This document summarizes characteristics and pathogenic mechanisms of Neisseria gonorrhoeae, Neisseria meningitidis, Treponema pallidum, and Haemophilus influenzae. Key points include: N. gonorrhoeae causes gonorrhea and ophthalmia neonatorum through attachment to mucosal surfaces. N. meningitidis can cause meningitis by crossing the blood-brain barrier. T. pallidum spreads via lymph and blood to cause primary and secondary syphilis lesions. H. influenzae is a respiratory pathogen that can cause meningitis, especially in young children.

1. Niesseria, Treponema,
Haemophilus
Aman Ullah

2. Neisseria species
Common characteristics
• Gram-negative
• Kidney bean–shaped diplococci
• Piliated
• Oxidase-positive
• Aerobic

3. Niesseria gonorrhoeae

4. Pathogenesis/Clinical Significance
• The normal habitat of N. gonorrhoeae is the human
genital tract
• It is usually transmitted during sexual contact, but can
also be transmitted during the passage of a baby
through an infected birth canal
• Bacterial proteins (pili and outer membrane proteins)
enhance the attachment of the bacterium to host
epithelial and mucosal cell surfaces, such as those of
the urethra, rectum, cervix, pharynx, and conjunctiva,
followed by colonization
• IgA protease allows gonococci to evade mucosal IgA

5. Pathogenesis/Clinical Significance
Gonorrhea
• In males, symptoms include urethritis, purulent discharge, and pain
during urination
• In females, infection is usually localized to the endocervix,
sometimes causing a purulent vaginal discharge.
• If the woman's disease progresses to the fallopian tubes,
gonococcal salpingitis (which may lead to infertility), pelvic
inflammatory disease.
• Alternatively, the infection may be asymptomatic
Ophthalmia neonatorum
• This is a purulent conjunctivitis acquired by a newborn during
passage through the birth canal of a mother infected with the
gonococcus.
• If untreated, acute conjunctivitis can lead to blindness

6. Lab diagnosis
• Gram-negative diplococci are visible within
neutrophils in urethral exudates
• Sample for C/S

7. Neisseria meningitidis

8. Pathogenesis/Clinical Significance
• N. meningitidis is one of the most frequent causes of
meningitis
• Trans - mission is via respiratory droplets
• Pili allow the attachment of N. meningitidis to the
nasopharyngeal mucosa
• The meningococcal polysaccharide capsule is
antiphagocytic, and is, therefore, the most important
virulence factor aiding in maintenance of the infection
• N. meningitidis also makes IgA protease
• Endotoxin called LOS is responsible for most of the
tissue damage in meningococcal disease

9. Pathogenesis/Clinical Significance
Meningitis
• The epithelial lining of the nasopharynx normally serves as a barrier
to bacteria
• If meningococci penetrate that barrier and enter the blood stream
they rapidly multiply, causing meningococcemia
• This septicemia can result in intravascular coagulation, circulatory
collapse, and potentially fatal shock (for which the bacterial
endotoxin is largely responsible)
• If N. meningitidis crosses the blood–brain barrier, it can infect the
meninges, causing an acute inflammatory response that results in a
purulent meningitis
• The initial fever and malaise can rapidly evolve into severe
headache, rigid neck, vomiting
• Coma can occur within a few hours

10. Lab diagnosis
• Specimen: Blood and CSF
• Sample for C/S
• CSF for Gram stain

11. Treponema pallidum
Common characteristics
• Gram-negative but stain poorly and need to be
visualized by other means
• Long, flexible, spiral- or corkscrew-shaped rods
• Highly motile
• Does not grow in culture

12. Pathogenesis/Clinical Significance
• T. pallidum is a human parasite, transmitted
primarily by sexual contact
• The infectious lesion is generally on the skin or
mucous membranes of the genitalia
• T. pallidum secretes the enzyme hyaluronidase,
which disrupts the ground substance, thereby
facilitating the spread of infection.

13. Pathogenesis/Clinical Significance
Syphilis
• T. pallidum multiplies at the site of initial infection, and spreads via the
lymph to the blood
• Within 2 to 10 weeks, a hard, painless ulcer (chancre) forms
• Up to 10 weeks later, secondary lesions appear. These consist of a red
maculopapular rash, seen primarily on the palms and soles, and pale,
moist papules, seen primarily in the anogenital region (where they are
called condylomas), the armpits, and the mouth
• Both primary and secondary lesions are rich in T. pallidum organisms, and
are extremely infectious, but both heal spontaneously
• Secondary lesions may be accompanied by systemic involvement, such as
syphilitic hepatitis, meningitis, nephritis.
• In untreated individuals, the disease progresses to a tertiary stage,
characterized by degenerative changes in the nervous system,
cardiovascular lesions, and/or development of granulomatous lesions
(gummas) in the liver, skin, and bones

14. Pathogenesis/Clinical Significance
Congenital syphilis
• A pregnant woman with syphilis can transmit T.
pallidum through the placenta to her fetus after
the first 10 to 15 weeks of pregnancy
• Infection can cause death and spontaneous
abortion of the fetus
• Those infants that live develop the symptoms of
congenital syphilis, including a variety of central
nervous system and structural abnormalities

15. Lab diagnosis
• The infection is diagnose serologically b/c it
cannot be seen by Gram stain and has not
been cultured in-vitro

16. Haemophilus influenzae
Common characteristics
• Gram-negative
• Pleomorphic in shape, ranging from small
coccobacilli to long, slender filaments
• Culture on chocolate agar containing hemin
and NAD

17. Pathogenesis/Clinical Significance
• H. influenzae is a normal resident of the human upper
respiratory tract, and may also colonize the conjunctiva and
genital tract
• Transmission is by respiratory droplets
• H. influenzae may be unencapsulated, or may produce a
capsule (capsular type b is associated with the most
serious, invasive disease)
• After attaching to and colonizing the respiratory mucosa,
the infection can become systemic, with bacteria spreading
via the blood to the central nervous system.
Bacterial meningitis
• H. influenzae can cause bacterial meningitis, especially in
infants and very young children

18. Pathogenesis/Clinical Significance
Upper respiratory tract infections
• H. influenzae is a major cause of otitis media,
sinusitis, and epiglottitis, primarily in children
Pneumonia
• This organism causes pneumonia, particularly in
older adults or immunocompromised individuals
• Lab diagnosis
• Specimen depend on the site of infection
• Sample for C/S