LECTURE Flashcards
first isolated by Pfeiffer in 1890; waserroneously named during the influenza pandemic that ravaged the world from 1889 to 1890
Haemophilus influenzae
The basis for this assumption was the frequent isolation of this bacillus from the [?] of patients with influenza and from [?] during those times when viral isolation methods were unavailable.
nasopharynx; postmortem lung cultures
secondary (opportunistic) invader
H. influenzae
Influenza, commonly referred to as the flu is a viral disease characterized by [?] of the upper airways.
acute infammation
intense infammation of the mucous membranes lining the nose
(coryza)
severe generalized muscle pain
(myalgias)
require special nutrients for isolation and identification
fastidious
special nutrients that are often supplied by addition of enrichment ingredients to culture media
growth factors
Species in the genus Haemophilus require [?] for optimal growth
Factor X and/or Factor V
Bordetella species, on the other hand, require
niacin (also known as nicotinic acid, a form ofvitamin B3), cysteine, and usually methionine.
Brucella species require
thiamine, niacin, and biotin.
Most bacteria included in this group are [?] or produce [?] infections.
nonpathogenic
opportunistic
General Characteristics
•Small, pleomorphic, gram-negative bacilli. The cells are typically coccobacillary or short rods.
•Nonmotile.
•Facultative anaerobes.
•Growth is enhanced in a 5% to 10% CO2-enriched atmosphere. •Are “blood-loving”
Haemophilus species
requiring enriched media, usually containing blood or its derivatives, that provide preformed growth factors, X and V; isolation usually requires the presence of X and/or V factor in the culture medium.
blood-loving
- Protoporphyrin IX which acts physiologically as hemin or hematin
Factor X
- An important component of cytochromes, catalase, and peroxidase.
Factor X
- Heat-stable and is frequently supplied by the incorporation of heat-lysed (“chocolatized”) blood cells in agar such as in chocolate agar or Fildes medium.
Factor X
- Nicotinamide adenine dinucleotide (NAD) or NAD phosphate (NADP).
Factor V
- Heat-labile and is commonly supplied by the incorporation of yeast extract or other appropriate supplements in the medium
Factor V
- May also be provided by a suspension of hemolytic strains of bacteria (e.g., staphylococci, pneumococci, and neisseriae)
Factor V
Pfeiffer’s bacillus
Haemophilus influenzae
Haemophilus influenzae: CHARACTERISTIC
Requires both X and V factor for growth
Haemophilus influenzae: HABITAT
- only in humans
- upper respiratory tract (oropharynx and nasopharynx) of 20% to 80% of healthy persons
Haemophilus influenzae: TRANSMISSION
person- to-person by respiratory droplets
Strains of H. influenzae are divided into 2 broad groups based on
capsular polysaccharides
These are encapsulated strains of H. influenzae which are separated into one of six groups: type a, b, c, d, e, or f; all have potential to invade deeper tissues.
Typeable strains
90% of invasive H. influenzae infections are caused by .
serotype b (Hib) strains
Haemophilus influenzae [?] is most commonly encountered in serious infections in humans which include meningitis esp. in
infants and children; and several other diseases such as epiglottitis and bacteremia.
serotype b (Hib) strains
They do not produce capsule.
Nontypeable strains
These are most commonly encountered as normal inhabitants of the upper respiratory tract of man; but
may cause mild localized infections (otitis media and sinusitis in children), and is associated with respiratory
tract infections (pneumonia).
Nontypeable strains
Until the availability of the Hib vaccine, H. influenzae was the most common cause of meningitis in children between [?] of age when nearly all passive immunity has waned, and the child enters a vulnerable non immune period of life. Although, it is still a problem if a child is [?] and not vaccinated.
3 months and 6 years
<2 years
Older children, adolescents and adults can less frequently be infected particularly those who are immunocompromised.
Meningitis
Meningitis by H. influenzae has very similar presentation with [?], with symptoms of fever, malaise, occasionally vomiting, stiff neck and neurological impairment. Untreated cases have [?] (up to 90%) even with prompt diagnosis.
meningococcal meningitis
high fatality
H. influenzae is the most common cause of this potentially fatal disease in children between the ages of 2 and 4
Epiglottitis
It has a rapid onset, with sore throat, dysphagia, fever, and swollen, cherry red epiglottis above the larynx at the base of the tongue.
Epiglottitis
Acute inflammation and intense edema of the epiglottis may cause complete [?] and [?]
airway obstruction and suffocation
can be “cherry red” in children; “thumb sign” on lateral neck x-ray
Epiglottitis
is an early manifestation of acute H. influenzae type b meningitis but in some infants, may occur without meningitis
Bacteremia
It is mostly seen in children with underlying diseases (e.g., sickle cell); signs and symptoms include fever, lethargy and high neutrophil count
Bacteremia
are second to S.pneumoniae as a common cause of otitis media in children, most frequently in children aged 6 months to 5 years with highest incidence among children less than 3 years of age
H. influenzae (nontypeable strains)
Signs and symptoms include fever, irritability, headache, occasionally nausea and vomiting, ear pain, hearing loss, discharge from the ear.
Otitis media
It is characterized by persistent cold symptoms, purulent nasal or post nasal discharge, cough, fever, headache, and often facial pain.
Sinusitis
In adults, H. influenzae causes pneumonia, particularly in individuals with other underlying pulmonary infections. It can be a manifestation of systemic infections caused by H. Influenzae type b.
Pneumonia
— lobar, segmental and purulent pneumonia.
pneumococcal pneumonia
Its characteristics are similar to pneumococcal pneumonia
Pneumonia
Hib capsule is a polysaccharide, called PRP
polyribosylribitol phosphate
It is the most important factor of H. influenzae because it allows the organism to resist phagocytosis and intracellular killing by neutrophils and the complement.
Capsule
This molecule consists of the 5-carbon monosaccharide ribose, linked by an ester bond to ribitol, and a 5-carbon sugar alcohol, which, in turn, is linked to a phosphate group.
polyribosylribitol phosphate
the only capsular type that contains two pentose monosaccharides rather than hexose sugars as subunit carbohydrates.
H. influenzae serotype b polysaccharide
promotes phagocytosis and complement-mediated bacteriolysis.
Anticapsular (anti-b) antibodies
H. influenzae is the only member of the genus that produces [?], an enzyme that cleaves secretory IgA present on human mucosal surfaces of the respiratory tract, thus allowing the bacteria to attach to these surfaces.
IgA protease
They favor attachment of the nontypeable strain of H. influenzae to host epithelial cells.
Pili
Each component is responsible for invasiveness, attachment, and antiphagocytic function.
Outer Membrane Proteins
of H. inluenzae has been shown to have a paralyzing effect on the sweeping motion of ciliated respiratory epithelium.
LPS
Antibodies directed against these antigens may play a significant role in human immunity.
Outer Membrane Proteins
Organisms attach to epithelial cells using [?] and [?]
pili and outer membrane proteins (OMP)
Invasion takes place between cells by disruption of [?]. In the submucosa, the [?]allows the bacteria to evade phagocytosis and enter the bloodstream
cell–cell adhesion molecules
capsule
H. influenzae type b (Hib) disease: PREVENTION
vaccination
PRP, like most bacterial polysaccharides, elicits a strong [?], but with little induction of memory.
primary antibody response
[?], which covalently link the polysaccharide to a protein, induce memory type antibody responses in children and are effective in younger infants who are at higher risk for the disease
H. influenzae type b (Hib) conjugate vaccines
PRP-OMPC
PRP-T
PRP-D
HbOC
Neisseria meningitidis outer membrane protein complex
Tetanus toxoid
Diphtheria toxoid
CRM197 mutant Corynebacterium diphtheriae toxin protein
• Hib conjugate vaccines are commercially available as:
‣ Monovalent vaccine
‣ Combination vaccine
(containing a single antigen only — Hib PRP)
‣ Monovalent vaccine
(consists of two or more vaccines given in one
shot — Diphtheria, Pertussis, Tetanus, HBV, Hib)
‣ Combination vaccine
• Depending on which vaccine product is chosen, the series consists of three doses at [?] of age or two doses given at [?] of age. An additional booster dose is given sometime between 12 and 15 months of age.
2, 4, and 6 months
2 and 4 months