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Skin and Soft-Tissue Infections
• Staphylococcus aureus
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- Boils: Walled off from body with fibrin
- Can produce toxic shock superantigen
- MRSA: Methicillin-resistant S. aureus
- Major cause of nosocomial infections (in hospitals)
- Some strains make exfoliative toxin (scalded skin syndrome).
Figure 26.2
Skin and Soft-Tissue Infections
• Streptococcus pyogenes
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- Best known for causing sore throats and
immunological sequelae, such as rheumatic fever
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- Also necrotizing fasciitis (“flesh-eating” disease)
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- Many prophages carry virulence factors.
Figure 26.3
Impetigo S. pyogenes or Staph aureus
Skin and Soft-Tissue Infections
• Viruses cause a maculopapular skin rash.
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- Usually infects through respiratory tract
- Paramyxovirus: Rubeola (“measles”)
- Herpes virus: Chickenpox, shingles
- Togavirus: Rubella (“German measles”)
Figure 26.4
measles
Chicken pox
Respiratory tract infections
Figure 26.5
S. pneumoniae
Scarlet fever
normal
TB
show tubercules
diphtheria
Gastrointestinal tract
infections
Salmonellosis in the US
norovirus
Genitourinary tract
infections
Sexually Transmitted Diseases
• Syphilis
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- Caused by the spirochete Treponema pallidum
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- Primary syphilis: Chancre at site of infection
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- Secondary syphilis: Generalized rash
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- Tertiary syphilis: Effects on heart and CNS
Figure 26.11
Sexually Transmitted Diseases
• Chlamydia
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- Most frequently
reported STD in U.S.
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- Caused by unusual
Gram-negative bacteria Chlamydia trachomatis
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- Chlamydia pneumoniae
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- Obligate
intracellular
pathogens
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- Both cause STDs,
as well as pneumonia and
trachoma of the eye.
Figure 26.12
Figure 18.45
Chlamydia on fallopian tube tissue
Sexually Transmitted Diseases
• Gonorrhea
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- Caused by the Gram-negative diplococcus
Neisseria gonorrhoeae
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- Most infected men exhibit symptoms, while most
women are asymptomatic.
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- Binds to CD4+ T cells, inhibiting T-cell activation
Figure 26.13
Central Nervous System Infections
• Meningitis
– - Infection of membrane surrounding brain
– - Some bacteria cross blood-brain barrier.
• - Streptococcus pneumoniae
• - Haemophilus influenzae
• - Neisseria meningitidis
Figure 26.16D
- Has thick capsule and type IV pili Figure 26.16B
- Dangerous if gets into bloodstream
- Crosses from capillary into cerebrospinal fluid
- Once in meninges, very difficult to treat
- Effective vaccine to capsule components
West Nile virus
Figure 26.18
Figure 26.19
Central Nervous System Infections
• Animation: Retrograde Movement of Tetanus
Toxin to an Inhibitory Neuron
Click box to launch animation
• Prions
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- Proteinaceous infectious particles
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- Cause spongiform encephalopathies
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- Improperly folded proteins form
aggregates
that damage the brain.
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- Most mammals suffer from these diseases.
Figure 26.20
Systemic infections
Figure 26.23
Figure 26.24
Lyme disease
Lyme disease
Figure 26.25
Lyme disease
deer ticks
Deer tick eating
Lyme disease rash
Lyme Disease
• Borrelia burgdorferi
• Spirochete
• Obligate Intracellular pathogen
Borrelia burgdorferi
• 1.5Mbp
• Strange genomic layout
– Linear chromosome (900 kb)
– Has over 20 circular AND linear plasmids
• Genome decay in obligate intracellular bacteria
• Loses many biosynthesis pathways (why make it if
you can get it from the host)
Rocky Mt. spotted fever
Vaccine LYMErix
• Recombinant Outer surface
protein A (OspA)
– Your body doesn’t make
antibodies to OspA normally
– OspA only expressed in unfed
ticks, not in fed ticks or host
• Temperature is the trigger to
stop OspA and start making
OspC
– other triggers for making
virulence proteins are pH and
Fe starvation
How the vaccine works
• Bacterial migration from midgut to salivary glands is
inhibited when ticks feed on OspA (and also in OspC)
immunized mice
• So immune serum appears to kill the bugs in the tick
or prevent migration
Rocky mountain spotted fever
Rickettsia inside cells
(arrows)
leprosy