Batterjee Medical College. Dr. Manal El Said Ass. Prof. of Medical Microbiology Non Lactose-Gram...

Batterjee Medical College

Dr. Manal El SaidDr. Manal El Said Ass. Prof. of Medical Microbiology

Non Lactose-Gram Negative Bacilli

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.

•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

Pathogenesis

Salmonella typhi

• 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

• TSI agar shows alkaline slant and acid butt, with no gas and a small amount of H2S.

Salmonella typhi

• 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.

Salmonella typhi

• 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

• 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

Salmonella enteritidis (Salmonella enterica)

Diseases

Characteristics

• Enterocolitis.• Sepsis with metastatic abscesses.

• Produces H2S.

• Motile.

Pathogenesis

• Habitat is the enteric tract of humans & animals, e.g., chickens & domestic livestock.

• Transmission is by the fecal–oral route.

• 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.

Laboratory Diagnosis• Gram-stained smear and culture.

• Non–lactose-fermenting colonies on MacConkey's agar.

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.

Laboratory Diagnosis• TSI agar shows alkaline slant & acid butt, with gas & H2S.

• 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.

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.

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

Characteristics

Enterocolitis (dysentery).

• Nonmotile

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)

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

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.

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 .

Prevention•Public health measures.•No Prophylactic drugs.•No vaccine.

Dr. Manal El SaidDr. Manal El Said

Proteus Species

Head of Medical Microbiology Department

•UTI

•Sepsis

Proteus Species (e.g., P. vulgaris, P. mirabilis)

Diseases

Characteristics

• Highly motile.

• Produce urease.

• Habitat is the human colon & environment (soil & water).

• Transmission to urinary tract is by ascending spread of

fecal flora.

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)

•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

• TSI agar shows an alkaline slant and acid butt with H2S.

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.

Prevention

• No vaccine or drug is available.

• Prompt removal of urinary catheters helps prevent urinary

tract infections.

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.

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)

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

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.

•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

• 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

Batterjee Medical College. Dr. Manal El Said Ass. Prof. of Medical Microbiology Non Lactose-Gram...

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