Module 5 Bacteriology Part 4.1: Salmonella and P. aeruginosa

Salmonella

Antigens cell wall O, flagellar H, and capsular Vi are

important for taxonomic purposes

Enteric fever

a severe, systemic illness, caused by Salmonella Typhi (most common) or Salmonella Paratyphi.

After an incubation period (10-14 days)

fever, malaise, headache, constipation, bradycardia, and myalgia occur.

Typhoidal salmonella (humans)

it can cause typhoid fever and paratyphoid fever

Non-Typhoidal salmonella

it can cause gastroenteritis and extra-intestinal

S. typhi

species that causes typhoid fever

S. Paratyphi A
S. Paratyphi B dTar
S. Paratyphi C

species that causes paratyphoid fever

Enteric fever

fever rises to a high plateau (39°C to 40°C), and

the spleen and liver become enlarged.

Abdominal symptoms: Enteric fever

diarrhea, constipation, and general abdominal pain

Treatment: Uncomplicated Enteric Fever

oral azithromycin

Treatment: Complicated Enteric Fever

parenteral third-generation cephalosporin or fluoroquinolone

Prevention: Enteric fever

• typhoid vaccine

🗸 live, attenuated vaccine (Ty21a) - oral

🗸 Vi capsular polysaccharide vaccine (Vi CPS) - IM

Bacteremia and Other Invasive Salmonella Infections

commonly caused by Salmonella choleraesuis and

Salmonella dublin

Bacteremia

more common among patients with comorbidities, elderly and children

Bacteremia

may lead to meningitis, septic, arthritis, osteommyelitis

Treatment: Bacteremia and Other Invasive Salmonella Infections

third generation cephalosporin (e.g., ceftriazone) and a fluoroquinolone

aorta

largest artery in human body

Endovascular infection

involves the aorta, often associated with atherosclerotic plaques or aneurysms; people older than 50 years have a higher risk of developing such complications.

Treatment: Endovascular infection

IV ceftriaxone, or ampicilin, or a fluoroquinolone for 6 weeks, followed by oral therapy

Enterocolitis (Salmonella Gastroenteritis)

most common manifestation of salmonella infection.

Salmonella typhimurium and Salmonella enteritidis

Common causes of enterocolitis

bacteremia

a rare complication. 2 to 4%

Differential Culture Media

EMB, MCA, or deoxycholate medium. Bismuth sulfite medium permits rapid detection of hydrogen sulfide

Selective Culture Media

salmonella-shigella (SS) agar, Hektoen enteric (HE) agar, xylose-lysine desoxycholate (XLD) agar, or desoxycholate-citrate agar, of all which

Enrichment Media

selenite F broth or tetrathionate broth

Agglutination Test

sera + unknown culture —> clumping

Tube Dilution Agglutination Test (Widal Test)

detects antibodies against the O and H antigens

Carriers

harbor the organisms in the gallbladder, biliary tract, or, rarely, the intestine or urinary tract

Food and drink

source of infection that have been contaminated with salmonella

Pseudomonas aeruginosa

produces pigments like pyocyanin, pyoverdine, pyorubin, pyomelanin

Pseudomonas aeruginosa

Gram-negative

obligate aerobe

Motile

pyocyanin

Produces a non-fluorescent bluish pigment

pyoverdine

Produces the fluorescent pigment which gives a greenish color

pyorubin

dark-red pigment

pyomelanin

black pigment

Pili (fimbriae)

extend from the cell surface and promote attachment to host epithelial cells.

Extracellular enzymes

elastases, proteases, and two hemolysins (a heat-labile phospholipase C and a

heat-stable glycolipid).

Lipopolysaccharide (LPS)

responsible for many of the endotoxic properties of the organism.

Pyocyanin

stimulates the release of interleukin (IL)-8

siderophores

binds iron

Exotoxin A

blocks protein synthesis

type III-secreted toxins

cell death or interfere with host immune response

P. aeruginosa

an opportunistic pathogen

Treatment: P. aeruginos infections

Piperacillinn + tobramycin (aminoglycooside)

aztreonam

carbapenems - imipenem or meropenem

fluoroquinolones - ciprofloxacin

cephalosphorins - ceftazidime, cefoperazone, and cefepime