1. The Laboratory diagnosis and susceptibility testing of meticilline-resistant staphylococcus aureus
By:
Maj Anthere Murangwa, MSC
Medical Microbiologist.

2. Outline Introduction Clinical features Introduction
Laboratory diagnosis & Results interpretation
MRSA definition & Transmission
MRSA testing
Recommendation
Introduction
Clinical features
Laboratory diagnosis & Results interpretation
MRSA definition & Transmission
MRSA testing
Recommendation

3. Introduction
Staphylococci or “staph” bacteria commonly live on the skin and in the nose.
Usually, staph bacteria don’t cause any harm.
However, if they get inside the body they can cause an infection.

4. Introduction Cont’
When common antibiotics don’t kill the staph bacteria.
It means the bacteria have become resistant to those antibiotics.
This type of staph is called Methicillin- Resistant Staphylococcus aureus (MRSA).

5. Introduction Cont’ STAPHYLOCOCCUS
Clinically they are grouped into two:
1. Coagulase positive Staphylococci
Staphylococcus aureus
2. Coagulase negative Staphylococci- frequently involved in nosocomial and opportunistic infections
S. epidermidis
S. saprophyticus
S. haemolyticus
S. lugdunensis
S. schleiferi

6. Clinical features
S. Aureus causes Pyogenic diseases and toxin- mediated diseases
1. Pyogenic diseases
Local lesions of skin - impetigo, furuncles, paronychia, cellulitis, folliculitis, etc.
Systemic infections -Septicemia, Endocarditis, Osteomyletis, Post surgical wound infections, etc.

7. Clinical features Cont’
2. Toxin mediated diseases
Food poisoning- (gastroenteritis)
Toxic shock syndrome-
Staphylococcal Scalded skin syndrome (SSSS)

8. Clinical features cont’
Staphylococcal Scalded skin syndrome (SSSS)
Rash in toxic shock syndrome

9. Laboratory Diagnosis Sample collection
Pus and swabs from infected sites, sputum, cerebrospinal fluid, blood for culture, urines, etc.
Faeces, vomit and the remains of food when food poisoning is suspected, nasal swabs from carriers.

10. Laboratory Diagnosis Microscopy
Gram stain and observe for gram positive cocci in clusters, singly and in pairs

11. Laboratory Diagnosis cont’
Culture
Blood agar: S. aureus produces golden-yellow that are beta-haemolytic.
Mannitol salt agar (selective and differential for isolation from faeces -staphylococcal food- poisoning) : yellow colonies

12. Laboratory Diagnosis cont’
Golden-yellow-B- haemolytic colonies
Mannitol Salt Agar test

13. Laboratory Diagnosis cont’
Biochemical tests
S. aureus is:
Coagulase positive
Catalase positive

14. Laboratory Diagnosis cont’
Antimicrobial susceptibility
First line: penicillin, amoxicillin, methicillin, cephalosporins, bactrim, etc.
Second line: Vancomycin, Rifampin, etc.
Third line: Levofloxacin, Ofloxacin, etc.
MIC

15. Methicillin-Resistant Staphylococcus aureus (MRSA)
What is MRSA?
When common antibiotics don’t kill the S. Aureus
The S. Aureus have become resistant to those antibiotics.
This type of staph is called Methicillin-Resistant Staphylococcus aureus (MRSA).

16. MRSA Cont’
Meticillin-resistant S. aureus produce an additional penicillin-binding protein, PBP2a or PBP2 coded by mecA gene in MRSA.
PBP2a or PBP2 confers resistance to all currently available β-lactam agents.

17. MRSA transmission Anyone can get MRSA bacteria.
You can get MRSA by touching someone or something that has the MRSA bacteria then touching your skin or your nose.
Using personal items of someone who has MRSA, such as towels, wash cloths, clothes.
Touching objects, such as public phones or door knobs, that have MRSA bacteria.
Taking too much antibiotics without Dr prescription

18. MRSA testing
Cefoxitin Resistance
Oxacillin Resistance

19. MRSA testing
Antimicrobial susceptibility

20. Recommendation
Physician and Clinician to provide antibiotics to the patient after laboratory results, especially antimicrobial susceptibility.
Take antibiotics exactly as your doctor prescribed.
Apply highly hygiene to avoid both auto infection and contamination from others.

21. Thank you for your attention