Gram - Part 3 Flashcards
Has multiple flagella at one pole and is actively motile.
Helicobacter pylori
Grows in 3–6 days when incubated at 37°C in a microaero-
philic environment
H pylori
Media for primary isolation of H pylori
• Skirrow’s medium with
vancomycin, polymyxin B
• trimethoprim, chocolate medium
Translucent colonies
H pylori
- oxidase positive
- catalase positive
- motile
- a strong producer of urease.
H pylori
Optimal pH H pylori grows.
6.0-7.0 pH
Not grows at the pH within the gastric lumen
H pylori is found:
Deep in the mucous layer near epithelial surface where physiologic pH is present
Produces protease that modifies the gastric mucus and reduces the ability of acid to diffuse through the mucus
H pylori
Organism that yelds in the production of ammonia and buffering of acid
H pylori
Acute symptoms of infection of H pylori may last for
1-2 weeks
H pylori is also a risk factor for
Gastric carcinoma and lymphoma
Determination of serum antibodies in H pylori infection
Blood
Gastric biopsy specimens can be used for histologic examination or
minced in saline and used for culture.
H pylori
May be collected for H pylori antigen detection
Stool samples
Required for diagnosis of H pylori infection
Gastroscopy
Demonstrates in routine stains of H pylori infection
Gastritis
can show the curved or spiral-shaped organisms
Giemsa or special silver
stains H pylori
performed when patients are not responding to treatment,
and there is a need to assess susceptibility patterns.
Culture for H pylori
Persist even if the H pylori infection is
eradicated, and the role of this in diagnosing active infection or after therapy is therefore limited.
Serum antibodies
Used to detect urease activity are widely used for presumptive identification of H pylori in specimens.
Rapid tests
Test that will result if H pylori is present, the urease activity generates labeled CO2 that can be detected in the patient’s exhaled breath.
Urea breath tests
Appropriate as a test of
cure for patients with known H pylori infection who have been treated.
Stool specimen
Eradicates H pylori infection in 70–95% of patients
Triple therapy with metronidazole and either bismuth subsalicylate or bismuth subcitrate plus either amoxicillin or tetracycline for 14 days
enhances ulcer
healing in H pylori infection
Acid-suppressing agent given for 4–6 weeks
Directly inhibit H pylori and appear to
be potent urease inhibitors.
Proton pump inhibitors (PPIs)
The preferred initial therapy of H pylori infection
7–10 days of a PPI plus amoxicillin and
clarithromycin or a quadruple regimen of a PPI metronidazole, tetracycline, and bismuth for 10 days
At 6–8 hours in rich medium, the small coccobacillary forms predominate.
• Later, there are longer rods and very pleomorphic forms.
Haemophilus influenza
Used for the capsule of Haemophilus influenza
Typing H influenza
Culture demonstrate flat, grayish, translucent colonies with diameters of
1–2 mm are present after 24 hours of incubation of Haemophilus influenza
Chocolate agar
Does not grow on sheep blood agar except around colonies of staphylococci (“satellite phenomenon”)
H influenzae
Identification of organisms of the Haemophilus group depends partly
on demonstrating the need for certain growth factors called
X and V
Acts physiologically as hemin
Factor X
Factor that can be replaced by nicotinamide adenine dinucleotide (NAD) or other coenzymes
Factor V
Contains capsular polysaccharides of one of six types (a–f)
Encapsulated H influenza
A type of capsular antigen is a polyribitol ribose phosphate (PRP).
Type B
Can be typed by slide agglutination,
coagglutination with staphylococci, or agglutination of latex particles coated with type-specific antibodies
Encapsulated H influenzae
Normal microbiota of the upper
respiratory tract are not encapsulated and are referred to as nontypeable
(NTHi).
Most H influenzae
The somatic antigens of H influenzae consist of
outer membrane proteins
Produces no exotoxin
H influenzae
The major virulence factor of H influenzae
Polyribose phosphate capsule of type b
Most common etiologic agents of bacterial otitis media and acute sinusitis.
H influenzae, mostly nontypeable, and pneumococci
Before the use of the conjugate vaccine, it was the most common cause of bacterial meningitis in children aged 5 months to 5 years in the United States.
H influenzae type B
Available for immunologic detection of H
influenzae antigens in spinal fluid
Commercial kits
Specimens of H influenzae are grown on
IsoVitaleX-enriched chocolate agar
H influenzae is differentiated from related gram-negative bacilli by
its requirements for X and V factors and by its lack of hemolysis on blood agar
The Haemophilus species that require this grow around paper strips or disks containing V factor placed on the surface of agar that has been autoclaved before the blood was added
V factor (heat liable)
A strip containing this can be placed in parallel with one containing V factor on agar deficient in these nutrients
X factor
Susceptible to ampicillin, but up to 25% produce a β-lactamase under control of a transmissible plasmid and are resistant.
Many strains of H influenzae type B
All strains of H influenzae is susceptible to
third-generation cephalosporins and carbapenems
Treatment for H influenzae that is given intravenously
Cefotaxime
