The effects of intravenous erythromycin and josamycin on gastrointestinal motility in dogs have been compared. Erythromycin interrupted the basal motility pattern in the fasted state and induced irregular bursts of spikes in both the fasted and fed states. Emesis occurred in all the dogs in the fasted state experiments and in four out of six dogs in the fed state experiments. Josamycin did not disturb gastrointestinal motility and no dog showed signs of discomfort. The difference in the chemical structure of erythromycin and josamycin is the main reason for their differential effect on the gastrointestinal tract.

Lipopolysaccharide (LPS) extracts of reference strains and isolates of Bacteroides spp. prepared by the proteinase K method were resolved by tricine-sodium-dodecyl-sulphate-polyacrylamide gel electrophoresis and located by silver staining. A considerable diversity of LPS profiles was evident within the Bacteroides genus although profiles were essentially species-specific, with some minor interstrain variations apparent among isolates of B. uniformis, B. ovatus, B. eggerthii and B. thetaiotaomicron. The LPS of most species consisted of a major rough LPS component of 2-5 kDa and a series of higher molecular weight bands which varied with species. B. vulgatus LPS was distinctive in showing an extensive ladder of multiple repeating oligosaccharide units with molecular weights ranging from 4 to > 17 kDa B. stercoris LPS included a high molecular weight (> 17 kDa) ladder of repeating oligosaccharide units. B. fragilis and B. thetaiotaomicron differed from most other species in producing a short ladder of repeating oligosaccharide units interspersing the rough LPS and a 5.6 kDa (B. fragilis) or 9 kDa (B. thetaiotaomicron) yellow-staining component. The heterogeneity of LPS profiles within the Bacteroides genus may reflect the differences in pathogenicity among the species and prove useful for typing.

We have studied the in-vitro activity of erythromycin, vancomycin and pristinamycin against 1,006 clinical isolates comprising streptococci, staphylococci, Neisseria gonorrhoeae, Haemophilus influenzae and anaerobes. In-vitro studies show pristinamycin to inhibit staphylococci and streptococci, including erythromycin highly-resistant organisms, at a concentration of less than or equal to 0.78 mg/l. Although pristinamycin's mean MIC for streptococci is higher than that of erythromycin, pristinamycin is bactericidal, whereas erythromycin is bacteristatic against Streptococcus agalactiae and oral streptococci. Enterococci were less uniformly susceptible to pristinamycin: 58 of the 94 Enterococcus faecalis tested were resistant (MIC greater than or equal to 3.12 mg/l). 14 of the 15 isolates of Enterococcus faecium were inhibited by less than or equal to 1.56 mg/l pristinamycin. Pristinamycin showed poor activity against Haemophilus influenzae (mode MIC 1.56 and MIC90 of 3.12 mg/l) but all except two of the 100 Neisseria gonorrhoeae tested were inhibited by less than or equal to 0.78 mg/l pristinamycin. Pristinamycin inhibited all nine Clostridium spp. at less than or equal to 0.39 mg/l and 38 of 40 strains of anaerobic gram-positive cocci at less than or equal to 0.78 mg/l. It was less effective against the Bacteroides fragilis group: (MIC90 3.12 mg/l). Pristinamycin had poor bactericidal activity against the anaerobes tested.

The in vitro activity of lomefloxacin, a new difluorinated quinolone, was compared to that of ciprofloxacin, ofloxacin, norfloxacin and other relevant antibacterial agents. Lomefloxacin and norfloxacin shared similar activity, whereas ofloxacin and in particular ciprofloxacin showed superior activity. Most gram-negative aerobes were susceptible to all four quinolones, 90% of isolates were inhibited by 1 mg/l. The gram-positive organisms were generally less susceptible, although 90% of Staphylococcus aureus isolates were inhibited by 0.5 mg/l of ciprofloxacin and ofloxacin; values for lomefloxacin and norfloxacin were 1 mg/l and 2 mg/l, respectively; susceptibility was not affected by methicillin resistance. Neisseria gonorrhoeae and Haemophilus influenzae were highly susceptible to the quinolones, especially ciprofloxacin. Penicillin/ampicillin-resistant isolates remained susceptible to the quinolones.