Multicentre study on antibiotic susceptibilities of anaerobic bacteria to cefoperazone-sulbactam and other antimicrobial agents.

The antibiotic susceptibilities of 241 anaerobic bacteria recovered from six geographic sites in North America were tested by agar dilution to cefoperazone-sulbactam and other drugs. Of the 189 Bacteroides fragilis group isolates, only one was resistant to cefoperazone-sulbactam (0.5%) or ampicillin-sulbactam (0.5%), and none was resistant to ticarcillin-clavulanate or chloramphenicol. No resistance to cefoperazone-sulbactam was observed among the other Bacteroides spp., Clostridium spp., or Peptostreptococcus spp. Resistance to cefoperazone-sulbactam is not commonly observed against anaerobic bacteria recovered from different geographical sites across North America.

Comparison of acridine orange stain with culture and gram stain of needle aspirate in experimental Pseudomonas pneumonia.

The sensitivity and specificity of culture, acridine orange stain, and Gram stain were determined using needle aspiration (NA) material obtained from 82 rats with acute Pseudomonas aeruginosa pneumonia and 18 control rats. Lungs were then processed for either bacterial quantitation or histopathologic examination. NA culture proved to be the most sensitive and specific (55 and 100%, respectively). Sensitivity of acridine orange stain was 40%, whereas Gram stain was only 29%. The specificity of each stain was at least 94%. Lung bacterial concentrations influenced the sensitivities of all three techniques, with better sensitivity found in NA samples obtained from lung with bacterial concentration of at least 10(4) colony-forming units (cfu) of P. aeruginosa. Acridine orange and Gram stain results were similar except in NA samples from lung with bacterial concentration of less than 10(4) cfu in which acridine orange stain was more sensitive. The presence of stains identifying bacteria collected from animals with sterile NA culture was found in a small but significant number of samples, suggesting the presence of nonviable though stainable organisms. Use of all three techniques (culture, acridine orange stain, and Gram stain) increased sensitivity to approximately 70% with minimal decrease of specificity.

Adherence of group A streptococci to human epithelial cells.

The adherence of group A streptococci to epithelial cells was studied by using streptococcal strains labeled with [(3)H]uridine or fluorescein isothiocyanate. The ability of the labeled organisms to adhere to Detroit 562 epithelial cells, derived from a human pharyngeal carcinoma, as well as to epithelial cells scraped from the oral cavity was determined. Adherence to monolayer cultures or cell suspensions of Detroit cells compared favorably with adherence to suspensions of human oral epithelial cells. Initial experiments to determine the optimal conditions for adherence showed that adherence was temperature dependent and that the optimal incubation time was 15 min for adherence to epithelial cells in suspension and 30 to 60 min for monolayer cultures. Both streptococci and epithelial cells exhibited specificity in the adherence process. Different streptococcal strains varied in their ability to adhere. Adherence was also affected by the growth stage of the bacterial cultures. Trypsin treatment of the streptococci slightly decreased adherence, whereas hyaluronidase treatment increased the adherence of some strains. Streptococci were found to adhere to only about half of the epithelial cells. Those epithelial cells apparently have a limited number of receptor sites since they can be saturated by adding increasing concentrations of bacteria. Further support for limited receptor sites was provided by competition experiments. Adherence was inhibited by trypsin treatment of the epithelial cells, suggesting that proteins in the epithelial cell membrane may play a role in streptococcal adherence.