"E" is for employ narrow spectrum

RE: "E" is for employ narrow spectrum

Beats — Mon, 16 Nov 2020 07:59:44 GMT

[quote userid="3169" url="~/001/veterinary-clinical/small-animal/medicine/f/discussions/29501/e-is-for-employ-narrow-spectrum/226714#226714"]I have always thought about this in similar terms to worming sheep and refugia populations! When we treat systemically we affect (pretty much) all cells and all bacteria in the body. If we take the animal and it's microbiome as a population - everything gets exposed to the antimicrobial with systemic treatment. Pour something down 1 or both ears and only the bacteria down the ears are treated (assuming no systemic absorption).[/quote]

I'd never thought of it like that. That's a really helpful analogy for me Michael, thanks!

I guess I've always been thinking more that the owner applying the ear treatment etc is getting more exposure to their own microbiome also etc, and in the case of ears is like a protected microenvironment with everything needed to culture resistant pseudomonas (a potentially killer bug to owner getting hip replacement?) as long as add the correct selection pressure is applied down the ear (say some colistin/polymixin...?) to the ongoing bug-broth; the owner is then instructed to clean it out all over the place with dog shaking head...

RE: "E" is for employ narrow spectrum

Beats — Mon, 16 Nov 2020 07:52:15 GMT

[quote userid="8991" url="~/001/veterinary-clinical/small-animal/medicine/f/discussions/29501/e-is-for-employ-narrow-spectrum/226729#226729"] C/S from urine/ears is almost entirely pointless[/quote]

I culture most of urine and find it helpful.

Don't remember last time I cultured an ear.

One of differences for me is that urine is generally (but not always) clearly a single bug on sediment check; ears rarely so (I'd culture an ear that was not responsive to treatment and had a uniform population of bacteria on cytology).

I don't think knowing what the bug is is entirely pointless at all, and also allows some surveillance of resistance patterns of bugs. The sensitivity testing in urine is generally helpful in my experience. I use Idexx and really like their urine culture service with MALDI-TOF and MICs.

RE: "E" is for employ narrow spectrum

David Mills — Sun, 15 Nov 2020 23:56:58 GMT

Interesting topic this, and I am minded to do more research on it.

Ian Ramsey posts on here occasionally and it would be good to have his pragmatic and sensible input.

Regarding topical treatment, remember that the local concentrations of abx are in their 1000s above MIC and labs do not account for this (I'm not entirely sure how they could in all honesty) - one of the reasons I normally day C/S from urine/ears is almost entirely pointless as higher concentrations can normally overcome apparent resistance unless it is linked to inherent resitance.

RE: "E" is for employ narrow spectrum

Michael Woodhouse — Sun, 15 Nov 2020 23:11:22 GMT

I have always thought about this in similar terms to worming sheep and refugia populations! When we treat systemically we affect (pretty much) all cells and all bacteria in the body. If we take the animal and it's microbiome as a population - everything gets exposed to the antimicrobial with systemic treatment. Pour something down 1 or both ears and only the bacteria down the ears are treated (assuming no systemic absorption).

RE: "E" is for employ narrow spectrum

Beats — Sun, 15 Nov 2020 21:36:16 GMT

[quote userid="3169" url="~/001/veterinary-clinical/small-animal/medicine/f/discussions/29501/e-is-for-employ-narrow-spectrum/226706#226706"]once we start using things topically then the collateral damage is much less.[/quote]

I don't follow. In dogs at least, probably the main bugs of zoonotic concern (or indeed resistance transfer concern) are surely topical bugs (Staph pseudintermedius and Pseudomonas) rather than gut bugs... and they lick their skin so the gut bugs probably get a selection pressure from it also to some degree?

RE: "E" is for employ narrow spectrum

Beats — Sun, 15 Nov 2020 21:33:02 GMT

[quote userid="3169" url="~/001/veterinary-clinical/small-animal/medicine/f/discussions/29501/e-is-for-employ-narrow-spectrum/226706#226706"]I miss Norodine 80.[/quote]

I'm really unsure on this one in particular.

TMPS had been my go to systemic for pyoderma in dogs since I graduated (albeit often at 25-30mg/kg q12hrs rather than the licensed 15mg/kg q12hrs) and probably my most common choice for UTIs in dogs (15mg/kg q12hrs) and emprrical treatment of presumed otitis media in dogs. I think the issue being that there is so much amoxicillin resistance in Staph pseudintermedius and this bug is probably most common reason for treating a dog with antibacterials [contrast cats where everything gets amoxicillin with me pretty much...]?

The clinic I work in never really subscribed to the modern "just-in-time" ordering system often mentioned by veterinary business experts, so our supplies of Norodine 80 lasted until they finally reached their expiry date. Since then I have been using human TMPS equivalent instead, but as Norodine 80 has not returned yet this led me to question had it been withdrawn as it was no longer appropriate for me to be using such a useful antimicrobial as TMPS in dogs as was perhaps better reserved for human health care (would make sense as effective against MRSA etc and like most historically under-used drugs in human healthcare could be making a big resurgence to being antibiotic of last resort etc due to lack of resistance owing to lack of use...)? It is not listed as a first line systemic treatment for dogs with pyoderma in the most recent guidelines I can find and I wonder if that is because it is no longer considered appropriate for pet vets to prescribe? Having said that, it still seems to be available for horses, and I can't see why would withdraw from comnpanion use and not horses (and there are plenty of other antimicrobials such as fluoroquinolones that are licensed and one might expect to be withdrawn first if withdrawl was due to concerns re use in pets) - thus perhaps its withdrawl is related to profits and pharma rather than meaning is now a less responsible first-line choice for dogs than it was 2 years ago?

My trouble is, I'm not sure what is a more appropriate, rational, choice if I'm to move away from TMPS for dogs... I went through a brief clindamycin phase instead, but that didn't seem any more sensible (in spite of being "narrow-spectrum"), but then the other options (amox/clav, cephalexin, FQ) all sound less responsible still.....), so I'm back at TMPS presently until I can figure this one out - I suspect I'll conclude clindamycin better choice but I'm not there again just yet... my issue being I know the local hospitals may use clindamycin for an owner, while I'm less clear on their TMPS use - transfer of bugs and resistance to owners commensals prior to elective hip op etc is presumably main health aim when I'm being "responsible" and avoiding selection of resistance for the drugs currently in human hospital use probably trumps avoiding increased resistance pressure to drugs that are likely to be future human hospital use? This is where I really need more specific guidance from folks that actually know about this stuff, but all I ever seem to see is calls to be more responsible - not clear advice and rationale on what being more responsible actually looks like in real world as a pet vet... or maybe I just haven't got my head around it correctly.

RE: "E" is for employ narrow spectrum

Michael Woodhouse — Sun, 15 Nov 2020 21:07:50 GMT

[quote userid="12930" url="~/001/veterinary-clinical/small-animal/medicine/f/discussions/29501/e-is-for-employ-narrow-spectrum"]Does clindamycin really trump amoxicillin in cats because it is "narrow-spectrum" for instance?[/quote]

I'd say not as a macrolide and therefore (at least according to WHO) a CIA. Therefore amoxycillin 1st

[quote userid="12930" url="~/001/veterinary-clinical/small-animal/medicine/f/discussions/29501/e-is-for-employ-narrow-spectrum"]Does a polymixin/colistin containing ear drop for dogs really trump a florfenicol-containing one by virtue of being "narrow-spectrum"? [/quote]

I also call it as a no, because once we start using things topically then the collateral damage is much less.

[quote userid="12930" url="~/001/veterinary-clinical/small-animal/medicine/f/discussions/29501/e-is-for-employ-narrow-spectrum"]I remain unconvinced that in small animal practice the maxim of "narrow-spectrum is better" [/quote]

I tend to agree. At the end of the day we have a very limited formulary. Honestly my personal view is

1st choice - licenced and not a CIA

2nd choice - licenced, do we have anything to try other than a CIA? In which case consider one

3rd choice - human medicine/cascade use.

I'd be very happy the removal of fluoroquinolones entirely from vet medicine. Get rid of 3rd+ generation cephalosporins. I would struggle without macrolides. I miss Norodine 80.