Acute infectious diarrheal disease - Nontyphoidal salmonellosis - DONE Flashcards
Nontyphoidal Salmonellae can be aquired from….
animal reservoirs
Transmission is most commonly associated with:
Nontyphoidal salmonellosis
- eating foods contaminated with small amounts of animal feces:
- usually food products of animal origin: eggs, poultry, undercooked ground meat, dairy products
- also fresh vegetables and fruits
- contact with animals or their environments
Risk factors and risk group:
Nontyphoidal salmonellosis
- Salmonella infection is more common in the summer months (June, July, and August) than winter.
- children under 5 years
- infants who are not breastfed
- adults over 65 years old
- people with weakened immune systems
- certain medications (for example, medications which reduce stomach acid) can increase the risk of Salmonella infection
IMAGE
SLIDE 3
Nontyphoidal salmonellosis - Symptoms - acute gastroenteritis:
- symptoms occur 6-48 hours after ingestion of contaminated food or water
- nausea, vomiting
- diarrhea: loose, nonbloody, of moderate volume stools
- fever
- abdominal cramping
Invasive Salmonella infection - Occur in about 8 % of persons with laboratory- confirmed Salmonella infection as:
- bacteremia
- meningitis
- osteomyelitis
- septic arthritis
Nontyphoidal salmonellosis - diagnosis:
is based on isolation of the organism from stool or blood, or otherwise sterile fluids
- stool cultures remain positive for 4-5 weeks after acute infection and in case of chronic carriage (<1% of patients) for more than one year
Nontyphoidal salmonellosis - treatment:
- gastroenteritis is usually self-limited within 3-7 days
- antibiotics usually not recommended - may prolong fecal carriage
- invasive disease
- choices for antimicrobial therapy for severe infections often include fluoroquinolone, third generation cephalosporins, or ampicillin.
Nontyphoidal salmonellosis - prevention:
- don’t rinse raw chicken
- cook chicken to 65F (always use thermometer)
- wash your hands before all meal preparation
- always use soap for effective hand washing
Shigellosis:
Shigellosis is an infectious disease caused by a group of bacteria called Shigella
Shigella:
- Gram-negative
- non-sporeforming
- non-motile bacilli
- belonging to the family Enterobacteriacae.
The genus Shigella includes four species:
- S. dysenteriae
- S. flexneri
- S. boydii
- S. sonnei
What kind of diarrhea does Shigella cause?
All species of Shigella cause acute bloody diarrhea. Immunity is serotype-specific.
Which Shigella species cause relatively mild illness?
S. sonnei and S. boydii usually cause relatively mild illness in which diarrhea may be watery or bloody.
Which Shigella species is the chief cause of endemic shigellosis in developing countries?
S. flexneri is the chief cause of endemic shigellosis in developing countries.
S. dysenteriae type 1:
produces a potent cytotoxin (Shiga toxin)
- causes illness that is more severe, more prolonged, and more frequently
- fatal than is illness caused by other Shigella
- resistance to antimicrobials occurs more frequently than among other Shigella
- it causes large, often regional, epidemics, frequently with high attack rates and high case fatality rates.
Shigella reservoir:
Humans and a few primates are the only reservoir of Shigella
How is Shigella transmitted?
- Shigella are spread by direct contact with an infected person, or by eating contaminated food or drinking contaminated water.
- Flies may also transmit the
organism.
What is the dose required for infection?
Shigella
The high level infectivity springs from low infective dose required for infection
Where does most infections caused by Shigella occur?
Ninety-nine percent of infections caused by Shigella occur in developing countries
Who is most likely to be infected by Shigella?
The majority of cases (~70%), and of deaths (~60%), occur among children less than five years of age.
Where does the outbreaks of Shigella occur in industrialized world?
In the industralized world outbreaks can occur in day care centers and institiution for mentally retarded
Who usually gets the sporadic cases of Shigella?
Sporadic cases occur among travelers returning from endemic areas
Pathogenesis of Shigella:
- active secretion and abnormal water reabsorption - watery diarrhea precedes the dysenteric syndrome
- Shigella invade the colonic epithelium causing its destruction
- this leads to formation of micro-ulcers and inflammatory exudates
- inflammatory cells (polymorphonuclear leucocytes) and blood appear in the stool.
What happens to Shigella once excreted?
Once excreted, the organism is very sensitive to environmental conditions and dies rapidly, especially when dried or exposed to direct sunlight.
What are the four phases of the clinical manifestation of Shigella?
- incubation
- watery diarrhea
- dysentery
- postinfectious phase
Shigella - incubation:
1-4 days, maybe up to 8 days
Shigella - watery diarrhea:
watery diarrhea (may represent the only clinical manifestation): fever, limited watery diarrhea, abdominal pain, malaise, anorexia
Shigella - dysentery:
frequent passage of small volume mucopurulent stools that contain visible blood, abdominal cramps and tenesmus (unproductive, painful straining)
Shigella - postinfectious phase
reactive arthritis can occur
Shigella - Diagnosis:
- routine microscopy of fresh stool is a simple screening test to detect invasive bacterial diarrhea.
The identification of numerous PMNs suggests a bacterial etiology, but does not distinguish shigellosis from disease caused by other invasive bacteria. - definitive diagnosis of Shigella infection can only be made by isolating the organism from stool and serotyping the isolate.
- culture is required to determine antimicrobial sensitivity.
How can definitive diagnosis of Shigella infection be made?
definitive diagnosis of Shigella infection can only be made by isolating the organism from stool and serotyping the isolate
Shigellosis - Treatment:
- Ciprofloxacin is a drug of choice for all patients , irrespective of their age.
- Alternative treatment:
- pivmecillinam
- ceftriaxon
- azithromycin
