Trimethoprim (TMP) is an antibiotic is used for the treatment of initial episodes of uncomplicated urinary tract infections due to susceptible strains of the following organisms: Escherichia coli, Proteus mirabilis, Klebsiella pneumoniae, Enterobacter species, and coagulase-negative Staphylococcus species, including S. saprophyticus. Cultures and susceptibility tests should be performed to determine the susceptibility of the bacteria to trimethoprim. Therapy may be initiated prior to obtaining the results of these tests. Trimethoprim is rapidly absorbed following oral administration. It exists in the blood as unbound, protein-bound, and metabolized forms. Ten to twenty percent of trimethoprim is metabolized, primarily in the liver; the remainder is excreted unchanged in the urine. The principal metabolites of trimethoprim are the 1- and 3-oxides and the 3'- and 4'-hydroxy derivatives. The free form is considered to be the therapeutically active form. Approximately 44% of trimethoprim is bound to plasma proteins. Trimethoprim blocks the production of tetrahydrofolic acid from dihydrofolic acid by binding to and reversibly inhibiting the required enzyme, dihydrofolate reductase. This binding is very much stronger for the bacterial enzyme than for the corresponding mammalian enzyme

Clindamycin hydrochloride is the hydrated hydrochloride salt of clindamycin. Clindamycin is a semisynthetic antibiotic produced by a 7(S)-chloro-substitution of the 7(R)-hydroxyl group of the parent compound lincomycin. Clindamycin inhibits bacterial protein synthesis by binding to the 50S subunit of the ribosome. It has activity against Gram-positive aerobes and anaerobes as well as some Gram-negative anaerobes.

Sulfamethoxazole is a synthetic antibacterial drug,which is used in combination with trimethoprim (Bactrim, Septra) for the treatment or prevention of infections that are proven or strongly suspected to be caused by bacteria. Sulfamethoxazole acts by inhibiting folic acid synthesis via enzyme called dihydropteroate synthase.

Vancomycin is a branched tricyclic glycosylated nonribosomal peptide produced by the fermentation of the Actinobacteria species Amycolatopsis orientalis (formerly Nocardia orientalis). Vancomycin became available for clinical use >50 years ago. It is often reserved as the "drug of last resort", used only after treatment with other antibiotics had failed. Vancomycin has been shown to be active against most strains of the following microorganisms, both in vitro and in clinical infections: Listeria monocytogenes, Streptococcus pyogenes, Streptococcus pneumoniae (including penicillin-resistant strains), Streptococcus agalactiae, Actinomyces species, and Lactobacillus species. The combination of vancomycin and an aminoglycoside acts synergistically in vitro against many strains of Staphylococcus aureus, Streptococcus bovis, enterococci, and the viridans group streptococci. The bactericidal action of vancomycin results primarily from inhibition of cell-wall biosynthesis. Specifically, vancomycin prevents the incorporation of N-acetylmuramic acid (NAM)- and N-acetylglucosamine (NAG)-peptide subunits from being incorporated into the peptidoglycan matrix; which forms the major structural component of Gram-positive cell walls. The large hydrophilic molecule is able to form hydrogen bond interactions with the terminal D-alanyl-D-alanine moieties of the NAM/NAG-peptides. Normally this is a five-point interaction. This binding of vancomycin to the D-Ala-D-Ala prevents the incorporation of the NAM/NAG-peptide subunits into the peptidoglycan matrix. In addition, vancomycin alters bacterial-cell-membrane permeability and RNA synthesis. There is no cross-resistance between vancomycin and other antibiotics. Vancomycin is not active in vitro against gram-negative bacilli, mycobacteria, or fungi.

FLOPRISTIN is one of the components of the experimental drug NXL103 (XRP 2868), along with linopristin. Both are semi-synthetic streptogramin antibiotics derived from the Streptomyces genus. NXL103 has a spectrum of antibacterial activity that indicates it has the potential to be effective in the treatment of skin and skin structure infections, including those caused by methicillin-resistant Staphylococcus aureus, as well as community-acquired pneumonia. NXL103 has completed Phase II trials.

Evernimicin (SCH 27899) is an oligosaccharide antibiotic. It nteracts with the large ribosomal subunit (50S) and inhibits bacterial protein synthesis. Evernimicin exerts activity against a wide spectrum of gram-positive bacteria and activity against some gram-negative bacteria. Evernimicin was being studied for the treatment of susceptible bacterial infections however its development has been discontinued.

Lotilibcin (WAP-8294A2) is an antibiotic originally isolated from Lysobacter sp. It is active against methicillin-resistant gram-positive bacteria. Lotilibcin antimicrobial activity is due to lysis of the bacterial membrane, and its membrane-disrupting effect depends on the presence of menaquinone, an essential factor for the bacterial respiratory chain. It was developing for the treatment of susceptible bacterial infections

MRX-I is a potent oxazolidinone antibiotic against Gram-positive pathogens, including methicillin-resistant Staphylococcus aureus, penicillin-resistant Streptococcus pneumoniae, penicillin-intermediate S. pneumoniae, and vancomycin-resistant enterococci. MRX-I demonstrated comparable or slightly higher activity than linezolid and was active against enterococci resistant to both vancomycin and teicoplanin. In addition, MRX-I exhibited bactericidal activities against staphylococci and streptococci but was bacteriostatic against enterococci. MRX-I inhibits formation of functional 70S initiation complex essential for bacterial protein synthesis, leading to the cessation of bacterial growth. Oral MRX-I was associated with a greater bioavailability and exposure when administered with food, and minimal accumulation of MRX-I occurred after multiple-dose administration. Oral MRX-I was well tolerated at single doses of up to 1,200 and 800 mg q12h for up to 28 days; all adverse events were mild to moderate in severity, and there was no drug discontinuation due to adverse events.

Exeporfinium (XF-73), a dicationic porphyrin derivative, is an antibacterial drug. Exeporfinium acts via a bacterial cell-surface mechanism that affects membrane permeability and integrity, leading to release of intracellular components and bacterial cell death, without lysis. Exeporfinium represents a broad-spectrum Gram-positive antibacterial drug. It also has activity against a number of Gram-negative bacteria. Exeporfinium has been granted Fast Track designation by the US FDA for the prevention of post-surgical staphylococcal infections such as Methicillin Resistant Staphylococcus aureus.

Gepotidacin (formerly GSK2140944) is a novel, first-in-class, triazaacenaphthylene antibacterial that selectively inhibits bacterial DNA gyrase and topoisomerase IV by a unique mechanism, one that is not utilized by any currently approved human therapeutic agent. As a consequence of its novel mode of action, gepotidacin is active in vitro against target pathogens carrying resistance determinants to established antibacterials, including fluoroquinolones. Gepotidacin has demonstrated in vitro activity against key pathogens, including drug-resistant strains, associated with a range of conventional and biothreat infections. GlaxoSmithKline is developing Gepotidacin for the treatment of gonorrhoea and skin and soft tissue infections.