As spring warms up, my own nose and sinuses have detected increasing pollen levels, and there’s been a corresponding increase in pruritic patients coming across the threshold.
I think the role of pyoderma in allergic skin disease is well established and accepted. However, it is not uncommon to see dogs with no obvious skin lesions that are markedly pruritic, and cytology often reveals large numbers of cocci without the correspondingly high levels of inflammatory cells.
In patients with reduced barrier function, this overgrowth can contribute significantly to the levels of pruritus. I find a significant number of dogs’ pruritus reduces by at least 50%, if not more, with appropriate antibiotic and shampoo therapy when overgrowth is identified by cytology.
I usually repeat the cytology in around 2 to 3 weeks to check for resolution, although, of course, given the relapsing nature of the condition periodic treatment is required.
Reference
Rosenkrantz W (2010). Proceedings of the NAVC Conference 2010.
This one’s a little controversial, but some evidence exists that taking swabs for culture from cases of otitis externa can lead to poor reproducibility.
Swabs taken from the same ear may produce different isolates, and even when the isolates agree, they may have different (antibiotic) susceptibility patterns (Bloom, 2015; Graham-Mize et al, 2004; and Schick, 2007).
Bloom (2015), therefore, suggested using rational topical therapy based on cytological findings was more valuable than using bacterial culture and sensitivity. He also only advised repeat cytology if the ear was not clinically resolving or neutrophils and bacteria were present on initial cytology.
He only takes culture and sensitivity where rods are found on cytology, there are proliferative changes and the ear is responding poorly to therapy – a rare set of circumstances in Paul Bloom’s experience.
This approach was supported by a study in which the authors evaluated whether any correlation was noted between topical antibiotic selection, in vitro bacterial antibiotic sensitivity, and clinical response in 17 cases of canine otitis externa complicated by Pseudomonas aeruginosa (Robson et al, 2010).
VIDEO: How to properly swab an ear for aural cytology (source: YouTube).
References
Bloom P B (2015). Diagnosis of Otitis Externa in the Real World, Proceedings of the North American Veterinary Conference, Orlando, Florida: 944-953.
Graham-Mize C A and Rosser E J Jr (2004). Comparison of microbial isolates and susceptibility patterns from the external ear canal of dogs with otitis externa, J Am Anim Hosp Assoc40(2): 102-108.
Robson D C, Burton G G and Basset R J (2010). Correlation between topical antibiotic selection, in vitro bacterial antibiotic sensitivity and clinical response in 17 cases of canine otitis externa complicated by Pseudomonas aeruginosa, (Abst). In 25th Proceedings of the North American Veterinary Dermatology Forum, 2010: 245.
Schick A E, Angus J C and Coyner K S (2007). Variability of laboratory identification and antibiotic susceptibility reporting of Pseudomonas spp isolates from dogs with chronic otitis externa, Vet Dermatol18(2): 120-126.
I had the privilege of attending the North American Veterinary Community Conference in January. The experience provided me with a number of top tips, which I thought I would pass on to you in the coming few weeks.
For those of you who are skeptical of the role professional experience plays in establishing evidence, many authors accept that not all evidence is derived from academic sources, for example, Schon (1984) and Bolton (2000) to name just two. I have still included reference to the appropriate sessions to keep those of you happy.
Have you ever pondered when treating cases of diarrhoea with an infectious origin as to whether there is any point in using a probiotic at the same time as a course of antibiotics? Well yes, you can.
I attended a joint session hosted by Mike Lappin and Stan Marks. Although it is not possible to say definitively for all probiotics and all antibiotics, Dr Lappin has conducted work to show the strains in Purina Fortiflora are unaffected by metronidazole at doses up to 20mg/kg. Good to have this confirmed, as this is a strategy I often use.
References
Lappin M and Marks S (2015). Quench the Stench: Strategies for Control of Diarrhea, North American Veterinary Conference, Orlando 2015.
Bolton G (2000). Reflective Practice: Writing and Professional Development, Paul Chapman Publishing, London.
Schon D (1984). The Reflective Practitioner: How Professionals Think in Practice, Basic Books.
Greenish purulent discharge accompanied by crusting, erythema and punctuate ulcerations in a crossbreed affected by Pseudomonas aeruginosa otitis externa, secondary to an adverse drug eruption. Image source: Veterinary Times 45.01 (Jan 6, 2014) – “Otitis: a diagnostic approach” by Filippo De Bellis.
I suspect we have all come across that tricky Pseudomonas otitis case that just seem to refuse to completely respond to antibiotic therapy in spite of extensive investigation for underlying causes.
I had just one such case recently that, in spite of culture and sensitivity, blood work, skin biopsy, extensive flushing, lack of response to licensed products (and so on), just refused to respond.
A quick look through one of my trusty text books* suggested Ticarcillin.
Ticarcillin potentiated with calvulanic acid (Timentin) is an extended spectrum penicillin that often has good activity against Pseudomonas. The 100mg/ml antibiotic solution can be applied directly to the ear canal as a drop.
The case I’m treating has responded really well.
* Reference: Hill, P.B. (2002) Small Animal Dermatology: a practical guide to the diagnosis and management of skin diseases in dogs and cats. Butterworth-Heinemann. London.
