WEEK 10: FASTIDIOUS GRAM-NEGATIVE BACILLI Flashcards
HACEK
(Haemophilus parainfluenza, Aggregatibacter,
Cardiobacterium, Eikenella and Kingella)
) causing SBE
(subacute bacterial endocarditis)
HACEK
- Derived from the Greek word “blood-lover”
HAEMOPHILUS
- Non-pathogenic or produce opportunistic infections
- 10% of the microbiota of the upper respiratory tract
HAEMOPHILUS
what are heamophilus’ * Require performed growth factors present in the blood:
o X Factor (hemin or hematin; X for unknown) – used in
the synthesis of catalase, peroxidase, and in the
cytochrome electron transport system
o V Factor (nicotinamide-adenine dinucleotide (NAD); V
for vitamin) – NAD is a co-enzyme that transfers
electrons from one reaction to another
o Both are additives
o Both are found inside RBCs, but only X factor is directly available
o Haemophilus species with the prefix para- only
require V factor for growth
is haemophilus capnophilic?
yes . they requires 5-10% CO2
– for culture of lower respiratory tract
Bronchial washing
Direct plating on selective media at the bedside is preferred
Haemophilus spp. fast drying kasi sila
- Small, gram-negative coccobacilli to long filaments
HAEMOPHILUS
stain that help in
detecting Haemophilus spp.
Acridine orange or Methylene blue stain –
- Haemophilus spp. will not grow on
MAC agar and SBA
Produce a “clumpy” nonhomogeneous appearance when
suspended in saline
HAEMOPHILUS
Use of impregnated strips or disks – for dentification of
Haemophilus spp. and some of the Aggregatibacter spp
Carryover may produce erroneous or less than definitive
results causing H. influenzae to be misidentified as
H. parainfluenzae
WHICH REQUIRES V FACTOR, X FACTOR AND NEITHER
- H. influenzae
- H. parainfluenzae
- A. segnis
- H. influenzae – requires both X and V factors
- H. parainfluezae – requires V factor only
- A. segnis – requires only V factor, oxidase negative
- Haemophilus Quad Plate
o Four zones: media with X factor only, V factor only, X
and V factors, and X and V factors with horse red
blood cells
as a substrate to synthesize
heme factor, in the process porphyrins are created
* Performed in agar, in broth, or on a disk
delta
aminolevulinic acid (ALA)
principle of porphyrin test
Principle: Based on the ability of the organism to convert
the substrate ALA into porphyrins or porphobilinogen,
which are intermediates in the synthesis of X factor
how is porphoblinogen detected
Detected by the addition of Kovacs reagent after 35°C for 4 hours incubation
o Red color forms in the lower aqueous phase
o Kovacs reagent (p-dimethylaminobenzaldehyde)
0.5mL for inoculation
how is porphyrin detected
Detected using an ultraviolet light with a wavelength
of about 360 nm (Wood’s lamp)
o Reddish-orange or pink fluorescence form under UV
light
o Much more accurate means of determining X factor
requirement compared to X and V factor disks
o Advantage: X factor is not required (no carryover)
o Disadvantage: Primary identification is based
on a negative test result
porphyrin test result
negative poprphyrin = x factor positive
= BLUE
(uv is negative, no flourescence, no color change in addition of kovac, cant make heme)
porphyrin positive = x factor negative
= PINK
kabaliktaran
btw di naman need heme
Hemolysis is determined on HBA since it cannot
hemolyze sheep’s blood
Satellitism
Stabbing the area of inoculation
enhances the hemolytic
reaction
occurs when an organism such as
Staphylococcus aureus, Streptococcus pneumoniae, or
Neisseria spp. produces V factor as a byproduct of
metabolism (they obtain V factor from the SBA)
Satellitism