batterjee medical college. dr. manal el said ass. prof. of medical microbiology non lactose-gram...
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Batterjee Medical College
Batterjee Medical College
Dr. Manal El SaidDr. Manal El Said Ass. Prof. of Medical Microbiology
Non Lactose-Gram Negative Bacilli
Batterjee Medical College
Typhoid fever.
Salmonella typhi
Diseases
Characteristics
• Habitat is the human colon only.
• Transmission is by fecal–oral route.
Habitat and Transmission
• Facultative gram-negative rods.
• Non–lactose-fermenting.
• Produces H2S.
Batterjee Medical College
•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.
Pathogenesis
Salmonella typhi
Batterjee Medical College
Pathogenesis
Salmonella typhi
Batterjee Medical College
• Gram-stained smear and culture.• Non–lactose-fermenting colonies on MacConkey's agar.
Laboratory Diagnosis
Salmonella typhi
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
• TSI agar shows alkaline slant and acid butt, with no gas and a small amount of H2S.
Laboratory Diagnosis
Salmonella typhi
Batterjee Medical College
• 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.
Laboratory Diagnosis
Salmonella typhi
Batterjee Medical College
• 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.
Salmonella typhi
Treatment
Batterjee Medical College
• 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
Salmonella typhi
Prevention
Batterjee Medical College
Salmonella enteritidis (Salmonella enterica)
Diseases
Characteristics
• Enterocolitis.• Sepsis with metastatic abscesses.
• Facultative gram-negative rods.
• Non–lactose-fermenting.
• Produces H2S.
• Motile.
Batterjee Medical College
Pathogenesis
• Habitat is the enteric tract of humans & animals, e.g., chickens & domestic livestock.
• Transmission is by the fecal–oral route.
Habitat and Transmission
• 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.
Salmonella enteritidis (Salmonella enterica)
Batterjee Medical College
Laboratory Diagnosis• Gram-stained smear and culture.
• Non–lactose-fermenting colonies on MacConkey's agar.
Salmonella enteritidis (Salmonella enterica)
Lactose positive colonies of Klebsiella pneumoniae (larger) and lactose negative colonies of Salmonella enterica ssp.enterica on McConkey agar.
Salmonella enterica ssp. enterica on Salmonella Shigella
(SS) Agar . Lactose negative, H2S positive colonies.
Batterjee Medical College
Laboratory Diagnosis• TSI agar shows alkaline slant & acid butt, with gas & H2S.
Salmonella enteritidis (Salmonella enterica)
Batterjee Medical College
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.
Salmonella enteritidis (Salmonella enterica)
Batterjee Medical College
Treatment
• Antibiotics not recommended for uncomplicated
enterocolitis.
• Ceftriaxone are used for sepsis depending on sensitivity
tests.
• Resistance to ampicillin and chloramphenicol is mediated
by plasmid-encoded β-lactamases & acetylating enzymes,
respectively.
Salmonella enteritidis (Salmonella enterica)
Batterjee Medical College
Prevention• Public health measures
• Do not eat raw eggs or meat.
• No vaccine is available.
Salmonella enteritidis (Salmonella enterica)
Batterjee Medical College Shigella Species (e.g., S. dysenteriae, S. sonnei)
Diseases
Characteristics
Enterocolitis (dysentery).
• Facultative gram-negative rods.
• Non–lactose-fermenting.
• Nonmotile
Batterjee Medical College
Pathogenesis
Habitat and Transmission• Habitat is the human colon only• No animal carriers • Transmission is by the fecal–oral route.
• 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.
Shigella Species (e.g., S. dysenteriae, S. sonnei)
Batterjee Medical College
Laboratory Diagnosis• Gram-stained smear and culture. • Non–lactose-fermenting colonies on MacConkey's agar.
Shigella Species (e.g., S. dysenteriae, S. sonnei)
colonial morphology displayed by Shigella cultivated on a Hektoen enteric agar .
Fecal flora with Shigella on MacConkey Agar Plates
Batterjee Medical College
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.
Shigella Species (e.g., S. dysenteriae, S. sonnei)
Batterjee Medical College
Treatment• Fluid & electrolyte replacement.• In severe cases, ciprofloxacin. • Resistance is mediated by : -Plasmid-encoded enzymes: ß-lactamase degrades
ampicillin -Mutant pteroate synthetase sensitivity to
sulfonamides .
Shigella Species (e.g., S. dysenteriae, S. sonnei)
Prevention•Public health measures.•No Prophylactic drugs.•No vaccine.
Batterjee Medical College
Dr. Manal El SaidDr. Manal El Said
Proteus Species
Head of Medical Microbiology Department
Batterjee Medical College
•UTI
•Sepsis
Proteus Species (e.g., P. vulgaris, P. mirabilis)
Diseases
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
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)
Proteus Species (e.g., P. vulgaris, P. mirabilis)
Batterjee Medical College
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
Proteus Species (e.g., P. vulgaris, P. mirabilis)
Batterjee Medical College
• TSI agar shows an alkaline slant and acid butt with H2S.
Laboratory Diagnosis
Proteus Species (e.g., P. vulgaris, P. mirabilis)
Batterjee Medical College
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.
Proteus Species (e.g., P. vulgaris, P. mirabilis)
Batterjee Medical College
Prevention
• No vaccine or drug is available.
• Prompt removal of urinary catheters helps prevent urinary
tract infections.
Proteus Species (e.g., P. vulgaris, P. mirabilis)
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
Bubonic & pneumonic plague.
Yersinia pestis
Diseases
Characteristics
• Reservoir is wild rodents, e.g. rats.
• Transmission is by flea bite.
•Small gram-negative rods with bipolar ("safety pin")
staining.
•One of the most virulent organisms (very low ID50)
Habitat and Transmission
Batterjee Medical College
Yersinia pestis
• Virulence factors include:
• Endotoxin
• Exotoxin,
• V & W proteins allow organism to grow within cells.
• Envelope (capsular) antigen that protects against
phagocytosis.
Pathogenesis
Bubo is a swollen inflamed lymph node,
located in the region of the flea bite
Batterjee Medical College
Yersinia pestis
• 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.
Laboratory Diagnosis
Batterjee Medical College
•Control rodent & avoid contact with dead rodents.
•Killed vaccine is available for high-risk occupations
•Close contacts should be given tetracycline.
• Streptomycin either alone or in combination with
tetracycline.
• Strict quarantine for 72 hours
Yersinia pestis
Treatment
Prevention
Batterjee Medical College
• Gram-negative rods.• It Causes: -Enterocolitis (similar to Shigella & Salmonella). - Mesenteric adenitis (mimic appendicitis) • Found in domestic animals • Transmitted by fecal contamination of food.
Yersinia enterocolitica