Bacteriology

Question 1

Mechanism for MRSA resistance

Answer 1

mec gene (mecA) which produces PBP2a. This has a low affinity for beta lactams.

Question 2

SCCmec type - hospital and community acquired

Answer 2

Type 1, 2 and 3 - hospital

Type 4 and 5 - community

Question 3

MRSA lab definition

Answer 3

Oxacillin MIC greater or equal to 4mcg/ml

Question 4

Catalase positive bacteria

Answer 4

Staphylococcus 
Pseudomonas aeroginosa
Aspagillus fumigatus 
Candida albicans
Enterobacteriaceae (Klebsiella, Serratia)
Mycobacterium tuberculosis

Question 5

What is the Panton-Valentine leukocidin?

Answer 5

A toxin produced by S. aureus which is cytolytic to PMNs, macrophages and monocytes

Question 6

Bacteria classed as Group A strep

Answer 6

S. pyrogenes

Question 7

Toxins involved in scarlet fever

Answer 7

Streptococcus pyrogenic exotoxins

Question 8

Mechanisms Group A Streptococcus uses to avoid phagocytosis

Answer 8

M protein

Polysaccharide capsule

Question 9

Pathogenesis of Scarlet Fever

Answer 9

Group A Streptoccocus infection releases the toxin sreptoccocal pyrogenic exotoxins. There is then a hypersensitivity reaction to the toxin leading to the rash

Question 10

VRE - what organism is it most associated with

Answer 10

E. faecium. E. faecalis resistance is significantly more rare

Question 11

Mechanism of VRE

Answer 11

Vancomycin resistance cluster genes coding for a changed binding terminus D-Ala-D-Ala to D-Ala-D-lactate

Question 12

Cause of tetanus including bacteriology

Answer 12

Clostridium tetani. An anaerobic, gram positive spore-forming rod. Disease is caused by exotoxin, transported via peripheral motor neurons to body, crosses to inhibitory interneuron, blocking its neurotransmission.

Question 13

Signs of tetanus

Answer 13

Local - muscle spasms and pain, trismus, difficulty swallowing
Generalised - muscle spasms, loss of airway and breathing, cardiovascular instability, fever, seating, GI stasis

Question 14

Immediate management of tetanus

Answer 14

• Clean wound + abx
• Human Tetanus immune globulin (including intrathecal)
• Support airway and breathing
• Control spasms with sedation, magnesium sulphate, paralytics

Question 15

What are the live vaccines?

Answer 15

MMR 
BCG 
Varicella 
Zoster 
Rotavirus 
Japanese encephalitis 
Oral typhoid 
Yellow fever

Question 16

What are the vaccines recommended routinely in the elderly?

Answer 16

Yearly influenza
Pneumococcal at 65
Herpes zoster at 70
Boostrix if in contact with children eg grandparents

Question 17

What are the gram positive cocci?

Answer 17

Staphylococci - coagulase pos (S. aureus) or neg (other)
Streptococci - alpha haemolytic (viridans, pneumococcus), beta haemolytic (groups A-G)
Enterococcus

Question 18

What type of bacteria are clostridia? What are the subtypes?

Answer 18

Gram pos anaerobic rods 
C. perfringens 
C. botulinum 
C. difficile 
C. tetani

Question 19

What type of bacteria are neisseria? What are the subtypes?

Answer 19

Gram neg cocci
N. meningitidis
N. gonorrhoea

Question 20

What are the aerobic gram neg rods?

Answer 20

Very large group:

• Enterobbactereaceae
• Pseudomonads
• Vibrios
• Haemophilus
• Legionella
• Helicobacter-like

Question 21

What are the HPV oncoviruses?

Answer 21

HPV 16 and 18 are the major viruses