41. Chlamydia & Mycoplasma

Question 1

Chlamydia general characteristics?

Answer 1

gram negative

obligate intracellular

unique developmental cycle

ubiquitous to humans and animals

highly conserved small genome (highly reombinant)

Question 2

chlamydia growth/metab

Answer 2

• EB = spore-like for extracellular survival/ transmission and is metab. Dormant
• after internalization becomes RB = less dense, grow in contact w/inclusion membrane, metabolically active (multiplies by binary fission), NON infectious
• late differentiation RB>EB 20-40 hrs post infection, outer memb rigidification and condensing of chromosomal DNA
• fully mature inclusion has 1000 EBs and 1+ inclusion per cell
• cycle closed when inclusion and infected host cell lyse (or inclusion is exocytosed)

Question 3

chlamydia pathogenesis

Answer 3

Secretion/translocation of chlamydial effector protein into the host cell is key to pathogenesis:
- type III secretion (T3S) (early T3S effectors assoc w/EBRB; mid assoc w/growth; late assoc w/RB detachment / T3S disruption and late RBEB)
- autotransport (T5S)
- outer membrane blebs
Primary infection is freq asymptomatic and responds to Abx, pathology caused by inflammatory response
Chronic infection due to extensive remodeling and scarring of tissue often at remote sites
Repeat infection or persistence common

Question 4

chlamydia virulence factors

Answer 4

• cytotoxins related to clostridial cytotoxins

- co-option of metabolites from the host and local microbiota promotes chlamydial growh**

Question 5

chlamydia disease

Answer 5

• Long-lasting in the absence of treatment
• repeat infections common
• often asymptomatic

Question 6

C. trachomatis pathogenesis?

Answer 6

Direct contact, house flies; enhanced by poor hygienic conditions; genital: 10% of sexually active adults

Question 7

C.trachomatis disease?

Answer 7

Primary = inclusion conjunctivitis
Repeated = follicular conjunctivitis (may resolve = immunity)
Chronic = trachoma (pannus, blindness, trichiasis)
Ophthalmia neonatorum = 5-12 days post-natal; abx eye drops at delivery
Genital  PID, ectopic, infertility

Question 8

C.trachomatis treatment?

Answer 8

Primary = Abx

But Abx therapy has no effect past childhood! (disease is immune-response mediated)

Question 9

c. pneumoniae disease?

Answer 9

Common cold-like sxs to atypical CA-PNA

• chronic infection (bronchitis, asthma, COPD exacerbation)
• disseminated chronic infections (arthritis, AAA, stroke, atherosclerosis)

Question 10

C.penumoniae dx and tx?

Answer 10

dx Not usually attempted (Ag possible)

10-14 days doxycycline, erythromycin, quinolones

Question 11

C.psittaci disease?

Answer 11

Flu-like to severe pna-like syndrome

Avian, occupational hazard

Question 12

C. psittaci dx and tx?

Answer 12

Rarely dx
- CF test, hx of bird exposure

-Doxycycline, tetracycline
B-list bioweapon

Question 13

mycoplasma characteristics?

Answer 13

Broad group, 100+ species

• wall-less pleiomorphic bacteria, evolved from Gram+ by mutational loss
• few pathogenic to humans
• fastidious orgs (difficult to manipulate in vitro)

Question 14

mycoplasma virulence factors?

Answer 14

• hemolysins (alpha or beta)
• surface structures (attachment to ciliated epith cells of respiratory tract)
• polysaccharide capsule

Question 15

M. pneumoniae general characteristics?

Answer 15

• super tiny colonies
• mulberry colonies
• Leading cause of pna in school-age kids and young adults

Question 16

M. pnemoniae pathogenesis and virulence factors?

Answer 16

Some immune response is beneficial (IgM, IgG, CMI)
BUT 50% develop cold agglutinins

• CARDS (community acquired respiratory distress syndrome) toxin of M.pneumoniae: ADP ribosylating and vacuolating toxin

Question 17

M. pneumoniae disease??

Answer 17

Cough, malaise, fever, CA-PNA = walking pneumonia

Question 18

M. pneumoniae dx and tx?

Answer 18

Serology and PCR (because hard to culture): IgG or IgM by ELISA

• Doxycycline
• ciproflaxin
• erythromycin
• azithromycin
• levoflaxin

Question 19

M. hominis, M. genetalium & U. urealyticum?

Answer 19

Members of normal GU flora

Opportunistic pathogens

STI – PID?
Spontaneous abortions?
Non-gonococcal urethritis (10%) - asymptomatic

Question 20

M. fermentans & M. petrans?

Answer 20

Assoc w/HIV infection (HIV grows better in vitro if host cells are already infected w/these mycoplasma, and assoc w/AIDS pts)

Why assoc w/HIV?

1. mycoplasma are opportunistic
2. mycoplasma infection enhances HIV virulence
3. AIDS-assoc mycoplasma are pathogenic in their own right