In-vitro activity of 29 antimicrobial agents against penicillin-resistant and -intermediate isolates of Streptococcus pneumoniae

Abstract

Antibiotic resistance among isolates of Streptococcus pneumoniae is increasing worldwide. Optimal therapy, though unknown, should be guided by in-vitro susceptibility testing. Currently, vancomycin is the only approved antibiotic that is universally active against multiresistant S. pneumoniae. In-vitro activities were determined for 29 antimicrobial agents against 22 penicillin-intermediate S. pneumoniae (PISP) and 16 penicillin-resistant S. pneumoniae (PRSP) isolates. MICs were determined in cation-adjusted Mueller-Hinton broth with 3% lysed horse blood in microtitre trays. Antimicrobial classes tested included cephalosporins, penicillin, aminopenicillins, macrolides, quinolones, carbapenems and other antimicrobial agents. Among the classes of antimicrobial agents tested, wide differences in susceptibility were demonstrated for both PISP and PRSP. Of the cephalosporins, ceftriaxone and cefotaxime demonstrated the best in-vitro activity for both PISP and PRSP. Of the quinolones, clinafloxacin and trovafloxacin showed the greatest in-vitro activity. Rifampicin and teicoplanin demonstrated excellent in-vitro activity. Promising in-vitro results of newer agents, such as quinupristin/dalfopristin, ramoplanin, teicoplanin and linezolid may justify further evaluation of these agents in clinical trials.

In Vitro Activities of Ramoplanin, Teicoplanin, Vancomycin, Linezolid, Bacitracin, and Four Other Antimicrobials against Intestinal Anaerobic Bacteria

“…It has demonstrated activity against a wide spectrum of gram-positive organisms, including antibiotic-resistant strains of staphylococci and enterococci and less frequently encountered pathogens such as Corynebacterium jeikeium, Listeria monocytogenes, and Bacillus spp. (5,9,10,11,12,14,16); however, limited data are available on the drug's activity against anaerobic bacteria (3,14). Broad-spectrum antimicrobials with activity against anaerobes may disrupt the ecological balance of the intestinal flora and promote colonization with VRE and Clostridium difficile (6,7,8,15,19), while antimicrobials with minimal antianaerobe activity preserve the normal intestinal anaerobic flora responsible for colonization resistance (18).…”

“…It has demonstrated activity against a wide spectrum of gram-positive organisms, including antibiotic-resistant strains of staphylococci and enterococci and less frequently encountered pathogens such as Corynebacterium jeikeium, Listeria monocytogenes, and Bacillus spp. (5,9,10,11,12,14,16); however, limited data are available on the drug's activity against anaerobic bacteria (3,14).…”

Efflux-Mediated Resistance to Fluoroquinolones in Gram-Positive Bacteria and the Mycobacteria

“…FQs are traditionally less active against gram-positive pathogens, although they are clinically useful against Mycoplasma pneumonia and have been employed in the treatment of drug-resistant mycobacterial infections (5), as well as infections caused by Staphylococcus aureus, Enterococcus faecalis, and penicillin-resistant Streptococcus pneumoniae (reviewed in references 6 and 24). With the development of newer FQs exhibiting enhanced activity against gram-positive bacteria (18,35,43,62) it is likely, too, that this class of compounds will see more frequent use against these organisms. Still, it is clear that FQ use promotes FQ resistance, which is already a problem in methicillin-resistant S. aureus (MRSA), and has, in fact, been reported in all gram-positive pathogens for which FQ use has occurred.…”

Pharmacodynamic Activity and Efficacy of Linezolid in a Rat Model of Pneumococcal Pneumonia

“…It has excellent activity against both penicillin-sensitive and penicillin-resistant S. pneumoniae (14,15,17). In the present study, the pharmacokinetic and pharmacodynamic properties of linezolid, as well as its efficacy against a penicillin-sensitive (MIC, 0.032 g/ml) S. pneumoniae isolate, were compared to those of ceftriaxone, an expanded-spectrum parenteral cephalosporin.…”