Diabetic Infections

Question 1

Rhizopus oryzae

Answer 1

Mucormycosis
-most acute and fulminant fungal infx known
-Mucormycosis characterized by infarction, necrosis host tissues resulting from invasion vasculature by hyphae
-most common etiologic agent for mucormycosis
-most common clinical form is rhinocerebral mucormysosis
-classically affects diabetics w/ ketoacidosis
-ubiquitous
-affinity for iron-rich, acidic environments
-tropism for blood vessels!
-broad irregularly branched, right-angled rare septations (lack septations)
-ribbon-like or moose antlers’
-sporangiophores up to 1500 mm length, sporangia are *globose, often collapse to umbrella-like form after spore release
-similar morphology to Aspergillus
Labs
-SDA (or sterile bread) can grow anywhere
Virulence
-relatively avirulent
-siderophore rhizoferrin
-ketone reductase
-hyphae (used for penetration)
Treatment
-aggressive surgical debridement + IV lipid amphotericin B + control of diabetes

Question 2

Psudomonas aeruginosa

Answer 2

-Gr- rod
-ubiquitous
-opportunist - HAI’s
-leading cause of *necrotizing otitis externa
Labs
-grows on blood, and macconkey
-mucoid colonies
-odor of grapes or tortilla chips
-some produce pigment, pyocyanin (blue) or pyoverdin (green)
Virulence
-adhesins
-pili
-alginate capsule
-spreading factors
-Exotoxin A
-Siderophores
-biofilms
-intrinsic and acquired antibiotic resistance
-LPS, capsule, smaller porins in OM, efflux pumps, B-lactamases, biofilms

Question 3

Necrotizing otitis externa

Answer 3

-infx of EAC and skull base
-most common in elderly w/ diabetes
-95% caused by P. aeruginosa
-NOT normal microbiota to ear canal, presence INC:
-hot, humid
-water exposure
Symptoms
-begins in EAC–>leads to parotitis, mastoiditis, osteomyelitis of skull base and temporomandibular joint, cranial nerve palsies, meningitis, and death
-severe otalgia, otorrhea
-sometimes temporary hearing loss
Treatment
-*surgical debridement+systemic and topical antibx+control of diabetes

Question 4

Diabetic foot infections

Answer 4

-most common infection in DM
-most frequent cause of non traumatic lower extremity amputation
-most polymicrobial, S. aureaus (often MRSA) primary pathogen
-5-7 diff species
Pathogenisis
-ischemic ulcers, cracks in feet or nail beds–>local cellulitis–>deeper soft tissues–>joints, bones–>systemic

Question 5

Necrotizing fasciitis Type II

Answer 5

• *usu S. pyogenes
• affects any age group
• usu commonty-acquired
• predisposing factors: trauma, chickenpox, IVDAs, burns

Question 6

Necrotizing fasciitis Type I

Answer 6

-more frequent in diabetics
-most often involves feet, w/ rapid extension along fascia into leg
-perineum, head, neck also common sites in diabetics
-it is *polymicrobial (avg 4.6 isolates/specimen, anaerobic+aerobic bacteria) (mostly S. aureus)
-Fournier gangrene (type I) –> perineum
-Cervical necrotizing fasciitis (type I)–> head and neck region
-mostly dental origin
Treatment
-mortality rate w/ optimal tx:
-type I - 20-40%
-type II - 14-34%