The document discusses the Gram positive cocci genera Staphylococcus and Streptococcus. It focuses on Staphylococcus, describing their characteristics including being facultatively anaerobic, non-motile, salt tolerant cocci that produce catalase. It discusses several medically important Staphylococcus species like S. aureus, S. epidermidis, S. saprophyticus and their roles in diseases ranging from skin infections to bacteremia, endocarditis, pneumonia and food poisoning. Treatment options depend on antibiotic sensitivity and resistance.

1. GRAM POSITIVE COCCI
(Staphylococcus)
SAMIRA FATTAH HAMID
Ph.D. Medical Bacteriology
College of Health Sciences
Hawler Medical University

2. GRAM POSITIVE COCCI
• Genus Staphylococcus
• Genus Streptococcus

3. GENUS: STAPHYLOCOCCUS
Characteristics:
• Gram positive spherical cells, usually arranged in
grape-like clusters.
• Facultatively anaerobic
• non spore-forming
• non-motile,
• Form single cocci , pairs, tetrads and clusters.

4. GENUS: STAPHYLOCOCCUS
Characteristics:
• They are salt tolerant, capable of growing in media
saturated with Nacl—about 28% salt—which explains
how they tolerate the salt deposited on human skin by
sweat glands.
• synthesizes catalase enzyme which differentiate them
from the streptococci.
• Tolerant to radiation, and heat (up to 60°C for 30
minutes),allowing them to survive on environmental
surfaces in addition to skin.

5. Characteristics:
• Active metabolically, ferment carbohydrates producing lactic acids.
• Produce pigments that vary from white to deep yellow.
• Some are members of the normal microbiota of the skin and mucous
membranes of humans; others cause suppuration, abscess formation and even
fatal septicemia.
• The pathogenic staphylococci often hemolyze blood, coagulate plasma, and
produce a variety of extracellular enzymes and toxins.
GENUS: STAPHYLOCOCCUS

6. The genus Staphylococcus has at least 40 species. The most frequently
encountered species of clinical importance are:
• Staphylococcus aureus
• Staphylococcus epidermidis
• Staphylococcus saprophyticus

7. Less common staphylococcus species:
• Staphylococcus haemolyticus
• Staphylococcus xylosus
• Staphylococcus lentus
• Staphylococcus lugdenensis
• Staphylococcus hominis
• Staphylococcus warneri

8. Staphylococcus aureus
S. aureus is a relatively common human commensal, nasal carriage occurs in 30–
50% of healthy adults, faecal carriage in about 20% and skin carriage in 5–10%.
Antigenic structure
1. Peptidoglycan:
a polysaccharide polymer containing linked subunits, provides the rigid exoskeleton
of the cell wall. destroyed by strong acid or exposure to lysozyme.
It is important in the pathogenesis of infection:
• It trigger production of interleukin-1 and antibodies by monocytes.
• It can be a chemoattractant for polymorphonuclear leukocytes, have endotoxin-like
activity, and activate complement.

9. Antigenic structure
2. Teichoic acid:
polymers of polyribitol–phosphate, are cross- linked to the peptidoglycan
and can be antigenic, can trigger activation of complement.
Staphylococcus aureus

10. Staphylococcus aureus
Antigenic structure
3. Protein A:
Protein A binds to the Fc portion of immunoglobulins (IgG). It is assumed
that “false” binding of immunoglobulins by protein A prevents “correct”
binding of opsonizing antibodies, thus hindering phagocytosis.

11. Antigenic structure
4. Capsule:
• polysaccharide inhibit phagocytosis by polymorphonuclear leukocytes.
• At least 11 serotypes have been identified, with types 5 and 8 responsible
for the majority of infections.
Staphylococcus aureus

12. Enzymes
1. Catalase
Produced by staphylococci converts H2O2 into H2O and O2.
2. Coagulase and clumping factor
Coagulase deposit fibrin on the surface of organism and alter
ingestion by phagocytic cells.
Clumping factor: A surface compound that is responsible for
adherence of the organism to fibrinogen and fibrin.
3. Staphylokinase (Fibrinolysin)-digest fibrin clots
Staphylococcus aureus

14. Staphylococcus aureus
Enzymes
4. Hyaluronidase-Spreading factor- hydrolyze
hyaluronic acid
5. Proteinases-hydrolyze protein
6. Lipases-hydrolyze lipid
7. DNase- Deoxyribonucleotidase
8. β-lactamase-Provides resistance of
staphylococcus to β-lactam antibiotic like
penicillin.

16. Staphylococcus aureus
Toxins
1. Hemolysins
S. aureus possesses four hemolysins, capable of lysing white and red blood
cells.
2. Panton–Valentine Leukocidin
It can kill white blood cells of humans. This toxin is an important virulence
factor in CA-MRSA infections.

17. Staphylococcus aureus
Toxins
3. Exfoliative Toxins
Epidermolytic toxins dissolve the mucopolysaccharide matrix of the
epidermis. composed of two distinct proteins of the same molecular weight.
 Exfoliative toxin A: heat stable (resists boiling for 20 minutes).
 Exfoliative toxin B: heat labile.
4. Toxic Shock Syndrome Toxin
Desquamative toxin produced by S. aureus it binds to major
histocompatibility class (MHC) class II molecules, yielding T-cell stimulation
and causes fever, shock, multiple-organ failure and skin rash.

18. Staphylococcus aureus
Toxins
5. Enterotoxin
There are multiple enterotoxins (A–E, G–J, K–R and U, V), produced
when S. aureus grown in carbohydrate and protein foods. heat stable and
resistant to the action of gut enzymes.
Important causes of food poisoning , Ingestion of 25 μg of enterotoxin B
results in vomiting and diarrhea. The emetic effect of enterotoxin is
probably the result of central nervous system stimulation (vomiting center)
after the toxin acts on neural receptors in the gut.

19. Pathogenesis and clinical features
Staphylococcus causes a variety of medical problems, depending on
the site of infection, the immune state of its host, and the toxins and
enzymes of a particular species or strain secretes.
Cutaneous diseases
• Folliculitis:
Infection of one hair follicle in which the base of the follicle becomes
red, swollen, and pus filled.
• Furuncle
or boil is a large, painful raised nodular extension of folliculitis into
surrounding tissue.
• Carbuncle:
When several furuncles unite, they form a carbuncle (infection of
multiple hair follicle and surrounding skin), which extends deeper into
the tissues.

20. Pathogenesis and clinical features
Cutaneous diseases
• impetigo:
Small, flattened, red patches on the face and limbs,
particularly of children whose immune systems are not
fully developed
• Cellulitis:
Infection of skin and subcutaneous tissue.

21. Pathogenesis and clinical features
Cutaneous diseases
• Staphylococcal scalded skin syndrome:
is a reddening of the skin that typically begins near the
mouth, spreads over the entire body, and is followed by
large blisters that contain clear fluid lacking bacteria or
white blood cells. These are lacking because the
syndrome is caused by exfoliative toxin released by
bacteria growing on the skin rather than in the body.
Within two days, the affected outer layer of skin
(epidermis) peels off in sheets, as if it had been dipped
into boiling water.

22. Pathogenesis and clinical features
Systemic diseases
• Toxic shock syndrome:
(Non-Streptococcal) When strains of Staphylococcus that
produce TSS toxin grow in a wound or in scraped vagina,
the toxin can be absorbed into the blood and cause toxic
shock syndrome, characterized by fever, vomiting, red
rash, extremely low blood pressure, and loss of sheets of
skin.
TSS is fatal to 5% of patients when their blood pressure
falls so low that the brain, heart, and other vital organs
have an inadequate supply of oxygen—a condition
known as shock.

23. Pathogenesis and clinical features
Systemic diseases
• Bacteremia
S. aureus is a common cause of bacteremia , the presence of bacteria in the blood. After
staphylococci enter the blood from a site of infection, they travel to other organs of the
body, which may become infected. Furuncles, vaginal infections, infected surgical
wounds, and contaminated medical devices such as intravascular catheters have all been
implicated in cases of bacteremia.

24. Pathogenesis and clinical features
Systemic diseases
• Endocarditis
S. aureus may attack the lining of the heart (including its
valves), producing a condition called endocarditis.
Typically, patients with endocarditis have nonspecific,
flulike symptoms, but their condition quickly deteriorates
as the amount of blood pumped from the heart drops
quickly.
About 50% of patients with endocarditis do not survive.

25. Pathogenesis and clinical features
Systemic diseases
• Pneumonia and Empyema
Staphylococcus in the blood can invade the lungs, causing pneumonia - an inflammation
of the lungs in which the alveoli (air sacs) and bronchioles (smallest airways) become
filled with fluid.
In 10% of patients with staphylococcal pneumonia, infection spreads to the space between
a lung and the chest wall where pus builds up—a condition known as empyema.

26. Pathogenesis and clinical features
Systemic disease
• Osteomyelitis
When Staphylococcus invades a bone, either through a traumatic wound or via the
blood during bacteremia, it causes osteomyelitis - inflammation of the
bone marrow and the surrounding bone.
Osteomyelitis is characterized by pain in the infected bone accompanied by high fever.
In children, the disease typically occurs in the growing regions of long bones, which
are areas with well-developed blood supplies.
In adults, osteomyelitis is more commonly seen in vertebrae.

27. Pathogenesis and clinical features
Systemic disease
• Food poisoning
Symptoms come on quickly, usually within hours of eating a contaminated food.
Symptoms usually disappear quickly, too, often lasting just half a day.
A staph infection in food usually doesn't cause a fever. Signs and symptoms
include:
• Nausea and vomiting
• Diarrhea
• Dehydration
• Low blood pressure

28. Staphylococcus epidermidis
• S. epidermidis is part of the normal human flora, typically the skin flora,
and less commonly the mucosal flora.
• Although it is not usually pathogenic, patients with compromised
immune systems are at risk of developing infection.
• S. epidermidis is a particular concern for people with catheters or other
surgical implants because it is known to form biofilms that grow on these
devices.
• Being part of the normal skin flora, S. epidermidis is a frequent
contaminant of specimens sent to the diagnostic laboratory.

29. Staphylococcus epidermidis
Diseases
• S. epidermidis causes biofilms to grow on plastic devices
placed within the body like intravenous catheters and
medical prostheses.
• Infection can also occur in dialysis patients by
contaminated device.
• It also causes endocarditis, most often in patients with
defective heart valves.

30. Staphylococcus epidermidis
Diseases
• Occasional cause of infection associated with implanted appliances
and devices.

31. Staphylococcus epidermidis
Role of Staphylococcus epidermidis in acne vulgaris
• Staphylococcus epidermidis in the normal skin is nonpathogenic. But in abnormal
lesions, it becomes pathogenic, likely in acne vulgaris.
• Staphylococcus epidermidis enters the sebaceous gland (where Propionibacterium
acnes the main bacterium that causes acne vulgaris colonizes) and damages the hair
follicles by producing lipolytic enzymes that change the sebum triglyceride to free
fatty acids leading to inflammatory effect.

32. Staphylococcus saprophyticus
S. saprophyticus is part of the normal human flora that colonizes
the:
• Perineum
• Rectum
• Urethra
• Cervix
• Gastrointestinal tract.

33. Staphylococcus saprophyticus
It is a common cause of uncomplicated urinary tract infections (UTIs), particularly in
young sexually active females. Less commonly, it is responsible for complications
including:
• acute pyelonephritis
• Cystitis
• Urethritis
• prostatitis

34. Staphylococcus saprophyticus
• An acute uncomplicated UTI is characterized by dysuria and frequency in an
immunocompetent, non-pregnant adult female and is the most common bacterial
infection in women.
• A complicated infection typically involves a patient that is immunocompromised,
elderly, male, pregnant, diabetic, and/or with urologic abnormalities such as
indwelling catheters or kidney disease.

35. Treatment
• Penicillin sensitive staphylococci………penicillin, ampicillin
• Penicillin resistant staphylococci………cloxacillin, Nafcillin
• Methicillin resistant staphylococci……… Vancomycin