Page 64 - Review of Medical Microbiology and Immunology ( PDFDrive )

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mebooksfree.com mebooksfree.com Activation of complement Bacteria enter skin Phagocytosis by mebooksfree.com mebooksfree.com
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CHAPTER 8 Host Defenses
53

via alternative pathway

C3b
C5,6,7,8,9
Macrophages
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Neutrophils
form
opsonizes
C5a attracts
membrane
bacteria,
neutrophils
which enhances
attack complex
phagocytosis
that lyses
bacteria
by neutrophils
Cytokine
epitopes
production
and
stimulate
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mebooksfree.com mebooksfree.com mebooksfree.com pores in the membranes of bacteria, which kills them. mebooksfree.com
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Chemokines (e.g.,
Antibody-
Cell-
Tumor necrosis
Interleukin-6
Interleukin-1
IL-8, MIP) attract
mediated
mediated
factor induces
induces acute-
neutrophils and
induces fever
immunity
immunity
inflammation
phase proteins
macrophages
FIGURE 8–1
Early host responses to bacterial infection.
The nonspecific protection in the gastrointestinal tract
includes hydrolytic enzymes in saliva, acid in the stomach,
Neutrophils and Paneth cells in the intestinal crypts contain
and various degradative enzymes and macrophages in the
tract produces different defensins called β-defensins. The
small intestine. The vagina of adult women is protected by
the low pH generated by lactobacilli that are part of the
mechanism by which defensins distinguish between bacte-
normal flora. one type of defensin (α-defensins), whereas the respiratory
rial membranes and human cell membranes is unknown.
The bacteria of the normal flora of the skin, nasopharynx,
Additional protection in the gastrointestinal tract and in
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mebooksfree.com mebooksfree.com mebooksfree.com Bacteria Commonly Causing Infection Associated with mebooksfree.com
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colon, and vagina occupy these ecologic niches, preventing
the lower respiratory tract is provided by defensins. These
are highly positively charged (cationic) peptides that create
pathogens from multiplying in these sites. The importance of
TABLE 8–1 Damage to Skin and Mucous Membranes Predisposes to Infection Caused by Certain Bacteria
Site of Infection
Predisposing Factor
Predisposing Factor
Staphylococcus epidermidis, Staphylococcus aureus
Skin
Intravenous catheters
Diabetes
Skin
Burns
Pseudomonas aeruginosa
Cystic fibrosis Skin S. aureus 1 2
Respiratory tract
P. aeruginosa
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mebooksfree.com mebooksfree.com mebooksfree.com Viridans streptococci, Capnocytophaga gingivalis mebooksfree.com mebooksfree.com
Actinomyces israelii
Gingival crevice
Trauma to jaw
Viridans streptococci
Dental extraction
Oropharynx
Oral mucositis secondary to cancer
Mouth but also entire gastrointestinal
tract
chemotherapy
1
Bacteria less commonly involved include Burkholderia cepacia and Stenotrophomonas maltophilia.
2
Viridans streptococci do not cause local infection after dental extraction but can enter the bloodstream and cause endocarditis.
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