MP-L10.S1.2B-Infections of the Musculoskeletal System (Lec) PDF

CM 109: INTEGRATED BASIC SCIENCES II (MICROBIOLOGY & PARASITOLOGY) INFECTIONS OF THE MUSCULOSKELETAL SYSTEM DR. KIMBERLY TRISHA R. CONCEPCION | 19 NOVEMBER 2024 TABLE OF CONTENTS...

CM 109: INTEGRATED BASIC SCIENCES II (MICROBIOLOGY & PARASITOLOGY) INFECTIONS OF THE MUSCULOSKELETAL SYSTEM DR. KIMBERLY TRISHA R. CONCEPCION | 19 NOVEMBER 2024 TABLE OF CONTENTS In the setting of implant surgery, microorganisms are inoculated either during the procedure I. INFECTIONS OF THE MUSCULOSKELETAL SYSTEM 1 → If wound healing is impaired, in the early postoperative period II. OSTEOMYELITIS 1 Epidemiology A. VERTEBRAL OSTEOMYELITIS 1 More often in male B. OSTEOMYELITIS IN LONG BONES 2 Microbiology C. PERIPROSTHETIC JOINT INFECTION 3 Typically classified as pyogenic or nonpyogenic However, this distinction is arbitrary D. STERNAL OSTEOMYELITIS 3 → In “nonpyogenic” cases (tuberculous, brucellar), macroscopic E. FOOT OSTEOMYELITIS 3 pus formation (caseous necrosis, abscess) is quite common III. INFECTIOUS ARTHRITIS 4 Table 1. Acute Bacterial Osteomyelitis vs Subacute Vertebral Osteomyelitis A. ACUTE BACTERIAL ARTHRITIS 4 Subacute vertebral B. NONGONOCOCCAL BACTERIAL ARTHRITIS 4 Acute vertebral osteomyelitis osteomyelitis (weeks to (Few days to weeks) C. GONOCOCCAL BACTERIAL ARTHRITIS 5 months) D. SYPHILITIC ARTHRITIS 6 40-50% are caused by Mycobacterium tuberculosis E. MYCOBACTERIAL ARTHRITIS 6 Staphylococcus aureus or Brucella species in region F. FUNGAL ARTHRITIS 7 12% by Streptococci where these microorganisms G. VIRAL ARTHRITIS 7 20% by gram-negative are endemic bacilli-mainly Escherichia coli Viridans streptococci - these IV. SKELETAL TUBERCULOSIS 7 (9%) and Pseudomonas infections most often occurs A. SPINAL TUBERCULOSIS 7 aeruginosa (6%) as secondary foci in patients B. TUBERCULOSIS OF HIP JOINTS AND KNEE 8 with endocarditis V. PYOMYOSITIS 8 IV drug users who do not use sterile paraphernalia VI. GAS GANGRENE 8 → Candida species VII. NECROTIZING FASCIITIS 8 Implant-associated spinal osteomyelitis → Coagulase-negative VIII. REFERENCES 9 → Staphylococci and C. acnes I. INFECTIONS OF THE MUSCULOSKELETAL SYSTEM PRECEPTOR NOTES Osteomyelitis Acute vertebral osteomyelitis - less than 2 weeks Infectious arthritis Subacute vertebral osteomyelitis - 2 weeks to 6 weeks Skeletal TB Take note of Staphylococcus aureus, Streptococci, Escherichia coli Pyomyositis and Pseudomonas aeruginosa Gas gangrene IV Drug users - fungal infections Necrotizing fasciitis II. OSTEOMYELITIS Manifestations An infection of bone Fever >38° (>100.4°F) Three mechanisms can underlie osteomyelitis Back pain is the leading initial symptom → (1) hematogenous spread The location of the pain corresponds to the site of infection: → (2) spread from a contiguous site following surgery → The cervical spine in ~10% of the cases → (3) secondary infection in the setting of vascular insufficiency or → The thoracic spine in 30% concomitant neuropathy → The lumbar spine in 60% Adult Neurologic deficits, such as radiculopathy, weakness, or sensory → Vertebral column - most affected loss Children Neurologic signs and symptoms are caused mostly by spinal → Long bones generally involved epidural abscess Implant associated Table 2. Early Onset vs Late Onset Early onset Late onset Within 30 days >30 days Wound healing impairment and Fever is rare fever are the leading findings Low-virulence organisms such S. aureus is the most common as coagulase-negative pathogen staphylococci or C. acnes as typical infecting agents Diagnosis These tests are helpful in excluding vertebral osteomyelitis: Figure 1. Vertebral column and long bones Retrieved from Doc Concepcion’s Lecture (2024). → Increased erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP) level A. VERTEBRAL OSTEOMYELITIS → Leukocytosis and neutrophilia Also known as: In view of this low rate positive blood culture after antibiotic treatment → Disk-space infection → Should be withheld until microbial growth is proven unless the → Septic diskiitis patient has sepsis syndrome → Spondylodiskiitis In patient with negative blood cultures → Spinal osteomyelitis → CT-guided or open biopsy is needed Most common manifestation of hematogenous bone infection in Bone samples should be cultured for aerobic, anaerobic, and adults fungal agents, with a portion of the sample sent for histopathologic In adults, the disk is avascular study Microorganisms invade via the segmental arterial circulation in Imaging procedures adjacent endplates and then spread into the disk → Important tools not only for the diagnosis of vertebral Alternative routes of infection are retrograde seeding through the osteomyelitis but also for the detection prevertebral venous plexus and direct inoculation during spinal ▪ e.g., bone metastases or osteoporotic fractures surgery, epidural infiltration, or trauma Trans # 10 B4: Mirabete, Molina, Navarro, Perdigon, Perez, Rawat, Romano, Santos, Sardovia, Tapel, Tolentino TH: Luna 1 of 19  Plain radiography is a reasonable first step in evaluating patients without neurologic symptoms meropenem (1-2g IV q8h) → May reveal an alternative diagnosis → Useful in subacute or chronic cases Pseudomonas aeruginosa Cefepime or ceftazidime (2 g IV MRI q8h) plus an aminoglycoside → Gold standard or → Should be performed expeditiously in patients with neurologic Piperacillin-tazobactam (4.5 g IV impairment q8h) plus an aminoglycoside for ▪ To rule out a herniated disk or to detect pyogenic complications 2-4 weeks in a timely manner followed by Ciprofloxacin (750 mg PO q12h) PRECEPTOR NOTES MRI - gold standard diagnosis for osteomyelitis Anaerobes Clindamycin (600 mg IV q6-8h) for 2-4 weeks followed by Clindamycin (300 mg PO q6h) Note: Refer to Appendix for Table 4. Antibiotic Therapy for Osteomyelitis Associated with Orthopedic Devices B. OSTEOMYELITIS IN LONG BONES Consequence of → Hematogenous seeding → Exogenous contamination during trauma (open fracture) → Perioperative contamination during surgery involving bone Figure 2. MRI (Left) and PET/CT (Right) Typically occurs in children Retrieved from Doc Concepcion’s Lecture (2024). In adults, the leading pathogenic source is exogenous infection → Mainly associated with internal fixation devices PRECEPTOR NOTES Left: Epidemiology → MRI from a 53 year-old man suffering from prosthetic aortic In adults, most cases of long-bone osteomyelitis are posttraumatic valve endocarditis (Aggregatibacter actinomycetemcomitans) or postsurgical → In addition, he experienced lumbar pain for 7 weeks → Less frequently → MRI sagittal sequence shows on T1 fat-saturated → Late recurrence arises from hematogenous infections during post-gadolinium image enhancement in the intervertebral disk childhood space (ventral arrow) and a small epidural abscess (dorsal Microbiology arrow) S. aureus Right: → Most commonly isolated in each type of osteomyelitis → PET/CT from same patient 4 weeks earlier In rare cases, mycobacteria or fungal agents are found in patients → PET/CT fusion shows fluorodeoxyglucose uptake at l5 ventral who live or have traveled in endemic regions (small arrow) and dorsal of S1 (large arrow: epidural abscess) → Cryptococcus species → Sporothrix schenckii Differential Diagnosis → Blastomyces dermatitidis The most common alternative diagnosis is erosive → Coccidioides species osteochondrosis Coagulase-negative staphylococci Conditions that may mimic vertebral osteomyelitis → Second most common etiologic agents (after S. aureus) in → Septic bone necrosis implant-associated osteomyelitis → Gouty spondylodiskitis After open fracture → Erosive diskovertebral lesions (Anderson lesions) in ankylosing → Contiguous long-bone osteomyelitis is typically caused by spondylitis gram-negative bacilli or a polymicrobial mixture of organisms Treatment Manifestations The aims of therapy for vertebral osteomyelitis are Pain and Low Grade Fever (1) Elimination of the pathogen(s) → Leading symptoms in adults with primary or recurrent (2) Protection from further bone loss hematogenous long-bone osteomyelitis (3) Relief of back pain Early (100 Retrieved from Doc Concepcion’s Lecture (2024). mg/L in most cases MRI is the current gold standard Diagnosis → For detection of each type of osteomyelitis Blood tests → CRP (elevated levels, ≥10 mg/L) Treatment → Erythrocyte sedimentation rate (elevated rates, ≥30 mm/h) are In cases of deep sternal wound infection sensitive (91-97%) but not specific (70- 78%) → A combined approach using both surgery and antibiotics Synovial fluid cell counts are ~90% sensitive and specific treatment is required → Threshold values of 1700 leukocytes/uL in periprosthetic knee In acute sternal osteomyelitis without hardware infection → A 6-week course → 4200 leukocytes/uL in periprosthetic hip infection In patients with remaining sternal wires α-defensin can be tested in synovial fluid → Treatment duration in generally is prolonged to 3 months → Biomarker is highly specific Tuberculous sternal osteomyelitis is treated for 6-12 months ▪ Useful in confirming PJI Primary sternal osteomyelitis can generally be treated without Three-phase bone scan is very sensitive for detecting PJI but is not surgery specific → In contrast, in secondary sternal osteomyelitis, debridement is CT and MRI detect soft tissue infection, prosthetic loosening, always required and bone erosion E. FOOT OSTEOMYELITIS → Imaging artifacts caused by metal implants limit their use Occurs in patients with diabetes, peripheral arterial insufficiency, or Treatment peripheral neuropathy and after foot surgery Goal of treatment is cure Epidemiology → Pain-free functional joint with complete eradication of the infecting Incidence of diabetic foot infection is 30 - 40 cases per 1000 persons pathogens with diabetes per year Initial IV therapy is followed by long-term oral antibiotics → Efficacious treatment is best defined in staphylococcal implant Risk factors for Diabetic Foot Infections associated infections Peripheral motor, sensory, and autonomic neuropathy Neuro-osteoarthropathic deformities (Charcot Foot) D. STERNAL OSTEOMYELITIS Arterial insufficiency Occurs primarily after sternal surgery (with the entry of exogenous Uncontrolled hyperglycemia organisms) and more rarely by hematogenous seeding or Disabilities such as reduced vision contiguous extension from adjacent sites of sternocostal arthritis Maladaptive behavior Exogenous sternal osteomyelitis after open sternal surgery is also called Deep Sternal-Wound Infection CM 109 INFECTIONS OF THE MUSCULOSKELETAL SYSTEM 3 of 19  Table 5. Acute bacterial arthritis causative agents per age group Infants 100.4°F) Excluding vertebral Please check Table 4 for the antibiotic therapy manifestation of IV drug users who do not use Back pain (initial symptom) osteomyelitis: hematogenous bone sterile paraphernalia → The cervical spine in → Increased infection in adults → Candida species ~10% of the cases erythrocyte → Avascular Implant-associated spinal → The thoracic spine in sedimentation rate Microorganisms osteomyelitis 30% (ESR) or C-reactive invade via → Coagulase-negative → The lumbar spine in protein (CRP) level segmental arterial → Staphylococci and C. acnes 60% → Leukocytosis and circulation in Neurologic deficits neutrophilia adjacent endplates → Radiculopathy, Blood culture after Alternative route: Acute Vertebral Subacute weakness, or sensory antibiotic treatment → Retrograde Osteomyelitis Vertebral loss → Withheld until seeding and (Few days to Osteomyelitis Implant associated microbial growth is direct inoculation weeks) (weeks to proven Vertebral months) EARLY ONSET → If negative Osteomyelitis → Within 30 days ▪ CT-guided or S. aureus: M. → Wound healing open biopsy 40-50% tuberculosis impairment and fever MRI or Brucella are the leading findings → Gold standard Streptococci: species → S. aureus is the → Important for 12% (endemic) common pathogen patients with LATE ONSET neurologic 20% by gram Viridans → >30 Days symptoms (-) bacilli streptococci - → Fever is rare Plain radiography → E. coli (9%) Secondary → Low-virulence → Without neurologic → P. foci in patients organisms such as symptoms aeruginosa with coagulase-negative (6%) endocarditis staphylococci or C. acnes as typical infecting agents Consequence of Typically occurs in S. aureus Pain and Low Grade Similar to vertebral Similar to vertebral osteomyelitis → Hematogenous Children → Most commonly isolated Fever osteomyelitis 4-6 weeks antibiotic therapy seeding Adults Coagulase (-) Staphylococci → Leading symptoms Three-phase bone No surgery is required if patient has good soft → Exogenous → From exogenous → 2nd most common Early (100 mg/L in most → In secondary sternal osteomyelitis, → Contiguous → Re-exploration for characterized by sternal cases debridement is always required extension from bleeding pain, swelling, and MRI is the current gold adjacent sites of erythema standard sternocostal Most patients have arthritis systemic signs and symptoms of sepsis Occurs in patients Incidence of diabetic Correlation is better when S. aureus Risk factors for Diabetic Diagnosed clinically Antibiotic treatment with: foot infection is isolated (40-50%) than when Foot Infections: → Without imaging → Should be based on bone culture → Diabetes → 30 to 40 cases per identification of: → Peripheral motor, procedures If a foot ulcer is clinically infected → Peripheral arterial 1000 persons with → Anaerobes (20-35%) sensory, and autonomic “Probe-to-bone” test → Prompt empirical antimicrobial therapy insufficiency diabetes → Gram negative bacilli (20-30%) neuropathy Diagnosis of foot ▪ May prevent progression to osteomyelitis → Peripheral → Coagulase negative → Neuro-osteoarthropathic myelitis → Risk of methicillin-resistant S. aureus is high neuropathy staphylococcus (0-20%) deformities (Charcot → Highly probable if ▪ An agent active against these strains should → After foot surgery Foot) bone can be directly be chosen (Ex: Vancomycin) → Arterial insufficiency touched with a metal Has not recently received antibiotics → Uncontrolled instrument → Spectrum of the selected antibiotic must Foot hyperglycemia MRI include gram-positive cocci Osteomyelitis → Reduced vision → High sensitivity ▪ Ex. Clindamycin, Ampicillin-Sulbactam → Maladaptive behavior (80-100%) and Has received antibiotics within the past month specificity (80-90%) → Spectrum of empirical antibiotics should Plain radiography include gram-negative bacilli → Sensitivity (30-90%) ▪ Ex. Clindamycin plus a Fluoroquinolone and specificity Has risk factors for Pseudomonas infection (50-90%) is low (previous colonization, residence in a warm → For follow-up with climate, frequent exposure of the foot to water) confirmed FO → An empirical antipseudomonal agent is indicated ▪ Ex. Piperacillin-Tazobactam, Cefepime CM 109 INFECTIONS OF THE MUSCULOSKELETAL SYSTEM 14 of 19 Table 20. Summary of Infectious Arthritis INFECTIOUS ARTHRITIS Disorder Characteristics Epidemiology Microbiology Manifestations Diagnosis Treatment Hematogenous route - - → Most common in all age groups - - - → Nearly every bacterial pathogens are capable of causing septic arthritis Infants → Group B Streptococci, Gram- Negative Enteric Bacilli, & S. aureus ▪ Most Common