Organisms normally found within cats' mouths are also found within abscesses.
Pasteurella multocida, Bacteroides spp , beta-hemolytic streptococci, and fusiform bacilli.
For non-healing wounds consider atypical mycobacteria.
Predisposing factors General
An intact male cat with access to the outside environment will fight for sexual favors.
Cats in a population dense area will fight to maintain territory.
Immunosuppressed individuals, eg with feline leukemia virus or feline immunodeficiency virus , may show more severe signs, or fail to respond to appropriate therapy.
Pathophysiology
Cat bites and scratches are major cause subcutaneous bacterial infection.
Bacteria are injected under the skin.
The small puncture wound heals rapidly.
Over the next 2-4 days bacteria multiply.
Normal defense mechanisms may fully clear the infection.
The infection may be walled off by fibrous tissue and rupture to the surface exuding cream green pus with fetid odor.
Infection may spread locally or hematogenously, leading to cellulitis, local lymphadenopathy or other organ involvement.
If already ruptured, clip and clean abscess with saline, dilute chlorhexidine or dilute hydrogen peroxide .
Liberal surgical drainage in non-ruptured abscesses will require general anesthesia or heavy sedation .
Cases which require extensive incisions will merit bandaging. If this is not possible place drain or leave open wound, eg side of face.
Oral antibiotics for 5-7 days. Choose bactericidal (clindamycin licensed for this use, but bacteriostatic) antibiotics with activity against the more frequently encountered organisms.
Non-steroidal anti-inflammatories in cases with pyrexia and pain .
Subsequent management
Treatment
May get overlying skin necrosis necessitating debridement.
Walker R D, Walshaw R, Riggs C M & Mosser T (1995) Recovery of two mycoplasma species from abscesses in a cat following bite wounds from a dog.J Vet Diagn Invest7 (1), 154-156.
Beale K M (1995) Nodules and draining tractsVet Clin North Am Small Anim Pract25 (4), 887-900.
Hoshuyama S et al (1996) Isolation of obligate and facultative anaerobic bacteria from feline subcutaneous abscesses.J Vet Med Sci58 (3), 273-274.
Kanoe M et al (1984) Obligate anaerobic bacteria found in canine and feline purulent lesions.Br Vet J140 (3), 257-262.
Ihrke P J (1984) Therapeutic strategies involving antimicrobial treatment of the skin in small animals.J Am Vet Med Assoc185 (10), 1165-1168.
Love D N, Jones R F & Bailey M (1979) Description of strains of Peptostreptococcus anaerobius isolated from subcutaneous abscesses in cats.J Gen Microbiol112 (2), 401-403.
Vetstream contributor(s)
Dr Rosanna Marsella DVM DACVD, PO BOX 100126, SACS, College of Veterinary Medicine, University of Florida, Gainesville, FL 32610-0126, USA.
D H Scarff BVetMed CertSAD MRCVS, Anglian Referrals, 2 Highlands, Old Costessey, Norwich NR8 5EA, UK. Tel/Fax: 01603 743415.
Print off the Owner factsheet on abscesses 
subcutaneous bacterial infection.