1. Opportunistic
Pathogens

2. PATHOGEN
“A pathogen is a microbe or
microorganism such as a virus (such
as HIV), bacterium (such as staph),
prion, or fungus (such as yeast) that
causes disease in its animal or plant
host”.
First devised in 1880.

3. MAJOR HUMAN PATHOGENS
Bacillus anthracis
Clostridium botulinum
Bartonella spp.
Spanish influenza virus
Yersinia pestis
Mycobacterium leprae

4. PATHOGENESIS
“The pathogenesis of a disease is the
mechanism by which the disease is
caused. The term can also be used to
describe the origin and development
of the disease and whether it is
acute, chronic or recurrent”.

5. OPPORTUNISTIC PATHOGEN
 “An infectious microorganism that is
normally a commensal or does not harm its
host but can cause disease when the host’s
resistance is low”.
OPPORTUNISTIC INFECTION
 “An opportunistic infection is an infection
caused by pathogens, particularly
opportunistic pathogens”.

6. OPPORTUNISTIC CONDITIONS
 When the immune system isn’t working
properly, normal flora can overpopulate or
move into areas of the body where they do
not normally occur.
 When the balance of normal microbes is
disrupted, for example when a person takes
broad spectrum antibiotics.
 Disease can result when normal flora are
traumatically introduced to an area of the
body that is axenic or that they do not
normally occur in.

7. Causes of Immunodeficiency
 Malnutrition
 Chemotherapy for cancer
 Skin damage
 Medical procedures
 Pregnancy
 Immunosuppressing agents for organ transplant
recipients
 The concomitant presence of certain underlying
diseases such as cancer, diabetes, cystic fibrosis
 Side effects of certain medical therapies and drugs
such as corticosteroids
 Infection with immunity-destroying microorganisms
 Age, both old and young

8.  Candida albicans
 Staphylococcus
aureus
 Pseudomonas
aeruginosa

9. OPPORTUNISTIC BACTERIA
 Campylobacter
 Flavobacterium
 Haemophilus
 Mycobacterium
 Nocardia
 Pseudomonas
 Rhodococcus
 Salmonella
 Shigella
 Staphylococcus
 Streptococcus
 Treponema
 Yersinia

10. REFERENCES TO STUDY
OPPORTUNISTIC BACTERIA
There are two main references to study
opportunistic bacteria:
1. Opportunistic bacteria with reference to the
site change.
 Example
E.coli
2. Opportunistic bacteria with reference to the
immunocompromised condition.
 Example
AIDS and its related opportunistic bacteria.

11. Pseudomonas aeruginosa as an
opportunistic pathogen
 member of the Gamma Proteobacteria
 Gram-negative, aerobic rod
 Belongs to family Pseudomonadaceae.
 Oxidase-positive

12. Infections by Pseudomonas
aeroginosa
 urinary tract
infections,
 respiratory system
infections,
 dermatitis,
 bacteremia,
 bone and joint
infections,
 gastrointestinal
infections

13. Infections are caused particularly
in :
 Patients with severe burns
 cystic fibrosis
 cancer
 AIDS
Pseudomonas aeruginosa is primarily a
nosocomial pathogen.

14. Characteristics contributing to
its success as opportunistic
pathogen
Natural habitat
 Ubiquitous in soil and water, and on surfaces in
contact with soil or water
 Actively swimming by means of its flagellum.
Metabolism
 Respiratory and never fermentative
 Can grow in the absence of O2 if NO3 is
available as a respiratory electron
acceptor

15. Nutritional requirements
 Minimal nutritional
requirements
 Simplest medium for
growth consists of
acetate as a source of
carbon and ammonium
sulfate as a source of
nitrogen.

16. Optimum temperature for growth
 37 degrees
 Able to grow at temp as high as 42 degrees
Tolerance to physical conditions
 Resistant to high conc. of salt, dyes, weak
antiseptics and antibiotics

17. Resistance to antibiotics and phagocytes
 Naturally resistant to antibiotics due to the
permeabiliity barrier afforded by its Gram-
negative outer membrane.
 Living in association with the bacilli,
actinomycetes and molds; resistant to their
naturally-occuring antibiotics.
 Slime layer; anti-phagocytic effect

18. Pathogenesis of Pseudomonas
aeruginosa
Composed of three distinct stages
 bacterial attachment and colonization;
 local invasion;
 disseminated systemic disease.

19. Attachment and colonization
It uses
 Flagella
 Pilli
 Exopolysaccharide (alginate or slime)

20. Invasion
Produce extracellular enzymes and toxins that
 Break down physical barriers
 Damage host cells and immune defence.
Two exocellular proteases involved are:
 Elastase
 Alkaline protease
Some more proteins are; hemolysins and cytotoxins

21. Dissemination
 Involves spread of infection to other parts
 Mediated by same extracellular products that
produce localized infection

22. E.coli

23. Escherichia coli (E. coli ) is a
Gram-negative,
rod-shaped and
facultative anaerobic bacterium
Commonly found in the lower intestine
of warm-blooded organisms
(endotherms)
Help in food digestion.

25. E.coli as an opportunistic
bacteria:-
 Although it lives in a healthy micro
flora of a human body, but only in
specific situation, when it arrive from
intestine to other organs and
tissues, unfortunately, it can cause a
very serious infection and illnesses.
The most frequent are urinary tract
and sexual organs infections.

26. Infections:-
Virulent strains of E. coli can cause
 Gastroenteritis (inflammation of
stomach and small intestine)
 Urinary tract infections and
 Neonatal meningitis (colonisation
of new born’s intestine)

27. In rarer cases, virulent strains are also
responsible for
 Hemolytic-uremic syndrome
 Peritonitis (inflammation of
peritoneum)
 Mastitis (inflammation of breast
tissues)
 Septicemia (inflammation of whole
body) and
 Gram-negative pneumonia.

28. Classification of E.coli:-
 Enterotoxigenic E. coli (ETEC)
diarrhea (without fever) in humans, pigs, sheep,
goats, cattle, dogs, and horses
 Enteropathogenic E.coli (EPEC)
diarrhea in humans, rabbits, dogs, cats and
horses
 Enteroinvasive E. coli (EIEC)
found only in humans
 Enterohemorrhagic E.coli (EHEC)
found in humans, cattle, and goats
 Enteroaggregative E.coli (EAEC)
found only in humans

30. Serotypes
Pathogenic E.coli strains can be
categorised as follows:-
 O antigen: part of lipopolysaccharide
layer
 K antigen: capsule
 H antigen: flagellin
 F antigen: MR fimbriae (rare)
For example E.coli strain EDL933 is of
the O157:H7 group.

31. Symptoms:-
 Bad stomach cramps
 Belly pain
 Vomiting
 Diarrhea, sometimes with blood in it
 Painful urination
Children are more likely than adults
to have symptoms. 3 or 4 days

32. Causes of infection:-
 E. coli in food
 During meat processing.
 Meat is not cooked to 160°F (71°C).
 Food come in contact with raw meat
 E. coli from person-to-person contact
When an infected person does not wash
his hands well after a bowel movement.

33.  E. coli in water
Human or animal feces infected
with E. coli sometimes get into lakes,
pools, and water supplies. People can
become infected when a
contaminated city or town water
supply has not been properly treated
with chlorine or when people
accidentally swallow contaminated
water.

34. Precautions:-
 Cook all types of beef to at least 160°F (71°C).
 Wash any tools or kitchen surfaces that have
touched raw meat.
 Wash your hands properly after using washroom.
 Use only pasteurized milk, dairy, and juice
products.
 Use only treated, or chlorinated, drinking water.

35. Summary
In summary, E. coli is an opportunistic
pathogen that can produce a variety
of symptoms in its host. However, if
precautionary measures are taken, E.
coli infections can be limited or
eliminated.

36. GENERAL INTRODUCTION OF AIDS
 Acquired immunodeficiency syndrome (AIDS)
 Human immunodeficiency virus (HIV)
 Retrovirus
 CD4 T cells, macrophages and dendrite cells.
 Cellular immunity is lost.
 leaves individuals susceptible to various
opportunistic infections

37. Opportunistic infections
association with HIV and AIDS
 HIV does not kill anybody directly.
 People with HIV can get many infections called
opportunistic infections.
 Many of these illnesses are very serious, and they
need to be treated and some can be prevented.
 People with advanced HIV infections are
vulnerable to infections and malignancies.
 Opportunistic Infections are caused by various
pathogenic microorganisms such as
bacteria, fungi, virus and parasites.

38. OPPORTUNISTIC BACTERIAL
PATHOGENS
 Bacterial pathogens are associated with the
significant proportion of morbidity and mortality.
The following genera of pathogens are most
common in person infected with HIV.
 Salmonella
 Campylobacter  Shigella
 Flavobacterium  Staphylococcus
 Haemophilus  Streptococcus
 Mycobacterium  Treponema
 Nocardia  Yersinia
 Pseudomonas
 Rhodococcus

39. Campylobacterr
 Campylobacter
Campylobacter is a genus that belongs to Family
Campylobacteraceae of Kingdom Bacteria.
 Twisted bacteria with spiral or corkscrew
appearance.
 These are motile with either unipolar or bipolar
flagella
 Gram-negative.
 Microaerophilic
 Oxidase positive test.

40. Campylobacter &AIDS
 Campylobacter infections are among the most
common bacterial infections in humans.
 Diarrhoea
 Bacteremia
 C. jejuni is usually the most common cause of
community-acquired inflammatory enteritis.
 Symptoms Includes abdominal
pain, cramping, dehydration and fever.

41. Flavobacterium
 Flavobacterium is a genus
that belongs to Family
Flavobacteriaceae.
 Gram-negative bacteria.
 Rod shaped bacteria
 They maybe motile or non-motile
 Found in soil and fresh water

42. Flavobacterium & AIDS
 Flavobacterium spp. may play a pathogenic
role in patients with advanced HIV disease
 Endocarditis
 Pneumonia
 Bacteremia
 F. meningosepticum is the most imp example of
this genus.

43. Haemophilus
 Haemophilus is a genus that belongs to
the Pasteurellaceae family
 Gram-negative bacteria.
 Pleomorphic bacteria (wide range of shapes
they occasionally assume)
 Aerobic or facultatively anaerobic.
 The genus includes commensal
and pathogenic organisms

44. Haemophilus & AIDS
 Meningitis is one of the most common
bacterial infections occurring in persons
infected with HIV caused by Haemophilus
influenzae,
 Pneumonia
 Upper respiratory tract infections, such as
otitis and sinusitis
 Genital infections.
 Recently HIV infection increases the risk of
acquiring invasive H. influenza infection.

45. OPPORTUNISTIC BACTERIAL
PATHOGENS
 Oppertunistic infections are also caused by
abnormal immune system of host
 Because of this reason such infections are
most common in person infected with
HIV.
 We will discuss the effect of five bacterial
genera as oppertunistic pathogens due to
weak immune system of the host

46. Nocardia
 Nocardia is a gram positive actinomycete.
 Human infection is rare and
contracted through inhalation.
 Infection is more
common among immunocompromised
patients,
especially those with impaired cell mediated
immunity.
 The patient may have other infections e.g
tuberculosis.

47. Rhodococcus
 Pneumonia is the most common
manifestation of Rhodococcus infection.
 Very most of cases originally reported were in
patients who were immunocompromised due
to malignancies, immunosuppressive.
 Pulmonary infection occurs by the inhalation
of the Rhodococcus particularly Rhodococcus
equi

48. Salmonella
 Salmonella infection has an increased incidence
in HIV infected populations.
 Salmonellosis and bacteremia are occurring at
an increased rate in person with HIV.
 A characteristic feature of Salmonellosis in AIDS
is the relapses that occur during appropriate
antibiotic therapy.
 S. typhimurium and S. enteridis are the two most
common serotypes isolated from the blood of
patients with AIDS in the United States

49. Yersinia
 Yersinia is responsible for causing plague in
peoples infected with AIDS
 Y. pestis is a gram-negative, facultatively
aerobic rod it is primarily a rodent pathogen.
 The vactor for this bacterium is a rat flea ,
Xenopsylla cheopis.
 Rat flea is actually an insect which transmits
that bacterium between two hosts.

50. Mycobacterium
 Tuberculosis is an unquestionably, the most
potent opportunistic bacterial infection
complicating HIV infection caused by
Mycobacerium tuberculosis.
 It is responsible for more than 2 million deaths
and 8 million new cases annually
 In India, tuberculosis is the most common
opportunistic infection.
 About a third of the HIV positive population
worldwide is coinfected with M. tuberculosis.

51.  Taxonomy Shigella
Family Enterobacteriaceae
 Four species:
• Shigella dysenteriae:
• Shigella flexneri:
• Shigella sonnei:
• Shigella boydii
 Morphology
rod-shaped
 Gram-negative

52.  General characteristics
 facultatively anaerobic
 Non-lactose fermenting
 non-motile
 Infection
 spread from human to human via the
fecal-oral route
 major cause of diarrheal disease
 HIV-infected persons are at increased risk
for infection

53. Staphylococcus
Taxonomy
 Genus Staphylococcus
 Family
Staphylococcaceae
Morphology
 spherical
 1 µm in size
 thick cell wall
 Gram-positive

54.  General characteristics
 facultative anaerobe
 immobile
 Coagulase Positive
 Are resistant to
 122 °F temperatures
 high salt concentrations (<10%)
 drying
 Infection
 common flora: skin, nasal cavity, pharynx,
gastrointestinal tract, genitourinary tract

55.  A bacteremia may result in
seeding other internal
abscesses, other skin
lesions, or infections in the
lung, kidney, heart,
skeletal muscle or
meninges.
 common cause of
community-acquired (CA)
or hospital-acquired (HA)
bacterial skin and soft-
tissue infections among
patients with HIV infection.

56. Pseudomonas aeruginosa
 Taxonomy
 genus Pseudomonas
 family Pseudomonadaceae
 Morphology
 rod-shape
 1-5 µm long and 0.5-1.0 µm
wide
 monoflagellated

57.  gram-negative
 Infection
 it often colonizes immuno compromised
patients, like those with cystic fibrosis,
cancer, or AIDS .
 takes advantage of an individual's weakened
immune system .
 produces tissue-damaging toxins.
 causes urinary tract infections, respiratory
system infections, dermatitis, soft tissue
infections, bone and joint infections,
gastrointestinal infections .

58. Streptococcus pneumoniae
 Taxonomy
 Genus Streptococcus
 family Streptococcaceae.
 Morphology
 Cocci
 0.5-1.2um
 often Arranged in Pairs or
Chains
 Gram-positive

59.  General characteristics
 Non motile
 Carbohydrates fermenters
 Infection
 spontaneously cause disease in humans,
monkeys, rabbits, horses, mice and guinea pigs.
 Patients with HIV infection are at increased risk
for bacterial pneumonia

60. Treponema pallidum
 Taxonomy
 genus Treponema
 family Spirochaetaceae.
 Morphology
 spiral-shaped
 0.2 µm in diameter and 6-
15 µm in length
 Gram negative

61. General characteristics
 mobile
 endoflagella
 Infection
 transmitted by direct contact
 Infection is initiated when T. pallidum penetrates
dermal micro abrasions or intact mucous
membranes.
 Neurosyphilis is most common in patients with
HIV infection.
 headache, meningeal irritation and nerve
abnormalities.