FERMENTATIVE GRAM-NEGATIVE (-) BACILLI (ENTEROBACTERIACEAE) Flashcards
memorization
General characteristics of Enterobacteriaceae:
- Gram-negative rods; either motile with peritrichous flagella or non-motile (“SKY”)
- Facultative anaerobes that grow well on artificial media
- Catalase positive, oxidase negative, reduce nitrate to nitrite
- Fermenters (produce acid in presence or absence of oxygen); All are glucose fermenters with or without gas production
Antigens of Enterobacteriaceae:
- O antigen
- H antigen
- K antigen
O antigen other name:
Somatic antigen
H antigen other name:
Flagellar antigen
K antigen other name:
Capsular antigen
location of O antigen
Cell wall
location of H antigen:
Flagella
location of K antigen:
Capsule
Enterobacteriaceae antigen used for serological grouping of Salmonella & Shigella
O antigen
Enterobacteriaceae antigen used to serotype Salmonella
H antigen
Enterobacteriaceae antigen role in preventing phagocytosis
K antigen
Predominant aerobe in the GIT; colonic normal flora (nonpathogenic strains) of human and animals
Escherichia coli (Colon bacillus)
Diseases caused by E. coli:
- Diarrhea
- UTI (most common cause)
- Neonatal meningitis
- Gram (-) sepsis
Mnemonic: DUNG
Also known as Shiga toxin-producing (STEC) or verotoxin-producing (VTEC); Diarrhea, hemorrhagic colitis, hemolytic uremic syndrome (HUS)
Enterohemorrhagic (EHEC)
Transmission of EHEC:
Undercooked, raw milk, apple cider
Most common isolate of group & pathogen most often isolated from bloody stools:
E. coli O157:H7
Culture media for E. coli O157:H7
Sorbitol-MacConkey Agar
Note: E. coli O157:H7 does not ferment sorbitol; colonies are colorless
Causes “Traveler’s diarrhea” (aka Montezuma’s revenge Turista), diarrhea in infants
Enterotoxigenic (ETEC)
Transmission of ETEC:
Contaminated food or water
Diarrhea in infants (Pediatric diarrhea); major pathogen in infants in developing countries
Enteropathogenic (EPEC)
Transmission of EPEC:
Formula & food contaminated with fecal material
Diarrhea in developing countries; chronic diarrhea in HIV-infected patients
Enteroaggregative (EAEC)
Diarrhea & UTI; Most common in children in developing countries:
Diffusely adherent (DAEC)
Common ventilator-associated pneumonia and is also associated with alcoholism (pneumococcus is still more common) and aspiration
KLebsiella pneumoniae
“Currant jelly” sputum is described in the infection of __________.
K. pneumonaie
The only indole positive Klebsiella; IMVIC: +-++
Klebsiella oxytoca
two (2) general types of Salmonella:
- Salmonella typhi
- Non-typhoid strains
Bacteria that causes typhoid fever:
Salmonella typhi
Non-typhoid strains:
S. enterica
S. enteritidis
Diseases caused by Salmonella:
- Endotoxin
- Entercolitis
- Septicemic (estraintestinal) disease
- Enteric fever (typhoid)
Salmonella stain that causes less severe typhoid fever:
Salmonella paratyphi
Salmonella strain that causes serious and recurring problems for patients with sickle cell disease
Salmonella osteomylitis
Signs and symptoms of typhoid fever:
- Abdominal pain
- Fever
- “Rose spots” may appear on the trunk of the patient in the second and third weeks
- Pulse-temperature dissociation (high fever with slow pulse)
Diagnosis for typhoid fever:
Culture (stool, blood) (Gold standard)
Most communicable of bacterial diarrhea (<200 bacilli needed to infect a person)
Shigella
Shigella strain that causes the most severe disease:
Shigella dysenteriae
Only Shigella strain that is ONPG (late lactose fermenter) positive:
Shigella sonnie
Only Shigella strain that is Catalase test, ONPG, Mannitol test negative
Shigella dysenteriae
Shigella strains that is positive for Catalase test and Mannitol test and negative for ONPG:
Shigella flexneri
Shigella boydii
Bacteria that produces swarming on agar
Proteus
Most common proteus strain that is indole (-)
Proteus mirabilis
Differentiate P. mirabilis and P. vulgaris:
P. mirabilis
- Indole (-)
- TSI = K/A
P. vulgaris
- Indole (+)
- TSI = A/A
Diseases caused by Proteus:
- UTI
- Wound infections
- Septicemia
Kidney stone associated with Proteus:
- Struvite kidney stones (then to urinary obstruction); (Proetus produces a powerful urease that hydrolyzes urea to ammonia and CO2, leading to struvite kidney stone [alkaline])
Slow lactose fermenters, not dominant pathogen for any clinical condition; often resistant to many antibiotics
Citrobacter and Serratia marcescens
Classified as BSL I; produce distinctive red colonies (red pigment); catalase (+), DNase (+)
Serratia marcescens
Bacteria that mimics Crohn’s disease or appendicitis; can cause inflammation around appendix or in mesenteric lymph nodes (mesenteric adenitis)
Yersinia enterocolitica
Cause of bubonic plague (‘“black death”);
Yersinia pestis
Humans get disease from what rat flea?
Xenopsylla cheopsis
Signs and symptoms of bubonic plague:
Fever, chills, headache; intense pain/swelling of a lymph node area (bubo)
Chief reservoir are reptiles & freshwater fish; Infections often involve aquatic environments; Opportunistic; H2S (+); Indole (+) differentiates from Salmonella:
Edwardsiella tarda
Only oxidase (+) Enterobacteriaceae; pleomorphic gram-negative rods in singles, pairs, short chains, or long filaments’ Biochemical & antigenic similarities to Shigella; Motile
Plesiomonas shigelloides (now included in Enterobacteriaceae)
