Bacterial Disease

1. By
Mr. Sainath H. Kamble
Assistant Professor in Microbiology
D.B.F. Dayanand College of Arts and Science, Solapur

2. Pseudomonas Aeruginosa
 Morphological Characters:-
 Pseudomonas aeruginosa is member of the Gamma
Proteobacteria class of Bacteria.
 It is a Gram-negative, aerobic rod belonging to the
bacterial family Pseudomonadaceae.
 Since the revisionist taxonomy based on conserved
macromolecules (e.g. 16S ribosomal RNA) the family
includes only members of the genus Pseudomonas which
are cleaved into eight groups.
 Pseudomonas aeruginosa is the type species of its group.
which contains 12 other members.

3.  Gram negative non sporing rods, motile with usually one polar
flagellum.
 Fimbriae may be present .
 It is non capsulated but many strains have a mucoid slime layer.
 Some strains, notably from respiratory tract infection in children
with fibrocystic disease, produce large amount of extracellular
polysaccharide slime.
 This forms a loose capsule (glycocalyx) in which microcolonies
of the bacillus are enmeshed and protected from the host defence.
 It is a rod about 1-5 µm long and 0.5-1.0 µm wide. P.
aeruginosa is an obligate respirer, using aerobic respiration (with
oxygen) as its optimal metabolism although can also respire
anaerobically on nitrate or other alternative electron acceptors.

4.  Cultural Characters:-
 Most strains are strict aerobes. But can grow anaerobically if nitrate is
available.
 The growth is range is 5-420 , optimum 37 0 but few other pseudomonas
species will grow in serial subculture at 420 . It grows well on ordinary
media, producing large. Opaque , Irregular colonies, with a distinctive,
musty, mawkish or earthy smell .
 Iridescent patches with a metallic sheen are seen in cultures on nutrient
agar.
 Crystals are seen beneath the patches. It grows on MacConkey and
DCA media, forming nonlactose –fermenting colonies. Many strains are
hemolytic on blood agar.
 In broth, it forms a dense turbidity with a surface pellicle.
 Pseudomonas aeruginosa produces a number of pigments , the best
known being pyocyanin and fluorescin .
 Pyocyanin is a bluish green phenazine pigment soluble in water and
chloroform .Fluorescin (Pyoverdin) greenish yellow pigment soluble in
water but not in chloroform.
 Pyocyanin is produced only by P.aeruginosa but fluorescin may be
produced by other species also.

5.  Other pigments produced are pyorubin (red) pyomelanin
(brown) in various combinations.
 Some strains may be non- pigmented .
 It is not known whether the pigments have any role in
pathogenesis.
 Some of the pigments particularly pyocyanin, inhibit the growth
of many other bacteria may therefore contribute to P. aeruginosa
emerging as the dominant bacterium in mixed infections.

6. Biochemical reactions
 The metabolism is oxidative and nonfermentative.
 Peptone water sugars are unsuitable for detecting acid
production, since this is weak and gets neutralized by alkali
produced from peptone.
 An ammonium salt medium in which the sugar is the only
carbon source is the best. Glucose is utilized oxidatively,
forming acid only.
 Indole, MR, VP and H2S tests are negative.
 Nitrate are reduced to nitrites and further to gaseous nitrogen .
 Catalase, oxidase and arginine dihydrolase are positive.

7. Antigenic Structure
 Antigen of extracellular slime polysaccharide
 Extracellular polysaccharide antigens have been targets for Stimulating specific
protective Immunity .
 O antigens
 Possesses 19 distinct, group specific O antigens
 Heat labile
 H antigens
 Two heat labile antigens recognised in P. aeruginosa
 Pathogenic bacteria produce an elaborate assortment of extracellular and cell-
associated bacterial products that enable colonization and establishment of
infection within a host.
 Lipopolysaccharide (LPS) molecules are cell surface factors that are typically
known for their protective role against serum-mediated lysis and their endotoxic
properties.
 The most heterogeneous portion of LPS is the O antigen or O polysaccharide, and
it is this region which confers serum resistance to the organism.
 Pseudomonas aeruginosa is capable of concomitantly synthesizing two types of
LPS referred to as A band and B band. The A-band LPS contains a conserved O
polysaccharide region composed of D-rhamnose (homopolymer), while the B-
band O-antigen (heteropolymer) structure varies among the 20 O serotypes of P.
aeruginosa.

8. Modes of transmission
 Although colonization usually precedes infections
by Pseudomonas aeruginosa, the exact source and mode
of transmission of the pathogen are often unclear
because of its ubiquitous presence in the environment.
 It is sometimes present as part of the normal flora of
humans, although the prevalence of colonization of
healthy individuals outside the hospital is relatively low
(estimates range from 0 to 24 percent depending on the
anatomical locale).
 The pili of Pseudomonas aeruginosa will adhere to the
epithelial cells of the upper respiratory tract and, by
inference, to other epithelial cells as well. These adhesins
appear to bind to specific galactose or mannose or sialic
acid receptors on epithelial cells.

9.  Colonization of the respiratory tract by Pseudomonas requires pili adherence and
may be aided by production of a protease enzyme that degrades fibronectin in
order to expose the underlying pilus receptors on the epithelial cell surface.
 Tissue injury may also play a role in colonization of the respiratory tract, since P.
aeruginosa will adhere to tracheal epithelial cells of mice infected with influenza
virus but not to normal tracheal epithelium.
 This has been called opportunistic adherence, and it may be an important step
inPseudomonas keratitis and urinary tract infections, as well as infections of the
respiratory tract.
 Pseudomonas aeruginosa, is spread by direct contact with the organism on a
contaminated surface, instrument, or other object.
 It is a bacteria, not a virus. It is not spread by sneeze droplets like influenza,
however it can live in any moisture for as long as the moisture is present.
 Pseudomonas can cause infection if it gets into the wrong place at the wrong
time.

10.  It can be found in urinary tract infections, pneumonia, wound
infections, etc.
 We've isolated it from surgical instruments, nurses medicine carts,
dietary food surfaces, hospital administration board room tables.
 It is especially adept at contaminating high-calorie, high-fat (TPN)
solutions as well as dextrose and normal saline IV solutions.
 It can be successfully treated in the majority of cases, although resistant
strains are commonly encountered.
 The major threat is as a secondary invader.
The skin is a great barrier to the bacteria, however a wound or other
trauma situation can give this organism a foothold to begin an
infection.

11. Pathogenesis
 For an opportunistic pathogen such as Pseudomonas aeruginosa, the
disease process begins with some alteration or circumvention of normal
host defenses.
 The pathogenesis of Pseudomonas infections is multifactorial, as
suggested by the number and wide array of virulence determinants
possessed by the bacterium.
 Multiple and diverse determinants of virulence are expected in the wide
range of diseases caused, which include septicemia, urinary tract
infections, pneumonia, chronic lung infections, endocarditis, dermatitis,
and osteochondritis.
 Most Pseudomonas infections are both invasive and toxinogenic.
 The ultimate Pseudomonas infection may be seen as composed of three
distinct stages: (1) bacterial attachment and colonization; (2) local
invasion; (3) disseminated systemic disease.
 However, the disease process may stop at any stage.
 Particular bacterial determinants of virulence mediate each of these
stages and are ultimately responsible for the characteristic syndromes
that accompany the disease.

12.  The mechanisms of pathogenesis are not cleared
understood.
 Several toxic extracellular products have been identified
in the culture filtrates, such as exotoxins A and S.
 Exotoxin A acts as an NADase, resembling the diptheria
toxin,good antibody respose to exotoxin A considered a
favourable sign in severe infections with Ps aeruginosa.
 Other toxic products include proteases, elastases,
hemolysins and enterotoxin.
 Slime layer acts as a capsule in enhancing virulence.

13. Symptoms
 The symptoms depend on the part of the body that is
infected. Fever, fatigue, muscle and joint pain, etc are the
most common symptoms.
 Here's a list of the respective symptoms of each infection.
Bone infection: Swollen infected part, redness.
Ear infection: Pain in the ear, reduced ability to hear, facial
paralysis.
Eye infection: Pain in the eye, reduced vision, swollen eyelids.
Cystic fibrosis: Cough, reduced appetite, fast breathing,
enlargement of the abdomen.
Skin infection: Ulcer that can result in bleeding.

14. Laboratory Diagnosis
 Bacterium grows readily on most media.
 The identification of pigmented strains of the bacillus from
clinical specimen is easy, but about 10 percent isolates may
be non pigmented.
 Prompt oxidase reaction and arginine hydrolysis help in
their identification.
 It may be necessary to use selective media such as
cetrimide agar for isolation from feces or other samples
with mixed flora.
 As P.aeruginosa is a frequent contaminant, isolation of the
bacillus from a specimen should not always be taken as
aproof of its etiological role.
 Repeated isolations help to confirm the diagnosis.

15. Prophalaxis and treatment
 Prevention of Ps aeruginosa cross –infection in hospitals
requires constant vigilance and strict attention to asepsis.
 Antibiotic treatment is not always satisfactory.
 Immunotherapy in human burns cases with antiserum to Ps
aeruginosa may be useful.
 Pseudomonas vaccines are being tried in cystic fibrosis patients
who are highly vulnerableto pseudomonas infection.
 Specific antibacterial therapy constitutes only one aspect of the
management of serious pseudomonas infection.
 Treatment of the underlying diseases, correction of granulopenia
appropriate supportive therapy need attention.
 Occasional opportunist infection may be caused by a few other
species, such as Ps fluorescens , Ps putida and Ps stutzeri.

16. Thank You
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