 1983-November 1999) of the medical literature, review of English-language literature and bibliographies of these articles, and product information.

STUDY SELECTION

Clinical efficacy data were selected from all published trials mentioning cefdinir. Additional information concerning in vitro susceptibility, safety, chemistry, and pharmacokinetic profile of cefdinir was also reviewed.

DATA SYNTHESIS

Cefdinir, an oral expanded-spectrum cephalosporin, has a broad spectrum of activity against many gram-negative and -positive aerobic organisms, including Streptococcus pneumoniae, Staphylococcus aureus, Streptococcus pyogenes, Haemophilus influenzae, and Moraxella catarrhalis. Cefdinir is stable to hydrolysis by many common beta-lactamases. Cefdinir is rapidly absorbed from the gastrointestinal tract and is primarily eliminated via renal clearance of unchanged drug. The terminal disposition half-life of cefdinir is approximately 1.5 hours. Efficacy has been demonstrated in a number of clinical trials in adults and children with upper and lower respiratory tract infections (e.g., pharyngitis, sinusitis, acute otitis media, acute bronchitis, acute exacerbation of chronic bronchitis, community-acquired pneumonia) and skin and skin-structure infections. The adverse event profile is similar to that of comparator agents.

CONCLUSIONS

Cefdinir is a second-line alternative to first-line antimicrobial agents, with convenient once- or twice-daily dosing in the treatment of upper and lower respiratory tract infections and skin and skin-structure infections. Similar to other oral expanded-spectrum cephalosporins, cefdinir has activity against common pathogens of the respiratory tract and skin 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.

Pharmacodynamics and pharmacokinetics of cefdinir, an oral extended spectrum cephalosporin

BACKGROUND

Oral second and third generation cephalosporins are undergoing continuing research and development in the arena of pediatric infectious disease in an attempt to fill voids created by existing agents in the quest for the "ideal" antimicrobial. This paper reviews the in vitro antimicrobial activity (pharmacodynamics) and pharmacokinetics of cefdinir, an extended spectrum oral cephalosporin, with an emphasis on those aspects relevant to the pediatric patient population.

METHODS

A MEDLINE literature search was conducted for the years 1985 through 2000, identifying all English language papers examining the in vitro antimicrobial activity and human pharmacokinetics of cefdinir. Bibliographies of these papers were reviewed, as were relevant data on file with the manufacturer.

DATA SYNTHESIS

Cefdinir exhibits broad range in vitro activity against Gram-positive and Gram-negative aerobes. It exhibits superior activity against Gram-positive aerobes, compared with drugs like cefixime, ceftibuten, cefuroxime and cefpodoxime. In addition it is stable to hydrolysis by many of the common betalactamases. The pharmacokinetic parameters of cefdinir in children are similar to those obtained in adults using similar milligram per m2 doses (300, 600 mg in adults = 7, 14 mg/kg in children, respectively).

CONCLUSIONS

The pharmacodynamic and pharmacokinetic characteristics of cefdinir as described in this paper, as well as the results of the clinical trials program, support the use of this agent in the treatment of a wide variety of pediatric infectious diseases.

The new antibiotics

It is easy to become overwhelmed by the amount of information available on the new antibiotics and difficult to keep abreast of the appropriate indications for each of them. For most patients with community-acquired infections, the first-line agent is usually not one of the newer agents, but a standard regimen, or at times, no antibiotic at all. The development of resistance is likely to parallel the extent to which these agents are prescribed. They should be used only when standard treatment fails, when compliance with treatment is a real and serious issue, or when the patient has a real allergic reaction to the standard regimen.

Cefdinir versus cefaclor in the treatment of uncomplicated urinary tract infection

OBJECTIVE

This multicenter, double-blind, randomized, parallel-group study was conducted in Europe, South Africa, and Australia to compare the clinical and microbiologic efficacy and the tolerability of a cephalosporin antibiotic, cefdinir, with those of cefaclor in the treatment of uncomplicated urinary tract infection.

METHODS

Patients were randomized in a 1:1 ratio to 5 days of treatment with either cefdinir 100 mg BID or cefaclor 250 mg TID.

RESULTS

A total of 661 patients were randomized to treatment. They were 90% female, with a median age of 44 years. There were no clinically important differences between groups in terms of demographic characteristics or symptoms on admission. The most frequently isolated pathogens in admission urine cultures were Escherichia coli (383 patients), Proteus mirabilis (20 patients), Staphylococcus saprophyticus (14 patients), and Klebsiella pneumoniae (9 patients). Of the admission pathogens with documented susceptibility results, significantly more were resistant to cefaclor (6.7%) than to cefdinir (3.7%; P < 0.003). Significantly more admission isolates of E. coli were resistant to cefaclor (5.1%) than to cefdinir (2.0%; P < 0.007). A total of 383 patients were assessable for efficacy, 196 in the cefdinir group and 187 in the cefaclor group. Clinical cure rates and microbiologic response rates for cefdinir and cefaclor were statistically equivalent at 5 to 9 days posttherapy (test-of-cure visit), using a 95% CI approach. The rate of treatment-related adverse events was higher in cefdinir-treated patients (20.2%) than in cefaclor-treated patients (13.0%; P = 0.025), mainly due to the greater frequency of diarrhea in the former group. However, only 4 patients (1.2%) discontinued cefdinir treatment due to diarrhea.

CONCLUSION

Empiric therapy with cefdinir appears to be a reasonable choice for patients with uncomplicated urinary tract infection in whom cephalosporin treatment is indicated.

Comparison of cefdinir and penicillin for the treatment of streptococcal pharyngitis. Cefdinir Pharyngitis Study Group

Cefdinir, an oral cephalosporin active against Streptococcus pyogenes (group A beta-hemolytic streptococci [GABHS]), is also resistant to degradation by most oropharyngeal beta-lactamases. This multicenter, randomized, controlled, double-masked study assessed the tolerability and efficacy of 2 dosing regimens of cefdinir in the treatment of pharyngitis due to GABHS. Adults and adolescents with pharyngitis due to GABHS received cefdinir 600 mg QD, cefdinir 300 mg BID, or penicillin V 250 mg QID each for 10 days. A throat culture and clinical assessment were obtained 4 to 9 days after completion of therapy. Of 919 patients enrolled, 644 (70.1%) were microbiologically assessable. The eradication rates 4 to 9 days after completion of therapy were 91.4% in the cefdinir QD group, 91.7% in the cefdinir BID group, and 83.4% in the penicillin group (P = 0.02 for cefdinir QD vs penicillin, P = 0.01 for cefdinir BID vs penicillin, P = 0.95 for cefdinir QD vs cefdinir BID). Clinical cure rates were also superior with cefdinir QD (94.8%, P = 0.02) and cefdinir BID (96.3%, P < 0.01) compared with penicillin (88.9%). Diarrhea was more common in the cefdinir groups (P < 0.001). Seventeen cefdinir patients and 4 penicillin patients discontinued therapy because of adverse reaction (P = 0.13). Ten days of treatment for streptococcal pharyngitis with cefdinir QD or BID is superior to treatment with penicillin V for the eradication of GABHS from the pharynx, although it is associated with a higher rate of adverse reactions.

Comparison of cefdinir and penicillin for the treatment of pediatric streptococcal pharyngitis

This multicenter, randomized, controlled, investigator-masked study was performed to assess the efficacy and tolerability of cefdinir for the treatment of streptococcal pharyngitis. Children aged 1 through 12 years with signs and symptoms of pharyngitis and a positive result on a rapid screening test for Streptococcus pyogenes were randomly assigned to receive cefdinir 14 mg/kg QD, cefdinir 7 mg/kg BID, or penicillin V 10 mg/kg 4 times daily for 10 days. Seven hundred ninety-two patients were enrolled, and 682 were clinically and microbiologically assessable. All treatment groups had similar demographic characteristics (-50.0% male, predominantly white, median age 7 years). The eradication rates of S pyogenes, determined 4 to 9 days after completion of therapy, were 94.3% in the cefdinir QD group, 94.3% in the cefdinir BID group, and 70.0% in the penicillin V group (95% confidence interval [CI] 17.6%-30.9%, P < 0.001 for cefdinir QD vs penicillin; CI 17.5%-30.9%, P < 0.001 for cefdinir BID vs penicillin). Clinical cure rates were 97.4%, 96.0%, and 86.3% for the cefdinir QD, cefdinir BID, and penicillin groups, respectively (CI 6.1%-15.9%, P = 0.001 for cefdinir QD vs penicillin; CI 4.6%-14.8%, P = 0.001 for cefdinir BID vs penicillin). Adverse reactions occurred in 8.3%, 8.7%, and 7.6% of cefdinir QD, cefdinir BID, and penicillin patients, respectively (P = NS). Treatment with cefdinir, either QD or BID, was associated with higher eradication rates of S pyogenes and higher clinical cure rates. Both cefdinir and penicillin were well tolerated. Three patients, 1 receiving cefdinir BID and 2 receiving penicillin, discontinued the study drug because of adverse reactions.

Five-day cefdinir treatment for streptococcal pharyngitis. Cefdinir Pharyngitis Study Group

A multicenter, randomized, controlled, investigator-blind study was performed to evaluate the safety and efficacy of oral cefdinir versus oral penicillin V for the treatment of pharyngitis due to group A beta-hemolytic streptococci (GABHS). Patients 13 years of age and older were randomized to receive either oral cefdinir (300 mg twice a day) for 5 days followed by placebo for 5 days or oral penicillin V (250 mg four times a day) for 10 days. Throat cultures were obtained, and signs and symptoms of pharyngitis were recorded at study admission and follow-up visits on study days 11 to 15, 16 to 20, and 25 to 31. Patients kept a diary to record medication intake and their assessment of throat pain at admission and at each day of study treatment. Five hundred fifty-eight patients were enrolled, of whom 432 (77.4%) were clinically and microbiologically evaluable. The GABHS eradication rates 5 to 10 days after completion of therapy were 193 of 218 (88.5%) in the cefdinir group and 176 of 214 (82.2%) in the penicillin group (P = 0.053). Clinical cure rates were 89.0 and 84.6%, respectively (P = 0.80). By the time of the long-term follow-up visit, 2 to 3 weeks after completion of treatment, 156 of 191 (81.7%) of the assessable cefdinir patients and 152 of 195 (77.9%) of the penicillin patients remained free of GABHS. Both treatments were well tolerated, with adverse reaction rates of 18.3% in the cefdinir study arm and 15.0% in the penicillin study arm (P = 0.278). Five-day treatment with cefdinir is safe and effective therapy for GABHS pharyngitis. Based on its twice-a-day dosage and shorter course of therapy, leading to potentially greater patient compliance, cefdinir may be considered for use in the treatment of pharyngitis caused by GABHS.

Cefdinir versus cephalexin for the treatment of skin and skin-structure infections. The Cefdinir Adult Skin Infection Study Group

Because of increasing resistance to older antimicrobial agents, newer drugs need to be evaluated for the treatment of skin and skin-structure infections (SSSIs). This double-masked, randomized, comparative, multicenter study enrolled patients aged 13 years or older with SSSIs to receive either cefdinir 300 mg BID or cephalexin 500 mg QID for 10 days. Nine hundred fifty-two patients (474 in the cefdinir group and 478 in the cephalexin group) took part, primarily white males between 18 and 65 years of age. There were two follow-up visits, with efficacy determined at the test-of-cure visit, 7 to 16 days posttherapy. Many patients were not microbiologically assessable, primarily because of negative cultures at study admission. Patients who required surgical intervention (e.g., incision and drainage) at the site of infection more than 24 hours after the initiation of drug therapy were defined as treatment failures. Significantly more isolated pathogens were resistant to cephalexin than to cefdinir. In the 178 efficacy-assessable cefdinir-treated patients, the rate of pathogen eradication was 93% (200/215), and the rate of successful clinical response was 88% (157/178), compared with 89% (221/247) and 87% (177/204), respectively, in the 204 efficacy-assessable cephalexin-treated patients. Using confidence-interval analysis, the microbiologic and clinical response rates of the cefdinir-treated patients were statistically equivalent to those of the cephalexin-treated patients. At the follow-up visits, patients were questioned about any adverse events occurring since their previous visit. Any untoward symptom occurring during or within 2 days after completion of drug treatment was considered an adverse reaction if the investigator judged it to be definitely, probably, or possibly related to the study drug. One hundred twenty-three (26%) cefdinir-treated patients and 77 (16%) cephalexin-treated patients experienced at least one adverse reaction, a statistically significant difference. Study drug was discontinued for adverse reactions in 20 (4%) cefdinir-treated patients and 13 (3%) cephalexin-treated patients; in the two groups, 10 and 7 patients, respectively, were discontinued for diarrhea. Cefdinir taken BID was as effective as cephalexin taken QID in the treatment of mild-to-moderate SSSIs and was well tolerated by most patients. The increased antibacterial activity of cefdinir must be balanced against the higher rate of diarrhea seen in patients treated with this drug.

Efficacy of CS-834 against experimental pneumonia caused by penicillin-susceptible and -resistant Streptococcus pneumoniae in mice

The efficacy of CS-834, a novel oral carbapenem, was assessed by using a murine model of pneumonia caused by penicillin-susceptible and penicillin-resistant Streptococcus pneumoniae and was compared with those of oral cephems, i.e., cefteram pivoxil, cefpodoxime proxetil, cefdinir, and cefditoren pivoxil. Intranasal inoculation of 10(6) CFU of penicillin-susceptible or penicillin-resistant S. pneumoniae in the exponential growth phase induced pneumonia and bacteremia in ddY mice within 48 h. For the treatment of infections caused by the penicillin-susceptible strain the antibiotics were administered orally at 0.4, 2, and 10 mg/kg of body weight twice daily for 2 days beginning at 24 h after bacterial inoculation, and for the treatment of infections caused by a penicillin-resistant strain the antibiotics were administered at 2, 10, and 50 mg/kg twice daily for 2 days beginning at 24 h after bacterial inoculation. Among the antibiotics tested, CS-834 exhibited the most potent efficacy against both types of strains. Against infections caused by penicillin-susceptible S. pneumoniae, CS-834 at all doses significantly reduced the numbers of viable cells in both the lungs and blood. Cefpodoxime proxetil at all doses and cefteram pivoxil and cefditoren pivoxil at doses of 2 and 10 mg/kg showed comparable efficacies. Against infections caused by penicillin-resistant S. pneumoniae, CS-834 at doses of 10 and 50 mg/kg showed the most potent efficacy among the antibiotics tested, resulting in the maximum decrease in the numbers of viable cells in the lungs. Comparable efficacies were observed with cefteram pivoxil and cefpodoxime proxetil at doses of 50 mg/kg each. The concentration of CS-834 in the lungs and blood was higher than that of cefdinir and was lower than those of the other antibiotics tested, suggesting that the potent therapeutic efficacy of CS-834 reflects its strong activity against S. pneumoniae.

In vitro and in vivo antibacterial activities of CS-834, a novel oral carbapenem

CS-834 is a novel oral carbapenem antibiotic. This compound is an ester-type prodrug of the active metabolite R-95867. The antibacterial activity of R-95867 was tested against 1,323 clinical isolates of 35 species and was compared with those of oral cephems, i.e., cefteram, cefpodoxime, cefdinir, and cefditoren, and that of a parenteral carbapenem, imipenem. R-95867 exhibited a broad spectrum of activity covering both gram-positive and -negative aerobes and anaerobes. Its activity was superior to those of the other compounds tested against most of the bacterial species tested. R-95867 showed potent antibacterial activity against clinically significant pathogens: methicillin-susceptible Staphylococcus aureus including ofloxacin-resistant strains, Streptococcus pneumoniae including penicillin-resistant strains, Clostridium perfringens, Neisseria spp., Moraxella catarrhalis, most members of the family Enterobacteriaceae, and Haemophilus influenzae (MIC at which 90% of strains are inhibited, < or =0.006 to 0.78 microg/ml). R-95867 was quite stable to hydrolysis by most of the beta-lactamases tested except the metallo-beta-lactamases from Stenotrophomonas maltophilia and Bacteroides fragilis. R-95867 showed potent bactericidal activity against S. aureus and Escherichia coli. Penicillin-binding proteins 1 and 4 of S. aureus and 1Bs, 2, 3, and 4 of E. coli had high affinities for R-95867. The in vivo efficacy of CS-834 was evaluated in murine systemic infections caused by 16 strains of gram-positive and -negative pathogens. The efficacy of CS-834 was in many cases superior to those of cefteram pivoxil, cefpodoxime proxetil, cefdinir, and cefditoren pivoxil, especially against infections caused by S. aureus, penicillin-resistant S. pneumoniae, E. coli, Citrobacter freundii, and Proteus vulgaris. Among the drugs tested, CS-834 showed the highest efficacy against experimental pneumonia in mice caused by penicillin-resistant S. pneumoniae.

Antimicrobial activity of DU-6681a, a parent compound of novel oral carbapenem DZ-2640

The in vitro antibacterial activity of DU-6681a, a parent compound of DZ-2640, against gram-positive and -negative bacteria was compared with those of penems and cephalosporins currently available. MICs at which 90% of the isolates are inhibited (MIC90s) of the compound for clinical isolates of methicillin-susceptible and -resistant Staphylococcus aureus and Staphylococcus epidermidis, including methicillin-susceptible and -resistant strains, were 0.10, 25, and 12.5 microg/ml, respectively. DU-6681a inhibited the growth of all strains of Streptococcus pyogenes and of penicillin-susceptible and -insusceptible Streptococcus pneumoniae at 0.006, 0.025, and 0.20 microg/ml, respectively, and MIC90s of the compound were 6.25 and >100 microg/ml for Enterococcus faecalis and Enterococcus faecium, respectively. MIC90s of DU-6681a were 0.20, 0.10, and 0.025 microg/ml for Haemophilus influenzae, Moraxella catarrhalis, and Neisseria gonorrhoeae, respectively. For Pseudomonas aeruginosa, the MIC50 and MIC90 of DU-6681a were 25 and 50 microg/ml, respectively. DU-6681a activity was not affected by different media, varied inoculum size (10(4) to 10(7) CFU), or the addition of human serum but was decreased under acidic conditions against gram-negative bacteria, under alkaline conditions against gram-positive bacteria, and in human urine, as was the activity of the other antibiotics tested. The frequency of spontaneous resistance to DU-6681a was less than or equal to those of the reference compounds. Time-kill curve studies demonstrated the bactericidal action of DU-6681a against S. aureus, S. pneumoniae, Escherichia coli, and H. influenzae.

Study of use of cefdinir versus cephalexin for treatment of skin infections in pediatric patients. The Cefdinir Pediatric Skin Infection Study Group

Three hundred ninety-four patients, aged 6 months to 12 years, entered a multicenter, randomized, controlled, investigator-blind study comparing cefdinir, 7 mg/kg of body weight twice a day, with cephalexin, 10 mg/kg four times a day, each given for 10 days. The most common infections treated were impetigo and secondary infection of preexisting dermatitis. The most common pathogens isolated were Staphylococcus aureus and Streptococcus pyogenes. Two hundred thirty-one patients were microbiologically evaluable. Microbiologic eradication rates were 164 of 165 pathogens (99.4%) in the cefdinir group and 152 of 156 pathogens (97.4%) in the cephalexin group (P = 0.14). Clinical cure rates were 116 of 118 patients (98.3%) in the cefdinir group and 106 of 113 patients (93.8%) in the cephalexin group (P = 0.056). Sixteen percent of cefdinir patients and 11% of cephalexin patients experienced adverse events (P = 0.11), the most common being diarrhea, which affected 8% of the cefdinir group and 4% of the cephalexin group. Cefdinir appears to be an effective and well-tolerated agent for the treatment of uncomplicated skin and skin structure infections in pediatric patients.

In vitro activity of cefdinir against respiratory pathogens isolated in Sicily with reference to beta-lactamase production

The in vitro activity of cefdinir (CI-983, FK-482), an orally absorbed aminothiazolyl cephalosporin, was evaluated against all 287 strains of Haemophilus influenzae, Haemophilus parainfluenzae, Moraxella catarrhalis, Streptococcus pneumoniae and Streptococcus pyogenes in comparison with cefaclor, cefuroxime, amoxicillin, amoxicillin-clavulanic acid, erythromycin and cotrimoxazole. The bactericidal activity of cefdinir, cotrimoxazole, amoxicillin-clavulanic acid and erythromycin was determined against H. influenzae, M. catarrhalis and S. pneumoniae. With the exception of one beta-lactamase negative ampicillin-resistant strain of H. influenzae (resistant to all antibiotics tested), no resistance to cefdinir was observed (MIC < or = 1 mg/l). Cefdinir was active against H. influenzae, H. parainfluenzae and M. catarrhalis regardless of whether or not they produced beta-lactamase. In general, the inhibitory concentrations of cefdinir against H. influenzae, H. parainfluenzae and M. catarrhalis were similar to those of amoxicillin/clavulanic acid, one or two dilutions lower than those of cefuroxime and four dilutions lower than those of cefaclor and cotrimoxazole. Against S. pneumoniae and S. pyogenes cefdinir had the same activity as cefuroxime and amoxicillin but was more effective than the other antibiotics tested. Kinetic studies showed that cefdinir was rapidly bactericidal at concentrations 2 and 4 times the minimum inhibitory concentration (MIC): a reduction of 99.9% in CFU values was generally observed after 6-8 h.

In vitro and in vivo antibacterial activities of S-1090, a new oral cephalosporin

S-1090, a new oral cephalosporin, was active against selected gram-negative bacteria and methicillin-susceptible clinical isolates of Staphylococcus aureus, Staphylococcus epidermidis, and Staphylococcus warneri, against which it had excellent activity. S-1090 was the most active compound against Streptococcus pyogenes and Streptococcus agalactiae among the agents compared. The in vivo efficacy of S-1090 against systemic and urinary and respiratory tract infections caused by gram-positive and -negative bacteria was superior to that expected from the in vitro and in vivo activities of the agents against which it was compared.

Suction-induced blister fluid penetration of cefdinir in healthy volunteers following ascending oral doses

The pharmacokinetics and suction-induced blister fluid penetration of cefdinir following single oral administrations of 200, 300, 400, and 600 mg were studied in 16 healthy young male volunteers according to a Latin square design. Plasma, blister, and urine samples were assayed by high-pressure liquid chromatography. We observed a nonlinear relationship (P = 0.02) between the dose and the maximum concentration in plasma as well as between the dose and the area under the concentration-time curve (AUC) in plasma (P < 0.001), which may be indicative of a limited absorption process. This resulted in a lower AUC value than expected as well as a smaller fraction of cefdinir excreted unchanged at a dose of 600 mg. Renal clearance decreased with increasing doses (P < 0.006; analysis of variance with the Latin square design and Games-Howell procedure). Maximal cefdinir concentrations in blister fluid were delayed compared with concentrations in plasma. Blister fluid penetration measured by the ratio of the AUC in blister fluid to the AUC in plasma was extensive (92.4 to 108.4%). Cefdinir concentrations in blister fluid remained equal to or higher than the concentrations in plasma from 6 to 12 h following cefdinir administration. On the basis of the concentrations in blister fluid and the in vitro MIC data, we estimated that cefdinir at 200 to 400 mg administered twice daily would be adequate to treat uncomplicated skin infections caused by Streptococcus pyogenes. Seven volunteers experienced episodes of light-to-moderate diarrhea. These adverse events occurred irrespective of dose.

The role of cefotaxime in the treatment of surgical infections

This study examines the role of cefotaxime in the treatment of both Gram-negative and Gram-positive surgical infections. A dose of 2 g of cefotaxime will sustain peripheral compartment concentrations of 2.6, 3.9, 1.6, and 0.7 micrograms/ml for 6, 8, 10 and 12 h, respectively. Therefore, the proportion of pathogens with a minimal inhibitory concentration (MIC) below the peripheral compartment cefotaxime concentrations was assessed as a measure of therapeutic potential. It was observed that bacterial elimination in infections correlates well with such pharmacodynamic predictions. Therefore, treatment recommendations for surgical infections are based on the following pharmacodynamics. The times above the MIC in the tissue compartment for various pathogens (1988-1994) known to cause surgical infections were: Escherichia coli, 12 h; all pyogenic streptococci, 12 h; pneumococci, 12 h; Haemophilus spp., 12 h; Proteus mirabilis, 12 h; Klebsiella spp., 10.9 h; viridans streptococci, 10.6 h; oxacillin-susceptible, coagulase-negative staphylococci, 9.7 h; Providencia spp., 9.2 h; Clostridium perfringens, 8.6 h; Peptostreptococcus spp., 8 h; oxacillin-susceptible Staphylococcus aureus, 7.3 h; and all S. aureus, 6.8 h. From the examination of pharmacodynamic parameters, cefotaxime appears to be a viable choice for the therapy of surgical infections other than the Gram-negative anaerobes. For those infections, metronidazole with cefotaxime would be preferred.

Effects of blood medium supplements on activities of newer cephalosporins tested against enterococci

This comparative study determined the effect of blood on the antienterococcal activities of the newer cephalosporins. Standardized disk diffusion susceptibility tests were performed with 57 strains of enterococci (30 Enterococcus faecalis strains) on Mueller-Hinton agar with and without 5% sheep blood supplementation. Twelve cephalosporins representing five different structural groups (based on the 7-alpha position substitution) were tested. The greatest frequency of activity enhancement by blood was observed with cefdaloxime and cefdinir (7-alpha hydroxyimino group) against E. faecalis. Cephalosporins with a 7-alpha methoxyimino group (cefpodoxime, cefepime, and cefpirome) had marked increases in zone diameters (3 to > 9 mm) when tested with the blood supplement. Cephems with 7-alpha amino or carboxy substitutions did not demonstrate any enhanced activity. Awareness of this phenomenon is important for the interpretation and accuracy of cephalosporin susceptibility testing.

In vitro evaluation of cefdinir (FK482), a new oral cephalosporin with enhanced antistaphylococcal activity and beta-lactamase stability

Cefdinir (FK482), a new oral cephalosporin with enhanced beta-lactamase stability, was tested by microbroth dilution against respiratory, urogenital, and skin and skin-structure bacterial pathogens. Included were beta-lactamase (beta LAC)-producing and -nonproducing isolates. Activity was compared with that of other orally administered beta-lactams. Cefdinir minimum inhibitory concentrations for 90% of isolates MIC90s (microgram/ml) were < or = 0.5 versus beta LAC+/oxacillin-susceptible Staphylococcus, aureus, S. epidermidis, and S. saprophyticus; < or = 0.06 versus Streptococcus groups A and B, and Neisseria gonorrhoeae beta LAC+; 0.125 versus S. pneumoniae penicillin-susceptible and Proteus mirabilis beta LAC+; 0.25 versus beta LAC+ versus strains of Moraxella catarrhalis, Escherichia coli, Klebsiella pneumoniae, and K. oxytoca; 0.5 versus Haemophilus influenzae beta LAC-; 1 versus H. influenzae beta LAC+; 4 versus Legionella pneumophila beta LAC+; and 8 versus Enterococcus faecalis beta LAC-strains. Cefdinir was equally effective against both standard and high inocula of S. aureus strains producing A, B, C, or D beta LAC types. MICs were also generated versus quality-control reference strains.

In vivo therapeutic efficacy of cefdinir (FK482), a new oral cephalosporin, against Staphylococcus aureus and Haemophilus influenzae in mouse infection models

Cefdinir (FK482), a new oral cephalosporin, displayed potent oral activity versus induced infections in mice. In studies using beta-lactamase-nonproducing (beta LAC-) and -producing (beta LAC+) Staphylococcus aureus strains, respective PD50s (in mg/kg) were 11 and 24 for preventing subcutaneous abscess and 2.7 and 2.3 for preventing lethal systemic infection. In studies using beta LAC- and beta LAC+ Haemophilus influenzae, respective PD50s were 5.8 and 3.1 for preventing lethal systemic infection. Time-kill studies versus H. influenzae showed that 6- to 12-mg/kg dosing was effective in reducing viable counts of these strains in blood by > or = 100-fold by 24 h after challenge. This in vivo performance was comparable to or exceeded values generated by cefaclor, cefpodoxime proxetil, and ampicillin.

Molecular epidemiology and antimicrobial susceptibility testing. Testing of quinolone-resistant Staphylococcus aureus strains isolated in Brazil

An outbreak of 20 oxacillin-resistant Staphylococcus aureus (ORSA) bloodstream infections (BSIs) was detected in the intensive care unit (ICU) at Hospital Sao Paulo, Brazil. In a surveillance study, 10% of ICU personnel were defined as chronic nasal carriers of ORSA. Thirteen BSIs and five nasal isolates were available for phage typing, restriction endonuclease analysis of plasmid (REAP) and chromosomal DNA hybridized with 32P rRNA gene probe. Susceptibility testing against select antimicrobial agents, including 11 quinolones, six glycopeptides, and five topical agents, was performed by broth microdilution and the disk diffusion tests. Ten of the 13 BSI isolates and four of the five nasal strains were oxacillin and quinolone resistant. The new fluoroquinolones CI-960 and WIN57273, the glycopeptides, and the topical agents ramoplanin, bacitracin, mupirocin, and novobiocin were most active. Fourteen strains, 12 BSI isolates, and three nasal isolates showed the same REAP profile. Moreover, the same REAP and chromosomal profile was detected in at least nine BSI isolates and in two nasal isolates. These strains were nontypable by phage typing. We concluded that nosocomial cross-transmission of a single, multiresistant strain of S. aureus occurred and that the epidemic reservoir was nasal carriage by ICU personnel.

Haemophilus test medium interpretive criteria for disk diffusion susceptibility tests with cefdinir, cefetamet, cefmetazole, cefpodoxime, cefdaloxime (RU29246, HR-916 metabolite), and trospectomycin

The disk diffusion zones and the MICs of six newer antimicrobials with significant activity against Haemophilus influenzae were compared using the Haemophilus test medium (HTM) and National Committee for Clinical Laboratory Standards methods. The rank order of potency was cefpodoxime (MIC50, < or = 0.03 micrograms/ml) > cefetamet > cefdinir > cefdaloxime = trospectomycin > cefmetazole (MIC50, 2 micrograms/ml). Susceptible breakpoint interpretive criteria for HTM tests were established that conformed to prior recommendations for each drug when tested against other species. Absolute agreement between methods ranged from 89% to 100% with < or = 1% false-susceptible interpretive errors. The recommended, tentative disk diffusion susceptible interpretive criteria were for 5-micrograms cefdinir disks > or = 20 mm (MIC correlate, < or = 1 micrograms/ml); for 10-micrograms cefetamet disks > or = 18 mm (MIC correlate, < or = 4 micrograms/ml); for 30-micrograms cefetamet disks > or = 21 mm (MIC correlate, < or = 4 micrograms/ml); for 30-micrograms cefmetazole disks > or = 16 mm (MIC correlate, < or = 16 micrograms/ml); for 10-micrograms cefpodoxime disks > or = 21 mm (MIC correlate, < or = 2 micrograms/ml); for 30-micrograms cefdaloxime disks > or = 23 mm (MIC correlate, < or = 2 micrograms/ml) and for 30-micrograms trospectomycin disks > or = 17 mm (MIC correlate, < or = 16 micrograms/ml). beta-Lactamase-negative, ampicillin-resistant (BLNAR) H. influenzae isolates consistently had the highest MICs for each cephalosporin tested.(ABSTRACT TRUNCATED AT 250 WORDS)

Cefdinir (FK482), an orally administered cephalosporin in vitro activity comparison against recent clinical isolates from five medical centers and determination of MIC quality control guidelines

Cefdinir, a new oral cephalosporin, was compared to cefaclor, cefadroxil, cefixime, and cefuroxime against greater than 5000 recent aerobic clinical isolates. This multicenter study revealed broad-spectrum cefdinir activity against all Enterobacteriaceae (MIC50s, 0.06-2 micrograms/ml) except Enterobacter cloacae, Morganella morganii, Proteus vulgaris, and Serratia marcescens (MIC50s, greater than or equal to 4 micrograms/ml). Oxacillin-susceptible staphylococci (MIC90s, 0.5-2 micrograms/ml), beta-hemolytic Streptococcus group B (MIC90, 0.06 micrograms/ml), and Acinetobacter lwoffii were also susceptible to cefdinir. The activity of cefdinir was similar to that of cefixime and cefuroxime against Gram-negative organisms and superior to all tested oral cephems when tested against Gram-positive cocci. None of the cephalosporins were active against oxacillin-resistant Staphylococcus spp., enterococci, Pseudomonas spp., or Xanthomonas maltophilia. MIC quality control range guidelines were established for the strains recommended by the National Committee for Clinical Laboratory Standards documents.

Comparative in vitro activity of cefdinir (CI-983; FK-482) against staphylococci, gram-negative bacilli and respiratory tract pathogens

The in vitro activity of cefdinir (CI-983; FK-482), a new oral cephalosporin, was compared with that of other antimicrobial agents against clinical isolates of staphylococci, gram-negative bacilli and common respiratory tract pathogens. Cefdinir (MIC90 less than or equal to 2.0 micrograms/ml) was more active than cefixime (MIC90 greater than 64 micrograms/ml) and equally as active as cefuroxime (MIC90 2.0 micrograms/ml) against oxacillin-susceptible staphylococci. Cefdinir was active against Haemophilus influenzae, including beta-lactamase producers (MIC90 0.5 microgram/ml), Moraxella catarrhalis (MIC90 less than or equal to 0.12 microgram/ml), Streptococcus pneumoniae (MIC90 less than or equal to 0.06 microgram/ml) and Streptococcus pyogenes (MIC90 less than or equal to 0.06 microgram/ml). The activity of cefdinir against gram-negative bacilli was variable; organisms with chromosomal cephalosporinases were often resistant.

In vitro activity and susceptibility to hydrolysis of S-1006

The in vitro activity of S-1006, the active component of a new orally absorbed cephalosporin, S-1108, inhibited 90% of Staphylococcus aureus isolates at less than or equal to 2 micrograms/ml, 90% of group A, B, C, F, and G streptococci and Streptococcus pneumoniae isolates at less than or equal to 0.12 microgram/ml, and all Haemophilus influenzae isolates at less than or equal to 0.06 microgram/ml. Although 50% of the members of the family Enterobacteriaceae were inhibited by less than or equal to 2 micrograms of S-1006 per ml, Enterobacter spp. and Citrobacter freundii resistant to ceftriaxone were resistant to S-1006. The MICs of S-1006 for approximately 20% of Providencia, Proteus vulgaris, and Serratia isolates were 4 micrograms/ml. S-1006 was hydrolyzed by the plasmid TEM-3, TEM-5, PSE-1, and PSE-4 beta-lactamases and by the chromosomal beta-lactamase of Enterobacter and Morganella spp. and P. vulgaris.

Comparative kill and growth rates determined with cefdinir and cefaclor and with Streptococcus pneumoniae and beta-lactamase-producing Haemophilus influenzae

The relationship between the growth rate and the kill rate was used to evaluate and to compare the in vitro bactericidal activities of cefdinir, a new oral cephalosporin, and cefaclor against Streptococcus pneumoniae and beta-lactamase-producing strains of Haemophilus influenzae. These frequently encountered pathogens of community-acquired respiratory tract infections are usually susceptible to both drugs. The MIC ranges for cefdinir and cefaclor were, respectively, 0.03 to 0.06 and 0.25 to 0.5 micrograms/ml for S. pneumoniae and 0.25 and 4 to 8 micrograms/ml for H. influenzae. The colony counts (CFU per milliliter) measured after 6 h of exposure to a range of antibiotic concentrations in broth were plotted against the colony count of the control culture over the same period of time. Higher kill rates versus bacterial growth rates were noted for S. pneumoniae for both drugs (positive balance). Conversely, lower kill rates versus growth rates were noted for H. influenzae for both drugs (negative balance). In conclusion, the bactericidal activities of both drugs against S. pneumoniae and H. influenzae were similar when expressed by the relationship between the growth rate and the kill rate at 6 h, but cefdinir was more active at lower concentrations.

MIC quality control guidelines for Haemophilus susceptibility tests using cefdinir (FK482), cefepime, cefetamet, cefpirome, ceftibuten, fleroxacin, temafloxacin, clarithromycin, RP59500, and trospectomycin

A multilaboratory study was performed to establish broth microdilution MIC quality control (QC) guidelines for 10 investigational drugs which previously demonstrated significant activity against Haemophilus influenzae. MIC QC ranges for H. influenzae ATCC 49247 with Haemophilus test medium were determined by using multiple contemporary lots of Haemophilus test medium and the National Committee for Clinical Laboratory Standards' recommended numbers of replicate tests. On the basis of these results, QC ranges (generally modal MIC +/- one log2 dilution) are proposed for cefdinir, cefepime, cefetamet, cefpirome, ceftibuten, fleroxacin, temafloxacin, clarithromycin, RP59500, and trospectomycin. The proposed QC guidelines for clarithromycin and temafloxacin were recently accepted by the National Committee for Clinical Laboratory Standards.

Antimicrobial activity of three investigational oral cephalosporins (BK-218, cefdinir, and RU29246) against Legionella

Three new, orally administered cephalosporins (BK-218, cefdinir, RU29246) were tested against 13 representative strains of Legionella. Cefdinir was most active [50% minimum inhibitory concentration (MIC50), 1 micrograms/ml], a potency comparable to the reference drug cefixime and eightfold less active than erythromycin. BK-218 was the least active cephalosporin (MIC50, 8 micrograms/ml) or 100-fold less potent than rifampin. These investigational cephems appear poorly suited by activity assays for Legionellosis therapy.

Antimicrobial activity of RU29246 (HR916 metabolite) compared with four other oral beta-lactams tested against more than 5000 clinical isolates

The activity of RU29246, the active metabolite of the oral cephalosporin ester HR916, was compared in a multicenter study with that of the four oral beta-lactam antibiotics cephalexin, cefaclor, cefixime and amoxicillin/clavulanate (amoxicillin/CA). RU29246 was generally 2- to 8-fold more active than the other oral cephalosporins and comparable to amoxicillin/CA against staphylococci, and was the most active cephalosporin against group B streptococci. All four cephalosporins were ineffective against enterococci. RU29246 was the only cephalosporin consistently active against Acinetobacter, but all beta-lactam antibiotics had poor activity against Pseudomonas spp. and Xanthomonas maltophilia. RU29246 was comparable to cefixime and more active than the other cephalosporins against members of the family Enterobacteriaceae. However, all of the antibiotics had poor activity against Enterobacter cloacae and Serratia marcescens. Quality control reference ranges for the quality control organisms Staphylococcus aureus ATCC 29213 and Escherichia coli ATCC 25922 are proposed for the broth dilution method based on data derived from this multicenter study.

In vitro activity evaluations of cefdinir (FK482, CI-983, and PD134393). A novel orally administered cephalosporin

Cefdinir, a so-called third-generation oral cephalosporin was tested in vitro against over 700 pathogens from patients with bacteremia. Cefdinir was very active against the Enterobacteriaceae with a 50% minimum inhibitory concentration (MIC50) value range of less than or equal to 0.03-8 micrograms/ml. The enteric species having the highest MIC90S (greater than or equal to 16 micrograms/ml) were Citrobacter freundii, and the enterobacters, Morganella morganii, Proteus vulgaris, and Serratia marcescens. Cefdinir was generally two- to fourfold less active than cefixime, but markedly more potent with a wider spectrum compared with older oral cephalosporins, cefaclor or cefuroxime. In contrast to cefixime, cefdinir inhibited Staphylococcus aureus (MIC90, 1 micrograms/ml) and other staphylococci. Pneumococci, beta-hemolytic streptococci, Haemophilus influenzae, Moraxella catarrhalis, and pathogenic Neisseria spp. (MIC90S, 0.12-0.5 micrograms/ml) were cefdinir susceptible, but Pseudomonas aeruginosa, oxacillin-resistant staphylococci and Bacteroides fragilis gr. strains were resistant. Cefdinir was generally bactericidal with a minimal inoculum effect at 10(6) colony-forming units per spot. Cefdinir beta-lactamase hydrolysis by some recently described extended broad spectrum beta-lactamases was suspected. Cefdinir exhibited a wide, balanced spectrum for an oral cephalosporin indicating possible clinical use against susceptible pathogens in respiratory tract, urinary tract, genital and cutaneous infections.

Use of antimicrobial susceptibility testing for epidemiology and the selection of oral, parenteral and topical regimens for control of CAPD-associated Staphylococcus aureus infection

Staphylococcus aureus is an important cause of peritonitis in patients undergoing continuous ambulatory peritoneal dialysis (CAPD). Using standard broth microdilution and disk diffusion methodology, we evaluated the in vitro activity of selected antimicrobial agents against S. aureus strains isolated from CAPD patients to assess candidate regimens for 1) topical agent control of colonization, 2) oral chemotherapy of CAPD infectious complications, and 3) parenteral treatment of serious CAPD-associated staphylococcal infections. A total of 34 isolates (31 patients) of S. aureus were available for testing, including 29 isolates (29 patients) from pericatheter skin, four isolates (four patients) from the nares, and one isolate from an episode of peritonitis. Six of the isolates were oxacillin-resistant (ORSA). The antimicrobial agents tested by broth microdilution included 17 different quinolones, 10 cephalosporins, six glycopeptides, two aminoglycosides, and imipenem. A total of eight potential topical agents, including the antistaphylococcal agent mupirocin, were tested by disk diffusion. All of the quinolones, with the exception of nalidixic acid (MIC90 greater than 16 micrograms/ml), had excellent activity against both ORSA and oxacillin-susceptible S. aureus (OSSA) with the most active agent being WIN57273 (MIC90 less than or equal to 0.015 microgram/ml). Imipenem and the cephalosporins, with the exception of cefixime, ceftazidime, and E-1040, possessed good activity against OSSA. None of the beta-lactam agents tested were active against ORSA. Likewise, the aminoglycosides, amikacin and gentamicin, exhibited good activity against OSSA strains but no activity against ORSA strains. All glycopeptides tested demonstrated excellent activity against ORSA strains. Of the topical antimicrobial agents tested only bacitracin, mupirocin, and nitrofurantoin were active against all OSSA and ORSA strains tested.(ABSTRACT TRUNCATED AT 250 WORDS)

Cefixime

Cefixime is a new orally active third-generation cephalosporin with a broad spectrum of activity against a variety of both gram-positive and -negative bacteria including many beta-lactamase-producing strains of streptococci, Haemophilus influenzae, Neisseria gonorrhoeae, and the majority of the Enterobacteriaceae. Activity of cefixime against Staphylococcus aureus, enterococci, Listeria monocytogenes, and Pseudomonas spp. is poor. The relatively long elimination half-life of cefixime (approximately 3.0 h) has made possible once- to twice-daily administration with the potential added benefit of improved patient compliance. Clinical trials indicate that cefixime is at least as effective as standard agents in the treatment of genitourinary and upper respiratory tract infections. The incidence of resistant organisms reported during clinical trials with cefixime was low. Adverse reactions observed during clinical trials were relatively uncommon and generally mild and transient in nature. The most significant adverse reactions reported were diarrhea and stool changes occurring in up to 20 percent of patients.

[Antibacterial activity and beta-lactamase stability of eleven oral cephalosporins]

Oral cephalosporins (cefixime, cefdinir, cefetamet, ceftibuten, cefpodoxime, loracarbef, cefprozil, cefuroxime, cefaclor, cefadroxil and BAY 3522) were compared by their antibacterial profile including stability against new beta-lactamases. Both activity and antibacterial spectrum of compounds structurally related to third generation parenteral cephalosporins (of the oximino class) were superior to established compounds. Activity against staphylococci was found to be highest for cefdinir, cefprozil and BAY 3522. Cefetamet, ceftibuten and cefixime demonstrate no clinically meaningful antistaphylococcal activity while the other compounds investigated demonstrate intermediate activity. The antibacterial spectrum was broadest for cefdinir and cefpodoxime. New oral cephalosporins are equally inactive as established compounds against Enterobacter spp., Morganella, Listeria, Pseudomonas and Acinetobacter spp., methicillin-resistant staphylococci, Enterococcus spp., penicillin-resistant pneumococci and anaerobes. New extended broad-spectrum betalactamases (TEM-3, TEM-5, TEM-6, TEM-7, SHV-2, SHV-3, SHV-4, SHV-5, CMY-1, CMY-2, and CTX-M) are active against the majority of oral cephalosporins. Ceftibuten, cefetamet, cefixime and cefdinir were stable against some of these enzymes even to a higher extent than parenteral cephalosporins. New oral cephalosporins should improve the therapeutic perspectives of oral cephalosporins due to their higher activity against pathogens marginally susceptible to established compounds (higher multiplicity of maximum plasma concentrations over MICs of the pathogens) and furthermore by including in their spectrum organisms resistant to established absorbable cephalosporins (e.g. Proteus spp., Providencia spp., Citrobacter spp., and Serratia spp.).