Haemophilus and other fastidious gram negative rods /certified fixed orthodontic courses by Indian dental academy

Haemophilus and Other Fastidious GramNegative Rods

INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com


Case Study
 A 2-year-old unvaccinated child was seen in the
emergency room because of complaints of headache
and fever
 A cerebrospinal fluid(CSF) sample was obtained and
sent to the laboratory for culture
 The Gram stain showed many white blood cells and
many gram-negative, small bacilli

W.B. Saunders Company items and derived items copyright © 2001 by W.B. Saunders Company.

Points to Consider
 What clinical findings led the physician to request a
CSF culture?
 Based on the patient’s age, which organism would be
suspected?
 What growth requirements must be met to recover
the suspected agent?
 Which other fastidious organisms would be
considered?
 Other points to consider


Haemophilus and Other Fastidious Gramnegative Rods
 The fastidious group of gram-negative bacilli
include:
 Haemophilus
 HACEK
 Legionella
 Bordetella
 Pasteurella
 Brucella
 Francisella


Haemophilus Influenzae: Clinical Infections
 Infections caused by typable (encapsulated) strains
 Acute epiglottis or laryngotracheal infection in small children
 Cellulitis/arthritis
 Meningitis
 Pneumonia/septicemia (in children)
 Conjunctivitis


Haemophilus Influenzae: Clinical Infections
 Infections caused by Nontypable strains
 Otitis media
 Sinusitis
 Pneumonia, bronchitis (in adults)


Haemophilus Species
H. influenzae
satellitism around
and between the
large, white,
hemolytic
staphylococci
Haemophilus species require hemoglobin for growth:
X-factor ( hemin): Heat-stable substance
V-factor (NAD): Heat- labile, coenzyme I, nicotinamide
adenine dinucleotide, found in blood or secreted by
certain organisms


Haemophilus Species

Direct smear of H. influenzae in CSF in a
case of meningitis. Note the intracellular
and extracellular pleomorphic gramnegative bacilli.


Haemophilus species
H.influenzae growing on
chocolate agar. Notice the
semi-opaque, gray-white,
mucoid colonies characteristic
of encapsulated strains.

Gram stain of H. influenzae
from colony

Haemophilus Species: Identification

This organism would be identified as H. influenzae
because it is using both X and V factors.



This organism would be identified as H.
parainfluenzae because it is using V factor only.



This organism would be identified as H. aphrophilus because it is
using X factor only.



Under ultraviolet light, the organism on the bottom
is showing a positive porphyrin reaction, whereas
the organism on the top is demonstrating a
negative porphyrin reaction.


HACEK Group and Capnocytophaga
 HACEK is an acronym of the first initial of each genus
that belong in the group:
 Haemophilus aphrophilus
 Actinobacillus actinomycetemcomitans
 Cardiobacterium hominis
 Eikenella corrodens
 Kingella species

 Capnocytophaga sp.
 Has similar requirements as the HACEK group


HACEK Group and Capnocytophaga: General
Characteristics
 Gram-negative bacilli
 Require an increased CO2 (5%-10%) environment
 Significant cause of endocarditis
 Usual flora of the oral cavity
 Opportunists in immunocompromised hosts


HACEK Group
H. aphrophilus growing
on blood agar

Gram stain morphology of H.
aphrophilus

HACEK Group
A. actinomycetemcomitans on
blood agar. Note the starshaped centers of the
colonies.

Microscopic morphology of A.
actinomycetemcomitans (Gram
stain).

HACEK Group
The 48-hour growth of
colonies of C. hominis

Gram stain of C. hominis
showing typical “rosettes”


HACEK Group
E. corrodens on
chocolate agar

Gram stain morphology
of E. corrodens


HACEK Group and Capnocytophaga
Growth of Capnocytophaga
colonies on chocolate agar.
Compare this growth with
Eikenella

Gram stain of
Capnocytophaga
species

HACEK group

Gram stain of Kingella kingae showing plump
rods in chains. Compare this morphology with
other members of the HACEK group.


Pasteurella species
 General characteristics
 Colonizes mucous membranes of the upper respiratory tract
and gastrointestinal tracts of mammals and birds
 Human infections occur from bites and scratches inflicted by
animals
 Most common isolated species is Pasteurella multocida


Pasteurella species
 P. multocida: Clinical manifestations
 Localized infection after a bite or scratch
 Respiratory tract infection
 Life-threatening systemic diseases (e.g., meningitis,
bacteremia)


Pasteurella Multocida
 Culture characteristics
 Growth on 5% blood or chocolate shows small, smooth, convex
colonies
 “Musty” odor
 No growth on MacConkey agar; oxidase positive

 Microscopic examination
 Very small gram-negative rods
 Bipolar staining with Giemsa or methylene blue
 “Safety-pin” appearance


Pasteurella Multocida
P. multocida growing on blood
agar and chocolate agar. No
growth on MacConkey agar
plate.

Gram stain morphology of P.
multocida showing bipolar staining


Case Study
 Ten members of a group of 2 dozen retirees from the
tobacco industry became acutely ill with pneumonia
during a 2-week cruise
 The group was staying in a block of rooms together
and spent time socializing over drinks and cigarettes
in the cabins and saunas and at the poolside


Case Study
 On the fifth day of the cruise, several members went
to see the ship’s doctor because of a worsening
cough
 Chest x-rays revealed patchy lobar pneumonia in all
affected individuals
 The condition improved with erythromycin therapy


Legionella Species
 General characteristics
 Ubiquitous gram-negative rods
 Acquired by humans primarily through inhalation of aerosols

 Clinical infections
 Febrile disease with pneumonia (Legionnaire’s disease) and
extrapulmonary involvement
 Pontiac fever (without pulmonary involvement)
 Asymptomatic infection


Legionella pneumophila
Gram stain of specimen showing
intracellular and extracellular

L. pneumophila in specimen stained by direct fluorescent antibody technique.


A

B

(A) Nonselective buffered charcoal yeast extract (BCYE) plate
inoculated with sputum specimen.
(B) Selective BCYE inoculated with the same specimen but
treated before inoculation. Legionella colonies are the smallest
visible colonies.


L. pneumophila colony on BCYE agar after 3, 4, 5, and
7 days of incubation

Legionella pneumophila: Identification

Schema for identification of L. species


Points to Remember
 Clinical manifestations presented by the patient
 The types of infections these organisms produce
 The risk factors that predispose susceptible
individuals


Points to Remember
 What special growth supplements are required for
isolation
 Where these groups of organisms are usually found
 Characteristic features of the organisms for
identification and differentiation among closelyrelated species


Thank you
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Haemophilus and other fastidious gram negative rods /certified fixed orthodontic courses by Indian dental academy