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Three Part Question

In [patients with cat bite wounds] do [prophylactic antibiotics] reduce [the incidence of wound infection]?

Clinical Scenario

A 29 year old man presents to the Emergency Department with a cat bite wound on left his arm. He says he was bitten some 6 hours prior to attendance. The wound is cleaned and it is noted that there are no signs of infection. You wonder whether prophylactic antibiotics are required to reduce the risk of wound infection.

Search Strategy

Ovid MEDLINE(R) 1950 to June Week 4 2008 and EMBASE 1980 to 2008 Week 27 using multifile searching

The Cochrane Library Issue 2 2008
cat bite.mp. AND (wound infection.mp. or exp Wound Infection/ OR exp INFECTION/ or infection.mp.) AND (antibiotic$.mp. or exp Anti-Bacterial Agents/) LIMIT to human AND English language.

Cochrane: (cat bites):ti,ab,kw 7 records none unique

Search Outcome

Medline - 25 papers found. Embase – 46 papers found. 3 of these papers were relevant. These are summarised in the table below:

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Elenbaas R M et al 1984, USA	12 Adult patients presenting with uninfected full-thickness wounds within 24 hrs of injury. Placebo vs oxacillin	Prospective, double blind, placebo-controlled study	Infection Rate	67% vs 0% (P =0.045)	This was a small study group.
Dire D J, 1991, USA	186 patients with 216 cat bite wounds / scratches over 2 years. Initially non infected bite wounds. Placebo vs antibiotic	Prospective survey	Infection rate: Puncture wounds	Infection rate:18% vs 3% (p=0.085)	The study focused on wound type and depth, as risk factors of wound infection. Did not specify antibiotic administered, I.V antibiotics were not included in the study.
			Infection rate: full thickness wounds	Infection rate:17% vs 3% (p=0.268)
			Infection rate: lower extremity wounds	Infection rate: 33% vs 0% (p=0.071)
Mitnovetski S, Kimble F, 2004, Australia	41 patients with cat bites of the hand seen over 3 years Combination of i.v Benzylpenicillin and Flucloxacillin effective in conjunction with surgical treatment	Observational	Infection rate with and without antibiotics	2% vs 28%.	Small group of patients. Not all patients were adults. Accuracy of data checked by questionnaire of which response rate was 46%. 12 % did not receive antibiotic treatment. More females than males.

Comment(s)

The studies found are all small and have significant methodological flaws. This area requires further appropriately designed RCTs

Clinical Bottom Line

Antibiotic prophylaxis should be given to all cat bite wounds that are deeper than superficial.

References

1. Elenbaas R.M, McNabney W.K, Robinson W.A, Evaluation of prophylactic oxacillin in cat bite wounds. Annals of Emergency Medicine: Mar 1984 13 (3), 155-157.
2. Daniel J Dire, Cat bite wounds: Risk factors for infection, Annals of Emergency Medicine: 1991, 20 (9) 973-979.
3. Mitnovetski S & Kimble F, Cat bites of the hand: ANZ Journal of Surgery: 2004, 4; 859-862