Chemo Penicillins Are Antibiotics Derived From the Essay

Chemo

Penicillins are antibiotics derived from the Penicillium mold. They are classified as beta-lactam antibiotics because of their fused beta-lactam structure. They also have a free carboxyl acid group, and one or more substituted amino acid side chains (Ophardt, 2003). Their primary mode of action is to inhibit bacterial cell wall synthesis by preventing the cross linking of peptides on the mucosaccharide chains, thereby causing the bacterial cells to inundate with water and burst (Ophardt, 2003). Penicillin is not a singular compound, hence the term "penicillins," referring to compounds that share a ring-like structure, and which are derived from two amino acids (valine and cysteine) via a tripeptide intermediate," (The Microbial World, n.d.).

Some penicillins are relatively limited in their scope, are used to treat mild or moderate infections. The development of resistance in target microorganisms, coupled with the tendency for some patients to be allergic to penicillins, also renders these classic antibiotics relatively limited in their overall effectiveness in clinical use. The most common types of naturally occurring penicillins include Penicillium notatum, the closely related species P. chrysogenum like penicillin G, and the more acid-resistant penicillin V. These are most effective against Gram-positive bacteria, which are characterized by the unique qualities of their cellular walls. They are not, however, effective against Gram-negative strains including those like Mycobacterium tuberculosis (The Microbial World, n.d.). However, a range of semi-synthetic penicillins has been developed, such as Ampicillin, Carbenicillin (see diagram) and Oxacillin. These have specific targeted actions and can be effective for some Gram-negative bacteria. The adverse effects of penicillins include the inability of some people to digest them, leading to mild diarrhea, headaches, and sore mouths. Other side effects are relatively common, and there may be more severe reactions to penicillin including rashes or joint pain ("Penicillin Side Effects," n.d.).

2. Gentamicin is part of the aminoglycoside class of antibiotics, and is one of the most frequently prescribed in the family along with tobramycin and amikacin (Drew, 2014). The aminoglycosides work by interrupting peptide synthesis and thus disrupting the ability of the bacilli to accurately translate their genes. At the microbial level, gentamicin does this specifically by binding with the "aminoacyl site of 16S ribosomal RNA within the 30S ribosomal subunit, leading to misreading of the genetic code and inhibition of translocation," (Drew, 2014). Gentamicin also inhibits oxygen transport in target organisms and causes anaerobiasis (Itokazu, n.d.). Gentamicin also prevenst the biosynthesis of DNA present in the proteins of Staphylococcus aureus (Abou-Zeid, Eissa & Salem, 1978).

Gentamicin and other aminoglycosides are indicated for serious infections caused by Gram-negative bacilli and highly resistent infections such as those acquired in hospital. However, the aminoglycosides are broad-spectrum antibiotics that can in some cases be recommended in patients with gram-positive infections. The primary problem with gentamicin is the potential for toxicity. The effectiveness of the antibiotic is increased in higher doses, but Gentamicin is known to cause nephrotoxicity, ototoxicity, as well as liver disease. Some of the ill effects, particularly with nephrotoxicity, are reversible. However, ototoxicity, particularly vestibular and auditory issues, are major problems and irreversible (Itozaku, n.d.). Other adverse effects of gentamicin include tinnitus, headache, nausea, and vomiting (Itozaku, n.d.). Length of therapy and dosage are considerations, and both should be minimized when possible. Because of its toxicity, gentamicin is indicated primarily in life-threatening situations.

3. Azithromycin is part of the azalide class of macrolide antibiotics, and is chemically related to erythromycin. Its mechanism of action is to inhibit bacterial protein synthesis by binding to specific ribosomes, thereby inhibiting peptidyl transferase activity, interfering with amino acid translocation during translation, and preventing the growth and reproduction of the organism ("Azithromycin," n.d.). Depending on the target organism, the effects are bacteriostatic or bactericidal. It is not indicated for any viral infections. Azithromycin does not inhibit the protein synthesis in healthy cells, but the substance does linger in the body a long time. Thus, azithromycin is typically administered in less frequent doses, or with shorter dosage duration, versus other antibiotics ("Zaiqi Granules," n.d.). Azithromycin is processed and eliminated primarily in the liver.

Azithromycin is effective in treating infections of Hemophilus influenzae, Streptococcus pneumoniae, Mycoplasma pneumoniae, Staphylococcus aureus, and mycobacterium avium, and many other organisms ("Zaiqi Granules," n.d). Typical indications for the administration of azithromycin include pneumonia due to Streptococcus pneumoniae, Haemophilus influenzae or mycoplasma pneumonia, some types of urethritis, nasosinusitis, tympanitis, acute bronchitis, cervicitis,, and acute tonsillitis that has caused acute pharyngitis or acute amygdalitis ("Zaiqi Granules," n.d.). Because azithromycin is processed and eliminated primarily in the liver, it is contraindicated in persons with hepatic diseases. Diarrhea and loose stool, along with other digestive issues, are the most common side effects.Nervousness has also been reported ("Zaiqi Granules," n.d.). More serious adverse effects include cracked skin, fever, and blisters. However, azithromycin is "generally well tolerated" and has few interactions with other medications ("Zaiqi Granules," n.d., p. 2).

4. Doxycycline is a member of the tetracycline family. It is a synthetic derivative of oxytetracycline. It has broad-spectrum antibacterial actions, and is effective against both gram-negative and gram-positive organisms ("Doxycycline," n.d.). Doxycycline works by inhibiting protein synthesis in target microorganisms, by binding to the 30S ribosomal subunit. It is primarily bacteriostatic in its action.

The most common therapeutic indications include respiratory infections such as sinusitis, chronic bronchitis, and various types of pneumonia infection including Mycoplasma pneumoniae pneumonia, Streptococcus pneumoniae, Haemophilia influenzae, and Klebsiella pneumonia. Doxycycline is also effective in killing bacteria causing urinary tract infections including Klebsiella species, Enterobacter species, Escherichia coli, Streptococcus faecalis and other organisms (Actavis, n.d.). It can also be used for some types of sexually-transmitted disease including Chlamydia trachomatis and Calymmatobacterium granulomatis. Doxycycline can be used to treat Rocky mountain spotted fever, plague, cholera, anthrax, typhus fever, malaria and the typhus group ("Doxycycline," n.d.).

Adverse effects from taking doxycycline include headache, dizziness, blurred vision, chills, diarrhea, jaundice, loss of appetite, vaginal discharge, and upset stomach. However, the prevalence of specific side effects is not well-known, meaning patients should report all side effects to their physician immediately. Doxycycline is generally not recommended for children or pregnant women. Because of its broad spectrum application, though, doxycycline has an abundance of clinical uses and potential in a number of disease scenarios.

5. Co-trimoxazole is the combination of trimethoprim with sulfamethoxazole, usually in a 1:5 ratio ("Trimethoprim," n.d.). Trimethoprim belongs to the family of dihydrofolate reductase inhibitors, is a pyrimidine inhibitor of dihydrofolate reductase, and interfers with folic acid metabolism ("Trimethoprim," n.d.). Sulfamethoxadole is a sulfonamide. Collectively, co-trimoxadole is classified as a sulfomamide as well and likewise works on the mechanism of inhibiting folate synthesis in a way that causes bacteriocide. It also competes with PABA and "blocks production of tetrahydrofolic acid by inhibiting the enzyme dihydrofolate reductase," ("Trimethoprim/Sulfamethoxazole," n.d.). Brand names include Bactrim, Bactrim DS, Septra, Septra DS, Sulfatrim ("Co-trimoxazole," n.d.).

Clinical uses for cotrimoxazole are varied and diverse, including types of urinary tract infections, shigellosis enteritis, Pneumocystis carinii pneumonitis, acute otitis (particularly those caused by Streptococcus pneumoniae or Haemophilus influenzaemedia), acute exacerbations of chronic bronchitis, gastro-intestinal infections like traveler's diarrhea, and even some types of cholera ("Trimethoprim/Sulfamethoxazole," n.d.). Cotrimoxazole is not a "drug of first choice," because it is known to present serious side effects ("Co-trimoxazole," n.d.). Moreover, bacilli resistant to amoxicillin are usually also resistant to co-trimoxazole. Cotrimoxazole is occasionally, but cautiously, recommended as a prophylactic for travelers visiting regions where they may be exposed to pathogens like Escherichia coli. However, resistance is common. Resistance is also relatively common when a traveler It is contraindicated in young children ("Co-trimoxazole," n.d).

Adverse effects of cotrimoxazole include stomach pain or tenderness, vomiting, loss of appetite, chest pain, constipation, gas, and emotional effects like depression, nervousness, and irritability ("Co-trimoxazole," n.d).

6. Ciprofloxacin hydrochloride, commonly called Cipro, works by inhibiting DNA replication, transcription, repair, and recombination in bacteria, by inhibiting enzymes like topoisomerases ("Cipro," n.d.). Thus, ciprifoxacin works entirely differently from other antibiotics and can be especially useful when other antibiotics have proven ineffective. There are also no known cross-resistances between ciprofloxacin and other antimicrobials ("Cipro," n.d.). It can be used for both gram-negative and gram-positive bacteria.

Common clinical uses for ciprofloxacin include Staphylococcus aureus (methicillin-susceptible isolates only), Staphylococcus epidermidis (methicillin-susceptible isolates only), Staphylococcus saprophyticus, Streptococcus pneumonia, Campylobacter jejuni, and Proteus mirabilis ("Cipro," n.d.). Therefore, urinary tract infections, cystitis in females, lower respiratory tract infections, sinusitis, and some types of infectious diarrhea are common indications. Cipro can also be prescribed in prostatitis and anthrax.

Ciprofloxacin is potent, not recommended for children generally, and is not typically a drug of first choice. Adverse reactions include headache, insomnia, dizziness, depression, and potential development of nephritis. Diarrhea is the most commonly reported side effect, and most of the side effects do vanish once the drug has left the system. Serious side effects have been reported with ciproflaxin, which is why milder antibiotics would generally be preferred.

References

Actavis (n.d.). Doxycycline capsules. http://www.medicines.org.uk/EMC/medicine/23949/SPC/Doxycycline+Capsules+BP+50mg/

Abou-Zeid AA, Eissa AI, Salem HM. (1978). Mode of action of gentamicin antibiotics produced by Micromonospora purpurea. Zentralbl Bakteriol Naturwiss. 1978;133(4):362-8.….....