6. Fastidious, intracellular and other miscellaneous bacteria

Fastidious

Microbe that requires specific, enriched growth conditions (fussy)

Respiratory fastidious microbes WITH ROUTINE VACCINE

Corynebacterium diphtheriae: Diphtheria

Bordetella pertussis: Whooping cough

Haemophilus influenza: Hib

Respiratory fastidious microbes WITHOUT routine vaccine

Legionella pneumophila: Legionnaire’s Disease

Mycoplasma pneumonia: “Walking” pneumonia

Fastidious microbe that can case meningitis

Listeria monocytogenes: Listeriosis (crosses placenta)

STI that is fastidious

Chlamydia trachomatis: Chlamydia

Diptheria is caused by

Corynebacterium diphtheriae

Respiratory diphtheria

causes fever, sore throat, adenopathy, and PSEUDOMEMBRANE

Respiratory diphtheria fatality

5-10%

Diphtheria toxin

Potent prophage-coded diphtheria toxin

Diphtheria toxin is only produced by

lysogenized strains

Mechanism of diphtheria toxin

blocks ribosomes from making proteins

Diphtheria toxin is negatively regulated by

iron

How does iron impact diphtheria toxin

iron is corepressor so it inhibits toxin production when in sufficient amounts.

When iron is low

operon is expressed and diphtheria toxin produced

Diphtheria pseudomembrane

Thick covering in the back of throat, tonsils, pharynx, nasopharynx

Issue with pseudomembrane

causes respiratory/airway obstruction 

Most common cause of death is severe diphtheria

myocarditis

how does diphtheria cause myocarditis

Toxin damages myocytes (heart muscle cells)

diphtheria cranial neuropathy

Diphtheria toxin damages myelin sheath of nerves

Diphtheria kidney damage

mediated by toxin that causes kidney injury and even failure

diphtheria treatment

Penicillin + anti-toxin

diphtheria prevention

DTaP (Diphtheria, Tetanus, Pertussis) vaccine

why is diphtheria so rare in US

because of effective Toxoid vaccine

Diphtheria toxoid is sensitive to

inactivated by heat or chemical

DTaP contains

inactivated tetanus toxin to stimulate immune response to toxin

Bordetella pertussis

causes whooping cough c

risk of whooping cough is greatest in

children under 1 year old

mortality of whooping cough before mass vaccination

21-31%

B. pertussis adhesins

Major colonizing factor for nasopharyngeal

toxins of b. pertussis

pertissus toxin
tracheal cytotoxin

Pertussis toxin

causes increase in respiratory secretions and mucus, leading to cough

Pertussis toxin mechanism

Unregulated activation of adenylate cyclase causing INCREASE IN cAMP!!

tracheal cytotoxin

paralyzes cilia causing the paroxysmal cough (whooping)

tracheal cytotoxin interferes with

secretions clearance via cilia paralysis in the trachea

actual whooping cough is called

paroxysmal cough

Diagnosis of B. pertussis

PCR most sensitive bc too hard to culture

During which phase of whooping cough infection is bacterial load the highest (MOST INFECTIOUS PHASE)

catarrhal (no cough yet, just cold symptoms)

paroxysmal phase of B. pertussis infection

later phase when you actually have the whooping cough symptoms

Issue with cararrhal phase and paroxysmal phase

you are most contagious in catarrhal phase BEFORE whoops so you may be spreading it

1948 has sharp decrease in whooping cough from the

DTP vaccine

1992 whooping cough

very very low because of DTaP

2005 whooping cough

Tdap

What year has had the highest incidence of whooping cough since 1995

2012

all pregnant women should receive which vaccine

Tdap

Capitals in DTaP vs Tdap

capital correspond to larger dose for more protection

Why do young children get DTaP vs Tdap

they need higher doses because they are highest risk group

Which serogroup of Haemophilus influenzae is most serious

Type b (Hib)

Virulence factor of Hib

Phosphoribosylribitol phosphate (PRP) capsule (antiphagocytic)

Phenomenon with H. influenzae on agar

grows as satellite colonies around Staphylococcus aureus, which secretes required growth factors

H. influenzae is major disease among

infants and elderly

Before vaccine development. Hib caused

90% of meningitis in children 6 months – 2  yrs

Hib epiglottitis

Inflammation of cartilage flap covering windpipe (trachea) which can be lifethreatening

Hib is also associated with

bacteremia so it can disseminate to other places like lungs, ears, joints, etc

Treatment of Hib

Broad-spectrum antibiotics (cephalosporins, azithromycin)

Polysaccharide capsule vaccine for Hib

poorly immunogenic, particularly in children <2 yrs of age

Hib Conjugate vaccine (PRP-tetanus toxoid)

is considerably more effective even in young infants

Conjugate vaccine causes

T-dependent immune response due to protein carrier

Protein carrier (tetanus toxoid) in conjugate vaccine

strong antigen so causes T-dependent response for better memory

Effective Hib vaccine has caused

decrease in incidence by 90%

Hib vaccine decreases

respiratory droplet transmission and decreases invasive disease risk

Haemophilus influenzae and H. aegyptius- Bacterial conjunctivitis

Acute purulent conjunctivitis (pink eye) common in children and adults,

Why was L. pneomophila named legionella

Killed 34 at an American Legion convention so when identified it wss named after it

L. pneumophila growth

fastidious and intracellular

L. pneumophila is best visualized with

silver stains

90% of legionellosis is caused by

L. pneumophila infection

L. pneumophila is found in

aquatic environments like Water cooling towers, air conditioning systems, shower heads, water fountains

L. pneumophila is transmitted via

inhalation of contaminated water aerosols.

2 type of legionellosis

pontiac fever
legionnaire’s disease

Pontiac fever

milder form of legionellosis with NO lung involvement

Legionnaire’s diease

a severe form of legionellosis characterized by pneumonia and potential respiratory failure.

Major predisposing factors to legionnaires disease (severe pneumoniae)

Chronic lung diseases, smoking, older males

Mortality of legionnaires disease (severe pneumoniae)

10-15% mortality

Rapid testing for legionnaires

Antigen detection in the urine by enzyme immunoassay (ELISA)

Smallest free living organisms

mycoplasma

Mycoplasma

Lack cell wall thus do not Gram stain

Mycoplasma are highly dependent on

sterols

Why are mycoplasma so dependent on sterols

They require sterols for maintaining membrane integrity and fluidity due to the absence of a cell wall.

Mycoplasma colonies

fried egg appearance

M. pneumoniae- Tracheobronchitis

70-80% of infections

M. pneumoniae- pneumonia makes up about

10%  of infections

M. pneumoniae- pneumonia common in

Teens, young adults

M. pneumoniae- pneumonia is aka

“Atypical” or “walking” pneumonia

Walking pneumonia

less severe but long duration

Mycoplasma genitalium

sexually transmitted Non-gonococcal urethritis (NGU)

Mycoplasma hominis

associated with Pyelonephritis (KIDNEY)

Ureaplasma urealyticum

Same Family, different Genus causes NGU, pyelonephritis

Mycoplasma infection treated with

Tetracycline

Listeria monocytogenes grows at

5 – 40^oC (refrigerator temperature!!!)

Listeria monocytogenes has tropism for

fetus and placenta of most animals

GI manifestation of listeriosis

Gastroenteritis often from eating processed meat products

If listeriosis crosses the BBB

Meningoencephalitis

If listeriosis crosses the placenta

maternal fetal infections

Listeriosis in healthy adults

often asymptomatic or NON-INVASIVE gastroenteritis

Invasive listeriosis

Meningitis is common in neonates and older adults

Leading cause of meningitis in cancer and renal transplant patients

Listeria monocytogenes

Listeriosis is especially common in

pregnant women

Transplacental transmission of listeriosis

can result in miscarriage or stillbirth

Listeriosis in neonates

oCNS is most often affected, resulting in meningitis

Why is Chlamydiaceae fastidious

Cannot produce ATP & must scavenge from host

Chlamydia trachomatis

causes STI and OCULAR disease