Activities of oral and parenteral agents against penicillin-susceptible and -resistant pneumococci

Abstract

This study examined bacteriostatic and bactericidal activities of oral and parenteral antibiotics for penicillin-susceptible and intermediately and fully penicillin-resistant pneumococci. ␤-Lactamase inhibitors did not affect ␤-lactam results. The activities of ampicillin, amoxicillin ؎ clavulanate, WY-49605, cefuroxime, cefpodoxime, cefdinir, cefixime, and cefaclor against two penicillin-susceptible, two intermediately penicillin-resistant, and two fully penicillin-resistant pneumococcal strains were tested. For all three groups, bacteriostatic values of amoxicillin and WY-49605 were lower than were those of other ␤-lactams tested. Of the cephalosporins, cefdinir, cefuroxime, and cefpodoxime yielded the lowest bacteriostatic values. All ␤-lactams were bactericidal (reduced original counts by >3 log 10 CFU/ml) at 1 dilution above bacteriostatic values, except for cefpodoxime (bactericidal at 2 dilutions above bacteriostatic values for one susceptible strain and one intermediately resistant strain), cefuroxime (bactericidal at 2 dilutions above bacteriostatic values for one intermediately resistant strain), and ampicillin (bactericidal at 2 dilutions above bacteriostatic values for one intermediately resistant strain). The activities of piperacillin, piperacillin-tazobactam, ticarcillin, ticarcillinclavulanate, ampicillin, ampicillin-sulbactam, ceftriaxone, ceftazidime, and ciprofloxacin against four penicillin-susceptible, two intermediately penicillin-resistant, and four fully penicillin-resistant pneumococcal strains were evaluated. Bacteriostatic values of piperacillin, ampicillin, and ceftriaxone for all groups were lower than were those of ticarcillin and ceftazidime. Bacteriostatic values of ciprofloxacin were unaffected by penicillin susceptibility. All ␤-lactams were bactericidal at 1 dilution above the bacteriostatic value, except for piperacillin (bactericidal at 2 dilutions above the bacteriostatic value for one intermediately resistant strain), ticarcillin (bactericidal at 2 dilutions above the bacteriostatic value for one susceptible strain and one resistant strain), ampicillin (bactericidal at 2 dilutions above the bacteriostatic value for two resistant strains), ceftriaxone (bactericidal at 2 dilutions above the bacteriostatic value for one resistant strain), and ceftazidime (bactericidal at 2 dilutions above the bacteriostatic value for one susceptible strain).

Usefulness of Betalactam Therapy for Community-Acquired Pneumonia in the Era of Drug-ResistantStreptococcus pneumoniae:A Randomized Study of Amoxicillin-Clavulanate and Ceftriaxone

“…When choosing the most appropriate betalactam agent, it should be borne in mind that activity against penicillin-resistant pneumococci varies greatly among different betalactams and that cephalosporins with poor activity or an unfavorable pharmacodynamic profile should be avoided. 21,33 In this regard it should be noted that at the dosage used of parenteral amoxicillin and ceftriaxone, the plasma levels of both antibiotics are above 8 mg/mL during a large percentage of the dosing interval. 26,35 In conclusion, in our area where penicillin resistance is prevalent, sequential intravenous/oral amoxicillin-clavulanate and parenteral ceftriaxone were effective and safe for empirical treatment of hospitalized patients with acute bacterial pneumonia, including cases due to pneumococcal strains with penicillin MICs up to 4 mg/mL.…”

Newer oral antimicrobials for resistant respiratory tract pathogens

“…8 Cefprozil, cefuroxime, and cefpodoxime may be useful against strains with intermediate resistance to penicillin (minimal inhibitory concentration ~1 J..Ig/mL), but none of the current oral cephalosporins should be used to treat highly resistant pneumococcal isolates (table 1). Newer compounds, such as cefdinir (Omnicef), are also ineffective against these highly resistant strains.…”

“…Newer compounds, such as cefdinir (Omnicef), are also ineffective against these highly resistant strains. 8 As the incidence of penicillin-resistant pneumococci increases, the usefulness of oral cephalosporins for empirical treatment of respiratory tract infections will greatly diminish.…”

Antimicrobial activity of faropenem, a new oral penem, against lower respiratory tract pathogens

“…However, many antibiotics are toxic at these levels, and there is, in addition, the risk of side effects; also, the threshold (level) of resistance of the pathogen can be easily increased, reducing the efficacy of the antibiotic prescription. There is an urgent need for oral and parenteral β‐lactams for the treatment of these infections [4]. Furthermore, there are currently no definite data on which to base treatment of infection associated with penicillin‐resistant pneumococci.…”