Bacteriology 12: Legion, Pseudo, Chlam, Mycoplasma Flashcards
Legionella
-gram +/-
-shape
-w/ or w/o O2
-distinct feature
Gram (-)
Bacilli - rod
-O2
-Faculative intracellular: can live and replicate both inside host cells (intracellularly) and outside of host cells (extracellularly) .. inside a Protozoa (amoebas), and macrophage
are known for causing Legionnaires’ disease.
85% of legionnaires’ disease is caused by
Legionella pneumophila
Which bacteria is Ubiquitous in water environments and soil?
Legionella
Legionella bacteria are found in freshwater environments such as lakes, rivers, and streams.
Occur in biofilms in cool, moist areas (AC units)
Pseudomonas
Uq. Saprophytes in soil and water
Pseudomonas can grow in a wide temperature range making them also salt-tolerant man-made water systems like cooling towers, hot tubs, swimming pools.
Also found in contact lens solution, floor mops, dialysis machines, and respirators humidifiers
They like plastic.
Legionella transmission
Transmitted by inhalation of contaminated aerosols
Legionella in the dental practice and as a dentist what must you do?
Found in high-speed hand piece
Must purge water lines for 2 minutes at the start of each day and 20-30 seconds b/w patients = this can decrease levels of bacteria by up to 70%
Warm temperatures (20-45) + stagnation = growth in dental water lines.
properly maintain water reservoir
Legionella pathogenesis
After inhalation, Legionella reaches the alveoli in the lungs, replicating and dividing inside alveolar macrophages—the primary immune cells responsible for engulfing and destroying pathogens.
INTRACELLULAR PATHOGEN
Avoiding Phagosome-Lysosome Fusion:
Normally, once bacteria are engulfed by macrophages, they are enclosed in a vesicle, which would typically fuse with a lysosome to destroy the bacteria. Legionella, however, blocks the fusion of the vesicle with lysosomes, preventing the bacterium from being degraded.
Inside the LCV, Legionella replicates, using nutrients derived from the host cell’s ribosome, mitochondria and endoplasmic reticulum. During this phase, the bacterium multiplies rapidly, forming large numbers of bacteria within the macrophage.
Once the replication cycle is complete, Legionella initiates the lysis (destruction) of the host cell, releasing new bacteria into the extracellular environment. (B/c macrophage growth increases to a point that they can’t sustain life and burst)
The released bacteria can then infect neighboring cells, continuing the cycle of infection
What’s the primary target for legionella?
After inhalation, Legionella reaches the alveoli in the lungs, replicating and dividing inside alveolar macrophages—the primary immune cells responsible for engulfing and destroying pathogens.
INTRACELLULAR PATHOGEN
Legionnaire’s disease
Legionnaires’ disease is a severe form of pneumonia caused by the bacterium Legionella pneumophila.
The pathogenesis of this disease involves the bacteria’s ability to invade and survive within alveolar macrophages in the lungs
multi-lobar pneumonia
Pneumonia Development:
This inflammation leads to the hallmark symptom of pneumonia, where the air sacs (alveoli) become filled with fluid, pus, and immune cells.
This impairs oxygen exchange in the lungs, causing symptoms like:
High fever
Cough (often dry, but can progress to a productive cough)
Can spread to
Gastrointestinal symptoms like nausea, vomiting, or diarrhea (common in Legionnaires’ disease)
Tissue Necrosis: Severe infection can lead to necrosis (death) of lung tissue, further impairing lung function and contributing to respiratory failure in severe cases.
Legionella diagnosis and complications with diagnosis
Diagnosis:
Culture from sputum or lung aspirate (cysteine-charcoal yeast extract agar)NEVER 100% YIELD… this bacteria is an obligate aerobe fastidious which refers to organisms that have complex or specific growth requirements and are often difficult to culture under standard laboratory conditions
Therefore must do
-urinary antigen test = ELISA
-PCR of sputum or aspirate
Legionella treatment
Levofloxacin (Flurooquinolones — Quinolones — DNA gyrase function — nucleic acid antigen)
Azithromycin (Macrlides — 50S — protein synthesis)
Pseudomonas Aeruginosa
-gram +/-
-shape
-w/ or w/o O2
-distinct features
Gram -
Rod- bacillus
Facultative anaerobe - non-fermenters
-CAN GROW IN A WIDE TEMP RANGE
They can also grow in man-made water systems like cooling towers, hot tubs, swimming pools.
Contact water lens solution - they like plastic
An oxidase test would distinguish pseudomonas from
Enterobacteria (we saw this bacteria in the Eosin agar test fermenting a small amount of lactose compared to some gram - bacteria that were highly lactose fermenters)
Pseudomonas are also Salt-tolerant
Pseudomonas growth characteris
-Metallic sheen and fruity odor
Pigments include:
Pyocyanin
Pyoverdin
These pigments contribute to its virulence and ability to produce reactive oxygen species (oxidase test) that damage host tissues.
-B-hemolytic (S.auerus and S.pyogenes)
Pseudomonas virulence factors
-Exotoxin A in the outer membrane b/c gram (-) duhhhhhhh. This outer membrane will have porins (regulation of passage) allowing for these exotoxins to be released and making it impermeable increasing antibiotic resistance.
-Alginate which is a polysaccharide produced by Pseudomonas that contributes to the formation of a slime layer in biofilms.
-Elastases: These enzymes break down elastin, damaging lung tissue and blood vessels.
-B-lactamase: providing antibiotic resistance. Highly resistant to disinfectants and commonly used antibiotics.
-**Rhamnolipid: inhibits the activity of the ciliated cells in the respiratory tract
Pseudomonas colonizer of
Colonizer of **GI tract*
Colonizer of mouth in patients w/ dysbiosis in their microbiota
Pseudomonas epidemiology in dental clinics
Found on dental unit water lines
-immunocompromised dental personnel and patients at risk
similar to Legionella which are also found water lines of dental practices. Legionella is commonly found on high-speed hand piece primarily
