Shigella and Pseudomonas Lecture Notes


•.mode of transmission

• Person to person

• Four- fingers-flies ,food,feaces

• Pathogenesis

• Limited to gastrointestinal tract without blood invasion.

• Toxin acts early producing non-bloody diarrhoea-

• followed by invasionof mucosa and wall of large intestine terminal ileum leading to necrosis,superficial ulcers .bleeding.

• Clinical picture1-4 days incubation

• Abdominal pain ,diarrhoea, tenesmus and fever.

• stool contains blood ,mucus,pus

• Diagnosis

• Macroscopic examination of stools to detect mucus and blood

• Microscopic examination reveals pus and RBCs

• stool

• Prevention

• No specific prophylaxis

• Prevention by interruption of fecal –oral transmission,

• proper sewage disposal,

• chloronation of water

• and personal hygiene hand washing)

• Treatment

• Restoration of fluid and electrolyte balance in severe cases

• Antibiotics flouroquinolone(ciprofloxacin)drug of choice


• Found in soil and water normal inhabitants of intestine of man

• Morphology-gram negative bacilli highly motile

• Diseases


• Wound infections

• Otitis media

• Pneumonia

• Bacteraemia(hospital or community acquired


Lab diagnosis

• Highly motile

• Culture swarming in successive waves over Nutrient agar plates

• MacConkeys pale colonies

• Urease positive

Proteus gram negative bacilli



Resistant to antibiotics and antibiotic sensitivity test should be done



Cephalosporins for resistant strains


• Habitat-in soil,sewage,water,commensals

• Hot tubs

• in intestine others cause disease


• Wound infections

• Otitis media

• Hospital acquired infection in immunocompromised host

• Grow in aqueous solutions

• Withstand disinfectants

• Morphology

• Gram negative motile bacilli

• Culture

• Aerobe on nutrient agar leading to greenish discoloration due to diffusable pigment


Pyocynin pigment production

• Pseudomonas aeruginosa is an opportunistic pathogen variety of systemic infections, particularly in patients with severe burns ,  cancer

• AIDS patients who are immunosuppressed individuals with cystic fibrosis who are highly susceptible to pseudomonal lung infections. .

• Those who have undergone chemotherapy, have had transplants, or have any of a variety of immunosuppressed conditions are far more at risk for developing bacterial infections due to Pseudomonas aeruginosa, and because this bacteria is relatively resistant to most antibacterial medications, infection can be deadly, particularly when it becomes infection of the lungs or bloodstream.

• P. aeruginosa finds numerous reservoirs:

• disinfectants, respiratory equipment,

• food, sinks, taps, and mops.

• This organism is often reintroduced into the hospital environment on fruits, plants, vegetables,

• as well by visitors and patients transferred from other facilities

• Spread occurs from patient to patient on the hands of hospital personnel,

• by direct patient contact with contaminated reservoirs,

• and by the ingestion of contaminated foods and water.

• When samples of gram-negative bacteria, particularly those that are considered aerobic, are stained, they resist color and typically show up in slides under the microscope as a pink color.

• Aerobic bacteria refers to bacteria that needs oxygen to survive, which Pseudomonas aeruginosa has in ample amounts, particularly in hospital settings.

• hospital equipment, like masks used to give oxygen, breathing apparatus, or catheters for urine.

• Typically most common infections induced by the bacteria are of the bladder, lungs or bloodstream. Inability to produce normal immune reactions to the presence of the bacteria can mean this germ can easily result in extremely grave health conditions.

• Diagnosis of infection

• Pus from lesion maybe greenish blue

• Smears show gram negative bacilli in pus cells

• Culture son nutrient agar show characteristic colonies with greenish discoloration

• Oxidase positive

• Treatment

• Difficult because eof antibiotic resistance

• Antibigram done.

• Aminoglycosides eg gentamycin or amikacin in combination with penicillin


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