Other Gram-negative Rods Flashcards
(35 cards)
What do all gram negative rods have in common❓
- Gram -ve cell envelop
- Lipopolysaccharides LPS (virulence factor)
- Aerobic- cause infection in sites of high oxygen tension eg lungs
Mention one way gram negative rods can be classified
1. Primary pathogens of human respiratory tract: Haemophilus Bordetella Legionella
- Opportunistic pathogen:
Pseudomonas
3. Primary pathogens of animals: Brucella Francisella Pasteurella
What do you know about haemophilus influenza❓
It is pleomorphic
It has a capsule (virulence factor)
Pathogen of young children
Illnesses are sporadic in occurrence
Normal component of upper respiratory tract flora (conjunctiva, genital tract)
Haemophilus influenza…
- Is transmitted by❓
- Can cause which diseases❓
- Respiratory droplets
2. If colonization occurs in respiratory tract: Otitis media Sinusitis Epiglottitis Bronchopneumonia
If it invades the bloodstream and localizes in other areas of the body:
Meningitis
Septic arthritis
Cellulitis
Haemophilus influenza is the leading cause of bacterial meningitis
True or false❓
True
Clinically H. influenza meningitis is indistinguishable from other purulent meningitides
True or false
True
How would you diagnose an infection caused by H.influenza❓
Culture on chocolate agar
Isolation from sterile sites eg blood, CSF, synovial fluid
In meningitis: gram staining of CSF reveals: Pleomorphic Gram -ve coccobacilli Capsule (capsular swelling/quellung rxn/immunoflourescence staining)
Capsular antigen may be detected using:
Latex agglutination
Countercurrent immunoelectrophoresis
Radioimmune assay
While diagnosing a case of H. influenza infection, isolation from pharyngeal cultures may be inconclusive
True or false❓
Why❓
True
H. influenza is found normally around the respiratory tract
How can you prevent an infection caused by H.influenza❓
Immunization <2yrs (type B)
Rifampin for individuals in close with infected pt
Bordetella pertussis causes which disease❓
Small
Encapsulated coccobaccili
Grow singly or in pairs
- What disease does bordetella pertussis cause❓
- How is transmitted❓
- In the absence of Immunization, it is most common in which age group❓
- What is the incubation period of B. pertussis❓
Whooping cough
Droplets via coughing
Ages 1-5
1-3weeks
Describe the pathogenesis of infections caused by bordetella pertussis
Binds to ciliated epithelium in URT ⬇️ Production of toxins and other virulent factors ⬇️ Interference with ciliary activity ⬇️ Death of cells
The disease can be divided into phases, what are they❓
Catarrhal Phase: Fever/Malaise Rhinorrhea Mild conjunctivitis Dry/non-productive cough
Paroxysmal Phase:
Exacerbated cough followed by whoop w large mucus production
Convalesce Phase (3-4weeks, severe in infants)
How can an infection by B. pertussis be
- Prevented❓
- Diagnosed❓
- Treated❓
- Vaccine (DPT) at 2months old
2.
Clinical presentation
Culture from nasopharynx in a selective agar medium (pinpoint colonies in 3-6 days) has
Direct fluorescent antibody test
Serologic antibody test
2. Erythromycin 🚫 ⬇️ Trimethoprim-Sulfamethoxazole
Describe the legionella genus
*Cells are unencapsulated
Coccobacillary in shape
Facultative intracellular species
Aerobic and fastidious
*Require L-cysteine
Cause primarily respiratory tract infections
An infection by Legionella is an atypical, acute lobar pneumonia with multisystem symptoms.
- How can it be acquired❓
- What are it’s two distinct presentations❓
- Has an incubation period of❓
- Can be diagnosed by❓
- Can be treated using❓
- Aspiration of water containing legionella
Inhalation of contaminated aerosol
- Legionnaires diseases
Pontiac Fever
2-10days
- Culture:
Respiratory secretions using buffered charcoal yeast (pH 6.9), L-cysteine and iron
Visible colonies in 3-5days
Urinary antigen test
- Erythromycin/Azithromycin
Fluoroquinolones
🚫antibiotics for Pontiac fever
Describe pseudomonas aeruginosa
Motile (polar flagella)
Encapsulated
Obligate aerobe
⬇️Nutritional requirements
Ubiquitous
Opportunistic pathogen (found in immunocompromised pt)
Causes nosocomial: Pneumonia, UTI, Surgical site infections, Severe burn infections, Infection of chemotherapy/antibiotics therapy patients
Describe the pathogenesis of infections caused by pseudomonas aeruginosa
Attachment to tissue (pili)
⬇️
Colonization of tissue (capsule prevents removal by normal clearance mechanisms)
⬇️
Damage (toxins promote invasion and dissemination)
Infections reflecting systemic spread of P. aeruginosa include❓
Why is there a complication in choice of therapy for P. aeruginosa infections❓
1.
Bacteremia
Secondary pneumonia
Bone and joint infections
Endocarditis
CNS/Skin/Soft tissue infections
- It is often antibiotic resistant
How can infection by pseudomonas aeruginosa be identified❓
How can it be treated❓
1.
Fruity odor at bedside/lab
Isolation in blood/MacConkey agar
Serologic typing
- Aggressive antimicrobial therapy
Describe the brucella genus
Zoonosis; B. ovis causes disease in man
Unencapsulated*
Small coccobacilli
Arranged singly or in pairs
LPS (virulence factor)
Aerobic
Facultative
Intracellular parasites
How can infection by B. ovis be identified❓
How can it be treated❓
- •Detailed history/Patients occupation/Exposure to animals/Food intake
•Culture (examine for up to one month)
Plated materials: colonies in 4-5days Blood: relatively longer
- Doxycycline and Gentamycin/Streptomycin
Prolonged treatment (6 weeks) to prevent relapse
Describe the pathogenesis of B. Ovis infection
Gain of entry (cuts/abrasions in skin/GI)
⬇️
Transport via lymphatic system
⬇️
Multiplication in regional lymph nodes
⬇️
Transmission to organs of reticuloendothelial system
- What disease does B. ovis cause❓
- How is transmitted❓
- What is the incubation period of B. pertussis❓
1.
Undulant Fever
2.
Contact with infected tissue
Ingestion of unpasteurized milk
Inhalation of infected aerosols
5 days to several months
