Batterjee Medical College
Batterjee Medical College
Non Lactose-Gram
Negative Bacilli
Dr. Manal El Said
Ass. Prof. of Medical Microbiology
Batterjee Medical College
Salmonella typhi
Diseases
Typhoid fever.
Characteristics
• Facultative gram-negative rods.
• Non–lactose-fermenting.
• Produces H2S.
Habitat and Transmission
• Habitat is the human colon only.
• Transmission is by fecal–oral route.
Batterjee Medical College
Salmonella typhi
Pathogenesis
•Infects the cells of the reticuloendothelial system, especially
in the liver & spleen.
•Endotoxin in cell wall causes fever.
•Capsule (Vi antigen) is a virulence factor.
•Predisposing factors:
Decreased stomach acid resulting from ingestion of
antacids or gastrectomy.
•Chronic carrier state established in gallbladder.
•Organism excreted in bile
fecal–oral spread to others.
Batterjee Medical College
Salmonella typhi
Pathogenesis
Batterjee Medical College
Salmonella typhi
Laboratory Diagnosis
• Gram-stained smear and culture.
• Non–lactose-fermenting colonies on MacConkey's agar.
The used media selective for Salmonella are SS agar, bismuth
sulfite agar, Hektoen enteric (HE) medium, brilliant green agar
& xylose-lisine-deoxycholate (XLD) agar. They contain both
selective and differential ingredients
Batterjee Medical College
Salmonella typhi
Laboratory Diagnosis
• TSI agar shows alkaline slant and acid butt, with no gas
and a small amount of H2S.
Batterjee Medical College
Salmonella typhi
Laboratory Diagnosis
• Biochemical and serologic reactions used to identify
species.
• Identity by using known antisera against O, H, & Vi
antigens .
• Widal test detects agglutinating antibodies to O & H
antigens in patient's serum, but its use is limited.
Batterjee Medical College
Salmonella typhi
Treatment
• Most effective drug is ceftriaxone.
• Ampicillin & trimethoprim-sulfamethoxazole can be used in
patients who are not severely ill.
• Resistance to chloramphenicol & ampicillin is mediated by
plasmid-encoded acetylating enzymes and β-lactamase,
respectively.
Batterjee Medical College
Salmonella typhi
Prevention
• Public health measures:
- Sewage disposal
- Chlorination of the water supply
- Stool cultures for food handlers
- Handwashing prior to food handling.
• Two vaccines are in common use:
- one vaccine contains purified Vi polysaccharide capsule
- other vaccine contains live attenuated S. typhi
Batterjee Medical College
Salmonella enteritidis
(Salmonella enterica)
Diseases
• Enterocolitis.
• Sepsis with metastatic abscesses.
Characteristics
• Facultative gram-negative rods.
• Non–lactose-fermenting.
• Produces H2S.
• Motile.
Batterjee Medical College
Salmonella enteritidis
(Salmonella enterica)
Habitat and Transmission
• Habitat is the enteric tract of humans & animals, e.g.,
chickens & domestic livestock.
• Transmission is by the fecal–oral route.
Pathogenesis
• Invades the mucosa of small & large intestines.
• Enter blood
sepsis.
• Infectious dose is at least 105 organisms because organism
is inactivated by stomach acid.
• Endotoxin in cell wall.
• Predisposing factors: lowered stomach acidity from
antacids or gastrectomy.
Batterjee Medical College
Salmonella enteritidis
(Salmonella enterica)
Laboratory Diagnosis
• Gram-stained smear and culture.
• Non–lactose-fermenting colonies on MacConkey's agar.
Salmonella enterica ssp. enterica on Salmonella Shigella
(SS) Agar . Lactose negative, H2S positive colonies.
Lactose positive colonies of Klebsiella pneumoniae
(larger) and lactose negative colonies of Salmonella
enterica ssp.enterica on McConkey agar.
Batterjee Medical College
Salmonella enteritidis
(Salmonella enterica)
Laboratory Diagnosis
• TSI agar shows alkaline slant & acid butt, with gas & H2S.
Batterjee Medical College
Salmonella enteritidis
(Salmonella enterica)
Laboratory Diagnosis
• Biochemical & serologic reactions used to identify
species.
• Antisera
is
used
to
identify
by
using
known
in
agglutination assay.
• Widal test detects antibodies in patient's serum to the O
and H antigens of the organism but is not widely used.
Batterjee Medical College
Salmonella enteritidis
(Salmonella enterica)
Treatment
• Antibiotics
not
enterocolitis.
recommended
for
uncomplicated
• Ceftriaxone are used for sepsis depending on sensitivity
tests.
• Resistance to ampicillin and chloramphenicol is mediated
by plasmid-encoded β-lactamases & acetylating enzymes,
respectively.
Batterjee Medical College
Salmonella enteritidis
(Salmonella enterica)
Prevention
• Public health measures
• Do not eat raw eggs or meat.
• No vaccine is available.
Batterjee Medical College
Shigella Species
(e.g., S. dysenteriae, S. sonnei)
Diseases
Enterocolitis (dysentery).
Characteristics
• Facultative gram-negative rods.
• Non–lactose-fermenting.
• Nonmotile
Batterjee Medical College
Shigella Species
(e.g., S. dysenteriae, S. sonnei)
Habitat and Transmission
• Habitat is the human colon only
• No animal carriers
• Transmission is by the fecal–oral route.
Pathogenesis
• Invades the mucosa of the ileum and colon
sepsis (rare)
• Endotoxin in cell wall.
• The infectious dose of Shigella is low (1–10 organisms)
because it is resistant to stomach acid.
• Children in mental institutions & day care centers
experience outbreaks.
• No chronic carrier.
Batterjee Medical College
Shigella Species
(e.g., S. dysenteriae, S. sonnei)
Laboratory Diagnosis
• Gram-stained smear and culture.
• Non–lactose-fermenting colonies on MacConkey's agar.
colonial morphology displayed by Shigella cultivated on a
Hektoen enteric agar .
Fecal flora with Shigella on MacConkey Agar Plates
Batterjee Medical College
Shigella Species
(e.g., S. dysenteriae, S. sonnei)
Laboratory Diagnosis
• TSI agar shows an alkaline slant with an acid butt and no
gas or H2S.
• Identified by:
- biochemical reactions - serology with anti-O antibody.
Batterjee Medical College
Shigella Species
(e.g., S. dysenteriae, S. sonnei)
Treatment
• Fluid & electrolyte replacement.
• In severe cases, ciprofloxacin.
• Resistance is mediated by :
-Plasmid-encoded enzymes: ß-lactamase
ampicillin
-Mutant pteroate synthetase
. sulfonamides
Prevention
•Public health measures.
•No Prophylactic drugs.
•No vaccine.
degrades
sensitivity to
Batterjee Medical College
Proteus Species
Dr. Manal El Said
Head of Medical Microbiology Department
Batterjee Medical College
Proteus Species
(e.g., P. vulgaris, P. mirabilis)
Diseases
•UTI
•Sepsis
Characteristics
• Facultative gram-negative rods.
• Non–lactose-fermenting.
• Highly motile.
• Produce urease.
Batterjee Medical College
Proteus Species
(e.g., P. vulgaris, P. mirabilis)
Habitat and Transmission
• Habitat is the human colon & environment (soil & water).
• Transmission to urinary tract is by ascending spread of
fecal flora.
Batterjee Medical College
Proteus Species
(e.g., P. vulgaris, P. mirabilis)
Pathogenesis
• Endotoxin causes fever and shock associated with sepsis.
• Urease degrades urea to produce ammonia
Ph.
• This leads to stones
- Obstruct urine flow
- Damage urinary epithelium
- Serve as a nidus for recurrent infection (trapping
bacteria within the stone.
• Organism is highly motile
facilitate entry into bladder.
• Predisposing factors are:
-Colonization of the vagina
-Urinary catheters
-Abnormalities of urinary tract (strictures, valves & stones)
Batterjee Medical College
Proteus Species
(e.g., P. vulgaris, P. mirabilis)
Laboratory Diagnosis
•Gram-stained smear and culture.
•Swarming (spreading) effect over
blood agar plate as the organism's
active motility.
•Non–lactose-fermenting colonies on
MacConkey's agar.
• Produces urease
•P. mirabilis is indole-negative
Batterjee Medical College
Proteus Species
(e.g., P. vulgaris, P. mirabilis)
Laboratory Diagnosis
• TSI agar shows an alkaline slant and acid butt with H2S.
Batterjee Medical College
Proteus Species
(e.g., P. vulgaris, P. mirabilis)
Treatment
• Trimethoprim-sulfamethoxazole or ampicillin is often used
for uncomplicated UTIs
• A third-generation cephalosporin should be used for
serious infections.
• The indole-negative species P. mirabilis is more likely to be
sensitive to antibiotics such as ampicillin.
• Resistance is mediated by plasmid-encoded enzymes.
Batterjee Medical College
Proteus Species
(e.g., P. vulgaris, P. mirabilis)
Prevention
• No vaccine or drug is available.
• Prompt removal of urinary catheters helps prevent urinary
tract infections.
Batterjee Medical College
Morganella morganii &
Providencia rettgeri
• Enteric gram-negative rod similar to Proteus species.
• Causes UTIs & sepsis.
• Highly motile & produces urease.
• Indole-positive and more resistant to antibiotics than
P. mirabilis.
Batterjee Medical College
Yersinia pestis
Diseases
Bubonic & pneumonic plague.
Characteristics
• Small gram-negative rods with bipolar ("safety pin")
staining.
• One of the most virulent organisms (very low ID50)
Habitat and Transmission
• Reservoir is wild rodents, e.g. rats.
• Transmission is by flea bite.
Batterjee Medical College
Yersinia pestis
Pathogenesis
• Virulence factors include:
• Endotoxin
• Exotoxin,
• V & W proteins allow organism to grow within cells.
• Envelope (capsular) antigen that protects against
phagocytosis.
Bubo is a swollen inflamed lymph node,
located in the region of the flea bite
Batterjee Medical College
Yersinia pestis
Laboratory Diagnosis
• Gram-stained smear.
• Wayson's stain show typical
"safety-pin" appearance.
• Cultures are hazardous &
done only in specially
equipped laboratories.
• Organism is identified by
immunofluorescence.
• Serologic tests that detect
antibody in patient's serum.
Batterjee Medical College
Yersinia pestis
Treatment
• Streptomycin either alone or in combination with
tetracycline.
• Strict quarantine for 72 hours
Prevention
•Control rodent & avoid contact with dead rodents.
•Killed vaccine is available for high-risk occupations
•Close contacts should be given tetracycline.
Batterjee Medical College
Yersinia enterocolitica
• Gram-negative rods.
• It Causes:
-Enterocolitis (similar to Shigella & Salmonella).
- Mesenteric adenitis (mimic appendicitis)
• Found in domestic animals
• Transmitted by fecal contamination of food.