Cellulitis develops when micro-organisms gain entry to the dermal and subcutaneous tissues via disruptions in the cutaneous barrier. Beta-haemolytic streptococci and Staphylococcus aureus are most commonly implicated as the causative agents of cellulitis.[3]Sigurdsson AF, Gudmundsson S. The etiology of bacterial cellulitis as determined by fine-needle aspiration. Scand J Infect Dis. 1989;21(5):537-42.
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[4]Bernard P, Bedane C, Mounier M, et al. Streptococcal cause of erysipelas and cellulitis in adults. A microbiologic study using a direct immunofluorescence technique. Arch Dermatol. 1989 Jun;125(6):779-82.
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[5]Eriksson B, Jorup-Ronstrom C, Karkkonen K, et al. Erysipelas: clinical and bacteriologic spectrum and serological aspects. Clin Infect Dis. 1996 Nov;23(5):1091-8.
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[6]Lutomski DM, Trott AT, Runyon JM, et al. Microbiology of adult cellulitis. J Fam Pract. 1988 Jan;26(1):45-8.
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[7]Leppard BJ, Seal DV, Colman G, et al. The value of bacteriology and serology in the diagnosis of cellulitis and erysipelas. Br J Dermatol. 1985 May;112(5):559-67.
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[8]Kielhofner MA, Brown B, Dall L. Influence of underlying disease process on the utility of cellulitis needle aspirates. Arch Intern Med. 1988 Nov;148(11):2451-2.
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[9]Bernard P, Toty L, Mounier M, et al. Early detection of streptococcal group antigens in skin samples by latex particle agglutination. Arch Dermatol. 1987 Apr;123(4):468-70.
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[10]Sachs MK. The optimum use of needle aspiration in the bacteriologic diagnosis of cellulitis in adults. Arch Intern Med. 1990 Sep;150(9):1907-12.
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[11]Duvanel T, Auckenthaler R, Rohner P, et al. Quantitative cultures of biopsy specimens from cutaneous cellulitis. Arch Intern Med. 1989 Feb;149(2):293-6.
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[12]Howe PM, Fajardo JE, Orcutt MA. Etiologic diagnosis of cellulitis: comparison of aspirates obtained from the leading edge and the point of maximal inflammation. Pediatr Infect Dis J. 1987 Jul;6(7):685-6.
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[13]Gunderson CG, Martinello RA. A systematic review of bacteremias in cellulitis and erysipelas. J Infect. 2012 Feb;64(2):148-55.
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[14]Chira S, Miller LG. Staphylococcus aureus is the most common identified cause of cellulitis: a systematic review. Epidemiol Infect. 2010 Mar;138(3):313-7.
http://www.ncbi.nlm.nih.gov/pubmed/19646308?tool=bestpractice.com
However, other micro-organisms can uncommonly result in cellulitis. Usually this occurs in a host with altered immunity or as the result of a specific exposure.
The pathophysiology of cellulitis has not been well studied. The burden of organisms in cellulitis appears to be low.[15]Hook EW 3rd, Hooton TM, Horton CA, et al. Microbiologic evaluation of cutaneous cellulitis in adults. Arch Intern Med. 1986 Feb;146(2):295-7.
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Some have speculated that the pyrogenic exotoxins produced by beta-haemolytic streptococci may contribute to the clinical findings in cellulitis.[16]Baddour LM, Bisno AL. Recurrent cellulitis after coronary bypass surgery. JAMA. 1984 Feb 24;251(8):1049-52.
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There is evidence of local production of inflammatory cytokines by keratinocytes.[17]Kupper TS. Immune and inflammatory processes in cutaneous tissues. Mechanisms and speculations. J Clin Invest. 1990 Dec;86(6):1783-9.
http://www.jci.org/articles/view/114907/pdf
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Interaction between surface proteins of Streptococcus pyogenes and adhesions on the surface of keratinocytes and Langerhans cells may be a requirement for infection to develop.[18]Okada N, Pentland AP, Falk P, et al. M Protein and protein F act as important determinants of cell-specific tropism of Streptococcus pyogenes in skin tissue. J Clin Invest. 1994 Sep;94(3):965-77.
http://www.jci.org/articles/view/117463
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In many instances, tinea pedis may cause a disruption in the cutaneous barrier and allow entry to offending bacterial organisms.[19]Semel JD, Goldin H. Association of athlete's foot with cellulitis of the lower extremities: diagnostic value of bacterial cultures of ipsilateral interdigital space samples. Clin Infect Dis. 1996 Nov;23(5):1162-4.
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