staphylococci 2011
TRANSCRIPT
STAPHYLOCOCCI
Definition: Gram +ve cocci arranged in clusters.
All Catalase test +ve # [ streptococci] .All Oxidase negative #
[Neisseria]
2
Gram positive cocci in clusters staphylococci
MSA NA BA
White colonies Pigmented golden yellow
1COLONIAL
MORPHOLOGY
Pigmented colonies of staph on NA
Complete ( β )2
HEAMOLYSIS
Hemolytic staphylococci on BA
Hemolytic staphylococci on BA
Ferment mannitol
(yellow color)
Don’t Ferment mannitol (red
color )
3FERMENTATION
Staphylococci on mannitol salt agarpathogenic (F+) non pathogenic(F-)
Staphylococci on mannitol salt agar pathogenic (F+)
Oxidase Catalase-ve +ve
4BIOCHEMICAL
REACTION
Catalase
2H2O2 O2 + 2H2OStreptococci vs. Staphylococci
Differential Characteristics
Catalase POS
Staphylococcus
Catalase NEG
S. aureus
Coagulase
Fibrinogen Fibrin
Differential Characteristics
Coagulase NEG
Coagulase POS
Staphylococcus aureus
COAGULASE TEST
Staphylococci
Coagulase +ve
(pathogenic)
Coagulase –ve
(non-pathogenic)
Staph. aureusStaph.
epidermidis
Staph.
saprophyticus
Pathogenic Non-pathogenic
1- coagulase +ve 1- Coagulase –ve.
Culture media 2- Pigmented golden yellow on NA 2- White colonies.
3- Haemolysis on BA. 3- No hemolysis on BA
4- Ferment mannitol on MSA . 4- Don not ferment
mannitol.
Biochemical reactions of staphylococci
Coagulase +ve Coagulase –veMannitol fermentation +ve Mannitol fermentation –ve
1-Novobiocin sensitive.* S. epidermidis.
2-Nov. resistant* S. saprophyticus.
Difference between pathogenic and non pathogenic
Novobiocin testStaph epidermidis ---S Staph saprophytics ---R
Staph. aureus has several cell wall components and antigens: 1- Peptidoglycan polymer. 2- Telchoic acids that mediate adherence of the organism to mucosal cells.
3- Protein A: 90% of staph. aureus posses this antigen. It is antiphagocytic. Protein A binds IgG molecule non-specifically through Fc portion leaving specific Fab sites free to combine with specific antigen. When suspension of such sensitized staphylococci is treated with homologous (test) antigen, the antigen combines with free Fab sites of IgG attached to staph cells leading to visible clumping of staphylococci within two minutes. It is known as “coagglutination”.
Antigenic structure
4- Clumping factor: which binds to fibrinogen yielding aggregation of the bacteria.
5- Capsular polysaccharide: A few strains of staph. aureus are encapsulated and tend to be more virulent that non capsulated strains.
6- Surface receptors: for specific bacterial phages, permit phage typing for epidemiological purposes.
Antigenic structure
Toxins and Enzymes produced by Staph. aureus
Toxins :
Hemolysin
Leucocidin
Toxic shock syndrome
toxin-1 (TSST-1)
Exfoliative toxin
Enterotoxin
Enzymes :
Coagulase enzyme
Staphylokinase
Hyaluronidase
B- lactamase
(penicillinase )
DNAase
25
Diseases produced by Staph. aureus
Pyogenic infection (enzymes)DisseminatedFocal
Toxin mediated: Food poisoning .Toxic shock syndrome .Scalded skin syndrome.
Staphylococcal Disease
27
Range from localized to systemicLocalized cutaneous infections – invade skin
through wounds, follicles, or glandsfolliculitis – superficial inflammation of hair follicle;
usually resolved with no complications but can progress
furuncle – boil; inflammation of hair follicle or sebaceous gland progresses into abscess or pustule
carbuncle – larger and deeper lesion created by aggregation and interconnection of a cluster of furuncles
impetigo – bubble-like swellings that can break and peel away; most common in newborns
28
Nonbullous Lesions of Impetigo
Figure 21.4
Staphylococcal Disease
30
Systemic infections osteomyelitis – infection is established in
the metaphysis; abscess formsbacteremia - primary origin is bacteria
from another infected site or medical devices; endocarditis possible
31
Figure 23.4
Bacterial Endocarditis
Staphylococcal Disease
33
Toxigenic disease food intoxication – ingestion of heat stable
enterotoxins; gastrointestinal distressstaphylococcal scalded skin syndrome –
toxin induces bright red flush, blisters, then desquamation of the epidermis
toxic shock syndrome – toxemia leading to shock and organ failure
Lesions of Skin Syndrome
Figure 21.5
35
Staphylococcal Food Poisoning
Pathogen Staphylococcus aureusSymptoms Nausea, vomiting, and
diarrhea
Intoxication/Infection IntoxicationEnterotoxin (superantigen)
Diagnosis Phage typingTreatment None
Events in Staphylococcal Food Poisoning
Figure 25.6
Importance in hospital infection:· Carriage of staph. by medical personnel→hospital
infection (nosocomial infection of patients) or food poisoning.
Carriage in : Nose.§Hands.
Tracing the source of infection = (epidemiological study of the isolated strains)phage typing. Detection of carriers nasal or skin swabblood agar. staph (identification).
Carriers of Staph. aureus
40
Phage typing
Figure 10.13
Phage Typing
Methicillin-resistant Staph.aureus (MRSA)
Resistant to all beta lactam antibiotics. resistant to other drugs (aminoglycosides).
sensitive to vancomycin.
Other Staphylococci
45
Coagulase-negative staphylococcus; frequently involved in nosocomial and opportunistic infections
S. epidermidis – lives on skin and mucous membranes; endocarditis, bacteremia, UTI
S. saprophyticus – infrequently lives on skin, intestine, vagina; UTI
Coagulase-Negative Staphylococci
Staphylococcus epidermidis
S. saprophyticus
Novobiocin testStaph epidermidis ---S Staph saprophytics ---R
Staph. saprophytics:urinary tract infections in
young females
Staphylococcal Biofilms
Figure 21.3