Batterjee Medical College
Batterjee Medical College
Aerobic
Gram-Negative Cocci
Dr. Manal El Said
Head of Microbiology Department
Batterjee Medical College
Neisseria
Dr. Manal El Said
Head of Microbiology Department
Batterjee Medical College
Neisseria meningitidis
(Meningococcus)
Diseases
- Meningitis (inflammation the meninges of the brain or spinal cord)
- Meningococcemia.
Characteristics
• Gram-negative "kidney-bean" diplococci.
• Oxidase-positive.
• Large polysaccharide capsule.
One of the three classic encapsulated pyogenic bacteria (Streptococcus
pneumoniae and Haemophilus influenzae are the other two).
Habitat and Transmission
•Habitat is the human upper respiratory tract
•Transmission is via respiratory droplets.
Batterjee Medical College
Neisseria meningitidis
(Meningococcus)
Pathogenesis
•The organism reaches the
meninges via the bloodstream.
•Endotoxin in cell wall causes
symptoms of septic shock.
• IgA protease produced.
•Capsule is antiphagocytic.
•Deficiency in late complement
components
recurrent
meningococcal infections.
The characteristic skin rash (purpura) of
meningococcal septicemia, caused by
Neisseria meningitidis
Batterjee Medical College
Neisseria meningitidis
(Meningococcus)
Laboratory Diagnosis
• Gram-stained smear and culture.
• Oxidase-positive colonies on chocolate agar.
• Ferments maltose in contrast to gonococci, which do not.
Batterjee Medical College
Neisseria meningitidis
(Meningococcus)
Laboratory Diagnosis
Round, moist, glistening & convex colonies
N. meningitidis - proper streaking and growth on blood agar plate.
Batterjee Medical College
Neisseria meningitidis
(Meningococcus)
Laboratory Diagnosis
+
Glu
+
Mal
-
Lac
Suc
Batterjee Medical College
Neisseria meningitidis
(Meningococcus)
Treatment
Penicillin G (no significant resistance).
Prevention
• Vaccine contains capsular polysaccharide of strains A, C,
Y & W-135.
• One form of the vaccine contains the polysaccharides
coupled to a carrier protein (diphtheria toxoid) and one
contains only the polysaccharides.
• Rifampin or ciprofloxacin given to close contacts to
decrease oropharyngeal carriage.
Batterjee Medical College
Neisseria gonorrhoeae
(Gonococcus)
Diseases
• Gonorrhea.
• Neonatal conjunctivitis
• Pelvic inflammatory disease.
Characteristics
• Gram-negative "kidney-bean" diplococci.
• Oxidase-positive.
• Insignificant capsule.
Batterjee Medical College
Neisseria gonorrhoeae
(Gonococcus)
Habitat and Transmission
• Habitat is the human genital tract.
• Transmission in adults is by sexual contact.
• Transmission to neonates is during birth.
Pathogenesis
•Organism invades mucous membranes
inflammation.
•Endotoxin weaker than that of meningococcus
severe disease when bacteremiaoccurs.
•IgA protease & pili are virulence factors
less
Batterjee Medical College
Neisseria gonorrhoeae
(Gonococcus)
Laboratory Diagnosis
•Gram-stained smear and culture.
•Organism visible intracellularly within neutrophils in urethral
exudate.
• Oxidase-positive colonies.
• Gonococci do not ferment maltose (meningococci do).
Left: Neisseria gonorrhoeae Gram stain of pure culture; Right: Neisseria gonorrhoeae Gram stain of a pustular exudate.
Batterjee Medical College
Neisseria gonorrhoeae
(Gonococcus)
Laboratory Diagnosis
Batterjee Medical College
Neisseria gonorrhoeae
(Gonococcus)
Treatment
• Ceftriaxone for uncomplicated cases.
• Tetracycline added for urethritis caused by Chlamydia
trachomatis.
• High-level resistance to penicillin is caused by plasmidencoded penicillinase.
• Low-level resistance to penicillin is caused by reduced
permeability and altered binding proteins.
Batterjee Medical College
Neisseria gonorrhoeae
(Gonococcus)
Prevention
• No drug or vaccine.
• Trace contacts and treat to interrupt transmission.
• Treat eyes of newborns with erythromycin ointment or silver
nitrate to prevent conjunctivitis.
Batterjee Medical College
Moraxella catarrhalis
• Small coccobacillary gram-negative rod
• It causes :
-Otitis media & sinusitis in children.
-Bronchitis & pneumonia in older people with
chronic obstructive pulmonary disease
• It is found only in humans
• It transmitted by respiratory aerosol.
Batterjee Medical College
Anaerobic
Gram-Negative Cocci
Dr. Manal El Said
Head of Microbiology Department
Batterjee Medical College
Veillonella
• Veillonella parvula is an anaerobic gram-negative
diplococcus
• It is a normal flora of the mouth, colon & vagina.
• It is a rare opportunistic pathogen that causes
abscesses of the sinuses, tonsils & brain
• It is usually in mixed anaerobic infections.