this is a series of lectures on microbiology, useful for undergraduate and post graduate medical and paramedical students..first lecture on bacteriology..on staphylococci

1. SYSTEMIC MICROBIOLOGY
BACTERIOLOGY
Dr. Ashish V. Jawarkar M.D.

2. GRAM POSITIVE BACTERIA
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STAPHYLOCOCCUS
Dr. Ashish Jawarkar
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3. Introduction
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Bacteria consist of only a single cell
Bacteria fall into a category of life called
the Prokaryotes
There are thousands of species of
bacteria, but all of them are basically one
of three different shapes.
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4. Classification of Bacteria
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Until recently classification has done on the
basis of such traits as:
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shape
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bacilli : rod-shaped
cocci : spherical
spirilla : curved walls
In clusters : actinomyces
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8. Classification of Bacteria
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The Gram stain is named after the 19th
century Danish bacteriologist who developed it.
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The bacterial cells are first stained with a purple dye
called crystal violet.
Then the preparation is treated with alcohol or
acetone.
This washes the stain out of gram-negative cells.
To see them now requires the use of a counterstain of
a different color (e.g., the pink of safranin).
Bacteria that are not decolorized by the
alcohol/acetone wash are gram-positive
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9. Gram Positive bacteria
• Staphylococci and streptococci
constitute the main group of
medically important gram positive
bacteria
• There are also bacilli that are
pathogenic such as Anthrax and
the Clostridia group. These are
also spore forming organisms
• There are also some other gram
positive rods such as Listeria,
Lactobacillus,and Cornybacterium
Dr. Ashish Jawarkar
diptheria
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10. Staphylococci
• Staphylococcus was first identified in
1880 in Aberdeen, United Kingdom, by
the surgeon Sir Alexander Ogston in pus
from a surgical abscess in a knee joint.
[1] This name was later appended to
Staphylococcus aureus by Rosenbach
• Main types
– Staph aureus – coagulase positive
– Staph epidermidis, staph hemolyticus, staph
saphrophyticus – coagulase negative
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11. Description headings for each
bacteria
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Morphology
Growth characteristics
Biochemical reactions
Resistance
Pathogenicity and virulence
Epidemiology
Diseases caused
Laboratory diagnosis
Treatment
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12. Staphylococci
Morphology
• Staphylococci stain dark purple with the
gram stain.
• Staphylococci are arranged in grape like
clusters
• Because they divide in three planes with
daughter cells remaining in close
proximity
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15. Description headings for each
bacteria
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Morphology
Growth characteristics
Biochemical reactions
Resistance
Pathogenicity and virulence
Epidemiology
Diseases caused
Laboratory diagnosis
Treatment
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16. Growth characteristics
• Grow on ordinary media like
nutrient agar
• Temperature 10-42 degree
• Produce golden yellow pigment
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18. Description headings for each
bacteria
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Morphology
Growth characteristics
Biochemical reactions
Resistance
Pathogenicity and virulence
Epidemiology
Diseases caused
Laboratory diagnosis
Treatment
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19. Staphylococci
biochemical reactions
• The most virulent form of
staphylococcus, SA also secretes
coagulase, that causes citrated
plasma to clot. These are referred
to as coagulase positive
• There are other staph that do not
have this ability and are labeled
coagulase negative
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20. Coagulase test
• Slide method or tube method
• In tube method – we add culture of
staphylococci and rabbit plasma
• Look for clot formation
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22. Description headings for each
bacteria
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Morphology
Growth characteristics
Biochemical reactions
Resistance
Pathogenicity and virulence
Epidemiology
Diseases caused
Laboratory diagnosis
Treatment
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23. Resistance
• Resistant to drying – can remain in
dried pus for 3-6 months
• resistant forms to penicillin have
emerged
– Produce penicillinase which inactivates
penicillin
– Change surface receptors for
penicillin
– Develop tolerance to penicillin –
bacteria inactivated, not killed
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24. Description headings for each
bacteria
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Morphology
Growth characteristics
Biochemical reactions
Resistance
Pathogenicity and virulence
Epidemiology
Diseases caused
Laboratory diagnosis
Treatment
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25. Pathogenicity
• Cell surface protein – protein A –
antiphagocytic property
• Clumping factor – surface protein – responsible
for slide coagulase test
• Produce enzyme coagulase
• Produce toxins
– Hemolytic toxins (leucocidins)
– Enterotoxin – causes food poisoning – vomitting,
diarrhoea etc
– Toxic shock syndrome toxin – produces hypotension
and rash
– Epidermolytic toxin – causes STAPHYLOCOCCAL
SCALDED SKIN SYNDROME (ssss)
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26. Description headings for each
bacteria
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Morphology
Growth characteristics
Biochemical reactions
Resistance
Pathogenicity and virulence
Epidemiology
Diseases caused
Laboratory diagnosis
Treatment
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27. Staphylococcus aureus
epidemiology
• Carried by 20-40 % of healthy
individuals in their mouth or on their
skin
• It also found in their nasal mucosa
• Vagina – increased risk of TSS during
menstruation
• Umbilical stump infected during birth
• Fomites carry staphylococci for months
• Nosocomial infections by MRSA
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28. Description headings for each
bacteria
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Morphology
Growth characteristics
Biochemical reactions
Resistance
Pathogenicity and virulence
Epidemiology
Diseases caused
Laboratory diagnosis
Treatment
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29. Diseases caused by staphylococci
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31. cellulitis
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32. boils
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33. boils
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34. Description headings for each
bacteria
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Morphology
Growth characteristics
Biochemical reactions
Resistance
Pathogenicity and virulence
Epidemiology
Diseases caused
Laboratory diagnosis
Treatment
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35. Lab diagnosis
• Specimen to be collected
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Skin – pus
Respiratory inf – sputum
Food poisoning – stool
For detection of carriers – nasal swab
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36. Staining and microsocopy
• Gram stained smears
– Gram positive cocci in grape like
clusters
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37. Culture
• Nutrient agar/blood agar
– Colonies with golden yellow pigment
• Coagulase test
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38. Antibiotic susceptibility testing
• In case of suspected hospital
acquired infection
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39. Description headings for each
bacteria
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Morphology
Growth characteristics
Biochemical reactions
Resistance
Pathogenicity and virulence
Epidemiology
Diseases caused
Laboratory diagnosis
Treatment
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40. Treatment
• Penicillin
• In resistant cases – cloxacillin
• For MRSA - vancomycin
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41. Coagulase negative staph
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S. epidermidis – stitch abcess, grows on
implants
S. saprophyticus – causes UTI
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42. THANK YOU
Dr. Ashish Jawarkar
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