Unit 6 Bacterial Infections

Aerobic

Thrive in an oxygen rich environment

Anaerobic

Grow optimally without oxygen

Pathogenicity

Ability of an organism to cause disease

Virulence

Quantitative measure of an organism’s pathogenicity

Invasiveness

Ability of the pathogen to grow extremely rapidly and cause direct damage to surrounding tissues by their sheer number.

Exotoxins

Proteins released by bacteria into surrounding tissues that have the ability to inactivate or kill host cells

Endotoxins

Harmful non protein chemicals that are part of the outer layer of the normal cell wall of gram negative bacteria.

• when the cell dies, endotoxins are released into surrounding tissues, causing inflammation, fever, and chills.

Bacilli shape?

Rods

Cocci shape?

Spherical

Spirilla shape?

Spiral

Bacterial Gram-Staining

Thick cell walls = gram positive

Thin cell walls = gram negative

Bacteriocidal

Kill bacteria

Bacteriostatic

Slow bacterial growth, allowing natural body defenses to eliminate microorganisms

Acquired resistance

The ability of an organism to become unresponsive to an anti-infective agent

Superinfections

Secondary infections.

• Candida albicans in the vagina

• Streptococci in the oral cavity

• Clostridium difficile in the colon

Antibiotics Indications

Bacterial infection treatment or prophylaxis

Antibiotics Side Effects

• Nausea

• Vomiting

• Diarrhea

• Rash

Absorbs better on empty stomach, but may need to be taken with food due to N/V

• Can be nephrotoxic

• Hypersensitivity and allergic reactions

• Increase bleeding time if taken with anticoagulants

• Risk of superinfection

• Decreases effectiveness of oral contraceptives

Piperacillin & Tazobactam (Zosyn)

Extended-Spectrum Penicillin

MOA: inhibits bacterial wall synthesis. Tazobactam added to avoid inactivation

Piperacillin & Tazobactam (Zosyn) Adverse Effects

• Diarrhea, hypokalemia, hyperglycemia, rash

• Thrombocytopenia, bleeding, platelet dysfunction

• Risk for C. diff infection

Piperacillin & Tazobactam (Zosyn) Considerations

• Caution with initial doses, can cause anaphylaxis

• Increase bleeding time

• HF pts can have sodium overload

• Safe in pregnancy (category B)

• Developed to combat Pseudomonas aeruginosa →

• Separate ESPs from aminoglycosides by at least 2 hrs, penicillins inactivate aminoglycosides if given closer together.

Piperacillin & Tazobactam (Zosyn) Indications

Skin, blood, sinus, CNS, respiratory infections. Surgical prophylaxis.

Cefazolin (Kefzol, Ancef)

1st Gen Cephalosporin

MOA: inhibit bacterial wall synthesis (bacteriostatic).

Broad spectrum

Cefazolin (Kefzol, Ancef) Considerations

• Monitor kidney function

• Synergistic antimicrobial action with other antibiotics

• Frequently used for surgery prophylaxis

Ceftriaxone (Rocephin)

3rd Gen Cephalosporin

MOA: inhibits bacterial wall synthesis.

Ceftriaxone (Rocephin) Considerations

• Longer duration allows for once-daily dosing

• Sometimes a preferred drug during pregnancy

• Crosses BBB

• Route IV/IM (very painful)

Ceftriaxone (Rocephin) Adverse Reactions

• High dose: risk for seizures

• GI-related issues including risk for C. diff

Imipenem-cilastatin (Primaxin)

Carbapenem

MOA:

• inhibits bacterial wall synthesis (bacteriostatic)

• Broad spectrum

• Cilastatin sodium prevents the destruction of imipenem and allows for higher serum levels of the antibiotic

Imipenem-cilastatin (Primaxin) Adverse Effects

Rare reactions: confusion, seizures, hallucinations

Imipenem-cilastatin (Primaxin) Contraindications

Use with caution in pts with head injury or history of seizures.

Overdose may result in ataxia.

Imipenem-cilastatin (Primaxin) Considerations

• Only give IV

• Short half-life requires it to be dosed as often as every 6 hrs

• Reserved for serious infections or as sepsis prophylaxis

• Resistance has developed in the form of carbapenem-resistant Enterobacteriaceae (CRE)

  • high mortality rates, up to 50%

Vancomycin

MOA: inhibits bacterial wall synthesis

Narrow-spectrum: gram positive organisms

Vancomycin Contraindications

• Impaired renal function

• History of hearing loss

Vancomycin Interactions

• Adds to toxicity of other ototoxic and nephrotoxic medications

• With metformin: may increase risk of lactic acidosis

Vancomycin Adverse Effects

• Vancomycin Flushing Syndrome (VFS)

  • Administer slowly

  • Hypotension, flushing, rash

• CNS: confusion, seizures, hallucinations

• Extravasation may cause tissue necrosis

• Ototoxicity: tinnitus and high-tone hearing loss precede deafness and may progress even after discontinuation

• Nephrotoxicity: can occur using therapeutic concentrations, but more common if trough serum concentrations kept above 10 mcg/mL

• Anaphylactic response (may lead to vascular collapse)

Vancomycin Considerations

• Use restricted to severe infections that have become resistant to other antibiotics

• Usually administered by slow (2+hours) IV infusion for systemic infection

  • PO for GI treatment only at lower-dose - not absorbed into systemic circulation

• Monitor serum peak and trough levels

Trough Level?

Lowest level of drug in blood.

Collect just prior to (30 min before) the next dose

Peak Levels?

Highest level of drug in the blood.

Collect following the administration of the dose

• 30 min after the dose (Tobra/Gent)

• 1.5 hrs after dose (Vanco)

Aztreonam

Monobactam antibiotic

MOA:

• narrow-spectrum: gram negative microbes

• cell wall inhibitor

• IV or inhaled for cystic fibrosis patients

• Pregnancy category B

Aztreonam Adverse Effects

• Superinfections

• Rare adverse effects: anaphylaxis, seizures

Linezolid (Zyvox)

Protein Synthesis Inhibitor- Oxazolidinones class

Linezolid (Zyvox) Contraindications

Risk for hypertension and palpitations with sympathomimetics

Linezolid (Zyvox) Adverse Effects/Considerations

• Transient dose-related myelosuppression → monitor CBCs

• Hypertension

• Hypoglycemia in DM patients

Aminoglycosides

• Drugs ending in -mycin, -micin

• Treat aerobic, life-threatening gram-negative infections

• Less than 1% of dose is absorbed orally, so drugs must be given IV

• Are given topically (eyes) or inhaled (cystic fibrosis)

• Can cross placenta (category C or D)

• Toxic to kidneys

• Toxic to ears

Gentamicin (garamycin)

Aminoglycoside

MOA:

• Inhibits bacterial protein synthesis

• Primarily for serious infection

Route:

• given IV or IM or topically (ophthalmic)

• ophthalmic formulation prescribed for conjunctivitis

Gentamicin Adverse Effects

• Thrombocytopenia

• BBW:

  • nephrotoxicity 26%

  • ototoxicity 25%

Gentamicin Contraindications

• Impaired renal function or existing hearing loss

• Pregnancy or breastfeeding

Gentamicin Drug Interactions

• Caution with other meds that are nephrotoxic or ototoxic

• Antiemetics may mask signs of aminoglycoside-induced ototoxicity

• Inactivated if mixed with penicillins

Gentamicin Considerations

• Monitor kidney function

• Monitor for ototoxicity

• Monitor CBC

Fluoroquinolones

Affect bacterial DNA synthesis

Most have been removed from drug market (dangerous)

Used for infections in hard to treat areas such as deep in lungs, GI, GU, or skin/soft tissue areas

Given PO or IV

Levofloxacin

Fluoroquinolone

• Prolonged post antibiotic effect, broad spectrum.

• Long half life allows for once daily dosing.

Levofloxacin Interactions

• Increased anticoagulant effect with warfarin

• Decreased absorption with antacids or mineral supplements

• Slows hepatic metabolism of xanthines (caffeine)

Levofloxacin Adverse Effects

• Cartilage toxicity

• GI toxicity, C-diff risk

• Cardiotoxicity

  • dysrhythmias, prolonged QT interval, aortic aneurysm

• Neurotoxicity:

  • CNS effects, psychoses, neuropathy, agitation, delirium, disorientation, disturbance in attention, memory impairment, nervousness

• Photosensitivity

• Hepatotoxicity

• Hypoglycemic coma

Levofloxacin Black Box Warnings

• Associated with tendonitis and tendon rupture

• Increased muscle weakness in pts with myasthenia gravis