TEST 2 Bugs 2 Part 1/2

Question 1

Most gram negative rods are in what family and what is their respiration type?

Answer 1

Enterobacteriaceae
Facultative anaerobes

Question 2

Gram Negative rods are normally found where and commonly cause what?

Answer 2

• Normal GI flora
• Diarrhea and UTI

Question 3

Gram negative rods are resistant to what two common antibiotics due to their Outer membrane.

Answer 3

Vancomycin and Penicillin

Question 4

Most gram negative enteric bacteria are resistant to ___________ compared to gram-positives.

Answer 4

Bile Salts

Question 5

Enterobacteriaceae ferment what?

Oxidase?

Catalase?

Reduction?

Answer 5

• Glucose
• Oxidase: -ve
• Catalase: +ve
• Reduce: nitrates to nitrites (anaerobic respiration)

Question 6

Which gram negative rods are lactose fermenters?

Answer 6

• Fecal Coliforms = CEEK
  
  • Citrobacter
    
    • Slow lactose fermenters
  • Enterobacter
  • Escherichia
  • Klebsiella

Question 7

Which gram negative rods are lactose nonfermenters?

Answer 7

• ShYPS
  
  • Non-motile, no H2S
    
    • Shigella
    • Yersina
  • Motile, and produce H2S
    
    • Proteus
    • Salmonella

Question 8

Virulence factors for gram negative rods

Answer 8

• Surface antigens:
  
  • O (PS part of LPS)
  • H (flagellar)
  • K (capsular, Salmonella’s is Vi)
  • Fimbriae, endotoxin (lipid A)

Question 9

What does E. Coli look like on different plates?

Answer 9

• Eosin-Methylene Blue: Green Metallic sheen
• MacConkey agar: Red colonies
• Triple Sugar iron (TSI): Lactose + Sucrose + Limited glucose fermentation + gas.

Question 10

E. coli disease-causing strains:

Answer 10

• Diarrhea-causing strains
  
  • EnteroTOXIGENIC (ETEC)
  • EnteroPATHOGENIC (EPEC)
  • EnteroHEMORRHAGIC (EHEC)
  • EnteroINVASIVE (EIEC)
• UTI-Causing strain
  
  • Uropathogenic (UPEC) - P Pili
• Neonate meningitis
  
  • K1 capsule

Question 11

Describe ETEC:

Answer 11

• Traveler’s Diarrhea & infantile diarrhea in developing world
  
  • Watery diarrhea
• Labile Toxin (LT) - ADP-ribosylates and stimulates Gsa → ^d cAMP.
• Stable Toxin (ST) stimulates cGMP.
• Both toxins cause loss of fluids and ions, causing water, non-inflammatory diarrhea.

Question 12

Describe EPEC:

Answer 12

• Infantile (Pediatric) diarrhea.
• No toxin or inflammation
• Pathogenicity Is. (PAI) encodes a type III secretion system and intimin adhesin.
  
  • Results in blunt microvilli and prevent absorption → watery diarrhea.

Question 13

Describe EHEC:

Answer 13

• (O157:H7)
• No ferment sorbitol.
• Do not invade host cell.
• In colon, produces shiga-like toxin that nicks 60S ribosomes.
  
  • Bloody diarrhea
  • can turn into Acute renal failure.

Question 14

Describe EIEC:

Answer 14

• Dysentery: fever, diarrhea, vomiting, abdominal cramping, tenesmus.
• Often blood and pus in stools.
• Invades intestinal epithelium (invasion proteins)
• Similar to shigellosis.

Question 15

Escherichia coli

UTIs details

Answer 15

• UPEC - Cystitis - E. coli Type 1 fimbriae adhere to perineum.
  
  • Pyelonephritis - P fimbriae (Pili) adhere to uroepithelium
    
    • High risk of septicemia and shock.

Question 16

Escherichia coli

Gram negative sepsis

Answer 16

• Most likely from UTIs:
  
  • Elderly patient, UTI (catheter, BPH), gram negative sepsis, + blood culture.
    
    • Life threatening, due to endotoxin (lipid A).

Question 17

Shigella details

Answer 17

• Human pathogen (usually infants and children) Not normal flora.
• Fecal oral spread; low infectious dose
• Catalase +; Ferment Glucose
• Invade intestinal M cells and induce apoptosis.
• Shiga toxin - cleaves 60S rRNA = inhibits protein synthesis and damages intestinal epithelium and glomerular epithelium.
• Shigellosis: Most cases - self-limiting, does cause dysentery but bacteremia is rare.

Question 18

Shigella mediums

Answer 18

• HMS
  
  • Hektoen enteric (HE) agar
  • MacConkey Agar
  • Salmonella/Shigella Agar

Question 19

Salmonella details

Answer 19

• Motile, encapsulated.
• Produce H₂S
• Catalase +; Ferment Glucose
• S. typhi: Infects only humans; fecal-oral spread in food/water. Some people chronically carry it (gall bladder).
• S. enterica are found in animal reservoirs
  
  • Extreme ages, cancer, immunocomp., and low stomach acid increase disease.

Question 20

S. typhi Infection

Answer 20

• Typhoid fever
  
  • Rose spots on the trunk/abdomen
  • Pulse-temperature dissociation
    
    • fever w/ low pulse
  • Treatment: Ceftriaxone, Fluoroquinolones
  • Vaccine: killed bacteria (orally) for travelers to high risk areas.

Question 21

Salmonella Infections

Serotypes Typhimurium and Enteritidis

Answer 21

• Not normal flora
• Gastroenteritis
  
  • Invasive, but self-limiting.
  • Spreads in families.
  • Post infection reactive arthritis occurs.
• Osteomyelitis
  
  • Focal lesions in sickle cell patients (encapsulated strain).

Question 22

Klebsiella:

K. pneumoniae

Answer 22

• Oppurtunist; Ferments lactose+glucose
• Weakly urease +ve
• Catalase+
• EMB agar and MacConkey agar.
• Lobar pneumonia, aspiration pneumonia, aspiration of GI contents.
• Red “currant jelly” sputum
• Resistant to many antibiotics
• Mixture of mouth anaerobes can be due to this bacteria.

Question 23

Yersinia details

Answer 23

• Y. pestis: Common in prarie dogs
• Y. Enterocolitica: Can grow in the cold.
• Y. pseudotuberculosis = similar to Y. enteroc

Question 24

Y. pestis details

Answer 24

• Responsible for several plagues:
  
  • Bubonic Plague: rapidly enlarging bubboes (greek word, “groin”, swollen inguinal region lymph node), fever, conjunctivitis.
  • Septicemic plague - 1st symptom → pulmonary emboli, pneumonic plague (highly contagious), shock with disseminated intravascular coagulation, organ failure.
  • Pneumonic plague - fever, malaise, chest tightness, pneumonia. Cyanosis.
• Treatment: Streptomycin (Doxycycline)

Question 25

*Y. enterocolitica* details

Answer 25

* **Invasive enterocolitis (yersiniosis):** * Contaminated pork, water or milk. * Symptoms: * Fever, abdominal pain, watery diarrhea. * Mimick appendicitis or Crohn's, or post-infectious reactive polyarthritis.

Question 26

**Proteus:** **P. vulgaris and P. mirabilis**

Answer 26

* Swarming motility: * Found in water, GI tract and human feces. * Opportunistic * Produces H₂S; Urease +ve; Cat+; Ferment glc. * Swarming bulls eye on MacConkey agar. * *P. vulgaris -* nosocomial oppurtunist: **UTIs** and **Kidney stones.** * *P. mirabilis* causes **UTIs** and **kidney stones.**

Question 27

Serratia: ## Footnote **Serratia marcescens**

Answer 27

* Ubiquitous in environment. * **Salmon-red pigment** * **Cat+** * MacConkey agar * Nosocomial infections: catheter associated bacteremia, UTIs, wound infections

Question 28

**Bacteroides fragilis** details:

Answer 28

* Short bacilli. Common intestinal bacilli. * Anaerobe, but aerotolerant. * Causes abscess if mucosal barrier is breached. * Anti-phagocytic capsule that aides this. * Usually part of the polymicrobial infections in the GI tract. * **Peritonitis and intraabdominal abscesses (diverticulitis). Lung abscess (aspiration).** * **Appendicitis** * Treatment with metronidazole and quinolone for E. coli or B. fragilis.

Question 29

**Fusobacterium** details:

Answer 29

* Slender, spindle shaped cells * Found in oral cavity and GI tract. * Have potent LPS. * **Abdominal abscesses** * **Acute necrotizing ulcerative gingivitis (ANUG) -** ulcerative oral disease.

Question 30

**Prevotella: Porphyromonas gingivalis** details:`

Answer 30

* Normal oral and genital microbiota. * Melanin production → black colonies. * **Periodontitis** **(gum infection)** * Difficult to treat.

Question 31

**Pseudomonas aeruginosa** details:

Answer 31

* Major nosocomial and opportunistic pathogen: * **Burns cellulitis** with bluegreen pus * **CF lung infection, pneumonia** * **Wound infections,** ulcers, UTIs * Swimmer's ear * **Malignant otitis externa (elderly/diabetics)** * septicemia (**+/- ecthyma grangrenosum),** shock/death.

Question 32

Campylobacter: **C. jejuni and C. coli**

Answer 32

* Corkscrew, flagellated, nose-to-nose seagull wing appearance. * Cat+, Ox+ * **Enteritis or dysentery** * **Guillain-Barre syndrome -** leading cause * **Reactive arthritis** can also follow.

Question 33

**Helicobactor pylori**

Answer 33

* Infects human only - fecal-oral transmission * Some asymptomatic carriers * **Gastritis -** inflammation. * **Gastric and duodenal ulcers** - epigastric pain and reflux. * **Adenocarcinomas, MALT lymphoma** - increased inflammation, ulcer + cancer risk.

Question 34

Vibrio *V. cholerae*

Answer 34

* Noninvasive, prefers alkaline environment. Human fecal contamination of coastal waters. * High infective dose. * Toxin coregulated pili (TCP) for ileal attachment. * **Cholera toxin** * **Cholera** * **Vaccine:** live, attenuated vaccine available.

Question 35

Vibrio *V. parahaemolyticus* details

Answer 35

* Coastal marine or estuarine halophile. * Ingestion of undercooked/raw seafood. * **Gastroenteritis** * Explosive, watery diarrhea (can be bloody), vomiting and fever. * **Wound infections** mild**.**

Question 36

Vibrio *V. vulnificus* details

Answer 36

* **Wound infections/cellulitis** in cuts from shucking oysters or water exposure. * Can become necrotizing fasciitis * **Gastroenteritis** ingesting raw oysters * **Septicemia**, bullous skin lesions, death (in \<24h) in patients with liver or iron-overload conditions.