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Microbiology CBL Flashcards

(65 cards)

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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
Mx of px with diarrhoea
Fluids if urea raised (oral or IV) | Antibiotics have little use in GE and can worsen prognosis - only give if CDI
26
Which viruses cause a vesicular rash?
Herpes simplex virus 1/2 Varicella zoster virus (chicken pox) Enterovirus (hand foot and mouth disease)
27
Proving immunity to varicella?
Varicella zoster virus IgG
28
Immunocompromised px at risk of complications of varicella. Including...
Bacterial infection of skin and soft tissues Disseminated varicella Haemorrhagic varicela VZV pneumonitis
29
Varicella zoster prophylaxis
Varicella zoster immunoglobulin - prepared from pooled plasma of non-UK donors with high titres of VZ antibody
30
Treatment of varicella-zoster if prophylaxis in unsuccessful
Aciclovir IV or valaciclovir oral if px is well enough
31
Aciclovir MOA
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
Aciclovir and renal function?
IV aciclovir may cause nephrotoxicity due to aciclovir crystals.
33
Which px groups are most likely to present with pulmonary TB?
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
What investigations should be done for suspected TB?
Sputum - TB bacilli by special stains CT of chest do differentiate between bronchial neoplasm and TB Bronchoscopy if still doubt Pleural effusion tap
35
4 drug therapy for TB
Rifampicin (colours urine red) Isoniazid (BOTH 6 MONTHS) Pyrazinamide Ethambutol
36
Isoniazid risk factors
Peripheral neuropathy due to antagonism of pyridoxine (Vit B6) - prophylactic measures of pyridoxine tx needed
37
Complications of TB
Nodal TB Osteomyelitis CNS TB - TB meningitis, cerebral TB Renal, testes, larynx, skin, liver, eye complications
38
Severe sepsis
Sepsis with organ dysfunction, hypoperfusion or hypotension
39
Septic shock
Sepsis with refractory hypotension
40
How is HIV transmitted?
``` 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
High risk groups for HIV
``` MSM who have unprotected sex High prevalence countries South east asia, eastern europe, south/central america IVDU Anyone diagnosed with an STI ```
42
Barriers to HIV testing
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
What is PCR?
Polymerase chain reaction - amplifies specific DNA sequence generating multiple copies. Sensitive and specific for diagnosing viruses
44
What is P. jiroveci (PCP)?
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
Define 'opportunistic infection'
Organisms which do not usually cause infection but do so when a hosts defences are compromised e.g. candida
46
Virology tests used to dx HIV
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
What is an HIV viral load?
Measure of HIV RNA in plasma. It is high in acute infection or late untreated disease.
48
How does HIV affect the immune system?
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
Criteria for diagnosis of AIDS? (Advanced HIV)
Aids defining illness evidence e.g. - ``` Recurrent bacterial infections (pneumonia) Cervical cancer Lymphoma Dementia Wasting syndrome ```
50
HAART
3 active drugs against HIV - 2 nucleoside reverse transcriptase inhibitors and either 1 non nucleoside reverse transcriptase inhibitor or 1 protease inhibitor.
51
Which clinical signs predict bacterial meningitis (BM) in 95% of px?
Headache Neck stiffness Confusion Fever
52
Main causative organisms in BM?
Streptococcus pneumonaie Neisseria meningitidis Listeria Streptococcus spp.
53
Investigations and Tx for BM?
Airway, breathing, circulation Pre-hospital parenteral penicillin or chloramphenicol Blood cultures Lumbar puncture
54
What is neutrophil pleocystosis in CSF with elevated protein and glucose <50% of blood characteristic of?
Bacterial rather than viral meningitis
55
Prophylaxis for meningococcal infection?
Ciprofloxacin (adults and children) or ceftriaxone (pregnancy) Audiometry performed as hearing loss
56
Antibiotic tx of bacterial meningitis?
3rd generation cephalosporins (3GC) and vancomycin +/- rifampacin Dexamethasone 10mg 6 hourly
57
Fever and recent travel to tropical country?
Malaria suspected
58
Important infections considered in all returning travellers with fever?
malaria, dengue, enteric fever (typhoid), HIV seroconversion
59
Falciparum Malaria dx?
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
Initial investigations for febrile travellers?
``` FBC LFTs U+E's Blood cultures HIV test Urine, stool culture CXR Ultrasound liver and spleen ```
61
Tx for falciparum malaira?
1 week quinine + doxycycline evidence of artemisinin drugs being superior to quinine but not widely available in the UK
62
Four species of plasmodia responsible for human malaria?
P. ovale, P. Falciparum, P. vivax, P. malariae
63
Complications of malaria?
``` Impaired consciousness Hypoglycaemia Spontaneous bleeding Haemoglobinuria Renal impairment Acidosis Pulmonary oedema Shock Death ```
64
Which antibiotics is Klebsiella pneumoniae resistant to?
Cefpoxodamin, ceftazidime, ampicillan, gentamicin
65
Resistance to cephalosporins?
Major concern. B-lactamases produced which are enzymes that hydrolyse the B-lactam ring of penicillin and cephalosporin antibiotics.

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