Activity of moxalactam and cefotaxime alone and in combination with ampicillin or penicillin against group B streptococci

Abstract

The activities of moxalactam and cefotaxime, alone and combined with ampicillin or penicillin, against 40 isolates of group B streptococci were assessed by using the microtiter broth dilution, checkerboard, and time-kill techniques. Neonatal meningitis, when caused by group B streptococci or Escherichia coli, has a mortality rate of 15 to 50% (3,4,9,10,15,21). Ampicillin plus a parenteral aminoglycoside, standard therapy for this disease, does not always effect clinical and microbiological cure. Although numerous factors, e.g., prematurity, play roles in determining the poor outcome of neonatal meningitis, there is definitely room for improvement in the antimicrobial therapy of this disease.Moxalactam and cefotaxime, two relatively new beta-lactam derivatives, hold promise for therapy of neonatal meningitis caused by gramnegative bacteria. The minimal inhibitory concentrations (MICs) of these agents for most strains of E. coli range from 0.06 to 0.125 ,ug/ml (7,17,18

Reverse inoculum effect in bactericidal activity and other variables affecting killing of group B streptococci by penicillin

“…The present experiments included adequate characterization of 11 group B streptococci, and none was found tolerant as defined by an MCB/MIC ratio of 8 to 32:1 or more. This result was consistent with those reported from several laboratories in the, United States, where the prevalence of'tolerance has varied from 0 to 8% (13,(16)(17)(18)(19), whereas our finding was in striking contrast to the geographically more closely related ones from the Federal Republic of Germany and England, where 5 of 38 (13%), 12 of 21 (57%), and 10 of 14 (71%) tolerant strains were detected (3,24,27). The Eagle effect predicts that there should be strains which are not effectively killed by 32 x MIC and more, although the true MBC might be much less.…”

“…DISCUSSION The details of the methods used in broth dilution susceptibility testing of group B streptocqcfi have varied widely, as exemplified by the choice of niodium. In the reports cited in this paper, Todd-Hewitt b oth has been used by four groups (2, 12, 23, 24), Mueller-17tnton broth by three groups (1,4,13,(15)(16)(17)20), Trypticase soy broth (BBL Microbiology Systems) by two groups (9,18), and Schaedler broth (19) and the Sensititre medium (3) by one group each. Our choice of Todd-Hewitt broth was conservative, and it remains to be seen whether any of our findings were medium dependent.…”