Infection microorganisms

Question 1

1. what gram stain is nisseria meningitidis?
2. what illness does nisseria meningitidis cause?
3. where is nisseria meningitidis commensal?
4. what is the virulence factors of nisseria meningitidis?
5. how would you identify nisseria meningitidis?
6. how is nisseria meningitidis treated?

Answer 1

1. gram negative diplococci
2. meningococcal sepsis
3. nasopharynx
4. lipopolysaccharide - triggers inflammation
5. nasopharyngeal swab
6. ceftriaxone (in sepsis) or beta lactams e.g. penicillin V - inhibits cell wall synthesis

Question 2

1. what gram stain is E.coli?
2. what illness does E.coli cause?
3. where is E.coli commensal?
4. how is E.coli treated?

Answer 2

1. gram negative bacilli
2. UTIs, peritonitis, neonatal meningitis
3. colon
4. trimethoprim for UTI - inhibits folic acid synthesis

Question 3

1. what gram stain is staph aureus?
2. what illness does staph aureus cause?
3. what is MRSA?
4. where is staph aureus commensal?
5. how is staph aureus treated?

Answer 3

1. gram positive cocci
2. skin abscess
3. a type of staph aureus that is resistant to lots of antibiotics
4. skin
5. flucloxacillin (if cellulitis) or vancomycin - both cell wall inhibitors

Question 4

1. what gram stain is staph epidermidis?
2. what does staph epidermidis form?
3. where is staph epidermidis commensal?
4. how is staph epidermidis treated?

Answer 4

1. gram positive cocci
2. a slime which is difficult to remove
3. skin
4. remove prosthetic device + use flucloxacillin

Question 5

1. what gram stain is strep pyogenes?
2. what are the virulence factors of strep pyogenes?
3. what does strep pyogenes cause?
4. how is strep pyogenes treated?

Answer 5

1. gram positive cocci
2. hyaluronic acid capsule, M protein hijakcs respiratory burst mechanism of neutrophils, streptokinase breaks down blood clots
3. bacterial pharyngitis + tonsilitis
4. penicillin V

Question 6

1. what gram stain is C.difficile?
2. what does sporulating mean?
3. where is C.difficle commensal?
4. what virulence factors does C.difficile have?
5. how is C.difficle treated?

Answer 6

1. gram positive bacilli
2. very difficult to get rid off - stays on surfaces
3. colon
4. toxin A (enterotoxin) - causes inflammation and buildup of excess fluid in bowel causing diarrhoea + toxin B (cytotoxin) - disrupts protein synthesis and disrupts cytoskeleton
5. metronidazole or vancomycin (serious cases)

Question 7

1. what is the gram stain of strep pneumoniae?
2. what is strep pneumoniaes main virulence factor?
3. how is mild peumonia treated?
4. how is moderate pneumonia treated?
5. how is severe pneumonia treated?

Answer 7

1. gram positive cocci
2. polysaccharide capsule
3. amoxicillin
4. amoxicillin + doxycycline
5. doxycycline + co-amoxiclav (all are cell wall synthesis inhibitors)

Question 8

1. what is the gram stain of viridans streptococci?
2. what illness is associated with viridans streptococci?
3. how is viridans streptococci treated?

Answer 8

1. GROUPS of gram positive cocci in chains
2. tooth decay and bacterial endocarditis
3. Penicillin V or surgical antibiotic prophylaxis

Question 9

1. what gram stain is haemophilus influenzae?
2. what illness is associated with haemophilius influenzae?
3. where is haemophilius influenzae commensal?
4. how is haemophilius influenza treated?

Answer 9

1. gram negative coccobacilli
2. mostly associated with children + especially pneumonia
3. nasopharyngeal
4. Co-amoxiclav and doxycycline

Question 10

1. what gram stain is salmonella typhi?
2. what illness does salmonella typhi cause?
3. how is salmonella typhi treated?

Answer 10

1. gram negative bacilli with flagella
2. causative agent of typhoid or enteric fever (travel related infection)
3. ceftriaxone (or fluoroquinolones)

Question 11

1. what gram stain is legionella pneumophilia?
2. what illness does legionella pneumophilia cause?
3. how is legionella pneumophilia spread?
4. how is legionella pneiomophilia treated?

Answer 11

1. gram negative bacilli
2. legionnaire’s disease or legionellosis or acute lobar pneumonia
3. air droplet
4. clarythromycin

Question 12

1. how does EBV appear under staining?
2. how does EBV cause infection?
3. how is EBV diagnosed?
4. what complications are associated with EBV?
5. how is EBV treated?

Answer 12

1. atypical lymphocyte
2. dsDNA, enveloped virus, infects B cells, results in T cell proliferation - splenomegaly
3. PCR, EBV serology, FBC, increased CD8 count
4. hodgkins lymphoma, gastric lymphoma, burkits lymphoma, nasopharyngeal carcinoma, sore throat
5. supportive treatment acyclovir

Question 13

1. what tyoe of virus is varicella zoster?
2. what does varicella zoster cause?
3. how does varicella zoster present?
4. who does varicella zoster affect?
5. what is the treatment for varicella zoster?

Answer 13

1. enveloped DNA virus, latent infection in dorsal root ganglia
2. chickenpox or reappears as shingles on a single dermatome
3. vesicular rash
4. immunocompromised or young
5. acyclovir - viral replication inhibitor

Question 14

1. what type of virus is Hep B?
2. what symptoms does Hep B cause?
3. what investigations can be done to confirm Hep B?
4. how is Hep B treated?

Answer 14

1. double stranded DNA, enveloped, blood bourne
2. fatigue, loss of apetite, abdominal pain, nausea, JAUNDICE
3. ALT, ALP and bilirubin all raised, PCR for Hep B
4. supportive treatment, if the disease progresses past 6 months then there is no cure, lifelong antivirals given, HbsAb vaccine

Question 15

1. what type of virus is Hep C?
2. how is at risk of developing Hep C?
3. what symptoms are associated with Hep C?
4. how would you investigate for Hep C?
5. what is the treatment for Hep C?

Answer 15

1. blood bourne virus, associated with hepatocellular carcinoma
2. IV drug users
3. mostly asymptomatic, 80% chronically infected which causes end stage liver disease, jaundice, cirrhosis
4. serology - anti HepC Ab + PCR
5. ribovarin + interferon (treatment for 8-12 weeks), can get re-infected, no vaccine, leads to chronic inflammation + infection of hepatocyte

Question 16

1. what type of virus is HIV?
2. what is meant by the term opportunistic illness?
3. how to investigate for HIV?
4. how is HIV treated?

Answer 16

1. ssRNA, enveloped retrovirus
2. HIV is more common in those who are immunocompromised + can result in reactivation of latent infections
3. viral load is inversely proportional to CD4 T cell count, T cell <200 = aids
4. HAART 2 nuceloside reverse transcriptase inhibitors + 1 non-nucleoside reverse transcriptase inhibitor OR 1 integrase inhibitor

Question 17

1. what type of virus is adenovirus?
2. where does adenovirus replicate?
3. what are symptoms of adenovirus?
4. what is the treatment for adenovirus?

Answer 17

1. double stranded DNA, non-enveloped
2. replicated in endothelial cells
3. conjunctivitis, sore throat, fever, cough
4. supportive treatment

Question 18

1. what type of virus is norovirus?
2. how is norovirus spread?
3. how is norovirus investigated?
4. how is norovirus treated?

Answer 18

1. single stranded RNA, non-enveloped, winter bug (associated with closed environment)
2. faecal - oral route
3. ELISA, stool sample
4. supportive treatment (anti-pyretics, IV fluid)

Question 19

1. what is the vector for plasmodium falciparum?
2. what are the consequences of plasmodium falciparum?
3. who is at risk of being infected by plasmodium falciparum?
4. how would you investigate for plasmodium falciparum?
5. how is plasmodium falciparum treated?

Answer 19

1. female mosquito as vector
2. hepatomegaly + splenomegaly - RBC destruction, increased bilirubin = jaundice
3. travelled to tropical regions
4. blood film x3, LFTs
5. quinine doxycycline

Question 20

1. where is candida albicans commensal?
2. what is the treatment for candida albicans?

Answer 20

1. vagina + mouth
2. nystatin, clotrimazole, IV fluconazole + systemic: amphotericin B

Question 21

1. what illness does aspergillous cause?
2. what is the treatment of aspergillous?

Answer 21

1. acute infection of the lungs
2. amphotericin B, targets chitin in fungal cell wall