Medical microbiology IA % +

Question 1

Lists the categories of micro-organism that cause infection.

Answer 1

• Bacteria
• Viruses
• Fungi
• Parasites
• Prions

Question 2

List the common sterile sites in the body

Answer 2

• Blood
• CSF(cerebro-spinal fluid)
• Lung
• Bladder

Question 3

List the non-sterile sites in the body

Answer 3

• Skin
• Nasopharynx
• Urethra (a tube that connects the urinary bladder to the urinary meatus for the removal of urine from the body.)
• Gut

Question 4

Outline the role of microscopy in bacterial infection.

Answer 4

• Light microscopy (x1000 magnification)
• Unstained - to see pus cells (e.g.urine, CSF)
• to see parasites (faeces)
• Gram stain - to see bacteria and yeasts/fungi
• Viruses not visible in light microscope

Question 5

Explain the difference between sterile and non sterile sites.

Answer 5

• Sterile sites should contain no micro-organisms
• Non-sterile sites may contain commensal microbes that may not harm the body, but still show up in microscopy or cultures.

Question 6

Outline the methods of detecting viruses

Answer 6

• Molecular methods-real time PCR
• Antigen detection
• Serology to determine immunity (antibodies in serum)
• Used rarely: Electron microscopy/ Cell or tissue culture - inoculate a “cell line”

Question 7

Outline the diagnostic principles in parasitology

Answer 7

• Microscopy of different stages: parasites, cysts and ova in faeces.
• Blood films for malaria
• Culture rarely possible
• Serology sometimes useful

Question 8

Describe basic infection control measures

Answer 8

• Wash hands before touching patient
• Wash hands or apply alcohol gel between patients
• Swab stethoscope between patients
• Patients isolated in single room (“barrier nursed” or source isolation) have extra precautions:

1. Wash hands, wear plastic apron
2. On leaving, dispose of apron, wash hands

Question 9

List the common specimen types collected for culture.

Answer 9

• Urinary tract infection - mid-stream urine (MSU)
• Chest infection – sputum
• Tonsillitis/pharyngitis – throat swab
• Wound or site of infection - swab or pus (swabs are sent in bacterial transport medium)
• Diarrhoea - faeces
• Bacteraemia - blood culture
• Meningitis - cerebro-spinal fluid (CSF)

Question 10

Feutures of gram stain & Microscopy

Answer 10

• Rapid
• Not sensitive
• Can’t usually identify particular species

Question 11

Features of cell culture

Answer 11

• Slow
• Sensitive
• Culture conditions suitable for the expected species

Question 12

4 Healthcare Acquired Infection

Answer 12

1. Methicillin Resistant Staph aureus (MRSA)
2. Clostridium difficile
3. Organisms with Extended Spectrum β-lactamases (ESBLs)
4. Noroviruses