Gram Negative Bacilli (Rods)

Question 1

Neisseria species

Answer 1

Gram negative cocci, often arranged in diplococci with tapered ends

oxidase positive

Aerobic

Most catalase positive

Question 2

Neisseria gonorrhoea

Answer 2

STI

G- diplococci

Fastidious, capnophilic and susceptible to cool temperatures drying and fatty acids

produce acid from glucose only

Question 3

Neisseria meningitidis

Answer 3

Encapsulated small G- diplococci

Second most common cause of community acquired meningitis in healthy adults

Question 4

Pathogenicity of Neisseria meningitidis

Answer 4

Receptor specific colonisation of nociliated cells of nasopharynx

anti-phagocytic capsule allows systemic spread

hyperproduction of lipooligosaccharide

Question 5

Meningococcal disease pathophysiology

Answer 5

specific receptors (GD1 ganlioside) for bacterial fimbriae on nonciliated columnar epithelial cells in nasopharynx of host

Internalised into phagocytic vacuoles and resist intracellular killing

replicate intracellularly and migrate to subepithelial space

Hyperproduction of endotoxin (lipid A & LOS) and blebbing into surrounding environment

Question 6

Helicobacter Pylori

Answer 6

associated with gastric antral epithelium in pateints with active chronic gastritis

Urease, Mucinase and Catalase positive

Question 7

Vibrio species

Answer 7

Vibrio species (including cholera) grow in estuarine and marine environments

survive and replicate in comtaminated waters with increased salinity and at temps of between 10-30 C

Symbiotic associations with chitinous shellfish - reserviour

Question 8

Psuedomonas and nonfermenters

Answer 8

Opportunistic pathogens of Plants, Animals and Humans

Many taxonomic changes in last decade

Question 9

Pseudomonas aeruginosa

Answer 9

simple nutritional requirements

slime layer colonise respiratory tract skin - burn, wound infections

Question 10

Stenotrophomonas maltophilia

Answer 10

Hospital Epidemics from Contaminated Moist reservoirs

Question 11

Acinetobacter baumanii Infections:

Answer 11

Respiratory tract

Urinary tract

Wounds

Septicemia

Question 12

Acinetobacter baumanii niches

Answer 12

• Natural environments
• Moist surfaces in hospitals (e.g., respiratory therapy equipment)
• Dry surfaces (e.g., human skin); rare for gram-negative bacilli
• Occasionally normal flora in oropharynx

Question 13

Acinetobacter baumanii treatment

Answer 13

Antibiotic Resistance Common

Empirical Treatment for Acute Infections: β-lactam + Aminoglycoside Specific Therapy According to Antibiotic Susceptibility

Question 14

Moraxella catarrhalis

Answer 14

In Elderly Patients with Chronic Pulmonary Disease

• Bronchitis
• Bronchopneumonia In Previously Healthy People
• Sinusitis
• Otitis Most strains produce β-lactamase; Penicillin Resistant

Question 15

Haemophilis

Answer 15

G- bacilli, likes blood

Obligate parasites

• Haemophilus influenzae

Acute pyogenic, normally invasive infections Chronic infections with H. influenzae as 2o pathogen

• Haemophilus ducreyi

True pathogen (i.e., not found in healthy individuals) STD; Soft chancre (chancroid)

Question 16

pasteurella disease forms

Answer 16

Localized cellulitis and lymphadenitis following animal bite or scratch In patients with underlying lung dysfunction,

worsening of chronic pulmonary disease from aspiration of organisms colonizing patient’s oropharynx

Systemic infection in immunocompromised

Liver disease patients at highest risk

Question 17

Bordetella, Francisella & Brucella

Answer 17

Extremely small Aerobic nonfermenters

Gram-negative coccobacilli

True pathogens: isolation always associated with disease; i.e., always clinically significant

NOTE: Previously studied nonfermenters were all opportunistic pathogens

Question 18

Human Disease & Associated Pathogens

Answer 18

Question 19

What is the disease severity of Brucella melitenisis?

Answer 19

Severe acute disease

Question 20

What is the disease severity of Brucella abortus?

Answer 20

Mild Disease

Question 21

What is the disease severity of Brucella suis?

Answer 21

Severe Chronic

Question 22

What is the disease severity of Brucella canis?

Answer 22

Mild disease

Question 23

Clinical Presentation of
Human Brucellosis

Answer 23

Acute disease often develops with initial nonspecific symptoms of malaise, chills, fatigue, weakness, myalgias (muscles), weight loss, arthralgias (joint), and nonproductive cough

Mild disease with rare suppurative complications

Chronic disease and recurrence are common because it can survive in phagocytic cells and multiply to high concentrations

May also take the form of destructive lesions

Question 24

Legionella pneumophilia

Answer 24

• Rod-shaped, gramnegative aerobic bacterium.
• 0.3 – 0.9 μm in width and 2 – 3 μm in length.
• Motility via one or more flagella.
• Lipid vacuoles present.

Question 25

What is Legionellosis?

Answer 25

• An infection caused by the bacterium,
Legionella pneumophila.

• The disease has two distinct forms:
Legionnaires’ Disease
»Severe form of infection, includes
pneumonia
Pontiac Fever
» Milder illness, resembles influenza

Question 26

Ecology of Legionella pneumophilia

Answer 26

• There are 40 species in the family of Legionella bacteria in the world. Of these species, 90% of diseases have been caused by Legionella pneumophila.
• There are 15 serogroups of L. pneumophila and most cases are associated with serogroup 1. There are 5 subgroups in this serogroup which have different
degrees of virulence.

Legionella are usually found in the freshwater of streams, lakes, warm springs, rivers, and riverbanks.
• Environmental conditions which promote
the growth of Legionella are:
• Water temperature between 20 – 50 ºC
• Stagnant water
• pH range of 2.0 – 8.5
• Sediment in water which supports the
growth of supporting microbiota (e.g. algae,
protozoa and others)
• Iron salts promote growth

Question 27

Pathogenesis of Legionella

Answer 27

Legionnaires’ Disease is caused by inhaling L.
pneumophila bacteria dispersed in aerosols of
contaminated water from the environment

• L. pneumophila enters a human host by
penetrating deep into the lungs; the size of the
bacterium allows its entrance in the human
respiratory tract.
• White blood cells attempt to ingest the bacterium
but instead of being destroyed, Legionella grow
and replicate, eventually killing the cell. More
Legionella are released into the lungs & worsen
the infection.
• Legionnaires’ Disease develops 2 – 10 days after
exposure to the bacteria. Exposure doesn’t
necessarily lead to infection. About 5 – 10% of the
population show serologic evidence of exposure,
but never develop symptoms of an infection.