Unit 2: Difficult Problems in Otitis Flashcards
Most difficult cases are NOT the result of _____ (3 things).
- Resistant organisms (MDR)
- Strange conformational problems
- Infections with rare organisms
What are difficult cases created by?
Inadequate treatment, chronic changes/biofilm production, failure to ID and control the primary factor, and lack of client commitment
What are some difficult problems you may encounter in practice?
“Allergic” ears, Malassezia infections, Pseudomonas infections, ceruminous otitis externa, hyperplastic ear changes
What are the 7 best practices in the management of otitis?
- Use appropriate diagnostics
- Prepare the canal for treatment
- Choose treatment wisely
- Meds must be administered properly
- Use quality control to evaluate treatment
- Consider long-term maintenance therapy
- ID and control primary factor(s)
Pseudomonas infections are suspected with unusually _____ ears.
painful
What is seen on cytology with a Pseudomonas infection?
Single population of Gram(-) rods
What is the etiology behind Pseudomonas infections?
Same primary factors as all otitis cases (atopy, masses, endocrinopathy, AI disease);
It is almost always a secondary bacterial invader after previous antibiotic therapies
What do you see at the opening of the canal with Pseudomonas infections?
Mucopurulent, sticky material
Swollen, sore, painful
What is the relationship between biofilm and MIC?
MIC of drugs like polymyxin B, enrofloxacin, and gentamicin is significantly higher for biofilm producers
What is biofilm?
Matrix of proteins in a sticky, gel-like substance containing sugary strands (EC polymeric substances)
What are the EC polymeric substances?
Polysaccharides, proteins, EC DNA
Where do bacteria live in biofilm?
In clusters separated by channels
Why is biofilm a good defense mechanism?
Provides protection from abx, antibodies, and phagocytes
What % of human infections are associated with biofilm?
80%
What are the mechanisms of antimicrobial intolerance?
- Antimicrobial depletion (agent doesn’t reach biofilm)
- Slow penetration (gives cells a chance to initiate stress response)
- Stress response (cells change activity in response to challenge)
- Altered microenvironment (metabolically inactive - alive)
- Persister cells (spore-like cells that can survive an antimicrobial challenge)
What are some advantages that bacteria have?
Structural stability, firm adherence to biotic/abiotic surfaces, increased virulence, resistance to antimicrobial therapy, resistance to host immune response
How may cells be dispersed in biofilm?
Shedding of daughter cells, detachment as result of nutritional levels or quorum sensing, shearing of biofilm aggregates
T/F: We should never assume that Pseudomonas and Staph otitis form biofilm.
False - we should assume that they all produce biofilm
What is the most important aspect of management of Pseudomonas otitis?
cleaning the ears
Why is cleaning the ears important?
Removes barriers to topical administration (wax, debris, biofilm), decreases bacterial burden, removes material (pus) that may inactivate meds
What does deep cleaning under anesthesia allow for?
Evaluation of the tympanic membrane and allows use of topical antiseptic
What is a good way to do a deep ear cleaning for Pseudomonas infections?
Flush with body temp saline
Ensure the ear drum is intact
Put in betadine (toxic to middle ear)
Allow to sit then flush out
Some cleansers show _____ activity vs. Pseudomonas.
antimicrobial
How can you maximize the value of your treatment?
Use cultures appropriately, understand the impact of biofilm, and use materials that lower MICs (i.e. Tris-EDTA, N-acetylcysteine/acetic acid)
Why is it important to understand drug [] when looking at a C&S report?
Many dogs will respond to certain therapies even though the report says the organism is resistant; at high enough [] you can get over the bacterial defense mechanisms
What are the mechanisms of Pseudomonas that contribute to its intrinsic resistance?
Genetic mechanisms: lack of porins, efflux pumps, lack of target proteins, chemical alternation of the Ab
What drugs should theoretically never work with Pseudomonas?
Cephalosporins, B-lactams, Tetracyclines, TMS, Macrolides, Lincosamides, Chloramphenicol
What commercial products may be suitable/effective?
Enrofloxacin/SSD, Plymyxin B sulfates (Surolan), gentamicin (Mometamax), orbafloxacin (Posatex)
What is the most common compounded medication that is used topically?
amikacin
What is the 2nd most common compounded medication that is used topically?
Ceftazidime
What are common antiseptics used?
Silver (SSD, micronized), N-acetylcysteine, chlorhexidine, Tris-EDTA, acetic acid
What has SSD been used for historically?
burn management
SSD is a _____ _____ antibacterial and antifungal agent.
broad spectrum
How many mcg/ml is a 1% SSD cream?
10,000 mcg/ml (10 mg/ml)
What are possible adverse effects of SSD?
Adverse drug eruptions, EM, TEN
What is the most common treatment currently by dermatologists for P**seudomonas?
SSD
What antiseptic can SSD be combined with to lower the MIC?
Tris-EDTA
What is the other silver antiseptic we can use but that has little clinical data available?
Micronized silver
What is N-acetylcysteine and what does it do?
Mucolytic agent with antibacterial properties that decreases biofilm production, reduces, production of EPS, and disrupts mature biofilm
What happens to MIC when NAC is combined with a FQ or aminoglycoside?
It increases
What formulation of NAC is preferred?
Topical - has inherent antimicrobial actions
How can NAC be used and what is it compounded with?
Used as a rinse to break down biofilm;
Compounded with tris-EDTA and antibiotic (enrofloxacin)
What is chlorhexidine usually combined with in ear cleansers?
Other active agents or potentiating compounds
What are the actions of tris-EDTA?
Alters cell envelope of bacteria and chelates Ca++
Tris-EDTA is an excellent adjunctive therapy with _____, _____, and _____.
FQs, aminoglycosides, and SSD
What effect on bacteria does Tris-EDTA have when used alone?
Bacteriostatic
To what treatments does Tris-EDTA add value?
Antibiotics (FQs and aminoglycosides), SSD, antiseptics (chlorhex)
What bacteria is acetic acid effective on?
Pseudomonas and S. aureus
With what products is acetic acid synergistic?
Tobramycin, colistin, ciprofloxacin
What is best for controlling pain associated with Pseudomonas otitis?
glucocorticoids
What is the best practice for using GCs in Pseudomonas otitis?
Use it aggressively initially, then back off ASAP
What does systemic antimicrobial therapy depend on?
C&S results, history of previous drug exposure, historical knowledge of the organism
What type of systemic therapy is recommended?
Aggressive - use high end of dosage range
T/F: Systemic antibiotic therapy is generally NOT necessary to manage Pseudomonas otitis externa (or interna).
True
How long past negative cytology/culture should we treat for Pseudomonas otitis?
2 weeks
What is best for checking for clearance of infection?
culture
What often appears as a perpetuating factor after the Pseudomonas has been cleared?
Malassezia
What is done for possible Malassezia infections after treating for Pseudomonas?
We start preventative anti-yeast meds as soon as the bacteria appears to be under control (azole or terbinafine)
What types of chronic infection and inflammation are represented with hyperplastic changes?
Folliculitis, furunculosis, fibrosis, calcification, cystic changes
What diagnostics can be done with hyperplastic otitis?
Palpation of ear canals and bullae, otoscopic exam, imaging
Why do we palpate the ear canals and bullae in hyperplastic otitis?
To check for calcification or fibrosis, pain (bullae involvement), open mouth (pain?)
Why do we do an otoscopic exam on hyperplastic ears?
To check if the hyperplasia is the entire length of the canal
What length of treatment is indicated for hyperplastic otitis?
Long term (Weeks to months)
What is the first thing to try with hyperplastic ears therapy wise?
Glucocorticoids;
This should open up the ears if hyperplasia is due to inflammation and edema; if it doesn’t work, the pet needs surgery
What topical glucocorticoids can be used on hyperplasia?
Flucinolone or mometasone
What therapy can be used for severe hyperplasia?
Cyclosporine or Triamcinolone
How is Triamcinolone administered?
Through the operating head otoscope while under GA, injected through a 23g spinal needle in a corkscrew pattern
What are indications for laser ablation?
Early lesions, polypoid otitis, apocrine cysts
