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Mersacidin is a new peptide antibiotic of the proposed lantibiotic family. It is active in vitro and in vivo against Gram-positive bacteria including the methicillin-resistant Staphylococci. Its in vitro activity is less than those of vancomycin and erythromycin but it shows much higher activity in the in vivo system than can be expected from the in vitro testing results. A water soluble potassium salt has been prepared which has an activity profile similar to that of mersacidin, but has better in vivo activity against Streptococcus pyogenes than the parent compound.

Desacetyl-cefotaxime, the main metabolite of cefotaxime, possesses a broad antibacterial spectrum. Its activity is lower than that of cefotaxime, but significantly surpasses that of cefazolin against gram-negative bacteria. The beta-lactamase stability of desacetyl-cefotaxime is higher than that of the parent compound. This beta-lactamase stability might be responsible for the synergistic effects of cefotaxime and desacetyl-cefotaxime occasionally seen in in vitro combination studies.

The in vitro and in vivo activity of ofloxacin (DL 8280, HOE 280) was compared with that of other antibacterial compounds. Ofloxacin was found to have a broad antibacterial spectrum which includes both gram-positive and gram-negative aerobic and anaerobic species. Its activity is generally higher than that of pipemidic acid and nalidixic acid. Against staphylococci and streptococci, ofloxacin proved to be more active than norfloxacin. In the case of Enterobacteriaceae and Pseudomonadaceae, ofloxacin and norfloxacin possess comparable activities. Ofloxacin was the most active compound against a number of aerobic isolates which are resistant to cefotaxime and ceftriaxone. Of the compounds compared, ofloxacin was the only one which exhibited reasonable activity against anaerobes. It inhibited all strains of Bacteroides fragilis at a concentration of 3.125 mg/l and the gram-positive anaerobes at 0.5 mg/l. In mice experimentally infected with various gram-positive and gram-negative bacteria, ofloxacin was more active than norfloxacin and pipemidic acid. With the gram-negative pathogens, orally administered ofloxacin was as active as gentamicin used parenterally. We conclude from our studies that ofloxacin could be a valuable therapeutic agent with a variety of indications.

Like all other cephalosporins that contain an acetyl side chain in the 3' position, cefotaxime (CTX) is partially desacetylated in vivo. Desacetylcefotaxime (des-CTX) possesses a broad antimicrobial spectrum and high beta-lactamase stability. With the exception of Pseudomonas aeruginosa, Morganella morganii, Bacteroides fragilis, and Staphylococcus aureus, most strains of other species tested usually had mean MICs of des-CTX lower than 1 microgram/ml. Its activity is generally lower than that of the parent compound. It was only against some strains of P. cepacia that des-CTX surpassed the activity of CTX. The activity of des-CTX markedly exceeds the activity of many therapeutically used cephalosporins. This is especially true for Haemophilus influenzae, Neisseria meningitidis, most species of Enterobacteriaceae, and streptococci other than Streptococcus faecalis.

The antibacterial activity of Ofloxacin (DL 8280, Hoe 280 Tarivid) against Ampicillin-resistant clinical isolates was compared to, Penicillin V, Tetracyclin-HCl, Cefalexin, Cefaclor, Co-trimoxazole and nalidixic acid. Ofloxacin proved to be the most active compound against all species tested.

3-[(2,3-Cyclopenteno-1-pyridinium)-methyl]-7-[2-syn-methoximino-2-(2-aminothiazol-4-yl)-acetamido]-ceph-3-em-4-carboxylate (HR 810) is a new cephalosporin derivative with an extremely broad antimicrobial spectrum. It is active against all bacterial species of clinical relevance, including strains which are frequently resistant towards cephalosporins of the third generation.

The antibacterial activity of the cephalosporin antibiotic HR 810 was evaluated in comparison with cefoperazone, cefotaxime, ceftazidime, ceftriaxone, latamoxef, gentamicin and amikacin against 1500 clinical isolates. HR 810 is the antibiotic with the broadest antimicrobial spectrum. It is also highly active against isolates of the genera Pseudomonas, Enterobacter, Staphylococcus and enterococci. HR 810 is very stable against hydrolysis by plasmid-coded and chromosomally coded beta-lactamases.