Gram Negative Bacterias Flashcards
Diplococci
Aerobics
- Maltose utilization: Neisseria meningitidis
- No maltose utilization : Neisseria gonorrhoeae and Moraxella
Coccobacilli
- Haemophilus influenzae
- Bordetella pertussis
- Francisella Tularensis
Bacilli
*Lactose fermentation: Fast: Klebsiella and E. Coli and Enterobacter.
Slow: Citrobacter, Serratia
*No lactose fermentation: oxidase neg: Salmonella, Proteus, Shigella, Yersinia.
Oxidase pos: Pseudomonas
Comma-shaped rods
They are oxidase positive
- Grows in 42C: Campylobacter jejuni
- Grows in alkaline media: Vibrio cholerae
- Produces urease: Helicobacter pylori
Neisseria meningitidis
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
Oxidase test
The oxidase test is used to identify bacteria that produce cytochrome c oxidase, an enzyme of the bacterial electron transport chain.
Neisseria gonorrhoeae
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)
Gonorrhea
Uptodate
Fitz-Hugh-Curtis syndrome
Uptodate
Moraxella catarrhalis
Third common agent causal for otitis media/ sinusitis on children.
Tx: augmentin
Bactrim
Haemophilus influenzae
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.
Epiglottitis
Causal agent: H. Influenzae
Symptoms:
Signs: cherry red on endoscopy, thumbprint signs in the x Ray
Uptodate
Bordetella pertussis
Whooping cough
Uptodate
Legionella pneumophila
- weakly gram -
- pleomorphic rods, requiring cysteine and iron
- water organisms, transmission by environmental water source habitat.
- treatment: macrolides or quinolone
- legionnaire’s disease
Legionnaire’s disease
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
Tularemia
Francisella tularensis
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
Whooping cough
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
Pseudomona aeruginosa
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)
Campylobacter jejuni
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
Bacteroides fragilis
Patient with abdominal trauma, emergency abdominal surgery which is complicate with septicemia, peritonitis, abscess
Gram negative bacilli anaerobic
Vibrio cholerae
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
Klebsiella
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
Proteus mirabilis
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
Yersinia enterocolitica
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.
Family enterobacteriaceae
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
Escherichia Coli
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
E. Coli UTI
- 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.
E. Coli gastroenteritis
PITCH
-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
Shigella
*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
Yersinia pestis
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
Yersinia enterocolitica
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
Helicobacter pylori
Gram negative, helical bacilli, oxidase positive, urease positive, catalase positive
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.
Peptic ulcer disease
Up to date
Salmonella
- 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.
Salmonella typhi
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
Spirochetes
Spiral shaped bacteria with axial filaments.
- Borrelia: wright or giemsa stain
- Leptospira
- Treponema is visualized by dark field microscopy or direct fluorescent antibody microscopy.
