Susceptibility of gram-negative bacteria and Staphylococcus aureus to combinations of ticarcillin and clavulanic acid

The role of new antibiotics for the treatment of infections in the emergency department

Treatment of infectious diseases comprises a large part of emergency medicine practice. The management of infectious diseases in the emergency department is often different than in other settings because of the types of infectious presentations and the frequent necessity of empiric treatment decisions. This paper examines the new antimicrobials and their role for the treatment of infections in the ED.

Comparative in vitro susceptibilities of 504 bacteremic isolates to ticarcillin plus clavulanic acid and other antimicrobial agents

A total of 504 clinical bacteremic isolates were tested for susceptibility to ticarcillin-clavulanic acid and 12 other antibiotics. Ticarcillin-clavulanic acid showed superior antibacterial activity compared to penicillin, mezlocillin, piperacillin, ticarcillin, gentamicin, and amikacin against bacteremic isolates of methicillin-susceptible Staphylococcus aureus and Staphylococcus epidermidis. However, ticarcillin-clavulanic acid's activity was inferior to that of vancomycin against methicillin-resistant isolates of S. aureus and S. epidermidis. For Escherichia coli, Klebsiella oxytoca, Proteus mirabilis, Providencia stuartii, and lactose nonfermenting aerobic gram-negative bacilli, the activity of ticarcillin-clavulanic acid surpassed that of mezlocillin, piperacillin, and ticarcillin. Of the antimicrobial agents tested, ticarcillin, piperacillin, ceftazidime, and amikacin were the most active antibiotics against Pseudomonas aeruginosa.

Discrepancies between disk diffusion and broth susceptibility studies of the activity of ticarcillin plus clavulanic acid against ticarcillin-resistant Pseudomonas aeruginosa

Ticarcillin and clavulanic acid in combination were tested against 40 Pseudomonas aeruginosa isolates resistant to ticarcillin by disk diffusion. A total of 21 isolates (53%) were susceptible to ticarcillin-clavulanate by disk diffusion, under currently recommended criteria for ticarcillin susceptibility. Macro-broth dilution tests (ticarcillin plus clavulanic acid, 2 micrograms/ml) confirmed susceptibility (MIC less than or equal to 64 micrograms/ml) of only 8 (38%) of 21 isolates. Time-kill studies of disk diffusion susceptible isolates indicated 2 log10 or greater killing of most isolates at 6 h in broth containing ticarcillin (64 micrograms/ml) combined with clavulanic acid (1, 2, 5, or 10 micrograms/ml). After 6 h, regrowth was common in all concentrations of clavulanic acid except 10 micrograms/ml. Regrowth populations were resistant to ticarcillin-clavulanate by MIC determination. Poor bactericidal activity of ticarcillin-clavulanate against ticarcillin-resistant P. aeruginosa was confirmed, as most isolates did not undergo 99.9% or greater killing at 24 h in all concentrations of clavulanic acid. Serotype O-11 was our most common serotype and was associated with disk diffusion "pseudosusceptibility." Concomitant disk diffusion testing of ticarcillin-clavulanate and ticarcillin is recommended for testing the susceptibility of P. aeruginosa to ticarcillin-clavulanate by disk diffusion. P. aeruginosa isolates resistant to ticarcillin should as a rule be considered also resistant to ticarcillin-clavulanate, despite apparent susceptibility by disk diffusion.

Resistance to beta-lactams in Enterobacteriaceae: distribution of phenotypes related to beta-lactamase production

Phenotypes of susceptibility to amoxycillin (Amo), ticarcillin (Tic), cephalothin (Ctn) were determined in 1366 isolates of Enterobacteriaceae by disk method and beta-lactamases were identified in 243 strains belonging to different phenotypes of amoxycillin-resistant strains. AmoR TicR CtnS strains (25%) were penicillinase producers and all of them were susceptible to the combination amoxycillin/clavulanic acid (Amo/CA) and ticarcillin/clavulanic acid (Tic/CA). Amo1/R TicS CtnR strains (12%) were cephalosporinase producers and resistance to Amo/CA was observed, except for Proteus vulgaris. AmoR TicR CtnR strains (18%) often produced two beta-lactamases (penicillinase and cephalosporinase) and they were resistant to Amo/CA; in this group, susceptibility to Tic/CA depends on the nature and the amount of the beta-lactamase produced, except for Serratia marcescens for which antibiotic resistance is probably due to other mechanisms. Tic/CA resistance was mainly found in Serratia marcescens (41%) and Enterobacter cloacae (36%).

Antibacterial activity of ticarcillin in the presence of clavulanate potassium

The antibacterial effects produced by ticarcillin disodium plus clavulanate potassium, a combination of the broad-spectrum penicillin ticarcillin, and the beta-lactamase inhibitor clavulanic acid as the potassium salt, have been measured in vitro and in experimental infection studies. The presence of clavulanic acid resulted in a significant enhancement of the activity of ticarcillin against a wide range of beta-lactamase-producing bacteria. These included ticarcillin-resistant strains of Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, P. vulgaris, Yersinia enterocolitica, and the anaerobe Bacteroides fragilis. In addition, beta-lactamase-producing isolates of Hemophilus influenzae, Branhamella catarrhalis, Neisseria gonorrhoeae, and Staphylococcus aureus were susceptible to ticarcillin and clavulanate. Clavulanic acid did not influence the activity of ticarcillin against ticarcillin-susceptible bacteria. The bactericidal effects of the antibiotic combination were measured in an in vitro kinetic model in which the drug concentrations were varied to simulate those measured in humans after intravenous dosing with ticarcillin (3.0 g) and clavulanate potassium (100 mg clavulanic acid). In these tests, ticarcillin plus clavulanic acid had pronounced bactericidal activity against ticarcillin-resistant bacteria. The protection of ticarcillin by clavulanic acid from inactivation by bacterial beta-lactamases in vivo was demonstrated in experimental infection models in which the efficacy of the ticarcillin plus clavulanic acid combination against infections caused by beta-lactamase-producing bacteria was correlated with the presence of effective concentrations of both antibiotic and inhibitor at the site of infection.

Timentin therapy for bone, joint, and deep soft tissue infections in children

Timentin, a combination of clavulanic acid (0.1 g) and ticarcillin (3.0 g), has proved effective in vitro against bacterial pathogens that produce beta-lactamases. The usual etiologic bacteria of osteochondritis of the foot (Pseudomonas species) and osteomyelitis/septic arthritis (Staphylococcus aureus) are commonly resistant to penicillins. To date, we have used Timentin to treat 30 children with bone, joint, and deep soft tissue infections. Timentin was administered intravenously at an average dosage of 207 mg/kg per day for mild to moderate infection and 310 mg/kg per day for bone and joint infections with systemic signs (sepsis). The lower dose was used in 24 patients and the other six patients, who had signs of sepsis, received the higher dose. All patients received Timentin intravenously over 30 minutes every four to six hours for a minimum of five days (mean 6.6 +/- 2.6 days, range five to 14 days). The mean time to defervescence and/or reduction in clinical symptoms was 1.6 +/- 1.3 days (range zero to four days). Osteochondritis due to P. aeruginosa was diagnosed in six patients, and septic bursitis, osteomyelitis, or septic arthritis due to S. aureus (13 patients) or Staphylococcus species and group A streptococci (four patients) was diagnosed in 17 patients. All isolates were susceptible to Timentin in vitro by disk-diffusion analysis. All patients showed a response to therapy with Timentin, with or without surgical intervention. All patients had clinical and microbiologic cures; no adverse reactions or side effects were observed. There have been no clinical or microbiologic relapses to date. Timentin may prove to be useful in specific bone and joint infections in children.

In vitro activity of ticarcillin plus clavulanic acid against bacteria isolated in three centers

Over 10,000 bacterial isolates were tested against ticarcillin alone or combined with clavulanic acid (2.0 micrograms/ml). Of 5,295 Enterobacteriaceae, 72% were susceptible to ticarcillin alone, whereas 91% were susceptible to the combination. Bacteroides fragilis and Bacteroides melaninogenicus isolates were more susceptible to the combination. The activity of ticarcillin against other microorganisms was not profoundly influenced.