Gram Intermediate Bacteria Flashcards
List some common Gram-intermediate bacteria (8).
Chlamydia trachomatis Chlamydia pneumoniae Chlamydia psittaci Coxiela burnetii Gardnerella vaginalis Mycoplasma pneumoniae Rickettsia prowazeki Rickettsia rickettsii
Chlamydia species respiration
Obligate intracellular (it cannot create its own ATP)
How do you visualize the Chlamydia species?
Poor gram staining
We can visualize them under microscope with Giemsa Stain
What visual features let you know you are looking at a member of Chlamydia?
We can see inclusion bodies within cells - bunches of reitculobodies dividing in the cell.
What are the 2 forms during Chlamydia’s life cycle?
Elementary bodies (1st form - infectious) and Reticulobodies (2nd form - active form)
Bacteria starts outside the cell in elementary stage. Once the bacteria enters cells they become reticulobodies that are active and can multiply via binary fission. Final stage is the release of newly formed bacteria (elementary again)
How do you diagnose a Chlamydia infection?
NAAT (Nucleic Acid Amplification Test) - fancy word for PCR
What are the 3 subtypes of Chlamydia trachomatis?
A-C: Blindness
D-K: STI
L1-L3: LGV
Chlamydia trachomatis A-C
Leading cause of blindness in entire world
Transmitted by hand to eye contact - fomites (any object that can carry a bacteria from one thing to another - hands)
Chlamydia trachomatis L1-L3
Causes lymphogranuloma venereum (an STD) - less common than D-K.
Infection of lymphatics, specifically inguinal nodes
Starts out with painless genital ulcer, but weeks to months later it presents as tender lymphadenopathy with draining lymph nodes
Chlamydia trachomatis D-K
Most commonly reported bacterial STI in the USA!
Watery discharge is characteristic (Gonorrhea is thicker, with white/purulent discharge)
If left untreated, may lead to PID in women (therefore, it is not so good to be asymptomatic)
If woman has active infection during delivery of baby, the baby can get D-K too.
Presentation in this case is: neonatal conjunctivitis, neonatal pneumonia with a staccato cough
The onset of these neonatal symptoms differentiates chlamydia D-K from gonorrhea:
Chlamydia = 1-2 weeks Gonorrhea = 1st 2-4 days
Long term effects of Chlamydia
Reactive arthritis - body fights bacteria with antibodies that cross react and attack the body. The triad for Reactive arthritis (Reiter’s) is:
1) knee most common
2) Uveitis (infection of eyes)
3) Urethritis
Can’t see, can’t pee, can’t climb a tree
Chlamydophila pneumonaie
one of the 3 atypical pneumonias (Legionella, Mycoplasma, Chlamydia)
Adults
This atypical pneumonia is more common in the elderly than in young adults.
Chlamydia Psittaci
Also transmits pneumonia
From birds like parrots - bird droppings
Chlamydia Tx
Antibiotics are very effective, esp penicillins and others that target cell walls bc the cell walls of chlamydia lack muramic acid.
Macrolides - Azithromycin (treats STI and Trichoma)
Topical macrolides are NOT effective for neonatal conjunctivitis - give them oral form.
Atypical pneumonia can be treated with doxycycline (1st line) or macrolides (2nd)
Coinfection with gonorrhea must be assumed. Treat for both. Always add Cephtriaxone to cover for this.
How do you differentiate a rickettsia infection from a coxiella infection?
Coxiella does NOT cause rash
Coxiella respiration
Obligate intracellular
Random note: It is gram (-)
Coxiella transmission
Contained in spore-like structures in animal feces. Spores are strong enough to survive digestive tract of animals. Transmitted to humans via aerosol transmission.
Farm animals are major reservoir. Farm animal to farmer is common scenario. Also, veterinarian who helped deliver a baby farm animal (exposed to placental secretions)
Coxiella (Q Fever) presentation
Q Fever = Pneumonia + HA + fever + hepatitis*
Q Fever Tx
Usually no antibodies are needed. The infection is self-limiting and goes away in about 2 weeks.
Rarely, a patient with chronic Q Fever can develop endocarditis (esp if immunocompromised or with previous valvular damage)
Prevent this with milk pasteurization
Vets can get an acellular vaccine since they’re high risk.
What disease does gardnerella cause?
Bacterial vaginosis
The gram stain of gardnerella
Gram-variable rod - can stain (+) or (-)
Bacterial vaginosis mechanism
Normal vaginal flora contains lactobacilli with a minority of anaerobic gram negatives. If the balance goes haywire and there’s an increase in anaerobic flora, this overgrowth lowers the amount of lactobacilli. This environment is more suitable for growth of gardnerella vaginalis.
Symptoms of Bacterial vaginosis
Thin, grayish-white, malodorous/fishy discharge
Discharge has pH > 4.5 (avg 5.5-6.5). Normal vaginal secretion pH is 3.8-4.5.
Treat the discharge with a 10% KOH prep which produces an extremely pungent odor (This is a test - The Whiff Test)
On microscopic exam (wet mount of discharge) you will see epithelial cells diffusely coated with bacteria (Clue Cells)
Bacterial vaginosis Tx
Metronidazole
How do you culture Mycoplasma pneumoniae?
Eaton’s Agar
What disease is mycoplasma most associated with?
Walking pneumonia - an atypical pneumonia (like Legionella, Chlamydia)
It is atypical bc you cannot readily culture it and isolate a microbe
Walking pneumonia
Caused by mycoplasma pneumo
Patients have CXR that may show even a severe pneumonia, but they may not appear that sick clinically. May even be walking around.
Normal pneumonia (like from strep pneumo) - Pt would be in bed.
Summary = XR appears much worse than Pts do clinically. Reticulonodular “patchy” infiltrate on XR.
Increased incidence in young adults, esp in areas of close contact (military recruits)
Mycoplasma gram stain
No cell wall = can’t appear on gram stain
Unique feature of Mycoplasma cell membrane
Only bacteria with a membrane that contains cholesterol - makes the membrane stable and flexible.
How do you dx walking pneumonia?
From Mycoplasma
Confirm dx by looking for cold agglutinins. 1-2 weeks into infection, Pts develop IgM molecules that agglutinate erythrocytes in cold temperatures (~4C). These cold agglutinins are present in 50-75% of these patients. The process leads to lysis of RBCs
Walking pneumonia Tx
From Mycoplasma (no cell wall)
Macrolides - azithromycin
Rickettsia respiration
Obligate intracellular - cannot produce CoA and NAD+
These are important for bacterial growth and replication. They must get these nutrients from eukaryotic host.
What do Rickettsia look like?
Coccobacilliary shape
Rickettsia gram staining
Technically gram (-) but it’s weak
Weil-Felix Test
An agglutination test used to diagnosis rickettsial infections. Tests for cross-reactivity btw rickettsial species and proteus vulgaris. It really isn’t very sensitive or specific tho.
General prodromal signs of Rickettsia infection
HA + Fever
Rickettsia infection Tx
Doxycycline (or other tetracyclines)
Describe the rash of Rickettsia prowazeki
Starts on trunk and spreads outward towards extremities.
Rash spares the hands, feet, and head.
Who is most affected by Rickettsia prowazeki infections?
Military camp recruits and POWs
Rickettsia prowazeki transmission
Spread by louse
The lice usually poop near their feeding site on skin. The patient’s scratching introduces the bacteria into the blood
What illness is caused by Rickettsia prowazeki?
Epidemic Typhus (widespread, rampant outbreak)
Rickettsia typhis causes endemic typhus
Symptoms of epidemic typhus
Caused by rickettsia prowazeki
Rash that starts on trunk and moves outward
Myalgia and arthralgia
Pneumonia
Encephalitis with dizziness and confusion
If really serious, coma
Epidemic Typhus Tx
Doxycycline
What disease does Rickettsia rickettsii cause?
Rocky Mountain Spotted Fever
Rocky Mountain Spotted Fever transmission
caused by rickettsia rickettsii bacteria
Spread by ticks - dermacentor tick (direct contact - from the actual bite, not from pooping and scratching)
Rocky Mountain Spotted Fever presentation
From rickettsia rickettsii
Rash does not start immediately - has incubation btw 2-14 days.
Rash begins at extremities and spreads centrally - even on palms/soles
HA, Fever, myalgias
Rocky Mountain Spotted Fever Tx
Doxycycline
