1. Medical Microbiology
Systemic bactreiology
Gram +ve cocci
Lecture-7
Dr. Saleh M Y OTH
PhD
Medical Molecular Biotechnology and Infectious Diseases
013/10/2010
IMS - MSU

2. Koch's postulates Sporatic disease
Pathology
Epidemiology Acute disease
Etiology Chronic disease
Infection Latent (recurrent) disease
Disease
Pathogen Local infection
Invasiveness Systemic, generalized infection
Opportunist Focal infection
Reservoirs Primary infection
Carrier Secondary infection
Communicable (contagious) diseases Inapparent, subclinical infection
Noncommunicable infectious diseases Nosocomial infections
Direct contact transmission Bacteremia, viremia
Indirect contact transmission Septicemia
Fomite Toxemia
Vectors Symptoms
Droplet (nuclei) transmission Portal of entry
Epidemic Portal of exit
Pandemic Stages of disease:
Endemic Incubation period
Sporadic Disease Period of illness (invasive period)
Convalescence 2

3. Streptococcus pneumoniae
Pneumonia
3

4. - Causes 60-70% of all bacterial
pneumonias
- Small, lancet-shaped cells
arranged in pairs and short
chains
- Culture requires blood or
chocolate agar
- Growth improved by 5-10% CO2
- Lack catalase and peroxidases
– cultures die in O2 4

5. S. pneumoniae
- All pathogenic strains form large capsules –
major virulence factor
- Specific soluble substance (SSS) varies
among types
- 90 different capsular types have been
identified
- Causes pneumonia and otitis media
5

6. Epidemiology and Pathology
- 5-50% of all people carry it as normal flora in the
nasopharynx; infections are usually endogenous
- Very delicate, does not survive long outside of its
habitat
- Young children, elderly, immunocompromised,
those with other lung diseases or viral infections,
persons living in close quarters are predisposed to
pneumonia
- Pneumonia occurs when cells are aspirated into the
lungs of susceptible individuals
- Pneumococci multiply and induce an overwhelming
inflammatory response
- Gains access to middle ear by way of eustachian
6
tube

7. Diagnosing Streptococcus pneumoniae
7

8. The course of bacterial pneumonia
8

9. View of ear anatomy indicating route
of infection
9

10. Cultivation and Diagnosis
- Gram stain of specimen – presumptive
identification
- Quellung test or capsular swelling reaction
- α-hemolytic; optochin sensitivity, bile
solubility, inulin fermentation
10

11. Treatment and Prevention
Traditionally treated with penicillin G or V
Increased drug resistance
Two vaccines available for high risk
individuals:
- Capsular antigen vaccine for older adults and
other high risk individuals – effective 5 years
- Conjugate vaccine for children 2 to 23 months
11

12. Gram nigative cocci
Family Neisseriaceae
12

13. Family Neisseriaceae
Gram-negative cocci
Residents of mucous membranes of warm-
blooded animals
Genera include Neisseria, Branhamella,
Moraxella
Two primary human pathogens:
- Neisseria gonorrhoeae (STD)
- Neisseria meningitidis
13

14. Genus Neisseria
- Gram-negative, bean-shaped, diplococci
- None develop flagella or spores
- Capsules on pathogens
- Pili
- Strict parasites, do not survive long outside of the
host
- Aerobic or microaerophilic
- Oxidative metabolism
- Produce catalase and cytochrome oxidase
- Pathogenic species require enriched complex
media and CO2
14

15. Neisseria Gonorrhoeae:
The Gonococcus
Causes gonorrhea, an STD
Virulence factors:
- Fimbriae, other surface molecules for
attachment; slows phagocytosis
- IgA protease – cleaves secretory IgA
15

16. Epidemiology and Pathology
- Strictly a human infection
- In top 5 STDs
- Infectious dose 100-1,000
- Does not survive more than 1-2 hours
on fomites
16

17. Comparative incidence of reportable
infectious STDs
17

18. Gonorrhea
Infection is asymptomatic in 10% of males and
50% of females
Males – urethritis, yellowish discharge, scarring,
and infertility
Females – vaginitis, urethritis, salpingitis (PID)
mixed anaerobic abdominal infection,
common cause of sterility and ectopic tubal
pregnancies
Extragenital infections – anal, pharygeal,
conjunctivitis, septicemia, arthritis
18

19. Gonorrheal damage to the male reproductive
tract
19

20. Ascending gonorrhea in women
20

21. Gonorrhea in Newborns
Infected as they pass through birth canal
Eye inflammation, blindness
Prevented by prophylaxis immediately
after birth
21

22. Diagnosis and Control
Gram stain – Gram-negative intracellular
(neutrophils) diplococci from urethral, vaginal,
cervical, or eye exudate – presumptive
identification
20-30% of new cases are penicillinase-producing
PPNG or tetracycline resistant TRNG
Combined therapies indicated
Recurrent infections can occur
Reportable infectious disease
22

23. Gram stain of urethral pus
23

24. Neisseria Meningitidis: The
Meningococcus
Virulence factors:
- Capsule
- Adhesive fimbriae
- IgA protease
- Endotoxin
12 strains; serotypes A, B, C cause most
cases
24

25. Epidemiology and Pathogenesis
Prevalent cause of meningitis; sporadic or
epidemic
Human reservoir – nasopharynx; 3-30% of adult
population; higher in institutional settings
High risk individuals are those living in close
quarters, children 6 months-3 years, children
and young adults 10-20 years
25

26. Epidemiology and Pathogenesis …
Disease begins when bacteria enter bloodstream,
cross the blood-brain barrier, permeate the
meninges, and grow in the cerebrospinal fluid
Very rapid onset; neurological symptoms;
endotoxin causes hemorrhage and shock; can
be fatal
26

27. Dissemination of the meningococcus from
a nasopharyngeal infection
27

28. One clinical sign of meningococcemia
28

29. Clinical Diagnosis
Gram stain CSF, blood, or asopharyngeal
sample
Culture for differentiation
Rapid tests for capsular polysaccharide
29

30. Treatment and Prevention
Treated with IV penicillin G, cephalosporin
Prophylactic treatment of family members,
medical personnel, or children in close
contact with patient
Primary vaccine contains specific purified
capsular antigens
30

31. 31

32. Other Gram-Negative Cocci and
Coccobacilli
Genus Branhamella
- Branhamella catarrhalis – found in nasopharynx:
significant opportunist in cancer, diabetes,
alcoholism
Genus Moraxella
- Bacilli – found on mucous membranes
Genus Acinetobacter
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