Fastidious and Anaerobes Flashcards
What does fastidious mean?
difficult to grow in the laboratory
Needs enriched agar plates/CO2 enriched atmosphere
Non-culture methods for identification
Name examples of fastidious gram-negative bacilli
Haemophilus influenzae (facultative anaerobe) Legionella pneumophila (aerobe) Helicobacter pylori (microaerophilic)
Describe Haemophilus influenzae
Can colonise upper airway
Capsulated strains are associated with meningitis in children
Vaccine - H. influenzae with the type “b” capsule (Hib)
What are the clinical syndromes of Haemophilus influenzae?
Pneumonia
Meningitis
Otitis media
How can Haemophilus influenzae be cultured?
Growth at ~5% CO2
Chocolate agar plate (heat-lysed horse blood)
Absolute requirement for NAD (factor V) and a source of haem (factor X).
Describe Legionella pneumophila
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
How can Legionella pneumophila be cultured?
Optimum growth 25-42OC
Culture: selective agar (L-cysteine for growth) BCYE agar
Non-culture methods= Urinary antigen / PCR (sputum)/ Serology
What’s the difference between Legionnaire’s Disease and Pontiac Fever
L: positive isolation, 2-14 day incubation, pneumonia, 5-80% mortality
P: negative isolation, 1-2 day incubation, flu without pneumonia, nearly 0% mortality
Describe Helicobacter pylori
Gastric pathogen - associated with gastric and duodenalulcers, gastritis, andgastric cancer.
Urease converts urea into CO2 and ammonia
How can Helicobacter pylori be cultured?
Culture: from biopsy, selective agar, microaerophilic + hydrogen
Columbia Blood Agar Medium
How can Helicobacter pylori be detected?
Non-invasive methods:= Urea Breath Test / Stool Helicobacter antigen test/ Serology
What sites do anaerobes usually colonise?
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
Name anaerobe examples
Bacteroides fragilis
Fusobacterium necrophorum
Describe Bacteroides fragilis
Associated with intra-abdominal and skin and soft tissue infections below the waist
High level penicillin resistance (β- lactamase production)
Describe Fusobacterium necrophorum
Long filamentous rods
Sore throat, peritonsillar abscess
Lemierre’s syndrome: infectiousthrombophlebitis of theinternal jugular vein
Describe non-culturable bacteria
Lack of cell wall Limited metabolic activity Replicate intracellularly Resistance to many antibiotics Cannot be cultured by standard methods
Name types of non-culturable bacteria
Mycoplasma pneumoniae
Chlamydia trachomatis
Describe Mycoplasma pneumoniae
Tracheobronchilotis, pneumonia
Children/young adults – closed populations
‘Walking’ pneumonia - (CXR more extensive than clinical presentation)
What are other extra-pulmonary manifestations of Mycoplasma pneumoniae?
Cold agglutinins (haemolytic anaemia)
Skin involvement (rash, erythema multiforme)
Cervical lymphadenopathy
Neurological
How can Mycoplasma pneumoniae by diagnosed?
Molecular (PCR respiratory sample)
Serology
How can Chlamydia trachomatis be diagnosed?
Intracellular pathogen
PCR (e.g. urethral swab, cervical/vaginal swab)
What are the clinical manifestations of Chlamydia trachomatis
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
In what ways can Pneumonia be atypical?
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)
What bacteria are associated with atypical Pneumonia?
Mycoplasma pneumonia Legionella pneumophila Chlamydophila pneumoniae Chlamydophila psittaci Coxiella burnetii
What are acid-fast bacilli?
resistant to decolourisation with acidified organic solvents (acid alcohol)
Thick, waxy cell wall (containing mycolic acid)
Describe Mycobacterium tuberculosis
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
