Antibiotic-resistant otitis

Re: Antibiotic-resistant otitis

james herriot lied — Sun, 16 Sep 2012 17:41:42 GMT

Another vote for baytril instilled direct - although I use the 2.5% in equal volume of steroid, so it works out to about 1% enrofloxacin, and use separate cleaner. Once daily or EOD.

I can't recall a non-responsive case, but am always acutely aware of the prevalence of clinical as opposed to bacteriological cures in these cases - and whilst c/s isn't all that sensitive for the immediate post-treatment phase, getting owners to comply with swabbing a month or so down the line in a symptomless patient is akin to the labour of Sisyphus.

Re: Antibiotic-resistant otitis

Stuart Fitzgerald — Sun, 16 Sep 2012 16:48:00 GMT

Sorry for being AWOL from my own thread- having a bit of a manic weekend on call! I performed otoscopy on the dog under general anaesthesia while obtaining the swab and I do not believe the TM is intact although I couldn't advance the scope as far as I would have liked in the ear. In any case, I couldn't visualise the membrane and am working on the assumption it is not intact.

Thanks for all the very interesting contributions, and the point on topical treatment potentially overcoming any in vitro resistance is well made. When I last discussed one of these cases with a dermatologist I was advised to use a 1% solution of gentamicin in Triz EDTA and was assured it would not cause ototoxicity even in the absence of an intact TM. I have not tried the enrofloxacin solution before.

I currently have the dog on 1mg/kg prednisolone BID while formulating a full treatment plan and I will consider a lateral wall resection if the ear canal 'opens' when the infection and associated inflammation are more under control, however at the moment I am not convinced that it will give us greatly improved aeration of the canal given its narrowness and the fact that my patient has enough redundant folds of skin to cover three 'normal' dogs.

Thank you all again for your input..... I'm off to retrieve an injured sparrowhawk from atop a chicken coop.

Re: Antibiotic-resistant otitis

Rajat — Sun, 16 Sep 2012 11:54:16 GMT

[quote user="bob lehner"]

[quote user="Rajat"]The recipe I use for these cases is : 14mls LA 10% baytril 6-8mls colvasone in a bottle of Triz Aural (dechra) -obv you need to remove some from the bottle first (sorry I made this mistake and felt silly so thought I'd mention it!)[/quote]

Interested in this - do you really use the 10% Baytril solution ? I looked into this once and spoke to one of the companies that makes a Triz ear wash - they recommended 16 mls of 2.5% Baytril per 100 mls of Triz soln , giving a final concentration of around 0.4% Baytril, which they considered safe for instillation in an ear with a possibly ruptured TM. Have also heard derm specialists recommend 0.4% Baytril soln for instillation into ears.

[/quote]

Hi Bob yes I do, I got the recipe from conference proceedings and dermatologists on VIN, the higher concentration means less is needed - they usually recommend 1 gram per 100mls, I have used between 1 gram and 1.4grams (as per above) so 10-14mls..before I got the LA stuff tho I was using the SA baytril... now there's no 'studies' on whether enrofloxacin is safe but anecdotal data suggests it is at these concentrations. I too have used it directly into the bulla for lavage and postop with ruptured drums and 'found' no problems, fwiw!

Re: Antibiotic-resistant otitis

bob lehner — Sun, 16 Sep 2012 11:31:21 GMT

Re: Antibiotic-resistant otitis

Rajat — Sat, 15 Sep 2012 19:20:25 GMT

sorry forgot to link the study:

Ototoxicity caused by topical administration of gentamicin versus tobramycin in rabbits.

Re: Antibiotic-resistant otitis

Rajat — Sat, 15 Sep 2012 18:57:27 GMT

[quote user="An On MRCVS"]What do you think is in it which is ototoxic that your homemade doesn't contain?[/quote]

The 'base' in commercial ear drops is what I have learnt is potentially ototoxic - and like I said previously I have seen incidence of deafness and ototoxicity in dogs who have had these drugs and (later) found to have compromised TMs.

[quote user="An On MRCVS"] ANYTHING which goes in there is dodgy[/quote]

Agreed!

[quote user="An On MRCVS"] so only way topical caused classic AG toxicity is if enough were absorbed into circulation, went systemic - and damaged the hairs - hence the study mentioned earlier[/quote]

This study suggests (a lower concentration of ) gentamicin instilled directly into the middle ear causes ototoxicity in rabbits (than the study previously linked)

I think there is little evidence in veterinary otic medications for which to use how long for and what exactly is ototoxic and what isn't. The only thing people seem to agree on is saline, btu even that is quite low in p so I wonder about it's effect on nerves.

Having said that, most dermatologists seem to agree on the 'gemish' previously quoted, that it seems to provide a good and safe way to treat stubborn infections in the face of a compromised drum or bacterial resistance and that is is a preferred way to medicate these ears than using a commercial preparation with a much higher likelihood of causing ototoxicity.

Re: Antibiotic-resistant otitis

An On MRCVS — Sat, 15 Sep 2012 18:17:19 GMT

I was going to say - beware of bias - Dechra make Canaural - but - oh - they include links to ototoxicity of framycetin - which is in Canaural! Also talks about polymixin B - in Surolan. Wonder why people always talk about gentamicin and not framycetin when talking ototoxicity?

I am curious about your stated preference for avoiding abusing the cascade Raj. You mentioned using enrofloxacin - similar profile to marbo - so why not use Aurizon? What do you think is in it which is ototoxic that your homemade doesn't contain? If distilled water were licensed it would have to carry a caution about ruptured TM - ANYTHING which goes in there is dodgy - but the mechanism of ototoxicity of gentamicin is systemic (to do with the hairs) - so only way topical caused classic AG toxicity is if enough were absorbed into circulation, went systemic - and damaged the hairs - hence the study mentioned earlier. As someone alluded to, systemic resistance profiles irrelevant when using topicals.

Re: Antibiotic-resistant otitis

Rajat — Sat, 15 Sep 2012 17:10:23 GMT

[quote user="Rob Davis"]Please note tongue in cheek smiley in previous post! [/quote]

Lol yes- tho it seems your suggestion was that I was being contradictory to my previous statement re the cascade, hence my question. Tongue in cheek duly noted

[quote user="Rob Davis"]I was taught (admittedly some years ago now!) by Dick White that there is a negligable risk of ototoxicity when using topical gentamycin. I have regularly used it since then when there is no ear drum present[/quote]

Yup - and I have seen and scoped plenty of dogs who have had ruptured TMs with no ototoxicity from a variety of topicals - always surprises me. Equally I have seen and caused ototoxicity similarly although I do admit less frequently. So I am unsure how risky it is, where we draw the line and so on. But there is a risk, and I know I'd prefer not to take it in my pet if that makes sense... equally I would like to know for future use re gentamicin and other such drugs exactly how ototoxic and at what concentrations and what amounts- sorry re-reading I sounded curt I was in the middle of consults and didn't insert enough smilies

This is an interesting article goes thru all the topical and systemic toxicities - http://www.dechra-us.com/Articles.aspx?PID=23573&Action=1&NewsId=725&currentPage=7 - and has some links re ototoxicity of gentamicin topically and systemically- you're right tho I cannot find any new or rigorous studies on a quick search will try later and in derm book to see if it is just 'one of those things' that has become entrenched in folklore..

Cheers

Raj

Ps- I didn't think you were red star man - and if you are at least you are contributing to the discussion eh ;-)

Re: Antibiotic-resistant otitis

Rob Davis — Sat, 15 Sep 2012 16:28:55 GMT

PS I'm not Mr Red Star Man!

Re: Antibiotic-resistant otitis

Rob Davis — Sat, 15 Sep 2012 16:27:22 GMT

[quote user="Rajat"]

[quote user="Rob Davis"]But Rajat, what about the cascade?[/quote]

Can you give me a licensed preparation that is safe in a dog with a ruptured TM (or high likelihood of a ruptured TM ) that is licensed, if so, I will obey the cascade sir. Or, as in this case, where there is drug resistant bacteria and no other preparation that can be used, what is your licensed tx of choice, pray elucidate I am all ears.

[/quote]

Please note tongue in cheek smiley in previous post!

[quote user="Rajat"]

Thank you for this interesting abstract. I wonder if their quantities and conentrations were sufficient to reach the middle ear and cause the toxicity. Ototoxicity from gentamicin is well documented in the literature. I am not comfortable on the basis of this one abstract to start using it. Indeed, it is the one drugs referral dermatologists recommend to avoid even when they do use other drugs off license with ruptured drums.

[/quote]

I was taught (admittedly some years ago now!) by Dick White that there is a negligable risk of ototoxicity when using topical gentamycin. I have regularly used it since then when there is no ear drum present, and have yet to encounter any problems. I would be interested to know if there are any other references contradicting the above study (I appreciate it is fairly old now and on a fairly small sample size, but is there really any evidence that topcial gentamycin is an issue?)

Re: Antibiotic-resistant otitis

Rajat — Sat, 15 Sep 2012 16:04:07 GMT

Wow someone is on a one star giving spree, David and James and Bob gave helpful and good info, why the one stars? Wonder if the 'giver' has any pearls of wisdom..or if he/she is involved in the post. Slightly annoying but I should probably not give this starring system much attention anyways!

Re: Antibiotic-resistant otitis

Rajat — Sat, 15 Sep 2012 16:01:58 GMT

[quote user="Rob Davis"]

[quote user="Rajat"] I'd worry about gentamicin in a chronic O.E. case as >80% have Otitis media (and compromised tympanic membranes tho may have ruptured and then healed over so gentamicin may not get into middle ear cavity)[/quote]

I was under the impression that topical gentamycin is very unlikely to cause ototoxicity cf systemic gentamycin.

Am J Vet Res. 1995 Apr;56(4):532-8.

Ototoxicity assessment of a gentamicin sulfate otic preparation in dogs.

Strain GM, Merchant SR, Neer TM, Tedford BL.

Source

Department of Veterinary Physiology, Pharmacology, and Toxicology, School of Veterinary Medicine, Lousiana State University, Baton Rouge 70803, USA.

Abstract

Vestibulotoxic and ototoxic effects often are seen after long-term, high-dose systemic treatment with gentamicin, but toxic effects after topical use have not been reported in animals, to the authors' knowledge. Vestibular and auditory effects of twice daily otic gentamicin treatment for 21 days were evaluated in 10 dogs with intact tympanic membranes and in the same 10 dogs after experimental bilateral myringotomy. Each dog served as its own control; 7 drops of gentamicin sulfate (3 mg/ml in a buffered aqueous vehicle) were placed in 1 ear, and 7 drops of vehicle were placed in the opposite ear. Treatment and control ears were reversed after myringotomy. Vestibular function was evaluated daily by neurologic examination and behavioral assessment. Auditory function was evaluated twice weekly by determination of brain stem auditory evoked potentials. Gentamicin sulfate placed in the ear of clinically normal dogs with intact or ruptured tympanic membranes, in the quantities used in this study, did not induce detectable alteration of cochlear or vestibular function. Serum gentamicin concentration after 21 days of treatment was detectable in only 2 dogs and was an order of magnitude below documented toxic concentrations.

PMID:: 7785834; [PubMed - indexed for MEDLINE]

[/quote]

Re: Antibiotic-resistant otitis

Rajat — Sat, 15 Sep 2012 15:59:40 GMT

[quote user="Rob Davis"]

[quote user="Rajat"]I think you will find a topical 'gemish' o fTriz Baytril (large animal 10%) and colvasone will do the job[/quote]

But Rajat, what about the cascade?

"We may rail against it and I won't let an animal suffer or die because of it, but I don't flout it willy nilly."

[/quote]

I think you will find this is legal under the cascade.

Pray inform what is your licensed drug of choice given the above sensitivity profile in a chronic O.E ear where the drum has a high possibility of being ruptured? I am all 'ears' !

Re: Antibiotic-resistant otitis

Rajat — Sat, 15 Sep 2012 15:52:54 GMT

[quote user="Rob Davis"]But Rajat, what about the cascade?[/quote]

Re: Antibiotic-resistant otitis

Rob Davis — Sat, 15 Sep 2012 15:28:56 GMT

I was under the impression that topical gentamycin is very unlikely to cause ototoxicity cf systemic gentamycin.

Am J Vet Res. 1995 Apr;56(4):532-8.

Ototoxicity assessment of a gentamicin sulfate otic preparation in dogs.

Strain GM, Merchant SR, Neer TM, Tedford BL.

Source

Department of Veterinary Physiology, Pharmacology, and Toxicology, School of Veterinary Medicine, Lousiana State University, Baton Rouge 70803, USA.

Abstract

PMID:: 7785834; [PubMed - indexed for MEDLINE]

Re: Antibiotic-resistant otitis

Rob Davis — Sat, 15 Sep 2012 15:25:32 GMT

[quote user="Rajat"]I think you will find a topical 'gemish' o fTriz Baytril (large animal 10%) and colvasone will do the job[/quote]

But Rajat, what about the cascade?

"We may rail against it and I won't let an animal suffer or die because of it, but I don't flout it willy nilly."

Re: Antibiotic-resistant otitis

David Mills — Sat, 15 Sep 2012 13:56:41 GMT

All of the above is sound advice, especially the C/S results requiring interpretation with caution - I view these as useless for deciding topical treatment but they are required if giving systemic antibiotics, which I think are essential in most of these types of cases. Don't be afraid of preds at good doses either - 1mg/kg minimum can dramatically improve ear health.

I wouldn't necessarily rush into a TECA without further investigations +/- myringotomy first. Even then, a lateral wall resection - peculiarly out of favour for a while - can improve access and aeration of the horizontal canal which can be enough to allow efficacious treatment in many cases and of course will preserve hearing. Remember that TECAs can carry complication rates of upto around 80% even with specialists so it is decidedly NOT something to be undertaken lightly and it is worth finding someone who does a lot (and has personalised complication rates available) when selecting someone to refer to - by this I mean at least 2-3 per month not per year.

Re: Antibiotic-resistant otitis

Rajat — Sat, 15 Sep 2012 13:44:40 GMT

I think you will find a topical 'gemish' o fTriz Baytril (large animal 10%) and colvasone will do the job -the MIC can often be overcome by topical therapy.

Has the dog had video otoscopy, and is the TM itnact? I'd worry about gentamicin in a chronic O.E. case as >80% have Otitis media (and compromised tympanic membranes tho may have ruptured and then healed over so gentamicin may not get into middle ear cavity)

The recipe I use for these cases is : 14mls LA 10% baytril 6-8mls colvasone in a bottle of Triz Aural (dechra) -obv you need to remove some from the bottle first (sorry I made this mistake and felt silly so thought I'd mention it!)

Fill canal bid, rub in vigorously.

Repeat cytology +/- culture every 1-2 weeks

I think cefovecin is dangerous here despite the sensitivity and if you do use it, I'd prob do it every 8-9 days for 3 doses to ensure the coliforms don't become resistant. never used it topically I was suggesting its use systemically for the poss O.Media.

I've got a chronic pseudomonas on the go at the mo who is resistant to everything. other than gentamicin and framcyetin. And he doesn't have an ear drum at all...fun times...!

cheers

Raj

Re: Antibiotic-resistant otitis

Rob Loxley — Sat, 15 Sep 2012 10:25:15 GMT

Some thoughts:
often topical tx will achieve high enough concentrations to confound lab reports of resistance
if it cleared before but recurred has he got concurrent OM
if TECA/LBO is an option then I'd be pursuing this sooner rather later

Re: Antibiotic-resistant otitis

James Laidlaw — Sat, 15 Sep 2012 10:21:27 GMT

How is it getting E. coli ear infection? Is it a swimmer or in dirty conditions at all - cause this might be an important part of avoiding the problem in future. Also, has it had C+S before, because often the results don't necessarily bear out what will happen with treatment in vivo vs. lab sens testing - ie: you may find the triz and gentamycin treatment used previously will work again this time, without having to resort to convenia in the ear!!

Re: Antibiotic-resistant otitis

Bob Russell — Sat, 15 Sep 2012 10:21:13 GMT

The makers are confident that their chlorhexidine products are not ototoxic but poss worth warning of the slight risk! With multiple resistant bugs chlorhexidine seems to be the route recommended especially for skin type bugs!

Re: Antibiotic-resistant otitis

Stephen Courtney — Sat, 15 Sep 2012 10:08:33 GMT

Have a look at the ear products that Vetruus make - they do an excellent antiseptic ear cleaner called otodine which has chlorhexidine and Tris EDTA in it - might be better to the antiseptic route as antibiotics look compromised.

Vetruus ' website has several innovative ear products and also provides CPD. I haven't used any of them yet - I'm in no hurry to aquire another of these headaches - but the options seem interesting. I don't have a link but Google, as in all things, will be your friend!