A brief description of the bacterium Staphylococcus Aureus.

1. STAPHYLOCOCCUS AUREUS
SUBMITTEDTO: PROF. SADIA ZIA

2. CONTENTS
▪ ABSTRACT
▪ INTRODUCTION
▪ CHARACTERISTICS
▪ MORPHOLOGY
▪ GROWTH
▪ SENSITIVITY AND
RESISTANCE
▪ TREATMENT IN LABS
▪ EPIDEMIOLOGY
▪ QUORUM SENSING
▪ APPLICATIONS OF QS
▪ DISEASES
▪ TREATMENT OF INFECTIONS
▪ RECENT RESEARCHES
▪ FUTURE PERSPECTIVES
▪ References

3. ABSTRACT:
▪ This article covers the epidemiology, virulence, growth and
identification of the gram positive bacterium staphylococcus aureus.
Its types, MRSA,VRSA andVISA are explained, the culture media in
which its grown, the reason of its resistance, sensitivity and virulence
has been explained.The cultures (lawn and streak) are shown in
different media and identification tests.
▪ This article also covers the daily uses or applications of
Staphylococcus aureus which is the result of the 3rd most widely
studied quorum sensing of it’s biofilms.

4. INTRODUCTION
▪ It is a gram-positive, round shaped
bacterium that is a member of the
Firmicutes and it is present in the normal
human flora, frequently in the nose,
respiratory tract, axillae and on the skin.

5. CLASSIFICATION
RELATED SPECIES:
• S. epidermidis
• S. saprophyticus
• S. haemolyticus
Bacteria
Firmicutes
Cocci
Coccus
Staphylococcaceae
Staphylococcus
Staphylococcus
Aureus

6. GENERAL CHARACTERISTICS
▪ Coagulase positive
▪ Heat stable – thermo nuclease
▪ DNase positive.
▪ Golden yellow pigmentation
▪ Hemolysis
▪ Ferment mannitol
▪ Gelatin liquefy
▪ Protein A
▪ Catalase positive
▪ Facultative anaerobe
▪ Non-motile
▪ Non-sporing
▪ Occasionally capsulated
▪ Clumping factor
▪ NaCl tolerance
▪ Oxidase positive
▪ Hydrolyses urea
▪ Indole negative
▪ MR,VP positive

7. MORPHOLOGY
▪ Gram positive
▪ 0.5 to 1.5 micro in size
▪ Arranged in grape like clusters
▪ Capsulated (A few) capsulated are more
virulent.
It is well-adapted to colonize the human skin
and our bodies probably provides major
ecological niches for this species. Why?
Because the surface proteins of this bacteria
are a perfect match for human protein
receptors. SA makes two primary transcripts
RNA 2 & RNA 3.These are generated by AgR
locus and originated from P2 and P3 promoters
respectively.These transcripts are present in
our body that’s why our body recognizes this
bacteria as its own.

8. FACTS AND FIGURES:
▪ 60% is naturally found in us by birth.
▪ Out of 100%. Overtime, 20% of the population will always be
colonized by S.A, 60% are sometimes colonized and 20% are never
colonized.
▪ 30% of the healthy humans carry this on their nose, throat and skin.
COLONIZATION?
When bacteria live inside your body but doesn’t harm it or produces no
virulence then it is said to be colonized.When they create virulence,
they are no more called as colonized!

9. GROWTH and REPRODUCTION:
▪ It grows a-sexually through binary fission.
▪ CULTURAL CHARACTERISTICS
1. Temperature: 7 – 48 ֯C, with an optimum temperature of 37 ֯C.
2. pH: 6 – 7 (6.8 usually).
▪ MEDIA:
Grows in basal media as
1. Nutrient Agar: circular colonies, smooth and opaque, resembles oil paint
2. Blood Agar: Colonies are bigger than Nutrient, zone of beta hemolysis
3. MacConkey Agar: Small, opaque, pink
4. Liquid media: uniform turbidity, no pigmentation
And there are different other media with 10% NaCl, lithium chloride, tellurite and
polymyxin.

10. GROWTH MEDIA:
Mac-conkey’s
Agar Blood Agar
Nutrient Agar
LIQUID media

11. GROWTH PATTERNS:
▪ The growth period or incubation time for staphylococcus aureus is
27-30 minutes in Heart-infusion broth media.

14. SENSITIVITY AND RESISTANCE:
▪ It rapidly develops drug resistance, antibiotics should be cautiously
devised. It shows resistance to β-lactam antibiotics in many ways:
▪ Production of β-lactamase enzyme: It cleaves the β-lactam ring
▪ Plasmid coded resistance, can be transferred between S. aureus
through transduction.
▪ Produced by >90% of strains of S. aureus.
▪ Resistance can be overcome by addition of β-lactamase inhibitors
such as clavulanic acid or sulbactam.
▪ By alteration of PBP: Discussed in detail in the section below, as
MRSA shows this resistance.

15. SENSITIVITY AND RESISTANCE:

16. METHICILLIN RESISTANT STAPHYLOCOCCUS
AUREUS
The thing that differentiates it
from normal S. aureus is that
it alters the penicillin binding
protein present in S. aureus
cell membrane (PBP-2a). It is
mediated by mecA gene. This
gene is chromosomally coded.
This PBP-2a has less affinity
for β-lactam antibiotics;
hence MRSA strains are
resistant to all β-lactam
antibiotics. There are further
two types of MRSA.

17. MRSA:

19. VRSA & VISA:
▪ Over use of vancomycin may lead to its resistance, which is of two
types:
▪ VRSA: (Vancomycin Resistant Staphylococcus Aureus) High grade
resistance.
▪ VISA: (Vancomycin Intermediate Staphylococcus Aureus) Low grade
resistance.
▪ VISA is more frequent thanVRSA. VRSA is mediated by van gene A.
it is believed to be acquired from a vancomycin resistant strain of
Enterococcus fecalis by horizontal conjugal transfer. VISA is due to
the cell wall thickness of S. aureus.

20. TREATMENT OF S.AUREUS IN LABS:
▪ This article covers the identification of S. aureus isolates in
laboratories.
▪ Coagulase test: It is the most commonly used biochemical test for
identification of S. aureus, it is of 2 types:
– Tube coagulase: Free coagulase detection. Colony of S. aureus is emulsified in
one mL of diluted plasma in a test tube and incubated at 37 ֯C preferably in
water bath for up to 4 hours. Positive: it is indicated by formation of a clot that
doesn’t flow when the test tube is tilted. Any degree of clot formation is
considered as positive. If negative, re-incubate overnight and re-examine for
delayed clots.
▪ Slide coagulase.

21. Phosphatase test:
This test is positive for S. aureus, organism is inoculated on
phenolphthalein diphosphate containing media and later the colonies
grown are exposed to ammonia vapor.
S.aureus
Splits
phenolphthalein
diphosphate in
media
Releases free
phenolphthalein
Reacts with
ammonia
vapors
Colonies turn
pink

22. EPIDEMIOLOGY:
▪ QS in S. aureus via the accessory gene regulator (agr) has been assigned a central role in
pathogenesis of S. aureus while the control of virulence gene expression in vitro by agr
has been selectively straightforward to describe regulation of both the quorum
response itself and virulence genes. In vivo is considerably less complex.
Quorum sensing depends on the environment in which S. aureus lives.Q.S has been
developed in S. aureus to communicate cell to cell and regulate numerous colonization.
They communicate to share info about cell density and adjust gene expression
accordingly.They enable bacteria to express genetically expansion process as collective
only when the impact of those process on the environment
Its phenotype effects the behavior and pathogenesis of biofilm in S. aureus.
S. aureus colonizes to epithelial surfaces of human. It considers as normal part of
human flora and regarded as transient member.
S.A have many cell surface virulence factors (such as protein A) and secrete exo-toxins
and enzymes that allows strains to cause a myriad of infections.These cause skin
syndromes, sepsis, necrotizing pneumonia, and toxic shock syndrome. No single cell
surface has been shown to mucus level of skin. If one attaches go mucus of the skin it
culturize and cause severe and dangerous diseases.
▪ 2 primary transcripts RNA 2 and RNA 3 are generated by Agr locus and originate
from P2 and P3 promoters respectively.

23. QS in S.AUREUS
▪ Q.S is involved in biofilm development of many organisms but
quorum sensing involved in the S.aureus inhibits the biofilm
production naturally.The agr (accessory gene regulator) is the
prime component of QS in S.aureus.
▪ It functions as a decision making process, cell interaction and
standard response to typical stimuli.

24. APPLICATIONS / USES:

27. TYPING OF S.AUREUS
Typing is especially useful in
outbreaks such as food
poisoning affecting a larger
community.
Typing methods include:
Phenotypic methods:
Bacteriophage typing and
antibiogram typing
Genotypic methods: PCR –
RFLP, ribotyping, PFGE (Pulse
field gel electrophoresis) and
sequence based typing.

28. VIRULENCE FACTORS:

29. S.AUREUS AS PATHOGEN

30. DISEASES:
 Diseases due to medicinal equipment contamination:
 Intravascular catheters septecimis
 Endo-tracheal tube pneumonia.
 Superficial and deep infections:
 Skin infections: folliculitis, boils, wounds and burns infections.
 Respiratory infections: tonsillitis, sinusitis, otitis.
 CNS infections: meningitis, brain abscess, intracranial thrombophlebitis
 Endovascular Infections: bacteremia, endocarditis, septicemiae
 Urinary infections
 Musculoskeletal: osteomyelitis, arthritis, pyomyositis
 Toxin Mediated Diseases:
 Food poisoning
 Staphylococcal scalded skin Syndrome (SSSS)
 Toxic shock syndrome

31. DESCRIPTION:

32. DISEASES:
Scalded skin syndrome
endocarditis
impetigo.
rashes

33. TREATMENT OF INFECTIONS

34. TREATMENT PROCEDURE FOR ENDOCARDITIS:

35. RECENT RESEARCHES:
▪ Recent research into quorum sensing systems of S. aureus has
produced compounds that can disrupt the bacteria's ability to
communicate, thereby disabling or diminishing the bacteria's ability
to become pathogenic.Therefore, the body is not compromised by
cell damage, inflammation, toxicity, or other detrimental effects of
the bacteria.This gives the body time to eradicate the bacteria
naturally through normal immune system functions.
▪ It is being researched for the use in food technology.
▪ There is a research out there showing colloidal silver killing MRSA.

36. FUTURE PERSPECTIVES
▪ QS inhibitors have provided evidence of alternative method for fighting
bacterial infections. QS inhibitors can be isolated from the huge natural
pool of chemicals and are more compatible for the human.
▪ Many researches are going on the gene expression control of the QS in
bacteria and they may be able to replace antibiotics in near future.
▪ In future, we are focusing on some of its strains, when grown in specific
cheese mediated conditions, show positive results for the fermentation and
preservation of that specific cheese.
▪ Resistant strains of MRSA are being used for vaccination in animals,
because the presence of this strand doesn’t allow any other organism to
settle in (quorum sensing and virulence factors).

37. REFRENCES:
▪ A textbook of Microbiology, Second edition (R.Vasanth)
▪ Essentials of Microbiology
▪ Principles of Biochemistry (K.R.Aneja)
▪ Review of Microbiology and Immunology
▪ Microbiology, an introduction (Gerard J.Tortora, Berdell R. Funke)
▪ Review of Microbiology and Immunology, Fifth edition (A.S.Sankrey)
▪ www.ncbi.nlm.nih.gov/

38. GROUP 1 (BSBT-A):
AMNA ASIF (0038)
HAFSA KHALID (0027)
HAIFA NOOR (0003)
MAHA SOHAIL (0049)
OSSAMA BIN ARIF (0034)
MEERUB SHAKEEL (0008)
AHMED RIZWAN (0005)
KHADIJA UMER (0043)
UROOJ ALI (0007)
THANKS!