General Bacteria Flashcards
Natural transformation seen in
Streptococcus
Bacillus
Hemophilus
Pseudomonas
Types of plasmids based on function
Fertility Resistance Col (bacteriocins) Virulence Metabolic
Bacteria sitting bidirectional replication
E coli
In prokaryotes start codon AUG codes for
N formyl methionine
Bacteria with diploid chromosome
Vibrio cholerae
Bacteria expressing competence factors
S. Pneumoniae
Bacteria not expressing competence factors
Hemophilus influenzae
Phage coded toxins
Bacterial toxins coded by lysogenic phages
Diphtheria toxin
Cholera toxin
Botulinum toxin
Types of transposons
Insertion sequence transposons
Composite transposons
Composition of blood agar
5-10 percent sheep blood + nutrient agar
Blood agar tests
Partial/Alpha hemolysis - green
Complete/beta hemolysis - clear, light transparent
No hemolysis - unchanged
Chocolate agar
Heated blood agar
More nutritious
RBC contents change medium to brown
Ex: hemophilus influenzae
Loeffler serum slope
For isolation of
Cornybacterium diphtherae
McConkey Agar
Isolation of enteric gram -ve bacteria
Lactose fermenters - pink - E coli
Non lactose fermenters - colour less - shigella
Etiological agents of Infective endocarditis
S. Aureus
Viridans streptococci
HACEK
Early prosthetic valve IE caused by
(<12 mo)
Coagulase negative streptococci
Ex: S. epidermis
Late prosthetic valve IE caused by
(>12 mo)
Viridans streptococci
Culture negative endocarditis caused by
HACEK
Bartonella sp.
Brunella sp.
Name of criteria used for diagnosis of IE
Duke’s criteria
Non blood culture tests for IE
- Serology - for Brucella, Bartonella
- Isolation of pathogens
- Special stains (PAS stain)
- Direct fluorescence Ab technique
- PCR
- Echo
S. Aureus microscopic IE
- Gram +ve cocci in clusters
- Golden yellow hemolytic colonies in blood agar
- Coagulase positive
Viridans streptococci microscopy IE
- Gram +ve long chains
- Mild Alpha hemolytic green colonies in blood agar
- Resistant to optochin
- Bile insoluble
HACEK organisms
Hemophilus influenzae Aggregatibacter sp. Cardiobacterium hominis Eikenella corrodens Kingella kingae
Highly fastidious, gram -ve, commensals in oral cavity
Main c/f of enteric fever (2)
Stepladder fever
Maculopapular rash
In enteric fever, blood sample is collected in
BHI medium
In enteric fever, enrichment broth used in stool examination is
Tetrathionate broth
Selenite F broth
In enteric fever, selective media used for stool sample are
DCA
XLD agar
Wilson Blair bismuth sulfite medium
DCA culture in enteric fever
Non lactose fermenting
Pale colonies with black centre
XLD culture in enteric fever
Red colonies with black centre
Wilson Blair bismuth sulfite medium culture in enteric fever
Jet Black colonies with metallic sheen due to H2S production
Gram strain for S. Typhi
Gram -ve
Non sporing
Non capsulated
Motile
Biochemical identification of typhoid
Catalase +ve
Others -ve
TSI - K/A. Gas present except S. Typhi
H2S present expect s. Paratyphi A
Slide agglutination test for typhoid
S typhi - agg. With O9 antisera
Paratyphi A - O2
Paratyphi B - O4
O agglutination in Widal test appearance
Compact, granular, chalky clumps.
Clear supernatent fluid
H agglutination in Widal test appearance
Large, loose, fluffy
Clear supernatent fluid
Significant titres in Widal test
H>200
O>100
Widal test false +ve
- Transient rise in titre due to other infections
- Inapperent infection
- Recent immunization
False -ve Widal test
Early/late stage
Carriers
Pts. On antibiotics
Prozone phenomenon
Treatment of enteric fever
3rd generation cephalosporins - Ceftriaxone
Azithromycin
Ciprofloxacin
Carriers - amplicilin, amoxicillin
Drug resistance in enteric fever
MDR - Chloramphenicol, Ampicillin
Fluroquinolone resistance - Ciprofloxacin
Ceftriaxone
Viral bloodstream infections
HIV
EBV
Dengue
Chikungunya
Most common fungal bloodstream infections
Candida albicans
Candida tropicalis
Candida auris
Parasitic BSI directly infecting blood cells
Plasmodium
Babesia
Parasitic BSI in bloodstream before migrating to other organs
Leishmania
Toxoplasma
Parasitic BSI that come from lymphatics to bloodstream transiently
Filariasis
Anticoagulant used for conventional culture media for bacteria (blood sample)
Sodium polyanethol sulfonate - also counteracts bactericidal action of blood
Families of rickettsiales order
Rickettsiaceae
Anaplasmataceae
Properties of rickettsiae
Or
Why are rickettsiae considered bacteria and not viruses
Gram -ve cell wall Both DNA and RNA multiply by binary fission Susceptible to antibacterials Held back by bacterial filters
Components of rickettsial cell wall
Peptidoglycans
OMPs
LPS
OMPs of rickettsiae
Species specific
Highly immunogenic
Used for vaccination and diagnosis
Organism, vector and mode of transmission of epidemic typhus
R. Prowasekii
Human body louse
Scratching contaminated skin
Organism, vector and mode of transmission of endemic typhus
R. Typhi
Rat flea
Scratching of contaminated skin
Organism, vector and mode of transmission of Rocky mountain spotted fever
Rickettsia rickettsi
Ticks
Bite of infected tick
Organism, vector and mode of transmission of Indian tick typhus
R. Akari
Tick
Tick bite
Organism, vector and mode of transmission of rickettsial pox
R. Akari
Mites
Mite bite
Organism, vector of scrub typhus
Orientia tsutsugamushi
Infected mite
Organism, vector of Q fever
Coxiella Brunetti
Cattle
Titre for Weil Felix test
1:80 possible infection
>OX19 - Epidemic and endemic
>OX19 + OX2 - Spotted fever
>OXK - Scrub typhus
Proteus strains used in Weil Felix tests
P. Vulgaris OX19, OX2
P. Mirabilia OXK
Lab Dx of rickettsial infections
- Serology: Weil-Felix test (non-specific), IFA, ELISA
- Histological examination of cutaneous biopsy sample from rash
- Isolation - inoculation into HeLa
- PCR
Lab Dx of Scrub Typhus
- Weil-Felix test - OXK Ag
- IFA
- ELISA
- PCR
Acute Q fever symptoms
Hepatitis
Interstitial pneumonia
fever
Pericarditis/Myocarditis
Chronic Q fever symptoms
Endocarditis
Lab Dx for Q fever
Coxiella burnetti
small pleomorphic Gram -ve coccobacillus
Highly fastidious (biosafety level 3 lab)
IFA detects Abs against Ags on LPS
Bartonellosis causative organism
Bartonella henselae
Bartonella henselae causes
- Cat scratch disease - regional lymphadenopathy, papules
2. Bacillary angiomatosis - neovascular lesions on skin and organs
Lab Dx of bartonella
- Warthin-Starry silver nitrate staining of lymph node smear
- Grown in blood agar at 37C
- IFA
- PCR
Rx of bartonella
Cat scratch - Self-limiting, azithromycin
Angiomatosis - Doxycycline
Brucella sp. characteristics
Obligate aerobic
fastidious, small, Gram -ve, coccobacillus
Non motile
C/F of brucellosis
Fever Arthralgia HSM Undulating fever Osteomyelitis
Lab Dx of Brucellosis
Blood culture - Castadena’s biphasic medium (BHI broth)
Serological - SAT - IgM detection
PCR