Microbiology of infected poison ivy dermatitis

We report the aerobic and anaerobic microbiology of secondarily infected po ison ivy dermatitis, The study involved retrospective review of clinical an d microbiology laboratory records of patients with secondarily infected poi son ivy lesions, Bacterial growth was noted in 33 specimens. Aerobic or fac ultative anaerobic bacteria only were present in 18 (55%) patients, anaerob ic bacteria only in seven (21%), and mixed anaerobic-aerobic bacteria in ei ght (24%). Forty-five isolates were recovered (1.4 per specimen): 27 aerobi c or facultative anaerobic bacteria, and 18 strict anaerobes. The predomina nt aerobic and facultative anaerobic bacteria were Staphylococcus aureus (1 3 isolates) and group A beta-haemolytic streptococci (six). The predominant anaerobes were Peptostreptococcus spp, (seven isolates), pigmented Prevote lla and Porphyromonas spp. (four) and Fusobacterium spp. (two). Single bact erial isolates were recovered in 18 (55%) patients, eight of which were S, aureus. Nineteen of the organisms isolated from 16 (48%) patients produced the enzyme beta-lactamase. Organisms that resided in the mucous membranes c lose to the lesions predominated in those infections. Enteric Gram-negative rods and Bacteroides fragilis group predominated in leg and buttock lesion s. Group A beta-haemolytic streptococci, pigmented Prevotella and Porphyrom onas and Fusobacterium spp, were most frequently recovered from lesions of the finger, face and neck, The polymicrobial aetiology of secondarily infec ted poison ivy lesions, and the association of bacterial flora with the ana tomical site of the lesions, are demonstrated.