Gram negative bacilli Flashcards
Important information about Enterobacteriaceae
*Commensals of the human and animal intestines(not all )
*They are widespread
*Consist of aerobes and facultative anaerobes
*Easily culturable
*Reduce nitrate
*Ferment glucose
*Some have capsules
*
Types of infections
- Endogenous (From own flora )
- Exogenous ( Organisms are transmitted from the outside to the inside eg via contaminated water
Forms of classification 1.Primary Pathogens Capable of causing diseases in anyone -shigella -salmonella -E.coli -Klebsiella pneumonia
- Opportunistic pathogens
* Cause disease under certain condtitions - Ability to ferment
- Non- fermentors
- Motility
- Biochemical reactions
Virulences
*Capsule ( major virulence factor ,anti phagocytotic ,interferes with antigen-binding )
- Lipopolysaccharides
- Lipid A= stimulates macrophages to produce IL 1 and tumor necrosis, shock, and fever
Oligo- lipopolysaccharides
- Urease
- Potent enzyme = changes pH to alkaline > Ca2+ and phosphate precipitates to form renal stones
*fimbriae (PILLI)
allows for bacterial adhesion to the cell surface
Escherichia coli
Epidemiology
*Human intestinal tract and urinary tract
Transmission
- Focal to oral
- Migration up the urethra
Vrulence
- capsule
- Flagella
- Fimbrae
Clinical
- Bactericaemia
- abdominal wounds
- Diarrhea
- neonatal meningitis
Important information about fastidious bacteria
- Organisms with complex requirements (blood or chocolate agar )
- It is necessary to simulate similar natural environmental conditions to prompt growth
- Culture may not always be the best options
They are usually found in flora of the oral cavity or upper respiratory tract
Usually smaller than other GNB Growth requirements
- High [CO2}
- Special environmental conditions and nutrition
H.Influenza
Transmission
- Respiratory droplets
- spreads in overcrowded areas
Epidemiology
* non-capsulated strains occupy the respiratory tract (nasopharynx)
Pathogenesis
- Causes of systemic infections in children
- Most invasive is caused by H.influenza with capsule B
- Enters the Nasopharynx invades the bloodstream and is able to avoid phagocytosis
Clinical
- Pneumonia
- Bacteriaceae
- Meningitis
- otitis media
- conjuctivitis
- epiglottitis
Treatment
Cephalosporins
Growth requirements
*RBC (X factor ,V factor ,chocolate agar
HACEK organisms
Hemophilus spp actinomycetemcomitans / Actinibacilli Cardiobacterium Eikenella corrodens Kingella kingae
They have similar growth requirements and cause similar syndrome
Epidemiology
Part of the oral flora
*Opportunistic diseases
Clinical
- Endocarditis
- septic arthritis
- osteomyelitis
- Bacteremia
Lab identification
*Grow slow
requires prolonged incubation
Pasteurella species
Animal bites
Epidemiology
*Found in animal mouth, respiratory tract, and GIT
Lab identification ‘
- Pleomorphic
- Requires increased [CO2}
- Requires factor V
- Requiresprolonged incubation
Clinical
animal bite
Bordetella pertussis
severe cough
Transmission
Through respiratory droplets
Syndrome
- produces exotoxins that damage the epithelium
- causes whooping cough especially in children under 2
Treatment
Erythromycin
Lab identification
- Gram negative coccobacilli
- Molecular methods are used > PCR
Legionella pneumophila
Location
*live in warm water
Transmission
Through inhalation or ingestion of contaminated water
Syndrome
*Rapidly progresses pneumonia in men with underlying diseases
Treatment
Erythromycin
Accumulates in water pipes
problematic in hotels and rooms that are usually not used, air conditioners
Paeudomonas aeruginosa
non fastidious
Characteristics
- Aerobic
- Mucoid polysaccharide capsule
- oxidative glucose metabolism
- simple nutritional needs
- survives in hydrotherapy baths and swimming pools
Disease spectrum
- Chronic pulmonary infections in cystic fibrosis patients
- septicemia
- ottitis externa infection
- colonise burn wounds
- osteomyliis
- meningitis
Virulence
- Toxins ( exotoxin A , LPS and exotoxins )
- Enzymes : Protease
- Invasins
- Adhesins
usually isolated from cystic fibrosis patients
Burkholderia cepacia
Oppotunistic bacteria in pulmonary diseased patients
nonfastidious
Characteristics
- Aerobe
- Infects patients with respiratory illness
- Seen in those with pulmonary disease and cystic fibrosis and granulomatous disease
- resistant to many antibiotics and aminoglycosides
- Found in aquatic environments
Virulence
*Pilli
adhering
colonizer of fluid used in hospitals
Disease spetrum
- Bacterimia
- UTI( catherters)
- Peritonsitis
- LRT infection
AcineloBACTER BAUMANNI
Found in hospitals
non- fastidious
Character
- Akenilos = unable to move bacterium rod
- Strictly aerobic, gram-negative coccobacillus
- inert in glucose metabolism
- Notable concern in hospitals
- survives in moist and dry conditions
- Can be found in normal fora of health hosts
Pathogenesis
- attaches and secretes toxins and enzymes on epithelial cells
- Enter the body through catheters, open wounds, and breathing tubes
- Colonises the skin, wound, respiratory system, and gastrointestinal tract
They are resistant to most antibiotics
Disease spectrum *nosocomial infections *Pneumonia *urinary tract infections *wound infection *osteomyelitis post surgery *Endocarditis post surgery *endocarditis *
Strenotrophomona maltophilia
Found in hospitals
Characteristics
- obligated aerobes
- Opportunistic pathogen
- requires indwelling of medical devices to cause infection in immune incompetent patients
Pathogens
- low virulence
- pili and proteins ‘
- infections are linked to contaminated catheters, mechanical ventilators, disinfectants solutions, and blood gas, machines
- Colonises fluid in hospitals settings
- ability to survive and multiply within parental nutrition and other types of IV infections
Clinical infections
*Resistant to beta-lactamase
(cant use penicillin) , aminoglycosides, carbapenems making therapy complicated
NB; Suspectiable to only trimethoprim-sulfamethoxazole
- Organisms must be isolated to determine the clinical relevance
*
Predisposing factors and types of infections
non-fastidious
*Indwelling urinary catheter = catheter-associated urinary infections
*Central intravenous catheter = Intravenous related -m bloodstream infection
*Urinary tract instrumentation = urosepsis
*Arterial monitaring devices = primary bacteremia
*Contamination during blood collection = Pseudobacterium
Prolonged antibacterial therapy and prolonged hospital stay = nosocomial or health care infections
Important information about non fastidious bacteria
- Gram-negative bacilli
- Aerobes and obligated aerobes
- Form no spores
- grow on MacConkey agar
- lactose negative
- Some are able to ferment glucose
- Resistant to many antibacterial agents
- Found in immune-compromised patients
Pathogenesis
- Transmission through medical devices
- opportunistic nosocomial agents
Clinicad diseases
- Bacteremia
- Meningitis
- URI
- Pneumonia
Epidemiology
- Ubiquitous
- Found in-hospital devices
- High incidents of death and complications in hosts with co morbidity
- rarely part of human flora
