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Gram Positive & Gram Negative
Cocci Infections
(Staphylococcus,
Streptococcus, Neisseria)
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• 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.
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Staphylococcus aureus (Gram stain)
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Staphylococcus aureus (BAP)
(Golen pigmen)
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Staphylococcus aureus
!annitol Salt Agar
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Catalase test
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Coagulase test
(slie)
Coagulase test
(tu"e)
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• !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.
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Streptococcus pyogenes
(Gram stain)#rom "roth culture
Streptococcus pneumoniae
(Gram stain)
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$ (partial)
hemolysis
% (total) hemolysis
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ptochin test Bacitracin test
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CA!P test
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• *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.
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Neisseria gonorrhoeae
(Gram stain)
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Canle 'ar
Neisseria gonorrhoeae
(hayer !artin meium)
iase (*)
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• "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.
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$ otentially fatal systemic infections
caused by "taphylococcus include toic
shock syndrome %T""), bacteremia,
endocarditis, pneumonia, empyema, and
osteomyelitis.
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• "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.
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$ 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.
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$ 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.
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• *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.
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$ 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.
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TH0*: ;85 8! ;85!
0TT2*T48*
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