Bacteriology Flashcards
Mechanism for MRSA resistance
mec gene (mecA) which produces PBP2a. This has a low affinity for beta lactams.
SCCmec type - hospital and community acquired
Type 1, 2 and 3 - hospital
Type 4 and 5 - community
MRSA lab definition
Oxacillin MIC greater or equal to 4mcg/ml
Catalase positive bacteria
Staphylococcus Pseudomonas aeroginosa Aspagillus fumigatus Candida albicans Enterobacteriaceae (Klebsiella, Serratia) Mycobacterium tuberculosis
What is the Panton-Valentine leukocidin?
A toxin produced by S. aureus which is cytolytic to PMNs, macrophages and monocytes
Bacteria classed as Group A strep
S. pyrogenes
Toxins involved in scarlet fever
Streptococcus pyrogenic exotoxins
Mechanisms Group A Streptococcus uses to avoid phagocytosis
M protein
Polysaccharide capsule
Pathogenesis of Scarlet Fever
Group A Streptoccocus infection releases the toxin sreptoccocal pyrogenic exotoxins. There is then a hypersensitivity reaction to the toxin leading to the rash
VRE - what organism is it most associated with
E. faecium. E. faecalis resistance is significantly more rare
Mechanism of VRE
Vancomycin resistance cluster genes coding for a changed binding terminus D-Ala-D-Ala to D-Ala-D-lactate
Cause of tetanus including bacteriology
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.
Signs of tetanus
Local - muscle spasms and pain, trismus, difficulty swallowing
Generalised - muscle spasms, loss of airway and breathing, cardiovascular instability, fever, seating, GI stasis
Immediate management of tetanus
- Clean wound + abx
- Human Tetanus immune globulin (including intrathecal)
- Support airway and breathing
- Control spasms with sedation, magnesium sulphate, paralytics
What are the live vaccines?
MMR BCG Varicella Zoster Rotavirus Japanese encephalitis Oral typhoid Yellow fever
What are the vaccines recommended routinely in the elderly?
Yearly influenza
Pneumococcal at 65
Herpes zoster at 70
Boostrix if in contact with children eg grandparents
What are the gram positive cocci?
Staphylococci - coagulase pos (S. aureus) or neg (other)
Streptococci - alpha haemolytic (viridans, pneumococcus), beta haemolytic (groups A-G)
Enterococcus
What type of bacteria are clostridia? What are the subtypes?
Gram pos anaerobic rods C. perfringens C. botulinum C. difficile C. tetani
What type of bacteria are neisseria? What are the subtypes?
Gram neg cocci
N. meningitidis
N. gonorrhoea
What are the aerobic gram neg rods?
Very large group:
- Enterobbactereaceae
- Pseudomonads
- Vibrios
- Haemophilus
- Legionella
- Helicobacter-like
What are the HPV oncoviruses?
HPV 16 and 18 are the major viruses
