Present status of therapy with combinations of antibiotics

Studies on antibiotic syngerism against enterococci. II. Effect of various antibiotics on the uptake of 14 C-labeled streptomycin by enterococci

The mechanism by which agents that inhibit bacterial cell wall synthesis produce a synergistic effect against enterococci when combined with aminoglycoside antibiotics has not been elucidated. Using (14)C-labeled streptomycin, it could be shown that uptake of this aminoglycoside antibiotic was markedly enhanced in enterococci growing in the presence of penicillin or other agents which inhibit the synthesis of bacterial cell walls. There was no enhancement of streptomycin uptake when the cells were incubated with antibiotics which primarily affect the bacterial cell membrane or inhibit protein synthesis. Increased streptomycin uptake was produced by penicillin only in actively growing bacteria. These observations are consistent with the hypothesis that enterococci exhibit a natural barrier to the entry of streptomycin which can be overcome by agents which inhibit cell wall synthesis, thus producing a synergistic effect.

Neto FD, Brasil MHS, Santos VMD, Henrique S, Saldanha LF, Souza Filho AJ, Suzuki LE. Aspectos gerais das septicemias e bacteriemias estafilocócicas no adulto

São apresentados 25 casos de infecções sistêmicas por estafilococos por pacientes adultos. Foram incluídos somente os casos em que houve concordância entre os achados bacteriológicos e clínicos. O Staphylccoceus aureus foi o mais encontrado em hemoculturas (17 casos). Dezoito casos comportaram-se verdadeiramente como septicemias caracterizadas por lesões metastáticas principalmente pulmonares, configurando os quadros clássicos de infartos pulmonares sépticos múltiplos. As principais complicações cardiovasculares foram a miocardite, endocardite, choque e o cor pulmonale agudo. As complicações neurológicas mais freqüentes foram meningite, coma e convulsões, tôdas seguidas de óbito. A porta de entrada mais freqüente foi através de infecção cutânea presente em 48% dos casos, seguida do aparelho genital feminino em conseqüência do abôrto provocado (20%). É apresentado estudo anátomo-patológico de 4 casos. Na discussão são apresentadas características biológicas do germe no sentido de facilitar o entendimento da fisiopatologia destas infecções sistêmicas assim como de esclarecer o quadro clínico exibido pelos pacientes. Breves considerações são realizadas no que concerne a patogenia e o quadro clínico nestas infecções e aspectos gerais de conduta terapêutica são assinalados.

Effect of different media on in vitro studies of antibiotic combinations

In an effort to determine the adequacy of a standard broth medium in the evaluation of antibiotic combinations, 20 strains of various bacterial species were studied simultaneously in Mueller-Hinton broth and in freshly drawn human serum from apparently healthy volunteers. Studies of growth dynamics by use of the usual plate dilution technique for quantitating colony-forming units were performed with strains of Staphylococcus aureus (methicillin-resistant and methicillin-susceptible), Streptococcus faecalis, Escherichia coli, Aerobacter, Klebsiella, and Proteus mirabilis. A variety of different antibiotics were investigated. With 19 of the 20 strains, interpretations of synergism or antagonism were the same in both media. Therefore, despite minor variations when the same strain was studied in both serum and broth, it is concluded that Mueller-Hinton broth is an adequate medium for use in studies of chemotherapeutic combinations in vitro. A simplified method for studying bactericidal activity is described, which is deemed practical for clinical microbiology laboratories and which led to the same conclusions regarding the combinations as were obtained by the more arduous plate dilution test.