β-lactam antibiotic used to treat bacterial infections caused by susceptible
Mode of action Amoxicillin acts by inhibiting the synthesis of bacterial cell walls. It inhibits cross-linkage between the linear peptidoglycan polymer chains that make up a major component of the cell wall of Gram-positive bacteria. microorganisms. It is usually the drug of choice within the class because it is better absorbed, following oral administration, than other beta-lactam antibiotics. Amoxicillin is susceptible to degradation by β-lactamase-producing bacteria, and so is often given clavulanic acid.
Microbiology Amoxicillin is a moderate-spectrum antibiotic active against a wide range of Gram-positive, and a limited range of Gram-negative organisms
Susceptible Gram-positive organisms : Streptococcus spp., Diplococcus pneumoniae, non β-lactamase-producing Staphylococcus spp., and Streptococcus faecalis.
Susceptible Gram-negative organisms Haemophilus influenzae, Neisseria gonorrhoeae, Neisseria meningitidis, Escherichia coli, Proteus mirabilis and Salmonella spp.
Resistant organisms Penicillinase producing organisms, particularly penicillinase producing Staphylococcus spp. Penicillinase-producing N. gonorrhoeae and H. influenzae are also resistant
All strains of Pseudomonas spp., Klebsiella spp., Enterobacter spp., indole-positive
Proteus spp., Serratia marcescens, and Citrobacter spp. are resistant.
The incidence of β-lactamase-producing resistant organisms, including E. coli, appears to be increasing.
Amoxicillin and Clavulanic acid Amoxicillin is sometimes combined with clavulanic acid, a β-lactamase inhibitor, to increase the spectrum of action against
Gram-negative organisms, and to overcome bacterial antibiotic resistance mediated through β-lactamase production.
Quinolones and fluoroquinolones form a group of broad-spectrum antibiotics. They are derived from nalidixic acid.
Fluoroquinolone antibiotics are highly potent and considered relatively safe.
MOA : Quinolones act by inhibiting the bacterial DNA gyrase enzyme. This way they inhibit nucleic acid synthesis and act bacteriocidically.
Drugs :Nalidixic acid, Ciprofloxacin , Levofloxacin, Norfloxacin ,Ofloxacin, Moxifloxacin , Trovafloxacin
Gentamicin is a aminoglycoside antibiotic, and can treat many different types of bacterial infections, particularly Gram-negative infection.
Gentamicin works by binding to a site on the bacterial ribosome, causing the genetic code to be misread.
Like all aminoglycosides, gentamicin does not pass the gastro-intestinal tract, so it can only be given intravenously or intramuscularly.
Gentamicin can cause deafness or a loss of equilibrioception in genetically susceptible individuals. These individuals have a normally harmless mutation in their DNA, that allows the gentamicin to affect their cells. The cells of the ear are particularly sensitive to this.
Gentamicin can also be highly nephrotoxic, particularly if multiple doses accumulate over a course of treatment. For this reason gentamicin is usually dosed by body weight. Various formulae exist for calculating gentamicin dosage. Also serum levels of gentamicin are monitored during treatment.
E. Coli has shown some resistance to Gentamicin, despite being gram-negative
Clarithromycin Used to treat pharyngitis, tonsillitis, acute maxillary
sinusitis, acute bacterial exacerbation of chronic bronchitis, pneumonia (especially atypical pneumonias associated with Chlamydia pneumoniae or TWAR), skin and skin structure infections, and, in HIV and AIDS patients to prevent, and to treat, disseminated Mycobacterium avium complex or MAC.
Unlike erythromycin, clarithromycin is acid-stable and can therefore be taken orally without being protected from gastric acids. It is readily absorbed, and diffused into most tissues and phagocytes.
Clarithromycin has a fairly rapid first-pass hepatic metabolism, i.e it is metabolised by the liver. However, this metabolite, 14-hydroxy clarithromycin is almost twice as active as clarithromycin.
Contraindications Clarithromycin should be used with caution if the patient has liver or kidney disease, certain heart problems (e.g., QTc prolongation or bradycardia), or a mineral imbalance (e.g., low potassium or magnesium levels).
Produced semisynthetically by chemical attachment of side chains to 7-aminocephalosporanic acid. Same mode of action , same resistance mech.
But tend to be more resistant than penicillins to certain beta –lactamases .
GENERATION BASED ON :
-- BACTERIAL SUSCEPTIBILITY PATTERNS
-- RESISTANCE TO BETA –LACTAMASES
--NOT EFFECTIVE AGAINST -MRSA , L. MONOCYTOGENES , C. DIFFICLE , ENTEROCOCCI
Procaine penicillin Procaine penicillin is a combination of benzylpenicillin with the local anaesthetic agent procaine. This combination is aimed at reducing the pain and discomfort associated with a large intramuscular injection of penicillin.
respiratory tract infections where compliance with oral treatment is unlikely ,syphilis, cellulitis