Gram positive and gram negative bacteria

1. Presented by
MAHANTHESHK
UMAR.G.T.
M.Sc.,(Biotech)

2. Gram staining is the use of stains to differentiate between
the two major types of bacteria
Is called a differential stain for that very reason
Helps to understand different characteristics of bacteria
Has been perfected by modification of the original
experiment over the years
Widely used from high school experiments to clinical
microbiology laboratories

3. Method invented by Hans Christain Gram in 1884.
Was originally devised to make bacteria more visible.
He observed that some bacteria destained after he washed it
with ethanol (typhus bacillus).
This unstaining of certain bacteria was due to certain
bacteria having thin cell walls(He called those gram
negatives).
The stained ones were named gram positive.
His methods were revised and now we stain both gram
negative and gram positives for better visual under the
microscope .

4. Gram staining is used to differentiate between two
different groups of bacteria.
The classification helps to identify some of the
characteristics the bacteria may have.
Method was adopted and is widely used as it is cost
effective, easy and the results are reliable.
Method should not be used to diagnosis or for specific
identification as it only distinguishes one large group to
another and not specific species of bacteria.

6. They are gram positive cocci that occur in grape like
clusters.
They are ubiquitous and the most common cause of
localized suppurative lesions in human beings.

7. 2 groups:
Coagulase positive
(Staphylococcus
aureus)
Coagulase negative
staphylococci (CoNS)

8. Morphology:
Spherical cocci
Approximately 1µm in diameter
Arranged in grape like clusters.
This is due to cell division
occurring in 3 planes; with
daughter cells tending to remain
close proximity.
They stain readily with aniline
dyes and are uniformly gram
positive.

9. Aerobes and facultative anaerobes
Opt. Temp. :37 ºC
pH: 7.5
They can grow readily on ordinary media.

10. Nutrient agar
Blood agar
MacConkey agar
Milk agar
Phenolphthalein phosphate agar
Selective salt media

11. Sugar fermentation
Catalase
Lipolytic
Phosphatase test
Deoxyribonuclease test

12.  Staphylococcus aureus and the
other micro coccaceae are among
the hardiest of the non-sporing
bacteria.
 They have been isolated from
dried pus after 2-3 months.
 It withstands moist heat at 60 ºC
for 30 min but is killed after 60
min.

13. Cytolytic toxins
Enterotoxins
Toxic shock syndrome toxin-I
(TSST-I)
Epidermolytic toxins
(Exfoliative toxins)

14. Coagulase
Coagulase test
Slide coagulase test
Tube coagulase test

15. Cutaneous infections
Deep infections
Toxin mediated diseases
• Food poisoning
• Toxic shock syndrome (TSS)
• Exfoliate diseases

16. Specimens
Direct microscopy
Culture
Identification
Antibiotic sensitivity tests
Bacteriophage typing
Serological tests

17.  Benzyl penicillin
 Patients allergic to penicillins may be
given erythromycin, vancomycin,
first generation cephalosporins.
 For cutaneous infections, oral
therapy with a semisynthetic
penicillin such as cloxacillin or
dicloxacillin is usually efficacious.
 For mild superficial lesions,
application of drugs as bacitracin,
chlorhexidine or mupirocin may be
sufficient.

18.  Sitch abscesses; endocarditid bacteremia
 Osteomyelitis
 Wound Infections
 Prosthetic Joint infections

20.  Streptococcusis a genus of Gram-positive coccus (plural cocci) or spherical bacteria
that belongs to the family Streptococcaceae, within the
order Lactobacillales (lactic acid bacteria), in the phylum Firmicutes
 The genus streptococcus comprises of gram-positive cocci that grow in pairs of
chains
 They are normal flora of humans and animals

23.  Biochemical and other criteria are also used in defining various species within a
single serogroup, and some species contain strains of more than one serogroup.
1.Morphology
2.Cultural Characteristics
3.Biochemical Reaction
4.Antigenic Structure
5.Toxins and Enzymes
6.Pathogenesis
7.Diseases
8. Diagnosis

24.  Streptococcus pyogenes are gram-positive,
spherical to ovoid organisms 0.5-1.0 mm in
diameter
 The organism grows in short or moderately
long chains.
 Chain formation is due to the cocci dividing
in one plane only and the daughter cells
failing to separate completely.

25.  They are aerobes and facultative
anaerobes, growing best at
temperature of 370 C.
 The optimal pH growth is 7.4-7.6
 The exacting in nutritive requirements,
growth accuring only in media
containing fermentable carbohydrates
or enriched with Blood or Serum Media

26.  S. pyogenes is Catalase negative.
 Insoluble in 10% bile unlike S.
pneumonia.
 It ferments several sugars producing
acid and no gas.
 Hydrolysis of pyrrolidinyl
naphthylamine(PYR test) is positive.

27.  1.Capsule.
 2.Group-specific polysaccharide
antigen.
 3.Type specific antigen.

28.  1.Hemolysins
 2.Pyrogenic
exotoxins
 3.DNA
(Streptodornase)
 4.Streptokinase
 5.Hyaluronidase
 6.Proteinase
 7.Other enzymes

29.  Acute diseases
associated with S.
pyogenes occur
chiefly in the
respiratory tract,
bloodstreams, or the
skin.
 Two post
streptococcal
sequelae, occur in 1-
3% of untreated
infections

30.  1.Respiratory infections
I. A. Sore throat infection
II. B. Suppurative infections
 2.Skin and Soft Tissue Infections
 3.Other Suppurative Infection
I. A. Puerperal sepsis
II. B. Non-suppurative Sequelae