GRAM +VE COCCI

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

GRAM +VE COCCI

Staphylococcus SPP.

 

 

 

 

 

 

 

·        Cocci.    -Gram +ve

 

·        Catalse +Ve

 

·        arranged in cluster of grapes

 

·        -most staphylococcus Non motile. Non sopre.

 

·        -most staphylococcus facultative anerobic.

 

·        -able to grow in media containing high concentration of salt.

 

·        -at temp from 18C-40C staph bacteria are present on the skin and mucous membrane of human.

 

·        -Opportunistic infections.

 

·        the outer layer of most staphylococcus cell wall covered with (polysaccharide capsule).

 

·        -Eleven capsular serotypes have been identified in S.aureus with serotypes 5 and 7 associated with majority of infection.

 

·        -peptidoglycan can form Half the cell wall of staph.

 

·        protin A can be used as specific identification test for S.aureus( not other Non coagulase staph)

 

·        -There are simple biochemical tests e.g (coagulase, protein A ,

heat- stable nuclease , manitol fermentation) can be used to identify colonies ofS. Aureus and other staph.

 

 

 

 

Staphylococcus aureus
Characteristics	*  cause most Staphylococcal diseases . *  Gr + Ve Cocci . *  Non Sporing , Non Motile Cocci *Usually has capsulate .(polysaccharide)&slim layer. *  Facultative anaerobic .
Habitat	*  Humans ( nose , skin , mucous ) . *  Always present in hospital environment . *  Survives drying . Tolerant of Salts
Transmission	*  Direct contact . *  Airborne route .
Pathogenesis	*Capsule= inhibits chemotaxis and phagocytosis. And facilitates adherence to foreign bodies. *Peptidoglycan= inhibits phagocytosis. *  Hemolysins = lyse RBCs *  Coagulase = converts fibrinogen to fibrin(clots plasma) *catalase= remove of hydrogen peroxide. *  Fibrinolysin = Digest fibrin *  Leucocidin = kills leukocytes *  DNase = hydrolyses DNA *       Protein   A   =    Antiphagocytosis (inhibits  antibody clearance) and anticomplementary. *  Enterotoxin = Vomiting & diarrhea *      TSS toxin-1 = produce leakage or destruction of endothelial cells. *  Exfoliative Toxin = Skin exfoliative
Diseases	*  Superficial infection(scalded skin syndrome) ( SSS ) *  Surgical Wound Infection *  Toxic Shock Syndrome . (( TSS )) *  Toxic Food Poisoning . (( TFP )) *  Septicemia , Endocarditis , pneumonia .
Laboratory Identification	*  White or Golden Colonies on Blood Agar *  Catalase +Ve , Coagulase +Ve , DNase + Ve

 

 

 

 

Staphylococcus epidermidis
Characteristics	*  Rarely cause infections in health people . *  Gr + Ve Cocci . *  Non Sporing , Non Motile Cocci *Opportunistic pathogen. *  Facultative anaerobic . *Slime layer.
Habitat	*  Humans (skin) . *  Always present in hospital environment . *  Survives drying . Tolerant of Salts
Transmission	* Direct contact
Pathogenesis	*  Lower pathogenicity than Staph. Aureus . *    Viscous extracellular slime = Enable the bacteria to adhere to a foreign surface .
Diseases	*  Urinary Tract Infection ( UTI ) *    Prosthetic valve Endocarditis. *Bacteremia. *surgical wounds. *central nervous system infection.
Laboratory Identification	*  White Colonies on Blood Agar *  Catalase +Ve , Coagulase -Ve , DNase - Ve *  Sensitive to Novobiocin disc .

 

 

 

 

Staphylococcus saprophyticus
Characteristics	*  Gr + Ve Cocci . *  Non Sporing , Non Motile Cocci *  Facultative anaerobic .
Habitat	*  Skin *    Genitourinary mucosa .
Transmission	*  Direct contact *  Endogenous spread to urinary tract .
Pathogenesis	*  Virulance factors unknown *    But , this bacteria has ability to colonize periurethral skin & mucosa .
Diseases	* Urinary Tract Infection ( UTI ): opportunistic infection.
Laboratory Identification	*  White Colonies on Blood Agar *  Catalase +Ve , Coagulase -Ve , DNase - Ve *  Resistance to Novobiocin disc .

Streptococcus SPP

 

- Gram +ve cocci

-catalase –ve.

-arranged in pairs or chains.

-most streptococcus facultative anaerobic.

-some grow only in atmosphere enhanced with carbon dioxide(capnophilic growth).

-carbohydrates are fermented, resulting in the production of lactic acid.

- most B-hemolytic streptococcus have group –specific antigen.

-most (but not all) alpha-hemolytic streptococcus and nonhemolytic streptococcus (gamma) do not have the group –specific antigen.

-PYR ( L-pyrrolindonyl-B-arylamidase)

if positive(Streptococcus pyogenes) or negative (Streptococcus anginosus)

 

-ASO tests useful confirming test for rheumatic fever or acute glomerulonephritis caused BY Streptococcus pyogenes.

 

 

 

 

Classification of Common Streptococcal Pathogens

 

Biochemical

Classification            Serologic Classification           Hemolysis Patterns

 

S. pyogenes                                A                                             β

 

S. agalactiae                               B                      β; occasionally nonhemolytic

 

S. dysgalactiae                           C, G                                          β

 

S. anginosus group                   A, C, F, G, nongroupable

β; occasionally α or nonhemolytic

 

S. bovis                                   D                    α; nonhemolytic; occasionally β Viridans group                                  Nongroupable                     α or nonhemolytic

S. pneumoniae

 

Enterococci

Nongroupable D

Α

 

α – β or Gamma

 

 

 

Biochemical Identification of Common Streptococci

 

 

Organism	Susceptibility Bacitracin Optochin	Hippurate hydrolysis	CAMP reaction	Bile solubility
S. pyogenes*	S             R	-	-	-
S. agalactiae	R            R	+	+	-
S. anginosus†	R            R	-	-	-
S. dysgalactiae‡	R            R	-	-	-
S. pneumoniae	R             S	-	-	+
Viridans group	R            R	-	-	-

 

 

S= Sensitive R= Resistant

Streptococcus pyogenes ( Group A , B hemolytic streptococcus )
Characteristics	*  Gr + Ve cocci in chain . *  Non Sporing , Non Motile Cocci . *  Some strains produce a hyaluronic acid capsule . *  Facultative anaerobic . *Growth is optimal on enriched-blood agar media. *inhibited if the medium contain high conc.of glucose. *the basic structural cell wall is peptidoglycan.
Habitat	* Commensal in the throat or skin
Transmission	Direct contact Airborne route
Pathogenesis	·         M Protein = Antiphagocytosis [ Major Virulence Factor ] *T protein= unknown function. *capsule=Antiphagocytosis. ·         Hemolysins = lyse RBCs. ·         Erythrogenic toxins = cause fever & rash in scarlet fever ·         Streptokinase = lyses Blood clot . ·         DNAse = hydrolyses DNA . ·         NADase = Kills Leucocytes .
Diseases	·         Pharyngitis , Tonsilitist , Otitist media . ·         Erysipelae & lampotigo . ·         Scarlet Fever . ·         Rheumatic Fever .(ASO confirming test) ·         Endocarditis .
Laboratory Identification	·         White small colonies on blood agar . ·         Colonies surrounded by Beta Hemolysis. ·         Catalase –Ve ·         Bacitracin Sensitive ·         PYR +Ve.

 

 

Streptococcus agalactiae (( Group B , Beta hemolysis Streptococcus ))
Characteristics	*  Gr + Ve cocci in chain . *  Non Sporing , Non Motile Cocci . *  Facultative anaerobic . *capsule(polysaccharide) *the surface protein (C protein)
Habitat	* Normal Vaginal ( 25% ) & Oral flora .
Transmission	* Direct Contact
Pathogenesis	*  Virulance factors not clearly Identified . *  Capsule is major virulence factor if it is present .=Antiphagocytosis .
Diseases	·         Neonatal Meningitis . ·         Septicaemia ·         Septic abortion . ·         Pneumonia.
Laboratory Identification	·         Colonies on blood agar larger than S.pyogenes . ·         The colonies are buttery a narrow zone of B- hemolytic. ·         Colonies surrounded by Beta Hemolysis. ·         Catalase –Ve ·         Bacitracin Sensitive . ·         CAMP test +Ve ·         Hippurate hydrolysis +Ve.

 

Streptococcus pneumonia (( Alpha Hemolytic Sterptococcus ))
Characteristics	·         Commonest pathogen cause pneumonia . ·         Lancet shape. ·         Gr + Ve Diplococci * Non Sporing , Non Motile Cocci . ·         Ploysaccharide capsule . ·         Facultative anaerobic . ·         Major cell wall structure is peptidoglycan (like all gram-positive cocci). ·         The other major cell wall component is teichoic acid.
Habitat	* Commensal in Human Respiratory Tract .
Transmission	* Droplet spread .
Pathogenesis	* Capsule = Antiphagocytosis .
Diseases	·         Pneumonia . ·         Septicemia .(Bactermia) ·         Meningitis ( Children less than 3 years & adults 45 years and above )) ·         Otitis Media .
Laboratory Identification	·         White small colonies on blood agar . ·         Colonies surrounded by Alpha Hemolysis. ·         Can grow only on enriched media. ·         Can ferment several carbohydrates.(lactic acid) ·         Grow poorly in media with high glucose concentration. ·         Catalase –Ve ·         Optichin Sensitive . ·         Bile solubility Sensitive.

 

 

 

 

Streptococcus viridans (( Alpha Hemolytic Sterptococcus ))
Characteristics	·         Gr + Ve cocci ·         Non Sporing , Non Motile Cocci . ·         Facultative anaerobic . ·         Do not have group-specific.
Habitat	·         Commensal in the human upper respiratory tract . ·         Large Number are found in Oral Cavity . ·         Rarely found in skin because fatty acid in skin are toxic to them
Transmission	·         Droplet Spread .
Pathogenesis	·         Attachment to tooth enamel & gums via various carbohydrates is important in establishment the colonization . ·         Ability to produce acid cause ---} Dental caries .
Diseases	·         Dental caries . ·         Bacterial endocarditis (( Bacteria enter the blood stream as result of dental manipulation and attach to damaged cardic valves . ·         Intraabdominal infections.
Laboratory Identification	·         White small colonies on blood agar . ·         Produce green pigments on blood agar. ·         Colonies surrounded by Alpha Hemolysis. ·         Catalase –Ve . ·         Optichin Resistant .

 

 

 

 

 

COCCI +VE GRAM

 

اﻟﻤﺮﺟﻊ اﻟﺬي ﺗﻢ اﻻﻋﺘﻤﺎد ﻋﻠﯿﮫ

Medical Microbiology

Patrick Murray ﻟﻠﻤﺆﻟﻒ