gram (-) bacteria Flashcards
48 hr history with yellowish penile discharge, sexual acticity
1) gonorrhea
2) gram stain
- gram (-) pink
20 year old male, 12 hour history of fever, chillss, and severe headache. purpuric skin lesions
1) sign of meningitis
2) BP - 71/54 (LOW)
2) neck stiffness and purpuric rashes
gonococcus
1) G (-) non-capsulated
2) usually colonize urogenital tract, pharynx, rectum
gonococcus virulence factors
virulence factors
– Pilus*: attachment
*The term pilus and fimbria can be used
interchangeably.
– Opacity protein (Opa): attachment
– Lipooligosaccharide (LOS)
– Porin proteins (Inhibition of complement
activation)
– Thermonuclease
– IgA proteases (good for degrading it and making it inactive on mucosal surfaces)
– β-lactamase (penicillin binding protein)
host-pathogen interaction of nisseria gonorrheoeae
1) Bacterial attachment to the host cell. (pili and opa protein)
2) Bacterial proliferation.
3) Translocation to the cytoplasm,
- Release of cytokines and chemokines by macrophages /
dendritic cells (DCs) in response to PAMPs (LOS)
- Attraction of neutrophils (at the site of infection) in
response to chemokine (IL-8). Bacterial killing by
neutrophils by:
a) Phagocytic
b) Non-phagocytic: Neutrophil Extracellular Trap
(NET) (thermonuclease)
- Complement activation (LOS and porin protein)
- Antigen recognition by DCs, migration to lymph nodes,
activate adaptive immunity (antigen presentation to naïve
T cells)
PRRs
1) athogen-associated-molecular patterns (PAMPs)
Lipopolysaccharide (LPS) (P. gingivalis, A. actinomycetemcomitans)
Flaggellin (T. denticola), etc
- L. gonorrhoeae: TLR4
Neisseria gonorrhoeae causes
Causes gonorrhea, only occurs in humans
(N. gonorrhoeae is human-specific pathogen)
– Sexually transmitted disease (STD)
a) Increased risk of infection with
increasing sexual encounters
– Most cases in the United States occur
among young people ages 15-24 years
a) Cases have declined over the past
decades
gonorrhea in men and women
Gonorrhea in men
Ø Inflammation causes painful urination and pus-
filled discharge
* Gonorrhea in women
Ø Often asymptomatic
Ø Can trigger pelvic inflammatory disease
* Infections can occur outside the reproductive tract (by
oral-genital contact)
Ø Cause pharyngitis, and gingivitis
* Infection of the cornea of newborns can occur during
childbirth (via infected mother
diagnosis gonorrhoeae
1) Diagnosis
– Asymptomatic cases identified with genetic
probes
– Culturing bacteria on selective media (Thayer
Martin medium)
– Gram-negative diplococci in pus from inflamed
penis
gonorrhoeae treatment
1) 3rd generation cephalosporins
2) azithromycin or doxycycline is often included
neisseria meningitidis
The Meningococcus: Neisseria meningitidis
* G(-), capsulated (anti-phagocytic) diplococci
* Most common cause of meningitis in individuals
under 20 years of age.
* Bacteria transmitted by respiratory droplets
among people living in close contact.
- Colonization: nasopharynx and upper
respiratory tract
- Usually asymptomatic
* The organisms can enter the blood stream and:
- spread to specific sites (such as meninges to
cause meningitis, peaks in the late winter
and early spring)
or
Øbe disseminated throughout the body
(meningococcemia)
meningitidis characteristics
Bacterial Characteristics
* Virulence factors
- Capsule
- Pili: attachment
- Lipooligosaccharide (LOS)
- IgA proteases
* Serogroups
- Polysaccharide capsule (at least 14 types) is highly
antigenic
- 90% of meningococcal disease are caused by serogroups
A, B, C.
* Culture
- Blood and CSF culture requires lysed blood agar
(chocolate, right pic) or sheep blood agar media (left pic).
- Fermentation of maltose (not seen in Gonococcus)
meningitidis
1) Meningococcal colonization of nasopharynx (pili-
mediated) that is enhanced by IgA protease.
2) Entry to the submucosa and blood stream (bacteria
escape from phagocytosis: capsule)
3) CNS invasion (by unknown mechanism)
4) CNS injury due to inflammatory response. LOS (-
associated endotoxin) triggers the release of
proinflammatory cytokines (e.g, TNF and IL-1)
meningitis symptoms
Sepsis as a consequence of
bacteremia
* Disseminated infection
characterized by:
– Thrombosis of small blood
vessels
– Fever, vomiting, headache,
myalgia
– Purpuric cutaneous lesion
– Reduced cardiac output
(hypotension due to pro-inflammatory cytokines)
meningitis diagnosis and prevention
Diagnosis
– Rapid diagnosis critical
– Spinal tap (CSF) , culture and Gram stain (meningitis)
– Blood culture (for meningococcemia)
* Treatment
– Immediate administration of intravenous 3rd generation (ASAP)
cephalosporin
* Prevention
– Vaccine against some meningococcal strains is available
