Antibiotic Therapy For Todays Ocular Infections 2011 - Michigan ...

Bacterial Resistance
• Specific mechanisms
– Development of altered receptors or enzymes that
interact with the drug (production of altered penicillin
binding proteins)
– Decrease in concentration of drug that reaches the
receptors by altered rates of entry or removal of drug
(aminoglycosides may have decreased ribosomal binding
due to decreased diffusion through cell wall)
Methicillin Resistant Staphylococcus
aureus (MRSA)
• HA‐MRSA – health care associated MRSA
– Older adults
– Patients with weakened immune systems
– Hospital, nursing home, dialysis patients
• CA‐MRSA – community associated MRSA
– Affects otherwise healthy patients of any age
– Serious skin and soft tissue infections
– Pneumonia
Methicillin Resistant Staphylococcus
aureus (MRSA)
• CA‐MRSA
– Young age
– Participation in contact sports
– Sharing towels or athletic equipment
– Weakened immune system
– Crowded or unsanitary conditions
– Association with health care workers
• HA‐MRSA
– Current or recent hospitalization
– Live in long term care facility
– Use of invasive devices
– Recent antibiotic use
Bacterial Resistance
• Enhanced destruction or inactivation of drug (B‐
lactamases which catalyze the hydrolysis of
penicillins)
• Synthesis of resistant metabolic pathways
(trimethoprim resistance in Streptococcus due to
production of thymidine nucleotides by alternative
pathway)
• Failure to metabolize the drug (anaerobic bacteria
may not metabolize drug metronidazole to active
metabolites)
Methicillin Resistant Staphylococcus
aureus (MRSA)
• Risk factors
– Antibiotic resistance
– Unnecessary antibiotic use
– Antibiotics in food, water
– Bacterial mutation
Methicillin Resistant Staphylococcus
aureus (MRSA)
• Ocular infection
– Suspect MRSA in unresponsive bacterial infections
– Consider possibility of MRSA in higher risk patients
• Initial treatment options in known MRSA infections
– Conjunctivitis ‐ Trimethoprim‐Polymyxin B, Besifloxacin or
Tobramycin
– Bacterial Keratitis – Fluoroquinolone combined with
Trimethoprim‐Polymyxin B. Cosnider Besifloxacin.
Vancomycin for nonresponsive infection or hospital
acquired infection.