The presentation provide in depth knowledge about two of the most affecting bacteria to human health. They are Neisseria ( causing gonorrhea and Meningitis) and Shigella ( Diarrhea)

1. Neisseria &
Shigella
Saptarshi Samajdar

2. NEISSERIA
• INTRODUCTION:
 Discovered by Albert Ludwig Neisser (1879) its first example, Neisseria
gonorrheae, the pathogen which causes the human disease gonorrhoea.
 Neisseria is a large genus of bacteria that colonize the mucosal
surfaces of many animals. Of the 11 species that colonize humans, only two
are pathogens, N. meningitidis and N. gonorrhoeae.
 Neisseria species are Gram-negative bacteria included among the
proteobacteria, a large group of Gram-negative forms. Neisseria is
diplococci resemble coffee beans.
 This falls under the family of Neisseriaceae
 Can’t grow in ordinary cultural media, need chocolate agar with 5%
CO2 (capnophilic)

3. Morphological features
• Neisseria gonorrhoeae
o Gram negative
o oval/ spherical cocci
o Usually found within the polymorphs
o arranged in pairs
o kidney shaped
o possesses pilli on their surface
Neisseria meningitidis
o Gram negative
o oval/ spherical cocci
o 0.6-0.8 micron in size
o Arranged in pairs
o Bean shaped
o Encapsulated Neisseria meningitides
Neisseria gonorroeae

4. Symptoms
Gonorrhoea:
Greenish yellow or whitish discharge from the vagina.
Lower abdominal or pelvic pain.
Burning when urinating.
Conjunctivitis (red, itchy eyes)
Bleeding between periods.
Spotting after intercourse.
Swelling of the vulva (vulvitis)
Meningitis:
General poor feeling.
Sudden high fever.
Severe, persistent headache.
Neck stiffness.
Nausea or vomiting.
Discomfort in bright lights

5. Pathogenesis
• N. gonorrhoeae causes gonorrhea, and N. meningitidis is the cause of
meningococcal meningitis. N. gonorrhoeae infections have a high
prevalence and low mortality, whereas N. meningitidis infections have a low
prevalence and high mortality.
• Neisseria gonorrhoeae infections are acquired by sexual contact and usually
affect the mucous membranes of the urethra in males and the endocervix
and urethra in females.
• The lipopolysaccharide of Neisseria meningitidis is highly toxic, an it has an
additional virulence factor in the form of its antiphagocytic capsule. Both
pathogens produce IgA proteases which promote virulence. Many normal
individuals may harbor Neisseria meningitidis in the upper respiratory tract.
It is mainly airbourne moves via droplet infection.. Enters into nasopharyngs
and invade mucosal membrane colonise and enter blood stream . Which
move to meninges and infect.

6. Diagonosis
• Neisseria is traditionally determined using conventional cystine trypticase
agar medium (CTA) containing 1% sugar. This method is based on
fermentative species and is not sensitive enough to detect acid from
oxidative species.
• This method is replaced by rapid carbohydrate test. This test is non growth
dependent method for the detection of acid production from carbohydrates
by Neisseria species.
• Chromogenic enzyme substrate :These tests are based on the presence of
preformed chromogenic enzyme in the culture and, thus, require a heavy
inoculum of the organism grown on selective medium to permit rapid
speciation of isolates. The enzymes that are detected by these systems
include beta-galactosidase, gamma-glutamylaminopeptidase and prolyl-
hydroxyprolyl aminopeptidase. Many of these methods are commercially
available.

7. Commonly used Drugs
Gonorrhoeae is very succeptible to resistance (1st
seen in 1980s) so
common antibiotics like Fluroquinolonones, Penicillins so, used drugs
are:
o Ceftriaxone (Rocephin)
o Azithromycin (Zithromax, Zmax)
o Cefixime (Suprax)
o Doxycycline (Vibramycin, Doxy)
o Erythromycin ophthalmic (Ilotycin Ophthalmic)
For Meningitis, third-generation cephalosporin (ceftriaxone or cefotaxime) is
the drug of choice for the treatment. Penicillin G, ampicillin, chloramphenicol,
fluoroquinolone, and aztreonam are alternatives therapies

8. Recent Developments
• Capsular Polysaccharide Vaccines: polysaccharide vaccines were
introduced against groups W-135 and Y; a meningococcal quadrivalent A,
C, W-135, and Y polysaccharide vaccine, which has been licensed in the
United States. However, these vaccines are poorly immunogenic in children
younger than 2 years of age.
• Polysaccharide–Protein Conjugate Vaccines: To overcome the problem
of short-lived protection against the meningococcus, covalent binding
(conjugation) of polysaccharides to a protein carrier has been used,
resulting in T-cell–dependent immunity and a memory response. United
Kingdom became the first country to introduce the meningococcal group C
polysaccharide–protein conjugate vaccine (MenC) into schedules for routine
infant immunization, with an initial catch-up campaign for children and
adolescents up to 18 years of age. MenC is safe,15 and surveillance in all
age groups has suggested an effectiveness of 95% at 1 year, with
significant waning over a period of 4 years.
• Natural products like garlic and jamun extracts have been helpful against
pathogenic Neisseria.

9. SHIGELLA
INTRODUCTION:
Discovered by Kiyoshi Shiga in 1897
Shigella is a genus of Gram-negative, facultative anaerobic, nonspore-
forming, non motile, rod-shaped bacteria genetically closely related to E. coli.
Shigella is one of the leading bacterial causes of diarrhea worldwide, causing
an estimated 80-165 million cases.
The bacteria is bile salt resistant : This trait is used for selective media
preparation
Can be classified into 4 serogroups:
S. dysenteriae (causes most serious form of bacillary dysentery)
S. flexineri ( causes shigellosis in underdeveloped countries)
S. boydii ( causes shigellosis in developed countries)
S. sonnei

10. Morphology
• Small Gram negative
• Facultative anaerobe
• Coliform bacillus
• Non motile
• Possess capsule
• Non lactose fermenting
Fig: Shigella (
http://www.infectioncontroltoday.com/news/
2015/04/multidrugresistant-
shigellosis-is-spreading-in-the-us.aspx
)

11. Clinical Syndromes
• Happens in 2 stages. Main symptoms are water like diarrhoea which
changes into dysentery along with frequent passage of blood and mucus
with stool as well as tenesmus, cramps and fever.
• Early stage: Watery diarrhoea attributed to enterotoxic activity of shiga toxin
Fever attributes to neurotoxic activity.
This process involve :
Ingestion
Non invasive colonisation
Production of enterotoxins by pathogenic bacteria in small intestine
2nd
Stage: Tissue invasion of large intestine
Cytotoxic activity of Shiga toxin increases.

12. Pathogenesis
• Shigella infection is typically by ingestion.
• Shigella species generally invade the epithelial lining of the colon, causing
severe inflammation and death of the cells lining the colon.
• Some strains of Shigella produce toxins which contribute to disease during
infection. S. flexneri strains produce ShET1 and ShET2, which may
contribute to diarrhoea.
• Shigella species invade the host through the M-cells interspersed in the gut
epithelia of the small intestine, as they do not interact with the apical surface
of epithelial cells, preferring the basolateral side.
• After invasion, Shigella cells multiply intracellularly and spread to
neighbouring epithelial cells, resulting in tissue destruction and
characteristic pathology of shigellosis

13. Diagonosis
• Antibiotic-sensitivity tests are important because Shigella is often resistant
to multiple antibiotics.
• More advanced testing and surveillance methods, such as plasmid profiling
and chromosomal fingerprinting, can also be used. So-called “genetic
fingerprinting” of the bacterial isolate, using pulsed-field gel electrophoresis
(PFGE) is a molecular technique that can help to characterize Shigella
isolates, whether obtained from human or food samples.

14. Drugs used against shigella
• The World Health Organization (WHO) recommends that all suspected
cases of shigellosis based on clinical features be treated with effective
antimicrobials (antibiotics). The choice of antimicrobial drug has changed
over the years as resistance to antibiotics has occurred, with different
patterns of resistance being reported around the world. Evidence is
insufficient to consider any class of antibiotic superior in efficacy in treating
Shigella dysentery. The following antibiotics are used to treat Shigella
dysentery:
• Beta-lactams: Ampicillin, amoxicillin, third-generation cephalosporins
(cefixime, ceftriaxone), and pivmecillinam (not available in the United
States)
• Quinolones: Nalidixic acid, ciprofloxacin, norfloxacin, and ofloxacin
• Macrolides: Azithromycin
• Others: sulfonamides, tetracycline, cotrimoxazole, and furazolidone.
• Most clinical infections with S sonnei are self-limited (48-72 h) and may not
require antimicrobial therapy.

15. Recent developments in drug design
• Attenuated S.flexineri 2a strain on human trials as well as primate samples
have shown promises of first vaccine against shigella infection.
• Natural products like usnic acid, Propolin D, Betulinic acid, Longifolene have
shown high promise against shigella.
• ETVAX One candidate is a formalin-inactivated ETEC vaccine (ETVAX)
consisting of four E. coli preparations, each engineered to hyper-produce
the CFA/1, CS3, CS5, and CS6 antigens of ETEC. In addition, the vaccine
contains a cholera B subunit modified to be more cross-reactive with the B
subunit of ETEC. ETVAX is co-administered with a double-mutant of the
ETEC heat-labile toxin (dmLT), which serves as a potent mucosal adjuvant.
• TSWC The other candidate includes formalin-killed S. flexneri 2a and 3a
and S. sonnei prepared as a trivalent vaccine, called TSWC. A prototype of
TSWC, S. flexneri 2a, was administered to North American volunteers and
found to be safe and immunogenic; it is now currently in a challenge trial.

16. Reference
• Cohen, M. S., Cannon, J. G., Jerse, A. E., Charniga, L. M., Isbey, S. F., &
Whicker, L. G. (1994). Human experimentation with Neisseria gonorrhoeae:
rationale, methods, and implications for the biology of infection and vaccine
development. Journal of Infectious Diseases, 169(3), 532-537.
• Tan, L. K., Carlone, G. M., & Borrow, R. (2014). Advances in the
development of vaccines against Neisseria meningitidis. New England
Journal of Medicine, 362(16), 1511-1520.
• Ruddock, P. S., Liao, M., Foster, B. C., Lawson, L., Arnason, J. T., & Dillon,
J. A. R. (2015). Garlic natural health products exhibit variable constituent
levels and antimicrobial activity against Neisseria gonorrhoeae,
Staphylococcus aureus and Enterococcus faecalis. Phytotherapy Research,
19(4), 327-334.
• Sansonetti, P. J. (1992). Molecular and cellular biology of Shigella flexneri
invasiveness: from cell assay systems to shigellosis. In Pathogenesis of
Shigellosis (pp. 1-19). Springer Berlin Heidelberg.
• Shata, M. T., Stevceva, L., Agwale, S., Lewis, G. K., & Hone, D. M. (2015).
Recent advances with recombinant bacterial vaccine vectors. Molecular
medicine today, 6(2), 66-71.