Clofoctol [2-(2,4-dichlorobenzyl)-4-(tetramethyl-1,1,3,3-butyl)phenol] is a synthetic antibacterial agent with bactericidal activity on various Gram-positive (especially S. pyogenes and S. pneumoniae, but also Corynebacterium spp. and Propionibacterium acnes) and some Gram-negative bacteria (including Haemophilus influenzae, Bordetella spp., Neisseria meningitides, and Neisseria gonorrhea). A peculiar property of clofoctol is the rapidity of the antimicrobial effect, similar to that of antiseptic compounds, which makes the development of resistance less likely. Following rectal administration of clofoctol, absorption is rapid and nearly complete (about 98%), with a good penetration in the lung tissue. Clofoctol is primarily metabolized by hepatic glucuronidation and excreted through the biliary system; renal elimination is negligible. Clofoctol compound has been used mainly in France (under the trade name Octoplus ) and Italy (as Gramplus) for the treatment of mild upper respiratory tract infections, especially in pediatric patients

Penimepicycline is a salt of beta-lactam antibiotic penicillin V and tetracycline antibiotic pipacycline. Penimepicycline exerts a bactericidal action on the streptococci, and a bacteriostatic action on various gram-positive and gram-negative bacilli, as well as on the penicillin-resistant staphylococci. In the 1960s it was studied in Japan for the treatment of urological, respiratory, gynecological and other infections.

Flumequine is a synthetic antibiotic, which used to treat urinary tract infections until toxicity studies were reported. Flumequine inhibits bacterial enzyme DNA gyrase (topoisomerase) that is responsible for the supercoiling of DNA, thus bacterial cell growth disrupted by inhibiting nucleic acid synthesis.

Flucloxacillin is an isoxazolyl penicillin of the β-lactam group of antibiotics, which exerts a bactericidal effect upon many Gram-positive organisms including β-lactamase-producing staphylococci and streptococci. While no longer used in the United States, Flucloxacillin is supplied under a variety of trade names in other countries, including Floxapen, Flopen, Staphylex. Floxapen is indicated for the treatment of infections due to sensitive Gram-positive organisms, including β-lactamase-producing staphylococci and streptococci. Typical indications including, skin and soft tissue infections; respiratory tract infections; other infections caused by floxapen-sensitive organisms, like example, osteomyelitis, urinary tract infection, septicaemia, endocarditis. Floxapen is also indicated for use as a prophylactic agent during major surgical procedures when appropriate; for example cardiothoracic and orthopaedic surgery. Flucloxacillin, by its action on the synthesis of the bacterial wall, exerts a bactericidal effect on streptococci except those of group D (Enterococcus faecalis) staphylococci. It is not active against methicillin-resistant staphylococci. There is evidence that the risk of flucloxacillin induced liver injury is increased in subjects carrying the HLA-B*5701 allele. Despite this strong association, only 1 in 500-1000 carriers will develop liver injury. Consequently, the positive predictive value of testing the HLA-B*5701 allele for liver injury is very low (0.12%) and routine screening for this allele is not recommended. Flucloxacillin diffuses well into most tissue. Specifically, active concentrations of flucloxacillin have been recovered in bones: 11.6 mg/L (compact bone) and 15.6 mg/L (spongy bone), with a mean serum level of 8.9 mg/L. Flucloxacillin diffuses in only small proportion into the cerebrospinal fluid of subjects whose meninges are not inflamed. It is also excreted in small quantities in mother's milk. In normal subjects approximately 10% of the flucloxacillin administered is metabolised to penicilloic acid. The elimination half-life of flucloxacillin is in the order of 53 minutes.

Garenoxacin is an antibacterial agent active against a range of aerobic Gram-positive and Gram-negative bacteria. It exerts its action by inhibiting bacterial DNA gyrase and topoisomerase IV. The drug was withdrawn from the market in Europe and was never approved in the USA. Garenoxacin is still marketed in Japan under the name Geninax.

Rokitamycin is a macrolide antibiotic against Gram-positive bacteria. Synthesized from strains of Streptomyces kitasatoensis. Rokitamycin is an inhibitor of protein synthesis by specifically binding to the 50 S subunit of the ribosome. Specificity towards prokaryotes relies upon the absence of 50S ribosomes in eukaryotes.

Iclaprim is an investigational broad-spectrum diaminopyrimidine antibiotic in development for the treatment of acute bacterial skin and skin structure infections (ABSSSIs). Iclaprim acts on bacterial cells by competitively inhibiting dihydrofolate reductase (DHFR), a key enzyme in the folate cycle; the same mode of inhibition is exerted by trimethoprim. Iclaprim resistance is mainly determined by point mutations in the dfr gene as studied in S. aureus and S. pneumoniae. Surveillance studies demonstrate that the spectrum of activity of iclaprim includes many organisms indicated in cSSSI including S. aureus and S. pyogenes. Iclaprim is bactericidal in vitro, generally at concentrations equal to the MIC that are maintained in human plasma for several hours after a therapeutic dose. Bactericidal activity is primarily time-dependent and concentration independent. Due to its structural similarity with trimethoprim, iclaprim is synergistic with sulfonamides against a broad spectrum of bacterial species. The antimicrobial mechanism of action of iclaprim is mediated by competitive inhibition of bacterial DHFR, the same mode of inhibition exerted by TMP. The activity of iclaprim against TMP-R mutants of S. aureus and S. pneumoniae is attributable to additional hydrophobic interaction between iclaprim and the enzyme. The same mechanism of action of iclaprim, competitive inhibition with the natural substrate DHF, is seen against both TMP-S and -R enzymes. Iclaprim is well suited for use as a first-line empiric monotherapy in patients with ABSSSI who are comorbid with renal impairment for the following reasons. n July 2015, the U.S. Food and Drug Administration, or FDA, designated the IV formulation of iclaprim as a Qualified Infectious Disease Product (QIDP) for ABSSSI and HABP. QIDP status grants iclaprim regulatory Fast Track designation, Priority Review and, if approved, a five-year extension to the statutory market exclusivity period in the United States, resulting in 10 years of market exclusivity from the date of approval.

Thiamphenicol is a broad-spectrum antibiotic, which is active against gram-positive and gram-negative organisms. The drug is marketed in Asia and Latin America for the treatment of various infections, including sexually transmitted diseases. As many phenicols, thiamphenicol inhibits the protein synthesis in bacterias by binding to 23S ribosomal subunit. In Europe and USA the drug is used in a veterinary practice.

Cefozopran hydrochloride is a third-generation cephalosporin that was launched for the treatment of severe infections in immunocompromised patients caused by staphylococci and enterococci. While it shows a very broad antibacterial spectrum against Gram-positive and Gram-negative organisms, it is particularly potent against S. aureus, Enterococcus faecalis, P. aeruginosa, and Citrobacter freundii. It is resistant to hydrolysis by most chromosomal and plasmid mediated β-lactamases and is reported to be active against respiratory, urinary tract, obstetrical, gynecological, soft tissue, and surgical infections. Similar to β-lactams, cephalosporins interfere with PBP (penicillin binding protein) activity involved in the final phase of peptidoglycan synthesis. PBP’s are enzymes which catalyze a pentaglycine crosslink between alanine and lysine residues providing additional strength to the cell wall. Without a pentaglycine crosslink, the integrity of the cell wall is severely compromised and ultimately leads to cell lysis and death. Resistance to cephalosporins is commonly due to cells containing plasmid encoded β-lactamases.

Temocillin was marketed by Beecham Pharmaceuticals in the UK in the 1980s but achieved little commercial success and was withdrawn, though it remained available via the manufacturer’s medical department. Presently licensed to Eumedica, temocillin is being re-launched in the UK and Belgium for treating UTI, sepsis, and respiratory infections by ESBL (Extended-spectrum beta-lactamases) and AmpC-producing Enterobacteriaceae. It acts by inhibiting the synthesis of the peptidoglycan layer of bacterial cell walls. It irreversibly binds to the active site of specific transpeptidases and carboxypeptidases known as Penicillin Binding Proteins (PBP), preventing peptidoglycan production.