Enterobacterales Part 1

*Question: Which biochemical test pattern distinguishes E. coli from other Enterobacterales?
A) IMVIC: --++
B) IMVIC: ++--
C) IMVIC: -++-
D) IMVIC: +--+

*Answer: B) IMVIC: ++--

*Question: Which three genera of Enterobacterales are characteristically non-motile (mnemonic "SKY")?
A) Salmonella, Klebsiella, Yersinia
B) Shigella, Klebsiella, Yersinia
C) Serratia, Klebsiella, Yersinia
D) Shigella, Kluyvera, Yersinia

*Answer: B) Shigella, Klebsiella, Yersinia

*Question: What is the characteristic appearance of E. coli on Eosin Methylene Blue (EMB) agar?
A) Black colonies with metallic sheen
B) Green metallic sheen
C) Pink mucoid colonies
D) Colorless colonies with black centers

*Answer: B) Green metallic sheen

*Question: Which genera are VP-positive and belong to the mnemonic "KESH"?
A) Klebsiella, E. coli, Shigella, Hafnia
B) Klebsiella, Enterobacter, Salmonella, Hafnia
C) Klebsiella, Enterobacter, Serratia, Hafnia
D) Klebsiella, Edwardsiella, Serratia, Hafnia

*Answer: C) Klebsiella, Enterobacter, Serratia, Hafnia

*Question: What is the TSI reaction pattern for organisms that ferment only glucose?
A) A/A (yellow/yellow)
B) K/A (red/yellow)
C) K/K (red/red)
D) A/K (yellow/red)

*Answer: B) K/A (red/yellow)

*Question: Which is the only oxidase-positive member of the Order Enterobacterales?
A) E. coli
B) Plesiomonas shigelloides
C) Klebsiella pneumoniae
D) Proteus mirabilis

*Answer: B) Plesiomonas shigelloides

*Question: What causes the green metallic sheen of E. coli on EMB agar?
A) Capsule production
B) Strong acid production during lactose fermentation reacting with dyes
C) H2S production
D) Urease activity

*Answer: B) Strong acid production during lactose fermentation reacting with dyes

*Question: Which three genera are phenylalanine deaminase-positive (mnemonic "PPM")?
A) Pantoea, Providencia, Morganella
B) Proteus, Plesiomonas, Morganella
C) Proteus, Providencia, Morganella
D) Proteus, Providencia, Enterobacter

*Answer: C) Proteus, Providencia, Morganella

*Question: What is the most common cause of urinary tract infections (UTIs)?
A) Klebsiella pneumoniae
B) Proteus mirabilis
C) Escherichia coli
D) Enterobacter cloacae

*Answer: C) Escherichia coli

*Question: Which E. coli pathotype produces Shiga toxins and causes hemolytic uremic syndrome (HUS)?
A) ETEC
B) EPEC
C) EHEC
D) EAEC

*Answer: C) EHEC

*Question: What is the most common E. coli pathotype causing traveler's diarrhea?
A) ETEC (Enterotoxigenic)
B) EPEC (Enteropathogenic)
C) EHEC (Enterohemorrhagic)
D) EIEC (Enteroinvasive)

*Answer: A) ETEC (Enterotoxigenic)

*Question: Which E. coli pathotype causes infantile/pediatric diarrhea with attaching and effacing lesions?
A) ETEC
B) EPEC
C) EIEC
D) DAEC

*Answer: B) EPEC

*Question: What are the three components of the HUS triad?
A) Fever, anemia, thrombocytosis
B) Microangiopathic hemolytic anemia, thrombocytopenia, renal insufficiency
C) Diarrhea, vomiting, dehydration
D) Hemolysis, uremia, septicemia

*Answer: B) Microangiopathic hemolytic anemia, thrombocytopenia, renal insufficiency

*Question: Which selective agar is used to distinguish E. coli O157:H7 from other E. coli strains?
A) MacConkey agar
B) SMAC (Sorbitol-MacConkey) agar
C) XLD agar
D) EMB agar

*Answer: B) SMAC (Sorbitol-MacConkey) agar

*Question: What is the characteristic appearance of E. coli O157:H7 on SMAC agar?
A) Pink colonies
B) Colorless colonies
C) Green metallic colonies
D) Black colonies

*Answer: B) Colorless colonies

*Question: Which K antigen is associated with E. coli causing neonatal meningitis?
A) K2 antigen
B) K5 antigen
C) K1 antigen
D) Vi antigen

*Answer: C) K1 antigen

*Question: What is the characteristic colony morphology of Klebsiella on MacConkey agar?
A) Swarming growth
B) Large, mucoid, pink colonies
C) Green metallic sheen
D) Colorless with black centers

*Answer: B) Large, mucoid, pink colonies

*Question: What causes the mucoid appearance of Klebsiella colonies?
A) Excessive flagella
B) Large capsule production
C) Biofilm formation
D) Lipopolysaccharide overproduction

*Answer: B) Large capsule production

*Question: Which Klebsiella subspecies causes atrophic rhinitis?
A) K. pneumoniae subsp. pneumoniae
B) K. pneumoniae subsp. ozaenae
C) K. pneumoniae subsp. rhinoscleromatis
D) K. oxytoca

*Answer: B) K. pneumoniae subsp. ozaenae

*Question: What is the characteristic histological finding in rhinoscleroma caused by K. rhinoscleromatis?
A) Langhans giant cells
B) Mikulicz cells
C) Reed-Sternberg cells
D) Aschoff bodies

*Answer: B) Mikulicz cells

*Question: Which Klebsiella species is motile and was formerly classified as Enterobacter aerogenes?
A) K. pneumoniae
B) K. oxytoca
C) K. aerogenes
D) K. variicola

*Answer: C) K. aerogenes

*Question: What does CRKP stand for in antimicrobial resistance terminology?
A) Ciprofloxacin-Resistant Klebsiella pneumoniae
B) Carbapenem-Resistant Klebsiella pneumoniae
C) Colistin-Resistant Klebsiella pneumoniae
D) Cephalosporin-Resistant Klebsiella pneumoniae

*Answer: B) Carbapenem-Resistant Klebsiella pneumoniae

*Question: Which organism was formerly known as Enterobacter sakazakii and produces yellow pigment?
A) Pantoea agglomerans
B) Cronobacter sakazakii
C) Serratia marcescens
D) Raoultella planticola

*Answer: B) Cronobacter sakazakii

*Question: What type of infections does Cronobacter sakazakii cause in neonates?
A) Diarrhea only
B) Sepsis, meningitis, and necrotizing enterocolitis
C) Urinary tract infections
D) Skin infections

*Answer: B) Sepsis, meningitis, and necrotizing enterocolitis

*Question: What is the source of Cronobacter sakazakii infections in infants?
A) Breast milk
B) Contaminated water
C) Powdered infant formula
D) Baby bottles

*Answer: C) Powdered infant formula

*Question: Which property allows Cronobacter to survive in powdered infant formula?
A) Thermophilic nature
B) Xerotolerance (survival in dry environments)
C) Acid resistance
D) Salt tolerance

*Answer: B) Xerotolerance (survival in dry environments)

*Question: Which Citrobacter species is linked to brain abscesses in neonates?
A) C. freundii
B) C. koseri
C) C. amalonaticus
D) C. farmeri

*Answer: B) C. koseri

*Question: What is a key biochemical feature that helps distinguish Citrobacter from Salmonella?
A) Lactose fermentation (variable/late)
B) Oxidase positive
C) Urease negative
D) VP positive

*Answer: A) Lactose fermentation (variable/late)

*Question: Which test distinguishes K. ascorbata from K. cryocrescens?
A) Indole production
B) Glucose fermentation at 5°C
C) Urease activity
D) H2S production

*Answer: B) Glucose fermentation at 5°C

*Question: What was Plesiomonas shigelloides formerly classified as?
A) Member of Enterobacteriaceae
B) Member of Vibrionaceae
C) Member of Pseudomonadaceae
D) Member of Aeromonadaceae

*Answer: B) Member of Vibrionaceae

*Question: How can Plesiomonas be differentiated from Vibrio species?
A) Plesiomonas is oxidase negative; Vibrio is positive
B) Plesiomonas is sensitive to high salt; Vibrio can survive in high salt
C) Plesiomonas produces H2S; Vibrio does not
D) Plesiomonas is non-motile; Vibrio is motile

*Answer: B) Plesiomonas is sensitive to high salt; Vibrio can survive in high salt

*Question: Which organism was formerly Enterobacter agglomerans and caused septicemia from contaminated IV fluids?
A) Cronobacter sakazakii
B) Pantoea agglomerans
C) Klebsiella aerogenes
D) Serratia marcescens

*Answer: B) Pantoea agglomerans

*Question: What is the decarboxylase pattern (LOA) for Pantoea agglomerans?
A) All positive
B) All negative (triple negative)
C) Lysine positive only
D) Ornithine positive only

*Answer: B) All negative (triple negative)

*Question: What is the characteristic growth pattern of Proteus species on agar?
A) Mucoid colonies
B) Swarming with concentric rings
C) Green metallic sheen
D) Pigmented colonies

*Answer: B) Swarming with concentric rings

*Question: Which substance is added to Modified Thayer-Martin medium to prevent Proteus swarming?
A) Vancomycin
B) Colistin
C) Trimethoprim lactate
D) Polymyxin B

*Answer: C) Trimethoprim lactate

*Question: How does Proteus mirabilis contribute to kidney stone formation?
A) Produces oxalate
B) Produces urease, increasing urine pH and forming struvite stones
C) Produces acid that precipitates calcium
D) Directly forms biofilms on kidney tissue

*Answer: B) Produces urease, increasing urine pH and forming struvite stones

*Question: What distinguishes Proteus mirabilis from Proteus vulgaris?
A) P. mirabilis is indole negative; P. vulgaris is indole positive
B) P. mirabilis is urease negative; P. vulgaris is urease positive
C) P. mirabilis is non-motile; P. vulgaris is motile
D) P. mirabilis produces H2S; P. vulgaris does not

*Answer: A) P. mirabilis is indole negative; P. vulgaris is indole positive

*Question: What biochemical tests are positive for all PPM genera (Proteus, Providencia, Morganella)?
A) Indole and urease
B) Phenylalanine deaminase and lysine deaminase
C) Citrate and VP
D) H2S and lactose fermentation

*Answer: B) Phenylalanine deaminase and lysine deaminase

*Question: What is the LIA (Lysine Iron Agar) reaction for organisms positive for lysine deaminase?
A) Yellow slant, yellow butt
B) Red slant, yellow butt
C) Purple slant, purple butt
D) Black slant, yellow butt

*Answer: B) Red slant, yellow butt

*Question: Which Morganella test differentiates M. morganii subsp. morganii from subsp. sibonii?
A) Indole production
B) Trehalose fermentation
C) Urease activity
D) Ornithine decarboxylase

*Answer: B) Trehalose fermentation

*Question: Which Providencia species is associated with traveler's diarrhea?
A) P. stuartii
B) P. rettgeri and P. alcalifaciens
C) P. rustigianii
D) All Providencia species

*Answer: B) P. rettgeri and P. alcalifaciens

*Question: What distinguishes Providencia rettgeri from P. alcalifaciens?
A) P. rettgeri is urease, mannitol, and inositol positive
B) P. rettgeri is indole negative
C) P. rettgeri does not cause diarrhea
D) P. rettgeri is non-motile

*Answer: A) P. rettgeri is urease, mannitol, and inositol positive

*Question: What is the characteristic delayed biochemical reaction of Hafnia species?
A) Delayed urease production
B) Delayed citrate reaction (positive next day)
C) Delayed indole production
D) Delayed H2S production

*Answer: B) Delayed citrate reaction (positive next day)

*Question: Which Hafnia species produces a verocytotoxin linked to gastroenteritis?
A) H. paraalvei
B) H. psychrotolerans
C) H. alvei
D) All Hafnia species

*Answer: C) H. alvei

*Question: Which Edwardsiella species is the only recognized human pathogen?
A) E. anguillarum
B) E. hoshinae
C) E. tarda
D) E. ictalurid

*Answer: C) E. tarda

*Question: What underlying condition increases risk for Edwardsiella tarda infection?
A) Diabetes mellitus
B) Hepatobiliary disease
C) Chronic kidney disease
D) Immunosuppression from HIV

*Answer: B) Hepatobiliary disease

*Question: What is the characteristic pigment produced by Serratia marcescens?
A) Pyocyanin (blue-green)
B) Prodigiosin (red)
C) Violacein (purple)
D) Melanin (brown)

*Answer: B) Prodigiosin (red)

*Question: At what temperature is prodigiosin pigment best produced by Serratia?
A) 37°C (body temperature)
B) 42°C
C) Room temperature (25°C)
D) 4°C

*Answer: C) Room temperature (25°C)

*Question: Why are clinical isolates of Serratia often nonpigmented?
A) They lose pigment genes in human hosts
B) Incubators are at 37°C, not ideal for pigment production
C) Clinical media inhibit pigment production
D) Antibiotics suppress pigmentation

*Answer: B) Incubators are at 37°C, not ideal for pigment production

*Question: Which Serratia species has an odor like rotten potatoes?
A) S. marcescens
B) S. rubidaea
C) S. odorifera
D) S. liquefaciens

*Answer: C) S. odorifera

*Question: Which Salmonella serotype causes typhoid fever?
A) S. enterica serotype Paratyphi A
B) S. enterica serotype Typhi
C) S. enterica serotype Cholerasuis
D) S. enterica serotype Enteritidis

*Answer: B) S. enterica serotype Typhi

*Question: What is the Vi antigen in Salmonella?
A) Flagellar antigen
B) Somatic antigen
C) Capsular polysaccharide antigen
D) Outer membrane protein

*Answer: C) Capsular polysaccharide antigen

*Question: Which Salmonella serotypes have the Vi antigen?
A) S. Typhi and S. Paratyphi A
B) S. Typhi and S. Paratyphi C
C) All Salmonella serotypes
D) S. Enteritidis and S. Typhimurium

*Answer: B) S. Typhi and S. Paratyphi C

*Question: What is the best specimen for blood culture in typhoid fever?
A) During the third week of illness
B) During the first week of illness
C) During the fifth week of illness
D) Any time during illness

*Answer: B) During the first week of illness

*Question: When should stool or urine culture be collected for Salmonella in typhoid fever?
A) First week
B) Second week
C) Third week or later
D) Before symptoms appear

*Answer: C) Third week or later

*Question: What is the appearance of Salmonella on XLD agar?
A) Pink colonies
B) Blue-green colonies with black centers
C) Red colonies with black centers
D) Colorless colonies

*Answer: C) Red colonies with black centers

*Question: What is the appearance of Salmonella on SS (Salmonella-Shigella) agar?
A) Pink colonies
B) Straw-colored or colorless colonies with black centers
C) Green metallic sheen
D) Red colonies

*Answer: B) Straw-colored or colorless colonies with black centers

*Question: What is the Widal test used for?
A) Detecting Salmonella antigens in stool
B) Detecting antibodies to Salmonella O and H antigens
C) Detecting Shiga toxin
D) Detecting urease activity

*Answer: B) Detecting antibodies to Salmonella O and H antigens

*Question: What does the TUBEX TF test detect?
A) Anti-O9 IgM antibodies for typhoid fever
B) Salmonella DNA
C) Shiga toxin
D) Capsular antigen

*Answer: A) Anti-O9 IgM antibodies for typhoid fever

*Question: What virulence mechanism allows Salmonella to survive in macrophages?
A) Capsule formation
B) Resistance to killing inside phagolysosomes
C) Flagellar motility
D) Biofilm formation

*Answer: B) Resistance to killing inside phagolysosomes

*Question: Who was "Typhoid Mary"?
A) The first person to discover Salmonella
B) Mary Mallon, a healthy carrier of S. Typhi
C) A patient who died from typhoid fever
D) A nurse who treated typhoid patients

*Answer: B) Mary Mallon, a healthy carrier of S. Typhi

*Question: Where does Salmonella Typhi persist in chronic carriers?
A) Liver
B) Spleen
C) Gallbladder
D) Kidneys

*Answer: C) Gallbladder

*Question: What is the infectious dose of Shigella required to cause disease?
A) 1,000-10,000 organisms
B) 10-100 organisms
C) 100,000 organisms
D) 1,000,000 organisms

*Answer: B) 10-100 organisms

*Question: Which Shigella serogroup is associated with the most severe dysentery?
A) Group A (S. dysenteriae)
B) Group B (S. flexneri)
C) Group C (S. boydii)
D) Group D (S. sonnei)

*Answer: A) Group A (S. dysenteriae)

*Question: Which Shigella species produces Shiga toxin?
A) S. sonnei
B) S. flexneri
C) S. dysenteriae type 1
D) S. boydii

*Answer: C) S. dysenteriae type 1

*Question: Which Shigella species is a slow lactose fermenter?
A) S. dysenteriae
B) S. flexneri
C) S. boydii
D) S. sonnei

*Answer: D) S. sonnei

*Question: Which Shigella species is the only one negative for mannitol fermentation?
A) S. dysenteriae
B) S. flexneri
C) S. boydii
D) S. sonnei

*Answer: A) S. dysenteriae

*Question: What is the characteristic stool appearance in bacillary dysentery caused by Shigella?
A) Watery diarrhea
B) Bloody diarrhea with mucus and pus
C) Rice water stools
D) Fatty, floating stools

*Answer: B) Bloody diarrhea with mucus and pus

*Question: What is the motility pattern of Shigella at all temperatures?
A) Motile at 37°C only
B) Motile at 25°C only
C) Motile at all temperatures
D) Non-motile at all temperatures

*Answer: D) Non-motile at all temperatures

*Question: How does Shigella invade intestinal cells?
A) Via flagella
B) Via Type III secretion system
C) Via capsule
D) Via pili only

*Answer: B) Via Type III secretion system

*Question: What is the mechanism of Shiga toxin?
A) Inhibits DNA synthesis
B) Inhibits protein synthesis leading to cell death
C) Inhibits cell wall synthesis
D) Disrupts cell membranes

*Answer: B) Inhibits protein synthesis leading to cell death

*Question: Which three Yersinia species are clinically significant?
A) Y. pestis, Y. enterocolitica, Y. ruckeri
B) Y. pestis, Y. pseudotuberculosis, Y. enterocolitica
C) Y. pestis, Y. frederiksenii, Y. intermedia
D) Y. enterocolitica, Y. kristensenii, Y. aldovae

*Answer: B) Y. pestis, Y. pseudotuberculosis, Y. enterocolitica

*Question: Which Yersinia species causes plague?
A) Y. enterocolitica
B) Y. pseudotuberculosis
C) Y. pestis
D) Y. ruckeri

*Answer: C) Y. pestis

*Question: What are the three forms of plague caused by Y. pestis?
A) Intestinal, respiratory, systemic
B) Bubonic, septicemic, pneumonic
C) Primary, secondary, tertiary
D) Cutaneous, mucosal, disseminated

*Answer: B) Bubonic, septicemic, pneumonic

*Question: How is Y. pestis transmitted?
A) Only by fleas
B) By fleas, direct contact, or aerosol
C) Only by aerosol
D) Through contaminated water

*Answer: B) By fleas, direct contact, or aerosol

*Question: What is the characteristic microscopic appearance of Y. pestis?
A) Gram-positive cocci
B) Gram-negative coccobacilli with bipolar staining ("safety-pin")
C) Gram-negative rods with flagella
D) Gram-positive rods

*Answer: B) Gram-negative coccobacilli with bipolar staining ("safety-pin")

*Question: At what temperature is Y. enterocolitica motile?
A) 37°C only
B) Non-motile at all temperatures
C) 25°C (room temperature)
D) 4°C only

*Answer: C) 25°C (room temperature)

*Question: What is the motility pattern of Y. pestis?
A) Motile at 37°C
B) Motile at 25°C
C) Non-motile at all temperatures
D) Motile at all temperatures

*Answer: C) Non-motile at all temperatures

*Question: Which Yersinia species mimics appendicitis?
A) Y. pestis
B) Y. pseudotuberculosis
C) Y. enterocolitica
D) Both B and C

*Answer: D) Both B and C

*Question: What is a common food source for Y. enterocolitica infection?
A) Beef
B) Chicken
C) Pork (chitterlings/intestines)
D) Fish

*Answer: C) Pork (chitterlings/intestines)

*Question: Which selective agar shows Y. enterocolitica as "bull's eye" colonies?
A) CIN agar
B) CIN II agar
C) MacConkey agar
D) XLD agar

*Answer: B) CIN II agar

*Question: What does CIN agar stand for?
A) Citrate-Indole-Novobiocin
B) Cefsulodin-Irgasan-Novobiocin
C) Chromogenic-Isolation-Nutrient
D) Cefoxitin-Irgasan-Nitrate

*Answer: B) Cefsulodin-Irgasan-Novobiocin

*Question: Which Yersinia species is urease negative?
A) Y. enterocolitica
B) Y. pseudotuberculosis
C) Y. pestis
D) All are urease positive

*Answer: C) Y. pestis

*Question: What is cold enrichment used for in Yersinia culture?
A) To kill other bacteria
B) To enhance recovery of Yersinia at 4°C
C) To promote pigment production
D) To induce motility

*Answer: B) To enhance recovery of Yersinia at 4°C

*Question: What allows Yersinia to grow in refrigerated food?
A) High salt tolerance
B) Ability to grow at low temperatures (1°C-5°C)
C) Acid resistance
D) Capsule formation

*Answer: B) Ability to grow at low temperatures (1°C-5°C)

*Question: What are Yops in Yersinia virulence?
A) Capsular polysaccharides
B) Yersinia outer proteins that inhibit phagocytosis
C) Toxins that lyse red blood cells
D) Flagellar proteins

*Answer: B) Yersinia outer proteins that inhibit phagocytosis

*Question: What is the F1 capsule in Y. pestis?
A) A flagellar protein
B) An encapsulation antigen that aids virulence
C) A toxin
D) An adhesion protein

*Answer: B) An encapsulation antigen that aids virulence

*Question: What are the four carbapenemase antibiotics in the mnemonic IMDE?
A) Imipenem, meropenem, doripenem, ertapenem
B) Isoniazid, metronidazole, doxycycline, erythromycin
C) Itraconazole, minocycline, daptomycin, ethambutol
D) Ibuprofen, morphine, diazepam, epinephrine

*Answer: A) Imipenem, meropenem, doripenem, ertapenem

*Question: What does CRE stand for?
A) Colistin-Resistant Enterobacteriaceae
B) Carbapenem-Resistant Enterobacteriaceae
C) Cephalosporin-Resistant Enterobacteriaceae
D) Ciprofloxacin-Resistant Enterobacteriaceae

*Answer: B) Carbapenem-Resistant Enterobacteriaceae

*Question: What does ESBL stand for?
A) Extended-Spectrum Beta-Lactamases
B) Extra-Strong Bacterial Lipases
C) Enhanced Structural Biofilm Layers
D) Enzymatic Substrate Binding Ligands

*Answer: A) Extended-Spectrum Beta-Lactamases