HRR: gram negative rods Flashcards
What is the shape and growth characteristics of Corynebacteria?
Corynebacteria are club-shaped, do not form spores, and exhibit aerobic growth on blood agar.
What kind of colonies do corynebacteria form?
Corynebacteria form non-hemolytic colonies.
Where can corynebacteria be found?
Corynebacteria are found as commensal flora on the skin, often referred to as diphtheroid.
What is the virulence factor of corynebacteria?
The virulence factor is diphtheria toxin, which ADP ribosylates EF-2, blocking tRNA and thus protein synthesis.
What encodes the DT gene?
The DT gene is encoded by a lysogenic bacteriophage.
How is diphtheria toxin regulated by corynebacteria?
It is regulated by the corynebacterium repressor protein (DtxR), influenced by iron levels; low iron increases toxin production, while high iron decreases it.
How is corynebacteria acquired?
Corynebacteria are acquired through inhalation of respiratory droplets.
How can corynebacteria be prevented?
Corynebacteria can be prevented with DTP/DTAP vaccines.
What is the clinical presentation of corynebacteria?
Corynebacteria are not invasive but can cause local and systemic effects of diphtheria, including fever, malaise, laryngitis, necrosis of oropharyngeal epithelial cells, and toxin-mediated myocarditis.
How is corynebacteria diagnosed?
Diagnosis is primarily clinical; cultures are sent to reference labs for assay.
How is diphtheria treated?
Diphtheria is treated with erythromycin and antitoxin (antibodies against DT). Skin infections may require antibacterial cleansers.
What are the presentations of non-diphtheriae corynebacteria?
Non-diphtheriae corynebacteria typically cause minor skin infections.
What is the shape and growth characteristics of Listeria?
Listeria are curved, beta-hemolytic on blood agar, catalase positive, can grow at refrigerator temperatures, and have flagella.
How is listeria acquired?
Listeria is usually acquired through unpasteurized dairy or cold cuts.
What happens if a pregnant person contracts listeria?
Transplacental and intrapartum infection can occur.
What is the clinical presentation of listeria?
In most people, there are no symptoms; in the elderly, pregnant, or immunocompromised, listeria can cause meningitis and encephalitis.
How is listeria diagnosed?
Listeria is diagnosed through blood and CSF culture.
What are the virulence factors of listeria?
Virulence factors include intracellular growth, survival in macrophages, listerolysin O, and the actin tail.
What is internalin?
Internalin induces the uptake of listeria by host cells.
Describe listeria immunity.
Listeria immunity involves innate and adaptive immunity; cytokines and gamma interferon halt intracellular growth.
How is listeria treated?
Listeria is treated with ampicillin and TMP/SMX.
What are listeriae resistant to?
Listeriae are resistant to cephalosporins.
What is the shape and growth characteristics of Bacillus?
Bacillus are rod-shaped, spore-forming, and exhibit aerobic growth.
What is the infectious form of bacillus?
The infectious form of bacillus is the spores, which are highly resistant to inactivation.
How are we infected with bacillus?
Infection can occur through inhalation, skin contact, or ingestion.
What is the main threat of bacillus to humans?
Bacillus can be a bioterror agent.
What are the virulence factors of bacillus?
Virulence factors include an anti-phagocytic capsule and a tripartite exotoxin.
Describe the exotoxin in bacillus.
The exotoxin has a protective PA component, an EF component that causes edema, and an LF component that kills cells.
Describe cutaneous anthrax.
Cutaneous anthrax manifests as a painless papule that progresses to an ulcer with edema and a black center.
Describe pulmonary anthrax.
Pulmonary anthrax occurs after inhaling bacillus spores, leading to fever, cough, mediastinal edema, cyanosis, bacteremia, meningitis, and potentially death.
Describe intestinal anthrax.
Intestinal anthrax results from ingesting bacillus spores, causing painful edema and necrosis.
Describe bacillus cereus.
Bacillus cereus produces enterotoxin that causes food poisoning or ocular infection.
How is bacillus diagnosed?
Diagnosis is made through culture of skin lesions, sputum, blood, and CSF.
What does bacillus anthracis look like?
Bacillus anthracis appears as long chains of non-hemolytic, non-motile rods.
What does bacillus cereus look like?
Bacillus cereus is beta-hemolytic and motile.
How can we treat bacillus?
Cutaneous bacillus infections can be treated with doxycycline or ciprofloxacin, but pulmonary and intestinal anthrax are difficult to treat.
How do we prevent bacillus?
Prevention includes ciprofloxacin if exposure is suspected and the beta anthracis vaccine, usually for military personnel.
