Atypical organisms (Chlamydias/ Mycoplasmas)

Question 1

Name the 3 types of Chlamydias that you have learnt. They have same biological cycle but with different genetic components.

Answer 1

1. Chlamydia trachomatis
2. Chlamydophila pneumoniae
3. Chlamydophila psittaci

Question 2

Chlamydias are obligate intracellular with a biphasic development cycle. What does it mean by biphasic?

Answer 2

1. Elementary bodies (EB): metabolically inactive, infective, Extracellular;
2. Reticular bodies (RB): metabolically active, Reproductive

Question 3

There are 3 types of transmission method for Chlamydia trachomatis. Describe how Ocular serovars (A-C) work (3) and what are the clinical presentations.

Answer 3

Ocular serovars (A-C)：

• direct contact of secretions (hand-to-eye)
• indirect contact (towel sharing)
• eye-seeking flies

Clinical presentations
- trachoma (conjunctivitis > corneal scarring > blindness)

Question 4

Describe how Oculogenital serovars (D-K) of Chlamydia trachomatis work (2) and what are the clinical presentations (3).

Answer 4

Oculogenital serovars (D-K)

1. STD
2. Vertical transmission

Clincal presentations

• genital tract infections
• neonative conjunctivitis (sticky eye)
• pneumonia

Question 5

Other than Oculogenital serovars of Chlamydia trachomatis, _____________ serovars (LGV, L1-L3) also transmit the bacteria via STD. What is the clinical manifestation?

Answer 5

Lymphogranuloma venereum serovas;

Lymph node infections (form buboes)

Question 6

What is the mode of transmission of Chlamydophila penumoniae?

Answer 6

Respiratory droplets

Question 7

What are the clinical presentations in Chlamydophila penumoniae infections? Be specific. (2)

Answer 7

1. Atypical pneumonia: Bilateral pulmonary involvement with extra-pulmonary presentations (myocarditis, meningoencephalitis, reactive arthritis)
2. associated with atherosclerosis (controversial)

Question 8

What is the mode of transmission of Chlamydophila psittaci?

Answer 8

Zoonotic: psittacine birds e.g. parrots

> psittacosis/ parot fever

Question 9

Other than Chlamydophila penumoniae, infections of ______________ also presents with atypical pneumonia. Fever, headahce, diahhrea and altered mental state can be seen.

Answer 9

Chlamydophila psittaci

Question 10

How can Chlamydia in general be diagnosed? (3)

Answer 10

1. Culture: tissue culture - obligate intracellular
2. Serology: ELISA
3. PCR

Question 11

Treatment for Chlamydia. (3)

Answer 11

1. Macrolides (azithromycin)
2. Doxycycline
3. Ceftriaxone if tgt with Neisseria (common)

Question 12

____________ are the smallest extracellular bacteria.

Answer 12

Mycoplasmas

Question 13

Why does Mycoplasmas not seen on Gram stain and they lack response to antibiotics like penicillin?

Answer 13

They have no cell wall

Penicillin: anti-cell wall antibiotics

Question 14

What is the specific agar for Mycoplasma? What can be seen?

Answer 14

Eaton’s agar;

Fried egg colonies

Question 15

Name the Mycoplasma whose mode of transmission is by respiratory droplets with an inbucation of 3 weeks.

Answer 15

Mycoplasma pneuomoniae

Question 16

Name the 3 Mycoplasma whose mode of transmission is by STD or vertical.

Answer 16

1. Mycoplasma hominis
2. Mycoplasma genitalium
3. Mycoplasma urealyticum

Question 17

For Mycoplasma pneumoniae, list the clinical presentations and briefly describe. (2)

Answer 17

1. Atypical pneumonia, ranging from asymptomtic (walking pneumonia) to multi-lobar involvement
2. Patchy infiltration in X-rays

Question 18

In
1. Mycoplasma hominis
2. Mycoplasma genitalium 
2. Mycoplasma urealyticum .
What are their clinical presentations? (2)

Answer 18

1. GU tract infections

2. Neonatal pneumonia

Question 19

How can Mycoplasma bacteria infections be diagnosied

Answer 19

1. Culture: slow growing, fastidious (requires special medium )
2. Cold agglutinins (IgM): autoantibodies that clumps and lyse RBCs at cold temperatures
3. PCR

**Clinical findings are non-specific

Question 20

Treatment for Mycoplasma infections?

Answer 20

Macrolides

NOT beta-lactams!