Haemophilus and the HACEK group Flashcards
General characteristic of Pasteurellaceae family
-facultative anaerobes • Gram (-) • pleomorphic • coccoid-shaped to rod-shaped cells • nonmotile •reduction of nitrates to nitrites • oxidase & catalase (+) - obligate parasites (exp. Haemophilus ducreyi)
4 genera of Pasteurellaceae family
Haemophilus
Actinobacillus
Pasteurella
Aggregatibacter
HACEK
- Haemophilus
- Aggregatibacter
- Cardiobacterium
- Eikenella
- Kingella
Where do HACEK organism resides
- oral cavity
- nasopharynx
some spp can cause ENDOCARDITIS
General characteristics of Haemophilus
Gram (-) • coccobacilli • pleomorphic • nonmotile •reduce nitrates to nitrites • ferment carbohydrates • oxidase & catalase (+)
Major pathogenic spp of Haemophilus
H. influenzae
H. aegyptius
H. ducreyi
Haemophilus require ______ to grow
“blood lovers”
require preformed growth factors present in blood the X and V factor
Growth factor in blood referred as HEMIN or HEMATIN
X factor
X stands for unknown
-When Haemophilus spp. are grown
anaerobically, they do not require heme but still require NAD
Growth factor in blood referred to as NICOTINAMIDE ADENINE DINUCLEOTIDE (NAD factor)
V factor
V stands for vitamin
- When Haemophilus spp. are grown
anaerobically, they do not require heme but still require NAD
Haemophilus spp. with “PARA” needs what growth factor
need only V factor for growth
Haemophilus spp. with “PARA” does not grow on this type of medium
SBA medium
On what medium Haemophilus spp. are isolated and recovered
- Chocolate agar
- because the lysis of RBC in this medium releases both X and V factor & inactivates NADases
The Haemophilusisolate gets X factor from the SBA & V factor from one of the organisms, except;
Neisseria spp.
Streptococcus pneumoniae
Staphylococcus aureus
Escherichia coli
- Escherichia coli
Staphylococcus aureus, Streptococcus
pneumoniae, or Neisseria spp., produces
V factor as a by-product of metabolism
This phenomenon happens when an organism, such as
Staphylococcus aureus, Streptococcus
pneumoniae, or Neisseria spp., produces
V factor as a by-product of metabolism
SATELLITISM
- helps recognition of haemophilum spp that need V factor for growth.
- Haemophilus spp. grows around colonies of these organisms
- In SBA agar
V factor producing organisms
- Staphylococcus aureus
- Streptococcus pneumoniae - Neisseria spp.
Haemophilus Influenzae:
Virulence factors
- Capsule
- IgA protease
- Fimbriae
- outer membrane proteins and LPS
the only member of the heamophilus genus that produces IgA
protease (can cleave secretory
IgA)
H. influenzae
What virulence factor of H. influenzae plays the most significant role in infection.
Capsule
type of H. influenzae capsule that has antiphagocytic and anticomplementray activity and is the leading cause of meningitis
Type B capsule
- Hib strain
what do you call group of H. influenzae that is not encapsulated
- non-typeable H. influenzae (NTHi)
2 patterns of H. influenzae infection
INVASIVE & LOCALIZED
Invasive infections of H. influenzae is caused by what type of strain
ENCAPSULATED STRAINS in which bacteremia plays a vital role
e.g., SAME PT septicemia, arthritis, meningitis, epiglottitis, pneumonia &
tracheitis
Localized infections of H. influenzae is caused by what type of strain
- contagious spread of NHTi strains
in localized H. influenzae infections, what organ serves as the reservoir in chronic middle ear infections and that the bacteria develop biofilms *
spleen tonsils adenoid kidneys mesentery gallbladder
- adenoid
Haemophilus spp associated with acute contagious conjunctivitis: pinkeye
Haemophilus aegyptius
Haemophilus spp that can cause severe systemic
disease: Brazilian purpuric
fever (BPF)
Haemophilus influenzae
biogroup aegyptius
causes severe systemic disease: Brazilian purpuric fever (BPF) *
Haemophilus aegyptius Haemophilus ducreyi Haemophilus influenzae biogroup aegyptius none of the choices all of the first three choices
Haemophilus influenzae biogroup aegyptius
Recovered using CA(RBC heat lysis releases BOTH both X factor & Vfactor & inactivates *
RNAses DNAses NADses isomerases none of the choices
NADses
-enzyme that hydrolyzes V factor
Haemophilus influenzae causes ocular infections(pinkeye) and requires X and V factors in the primary medium for growth. The subspecies Haemophilus influenza (biogroup) aegyptius can further be identified and differentiated by which two tests? *
A. Indole and xylose
B. Glucose and urease
C. Oxidase and catalase
D. ALA test and oxidase
A. Indole and xylose
Haemophilus spp that is the causative agent of
chancroid
“soft chancre”
a highly communicable
sexually transmitted genital
ulcer disease (GUD)
Haemophilus ducreyi
- most common site of infection is penis or labia
a suppurative (pus-
forming), enlarged, draining,
inguinal lymph nodes
Buboes
Haemophilus spp that can cause otitis media & acute sinusitis and is related to endocarditis: insidious onset
H. parainfluenzae
primary site of infection of H.parainfluenzae
Mitral valve
It is the recommended specimen for culture of the lower respiratory tract for h. influenzae organisms
Bronchial Washing
Additional Info
specimen processing in the laboratory should
occur soon after collection for maximum
recovery
Since:
- Haemophilus spp. dies rapidly in clinical specimens
- Haemophilus spp. are susceptible to
drying)
H. influenzae in chocolate agar
- incubated between 33° & 37° C
- growth after 18 to 24 h of incubation
in an atmosphere of 5% - 10% CO2 (high humidity)
It is an excellent medium for the
isolation of Haemophilus spp. from
respiratory specimens
- CA supplemented with bacitracin (300
mg/L) - Bacitracin: reduces overgrowth
of normal respiratory microbiota
What does the growth of tan mucoid colonies of H. influenzae in chocolate agar indicate?
- charcateristics of encapsulated strains
Special media for H. aegyptius is composed of :
- enriched CHOC agar supplemented with 1% Iso- VitaleX or Vitox
Special media for H. ducreyi is composed of:
- enriched CHOC medium, or Nairobi biplate
- grows best at 33° C
Characteristics of H.influenzae in Chocolate agar
- translucent, tannish, moist, smooth, &convex
- “mousy” or bleachlike odor
Characteristics of H.parainfluenzae and H. parahaemolyticus in Chocolate agar
- Tannish & drier with a medium to large size compared with H. influenzae
Characteristics of H. ducreyi in Chocolate agar
- small, flat, smooth, nonmucoid, transparent to opaque
colonies or appears tan or yellow
Haemophilus spp. do not grow on what medium
MAC agar
Microscopic morphology of H. influenzae in gram stain
- capsules are clear, non-
staining areas (“halos”) surrounding the organisms in purulent secretions - ## small pleomorphic stains “FAIINT PINK”
Due to the low specificity and sensitivity of Heamophilus in gram stain, these stains are used to help detect the latter
acridine orange & methylene blue stain
Microscopic morphology of H. ducreyi in gram stain
- singly or in groups (clusters)/“SCHOOL OF FISH ”or “RAILROAD TRUCKS”
- are loosely coiled clusters of organisms lined up in parallel or appearing as “FINGERPRINTS”
This can be the first clue to help indicate
that the organism being isolated is Haemophilus
- growth of gram (-) pleopmorphic coccobacilli on CHOC agar w/ NO growth on SBA and MAC agar in pure culture
- these 3 test must be done simultaneously
- satellitation can occur on SBA if it’s not pure culture
In laboratory identification, if a Haemophilus spp. requires both X and V factor for growth, what does it indicate?
- the organism growing is H. influenzae
In laboratory identification, if a Haemophilus spp. requires only V factor for growth, what does it indicate?
- the organism is identified as H. parainfluenzae or H. parahaemolyticus
In laboratory identification, if a Haemophilus spp. requires only X factor for growth, what does it indicate?
- the organism growing can be Aggregatibacter aphrophilus
- bcs this spp. can appear to be hemin dependent on initial isolation.
This is an alternative method for differentiating the heme-producing species of Haemophilus
Porphyrin test
Principle of Porpphyrin test
- is based on the ability of the organism to convert the substrate δ-aminolevulinic acid (ALA) into porphyrins or porphobilinogen (intermediates in
the synthesis of X factor)
In porphyrin test, porphobilinogen can be detected after 4hrs of incubation in 35° C through the addition of
- p-dimethylaminobenzaldehyde (Kovac rgt)
- (+ for porphobilinogen) = RED color forms [lower aqueous phase]
In porphyrin test, porphyrins can be detected using
- UV light: wavelength - 360 nm
- reddish-orange color under UV light
Advantage and Disadvantage of Porphyrin test
Advantage:
- X factor is not required and the problem of carryover is eliminated
Disadvantage:
- primary ID is based on a negative test result
Primary identification of Heamophilus spp. in porphyrin test is base on what result?
Negative result = presence of organism
-e.g., H. influenzae
negative = no fluorescence (UV light test) + no color change occurs after addition of the Kovacrgt
the recommended treatment of life-threatening illness caused by H. influenzae
- cefotaxime or ceftriaxone
alternative drugs
• trimethoprim-sulfamethoxazole
• imipenem
• Ciprofloxacin
Hamephilus shows increased resistance in this antimicrobial drugs
- Ampicillin (Should not be administered alone)
General characteristics of HACEK group
- include both fermentative and non-fermentative gram (-) bacilli
- fastidious
- ehnaced growth w/ CO2
- are opportunist & generally require a comprimised host
ACEK group
- ACEK more dysgonic (slow/ poor growing)
- important cause of endocarditis
Cardiobacterium is needs CO2 for growth thus they are considered as?
Capnophilic
Risk factors for Infective (bacterial) endocarditis
- tooth extraction
- history of endocarditis
- gingival surgery
- Heart valve surgery
- mitral valve prolapse
General characteristics of Aggregatibacter aphrophilus
- foam loving or desiring/ loves high conc. of CO2 (can grow w/out CO2 tho)
- linked to bone & joint infections
- found in dental plaque & gingival scrapings
A. aphropilus growing over the entire surface of Trypticase soy agar plate is due to what reason
- because they are not X factor dependent
General characteristics of Aggregatibacter actinomycetemcomitans
- has 6 serotypes (a-f)
- A, B, and C is the most common
- normal oral microbiota in humans
- require >24 hr for visible growth
- a distinctive “STAR SHAPE with four to six points” in
the center of the colonies is often seen at 48 h
Human tissue infection caused by A. actinomycetemcomitans is usually caused by
- bites by sheep, pigs, cattle, and horses or through contact with these animals.
Major virulence factors of A. actinomycetemcomitans
- Collagenase
- Leukotoxin (toxic to PMNs and monocytes)
Aggregatibacter spp. that is a major contributor to PERIODONTITIS
- A. actinomycetemcomitans
can cause destruction of the alveolar bone that
supports teeth
Biochemical test characteristic of A. actinomycetemcomitans
- catalase (+)
- Granular and adhere to sides of tube
- urease, indole, esculin, citrate (-)
- ## ferment glucose (+)
General characteristics of Cardiobacterium hominis
- nonmotile
- pleomorphic
- normal microbiota: nose, mouth & throat
- infection can lead to Endocarditis infecting the AORTIC VALVE
In Yeast extract Cardiobacterium hominis appear
- tend to form ROSETTES, swellings or sticklike structures
General characteristics of Eikenella corrodens
- normal biota: oral and bowel cavities
- cause of ADULT periodontitis, meningitis,
empyema, pneumonia, osteomyelitis, arthritis, &
postoperative tissue infections
Eikenella corrodens manifest as ________ in drug addicts
Cellulitis
Biochemical test characteristic of Eikenella corrodens
- catalase (-)
- oxidase (+)
- nonmotile
- YELLOW PIGMENT
- “PIT” (make a depression) or CORRODES the surface of the agar
- CHLORINE BLEACH–like odor from the agar surface adhere to the sides of the tube & produce
granules
General characteristics of Kingella spp.
- important pathogens in the PEDIATRIC population
- the most common cause of OSTEOARTHRITIS infection in children younger than 4 years of age
Biochemical test characteristic of Kingella spp.
- resist decolorization in gram stain
- oxidase (+)
- catalase (-)
- fermenters of glucose and other sugars but w/ no gas
- susceptible to penicillin
Kingella shares resemblance with this organism in MTM agar
- Neisseria gonorrhoeae
Kingella can grown in SELECTIVE agar such as
- MTM or modified thayer- martim medium
