• Staphylococcus aureus• - 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).
Skin and Soft-Tissue Infections
Figure 26.2
• Streptococcus pyogenes• - Best known for causing sore throats and
immunological sequelae, such as rheumatic fever • - Also necrotizing fasciitis (“flesh-eating” disease)• - Many prophages carry virulence factors.
Skin and Soft-Tissue Infections
Figure 26.3
Impetigo S. pyogenes or Staph aureus
• Viruses cause a maculopapular skin rash.• - Usually infects through respiratory tract• - Paramyxovirus: Rubeola (“measles”)• - Herpes virus: Chickenpox, shingles• - Togavirus: Rubella (“German measles”)
Skin and Soft-Tissue Infections
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• - Caused by the spirochete Treponema pallidum• - Primary syphilis: Chancre at site of infection• - Secondary syphilis: Generalized rash• - Tertiary syphilis: Effects on heart and CNS
Figure 26.11
Sexually Transmitted Diseases
• Chlamydia• - Most frequently
reported STD in U.S. • - Caused by unusual
Gram-negative bacteria - Chlamydia trachomatis
• - Chlamydia pneumoniae
• - Obligate intracellular pathogens
• - 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• - Caused by the Gram-negative diplococcus
Neisseria gonorrhoeae• - Most infected men exhibit symptoms, while
most women are asymptomatic.• - Binds to CD4+ T cells, inhibiting T-cell activation
Figure 26.13
• Meningitis– - Infection of membrane surrounding brain– - Some bacteria cross blood-brain barrier.
• - Streptococcus pneumoniae• - Haemophilus influenzae• - Neisseria meningitidis
Central Nervous System Infections
- Has thick capsule and type IV pili- Dangerous if gets into bloodstream- Crosses from capillary into cerebrospinal fluid- Once in meninges, very difficult to treat- Effective vaccine to capsule components
Figure 26.16D Figure 26.16B
West Nile virus
Figure 26.18 Figure 26.19
• Animation: Retrograde Movement of Tetanus Toxin to an Inhibitory Neuron
Click box to launch animation
Central Nervous System Infections
• Prions• - Proteinaceous infectious particles• - Cause spongiform encephalopathies• - Improperly folded proteins form
aggregates that damage the brain.• - 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