haemophilus and other fastidious gram negative rods / orthodontic courses by indian dental academy

Haemophilus and Other Fastidious Gram-Negative Rods

INDIAN DENTAL ACADEMY

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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


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 Gram-negative 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

Haemophilus species require hemoglobin for growth:X-factor ( hemin): Heat-stable substanceV-factor (NAD): Heat- labile, coenzyme I, nicotinamide adenine dinucleotide, found in blood or secreted by certain organisms

H. influenzae satellitism around and between the large, white, hemolytic staphylococci


Haemophilus Species

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


Haemophilus speciesH.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 GroupA. actinomycetemcomitans on blood agar. Note the star-shaped centers of the colonies.

Microscopic morphology of A. actinomycetemcomitans (Gram stain).


HACEK GroupThe 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 CapnocytophagaGrowth 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 pneumophilaGram stain of specimen showing intracellular and extracellular Legionella pneumophila

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


Legionella pneumophila

(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.

A B


Legionella pneumophila

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 closely-related species


Thank you

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haemophilus and other fastidious gram negative rods / orthodontic courses by indian dental academy

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