Exam 3 Flashcards
Anaerobes
- infections are close to mucosal surface
- foul odor
- produce large quantities of gas
- black color or brick-red fluorescence
- anaerobic infections are usually polymicrobial
G+ spore-forming rods
Clostridium genus
catalase negative (unlike bacillus)
C. perfringens
- boxcar shaped
- double zone of beta hemolysis
- Type A: ingestion of toxin that causes diarrhea and cramps
- Type C: bloody diarrhea with necrotic inflammation of the small intestine (can be fatal)
- can cause myonecrosis aka gas gangrene
- most common isolate in blood cultures
- Egg yolk agar: opaque zone around colony (lecithinase)
C. botulinum
- from canned foods
- causes flaccid paralysis
- botulism
- ingestion of preformed botulin toxin, babies eating honey, wounds
- Toxin A is used for Botox
C. tetani
- heavy swarming with terminal spores
- neurtotoxin inhibits nuerotransmitters
- tetanus
- spastic/rigid paralysis
- TDaP vaccine
C. difficile
- most common isolate in antibiotic-associated diarrhea
- can cause colitis
- develops because normal flora is destroyed by antimicrobials
- nosocomial
- test for toxin production
- CCFA is selective: yellow round glass colonies
G+ non-spore forming rods
Actinomyces
Bifidobacterium
Propionibacterium (P. acnes is a frequent contaminent in blood cultures)
-all three can cause actinomycosis which is when sinus tracts erupt to the surface and drain pus that contains sulfur granules
G- anaerobic bacilli
Bacteroides (most common)
Prevotella
Porphyromonas
Fusobacterium
G- anaerobic cocci (veillonella)
Bacteroides fragilis
- # 1 NF bacteria in human colon
- # 1 causative agent in peritonitis and intra-abdominal abcesses
B. ureolyticus may pit agar
Prevotella melaninogneica
- # 1 bacteria of gingiva (also in vagina)
- turns to a brown-black color over 2-3 weeks
Porphyromonas
- normal flora of the mouth & GU tract
- head/neck infections
Fusobacterium
- oral flora, also in GI, GU, and URT
- sores, foot ulcers, etc
- Lemierre’s disease- can cause clots in jugular vein
- both species fluoresces chartreuse
- resistant to vancomycin
- F. nucleatum- long/thin with pointed ends. lipase negative.
- F. necrophorum- has rounded ends. lipase positive.
Anaerobic cocci
Peptostreptococcus
- brain abscesses, meningitis, pneumonia, and gingivitis
- SPS test: Peptostreptococcus is sensitive & Peptoniphilus is resistant
Anaerobic testing
- best cultures are tissue biopsy or needle aspiration
- rapid processing due to drying out and exposure to O2
- PRAS media to isolate since most anaerobic infections are polymicrobial
Anaerobic chambers
- H2 (5-10%)
- CO2 (5-10%)
- N2 (80-90%)
- palladium coated alumina pellets remove any residual O2
- dessicant absorbs excess water
- indicator: blue or pink when O2 present
KVLB agar
eliminates most Gram negative via kanamycin & most Gram positive via vanco
Kanamycin: sensitivity indicated Bacteroides (except B. fragilis) or Fuso & Veillonella
Vancomycin: sensitivity indicates G+ bacillus or Porphyromonas
Prevotella & B. fragillis are resistant to V & K (black color)
Colistin disc (not on agar): sensitivity indicates same as kanamycin plus Prevotella
BBE agar
- bile
- B. fragilis group
Fluorescence
- Porphyromonas & Prevotella: brick-red
- Fusobacterium & C. dif: chartreuse
- Veillonella: red
Spot indole test
- blue-green = positive
- P. acnes is the only one
Spirochetes
- helical shaped
- unicellular motile bacteria
- usually treat with doxy or tetracycline
Leptospira
- tightly coiled
- L. interrogans causes Leptospirosis (Swineherd’s disease)
- severe systematic disease = Weil’s disease
- zoonotic disease, excreted in urine
- Fletcher’s agar
Borrelia
- loosely coiled
- anthropod borne (Ixodes tick)
- Kelly medium
- microaerophillic
- requires fatty acids for growth
B. recurrentis
- relapsing fever
- can be seen in PB
- death of spirochetes can cause sudden endotoxin release (Jarisch-Herxheimer rxn = flu-like symptoms)
B. burgdorferi
- Lyme’s disease
- Stage 1: bulls-eye rash
- Stage 2: arthritis, meningitis, lesions
- Stage 3: chronic lesions, neurological symptoms, permanent disability
Treponema pallidum
- Syphillis
- can cross placenta (all treponemals can)
T. pallidium: pertenue
- Yaws
- nonvenereal
- lesions on face
T. pallidum: endemicum
- Endemic syphillis (bejei)
- contact with contaminated eating utensils
- resembles Yaws
T. pallidum: carateum
- Pinta
- ulcerative/papulo lesions that depigment skin
Syphillis
- gay male sex
- Primary: chancre at infection site (penis or vagina/cervix)
- contains spirochetes that can be seen in dark field microscopy
- Secondary: widespread macular rash (syphilitic roseola) on palms/soles of feet and condylomata kata (most gray-white plagues with spirochetes)
- Latent: pt is asymptomatic but still infectious
- Tertiary (late): late complications such as CNA issues
- Congenital- intrauterine that causes facial abnormalities such as Hutchinson’s teeth
Chlamydia
- obligate intracellular parasites
- two forms: elementary body (infectious phase) and reticulate body (replicate/non-infectious phase)
C. trachomatis
- most common bacterial STD in the US
- males: urethral discharge, urethritis, conjunctivitis, prostatitis, etc.
- females: cervicitis, PID, conjunctivitis, discharge, can cause infertility
- often asymptomatic**
- other infections: neonatal (Reiter syndrome, passed through birth canal), Lymphogranuloma Venereum (bubo formation, genital/anal papule), Trachoma (blindness..#1 cause of avoidable blindness)
- humans only reservoir
- to dx, mucosa scraping (1st morning urine/vaginal swabs are best)
C. pneumoniae
- TWAR
- via respiratory droplets
- endotoxin
- life cycle promotes infection
- survive in macrophages
- cause recurrent or persistant infections
C. psittaci
- bird chlamydia
- parrot fever
- pneumonia in humans
- via respiratory droplets
Rickettsiae
- obligate intracellular bacteria
- transmission through ticks
- Spotted fever & Typhus group
Spotted Fever Group
- R. rickettsii: Rocky Mt Spotted Fever
- ticks: D. variabilis & D. andersoni
- flu-like symptoms with rash on ankles/wrist- NOT FACE
- R. konorii: Boutonneuse Fever aka Mediterranean spotted fever
- reservoirs are ticks and dogs
- rash on palms/soles of feet/body/face
- Taches noires: black spots at primary site of infection
Typhus group
- R. typhi: endemic typhus aka murine typhus
- oriental rat/cat flea
- flea poops on skin and scratching infects the bite
- R. prowazekii: epidemic louse-borne tyhpus aka Brill-Zinsser disease
- human louse/squirrel flea/louse
- rash all over-including face
Rickettsialpox
- R. akari
- reservoir is house mouse
- vector is mouse mite
- papules form at bite and progresses to a pustule
- rash everywhere except for palms/soles
Scrub Typhus
- causative agent is Orientia tsutsugamushi
- vector- chigger
- reservoir is rat
- tache noire at site of inoculation
- rash IS NOT on face, soles, palms
Anaplasmataceae family
- Ehrlichia: dogs infected with brown dog ticks
- asymptomatic in humans
- can form morulae in cells (in WBC)
- Lone star tick
Coxiella
- C. burnetti
- Query fever
- livestock are reservoirs
- bioterrorism agent
Mycoplasma
- smallest free-living organisms in nature
- do not possess cell walls so cannot Gram stain and extremely sensitive to drying
- resistant to cell wall antibiotics (PCN)
- slow growing, fastidious (need cholesterol & fatty acids)
- dacron swab or freeze @ -70 degrees C
- spread via close contact (aerosols)
- look like fried eggs on agar
M. pneumoniae
bronchitis/pharyngitis
- walking pneumonia (atypical pneumonia- usually asymptomatic)
- adheres to oropharynx cells
- isolation always indicates pathogenicity
- typically not cultured- uses serology
- rx = erythromycin or Z-pak
M. hominis
- urogenital
- requires arginine
- normal flora-opportunistic pathogen
- rx = clindamycin
ureaplasma
- urogenital infections
- meningitis of newborns
- urethritis in men
- requires urea
- rx = erythromycin
ID of Mycoplasma
- on A8 agar: look for fried egg appearance for M. hominis & irregular shaped colonies for ureaplasma
- in liquid media- look for pH change which will turn pink
Mycobacteria
- non-motile
- non-spore forming
- cell wall has high lipid content (mycolic acid) so its resistant to Gram stain
- aerobic
- requires complex media
- divided into two groups: M. tb complex (both are catalase neg and inhibited by NAP) & nonTb mycobacteria (NTMs) and then M. leprae is by itself
M. bovis
- MTB complex
- primary in cattle
- transmission via ingestion of contaminated milk or airborne
- inhibited by T2H and pyrazinamidase (differentiate from M. TB)
- niacin neg
- doesnt reduce nitrate
M. tuberculosis
- MTB complex
- primary TB
- transmitted via airborne droplet
- bacteria gets phagocytsed and can still multiply (+PPD test)
- reactivation can occur in advanced age, immunocompromised, and malnutrition pts (night chills common symptom)
- slow grower: raised dry rough appearance
- cord factor
- optimal growth: 35-37 degrees
- only non-pigment producer that is positive niacin accumulation and reduces nitrate
- positive pyrazinamidase
- converts to nicotinic acid (yellow color)
- treatment: 9 course regimen of isoniazid & rifampin
Miliary tb
spread of bacteria from lungs to bloodstream (M. tb)
M. avium/M. intracellulare
- most common NTM causing tb in the US
- pulmonary disease that resembles TB
- slow growing
- associated with HIV/AIDS pts
- growth in T2H media
M. avium subsp. paraTB: Johne’s disease- chronic diarrhea in livestock
M. kansasii
- 2nd most common cause of NTM lung disease in US
- slow grower
- photochromogenic
- reduces nitrate**
- produces pyrazinamidase
Photoreactivitiy
photochromogens: carotene pigment upon exposure to light
scotochromogens: pale yellow to orange color in dark or light
nonchromogenic: buff of lack of color
M. genavense
- AIDS pts
- enteritis, genital, and soft tissue infections
M. haemophilum
- immunocompromised pts
- not pulmonary
- lymphadenitis and nodules (cutaneous)
M. malmoenese
chronic pulmonary disease and cervical lymphadenitis
M. marinum
-cutaneous infections due to contain with salt water or inadequate chlorinated water
aka swimming pool granuloma
-positive pyrazinamidase
M. scrofulaceum
- cervical lymphadenitis in children
- scotochromogen
- positive urease (differentiates from M. gordonae)
M. simulae
- pulmonary disease in pts with preexisting lung conditions
- parts of Texas
- photochromogenic and produces niacin
M. szulgai
- pulmonary disease similar to TB
- photochromic
M. ulcerans
- nodule that develops into ulcers
- nonchromogenic buff colonies
M. xenopi
- recovered from hot and cold water temp birds and taps
- can grow at 42 degrees
- pulmonary
- scotochromic
M. gordonae
- found in tap water and soil aka tap water bacillus**
- found in clinical specimens but not pathogen
- scotochromogen
Rapid growing species (more than 7 days)
- M. chelonae: M. abscesses group
- opportunistic infections
- cutaneous
- only rapid grower to be be negative for iron uptake
- more drug resistance than others in this group
- 3-day arylsulfatase test and will grow on MAC
- doesnt reduce nitrate
M. leprae
- Hansen’s disease (leprosy)
- two types
- tuberculoid-skin lesions and nerve involvement but spontaneous recovery and
- lepromateous- skin lesions and progressive nerve damange that can lead to deformities and can be fatal
- person to person transmission
- armadillo,mouse feet
specimen collection
early morning respiratory specimen on 3 consecutive days (only 2/3 need to be positive for confirmatory)
digestion/decontamination
- digestion: liquefy the sample so the bacteria can absorb nutrients in media
decontamination: allow the chemical agent to kill non-mycobacterial organisms (mycobacteria survive due to high lipid cellular walls) - samples collected aseptically do not require this (CSF, pleural fluid, joint fluid)
- agents: NAOH & acetyl-cysteine
Staining
acid fast stain (Ziehl-Neelsen)
- carbofuchsin while heating
- acid alcohol (decolorized)
- methylene blue (counter stain)
blue background with red organism**
kinyoun stain is the same except without heat
Medias
Lowenstein-Jensen media
American Thoracic Society media
Middlebrook media
all contain malachite green which suppresses the growth of G+ organisms
BACTEC system
culturing system of mycobacteria
amount of labeled CO2 is detected and interpreted as a growth index
MGIT
same principle as BACTEC but measures O2 consumption via fluorescence
