Musculoskeletal Microbiology Flashcards

Terms Definitions
An infection of the bone characterized by inflammatory destruction, necrosis, and inhibition of new bone formation. Maybe acute or chronic.
Hematogenous osteomyelitis
Blood-borne. Most common in children. Common in long bones and vertebrae. ESR and C reactive protein levels elevated.
Osteomyelitis secondary to Contiguous infection
Bacteria introduced by trauma. Increasing pain accompanied by mild fever. Imaging is not usually diagnostic. Most commonly poly microbial. Staphylococcus aureus, Streptococcus pyogenes, enterococcus, Pseudomonas in chronic cases.
Diabetic foot infections
Osteomyelitis secondary due to vascular insufficiency. Pain and fatigue in the area of previously traumatized skin but may have no pain due to advanced neuropathy. Poly microbial or single bacterial cost. Seen on radiograph. Usually Staphylococcus aureus.
Crackling or grading feeling or sound in joints indicating an infection with anaerobes or Enterobacteriaceae
Staphylococcus aureus
Gram-positive cocci. Catalase positive. Co positive. Virulence factor is protein A which binds to constant region of IgG Ab. preventing Ag binding. Capsule to evade phagocytosis. Enterotoxin. Antibiotic resistance due to beta lactamase enzyme & penicillin binding protein.
Strep agalactiae
Osteomyelitis in infants. Gram-positive cocci in chains. Beta-hemolytic. Catalase negative. Lancefield system. Hydrolyzes hippurate. Virulence factors; anti-phagocytic. Bacitracin resistant.
Streptococcus pyogenes
Osteomyelitis and children. Beta-hemolytic. Normal flora of Respiratory tract. Capsule
Group of streptococci but not a species. Alphahemolytic. Usually commensals
Streptococci pneumoniae
Diplococci or short chains. Alphahemolytic. Big capsule
Gram-positive cocci. Antibiotic resistance is common.
E. coli
Osteomyelitis in infants. Gram-negative bacilli. Grow on MacConkey agar.
Alpha hemolysis
Partial hemolysis
Beta hemolysis
Complete hemolysis
Gamma hemolysis
No hemolysis
Haemophilus influenza
Osteomyelitis in children. Small gram-negative coccobacilli. Polysaccharide capsule. Grows on chocolate agar. Virulence factors: capsule, proteases, endotoxin
Osteomyelitis in sickle cell disease. Motile gram-negative rods. Clear colonies on McConkey's agar. H2S positives. Virulence factors: H,K,O-Ag
Osteomyelitis in immunosuppressed patients. Atypical bacteria. Filamentous like structure. Acid-fast bacteria, strict aerobes.
Pseudomonas aeruginosa
Motile gram-negative rods. Widely disbursed in soil and water. Invasive and toxigenic. Important nosocomial pathogen. Intestine & skin normal flora. Obligate aerobe, oxidase positive, non-glucose fermenter and non-lactose fermenter. Osteomyelitis immunosuppressed
Pseudomonas aeruginosa virulence
Pigment production. Highly resistant to multiple antibiotics. Violence factors: alginate slime prevents phagocytosis, Exotoxin a prevents protein synthesis, irons sequestering mechanisms, biofilms
Coccidioides immitis
Osteomyelitis in endemic areas. Dimorphic fungus. Systemic mycoses. Giants spherules with thick walls or septate hyphae. Endemic cause of pneumonia in Southwest US
Histoplasma capsulatum
Osteomyelitis in endemic areas. Dimorphic fungus: tuberculate macroconida at 25°C or yeast at 37° C. Carried in bat guano and bird droppings. Endemic cause of pneumonia in Ohio/Mississippi River Valley
Septic arthritis
Joint destruction due to viruses, fungi, or bacteria. Either gonococcal or nongonococcal. Normally due to direct inoculation. s aureus is most common. Neisseria gonorrhea is common in young adults.
Reactive arthritis
Sterile inflammatory process in the joint often a result from infection at a distant site
Disseminated gonococcal infection
1 – 3% of patients with N. gonorrhoeae develop disseminated disease, bacteria in blood, as one of two syndromes: 1) tenosynovitis, dermatitis, polyarthritis 2) monoarticular arthritis w/NO skin lesions
Thayer Martin plates
Chocolate + ant'cs followed by gram stain. N. gonorrhea stains small grayish to colorless and mucoid. N. meningitidis stain large bluegray and mucoid
N. gonorrhea
Gram-negative diplococci. Resistant to complement. Sequesters iron. Cleaves IGA, for transmitting to through mucosal surfaces.
Mycobacterium tuberculosis
Associated with chronic monoarticular arthritis. Bacteria are seeded in joint via the blood. Infection may involve tendons and pulmonary system. Anaerobic acid-fast bacillus, no gram classification but may stain +
Lowenstein – Jensen agar
Used to grow Mycobacterium tuberculosis. Slow-growing.
Sporothrix Schenckii
Chronic monoarticular arthritis. Most common fungal agent. Rose handlers disease. Joint is "boggy "decreased range of motion but is not red or tender
Tissue nematodes from ingestion of undercooked meat that Contain larvae, in particular pork or wild game.
Nursing Trichinella
Upon muscle cell entry Trichinella form a "nurse cell "which protects and nourishes the parasitic larvae and is considered a cyst
Symptoms of Trichinella
Early stages: gastroenteritis, diarrhea, nausea. Conjunctivitis &edema of upper eyelids. Splinter hemorrhages. Malaysia, weaknesses, rashes. Eosinophilia is also common.
Diagnosis of Trichinella
Eosinophilia as early as two weeks postinfection. Elevated creatine kinase, aldolase, LDH due to increased permeability/damage to infected muscle cells. Tissue biopsy serves as definitive diagnosis and larva can be viewed.
Trypanosoma cruzi
Flagellated protozoan that causes both acute and chronic Chagas disease. Found in South and Central America.
Vector for Chagas disease
Reduviid (kissing bug). Associated with poor housing. Passed through insect fecal matter.
T. cruzi symptoms
Initially results in a chagoma, erythematous lesion at bite site. Acute inflammatory reaction often on face near eyes. Romana's sign: edema of the eyelid. Fever, myalgia, fatigue, rash.
Amastigotes of T. Cruzi
An intra-cellular form of the parasite that lacks flagella and infects muscle cell. Small rounded cells containing a nucleus and Kinetoplast. 8-12 wks post acute infection
Chronic chagas
Causes cardiac and digestive manifestations typically 10 to 30 years after initial infection. Can cause arrhythmia, dilation, cardiac failure, ventricular dysfunction. Digestive symptoms include dilated esophagus and dilated colon.
Reactivated chagas disease
Occurs in immunocompromised patients such as HIV, transplant recipients, immunosuppressed. HIV patients often get meningeoencephalitis, CNS involvement
Diagnosis of Acute Chagas disease
Detection of trypanosomes in blood, isolation & PCR for T. Cruzi DNA.
Diagnosis of chronic chagas
Patient's serum is tested against T. cruzi using indirect fluorescent assay or EIAs. Trypanosome are rarely found in periphial blood since amastigote are intracellular structures
Toxoplasma gondii
Complex protozoan that infects warm-blooded species, most common infection in the world. Oocytes are ingested and the cyst ruptures releasing Tachyzoites into small intestines which disseminate to all the organs, including muscle and form tissue cysts with Bradyzoites.
T. Gondii transmission
Undercooked meat, congenital, transfusion, cat fecal contamination
Congenital toxoplasmosis
Serious birth defects can result from perinatal infections if the mother is acutely infected with toxoplasma during pregnancy
Diagnosis of toxoplasmosis
Serology IgM and IgG and PCR for toxoplasmosis DNA. In AIDS patients encephalitis may develop.
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