Listeria, H ifluenzae, P aeruginosa, M tuberculosis, M pneumoniae Flashcards
Clinical history: A 33-year-old female dairy farmer develops a severe headache and neck stiffness. On physical examination, her temperature is 38.2°C. She has no papilledema. A lumbar puncture is performed, and a Gram stain of the CSF obtained shows many short, gram-positive rods.
What is the most likely causative agent in the case above?
Listeria moncytogenes
Listeria appears in animals, skin, food (T/F)
True
Epidemics of Listeria are linked to contaminated food (T/F)
True
Complications
Meningitis
Persons at risk
Pregnant women, infants, elderly
L moncytogenes resembles S pneumoniae (gram +ve diplococci)
True
CAMP results for L moncytogenes
-Strep B produces CAMP factor (protein) that interacts with S aureus to enhance lysis of RBCs.
Group B strep streaked perpendicular to S aureus streak on blood agar
+ve result: –Arrowhead zone of hemolysis
Important diagnostic factor to distinguish S pneumoniae and L moncytogenes
L moncytogenes is catalase positive and all streptococci are catalase negative
Motility pattern
Umbrella motions
Treatment
Ceftriaxone
Vancomycin
Listeria treatment - add in ampicillin and gentamicin
Why is it important to identify if L moncytogenes is the pathogen?
Since Listeria doesn’t respond to usual antibiotic treatment for strep, it is important to identify which it is.
Num 1 cause of community acquired meningitis is L moncytogenes, why?
Neurotropism - An ability to invade and live in neural tissue.
Virulence factors: L moncytogenes
Facultative anaerobe - because it can survive in cells
Survives digestion
Adheres to host cells
Can replicate in macocrophages so can carry bacteria anywhere and cross placenta.
Life cycle: L moncytogenes
Adheres to host cells -> internalize into phagolysosome
Low pH actives O and C = break out of Listeria
Bacteria replicates in cytosol
Creates actin rockets = propelling around cell into cell wall
Neonatal effect: L moncytogenes
- Early onset
- -miscarriage, stillbirth, in utero transmission
Late onset in babies- Listeriosis
- At/shortly after birth
- Meningitis/ meningoencephalitis
A 10-month-old child of a family from Mexico living in Durham was noted by his mother to have a grand mal seizure with shaking of arms and legs by the description given to the EMT. The EMTs found the child limp and unresponsive. In the emergency room the child’s fever was 39.5°C (103.1°F). Blood cultures and lumbar puncture were performed. CSF findings were as follows:
cell count of 4000
95% PMNs
glucose 20mg/dl
protein 125mg/dl.
Gram stain showed PMNs and occasional Gram-negative coccobacillary organisms. The organism grew on chocolate agar but not on sheep blood agar or MacConkey’s agar. What is the most likely organism in this case?
Haemophilus influenzae
Hemophilus influenzae is located where?
Nasopharynx of healthy persons
Cell morphology - H influenzae
Short, gram negative rods/coccobacillus
Non motile
No flagella/pilli
Fastidious
Requirements for growth
X-factor – respiration enzyme
V factor/NAD - oxidation-reduction process
H influenzae ranges of effects on humans:
causes meningitis, primary bacteremia, pneumonia, epiglottitis and arthritis.
Non-Capsulatedinfluenzae(Nc-hi) causes otitis media, conjunctivitis and sinusitis
Causes chronic bronchitis in adults
Specimen
CSF, Sterile site aspirates, fluids, urine, sputum, Respiratory tract specimens.
Diagnosis
Direct:
–Gram -ve, coccobacilli, small rods
Cultivation:
Blood agar - satellitism
Chocolate agar - mucoid colonies
PCR
Done in case of meningitis
Treatment
Num 1 treatment
Cephalosporin (good CSF penetration)
Ceftriaxone + Cefotaxme - used in Meningitis and Septicemia
Amoxicillin - oral - otitis media, bronchitis, sinusitis
Pseudomonas aeruginosa is opportunistic, why?
It affects immunocompromised persons (Cystic fibrosis)
P aeruginosa features
Gram -ve
Rod shaped
Non spore forming
Aerobic
P aeruginosa symptoms
Lungs: pneumonia, coughing, congestion
Blood: Joint pain, stiffness, fever, chills, fatigue
P aeruginosa - virulence factors
Siderophores - iron chelating
Flagella - attachment + invasion of tissue
Pilli - attachment
Exotoxin A - inhibits protein synthesis in host cells
Forming hard to remove biofilms - anaerobic
P aeruginosa - Transmission
Can be transmitted to a host via fomites, vectors, and hospital workers who are potential carriers for multiply-antibiotic-resistant strains of the pathogen.
Which illness does Klebsiella pneumoniae often cause?
Bacterial pneumonia/lung infection (common)
Transmission - K pneumoniae
-When bacteria enters the respiratory tract/spread via hand contact
Community acquired pneumonia (rare) - spread via community setting e.g. mall/subway
Hospital acquired pneumonia - spread at hospital/nursing home
A 52-year-old homeless, alcoholic man had a fever and a cough productive of thick sputum that worsened over several days. His temperature is 38.2°C. Diffuse crackles are heard at the right lung base.
Klebsiella pneumoniae
K pneumoniae features
Gram negative
Enteric - occurs in intestines
Rod shaped
Thick capsule
K pneumoniae usually found where?
Nasopharynx
GIT
K pneumoniae symptoms
Fever Chills Coughing Yellow/bloody mucus Shortness of breath Chest pain
Illnesses caused by K pneuminae
Urinary tract, nosocomial pneumonia and intraabdominal infections
A 4-year-old female had a gradual onset of fever, productive cough, anorexia and diarrhea about eleven days prior to death. The breath sounds were harsh, and a few cracking rales were heard over the right base posteriorly.
Mycoplasma tuberculosis
Where does Mycobacterium tuberculosis usually affect?
Lungs
However, can attack any part of the body such as the kidney, spine, and brain.
Mycobacterium is not acid fast (T/F)
False; have ropelike structures of peptidoglycan that are arranged in such a way to give them properties of an acid fast bacteria.
Lab ID - M tuberculosis
Slow growth - tough cell wall that prevents passage of nutrients
Specimen - sputum
Test - acid fast stain
Treatment -TB
The most common treatment for active TB is isoniazid INH in combination with three other drugs—rifampin, pyrazinamide and ethambutol.
Community acquired atypical pneumonia can be caused by which of the following organisms?
Legionella pneumophilia Staphylococcus aureus Klebsiella pneumoniae Mycoplasma pneumoniae Pseudomonas aeruginosa
Mycoplasma pneuminae
Mycoplasma pneumoniae commonly causes mild infections of the respiratory system (T/F)
True
M pneumoniae are bacteria that lack a cell wall, so they require residence in a host organism (T/F)
True; obtain all essential nutrients to survive via mucosal epithelial cells of the host.
Transmission
Respiratory droplets
Illnesses caused by M pneumoniae
Tracheobronchitis and primary atypical pneumonia
Features - M pneumoniae
Spherical, no cell wall, filamentous
Virulence factors - M pneumoniae
Adhesion proteins - attachment to epithelial cells of respiratory tract
β-lactam antibiotics (ie. penicillin) can’t be used to kill the bacteria, because they target the lyses of the cell wall
