Gram-Negative Cocci

Question 1

TALK ABOUT NEISERRIA

Answer 1

it is a gram negative cocci , it is facilitative intracellular
Neisseria is non- spore-forming, capable of moving using twitching motility, and
an obligate aerobe (requires oxygen to grow)

it has two main human pathogens: Neisseria meningitidis and Neisseria gonorrhoeae.
• N. gonorrhoeae is the causative agent of gonorrhea and N. meningitidis is one
cause of bacterial meningitis

Question 2

what are the important properties for Neisseria

Answer 2

Neisseria meningitidis (meningococcus) has a prominent
polysaccharide capsule with antiphagocytic action. The capsule also is
the immunogen in the vaccine that induces protective antibodies.

 Neisseria gonorrhoeae (gonococcus) has no polysaccharide capsule but
has multiple serotypes based on the antigenicity of its pilus protein.

Question 3

what does the endotoxin of Neisseria consists of

Answer 3

The endotoxin of Neisseria consists of lipooligosaccharide (LOS), in
contrast to the lipopolysaccharide (LPS) found in enteric gram-negative
rods. Both LPS and LOS contain lipid A, but the oligosaccharide part of LOS
contains few sugars, whereas the polysaccharide part of LPS contains a
long repeating sugar side chain

Question 4

how can I differentiate Neisseria from other cells ?

Answer 4

• Neisseriae are oxidase-positive
( The purple color indicates a positive test )

colonies exposed to phenylenediamine turn purple or black as a result of oxidation

Question 5

talk about Neisseria meningitidis

Pathogenesis & Epidemiology

Answer 5

it is a gram-negative cocci that cause bacterial meningitis
It is transmitted by airborne droplets that colonize in the nasopharynx and become a part of the normal flora of the Upper respiratory tract, from there the organism can enter the bloodstream and to meningis cause meningitis

Question 6

what are the Two organisms cause more than 80% of cases of bacterial meningitis in infants older than 2 months of age

Answer 6

Streptococcus pneumoniae and N. meningitidis.

Question 7

Meningococci have four main virulence factors mention them

Answer 7

(1) A polysaccharide capsule
(2) Endotoxin, which causes fever
(3) An immunoglobulin A (IgA) protease
(4) Factor H binding protein (FHBP)

Question 8

what is Waterhouse–Friderichsen

syndrome

Answer 8

The most severe form of meningococcemia
is characterized by high fever, shock, widespread purpura,
The symptoms are fever, headache, stiff neck, and
an increased level of polymorphonuclear leukocytes (PMNs) in the
spinal fluid

Question 9

what is the difference between N. meningitidis and N. gonorrhoeae

Answer 9

The differentiation between N. meningitidis and N. gonorrhoeae is made
on the basis of sugar fermentation: meningococci ferment maltose,
whereas gonococci do not (both organisms ferment glucose)

Question 10

laboratory diagnosis for N. meningitidis

Answer 10

The principal laboratory procedures are smear and culture of blood and
spinal fluid samples

The organism grows best on chocolate agar incubated at 37°C in a 5% CO2
atmosphere

Question 11

treatment and prevention of N. meningitidis

Answer 11

penicillin G

The vaccines against groups A, C, Y, and W-135 meningococci are conjugate vaccines, that is, the capsular polysaccharide is conjugated to a carrier protein.

Question 12

talk about Neisseria gonorrhoeae

Answer 12

it is a gram negative cocci
It is oxidase positive and aerobic, and it survives phagocytosis and
grows inside neutrophils
• Pili are the main virulence factors,
• Two virulence factors in the cell wall are endotoxin
(lipooligosaccharide, LOS) and the outer membrane proteins.
• The organism’s IgA protease can hydrolyze secretory IgA, which
could otherwise block attachment to the mucosa.
• Gonococci have no capsules.

Question 13

what are the pathogenesis of N .gonohreaa

Answer 13

The main host defenses against gonococci are antibodies (IgA and
IgG), complement, and neutrophils

Question 14

what are the Clinical Findings for Gonococci

Answer 14

• Gonococci, like meningococci, cause disease only in humans. N. gonorrhoeae can cause infection of the genitals, throat, and eyes. The organism is usually transmitted sexually

Gonococci cause both localized infections, usually in the genital tract, and disseminated infections with seeding of various organs. Gonococci reach these organs via the bloodstream (gonococcal bacteremia)

Question 15

Laboratory Diagnosis FOR Neisseria gonorrhoeae

Answer 15

• Nucleic acid amplification tests (NAAT),

N. gonorrhoeae is oxidase positive (possessing cytochrome c oxidase) and catalase positive (able to convert hydrogen peroxide to oxygen)

Question 16

treatment and prevention for Neisseria gonorrhoeae

Answer 16

Ceftriaxone is the treatment of choice

The prevention of gonorrhea involves the safe sex and the prompt
treatment of symptomatic patients and their sex partners

Question 17

TALK ABOUT GENUS CHLAMYDIAE

Answer 17

it is gram negative cocci that is obligate intracellular

Chlamydia trachomatis causes eye, respiratory (pneumonia), and genital tract infections
Chlamydia pneumoniae causes atypical pneumonia.
• Chlamydia psittaci causes psittacosis, also a disease characterized mainly by
pneumonia

They have a rigid cell wall but do not have a typical peptidoglycan layer. Their cell walls resemble those of gram-negative bacteria but lack
muramic acid.

Question 18

Life cycle of Chlamydia.

Answer 18

The extracellular, inert elementary body enters an epithelial cell and changes into a reticulate body that divides many times by binary fission.

The daughter reticulate bodies change into elementary bodies and are released from the epithelial cell.

The cytoplasmic inclusion body, which is characteristic of chlamydial infections, consists of many daughter reticulate and elementary bodies

Question 19

Transmission & Epidemiology of Chlamydia

Answer 19

Chlamydiae infect primarily epithelial cells of the mucous membranes
or the lungs. They rarely cause invasive, disseminated infections

• Chlamydia trachomatis infects only humans and is usually transmitted by close personal contact

Chlamydia pneumoniae infects only humans and is transmitted from
person to person by aerosol. causes upper and lower respiratory tract infections

Chlamydia psittaci infects birds ( Chlamydia psittaci infects the lungs primarily )

Question 20

treatment and prevention

Answer 20

All chlamydiae are susceptible to tetracyclines, such as doxycycline

There is no vaccine against any chlamydial disease.