normal flora microbiology

Topics: Escherichia coli, Staphylococcus aureus, Pneumonia Pages: 34 (7217 words) Published: September 28, 2014
Intro to Microbiology:
Gram stain:

Gram +
Gram -

Except Listeria has endotoxin
Strep pneumo
VERY Dangerous:
(Some Strange Killers Have Pretty Nice Capsules)
1. Salmonella
2. Strep
3. Kleibsiella
4. Hemophilus B
5. Pseudomonas
6. Nisseria-(largest capsule- most likely cause of any toxicity) 7. Citroacter

Gram (+)Gram (-)

N-acetyl muramic acid (Nam)
N-acetyl glucosamine (Nag) = Peptidoglycan wall
Contains Techtoic Acid → non-toxic

Steps for Gram stain
1. Crystal violet → picked up by gram (+) by peptidoglycan 2. Iodine (sealant) seal the color in
a. Too little won’t adhere to G+
b. Too much might stain G-
3. Wash excess crystal violet with EtOH
4. Sapphrine (pink/red to stain G-)

Endotoxin(Periplasmic Space – contains endotoxin)
Lipoopolysaccharides means (lipid (A) and sugar-(0-antigensaccharides) and the core antigen is variable Once u give antibiotic the condition get worse because endotoxin release cause (inflammation) so in pedriatic pretreat with steroid ( board exam) Destroying outer membrane will first release Lipid A causing pt to get worse before getting better -Severe shock  Gram negative sepsis.

pediatrics- give steroids before antibiotics for bacterial meningitis (dexamethasone BEFORE antibiotics) to keep inflammation down and prevent hearing loss and neuropathies.

Acid Fast Stain:
For Mycolic Acid
Nocardia is partially acid fast and Gram +
Cryptosporidium is protozoa that is partially acid fast.
Only the pathogen will be pink, everything else will be blue.


Gram + or Gram - ??
If the part of the body that is affected is EXPOSED TO O2 → Gram + Aerobe But if Hiding from O2 → Gram + Anaerobe
If part of the body that is affected is NOT EXPOSED TO O2 → Gram – Anaerobe If in both locations with or without O2 → Facultative
Facultative Anaerobe prefers no O2
Facultative Aerobe prefers O2
Anaerobe Clues
Air fluid levels becos they produces/ releases a lot of gas
Bad breath, body odor, Farts
Bleach works by introducing oxygen to the bacteria!!!

Staphlococcus aureus
MCC of skin infections
Cellulitis → Flat red area; + blanching and pain
Oomphalitis → cellulitis around umbilicus of a newborn
Mastitis → cellulitis around breast
Panniculitis → cellulitis as a ring around abdomen
Folliculitis → infection of a hair follicle
Pus at the base of the hair shaft
Carbuncle(boil) → small nodular indurated area with infection (no pus ) Furuncle → hair follicle in the middle of carbuncle(boil) – (no pus) Ballintitis → infection of the head of the penis
Fascitis → Compartment syndrome

Strep pyogenes
S. aureus is the MCC for skin infections except for these 5 cases where it is Strep pyogenes who is responsible First “LINES”
Lymphangitis → infection follows lymphatic channels = “red streak” Impetigo → honey crusted lesions ( if bullous d/t Staph aureus’s elastase activity) Necrotizing fascitis → “flesh eating strep” → Compartment Syndrome Erysepelas infection of subcutaneous fat→ raised edges; do not blanche (vs. cellulitis) Scarlet Fever

“sand paper rash”
Strawberry tongue

Staph epidermidis
Action is under the epidermis where it is the most abundant
Primarily due to:
Shunt Infection
Central Lines
These both penetrate the skin underneath the epidermis

Propriobacterium Acne
Exposed to oxygen but hiding under skin = Gram + ANAEROBE
Affinity for Propionic Acid(sebum) found in sebaceous glands and ferment it Progesterone stimulate sebaceous gland to produce more sebum(oily or waxy matter) + Females > Males
Caused by birth control pills/shots → acne 2 weeks prior to menses More common in pregnancy

Therefore, acne treatment is based on exposure to O2 (Oxy 10) Acne Medications
Start with Oxy 5/10 → Abrasive pads (open pores to O2 ) → ABX treatment: Clindymycin, Erythromycin, Minocycline...
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