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Infection > Classification and investigation of microbes > Flashcards

Classification and investigation of microbes Flashcards

1
Q

What 4 large groups of microbes are there?

A
  • viruses
  • bacteria
  • fungi (yeasts and moulds)
  • parasites (protozoa and helmithins/ worms)
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2
Q

How can DNA based viruses be classified?

A

if double stranded or single stranded DNA and then if they have an envelope (phospholipid bilayer)

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3
Q

How can RNA based viruses be classified?

A

First by double or single stranded RNA, if single stranded if it can be read (positive) or needs reverse transcription (negative), then by if icosahedral or helical RNA and then by if virus enveloped or non enveloped

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4
Q

What are kochs prostulates for proving a microorganism is the cause of a disease?

A
  • microorganism should be found in abundance in all organisms with disease and not in healthy organisms
  • microorgansim must be able to be siolated and grown in culture
  • cultured microorganism must cause disease in healthy organism when introduced
  • microorganism must be reisolated and identified as identical to originally introduced microorgansim
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5
Q

Whats a bacteriophage?

A

A virus that infects bacteria

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6
Q

What shapes can bacteria be classified into?

A
  • circles (coccus/ cocci) can be in clusters (eg. staphylocuccus) or chains (streptococcus)
  • lines (spirillus)
  • rods (bacillus)
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7
Q

What does a gram stain test for? How is it done?

A

Add crystal violet, wash, add iodine, wash with alcohol and then add safranin. If the bacteria has a lots of polysaccaride on the capsule it will retain the safarnin stain.

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8
Q

What colour do gram + and gram - bacteria go on gram stain?

A

purple is gram + and red is gram -

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9
Q

When is an acid fast stain most commonly done?

A

When mycobacterium such as TB are suspected

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10
Q

What is a chocolate agar?

A

An agar that is fortified by blood and then heated to lyse the RBCs. This means that some specific bacteria will grow better.

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11
Q

What is the differance between an anaerobe and an obligate anaerobe?

A

Anaerobe can survive without O2 and obligate anaerobe cannot survive when O2 is present

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12
Q

What 3 ways can viruses be detected?

A

Antigen detection (ELISA test)
Antibody detection
DNA/ RNA detection - PCR

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13
Q

What 3 investigations can be useful to detect and identify a bacteria?

A

Blood cultures
PCR
Antigen detection
Sometimes toxin detection

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14
Q

If neutrophils and WBC count was high what type of infection is suggested?

A

Bacterial

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15
Q

If lymphocytes and WBCs are high what type of infection is suggested?

A

Viral

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16
Q

If WBC count and/ or neutrophils and/ or lymphocytes are low or normal is there defiantly no infection?

A

No

17
Q

What commensals are found on skin? Group into gram+ and -

A 
gram +: 
- staph aureus and staph epididermis and many streptococcus species
Gram-:
- corynebacterium 
- prioprionibacterium
18
Q

Outline the infection model

A

Pathogen and Pt interact and if conditions are right the mechanism of infection leads to infection. This leads to management (investigations, history, treatment) which leads to outcome (resolution, death, long term infections ect)

19
Q

What factors about pt may change likleyhood of infection

A
  • age (v. Old or v. Young)
  • gender (UTI more common in females)
  • physiology (pregnant, behaviours (STDs and EBV)
  • social factors
  • pathology (diabetes)
  • Place (where they are and have been)
  • time (of year- winter, and relative to infection timeline )
20
Q

Give 4 mechanisms of infection?

A
  • contiguous spread (direct contact)
  • inoculation (needles)
  • haematogenous (by blood)
  • ingestion
  • inhalation
  • migration of commensals
  • vector
  • vertical
21
Q

What needs to happen for infection to cause disease?

A
  • attachment to tissues
    Then, either:
  • interaction with host defences leading to inflammation and so host damage
    Or
  • toxin production leading to host damage
22
Q

What are 6 steps to management of an infection?

A
  • History
  • Examination
  • investigations
  • Diagnosis
  • Treatment
  • Infection prevention
23
Q

What questions would you ask in history if infection suspected?

A
  • about place: Where you live, where you been, anyone at work/ family had illness?
  • about time: How long symptoms present for, have they changed, how long since abroad
  • about symptoms: local (signs of inflammation, sore throat, cough, GI upset, ear pain, pain on urination, vomiting ect) and systemic (fever, weakness, consciousness, chills and rigour)
  • about pt (smoke, diabetes, splenectomy, antibiotics ect)
24
Q

What examinations would be done if infection suspected?

A

HR, BP, Temp, spleen and liver size, o2 saturation,

25
Q

What investigations could be ordered if infections suspected?

A
  • X-ray
  • FBC- look at Hb, MCV, WBCs, neutrophils and lymphocytes
  • U&E - test kidney function
  • CRP- marks inflammation
  • coagulation studies (is liver ok- clotting often changes)
  • liver function (AST and ALT)
  • blood sugar and gasses
  • PCR
  • Blood cultures
  • general microbio tests like swabs, samples ect to test
26
Q

How can infections be treated?

A 
Supportively:
- pain relief, fluids, basically just restore physiological state (leave temp)
Specific:
- antibiotics/ antivirals/ antifungals 
- drainage 
- debridement/ dead space removal
27
Q

What is sepsis?

A

‘life threatening organ dysfunction due to dysregulated host response to an infection’ When the hosts immune response becomes exaggerated, leading to uncontrolled cytokines release. This leads to vascular dilation (decreases BP–> shock), coagulation changes–> more thrombus–> organ ischaemia and failure

28
Q

What are general signs of sepsis?

A
  • look very unwell
  • fever
  • headache
  • unresponsiveness
  • weakness
  • photophobia
  • high HR
  • low BP
  • nausia
  • abdopain and vomiting
  • other signs suggest scource (eg beach stiffness with meningitis)
29
Q

What are red flags for sepsis?

A
  • high resp rate over 25 per min
  • need for O2 to keep sats abover 91%
  • low BP (<91 or fall of 40 from normal)
  • no urine output for 18hrs
  • Hr > 130
  • unresponsive execpt to voice or pain or neither
  • non blanching rash, ashen, cyanosis, neutropenia or chemo in last 6 weeks
30
Q

What are 6 steps to sepsis treatment?

A
  • give high flow o2
  • take blood cultures
  • Give antibiotics
  • Give fluids
  • Measure lactate
  • measure urine output and balance fluids, consider catheter
31
Q

What complications are there to sepsis ?

A
  • irreversible hypotension
  • resp failure
  • renal failure
  • increased intercranial pressure
  • ischamic necrosis of extremities
32
Q

staph epididermis and aureus are both gram + cocci that tend to live in grape bunch like clusters, how can you differentiate between them?

A
  • epididermis is coagulase negative

- areus is coagulase positive

33
Q

Where would you get a sample from to test for MRSA?

A

nose swab

Infection (9 decks)

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