Section 1: Aerobic Gram Negative Coccobacili Flashcards
What are the characteristics of Haemophilus sp.
Small
Normal flora of the upper respiratory tract
What are the growth requirements of Haemophilus
Heme, a building block of hemoglobin
X factor-component ofblood called hemin
V factor-either NAD or NADP
In lab Haemophilus is grown on chocolate blood agar
What are the two groups Haemophilus influenzae is split into
1: Encapsulated or typeable strains
2: Non encapsulated or nontypeable strains
What is the epidemiology of Haemophilus influenzae
Transmitted in respiratory secretions.
Usually non encapsulated strains are part of the normal flora
• However, a minority (3-7%) of healthy individuals harbor Hib in the upper respiratory tract
What is the pathogenesis of Haemophilus influenzae
Meningitis
Epiglottitis
Pneumonia
What is meningitis
Leading cause of acute meningitis in children (until widespread vaccination program began in 1985)
• Regional lymph nodes and meninges are infected • Bloodstream can be infected = bacteremia
• Serious neurologic sequelae (abnormal condition following or related to a previous disease) frequently develop and persist after recovery from meningitis
What is epiglottitis
Infection of the epiglottis characterized by swelling
• Pediatric illness which can be life-threatening emergency
• Symptoms include, rapid progression, high fever, drooling, inspiratory strider, and difficulty breathing when supine
• Since the advent of the Hib vaccine the disease is seldom seen
What is Pneumonia
Seen in adult debilitated, imrnunocompromised patients
How is Haemophilus influenzae diagnosed
Microscopy Serotyping Culture on chocolate blood agar Agglutination testing Culture on blood agar with Staphylococcus aureus
How is Haemophilus influenzae prevented
Until 6 mos. of age infant is protected by maternal antibodies
In 1985 first Hib conjugate vaccines licensed for use
• All children should have vaccine approved for infants at 2 mos o Children older than 60 mos. and adults do not need to be vaccinated
What is Haemophilus ducreyi
Causative agent of the sexually transmitted infection (STI), chancroid
-After an incubation period of one day to two weeks, begins with a small bump on the genitalia that becomes an ulcer within a day of its appearance
How is Haemophilus ducreyi diagnosed
Obtain smear from genital ulcers and culture on chocolate blood agar
Rule out other STis
What is often seen in the inguinal regions of patients with Haemophilus ducreyi
Patients often have adenopathy (swollen lymph nodes) in the inguinal area
What is the characteristic of the Haemophilus ducreyi ulcer
The ulcer characteristically:
• is painful
• has irregular or ragged borders
• is soft and has a base that is covered with a yellowish-grey material
Men typically have 1 ulcer, while females have multiple ulcers
What is Haemophilus vaginalis
aka Gardnerella vaginalis
• Part of normal vaginal flora
• Sometimes causes mild infection
How is Haemophilus vaginalis diagnosed
Gram stain reveals “clue cells”
• Identified as numerous stippled or granulated epithelial cells
• Characteristic of H. vaginalis infection
What is Bordetella pertussis
Capsule
- Three serotype based on capsular antigens have been identified
- Nutritionally fastidious, cultivated on rich media supplemented with blood
- Do not require X and V factors
- Causative agent of pertussis (whooping cough)
What are the virulence factors of Bordetella pertussis
Pertussis Toxin Filamentous Hemagglutinin extracellular adenylate cyclase endotoxin Strain reversion
What does the buildup of cAMP from Bordetella pertussis lead to
Increased insulin production, resulting in hypoglycemia
• Increased sensitivity to histamine, resulting in increased capillary permeability, hypotension, and shock
• Inhibition of monocytes migrating into tissue
What is Filamentous Hemagglutinin
Large protein that forms filamentous structures on the cell surface that bind to the ciliated host cells allowing colonization of host tissue
What is extracellular adenylate cyclase (TOXIN)
B. Pertussis secretes invasive adenylate cyclase which enters host cell and acts locally to reduce phagocytic activity, particularly of neutrophils
What is Strain reversion
Transposon mutagenesis can result in a virulent strain (phase I) becoming non-virulent (phase IV)
• Phase N strain can revert (lose the transposon) and become virulent
What is the epidemiology of Bordetella pertussis
Found worldwide
-Primarily infects children under 6 mos.
• Droplet transmission
• Incubation period is 7-10 days
-Pertussis once the most common disease of childhood
-Often fatal, particularly in infants
What are the pathological stages of Bordetella pertussis
Catarrhal stage
Paroxysmal stage
What occurs during the Catarrhal stage of Bordetella pertussis infection
Colonization of the upper respiratory system
• Characterized by fever, malaise and coughing
• B. pertussis is recovered in large numbers from pharyngeal cultures
• If diagnosed in this stage the severity and duration of the disease can be reduced by antimicrobial treatment
What occurs during the Paroxysmal stage of Bordetella pertussis infection
-Follows relatively nonspecific symptoms of catarrhal stage
• Begins gradually with prolonged and paroxysmal coughing that ends in a characteristic inspiratory gasp
How is Bordetella pertussis diagnosed
Swab nostrils
• Culture on selective media (Bordet-Gengou)
• Serum agglutination
• Fluorescent antibody testing
How is Bordetella pertussis prevented
Whole cell vaccine
Acellular vaccin -fewer side effects
How are Brucella species named
for the animal they infect
What is the epidemiology of Brucella
Human brucellosis is a true zoonosis in that all infections are acquired from animals.
- Brucella penetrates the skin and mucosa o In animals the microbe typically affects the reproductive organs and is contracted by humans via contaminated milk
- Brucellosis is rare in the United States, 100 to 200 cases occur each year.
- Brucellosis can be very common in countries where animal disease control programs have not reduced the amount of disease among animals
What is the pathogenesis of Brucella
- Microbes spread via lymphatic system and multiply in phagocytes (obligate intracellular)
- Cause lesions in various organs including: liver, spleen, bone marrow, kidney
What are the symptoms of Brucella
fever, unusually severe limb and back pain, marked fatigue
How is Brucella diagnosed
Primarily Dependent on cllinical findings
-Grows poorly in culture and may need to be incubated for up to 4 weeks
How is Brucella controlled
Immunize cattle sheep and goats.
- Live attenuated vaccines have reduced brucellosis in domestic animals
- Pasteurization of milk
- Protective clothing for those occupationally exposed
What are the characteristics of Francisella tularensis
- small
- Gram negative
- Pleomorphic= rod, coccobacilli, filament-like
- Non-motile
- Very thin capsule composed of lipids
- Pathogenic strains possess capsule, loss of or lack of capsule is associated with decreased virulence
- Causative agent of tularemia (aka-glandular fever, rabbit fever, tick fever, and deer fly fever) •
What are the 2 strains of Francisella tu/arensis
Type A strain= Francisella tularensis var tularensis causes tick-borne tularemia in rabbits, and produces classic disease in human beings
-Type B strain = found predominantly in Europe and Asia, rarely leads to fatal disease
What is the epidemiology of Francisella tu/arensis
-Disease of mammals, fish, birds, and invertebrates
-Primary vector is infected ticks, sometimes deer flies
-Humans are infected by
• Direct contact with animal (hunters)
• Bite from infected tick or fly
• Contaminated food or water
What is the pathology of Francisella tu/arensis
- Initial symptoms oftularemia develop after 3-5 day incubation period
- Fever, chills, malaise, fatigue
How many microbes can cause Francisella tu/arensis
Highly infectious, as few as 10-50 microbes can cause disease
What are the subtypes of Tularemia
Ulceroglandular tularemia
Pneumonic tularemia
Oculoglandular tularemia
Typhoidal tularemia
How is Francisella tu/arensis diagnosed
- Clinical history
- Isolation in culture-must be grown on chocolate agar (sometimes blood agar). Requires incubation times of 1-2 weeks
- Agglutination tests
- Fluorescent antibody test
How is Francisella tu/arensis prevented
-Avoid reservoirs and vectors of infection (rabbits, ticks, flies)
-Wear gloves when processing animals
-Prompt removal of ticks-F. tularensis present in feces, not saliva. Tick must feed for prolonged period to transmit infection -
Live attenuated vaccine is available
• Treatment
• Not completely effective in preventing disease, but can lessen severity of the disease
• Recommended for people at a significantly increased risk of exposure
