Gram negative coccobacilli, Brucella, Francisella, Pasteurella, Yersinia, Bordatella Flashcards
(30 cards)
What are the genuses of Gram negative Coccobacilli
Haemophilus and Bordetella
H. influenzae
H. parainfluenzae
H. aegyptius
H. ducreyi
B. pertussis
B. parapertussis
Haemophilus influenzae
Morphology
Culture
A Gram negative cocco-bacillus (long), 1.5uM coccobacilli in pairs mostly or short chains.
is a fastidious bacteria: this blood loving (heamophil) bacteria requires factor X, Heme and factor V, NAD in its medium. So it must be grown on chopped-meat enriched chocolate agar.
Or it can be grown as a satellite colony around a Staphylococcus aureus streak
facultative anaerobe.
Catalase: negative
Oxidase: negative
Urease: positive
Colonies: tiny clear colonies in blood S. a satellite culture, small gray colonies on chocolate agar.
UsingSims-discs on simple agar. They grow near factors X+V, but not X or V alone.
Haemophilus influenzae, Virulence factors
Capsule, serotypes a-f -
capsule b = bad H.i b is the most common invasive type which causes severe disease in children.
There is a childhood vaccine against the type b
There are also many species of uncapsulated H. influenzae and these must be identified by geneotype. Unencapsulated forms are much less invasive and cause only local infections. Are often opportunistic infections in patients already suffering from other respiratroy disease.
IgA protease
Surface antigens: OMPs, outer membrane proteins and LPS
Hemolysins
Cytolethal distending toxin (CDT) -
Heamophilus influenzae
Habitat
Transmission
An obligate pathogen
Reservior is the human respiratory system and nasopharynx
Transmitted via respiratory droplets
Heamophilus influenzae
Clinical diseases
Diagnosis
Upper respiratory infections:
Nasopharyngitis, Sinusitis,
Epiglottitis - represents severe chocking danger,
Otitis media - middle ear infection with a danger of eardrum perforation.
Lower respiratory infections: Bronchitis, Pneumonia
Septic Arthritis - infection of a synovial joint, along with fever
Invasive severe diseases:
Cellulitis - especially periorbital cellulitis causing swelling of the eyelids in infants/children.
Meningitis
Vasculitis
Sepsis - secondary DIC, gangrene of extremities
H. influenzae
Diagnosis
Treatment
Diagnosis: Samples from infection site, also from CSF
Diagnose by culture characteristics
by Antigen Latex-agglutination for capsule (a-f variants)
by direct immunofluorescent labeling of H. i b antigens in the CSF
rtPCR from blood and CSF samples
Treatment:
Ampicillin and 3rd gen Cephalosporins
or
Ampicillin and Aminoglycosides
but as usual do an antibiogram, 5-40% are penicillin resistant, and a beta-lactamase inhibitor should be used as well.
Active immunisation of children against HiB by vaccine
Activie immunisation of pregnant mothers to prevent infection during birth
Haemophilus ducreyi
Morphology
Culture
Gram negative coccobacillus/bacillus (rod) in long chains.
demanding requires heme (factor X), but not NAD (V) (chocolate agar).
Small whitish colonies
H. ducreyi
Clinical diseases
Treatment
Causes only the sexually transmitted disease chancroid.
Chancroid = Ulcus molle = ulcer soft (as opposed to ulcus durum, hard ulcer of syphilis)
Treatment:
Macrolide or
3rd generation Cephalosporin
What are the 4 major species of Haemophilus bacteria?
What are the diseases they cause?
H. influenziae - many, from mild sinusitis to severe sepsis, meningitis
H. ducreyi - the STD Chancroid
H. aegyptius - Brasilian purpuric fever
H. parainfluenzae - Pharyngitis, Endocarditis, Conjunctivitis
Bordetella pertussis
Morphology
Culture
Gram negative coccobacillus (short), 1uM in pairs
Special medium Bordet-Gengou medium - contains potato extract, glycerol, 20% sheep blood, and antibiotics to inhibit normal flora
- *Distinct mercury like appearance** on this special medium. Small round blue/silver/gray on the 20% blood agar BG-medium.
- *No hemolysis**
Or on Charcoal agar supplemented with defibrinated horse blood. Charcoal, along with starch, neutralizes fatty acids and peroxides, which are toxic to Bordetella.
On Charcoal agar, the pertussis colonies are solid white.
Bordatella pertussis
Clinical diseases
Treatment
“Pertussis” = violent cough
Bordatella pertussis causes whooping cough.
Bordetella pertussis
Virulence factors
Endotoxins
Capsule
Fimbriae
Filamentous hemagglutinin - mediates attachment of the bacteria to the respiratory epithelium.
Outer membrane proteins (OMP)
LPS
Pertactin - A major virulence factor: Adhesion to tracheal respiratory endothelial cells.
Exotoxins:
Pertussis Toxin - Has a pore forming region and another regionwhich activates Gs proteins, which then in turn activate cellular adenylate cyclase, to generate cAMP. Generates cilliary stasis, allowing for enhances cilia binding by filamentous hemagglutinin.
Adenylate-cylcase toxin - a toxin composed of a pore forming domain and its own adenylate cyclase domain. enters cells that B. p is bound to, and causes drastic increases in cAMP. Impairs chemotaxis, as well as inhibiting peroxide and superoxide synthesis, inhibiting immune system.
Tracheal cytotoxin - damages tracheal epithelial cells, damages their cilia, impeding their ability to move bacterial outward from resp. tract.
Dermatonecrotic toxin - activates cellular Rho-GTPase.
Bordetella pertussis
Habitat
Transmission
Humans are only reservoir.
Very contagious and spread by respiratory route during the first two stages of the disease: Catarrhal stage and Paroxysmal stage
Bordatella pertussis
Clinical disease
Disease: Whooping cough, incubation followed by 3 stages:
Incubation: 7-10 days
Catarrhal stage: 1-2 weeks of throat/nasal type infection and possibly conjunctivitis. Fever, malaise and loss of appetite.
Paroxysmal stage: 2-4 weeks. Fever subsides, nonproductive whooping cough develops. 15-25 attacks a day of a several minutes of coughing and wheezing breath. Hypoxia and cyanosis occurs. Neck veins and eyelids bulge, capillaries in the sclera may rupture. Vomitting often occurs after the attack.
Convalescent stage: 3-4 weeks or longer: Coughing attacks decrease. no longer contagious. Secondary complications often occur during this stage such as pneumonia or encephalopathy.
Bordetella pertussis
Diagnosis
Diagnosis:
Cough directly onto the Bordet-Gengou or Charcoal supplemented blood agar.
Or swabbed with a calcium alginate swab, bc the pertussis will not grow on cotton.
Slide agglutination with antibodies against B. pretussis
Direct IF immunolabeling on direct plate smears
ELISA for circulating anti pertussis antibodies
Widal’s type tube agglutination for circulating anti-pertussis antibodies using laboratory pertussis strains.
rtPCR
Bordatella pertussis
Treatment
Prevention
Treatment:
During the prodromal or cattharal stage, Erythromycin (macrolide) or Ampicillin can shorten disease or lessen symptoms.
Resistant to penicillin G.
Treatment during the paroxysmal stage (severe coughing stage) does not alleviate any symptoms, but may decrease the infectivity and bacterial shedding of the patient.
Primarily supportive
Prevention:
Active immunization with neutralized B pertussis as part of the DPT vaccine (Diptheria Pertussis Tetanus)
Acellular vaccine: DaPT vaccine (Diptheria toxoid - “a” for acellular, pertussis, and tetanus.
Differential diagnosis of
- Bordetella pertussis*
- B. parapertussis*
- and*
- B. bronchiseptica*
B pertussis: Requires special agar, Bordet-Gengeu. Others will grow on normal or special agar. Oxidase positive, and Urease negative
B parapertussis: Oxidase negative, Urease positive, and will grow on normal agar.
B bronchiseptica: Is motile and has cillia, the others are not. It is also positive for all the other tests.
Brucellae genus
Morphology
Culture
Gram negative coccobaccili, short coccobacilli
Fastidious requires more than 24 hours and nutrient rich agar containing Serum and Glycine supplement.
Pinpoint smooth shiny colonies. Non-hemolytic at 48 hours
Facultative anaerobic and Facultative intracellular. Is cultured most effectively anaerobically.
*Though they are slow growing, Brucella are hearty, and are easy to grow and maintain in animal stocks. They are also easily disseminated through water droplets and highly infective. Because of all this they are categorized and tracked well as a potential bioterrorism agent.
What are the Brucella species ?
What is their habitat?
How are they transmitted?
They are all zoonotically transmitted
by ingestion of infected animal tissue or milk, or direct skin through skin lesions or eye conjunctiva.
After injestion or skin contact, brucella penetrates through skin lesions or GI mucosa and enters the lymphatics. Where the bacteria proliferate by intracellular growth within bacrophages. This is followed by blood infection and widespread organ infiltration.
Reserviors are animals. Patients are usually animal related-workers.
- B. abortus* - causes abortions in cows
- B. melitensis* - infects goats
- B suis* - pigs
- B canis* - dogs
Every Brucella species causes the same type of disease, Brucellosis in humans
Brucella
Clinical disease
Brucellosis
Fever and chills aka “undulant fever”, RES
loss of appetite, backache, headache, sometimes lymphadenomas.
Orchitis - testicular inflammation, swelling
Carditis
Arthritis and joint swelling often of knees, feet
Symptoms are long lasting from months to years
But fortunately disease is rarely fatal
Brucella
Diagnosis
Treatment
Prevention
By clinical specimen sampling of:
Sputum, urine, blood-culture, CSF, bone marrow, and lymph node punctate:
Direct smear of intracellular gram negative coccobacilli
Culturing is slow, so serology methods should be used.
Serology for Brucella IgM, Tube agglutination
IgM chromatography
ELISA
Treatment:
Doxycyclin, Rifampicin, Streptomycin, Tetracycline
Prevention:
No specific prevention exists. Controlling animal health.
Fancisella tularensis
Habitat
Transmission
Francis the rabit in the Tulip field.
It is harbored by over 100 species of animals and insects, and is zoonotically transmitted by handling carrier animals or being bitten by an insect vector, fly, tick.
It is extremely virulent will start an infectious lesion wherever it makes contact.
If it is on the skin, –> Ulceroglandular tularemia
If it is inhaled (inhaling aerosolized particles while skinning the animal, inhaling a fly) –> Pneumonic tularemia
If it hits the eye –> oculoglandular tularemia
Ingested –> typhodal tularemia
But, there is no human to human transmission.
Francisella Tularensis
Clinical disease
Diagnosis
Tularemia is clinically very similar to the bubonic plague. with the one exception that skin ulcers usually do not develop in the plague.
Skin ulceration with well defined boundaries.
Lymphadenoma, granuloma
Since the bacteria is so infectious it is not cultured.
It is confirmed by measuring the titers of circulating antibodies against F. tularensis.
and rtPCR of clinical samples.
Francisella tularensis
Treatment
