Fastidious and Anaerobes

Question 1

What does fastidious mean?

Answer 1

difficult to grow in the laboratory
Needs enriched agar plates/CO2 enriched atmosphere
Non-culture methods for identification

Question 2

Name examples of fastidious gram-negative bacilli

Answer 2

Haemophilus influenzae (facultative anaerobe)
Legionella pneumophila (aerobe)
Helicobacter pylori (microaerophilic)

Question 3

Describe Haemophilus influenzae

Answer 3

Can colonise upper airway
Capsulated strains are associated with meningitis in children
Vaccine - H. influenzae with the type “b” capsule (Hib)

Question 4

What are the clinical syndromes of Haemophilus influenzae?

Answer 4

Pneumonia
Meningitis
Otitis media

Question 5

How can Haemophilus influenzae be cultured?

Answer 5

Growth at ~5% CO2
Chocolate agar plate (heat-lysed horse blood)
Absolute requirement for NAD (factor V) and a source of haem (factor X).

Question 6

Describe Legionella pneumophila

Answer 6

Causes Legionnaire’s Disease and Pontiac Fever
Waterborne = air conditioning systems, water cooling towers, hot tubs, shower heads
16 serogroups of L. pneumophila, serogroup 1 accounts for the majority of human infections (approx. 85%)
Public health - management of cases, contacts and outbreaks

Question 7

How can Legionella pneumophila be cultured?

Answer 7

Optimum growth 25-42OC
Culture: selective agar (L-cysteine for growth) BCYE agar
Non-culture methods= Urinary antigen / PCR (sputum)/ Serology

Question 8

What’s the difference between Legionnaire’s Disease and Pontiac Fever

Answer 8

L: positive isolation, 2-14 day incubation, pneumonia, 5-80% mortality
P: negative isolation, 1-2 day incubation, flu without pneumonia, nearly 0% mortality

Question 9

Describe Helicobacter pylori

Answer 9

Gastric pathogen - associated with gastric and duodenalulcers, gastritis, andgastric cancer.
Urease converts urea into CO2 and ammonia

Question 10

How can Helicobacter pylori be cultured?

Answer 10

Culture: from biopsy, selective agar, microaerophilic + hydrogen
Columbia Blood Agar Medium

Question 11

How can Helicobacter pylori be detected?

Answer 11

Non-invasive methods:= Urea Breath Test / Stool Helicobacter antigen test/ Serology

Question 12

What sites do anaerobes usually colonise?

Answer 12

Predominant sites colonised by Bacteroides and other anaerobic bacilli (mouth, gut), oral and dental, pleuropulmonary, intra-abdominal, female genital tract and skin, soft tissue and bone infections

Question 13

Name anaerobe examples

Answer 13

Bacteroides fragilis

Fusobacterium necrophorum

Question 14

Describe Bacteroides fragilis

Answer 14

Associated with intra-abdominal and skin and soft tissue infections below the waist
High level penicillin resistance (β- lactamase production)

Question 15

Describe Fusobacterium necrophorum

Answer 15

Long filamentous rods
Sore throat, peritonsillar abscess
Lemierre’s syndrome: infectiousthrombophlebitis of theinternal jugular vein

Question 16

Describe non-culturable bacteria

Answer 16

Lack of cell wall
Limited metabolic activity
Replicate intracellularly 
Resistance to many antibiotics
Cannot be cultured by standard methods

Question 17

Name types of non-culturable bacteria

Answer 17

Mycoplasma pneumoniae

Chlamydia trachomatis

Question 18

Describe Mycoplasma pneumoniae

Answer 18

Tracheobronchilotis, pneumonia
Children/young adults – closed populations
‘Walking’ pneumonia - (CXR more extensive than clinical presentation)

Question 19

What are other extra-pulmonary manifestations of Mycoplasma pneumoniae?

Answer 19

Cold agglutinins (haemolytic anaemia)
Skin involvement (rash, erythema multiforme)
Cervical lymphadenopathy
Neurological

Question 20

How can Mycoplasma pneumoniae by diagnosed?

Answer 20

Molecular (PCR respiratory sample)

Serology

Question 21

How can Chlamydia trachomatis be diagnosed?

Answer 21

Intracellular pathogen

PCR (e.g. urethral swab, cervical/vaginal swab)

Question 22

What are the clinical manifestations of Chlamydia trachomatis

Answer 22

Trachoma (serotypes A, B, Ba, and C)
STI (serotypes D through K)
urethritis, cervicitis, salpingitis, pelvic inflammatory disease, epididymitis , proctitis,
Lymphogranuloma venereum (LGV) (serotypes L1, L2, L3)
– tropics

Question 23

In what ways can Pneumonia be atypical?

Answer 23

Atypical in presentation - generalised symptoms – fever, myalgia
Atypical imaging – non-lobular, patchy inflammatory changes, pulmonary interistituim
Atypical in diagnosis – fastidious, non-culturable (use of PCR, serology etc)

Question 24

What bacteria are associated with atypical Pneumonia?

Answer 24

Mycoplasma pneumonia
Legionella pneumophila
Chlamydophila pneumoniae
Chlamydophila psittaci
Coxiella burnetii

Question 25

What are acid-fast bacilli?

Answer 25

resistant to decolourisation with acidified organic solvents (acid alcohol)
Thick, waxy cell wall (containing mycolic acid)

Question 26

Describe Mycobacterium tuberculosis

Answer 26

Slow growth rate in culture (average 4 wks, up to 8 wks)
1.8 million deaths a year
Primarily disease of lung, may spread to other sites e.g. miliary TB
High risk groups - high-incidence countries, immunocompromised, substance misuse
Multidrug resistance and drug tolerance