Bite wound

Bite wounds may become infected with many different organisms but most commonly S. aureus, Pasteurella spp., S. anginosus group and beta-hemolytic streptococci.

The presence of squamous epithelial cells and absence of PMNs may indicate that the the organisms isolated may not reflect the true etiology of the infection.

Setup

Direct Examination

Gram stain

Culture

Media Incubation
Blood Agar (BA) CO2, 35°C x 48 hours
MacConkey Agar (MAC) O2, 35°C x 48 hours

Interpretation Examine plates after 24 and 48 hours incubation.

Any growth of S. aureus, Pasteurella spp., S. anginosus group, beta-haemolytic streptococci and Pseudomonas aeruginosa is significant.

For other organisms such as Enterobacteriaceae and other Gram negative bacilli, a significant result is determined by the isolation of a moderate to heavy predominant growth, or if growth correlates with the predominant organism seen on Gram stain.

Reporting

Gram stain

Report with quantitation the presence of pus cells, squamous epithelial cells and organisms.

Culture

Negative Report
“No growth” or “Normal skin flora”
Positive Report
Quantitate all significant isolates with appropriate sensitivities. If normal flora is also present, report with quantitation.

References H.D. Isenberg. 2004. Specimen Collection, Transport and Acceptability p. 2.1.1 – 2.1.28. In Clinical Microbiology Procedures handbook, 2nd Edition, Vol 1 ASM Press, Washington, D.C

H.D. Isenberg, 2004. Wound Cultures – Wound and Soft Tissue Cultures, p. 3.13.1.1 – 3.13.1.16. In Clinical Microbiology Procedures Handbook, 2nd Edition, Vol 1 ASM Press, Washington, D.C.

H.D. Isenberg. 2004. Culture for anaerobes p. 4.3.1 – 4.3.9 In Clinical Microbiology Procedures Handbook, 2nd Edition, Vol 1 ASM Press, Washington, D.C.

H.D. Isenberg. 2004. Examination of Primary Culture plates for anaerobic bacteria. p. 4.4.1 – 4.4.6 In Clinical Microbiology Procedures Handbook, 2nd Edition, Vol 1 ASM Press, Washington, D.C.

H.D. Isenberg. 2004. Incubation techniques for anaerobic bacteriology specimens. p. 4.5.1 – 4.5.4 In Clinical Microbiology Procedures Handbook, 2nd Edition, Vol 1 ASM Press, Washington, D.C.

Cumitech 5A Practical anaerobic bacteriology December 1991