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1. Vinnitsa National Pirogov Memorial Medical
University/ Department of microbiology
Lecturer: ass.-prof.Vovk I.M.
Main pathogens causing infectious
arthritis, osteomyelitis. Laboratory
diagnostics.

2. Infectious arthritis is an infection of one or more joints
that can be caused by bacteria, viruses, fungi, and
parasites
It`s classified as:
1. Acute bacterial arthritis
2. Acute viral arthritis
3. Chronic infectious arthritis

3. Acute bacterial arthritis
• Infection can be acquired from
hematogenous dissemination,
direct joint inoculation, or a
contiguous focus.
• Monoarticular mostly
• Mainly the knee is affected
Pathogens:
1. Staphylococcus aureus,
Streptococcus spp.
2. Gram-negative bacteria ( in
neonates, the elderly, intravenous
drug users, and
immunocompromised)
3. Neisseria gonorrheae in young
adults, more often in females

4. Acute viral arthritis
• As usually acute
polyarticular arthritis that
occurs simultaneously with
other systemic symptoms of
viral infection
• Main pathogens: parvovirus
B19, rubella virus, hepatitis
B, hepatitis C, and
alphaviruses, including
chikungunya virus, Ross
River virus, and
o’nyongnyong virus

5. Laboratory diagnostics: synovial fluid assay
A sample is taken during a
procedure called an arthrocentesis
Normal data:
• Clear
• Colorless or pale yellow
• Stringy
• Free of bacteria, viruses, and
fungi
• Cells: 0-150 cells/µL
• Crystals: absent
Arthritis:
The synovial fluid may be
cloudy or thick.
• A high white blood cell count
could mean you have an
infection or another medical
condition.
• A high uric acid level and
crystals could signal gout
• A high red blood cell count
could result from:
– Injury
– Blood in the joint
– Bleeding disorder

6. Microscopy of synovial fluid
Normal cells, found in synovial fluid: A-
neutrophils; B-lymphocytes; C –
monocytes/histiocytes; D – synovial lining
cells
Normally WBC in synovial fluid are presented
by 48% monocytes,24% lymphocytes,
macrophages 10%, neutrophils 7%, synovial
cells 4%)
Synovial fluid microscopy with acute
inflammation signs: WBC up to 105,
neutrophils are more then 50%
Synovial fluid microscopy with septic
arthritis: WBC up to 2x105, neutrophils
are more then 90%

7. • Microscopy
• Bacteriological investigation:
– Gram stain
– Culture method, antibiotic susceptibility tests
• Molecular genetic assay at viral arthritis (PCR)
• Other methods: plain film radiography.
– computed tomography or magnetic resonance
imaging is recommended.

8. Copied from Musculoskeletal Key: Synovial Fluid Analyses, Synovial Biopsy, and

9. Pathogen Prefered Antibiotic Alternative Antibiotic
Staphylococcus spp.,
Streptococcus spp.,
Enterococcus spp.
Vancomycin Daptomycin or Linezolid
Neisseria gonorrheae Ceftriaxone Cefotaxime
Gram-negative non-
fermentating rods
Ceftazidime or
Cefepime or
Piperacillin-tazobactam
Aztreonam or
Ciprofloxacin (levofloxacin)
or Dorepenem
Risk factors for resistant
pathogens
Vancomycin +
Ceftazidime or Cefepime
Daptomycin or linezolid
plus
Piperacillin-tazobactam or
Azteronam or
Ciprofloxacin or
Dorepenem
Joint drainage by repeat aspiration, arthroscopy, or arthrotomy is required

10. Usually monoarticular
Large peripheral joints
Mostly in immunocompomised or chronically ill
patients
Pathogens:
Mycobacterium tuberculosis, atypical mycobacteria
Fungi: Candida spp., dimorphic fungi (e.g.,
Blastomyces, Coccidioides, Histoplasma, and
Sporothrix), Cryptococcus, and Aspergillus

11. • Therapy of M. tuberculosis arthritis is similar to
pulmonary tuberculosis.
• Many fungal arthritides are difficult to treat and
result in chronic joint disability. Treatment varies by
infecting organism. Experience using the azoles
(including new triazoles) and the echinocandins is
growing, and in many cases, these drugs are
replacing amphotericin.
• Except for Cryptococcus and Sporothrix, fungal
arthritis requires surgical drainage and débridement.

12. Osteomyelitis is an inflammation of the bone tissue caused by an
infectious agent.
It s can develop as the result of:
1. contiguous spread from adjacent soft tissues and joints ( diabetic foot
infections, lesions at peripheral vascular disease
2. hematogenous seeding (more often in children),
3. direct inoculation of microorganisms into the bone as a result of trauma or
surgery (open fracture, prosthesis or osteosynthesis).
Classification:
The Lew and Waldvogel classification is based on the duration of illness (acute
versus chronic), the mechanism of infection (hematogenous vs. contiguous),
and the presence of vascular insufficiency
Acute osteomyelitis is associated with inflammatory bone changes caused by
pathogenic bacteria, and symptoms typically present within two weeks after infection.
Necrotic bone is present in chronic osteomyelitis, and symptoms may not occur until six
weeks after the onset of infection, recurrent episodes are typical

13. A, B – acute osteomyelitis with abscess formation; C – sequestrum formation at
chronic osteomyelitis

14. Acute osteomyelitis is mostly diagnosed in children
because of hematogenous spreading.
Hematogenous osteomyelitis is monomicrobial
Contiguous osteomyelitis is polymicrobial and mostly
diagnosed in adults
High-risk groups: diabetes mellitus, vascular
insufficiency
Chronic osteomyelitis is resistant to therapy because of
microbial biofilms formation on the bone tissue

15. • The diagnosis of osteomyelitis is suspected on clinical
grounds.
• Confirmation usually entails a combination of radiologic,
microbiologic, and pathologic tests.
• Computed tomography or magnetic resonance imaging (MRI),
are considered standard of care in the diagnosis of
osteomyelitis.
• Bone biopsy or needle aspiration is best for organism
identification (gold standard).
• Repeated swab cultures of the same organism from draining
wounds and sinus tracts may be of diagnostic benefit. Single
investigation may be false-positive due to isolation of skin
bacteria, also negative cultures are obtained in 50% of cases

16. S.aureus is the most common cause of hematogenous
osteomyelitis in adults and children
GAS (group A streptococci), Streptococcus pneumoniae and
Kingella kingae took second place in children
GBS (group B streptococci) may cause osteomyelitis in neonates
Contiguous osteomyelitis may be caused by S.aureus,
P.aeruginosa, Serratia marcescens, E.coli
Fungi and mycobacteria can be isolated from immunocompomised
and diabetes mellitus patients
Propionibacterium acnes may be associated with osteomyelitis
with osteosynthesis
Salmonella spp. and other gram-negative bacteria may be cause of
osteomyelitis in patients with hemoglobinopathies

17. Osteomyletis Main pathogens Management
Osteomyelitis after a
contaminated open
fracture
Staphylococcus spp.,
gram-negative non-
ferments
early aggressive wound irrigation
and débridement, administration
of parenteral and local
antimicrobials, fracture fixation,
and soft tissue coverage of
exposed bone.
Vertebral
osteomyelitis and
spondylodiskitis
S. aureus, coagulase-
negative staphylococci,
Mycobacterium
tuberculosis, and Brucella
spp.
A 6-week course of parenteral
antimicrobial therapy without
surgery.
Osteomyelitis in
patients with diabetes
mellitus or vascular
insufficiency
Polymicrobial a combination of broad-spectrum
antimicrobial regimen and surgical
débridement
Acute hematogenous
osteomyelitis
S.aureus a 2- to 3-week course of
antimicrobial therapy

18. Bacteria First line AB Alternative AB
Staphylococci (MSSA, MSSE) Oxacillin or cefazoline Vancomycin or rifampin
Staphylococci (MRSA, MRSE) Vancomycin or Daptomycin Linezolid or levofloxacin plus
rifampin
Streptococci (penicillin sensitive) Penicillin G or ceftriaxone or
cefazoline
Vancomycin
Enterococci Penicillin G or ampicillin plus
gentamycin
Vancomycin plus gentamycin
Enterobacteria Ceftriaxone or ertapenem Ciprofloxacin or levofloxacin
Pseudomonas aeruginosa Cefepime plus meropenem or
imipenem
Ciprofloxacin or ceftazidime

19. • Mandell, Douglas and Bennett`s Infectious Diseases Essentials, [edited by ]
J.E.Bennett, R.Dolin, M.J.Blaser. -Elseiver, 2017. – 520 p.
• Diagnosis and Management of Osteomyelitis/J. Hatzenbuehler, T J.
Pulling//Am Fam Physician. 2011 Nov 1;84(9):1027-1033.
• A.L.L. Lima et al. Recommendations for the treatment of osteomyelitis// Braz
J Infect Dis. (2014). – Vol. 18 (5). 526-534.
• Synovial Fluid and Synovial Fluid Analysis/ S.Watson//
https://www.webmd.com/arthritis/synovial-joint-fluid-analysis
• Synovial fluid analysis in the diagnosis of joint disease/P.Hermansen,
T.Freemont//Diagnostic Histopathology (2017). – vol.23 (5). – 211-220.
• N.Kavanagh et al. Staphylococcal Osteomyelitis: Disease Progression,
Treatment Challenges, and Future Directions//Antimicrobial Agents and
Chemotherapy (2018) https://doi.org/10.1128/CMR.00084-17