staphylococcal Species, Classification, Structure, morphology, Colony characteristics, Growth and biochemical Characterization,, Diagnosis and treatments of staphylococcal infections

1. Staphylococcal infection
Bilal Nasir

2. Staphylococcus
• Staphylococcus is a genus of Gram-positive
• cause a wide variety of infections in humans and other animals
• Certain toxin are produced by different Species
• Staphylococcal toxins are a common cause of food poisoning
• Staphylococci are also known to be a cause of bacterial conjunctivitis.
• Staphylococcus aureus can cause a number of different skin diseases
• Among neurosurgical patients, it can cause community-acquired meningitis
• commonly found on the skin or in the nose of even healthy individuals
• Normally cause no problems or result in relatively minor skin infections.

3. Staphylococcus
• Sir Alexander Ogston, a Scottish surgeon, first showed in 1880 that a
number of human pyogenic diseases were associated with a cluster-
forming micro-organism.
• He introduced the name 'staphylococcus' (Greek: staphyle =bunch of
grapes; kokkos = grain or berry),
• now used as the genus name for a group of facultatively anaerobic,
catalase-positive, Gram positive cocci
• Gram positive cocci ( from Greek staphyle, means bunch of grapes ) that
• occur singly and in pairs, short chains and irregular grape-like clusters

4. Staphylococcus

5. Classification
• Family : Micrococcaceae
• Genus : Micrococcus and Staphylococcus
• Species : S. aureus, S. saprophyticus, S. epidermidis
• More than 20 species

6. Species of genus Staphylococcus
• The genus Staphylococcus contains about forty species and subspecies today.
• Only some of them are important as human pathogens:
–Staphylococcus aureus
–Staphylococcus epidermidis
–Staphylococcus hominis
–Staphylococcus haemolyticus
–Staphylococcus saprophyticus
–others

7. Structure and Physiology
• Gram-positive cocci, non-motile, facultative anaerobes
• Cells occur in grapelike clusters
• Cells division occurs along different planes and the daughter cells remain
attached to one another
• Salt-tolerant: allows them to tolerate the salt present on human skin
• Tolerant of desiccation: allows survival on environmental surfaces (fomites)

8. The species Staphylococcus aureus
Morphology
• Gram-positive, spherical cells, mostly arranged in irregular grape like clusters.
• Polysaccharide capsule is only rarely found on cells.
• The peptidoglycan layer is the major structural component of the cell wall.
• It is important in the pathogenesis of staphylococcal infections.
• Other important component of cell wall is teichoic acid.
• Protein A is the major protein component of the cell wall.
• It is located on the cell surface but is also released into the culture medium during the cell
growth.
• A unique property of protein A is its ability to bind to the Fc part of all IgG molecules except IgG3.
• It is not an antigen-antibody specific reaction.

9. S aureus
A Unique Organism

11. Physiology and structure
• Capsule or polysaccharide slime layer
• Peptidoglycan layer
• Teichoic acid
• Protein A
• Cytoplasmatic membrane
• Clumping factor
• Cytoplasma

12. What is Capsule or polysaccharide slime layer?
• A loose-fitting, polysaccharide layer (slime layer) is only occasionally
found in staphylococci cultured in vitro, but is believed to be more
commonly present in vivo.
• Eleven capsular serotypes have been identified in S. aureus, with
serotypes 5 and 7 associated with majority of infections.

13. Capsule helps Staphylococcus species
• The capsule protects the bacteria by inhibiting the chemotaxis and
phagocytosis of staphylococci by polymorph nuclear leukocytes, as
well as by inhibiting the proliferation of mononuclear cells.
• It is also facilitates the adherence of bacteria to catheters and other
synthetic material.

14. Staphylococcal enzymes
• – Coagulase
• –Catalase
• –Hyaluronidase
• –Fibrinolysin
• –Lipases
• –Nuclease
• –Penicillinase

15. Enzymes
Coagulase
– Triggers blood clotting
Hyaluronidase
– Breaks down hyaluronic acid, enabling the bacteria to spread between cells
Staphylokinase
– Dissolves fibrin threads in blood clots, allowing Staphylococcus aureus to free itself
from clots
Lipases
– Digest lipids, allowing staphylococcus to grow on the skin’s surface and in
cutaneous oil glands
-lactamase
– Breaks down penicillin
– Allows the bacteria to survive treatment with -lactam antimicrobial drugs

16. Protein A
• The surface of most S. aureus strains (but not the coagulase-negative
staphylococci) is uniformly coated with protein A.
• This protein is covalently linked to the peptidoglycan layer and has a unique
affinity for binding to the Fc receptor of immunoglobulin IgG.
• The presence of protein A has been exploited in some serological tests,
• Additionally, detection of protein A can be used as a specific identification test for
S. aureus.

17. Peptidoglycan
• Half of the cell wall by weight is peptidoglycan, a feature common to
gram-positive bacteria.
• The subunits of peptidoglycan are N-acetylmuramic acid and N-
acetylglucosoamine.
• Unlike gram-negative bacteria, the peptidoglycan layer in gram-
positive bacteria consists of many cross-linked layers, which makes
the cell wall more rigid.

18. Teichoic acid
• Teichoic acid is species-specific, phosphate containing polymers that
are bound covalently to the peptidoglycan layer or through lipophilic
linkage to the cytoplasmic membrane (lipoteichoic acid).
• Teichoic acid mediates the attachment of staphylococci to mucosal
surfaces through its specific binding to fibronectin

19. surface proteins
Other surface proteins that appear to be important for adherence to
host tissues include:
• collagen-binding protein
• elastin-binding protein
• fibronectin-binding protein

20. Cytoplasmic membrane
• The cytoplasmic membrane is made up of a complex of proteins,
lipids, and small amount of carbohydrates.
• It serve as an osmotic barrier for the cell and provides an anchorage
for the cellular biosynthetic and respiratory enzymes.

21. Staphylococcal toxins
• S. aureus produces many virulence factors, including at
least five cytolytic or membrane-damaging toxins:
– alpha toxin
– beta toxin
– delta toxin
– gamma toxin
– Panton-Valentin toxin
– two exfoliative toxins
– eigth enterotoxins (A-E, G-I)
– Toxic Shock Syndrome Toxin 1 (TSST-1)

22. Toxic shock syndrome toxin (TSST-1)
• Toxic shock syndrome toxin (TSST-1)
is a super-antigen capable of
activating large number of T cells
• (TSST-1) Was associated with use of tampons
but is also known to be associated
with postoperative wound or soft
tissue infections

23. TSST and other Toxins
• The enterotoxins and TSST-1 belong to a
class of polypeptide known as super
antigens.
•
• Staphylococcus aureus strains produce
several other extracellular, biologically
active substances, including proteases,
phosphatases, lipases, lysozyme etc.

25. Exfoliative toxins
• Staphylococcal scalded skin syndrome
(SSSS), a spectrum of diseases
characterized by exfoliative dermatitis, is
mediated by exfoliative toxins.
• The prevalence of toxin production in S.
aureus strains varies geographically but is
generally less than 5% to 10%.

26. Enterotoxins
• Eight serologically distinct staphylococcal
enterotoxins (A-E, G-I) and three subtypes
of enterotoxin C have been identified.
• The enterotoxin are stable to heating at 100
C for 30 minutes and are resistant to
hydrolysis by gastric and jejunal enzymes

27. Enterotoxins
• Thus, once a food product has been contaminated with
enterotoxin-producing staphylococci and the toxin have been
produced, neither reheating the food nor the digestive
process will be protective.
• These toxins are produced by 30% to 50% of all S. aureus
strains.
• Enterotoxin A is most commonly associated with disease.
Enterotoxins C and D are found in contaminated milk products,
and enterotoxin B causes staphylococcal pseudomembranous
enterocolitis.

28. What is the role of Coagulase
• The role of coagulase in the
pathogenesis of disease is
speculative, but coagulase may cause
the formation of fibrin layer around a
staphylococcal abscess, thus
localizing the infection and
protecting the organisms from
phagocytosis

29. Hyaluronidase
• Hyaluronidase hydrolyzes hyaluronic
acid, the acidic mucopolysaccharides
present in the acellular matrix of
connective tissue.
• This enzyme facilitates the spread of S.
aureus in tissues.
• More than 90% of S. aureus strains
produce this enzyme.

30. Fibrinolysin
• Fibrinolysin, also called staphylokinase, is
produced by virtually all S. aureus strains
and can dissolve fibrin clots.
• Staphylokinase is distinct from the
fibrinolytic enzymes produced by
streptococci.

31. coagulase
• The genus Staphylococcus can be divided into
two subgroups
(on the basis of its ability to clot blood
plasma by enzyme coagulase):
• coagulase-positive
• coagulase-negative.

32. Staphylococcal Diseases
• Systemic Disease
• Toxic shock syndrome-TSS toxin is absorbed into the
blood and causes shock
• Bacteremia-presence of bacteria in the blood
• Endocarditis-occurs when bacteria attack the lining of the heart
• Pneumonia-inflammation of the lungs in which the
alveoli and bronchioles become filled with fluid
• Osteomyelitis-inflammation of the bone marrow and
the surrounding bone

33. Boil (Furuncle )

34. Surgical wound infections:
many causes including S. aureus

35. Diagnosis
• Microscopy – smears of clinical materials
are stained according to Gram stain
• Cultivation on solid media (agar, usually
blood agar)
• Biochemical tests
• Phage typing – susceptibility of S. aureus
strains to various temperature phages

36. Diagnosis
• Specimen
• Smear
• Culture
• Coagulase test
• Biochemical Reactions
• Antibiograms
• Typing

37. Clinical Concerns and Treatment
• 95% have penicillinase and are resistant to
penicillin and ampicillin
• MRSA – methicillin-resistant S. aureus – carry
multiple resistance
– Some strains have resistance to all major
drug groups except vancomycin
• Abscesses have to be surgically perforated
• Systemic infections require intensive lengthy
therapy

38. Treatment
• Antistaphylococcal antibiotics of the first choice:
–vancomycin
– oxacillin (methicillin)
– cephalosporins of I. generation (cefazolin, cephalotin)
• Antistaphylococcal antibiotics of the second choice:
– lincosamides (e.g. clindamycin)
– glycopeptides (vancomycin, teicoplanin)
– linezolid
– tigecyklin
– daptomycin
– and others

39. Antibiotic sensitivity pattern
• Very variable and not predictable
• Very imp. In Pt. Management
• Mechanisms
– 1.B lactamase production - plasmid mediated
• Has made S. aureus resistant to penicillin group of antibiotics -
90% of S. aureus (Gp A)
• B lactamase stable penicillin's (cloxacillin, oxacillin, methicillin)
used
– 2. Alteration of penicillin binding proteins
• (Chromosomal mediated)
• Has made S. aureus resistant to B lactamase stable penicillins
• 10-20% S. aureus Gp (B) GH Colombo/THP resistant to all
Penicillins and Cephalosporins)
• Vancomycin is the drug of choice

40. Prevention
– Hand antisepsis is the most important
measure in preventing nosocomial
infections
– Also important is the proper cleansing of
wounds and surgical openings, aseptic use
of catheters or indwelling needles, an
appropriate use of antiseptics