Gram Negative Bacteria Flashcards
Edward and Ewing classification of Enterobacteriacea
Escherichiae - E Coli, Shigella
Edwarsielleae - Edwardsidlla
Salmonellae - Salmonella
Citrobecterae - Citrobacter
Klebsielleae - Kleibsiella, Enterobacter, Serratia
Proteae - Proteus, Morganella
Yersinieae - Yersinia
Erwinieae - Erwinia
Gram Negative bacteria features
Non sporing
Aerobic
Peritrichous flagella
Glucose fermentation
Nitrate to Nitrite
Catalase +ve
Oxidase -ve
All Gram negative Bacteria arr motile except
Shigella
Salmonella gallinarum
Salmonella pullorum
All Gram negative organisms are Catalase positive except
Shigella dysenteriae - Catalse -ve
Classification of gram negative organisms on the basis of Lactose fermentation
Lactose fermenter
Non lactose fermenter
Late lactose fermenter
Examples of lactose fermenter
E coli
Kleibsiella
Enterobacter Citrobacter
Examples of Non lactose fermenter
Salmonella
Shigella
Proteus
Yersinia
Example of Late lactose fermenter
Shigella sonnei
Test for Lactose fermentation
MacConkey agar
CLED (Cystein lactose electrolyte deficient)
Eosin methylene blue
MacConkey agar consist of
PLANT
Peptone
Lactose - diff. Media
Agar
Neutral red - Indicator media
Taurocholate (Bile salts) - Selective media
MacConkey agar gives which color
Pretty Pink color
MacConkey agar is combination of
Differential media , indicator media and selective media
Indicator media for CLED
Bromothymol blue
CLED better than MacConkey agar because
It’s less inhibitory
Allow both gram Positive and gram negative to grow
CLED gives which color
Yellow
Eosin methylene blue shows which colonies and color
Blue Blackish colonies with green shin around it
Classification of Ecoli on the basis of Antigen
Somatic O (cell wall)
Capsular K antigen
Flagella H antigen
Toxins secreted by Ecoli
Hemolysin
Enterotoxins - Labile toxin, Stable toxin, Verocytotoxin/Shiga like toxin
Enterotoxin/Labile toxin fragments
Fragment A - increases cAMP
Fragment B - Binds to GM1 ganglioside
Labile in air
Stable toxin features
cGMP
Stable on ground
Mechanism of action of Shiga toxin or shiga like toxin
Decreases 60S ribosomes - decrease protein synthesis
Clinical features of Ecoli
UTI
Diarrhea
Meningitis
Sepsis
Pneumonia
Diarrheal strains of E Coli
EPEC(Enteropathogenic)
ETEC(Enterotoxigenic)
EIEC(Enteroinvasive)
EHEC(Enterohemorrhagic)
EAEC(Enteroaggregatory)
DAEC(Diffuselyadherent)
Enteropathogenic Ecoli causes
Pediatric/Infantile diarrhea (bcz it produces bundle forming pili) - Plasmid coded
Enteropathogenic Ecoli shows which lesion
Shows A/E Lesions (Attachment/Effacement lesion)
Enterotoxigenic Ecoli causes
Traveller’s Diarrhea
Large infectivity dose is needed
Colonisation factor antigen (CFA)
Enteroinvasive Ecoli causes
Dysentery (BLOOD + STOOLS)
Antigen responsible for Traveller’s Diarrhea
Colonisation factor antigen (CFA)
Antigen responsible for Dysentery caused by E coli
Virulence marker antigen (VMA)
Enterohemorrhagic Ecoli causes
Hemolytic uremic Syndrome
Hemorrhagic Cystitis
Most common cause of Hemolytic uremic syndrome
Ecoli 0157/H7
Sereny test
Inoculation suspension of bacteria into Guinea’s pig - mucopurulent conjunctivitis and severe keratitis - indicates Positive test
Sereny test is done for
EIEC
Shigella
Listeria monocytogenes
Selective and differential medium used for detection of Enterohemorrhagic Ecoli
SMAC Test (Sorbitol McConkey agar) - 0157/H7 doesn’t shows this reaction
Small infectivity dose is needed for which bacilli
CHHOTA SMALL
Cryptosporidium
E. Histolytica
Enterohemorrhagic Ecoli
Shigella
G. Lamblia
Enteroaggregatory Ecoli causes
Persistent diarrhea (>14 day)
Toxin involved in Enteroaggregatory Ecoli
EAST 1 Toxin
Enteroaggregatory Ecoli on Hep2 cell line shows
Stagged brick appearance
Sample in case of UTI due to Ecoli
Urine - fresh clean catch midstream urine
Suprapubic aspiration(Obstructive uropathy)
Catheter specimen not recommended
Blood Agar finding for Ecoli
Hemolytic
Finding of MacConkey agar for Ecoli
Pink color
CLED Finding for Ecoli
Shows yellow color
Selective media used for Ecoli diagnosis
DCA(Deoxycholate citrate agar)
IMVIC Test
Indole test - Red color
Methyl red test - Red +
Voges Proskauer test - Red +
Citrate utilization test - Blue +
Biochemical test findings/IMVIC of Ecoli
Ferment glucose/lactose
Indole +
Methyl red +
Voges Proskauer -ve
Citrate utilization test -ve
IMVIC Test result in Ecoli and Klebsiella
++– (Ecoli)
–++ (Klebsiella)
Treatment of Ecoli infection
Uncomplicated - Cotrimoxazole or Ciprofloxacin
Depends on sensitivity
Shigella features
Non motile
Non sporing
Non encapsulated
Gram Negative bacilli
Low infective dose needed
No lactose fermentation
All shigella species are Catalase +ve and shows Mannitol fermentation except
Shigella dysenteriae
Shigella includes
Shigella dysenteriae
Shigella flexneri - M/C India
Shigella boydii
Shigella sonnei
Which shigella species shows non lactose fermentation
S. Dysenteriae
S. Flexneri
S. Boydii
Which shigella species shows late lactose fermentation
S. Sonnei - M/C worldwide
Toxins release by Shigella
Exotoxin - Enterotoxin (SheT 1 and 2), Cytotoxin (Shiga toxin)
Endotoxin
Pathogenesis of Shigella infection
Shigella enters with the help of M cells - Rupture Macrophages - then enters again via basolateral endocytosis - cell by cell actin polymerisation
Antigens associated with shigella infection
Virulence marker Antigen (VMA)
Invasive Plasmid antigen (IPA)
Incubation period of shigellosis
1-4 days
Initial clinical manifestations of Shigellosis
Water diarrhea - Dysentery
Complications of Shigellosis
Toxic megacolon
Perforation
Metabolic complications - Hypoglycemia, Hyponatremia
Shigella encephalopathy is termed as
Ekiri Syndrome - Toxic encephalopathy, Delirium, Confusion
HUS can be caused by
Enterohemorrhagic Ecoli
Shigella
Reiter’s Syndrome includes
Reactive arthritis
Urethritis
Conjunctivitis
IMVIC Test in Shigellosis
M SHY - Shigella, Yersinia
Methyl red +
IMVIC : -+–
Transport media used in Shigellosis
SBGS (Sachs buffered Glycerol saline)
Enrichment media or broth used in Shigella and Salmonella infection
Sclenite F broth
Tetrathionate B broth
Selective media used for diagnosis of Shigella and Salmonella
XLD ( Xylase Lysine deoxycholate)
DCA (Deoxycholate agar)
SS (Salmonella Shigella agar)
HE (Hektoen enteric agar)