The document discusses the bacterium Staphylococcus aureus, including MRSA. It describes S. aureus's characteristics and how it can cause infections. MRSA was first identified in the 1940s when some S. aureus strains developed resistance to penicillin. It further discusses how MRSA is transmitted and the differences between CA-MRSA and HA-MRSA. Prevention, treatment options, and challenges like developing resistance are also covered at a high level.

1. JAYSHREE
Ph.D SCHOLAR

2. Staphylococus aureus
 Gram Positive
 Non-motile
 Spherical
 Grows in clumps
 Resembles clumps of grapes
 Golden color- colonies
 Some produce hemolysis
 Some produces coagulase
 Produce catalase enzymes

3. Virulence Determinants of
Staphylococcus aureus

4. Frequency of Staphylococcus aureus
colonization in carriers on various body sites
Nose 100%
Skin chest 45%
Perineum 60%Ankle 10%
Axilla 19%
Hand 90%
Forearm 45%
4

5. S. aureus – as pathogen
• virulent factors (toxins
and enzymes)
• Frequent nosocomial- and
community-acquired
pathogen
• Mode of transmission –
contact
• Clinical manifestations
1/31/2015 5

6. Superficial Infections

7. Scalded Skin Syndrome: Classic Toxic
Shock

8. Systemic Menstrual Toxic Shock

9. Cont…
• The Staphyloccoccus aureus bacterium,
commonly known as staph, was discovered in
the 1880s - painful skin and soft tissue
conditions
• Initially cases were treated by draining the
abscess or boil

10. Cont…
• In the 1940s, medical treatment for S.
aureus infections became routine as
Penicillin was introduced as drug of choice.
• Penicillin- bacterial cell wall synthesis- inflow
of water- cell burst

11. Cont…
• But resistance to penicillin in Staph. aureus -
due to the presence of penicillinases in them.
• Later on due to development of resistance to
penicillin

12. Cont…..
• In 1959 methicillin was introduced for Staph.
aureus resistant to penicillinases (Leonard and
Markey, 2008)
• In recent time resistance leading to use of
vancomycin.

13. Cont..
• Most strains of MRSA are inhibited by
concentrations of vancomycin ranging from
0.5- 2.0 mcg/mL, although strains have been
reported with intermediate sensitivity that
have been called Glycopeptide intermediate
staph aureus or Vancomycin intermediate staph
aureus.

14. What Is MRSA?
• MRSA is the term used for any strain of
Staphylococcus aureus that has developed
resistance to β- lactam antibiotics, which include
the penicillins (methicillins, oxacillin,
dicloxacillin etc.) and cephalosporins
• MRSA causes a variety of disseminated, lethal
infections in humans.
• Has the ability to easily transfer resistant genes to
other species directly and indirectly

15. •Resistance of MRSA to β- lactam antibiotics including
penicillinase stable β- lactam is mediated by the mecA gene.
•This gene is expressed in bacterial cell wall and encodes
for a penicillin binding protein (PBP2a) which has a low
affinity for β- lactam antibiotics (Leonard and Markey, 2008).
•SCCmec element is a genomic island of unknown origin
containing this antibiotic resistant mecA gene (Batabyal et al.,
2012).
how MRSA is resistant to methicillin?

16. How “Tough” is MRSA?
• Staphylococci can survive many extreme
environmental conditions.
• The bacteria can be cultured from dried clinical
material after several months, are relatively heat
resistant, and can tolerate high salt media.
So, “What Do we Do?”
• You can not get rid of MRSA; you can only
control it.

17. How is MRSA spread?
1. Direct contact with infected or colonized
host -human-to-human contact
2. Contaminated intermediate surfaces
-hand towels
-faucets
-tub/shower
3. Airborne fluid droplets

18. CA-MRSA and HA-MRSA
 CA-MRSA
Unique
microbiologic and
genetic properties
compared with
HA-MRSA may
allow the
community strains
to spread more
easily or cause
more skin disease

19. Community-Associated (CA)-MRSA
• CA-MRSA has only been known since the
1990s.
• CA-MRSA is of great concern to public health
professionals because of who it can affect.
• CA-MRSA skin infections are known to spread
in crowded settings

20. Cont…
• CA-MRSA is resistant to
penicillin and methicillin.
• Lead to redness, swelling
and pain resembling to
spider bite.
• Minor skin problems
pimples, insect bites, cuts,
and scrapes especially in
children may lead to MRSA
colonization.

21. Hospital-acquired MRSA (HA-MRSA)
HA-MRSA Healthcare-acquired Methicillin
resistant Staph. aureus
Many hospitals now seeing CA-MRSA in
healthcare associated infections

22. Vancomycin resistance……..?
• Isolate of S. aureus in 1997 was observed
resistant mediated not via acquisition of van A by
a strain of methicillin-resistant S. aureus (MRSA)
but by an unusually thickened cell wall containing
dipeptides capable of binding vancomycin,
thereby reducing availability of the drug for
intracellular target molecules.
• This was the first observation of vancomycin-
intermediate S. aureus (VISA).

23. Cont….
• The predicted mechanism of van A gene
plasmid-mediated transfer from enterococci
to S. aureus was later observed for the first
time in 2002; this was the first description of
vancomycin-resistant S. aureus (VRSA).

25. Drugs against MRSA
• Daptomycin
• Linezolid(belonging to oxazolidiones class)

26. Drugs In Development
• Oritavancin-Binds to normal cell wall
precursors
• Tigecyclin-Works on efflux pumps
• Dalbavancin- Bacteriacidal

27. Who is at risk for MRSA?
 ANYONE can get MRSA – those most at risk:
Spend a lot of time in crowded places such
as hospitals, schools or dorms
Share sports equipment
Share personal hygiene items
Play contact sports
Overuse or misuse antibiotics

28. Can Healthy People Get MRSA?
• Yes. MRSA skin infections are showing up more
frequently in healthy people, with none of the
usual risks factors.
• This type of MRSA - called community-
associated MRSA (CA MRSA) - has been
reported among athletes, prisoners, and military
recruits.

29. Diagnosis
• S. aureus infections in humans are diagnosed
by culture and identification of the organism,
as in animals. (Staphylococcal food poisoning
is diagnosed by examination of the food for the
organisms and/or toxins.).

30. Cont…..
• Methicillin-Resistant Staphylococcus aureus
(MRSA) as the causal agent of nosocomial
infection demands a quick and trustworthy
characterization of isolates

31. Phenotypic Methods
• Antibiogram typing
• Phage typing
• Serotyping
• Biotyping
• Protein electrophoretic typing
Whole cell protein typing
Immunoblotting
Zymotyping

32. Genotypic Methods
• Plasmid DNA analysis
• Chromosomal DNA analysis
• Southern blot analysis of RFLP
• Ribotyping
• Binary typing
• Pulsed field gel electrophoresis

33. Prevention
The best defense against spreading MRSA is to
practice good hygiene, as follows:
• Keep your hands clean
• Use hand sanitizer containing at least 62
percent alcohol.
• Keep cuts and scrapes clean and covered with
a bandage until healed.
• Follow your healthcare provider’s instructions
on proper care of the wound.
• Bandages or tape can be discarded with regular
trash.

34. Cont…
• Avoid contact with other people’s wounds
or bandages.
• Avoid sharing personal items, such as
towels, washcloths, razors, clothes, or
uniforms.
• Wash sheets, towels, and clothes that
become soiled with water and laundry
detergent; use bleach and hot water if
possible.

35. Cont….
• Drying clothes in a hot dryer, rather than air-
drying, also helps kill bacteria in clothes.
• Tell any healthcare providers who treat you if
you have or had an S. aureus or MRSA skin
infection.
• If you have a skin infection that requires
treatment, ask your healthcare provider if you
should be tested for MRSA.

36. Cont….
• Many healthcare providers prescribe drugs that
are not effective against antibiotic-resistant
staph, which delays treatment and creates more
resistant germs.
• Healthcare providers are fighting back against
MRSA infection by tracking bacterial
outbreaks and by investing in products

37. Vaccination
• Development of StaphVAX®, a
polysaccharide conjugate vaccine against S.
aureus infections in process.
• The results of the phase 3 clinical trials of the
vaccine (Staph VAX) will be presented 2006.

38. Future Prospects
• What of the future? Many new avenues are
under exploration.
• Tea-tree oil in a nasal application together with
a body wash was shown to be as effective as
mupirocin with antiseptic washes in the
eradication of carriage of MRSA
• Antiseptic-coated endotracheal tubes are
undergoing trials.

39. Cont…
• Other techniques under investigation include a
hydrogen-peroxide-based gas to decontaminate
the environment, air filtration units and diagnostic
kits, phage therapy and, perhaps the most
interesting
• A search of Medline yielded no published data on
this last approach. Whatever new answers emerge,
we must hope they will not go the way of
methicillin.

40. MRSA- Indian Scenario
• MRSA is endemic in India and is a dangerous
pathogen for hospital acquired infections.
• This study was conducted in Indian tertiary
care centres during a two year period from
January 2008 to December 2009 to determine
the prevalence of MRSA and susceptibility
pattern of S. aureus isolates in India.

41. Cont….
• In India first MRSA, 6th in world was isolated
in 2005 at Kolkata from the cases of wounds in
children.
• Till than it has been reported from various part
of country including animals and supposed to
be major cause of mastitis in bovines (Kiran,
2014).

42. • National Guidelines for controlling MRSA
were published in 1998 and are currently under
revision.
• A two-tier control programme was
recommended.

43. References
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2. Mitchell, David.MRSA.”what’s New”. Inoculum. Volume 8, number 2 (1999) 1-12.
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5. http://www.bioteach.ubc.ca/Biodiversity/AttackOfTheSuperbugs
6. Foster, Timothy. The staphylococcus aureus “superbug”.J. clin Ivestigation
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12. www.FDA.com (FDA archives)
13. www.postgradmed.com/issues/2001/10_01/hoel.htm
14. www.cdc.gov/ncidod/hip/aresist/mrsa_CDCactions.htm
15. www.medscape.com
16. http://www.nabi.com/images/factsheets/fsStaphVAX.pdf
17. http://textbookofbacteriology.net/staph_2.html
18. http://aic-server4.aic.cuhk.edu.hk/web8/0205_MRSA.jpg

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