Bacterial, Viral, Fungal, Infection III Flashcards
causes of skin, soft tissue, blood and bone infection
gram negative aerobic and facultative rods
environment where these gram neg aerobic and facultative rods flourish
– Pseudomonas spp.
– Stenotrophomonas maltophilia
– Tap water, hospital flowers, moist lettuce, soil
what can enterobacteriaceae GNR infect
all tissues
resistance that is common in enterobacteriaceae
antibiotic resistance
order of the enterobacteriaceae GNR group and the most pathogenic
- E. coli
- klebsiella (most pathogenic)
- enterobacter spp
feature that klebsiella and enterobacter spp share
Mucoid capsular antigens antiphagocytic
what are the non enterobacteriaceae GNR
pseudomonas aureginosa and acinetobacter baumannii
features of acinetobacter baumannii
- high resistant and originated in iraq
- endotoxin
- wound and blood stream infections
what is pseudomonas toxin similar to
diphtheria toxin
features of pseudomonas
– Naturally resistant to many antibiotics
• metallo-carbapenemase similar to KPC.
– Ability to adapt to almost any growth opportunity.
– Mucoid strains block WBC, & enhance survival
– Can infect skin, soft tissue, bone, blood
exception to requesting specially an anaerobic culture to recover anaerobes
blood cultures which come with both aerobics and anaerobic bottles
what type of infections do anaerobes usually cause
mixed organism infections (mixed with other anaerobes or facultative organisms)
where do anaerobe dominate
in stool of colon
Opportunistic Anaerobic Conditions that Allow Infection
• Tissues devitalized by: –Trauma – Malignancy – Inflammation –Impaired blood supply – Surgery –Foreign body
acceptable specimens for anaerobic cultures
- Abscess fluid aspirates
- Surgically removed tissue
- Blood cultures
how does one get anaerobic cellulitis and what does it contain
dog bite
mixed anaerobic flora including clostridium –> clostridium infection of wounds and surrounding subcutaneous tissue
what is formed in anaerobic cellulitis and what is absent
-marked gas formation but absence of toxicity of gas gangrene
most common Gram-negative rods causing anaerobic infections and second common
Bacteroides fragilis group is most common
fusobacterium sp is second common
what does bacteriodes fragillis have
capsule with antiphagocytic function
more pathogenic non spore forming gram positive anaerobic rods
actinomyces and proprionibacterium
less pathogenic non spore forming gram positive anaerobic rods
– Mobiluncus (may help cause vaginitis)
– Lactobacillus : Normal flora
– Eubacterium
– Rothia
describes actinomyces
long gram pos rods that are often branching (no spores, no acid fast); anaerobes but some are aerotolerant
most common pathogen in serious infection with actinomycetes sp
a. israelii
morphology of a. israelii and how long it takes to grow
molar tooth colony morphology
4-10 days to grow
places other than the oral cavity where actinomyces can cause serious chronic infection
- uterus with contaminated IUD
- thoracic due to aspiration pneumonia
- abscess in neck or head
classic finding seen with pus in actinomyces
sulphur granules - colonies of actinomyces
what are propionibacterium acnes
anaerobic coryneform which grows in hair follicle
what are infections of propionibacterium acnes
– Acne
– Opportunistic infection of prosthetic devices.
– Mixed anaerobic infection
– Can be common blood culture contaminant
laboratory support for diagnosis of gas gangrene
culture and gram stain
tissue biopsy
organism in gas gangrene
clostridium perfringes
characteristics of clostridium perfringes
– Gram positive spore forming rod.
• No spores are seen in stains of tissue.
– Fast growing anaerobic fermenter
• Generates large amounts of H2 & CO2
– Encapsulated and non-motile.
– Found in colon and soil
main pathogenic factor in clostridium perfringes
alpha toxin
what does the alpha toxin in clostridium perfringes do
Diffuses through tissue killing cells thus producing more necrotic growth areas for organism
what are the other toxins of clostridium perfringes
theta toxin and enterotoxin
what does enterotoxin of clostridium perfringes cause
food poisoning
what are importance of theta toxins of clostridium perfringes
– Toxic for heart muscle & capillaries.
– Similar to Streptolysin O in beta strep
other mechanism of pathogenesis of c. perfringes
- fermentation of muscle carbs (produces crepitation which are palpable gas)
- destructive extracelllular enzymes: collagenases, hyaluronidase, DNAse, and protease
when does one get gas gangrene
in severe traumatic wounds
why can’t clinicians wait on lab cultures to diagnose gas gangrene
it is rapidly life threatening so a clinical diagnosis must be made by detecting gas in infected tissue
treatment of gas gangrene
remove infected tissue immediately by surgical debridement and placing drain in wound
what are secondary treatments for gas gangrene
placing patients in hyperbaric oxygen chamber
treat with penicillin
how do neonates acquire strep agalactiae
through passage of the birth canal because about 30% of women have it as part of their normal vagina flora
clinical manifestation of strep agalactiae in neonates
Lethargy, fever, sepsis, meningitis, respiratory distress
clinical manifestation of strep agalactiae in older children and adults
– Puerperal fever at delivery
– Gynecologic surgery infections
– Skin and soft tissue infections
what pyogenic bacteria can cause pharyngitis without any post infection sequelae
beta strep group C and G
results of getting beta strep C and G
skin and soft tissue infections
- infections of wounds
- occasional bacteremia
secondary to some other insult to the lung such as influenza or aspiration
staph pneumonia
types of bacteremia
- transient
- intermittent
- continuous (infective endocarditis, typhoid fever, brucellos and etc)
classification of infective endocarditis
acute, subacute, chronic
signs and symptoms associated with infective endocarditis
• Local infection of valve & tissue damage
• Septic embolization of valvular vegetations
• Continuous bacteriemia
• Cytokine release
• Circulation of immune complexes to distant organs
– Glomerulonephritis
5 major viridian strep group that causes endocarditis
- S. mutans group
- S. salivarius group
- S. anginosus group
- S. mitis group
- S. sanguinis group
viridian mmass
microbes that causes endocarditis
staph aureus, virdians, enterococci, coag neg staph, strep bovis, enterobacteriaceae plus pseudomonas gram neg rods, fungi (candida), and hacek
how to diagnose infective endocarditis
- 2 positive blood cultures before first administration of antibiotics
- on ECG: oscillating intracardiac mass
- petechiae, fever
what do rare causes of endocarditis require for diagnosis
infectious disease consult to identify hard to grow organisms: mycobacterium, rickettsia, fungi
