1.Gram Positive & Gram Negative Cocci Infections

8/19/2019 1.Gram Positive & Gram Negative Cocci Infections

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Gram Positive & Gram Negative

Cocci Infections

(Staphylococcus,

Streptococcus, Neisseria)



• Gram-positive cocci especiallyStaphylococcus spp. are living andreproducing on almost every square

inch of our skin. They are members ofevery human’s microbiota, and usuallyunnoticed. Hoever, they can bepathogen, causing minor to life-threatening diseases.



Staphylococcus aureus (Gram stain)



Staphylococcus aureus (BAP)

(Golen pigmen)



Staphylococcus aureus

!annitol Salt Agar



Catalase test



Coagulase test

(slie)

Coagulase test

(tu"e)



• !eseachers differentiate species of"treptococci using several differentoverlapping schemes, including# $ serological based on the reactions of

antibodies to specific bacterial antigens,

$ type of hemolysis %&, ', or (-hemolysis),

$ cell arrangement, and

$ physiological properties as revealed bybiochemical tests.



Streptococcus pyogenes

(Gram stain)#rom "roth culture

Streptococcus pneumoniae

(Gram stain)



$ (partial)

hemolysis

% (total) hemolysis



ptochin test Bacitracin test



CA!P test



• *eisseria is the only genus of Gram

negative cocci that cause diseases in

humans. The cells of these bacteria are

nonmotile and typically arranged as

diplococci %pairs) ith their common sides

flattened like coffee beans.



Neisseria gonorrhoeae

(Gram stain)



Canle 'ar

Neisseria gonorrhoeae

(hayer !artin meium)

iase (*)



• "taphylococcus#

$ S. aureus and S. epidermidis are found on theskin and in upper respiratory, gastrointestinal,and urogenital tracts. S. aureus is the morevirulent, partly because of its production of

various en+ymes such as coagulase andstaphylokinase, and several toins.

$ ood poisoning is a noninvasive diseasecaused by "taphylococcus. "kin diseases

caused by this bacteria include scalded skinsyndrome, impetigo, folliculitis, furuncles, andcarbuncles.



$ otentially fatal systemic infections

caused by "taphylococcus include toic

shock syndrome %T""), bacteremia,

endocarditis, pneumonia, empyema, and

osteomyelitis.



• "treptococcus

$ /ells of group 0 streptococcus %S. pyogenes)

produce protein 1 and hyaluronic acid

capsule, each of hich contributes to the

virulence of the species. 2n+ymes and toins

produced by S. pyogenes dissolve bloodclots, stimulate fever, and lyse blood cells.

$ The diseases caused by S. pyogenes include

streptococcal sore throat, scarlet fever,

pyoderma, erysipelas, streptococcal T"",necroti+ing fasciitis, rheumatic fever, and

glomerulonephritis.



$ Group 3 streptococci %S. agalactiae) are

normal flora of loer gastrointestinal and

urogenital tracts. They are associated ithneonatal infections and usually are sensitive

to penicillin.

$ The viridans group of &-hemolytic streptococci

include members that inhabit mouth, pharyn,

G4 tract, 5G tract6 cause dental caries, and

can enter the blood and cause bacteremia,

meningitis, and endocarditis. $ 2nterococci are normal flora of the intestines,

that can cause nosocomial infections.



$ 7irulent strains of S. pneumoniae are

protected by polysaccharide capsules. The

bacteria secrete protein adhesion, secretory4g0 protease and pneumolysin hich lyses

cells of the lungs. neumonia is the most

prevalent disease caused by S. pneumoniae.

"ymptoms are fever, breathing difficulty, chestpain and rusty-colored sputum. The bacteria

can be identified by the production of &

hemolysin, inhibition of groth by optochin,

bile salt solubility, and serological reaction%quellung). 8ther diseases include sinusitis,

otitis media, bacteremia, endocarditis, and

meningitis.



• *eisseria*eisseria is a pathogenic Gram negative

coccus6 its virulence results from the

presence of fimbriae, polysaccharidecapsules, and lipooligosaccharide

containing lipid 0 in its cell all.



$ Neisseria gonorrhoeae causes gonorrhea, a

seually transmitted disease %"T9) ofhumans. 4n men it results in acuteinflammation of the urethra, hereas inomen it is generally asymptomatic. 4t caninfect the uterus and uterine tubes to causepelvic inflammatory disease %49).

$ Neisseria meningitidis causes a type ofmeningitis6 it is transmitted on respiratorydroplets and is life-threatening hen it entersthe bloodstream or central nervous system.



TH0*: ;85 8! ;85!

0TT2*T48*

1.Gram Positive & Gram Negative Cocci Infections

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