9/16/10 Osteomyelitis

Front 1

Pseudomonas aeruginosa

Back 1

Gram negative rods in pairs and singles

Does Not ferment carbohydrates; Obligate anaerobe
Blood Agar (BAP)- brown colonies, semi clearing
MacConkey Agar- colorless colonies lactose-non fermenting
Nutrient Agar- blue-green colonies

Associated with long term catheterization

Front 2

Hematogenous seeding in Children

Back 2

CA-Staphylococcus aureus, Strep. pneumoniae, Haemophilus influenzae type B

metaphysis

In neonates the most common organisms are group B streptococci and E. coli.

Front 3

Hematogenous Osteomyelitis of the Adult

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In adults hematogenous osteomyelitis most often affects the spine.

S. aureus and coagulase negative Staphylococci

Elderly are also more prone to pelvic infections and theoretically, retrograde flow from pelvic tissues (urethra, prostate, bladder) to lumbar vertebrae can explain the spread of pelvic infections preferentially to lumbar vertebrae.

less likely to have seeding in the long bones.

Front 4

Contiguous-focus Osteomyelitis without Generalized Vascular Insufficiency

Back 4

S. aureus

can be poly microbial including gram-negative bacilli and anaerobic organisms

caused by Surgical reduction, internal fixation of factures, prosthetic devices, soft tissue infections

Front 5

Acute Ischaemic Neuropathic Osteomyelitis and/or Vascular Insufficiency

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Mostly polymicrobial including aerobic and anaerobic organisms: coagulase positive and negative Staphylococci, Streptococcus spp. Enterococcus spp, gram negative bacilli.

causes: Foot ulcer due to neuropathy, vascular insufficiency and hyperglycemia

Front 6

Intravenous Drug Users and Osteomyelitis

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S. aureus, Pseudomonas, Candida, Eikenella corrodens. Also Mycobacterial osteomyelitis is more common in these patients.

Sternoclavicular, sternochondral joint, sacroiliac joint and symphysis pubis

Front 7

Patients with Indwelling Catheters & Hemodialysis patients

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catheters: S. aureus, sacroiliac joint infections

hemodialysis: Vertebral osteomyelitis, S. aureus and S. epidermidis
Oxacillin resistant S. aureus is common in this setting

Front 8

Sickle cell Disease and Osteomyelitis

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Salmonella, S. aureus, other gram negatives

HLA class II DRB 15 is protective while
HLA class II DQB1 03 is susceptible

Patchy ischemic infarction in the bowel due to sickling, permitting transient mucosal barrier breakdown

Long bone and septic arthritis

Front 9

Salmonella

Back 9

Gram-negative facultative, rod-shaped, with peritrichous flagella.

Can be isolated on MacConkey agar
Usually Non-lactose fermenters
Acid and gas from glucose fermentation
Produce H2S

Usually cause two diseases:
Salmonellosis; enteric fever (typhoid)

Front 10

Mycobacterium tuberculosis’ in Spinal Osteomyelitis

Back 10

Acid Fast, rods , intracellular
Resistant to chemicals and drying due to thick cell wall with mycolic acids.

Strictly aerobic and slow growing

Vertebral osteomyelitis due to M. tuberculosis =Pott’s disease

HIV patients, IV drug users and other immunocompromised patients are at risk of Mycobacterium infection

Front 11

Review of Staphylococcus aureus

Back 11

Gram + cocci, non-motile
Catalase +
Facultative anaerobe
β-hemolytic
Salt and Temp tolerant
Golden pigmented colonies
Anti-phagocytic polysaccharide capsule
Coagulase producer

Invasion:
Hyaluronidase, Staphylokinase, Lipase, Dnase

Adherence:
The MSCRAMMS adhesion proteins are important to S. aureus adhesion to host intracellular matrix proteins including that of bone:
Collagen binding protein – cna
Fibronectin binding proteins – fnbA, fnbB, clf A, clfB
Sialoglycoprotein adhesin

Tissue destruction:
Cytolytic toxins: α, β, δ, γ and the P-V leukocidin

Front 12

Penicillin resistant S. aureus

Back 12

Penicillinase encoded by bla

Plasmid encoded and easily transferable

Other B-lactams resistant to penicillinase where introduced
cephalosporin, methicillin, nafcillin

Front 13

MRSA: Methicillin Resistant S. aureus

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Defined as having oxacillin MIC of greater than 4μg/ml

All MRSAs have the mecA gene.
mecA codes for a very low-affinity PBP2A

The transpeptidases link the NAM-NAG chains together by way of a pentapeptides

Diagnosis of MRSA:
MIC testing, growth on Oxacillin agar, disk diffusion tests
PCR analysis for mecA gene

Front 14

VISA and VRSA: Vancomycin intermediate and resistant S. aureus

Back 14

Transposon TN1546 (vanA) is on a multi-resistance conjugative plasmid.

Van A gene products modify the Nam-peptide terminus from D-ala-D-ala to D-ala –D-lactate

The modified precursors don’t bind vancomycin and therefore can be used for cell wall assembly.

Alternative Treatment : Daptomycin

Front 15

Acquiring Antibiotic Resistance

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Conjugation between E. faecalis and S. aureus followed by transposition into the S. aureus multiple drug resistance plasmid..
75% of Enterococcus faecalis isolates are vancomycin resistant (VRE)

Transduction followed by transposition into the multi-drug R plasmid
The TN1545 transposon is self-transferable.