Relationship between growth rate and phagocytosis susceptibility in Streptococcus mutans.

Streptococcus mutans strain GS-5 was grown in a variety of carbon sources in order to achieve different balanced growth rates, ranging from 61 to 383 minutes. The influence of the S. mutans growth rate on mouse phagocyte activity against these bacteria has been evaluated. The percentages of bacteria phagocytized and intracellularly killed by macrophages rose to 60-80% and 85-95% respectively when the doubling time was longer, showing that S. mutans is particularly sensitive to nonspecific immune defence mechanisms when cultured under conditions similar to those of its natural ecosystem.

[Use of ofloxacin in otorhinolaryngologic infections]. / Impiego dell'ofloxacina nelle infezioni del distretto O.R.L.

Ofloxacin, a new fluoroquinolonic synthetic compound with broad antibacterial spectrum, was used in per os therapy of 15 ear, nose and throat infected patients. The antibiotic was then compared with other eight antimicrobial agents against the Gram-positive and Gram-negative isolates. Either in vitro than in vivo the god antibacterial activity and tolerance of ofloxacin, particularly against Gram-positive infections, was demonstrated. Results point out the possibility of utilization of ofloxacin per os against ear, nose and throat infections.

Killing of macrophage-ingested mycobacteria by rifampicin, pyrazinamide, and pyrazinoic acid alone and in combination.

A study was undertaken with the aim of assessing the killing capacity of rifampicin, pyrazinamide, and pyrazinoic acid on macrophage-ingested, live Mycobacterium tuberculosis. The 3 drugs were used at concentrations corresponding to the average peak levels observed in humans after administration of therapeutic doses that had been found to penetrate into macrophages in a previous study. The degree of killing was studied after exposure of the cell cultures to the individual drugs and their combinations for 3, 18, 24, 48, and 72 h. Comparing the degree of killing in the control, drug-free cultures with that observed in the drug-containing systems, over a period of 3 to 24 h, indicated that in these a greater, more rapid, although not statistically significant, killing of intracellular mycobacteria took place. At 48 h the degree of killing was similar in the control and in the drug-containing cell cultures. Between 48 and 72 h, however, a marked growth of intracellular mycobacteria was observed in the control cultures. This phenomenon was much less evident in the drug-containing cultures. No major increase in the killing effect with respect to that observed with the individual drugs was found after exposure of the macrophages to all possible combinations of the 3 drugs.

Susceptibility of clinical isolates of gram-positive and gram-negative organisms to cefatrizine.

The in vitro activity of cefatrizine was evaluated against 294 Gram-positive and 270 Gram-negative bacteria isolated from clinical specimens. Cefatrizine had excellent activity against Gram-positive cocci, inhibiting all except enterococci at minimal inhibitory concentrations below 1 mcg/ml. Moreover, cefatrizine was an effective antibacterial agent for most major Gram-negative species. Cefatrizine activity was tested against 34 strains of H. influenzae and 37 strains of K. pneumoniae and compared with that of other orally administered cephalosporins. Cefatrizine MIC50 values were much lower than those recorded for cephalexin and cefadroxil.

[Comparative study of the in vitro activity of dibekacin, piperacillin, cefotaxime and cefuroxime on gram-negative bacteria]. / Studio comparativo dell'attivita' in vitro di dibekacina, piperacillina, cefotaxime e cefuroxime su batteri Gramnegativi.

The activity in vitro of the dibekacin was compared with that of piperacillin, cefotaxime and cefuroxime against 266 recently isolated gramnegative pathogens. Dibekacin was consistently more potent than cefotaxime, cefuroxime and piperacillin, with MIC50 and MIC90 values lower than the others. Dibekacin and cefotaxime were essentially similar in activity against all the bacteria, with the singular exception of Pseudomonas aeruginosa, which was markedly more susceptible to the former drug.

[Comparative activity of dibekacin and several cephalosporins on Pseudomonas aeruginosa]. / Attivita' comparativa in vitro della dibekacina e di alcune cefalosporine su Pseudomonas aeruginosa.

Dibekacin is a semisynthetic aminonglycoside derivative of kanamicin B, with highly activity against most gram-positive and gramnegative bacteria. It is also active against bacteria relatively resistant to other antibiotics. Since Pseudomonas aeruginosa seems to be the most common strain recent clinical isolated, we compared the in vitro activity of dibekacin with other eigh cephalosporins against 579 clinical isolates of sensitive and gentamicin-carbenicillin resistant Pseudomonas aeruginosa. The results indicate that dibekacin was more active than any of the other antibiotics tested against all the organisms tested, including carbenicillin-resistant Pseudomonas aeruginosa.