62 (140)

6: Bacterial dermatoses

Histopathological examination of skin biopsies may be consistent with bacterial infection and also an underlying dermatosis. This procedurę may reveal intraepidermal pustules containing degenerate neutrophils, perifolliculitis, or mural or interface folliculitis compatible with bacterial infection. Special stains may be used according to the differentials \

Bacterial culture should be routine in cases of recurrent pyoderma or when multiple species of bacteria are seen on cytology.

A search for an underlying dermatosis or systemie illness should always be conducted and the condition identified where possible.

Treatment

Systemie antimicrobial therapy is the treatment of choice. The majority of staphylococci responsible for pyoderma in the cat, are resistant to penicillin, amoxycillin and ampicillin. The most effective antibiotics are clavulanic acid-potentiated amoxycillin, cephalosporins (e.g. cephalexin and cefadroxil), enrofloxacin, marbofloxacin and clindamycin. Trimethoprim-potentiated sulphonamides are often used in Europę and the United States ^8,9 (Table 6:1), although in Australia, strains of Staphylococcus intermedius are very commonly resistant to these ¹⁰. Antibiotics should be given for a minimum of 3 weeks and should be continued for at least a week beyond clinical resolution. Pastę preparations are particularly useful, firstly because they are easy to administer and secondly because they can generally be given in one daily dose.

Antibacterial shampoos are rarely used because cats have a reputation (often unjustified) for not liking being washed. However, shampoos, when it is possible to apply them easily, form a very effective adjunctive therapy. A 2-3% chlorhexidine solution is one example. For localised pyoderma, local application of an antiseptic containing 0.5% chlorhexidine is often useful.

Treatment of the underlying cause, when identified, is essential to prevent or limit recurrence.

Superficial juvenile pustular dermatitis

Superficial juvenile pustular dermatitis is a bacterial skin infection of the cat caused by Pasteurella multocida and various beta-haemolytic streptococci. No underlying cause has been identified. Dermatological signs are characterised by non-follicular pustules associated with epidermal collarettes, mainly on the dorsal neck and trunk. Systemie signs are rare. Pasteurella multocida or beta - haemolytic streptococci may be isolated on bacterial culture. Histopathological examination of skin biopsies demonstrates the presence of non-follicular pustules containing lots of degenerate neutrophils. Treatment involves giving a suitable antibiotic for about 3 weeks.

Bacterial paronychia

Aetiopathogenesis

Bacterial paronychia is particularly common in the cat. Various bacteria have been isolated from within lesions, including Staphylococcus spp., Streptococcus spp., Pseudomonas spp., and Proteus spp. Multiple bacterial paronychia should lead to suspicion of an underlying dermatosis or systemie illness (e.g. retrovirus infections, systemie lupus erythematosus)^IU2.

Clinical features

Dermatological signs are characterised by painful and swollen nail beds (Fig. 6 : 3). Pus, varying in colour and sometimes with a nauseating smell caused by the bacteria, is also present around the digits. Multiple digits and several feet are very often affected " ^l2.

Systemie signs vary according to the underlying illness.

6.3