Antimicrobial Resistance and Penicillins

Antibiotics Overview

• Antibiotics are medicines used to kill or stop the growth of microbial life in the body
• The term antimicrobials is a broader definition, including medicines used for bacterial, viral, fungal, and parasitic infections

Bacteria Classification

• Aerobic and anaerobic bacteria
• Gram-positive and gram-negative bacteria
• Pathogenic and normal flora bacteria
• Bacteria identification methods: culture and sensitivity, serology, and polymerase chain reaction (PCR)

Antibiotic Resistance

• Antibiotic resistance occurs when microorganisms survive exposure to an antibiotic
• Causes more than 38,000 deaths in Thailand, 23,000 deaths in the US, and 25,000 deaths in the European Union each year
• Result of massive use of antibiotics, both appropriate and inappropriate, over the past 80 years

Mechanisms of Antibacterial Agents

• Inhibition of bacterial cell wall synthesis or activation of enzymes that disrupt cell walls (penicillins, cephalosporins, vancomycin)
• Inhibition of protein synthesis (tetracyclines, clindamycin, aminoglycosides)
• Inhibition of organism reproduction by interfering with nucleic acid synthesis (fluoroquinolones, HIV anti-retrovirals)
• Inhibition of cell metabolism and growth (sulfonamides)

Antibiotic Classification

Penicillins

• Derived from a fungus
• Widely distributed except in CSF (except if inflammation is present) and intraocular fluid
• More effective in treating gram-positive infections
• Used to treat infections of the skin, GU, GI, respiratory tract, and soft tissues
• Combinations for beta-lactamase inhibition (Augmentin)

Cephalosporins

• Derived from a fungus
• Broad-spectrum antibiotics with activity against both gram-positive and gram-negative bacteria
• Less active against gram-positive bacteria than penicillins
• Can't penetrate CSF well, except for Ceftin (cefuroxime) and 3rd generation agents
• Indications: surgical prophylaxis, infections of the respiratory tract, skin, bone, joints, urinary tract, brain, and spinal cord

Aminoglycosides

• Treat infections caused by gram-negative organisms such as Proteus, Klebsiella, Enterobacter, Escherichia coli, and Pseudomonas
• Poorly absorbed from the GI tract, causing local effects
• Accumulate in kidneys and ears
• Poorly distributed to CNS, respiratory tract, and intraocular fluid
• Nephrotoxic and ototoxic

Fluoroquinolones

• Synthetic bactericidal drugs with activity against gram-positive and gram-negative organisms
• Mechanism of action: interferes with DNA gyrase, an enzyme necessary for bacterial DNA synthesis
• May be used to treat respiratory, GU, GI, bone, joints, skin, and soft tissue infections

Tetracyclines

• Contraindicated in renal failure, except for doxycycline and minocycline
• Not indicated in children less than 8 years old because they can cause permanent discoloration of teeth and depress bone growth
• Can cause photosensitivity
• Avoid taking within 2 hours of dairy products, with iron, or with antacids

Miscellaneous Antibacterials

Chloramphenicol

• Broad-spectrum bacteriostatic antibiotic
• Used for gram-negative and gram-positive bacterial infections
• Indicated in meningococcal and pneumococcal infections

Clindamycin

• Similar in action to macrolides
• Effective against gram-positive cocci and pneumococci
• Great for acne and bacterial vaginosis

Vancomycin

• Active against gram-positive bacteria only
• Frequently used to treat MRSA
• Can cause hypotension, flushing, and skin rash if given too quickly, and "red man syndrome"

Metronidazole (Flagyl)

• Effective against anaerobic bacteria and gram-positive bacilli such as clostridium
• Used for intestinal infections by protozoa such as Giardia, amebiasis, and trichomoniasis
• Used for bacterial vaginosis

Antibiotics: Nursing Implications

Penicillins

• Monitor patients for allergic reactions for at least 30 minutes after administration
• Effectiveness of oral penicillins is decreased when taken with caffeine, citrus fruit, cola beverages, fruit juices, or tomato juice

Cephalosporins

• Orally administered forms should be given with food to decrease GI upset, which delays absorption
• Some agents may cause an Antabuse-like reaction when taken with alcohol