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CBL > Microbiology CBL > Flashcards

Microbiology CBL Flashcards

1
Q

How should blood cultures be taken when dealing with possible bacterial endocarditis (BE)?

A

3 sets
From peripheral veins
Prior to antibiotics

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2
Q

Fever and a heart murmur?

A

Bacterial endocarditis should always be considered

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3
Q

Investigations for endocarditis?

A

Echocardiogram

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4
Q

What will be seen on an echocardiogram in BE?

A

Fibrin and platelets attached to damaged heart valve

Bacteria adherence to lesions = vegetations

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5
Q

Gram positive cocci

A

Staphylococci (clusters like grapes)

Streptococci (chains)

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6
Q

Gram positive rods

A

Clostridia (c. diff)
Bacillus (B.cereus)
Listeria (L.monocytogenes)

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7
Q

Gram negative cocci

A

Neisseriae

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8
Q

Gram negative rods

A

E.coli

Klebsiella (K.pneumoniae)

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9
Q

Most common streptococcus species associated with BE?

A

Streptococcus viridans

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10
Q

Criteria used to diagnose endocarditis

A

Dukes criteria - sustained bacteraemia with a typical organism and an echo which is consistent with endocarditis

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11
Q

Streptococcal endocarditis antibiotic regimen

A

4 weeks benzylpenicillin with gentamicin the first two weeks (synergistic in combination but gentamicin alone would not work)

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12
Q

Acute cholecystitis pathogenesis

A 
Gallbladder infections usually result from gallstone formation and impaction in cystic duct leads to -
Infection
Oedema
Cholangitis
Liver abcess formation
Gangrene of gallbladder
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13
Q

Criteria for systemic inflammatory response syndrome (SIRS)

A

Temp >38 or <36
Tachycardia >90bpm
Tachypnoea RR>20/min
WBC >12

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14
Q

Necrotising fascitis causing severe sepsis clues

A

NSAID use
Mild preceeding trauma
Sepsis
Progresses over several hours

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15
Q

Type 1 vs Type 2 necrotising fascitits

A

Type 1 - Anaerobe infection (bacteroides) and aerobes (Streptococci). More common in elderly px.

Type 2 - Group A streptococci (S. pyogenes or S. aures)

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16
Q

Broad spectrum antibiotics to commence in NF

A 
flucloxacillan
benzylpenicillin
metronidazole
gentamicin
clindamycin
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17
Q

Surgical prophylaxis for MRSA

A

Vancomycin or teicoplanin (glycopeptide)

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18
Q

Cefuroxime

A

Associated with c.diff

No activity against MRSA

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19
Q

What to establish in a sexual hx?

A 
Date of last sex
Gender of partner
Type of sex - oral, anal etc
Condom?
Have they had an STI test before?
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20
Q

HIV symptom screen

A

Fever, rash, headache, sore throat, swollen glands

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21
Q

Investigations for MSM

A

Genital, anal and proctoscopic exam
Excluse mouth for oral hairy leukoplakia and candida
Lymph nodes, skin rash?
NAAT for chlamydia and gonorrhoea

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22
Q

Why does n.gonorrhoea have multiple drug resistance determinants?

A

It is naturally transformable and can easily acquire plasmids and genetic material between resistant and sensitive organisms can be transferred.

Resistant to penicillin, tetracycline and quinolone (ciprofloxacin)

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23
Q

Risk factors for CDI

A

Over 65
recent hospitalisation
recent antibiotics

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24
Q

Most common causes of gastroenteritis

A 
Campylobacter 
Salmonella
E.coli
Norovirus
Rotavirus
Giardiasis
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25
Q

Mx of px with diarrhoea

A

Fluids if urea raised (oral or IV)

Antibiotics have little use in GE and can worsen prognosis - only give if CDI

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26
Q

Which viruses cause a vesicular rash?

A

Herpes simplex virus 1/2
Varicella zoster virus (chicken pox)
Enterovirus (hand foot and mouth disease)

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27
Q

Proving immunity to varicella?

A

Varicella zoster virus IgG

28
Q

Immunocompromised px at risk of complications of varicella. Including…

A

Bacterial infection of skin and soft tissues
Disseminated varicella
Haemorrhagic varicela
VZV pneumonitis

29
Q

Varicella zoster prophylaxis

A

Varicella zoster immunoglobulin - prepared from pooled plasma of non-UK donors with high titres of VZ antibody

30
Q

Treatment of varicella-zoster if prophylaxis in unsuccessful

A

Aciclovir IV or valaciclovir oral if px is well enough

31
Q

Aciclovir MOA

A

Nucleic acid analogue. Converted by viral thymidine kinase to aciclovir monophosphate. Host cell kinases convert aciclovir monophosphate to aciclovir triphosphate.

Aciclovir triphosphate is the active form which acts as the nucleic acid analogue competitively inhibiting viral DNA polymerase - DNA chain termination

32
Q

Aciclovir and renal function?

A

IV aciclovir may cause nephrotoxicity due to aciclovir crystals.

33
Q

Which px groups are most likely to present with pulmonary TB?

A

People who acquired the infection in the 1940s or 1950s
Alcoholics
Those who grew up or visited the developing world for prolonged periods
Strong correlation with HIV

34
Q

What investigations should be done for suspected TB?

A

Sputum - TB bacilli by special stains
CT of chest do differentiate between bronchial neoplasm and TB
Bronchoscopy if still doubt
Pleural effusion tap

35
Q

4 drug therapy for TB

A

Rifampicin (colours urine red)
Isoniazid (BOTH 6 MONTHS)
Pyrazinamide
Ethambutol

36
Q

Isoniazid risk factors

A

Peripheral neuropathy due to antagonism of pyridoxine (Vit B6) - prophylactic measures of pyridoxine tx needed

37
Q

Complications of TB

A

Nodal TB
Osteomyelitis
CNS TB - TB meningitis, cerebral TB
Renal, testes, larynx, skin, liver, eye complications

38
Q

Severe sepsis

A

Sepsis with organ dysfunction, hypoperfusion or hypotension

39
Q

Septic shock

A

Sepsis with refractory hypotension

40
Q

How is HIV transmitted?

A 
Body fluids and/or tissues
Unprotected sexual intercourse - insertive vaginal, receptive  vaginal, insertive anal, receptive anal, oral
IV drug users
Blood transfusion
Tattoo/piercing
41
Q

High risk groups for HIV

A 
MSM who have unprotected sex
High prevalence countries
South east asia, eastern europe, south/central america
IVDU
Anyone diagnosed with an STI
42
Q

Barriers to HIV testing

A

Px barriers - might not think they are at risk, stigma, immigration issues, fit to work (e.g. doctor), insurance

Doctor barriers - may assume px isnt at risk, lack of urine, fear of offending px

43
Q

What is PCR?

A

Polymerase chain reaction - amplifies specific DNA sequence generating multiple copies. Sensitive and specific for diagnosing viruses

44
Q

What is P. jiroveci (PCP)?

A

Opportunistic infection caused by fungus in immunocompromised px. Funcus with cyst, merozoite and trophozoite morphology.
Extracellular pathogen causes interstitial plasma cell pneumonia
SOB, fever, dry cough

Tx - cotrimoxazole, steroids

45
Q

Define ‘opportunistic infection’

A

Organisms which do not usually cause infection but do so when a hosts defences are compromised e.g. candida

46
Q

Virology tests used to dx HIV

A

HIV antibody test - most px develop antibodies within 6-8wks

ELISA test performed first then confirmed with Western Blot

HIV p24 antigen testing more recently

47
Q

What is an HIV viral load?

A

Measure of HIV RNA in plasma. It is high in acute infection or late untreated disease.

48
Q

How does HIV affect the immune system?

A

HIV gains entry to T helper cells by binding to CD4 on their surface. T helper cells are depleted as HIV progresses, impairing B cell activation and antibody production.

49
Q

Criteria for diagnosis of AIDS? (Advanced HIV)

A

Aids defining illness evidence e.g. -

Recurrent bacterial infections (pneumonia)
Cervical cancer
Lymphoma
Dementia
Wasting syndrome
50
Q

HAART

A

3 active drugs against HIV -
2 nucleoside reverse transcriptase inhibitors and either 1 non nucleoside reverse transcriptase inhibitor or 1 protease inhibitor.

51
Q

Which clinical signs predict bacterial meningitis (BM) in 95% of px?

A

Headache
Neck stiffness
Confusion
Fever

52
Q

Main causative organisms in BM?

A

Streptococcus pneumonaie
Neisseria meningitidis
Listeria
Streptococcus spp.

53
Q

Investigations and Tx for BM?

A

Airway, breathing, circulation
Pre-hospital parenteral penicillin or chloramphenicol
Blood cultures
Lumbar puncture

54
Q

What is neutrophil pleocystosis in CSF with elevated protein and glucose <50% of blood characteristic of?

A

Bacterial rather than viral meningitis

55
Q

Prophylaxis for meningococcal infection?

A

Ciprofloxacin (adults and children) or ceftriaxone (pregnancy)

Audiometry performed as hearing loss

56
Q

Antibiotic tx of bacterial meningitis?

A

3rd generation cephalosporins (3GC) and vancomycin +/- rifampacin

Dexamethasone 10mg 6 hourly

57
Q

Fever and recent travel to tropical country?

A

Malaria suspected

58
Q

Important infections considered in all returning travellers with fever?

A

malaria, dengue, enteric fever (typhoid), HIV seroconversion

59
Q

Falciparum Malaria dx?

A

3 blood tests over 2-3 days, can be diagnosed by microscopy of a thick or thin blood film, or using a rapid diagnostic antigen test

60
Q

Initial investigations for febrile travellers?

A 
FBC
LFTs 
U+E's
Blood cultures
HIV test
Urine, stool culture
CXR 
Ultrasound liver and spleen
61
Q

Tx for falciparum malaira?

A

1 week quinine + doxycycline

evidence of artemisinin drugs being superior to quinine but not widely available in the UK

62
Q

Four species of plasmodia responsible for human malaria?

A

P. ovale, P. Falciparum, P. vivax, P. malariae

63
Q

Complications of malaria?

A 
Impaired consciousness
Hypoglycaemia
Spontaneous bleeding
Haemoglobinuria
Renal impairment
Acidosis
Pulmonary oedema
Shock
Death
64
Q

Which antibiotics is Klebsiella pneumoniae resistant to?

A

Cefpoxodamin, ceftazidime, ampicillan, gentamicin

65
Q

Resistance to cephalosporins?

A

Major concern. B-lactamases produced which are enzymes that hydrolyse the B-lactam ring of penicillin and cephalosporin antibiotics.

CBL (9 decks)

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