Others - Mycoplasma/Chlamydia/Mycobacterium/Obligate Intracellular Pathogens

Question 1

Why is Gram stain not used for Mycoplasma?

Answer 1

It has no cell wall and hence cannot be visualised via gram stain. This also results in its resistance to cell wall synthesis inhibitors.

Question 2

Clinical presentation of M. pneumoniae?

Answer 2

URTIs - Walking pneumonia (Mild pneumonia where patients are mobile and can continue spreading disease)

Question 3

Clinical presentation of M. hominis and U. urealyticum?

Answer 3

Non-gonococcal urethritis, UTIs

Question 4

Treatment for Mycoplasma?

Answer 4

Erythromycin

Question 5

Why do we not use Gram stain for Chlamydia?

Answer 5

Little peptidoglycan in cell wall, unable to visualise clearly. Resistant to cell wall synthesis inhibitors.

Question 6

How is Chlamydia classified?

Answer 6

By surface antigens

Question 7

How is C. trachomatis (A-C) spread and is there immunological memory?

Answer 7

Spread via 3Fs (Flies, fingers, fomites). No immunological memory, could lead to repeated infections

Question 8

Clinical presentation of C. trachomatis (A-C)?

Answer 8

Trachoma
- Chronic inflammation of eyelids -> Curling of eyelashes -> Cornea infection
- Pannus formation -> Blindness

Question 9

How does C. trachomatis (L1-L3) spread?

Answer 9

Sexually transmitted

Question 10

Clinical presentation of C. trachomatis (L1-L3)?

Answer 10

Lymphogranuloma venerum
Primary lesion on genitalia that can spread via lymphatics and cause rectal strictures and elephantiasis

Question 11

Clinical presentation of C. trachomatis (D-K)?

Answer 11

STD
Males: Urethritis, dysuria (possible), infection of epididymis or rectum (homosexual males)
Females: Endocertival canal infection that could cause opthalmia neonatarum, ascending infection to cause reactive arthritis or urethritis/proctitis

Question 12

How is Chlamydia trachomatis treated?

Answer 12

Doxycycline

Question 13

Testing for C. trachomatis is done in conjunction with which other bacteria?

Answer 13

N. gonorrhoeae

Question 14

Ch. pssitaci is spread by ___ and initially causes ___ that can lead to ___

Answer 14

Birds, flu-like illness, pneumonia and meningitis

Question 15

Ch. pneumoniae causes a mild form of ___

Answer 15

Community acquired pneumonia

Question 16

What stains are used for Mycobacterium?

Answer 16

Ziehl Neelsen Stain (ZN Stain) and Auramine stain (fluorescent microscopy)
Acid-Fast Bacilli culture (Takes 8 weeks)

Question 17

Clinical presentations of M. tuberculosis?

Answer 17

Primary TB: Primary infection with foci in lower part of upper lobe or upper part of lower lobe (Ghon focus). Usually clinically silent.
Secondary TB: Reacitvation/reinfection -> Large exuberant granulomas with caseous necrosis (Assman’s focus)
Miliary TB: Disseminated by blood systemically

Question 18

General symptoms of M. TB?

Answer 18

Fever, chronic cough with blood, night sweats, pulmonary disturbances, enlarged lymph nodes, possible joint and bone involvement

Question 19

Treatment for M. tuberculosis?

Answer 19

RIPES
Rifampicin, Isoniazid, Pyrazinamide, Ethambutol, Streptomycin

Question 20

Clinical presentation of M. leprae?

Answer 20

General presentation: Paralysis, anaesthesia, trophic ulcers, Charcot joints
Tuberculoid leprosy: Th1 response
Lepromatous leprosy: Th2 response

Question 21

Which cells do Rickettsia affect and damage?

Answer 21

Endothelial cells

Question 22

Which cells does Coxiella replicate in?

Answer 22

Phagolysosomes inside marcophages

Question 23

Clinical presentation of Rickettsia?

Answer 23

General presentation: Fever, haemorrhagic lesions and possible shock due to vascular damage
Typhus type: Spread by lice
Spotted Fever: Spread by ticks
Scrub typhus type: Spread by chigger

Question 24

Treatment for Rickettsia?

Answer 24

Doxycycline

Question 25

How is Coxiella spread?

Answer 25

Airborne droplets or drinking infected milk

Question 26

Clinical presentation of Coxiella?

Answer 26

Acute Q fever: Increased susceptiblity to viral infections Chronic Q fever: Endocarditis (culture negative endocarditis)

Question 27

Treatment for Coxiella?

Answer 27

Doxycycline

Question 28

B. recurrentis causes ___ due to ___. Diagnosed by ____ and is treated with ___

Answer 28

Relapsing fever, constant antigenic variation, peripheral blood film, doxycycline

Question 29

Borrelia burgdorferi causes ___ with ___. Diagnosed by ___ and is treated with ___.

Answer 29

Lyme disease, erythema chronic migrans, serology, doxycycline

Question 30

How does Treponema palladum look like?

Answer 30

Thin helical spiral bacteria

Question 31

Clinical presentation of Treponema palladum?

Answer 31

Primary syphilis: Painless chancre at cervix/penis with enlarged lymph nodes Secondary syphilis: Diffused rashes across palms and soles, warty lesions (condylomata lata) at moist areas Tertiary syphilis: Cardiovascular syphilis, meningitis, gummatous syphilis etc. Congenital syphilis: Hutchinson's triad

Question 32

What is characteristic of congenital syphilis?

Answer 32

Hutchinson's Triad: 1. Deafness 2. Interstitial keratitis of cornea 3. Notched incisors (Teeth)

Question 33

Treatment of Treponema Pallidum?

Answer 33

Benzylpenicillin

Question 34

Leptospira is chronically excreted in ___ and enters via ___.

Answer 34

Rat urine, exposed mucosa

Question 35

Clinical presentation of Leptospira?

Answer 35

Phase I: Septicaemia, Phase II: Immune Bacteraemia leptospirosis: Flu-like fever that will lead to aseptic meningitis Icteric leptospirosis: Often fatal with haemorrhage, jaundice and renal failure

Question 36

What is another name for Icteric Leptospirosis?

Answer 36

Weil's disease

Question 37

Helicobacter Pylori infects ___ in humans

Answer 37

Gastric mucosa

Question 37

Treatment for Leptospira?

Answer 37

Benzylpenicillin

Question 38

Clinical presentation of Helicobacter Pylori? Associated with?

Answer 38

Chronic inflammation predisposes to peptic ulcers and cancer Causes dyspepsia, abdominal pain, flatulence, bad breath Associated with MALT lymphoma

Question 39

Treatment for H. pylori?

Answer 39

Quadruple therapy: Omeprazole, Clarithromycin, Metronidazole, Bismuth

Question 40

Virulence factors of H. pylori ___ structure allows it to burrow into mucosa, preventing flushing away by gastric motility Produces ___ that breaks down ___ to form ___, allowing it to persist in ___ environment Produces ___ that causes ___ and ___ and ___ Proteases release damage gastric mucosa and release nutrients for continued colonisation

Answer 40

Spiral Urease, urea, NH3, acidic Bacterial PAF, local vasoconstriction, thrombotic occlusion, reduced mucosal regeneration

Question 41

Campylobacter appears like a ___ in microscopy

Answer 41

Seagull

Question 42

Campylobacter's mode of transmission?

Answer 42

Faecaloral transmission via infected poultry

Question 43

Clinical presentation of Campylobacter? Complications?

Answer 43

Incubation period that presents with initial flu-like illness that can cause abdominal pain and diarrhoea Complications: Guillain-Barre Syndrome

Question 44

What is Campylobacter sometimes misdiagnosed as?

Answer 44

Appendicitis

Question 45

Treatment of Campylobacter?

Answer 45

Erythromycin

Question 46

Types of Mycobacterium Leprae

Answer 46

1. Tuberculoid leprosy (Th1) 2. Lepromatous leprosy (Th2)

Question 47

Test for Mycobacterium TB

Answer 47

Mantoux test *CANNOT use Gram stain (Can use AFB or Auramine stain)

Question 48

Primary TB is characterised by ___ and ___. Is often ___.

Answer 48

Ghon focus = small foci of inflammation comprising several MTC surrounded by a dense granuloma Primary complex = Ghon focus + enlarged regional lymph notes Clinically silent

Question 49

Post Primary TB is due to ___ or ___. Can present in ___ in the body and presents as ___ with ___. Necrotic foci in lungs can be coughed out leading to ___.

Answer 49

Reinfection, reactivation Any organ Large exuberant granulomas, central caseous necrosis Cavitations

Question 50

Miliary TB occurs when bacteria is spread through the ___ and affects ___. Seen as ___ that show up well on ___ but not on ___.

Answer 50

Bloodstream, multiple organs Small white nodules (millet seeds), CT, X ray

Question 51

Clinical symptoms of TB

Answer 51

1. Pulmonary: Chronic cough, sometimes bloodstained with dyspnoea 2. CNS: Meningitis 3. Osteomyelitis and vertebral collapse Systemic features: Fever, night sweat and weight loss

Question 52

MTC are phagocytosed by ___, but survive and continue to replicate within the ___. They inhibit acidification by producing a ___. More monocytes are recruited but ___. ___ are also recruited, releasing ___ that causes increased activity of macrophages that kill microbes. Could lead to ___, ___, or ___.

Answer 52

Macrophages, phagolysosomes Cord factor Unable to kill the microbes Activated T lymphocytes, IFN-gamma Cure, latency or active TB

Question 53

What is TB misdiagnosed as?

Answer 53

Paragonimus westermani (lung fluke)