Gram Negative Bacterias

Question 1

Diplococci

Answer 1

Aerobics

• Maltose utilization: Neisseria meningitidis
• No maltose utilization : Neisseria gonorrhoeae and Moraxella

Question 2

Coccobacilli

Answer 2

• Haemophilus influenzae
• Bordetella pertussis
• Francisella Tularensis

Question 3

Bacilli

Answer 3

*Lactose fermentation: Fast: Klebsiella and E. Coli and Enterobacter.
Slow: Citrobacter, Serratia

*No lactose fermentation: oxidase neg: Salmonella, Proteus, Shigella, Yersinia.
Oxidase pos: Pseudomonas

Question 4

Comma-shaped rods

Answer 4

They are oxidase positive

• Grows in 42C: Campylobacter jejuni
• Grows in alkaline media: Vibrio cholerae
• Produces urease: Helicobacter pylori

Question 5

Neisseria meningitidis

Answer 5

KIDNEY BEAN-SHAPED Diplococci gram negative

Large capsule, ferments maltose
Grows on chocolate agar in 5% CO2 atmosphere.
*Reservoir: nasopharynx
* transmission😷: respiratory droplets
* Cause: -meningococcemia: abrupt onset with fever, chills, malaise, prostration, and petechial rash and gangrene of toes. Stiff neck and vomiting. - meningitis on babies.
*Dx: gram stain of the CSF, PCR, Latex agglutination
*Tx: neonats/ infants: ampicillin and cefotaxime.
Adults: ceftriaxone with or without vancomycin

Question 6

Oxidase test

Answer 6

The oxidase test is used to identify bacteria that produce cytochrome c oxidase, an enzyme of the bacterial electron transport chain.

Question 7

Neisseria gonorrhoeae

Answer 7

Diplococci gram negative, metabolized glucose and produce IgA proteases.

• No capsule
• No maltose fermentation
• Transmission: sexually or perinatal
• Cause: GONORRHEA, neonatal conjunctivitis, pelvic inflammatory disease (PID), urethritis in males, fitz-Hugh-Curtis syndrome
• Prevention: condoms, erythromycin eye ointments in new borns.
• Dx: genetic, culture on Thayer-Martin medium
• Tx: ceftriaxone + (azythromycin, for possible chlamydial coinfection)

Question 8

Gonorrhea

Answer 8

Uptodate

Question 9

Fitz-Hugh-Curtis syndrome

Answer 9

Uptodate

Question 10

Moraxella catarrhalis

Answer 10

Third common agent causal for otitis media/ sinusitis on children.

Tx: augmentin
Bactrim

Question 11

Haemophilus influenzae

Answer 11

Cocobacillary gram negative, unencapsulated.

• Transmission: aerosol
• most common agent causal of epligottitis, otitis media, conjunctivitis, bronchitis/pneumonia and meningitis. (EMOP)
• produces IgA protease.
• Tx: augmentin for mucosal infections, ceftriaxone for meningitis, rifampin for close contacts like prophylaxis.

Question 12

Epiglottitis

Answer 12

Causal agent: H. Influenzae
Symptoms:
Signs: cherry red on endoscopy, thumbprint signs in the x Ray
Uptodate

Question 13

Bordetella pertussis

Answer 13

Whooping cough

Uptodate

Question 14

Legionella pneumophila

Answer 14

• weakly gram -
• pleomorphic rods, requiring cysteine and iron
• water organisms, transmission by environmental water source habitat.
• treatment: macrolides or quinolone
• legionnaire’s disease

Question 15

Legionnaire’s disease

Answer 15

SEVERE ATYPICAL PNEUMONIA often unilateral and lobar

• transmission aerosols from contaminated air conditioning or water.
• predisposing factors: smokers, chronic lungs disease, alcoholism.
• symptoms: pneumonia, mental condition and diarrhea.
• Dx: direct fluorescent antibody (DFA)
• tx: quinolone, azythromycin, erythromycine

Question 16

Tularemia

Francisella tularensis

Answer 16

Endemic in USA. Arkansas and Missouri
Zoonosis: reservoir wild animals like rabbits, deer and rodents
*transmission :
-Tick bite: ulceroglandular Disease: fever, ulcer at bite site and regional lymph node enlargement and necrosis.
-aerosols: pneumonia
-Ingestion: undercooked , infected meat or contaminated water.
*Dx: culture
*Tx: streptomycin

Question 17

Whooping cough

Answer 17

Bordetella pertussis 
Coco bacilli gram negative encapsulated
Virulence due to pertussis toxin. Inhibiting negative regulator of Gi ADP-ri 
*Disease: whooping cough
*transmission: respiratory droplets
*Prevention: vaccine DTAP 
Most common in children, but could appears in adults. 12-20% afebril adults with cough>2weeks have pertussis. 
*tx: azythromycin

Question 18

Pseudomona aeruginosa

Answer 18

Gram - bacilli, non lactose fermentation, oxidase positive.

Causes: 
Pneumonia
Sepsis
Ecthyma gangrenosum
UTIs
Diabetes, drug use
Osteomyelitis
Mucous polysaccharide capsule
Otitis externa (swimmer's ear)
Nosocomial infections
A exotoxin 
Skin infection (hot tub folliculitis)

Question 19

Campylobacter jejuni

Answer 19

Comma or S shaped gram negative rod with polar flagella ,
Oxidase +
Grows at 42C
Most common agent causal of bloody diarrhea .
Fecal oral transmission or undercooked contaminated poultry or meat
*symptoms: ten or more stools/day, abdominal pain, malaise, nausea, vomiting and fever
*complications : Guillain-Barré syndrome or reactive arthritis
Dx: culture in skirrow agar at 42C
*tx: erythromycine, fluoroquinolonas, penicillin resistant

Question 20

Bacteroides fragilis

Answer 20

Patient with abdominal trauma, emergency abdominal surgery which is complicate with septicemia, peritonitis, abscess

Gram negative bacilli anaerobic

Question 21

Vibrio cholerae

Answer 21

Gram negative curved rod with polar flagella
Oxidase positive
Growth on alkaline media
Human colon reservoir
Transmission: fecal oral
Pathogenesis: cholera enterotoxin, activate ADP-ribosylates Gs, increased cAMP, efflux of Cl and H2O.
CHOLERA: Rice water stools, fluid loss 20lts/day
Complication: hypovolemia shock
Dx: clinical, culture on TCBS, oxidase test positive
Tx: fluid and electrolyte replacement , doxycycline or Ciprofloxacin

Question 22

Klebsiella

Answer 22

Bacilli gram negative , oxidase negative, major capsule (some Killers have pretty nice capsule)
Klebsiella pneumoniae: PNEUMONIA, UTI, SEPTICEMIA.
Cause lobar pneumonia in alcoholics and diabetics when aspirated (transmission endogenous)
Dx: Mckonkey culture of sputum (jelly, thick and bloody) , lactose ferment
Tx: Fluoroquinolona

Question 23

Proteus mirabilis

Answer 23

Gram negative rod, flagellar (high motility), non lactose fermenting, urease positive.
Patient with UTI and Lowe back pain or septicemia.
Swarming motility
Reservoir: human colon and environment
Transmission: endogenous
Pathogenesis: urease raise urine pH to cause kidney stones.
Tx: Fluoroquinolona, TMX-SMX or cefepime

Question 24

Yersinia enterocolitica

Answer 24

Gram negative rod, motile at 25C, no motile at 37C, cold growth
Reservoir zoonotic
Transmission : unpasteurized milk, pork.
Disease: ENTEROCOLITIS: -very young febrile bloody diarrhea and pus. -older kids/young adults: PSEUDOAPENDICITIS , - Adults: enterocolitis with post incite sequelae like reactive arthritis
Dx: stool culture, cold enrichment at 25C.
Tx: supportive care and in inmunocompromised Fluoroquinolona or third generation cephalosporins.

Question 25

Family enterobacteriaceae

Answer 25

``` Gram negative rods Facultative anaerobics Ferment glucose Oxidase negative Catalase positive ``` Family Pathogenesis : endotoxins LPS and antigens ( O,H, K, Vi) Dx: blood agar B-hemolytic MacConkey agar: lactose fermentation: + colored colonies Escherichia, Klebsiella, Citrobacter - colorless colonies shigella, Yersinia, salmonella, proteus

Question 26

Escherichia Coli

Answer 26

Gram negative rod, ferments lactose, enterobacteriaceae Oxidase negative *Reservoir: Human colon *Transmission: fecal oral or endogenous *Diseases: UTI (most common cause)(fimbriae) Neonatal septicemia/ meningitis (second cause) (K-cap) Pneumonia (k-capsule) Septicemia (LPS endotoxin) Gastroenteritis : ETEC, EPEC, EIEC, EHEC, EAEC, DAEC

Question 27

E. Coli UTI

Answer 27

* transmission: endogenous and ascend, most common agent causal in women due to anatomy * pathogenesis: Motility , adherence to uroepithelium with the pili and fimbrias * Dx: uroanalisis and urine culture > 10(5) CFU/ml * Tx: Ciprofloxacin (Fluoroquinolona) or sulfonamides. Augmentin some times.

Question 28

E. Coli gastroenteritis | PITCH

Answer 28

-ETEC ( enterotoxigenic e. Coli) traveler's diarrhea Watery diarrhea due to heat-Labile and heat-stable enteroToxins. No inflammation or invasion. Tx: tmp/smx -EIEC ( enteroinvasive e. Coli) microbe invades intestinal mucosa and causes necrosis and inflammation. Dysentery diarrhea (shigella-like ) - EPEC (enteropathogenic) watery diarrhea usually in pediatrics.(second common cause in pediatrics diarrhea) Tx: beta lactams - EHEC (enterohemorragic) O157:H7 most common serotype in US. Bloody diarrhea (dysentery) . Does not ferment sorbitol. Transmitted via undercooked meat, raw leafy vegetables. Tx: NO ATB. Complications: Hemorrhagic colitis and HUS ( hemolytic uremic syndrome) most common in children<5y

Question 29

Shigella

Answer 29

*Patient with acute bloody diarrhea and fever. *Gram (-) bacilli, non-motile, non-lactose fermenters, do not produce H2S *Two types: Shigella sonnei (most common in US) Shigella dysenteriae (most severe disease) * Reservoir: human colon only * Transmission : fecal oral (day care) * Pathogenesis: - Endotoxin (fever) - Shigella invade M cells - Shiga toxin( produce by S. Dysenteriae type 1, neurotoxic, cytotoxic, enterotoxic) * Disease: Enterocolitis/shigellosis Fever, lower abdominal cramps, tenesmu.s, diarrhea first watery then bloody; invasive but rarely causes septicemia;shallow ulcers * Dx: culture win McConkey agar (colorless colonies) * Tx: fluids replacement, severe cases antibiotics

Question 30

Yersinia pestis

Answer 30

``` Gram negative rods with bipolar staining Facultative intracellular parasite Coagulase positive Zoonosis: rodents Potential biofarware agent Human to human transmissions respiratory droplets. -Bubonic plague disease, BLACK DEATH : rapidly increasing fever, regional buboes, conjuctivitis. - Tx: aminoglycosides ```

Question 31

Yersinia enterocolitica

Answer 31

Zoonotic. Gram negative bacilli, non lactose fermenters, non H2S producers. Patient with inflammatory diarrhea or PSEUDOAPENDICITIS Cold climates Unpasteurized milk, pork Disease: ENTEROCOLITIS Transmission: from pet feces (puppies), contaminated milk or pork. DX: stool culture in 25C, cold enrichment TX: usually supportive care

Question 32

Helicobacter pylori Gram negative, helical bacilli, oxidase positive, urease positive, catalase positive

Answer 32

UREASE POSITIVE Reservoir: humans Transmission: fecal-oral, Oral-oral Pathogenesis: motile, urease positive, mucinase, invasive, inflammation. Disease: chronic gastritis and duodenal ulcers: associated with stomach cancer. Dx: biopsy with culture , breath test, serology Tx: 1) omeprazole+amoxicillin+clarithromycin (triple therapy) 2) treat for 10-14 days 3) quadruple therapy: bismuth, proton pump inhibitor (ppi), tetracycline, metronidazole.

Question 33

Peptic ulcer disease

Answer 33

Up to date

Question 34

Salmonella

Answer 34

- Gram negative rods, non lactose fermenters, oxidase negative and can invade the GI tract via M cells of Peyer patches. - Two types: Salmonella typhi, Salmonella spp.

Question 35

Salmonella typhi

Answer 35

Reservoirs: humans only H2S production Flagellar GI manifestations: constipation followed by diarrhea Cause: typhoid fever: rose spots on abdomen, constipation, abdominal pain and fever. Tx: ceftriaxone or Fluoroquinolone

Question 36

Spirochetes

Answer 36

Spiral shaped bacteria with axial filaments. - Borrelia: wright or giemsa stain - Leptospira - Treponema is visualized by dark field microscopy or direct fluorescent antibody microscopy.