T he N eisseria Dr. Ali - PowerPoint Presentation

Slide1

The Neisseria

Dr. Ali Abdulwahid

University of

Mustanisiriya

College of Medicine

Third stage

Slide2

The Neisseria

Gram-negative cocci, usually occur in pairs to form (diplococci)

The two medically important species are

Neisseria

gonorrhoeae

(gonococci)

Neisseria

meningitidis

(

meningococci

)

Some other species are members of normal human respiratory tract

microbiota

, and either rarely or never cause disease

Slide3

The typical Neisseria

A Gram-negative, non motile kidney shaped diplococcus,The bacterial cells are about 0.8

μm

in diameter.

Culture features

On enriched media (e.g. chocolate agar) , after 48 hours of incubation, the organisms can form convex, glistening, elevated,

mucoid

colonies

Their size can be

1–5 mm in diameter.

non

pigmented

and can be transparent or opaque,

non hemolytic.

Slide4

Growth Characteristics

The Organisms grow best under aerobic conditionsOxidize carbohydrates

, producing acid but not gas

Meningococci

and gonococci are

fastidious,

growing on media that containing complex organic substances such as heated blood,

hemin

, and animal proteins

It requires an atmosphere containing 5% CO2.

They are sensitive to the desiccation, moist heat, sunlight, and many different disinfectants .

Slide5

Kovac’s

oxidase test

The oxidase test is a key test for identifying them. It

determines the presence of

cytochrome oxidase

.

When bacteria are treated with

Kovac’s

reagent

(tetramethylparaphenylenediamine hydrochloride) the Neisseria rapidly turn into dark purple.

Kovac’s

oxidase test: on filter paper .

Adapted from:

https://www.cdc.gov/meningitis/lab-manual/chpt07-id-characterization-nm.html

Slide6

Neisseria gonorrhoeae

Gram- negative, kidney shaped diplococci

Their natural reservoir is human (genital tract)

Utilize (oxidase) only glucose (not maltose as in

meningococci

)

Gonococci isolated from clinical specimens or maintained by selective subculture have typical

small colonies containing

piliated

bacteria. On nonselective subculture, larger colonies containing non piliated gonococci are also formed.

Slide7

Pathogenesis

Transmission :Sexual contact

Birth (infection of newborns during passage through an infected birth canal)

Slide8

Important Virulence factors

Pili

:

The hair-like appendages extends from the

gonococcal

cell surface

They enhance attachment to host cells and resistance to phagocytosis

Outer membrane proteins A- Por proteins extends through the

gonococcal cell membraneAffect the intracellular killing of gonococci within neutrophils by preventing phagosome–lysosome fusion. Confers resistance of gonococci to the bactericidal activity of normal human serum via binding to C3b and C4b proteins of human complement system.

Slide9

Opa

proteins

: mediate adhesion of gonococci to host cell receptors.

Rmp

(Protein iii

) This protein associates with

Por

in the formation of pores in the cell surface.

IgA1 protease

: inactivates IgA1 antibodies, which are the main mucosal antibody of humans.Lipooligosaccharide (endotoxin)

It differs from lipopolysaccharide (LPS) of other Gram-negative bacteria as it lack the long O-antigen side chains and so called lipooligosaccharide (LOS).Their endotoxic effects are responsible for the toxicity in gonococcal infections

Slide10

Diseases

Gonococci can attack the mucous membranes of different sites of the body including : the genitourinary tract, eye, rectum, and throat

,

resulting in acute suppuration that may lead to tissue invasion; followed by chronic inflammation and fibrosis.

Men

usually have urethritis, with yellow, creamy pus and painful urination.

Urethral infection in men can be asymptomatic

Slide11

In women:

The primary infection is in the endocervix which then extends to the urethra and vagina, leading to

mucopurulent

discharge

.

It may then progress to the uterine tubes, causing

salpingitis

,

fibrosis

, and obliteration of the tubes. Infertility occurs in 20% of women with gonococcal salpingitis.Chronic gonococcal cervicitis and proctitis are often asymptomatic.

Slide12

2-

Gonococcal bacteremia

leads to skin lesions on the hands, forearms, feet, and legs

3-

Gonococcal

ophthalmia

neonatorum

It is an infection of the eye in newborns, acquired during passage through an infected birth canal. The progress of the initial infection is very rapid and can result in blindness if untreated

Slide13

A

newborn

with

gonococcal

ophthalmia

neonatorum

caused by a maternally transmitted

gonococcal

infectionAdapted from

Centers

for Disease Control and Prevention

,

Public Health Image Library

 (PHIL) , identification number 

#3766

.

Slide14

Diagnosis

A. SpecimensPus and secretions are taken from the urethra, cervix, rectum, conjunctiva, throat, or synovial fluid for culture and smear.

Blood culture is necessary in systemic illness

B. Smears

Gram-stained smears of urethral or

endocervical

exudates reveal many

diplococci

within pus cells.

Slide15

Gram-stain of

gonococcal

urethritis. The bacteria can be seen intracellular and extracellular.

Adapted from

Centers

for Disease Control and Prevention

,

Public Health Image Library

 (PHIL), identification number 

#4085

.

Slide16

C. Culturepus or mucus specimens can be streaked immediately after collection on enriched or selective medium (

eg

, Chocolate agar, Thayer-Martin and modified Thayer-Martin medium [MTM])

and incubated at 37°C in 5% CO2 ,.

After 48 hours of incubation , the growing organisms can be identified by

Gram-stained smear

; by

oxidase test

; by coagglutination, immunofluorescence staining and any further laboratory tests.

Slide17

Growth of

Neisseria

gonorrhoeae

on different microbiologic culture media.

Adapted from

Centers

for Disease Control and Prevention

,

Public Health Image Library

. Image credit: CDC/Renelle Woodall (PHIL #6505), 1969

Slide18

Neisseria

gonorrhoeae

oxidase positive test at plate and with swap.

Adapted from

https://www.cdc.gov/std/gonorrhea/lab/ngon.htm

Slide19

Nucleic Acid Amplification Tests

Provides direct detection of N gonorrhoeae in genitourinary specimens

Advantages

: better detection, more rapid results, and the ability to use

urine

as a specimen source.

Slide20

Treatment

Because of the problems with antimicrobial resistance in N gonorrhoeae,

Uncomplicated infections

ceftriaxone

(250 mg) given intramuscularly as a single dose

Oral

cefixime

(400 mg ) as a single dose.

Possible concomitant chlamydial infections

1 g of azithromycin orally in a single dose or 100 mg of doxycycline orally twice a day for 7 days

Slide21

Prevention

The infection rate can be reduced by The early diagnosis and the treatment, which can eradicate the gonococcal infection rapidly

avoiding multiple Sexual partners,

Mechanical prophylaxis

(condoms) provides partial protection.

Chemoprophylaxis

: is with limited effects due to the increasing antibiotic resistance of the gonococci.

Gonococcal

ophthalmia neonatorum this infection can be prevented by local application of 0.5% erythromycin ophthalmic ointment or 1% tetracycline ointment to the conjunctiva of newborns

Slide22

Neisseria meningitidis

Differential featuresGram-negative diplococcucci

Obligate commensal to humans

The

nasopharynx

is the portal of entry

Grouped into 13

serogroups

depending on the structure and immunogenicity of their capsular polysaccharides.

The serogroups that associated with disease in humans are A, B, C, X, Y, and W-135.The bacteria utilize the maltose ( in contrast to gonococci)

Slide23

Pathogenesis

Transmission:bacteria can colonize around 5-10 % of healthy individual asymptomatically The bacteria transmit from one person to another via respiratory droplets,

After colonizing the

nasopharynx

, it can reach the blood stream and then spread to the meninges

A small rate of healthy carriers can develop diseases

Slide24

Important virulence factors

Pili and outer membrane proteins (Opa and

Opc

) play the key role in colonization process as

adhesins

Capsular polysaccharide

:

antiphagosytic

confers resistance to serum bactericidal activityIgA protease : inhibit IgA activity and promoteLipooligosaccaride (endotoxine): Responsible for the endotoxin activity of the meningococcal infection causing fever, septic shock in the systemic infection

Slide25

Diseases:

The nasopharynx is the portal of entry. The bacteria colonize the

halthy

individual as a transient flora without causing disease

(carriage state).

In few cases , the bacteria can reach the bloodstream, disseminated and producing bacteremia

Fulminant meningococcemia

is severe, with a high fever and a hemorrhagic rash

Waterhouse-

Friderichsen syndrome, when the patient have disseminated intravascular coagulation and circulatory collapseMeningococcal meningitis is the most common complication of meningococcemia.

Slide26

Diagnosis

A. SpecimensSpecimens of blood are taken for cultureSpecimens of spinal fluid are taken for smear, culture, and chemical determinations.

Nasopharyngeal swab cultures are suitable for carrier surveys.

Puncture material from

petechiae

may be taken for smear and culture.

B. Smears

Gram-stained smears of the sediment of centrifuged spinal fluid or of petechial aspirate often show typical

neisseriae

within polymorphonuclear leukocytes or extracellularly.

Slide27

C. Culture

Blood and Cerebrospinal fluid specimens are plated on agar culture mediaA modified MTM with antibiotics (selective media ) is used for nasopharyngeal cultures

The grown colonies of

neisseriae

on solid media can be identified by

Gram stain

and the

oxidase test

Spinal fluid and blood generally yield pure cultures that can be further identified by

carbohydrate oxidative reactions and agglutination

Slide28

Proper streaking and growth of 

N.

meningitidis

 on a Blood Agar plate

Gram stain of 

N.

meningitidis

 in CSF with associated PMNs.

Pictures were adapted from:

https://www.cdc.gov/meningitis/lab-manual/chpt06-culture-id.html

 

N.

meningitidis

 with utilization of glucose (dextrose) and maltose, indicated by acid production (

color

change to yellow), and no utilization of lactose or sucrose

https://www.cdc.gov/meningitis/lab-manual/chpt07-id-characterization-nm.html

Slide29

D. Serology

Antibodies against the capsular polysaccharides can be used as a detection testTheir positivity can be detected by latex agglutination or hemagglutination

tests or by their bactericidal activity.

Polymerase Chain Reaction (PCR):

using primers targeting specific meningococcal genes , providing rapid and sensitive detection

Slide30

Treatment

TreatmentPenicillin G In persons who are allergic for penicillins

chloramphenicol or a third generation cephalosporin (

cefotaxime

or ceftriaxone) can be used as alternatives

Slide31

Prevention

Vaccination Capsular polysaccharides vaccines are available for groups A, C, Y, and W-135Tetravalent conjugate vaccines such as

Menveo

, contain capsular polysaccharides of group A, C, Y, W135 conjugated to diphtheria toxoid.

Bexero

(protein based vaccine) provide protection against group B

maningococci

chemoprophylaxis

Rifampin or ciprofloxacin can be sued for decrease and eradicate the carrier rate and serve as chemoprophylaxis for people who are with close contact with the patients (such as household)

Slide32

References

Reidle, S., Morse, S. A., Meitzner, T., and Miller, S. 2019.

Jawetz

,

Melnick

&

Adelberg’s

Medical Microbiology , Twenty-Eight Edition. The McGraw-Hill education, Inc. USA

Centers

for Disease Control and Prevention: Laboratory Methods for the Diagnosis of Meningitis. Chapter 6: Primary Culture and Presumptive Identification of Neisseria meningitidis, Streptococcus pneumoniae, and Haemophilus influenza Retrieved from https://www.cdc.gov/meningitis/lab-manual/chpt06-culture-id.html

Centers for Disease Control and Prevention: Laboratory Methods for the Diagnosis of Meningitis. Chapter 7: Identification and Characterization of Neisseria meningitides Retrieved from https://www.cdc.gov/meningitis/lab-manual/chpt07-id-characterization-nm.html

Centers

for Disease Control and Prevention:

Gonorrhea

Laboratory Information

Characteristics of 

N.

gonorrhoeae

 and Related Species of Human Origin. Retrieved from

https://www.cdc.gov/std/gonorrhea/lab/ngon.htm

Centers

for Disease Control and Prevention

Public Health Image Library

 (PHIL).

Slide33

Thank you