Infectious Diseases Plate Rounds 8-7.pptx

Infectious Diseases Plate Rounds 8-7.pptx

1. Plate Round Discussion August 7, 2024.

2. Case Study 1. Lyme Serology and Western blot – MRN: 105703449. 2. Granulicatella adiacens – MRN: 117761492. 3. Mycobacterium tuberculosis – MRN: 117856539.

3. Borrelia burgdorferi   Lyme disease is a tick-borne infection caused by spirochetes in the Borrelia burgdorferi and transmitted to humans by the bite of Ixodes/Deer ticks. The tick’s natural hosts are deer, rodents, mammals and birds. Transmission season for Lyme disease in Michigan typically occurs from May through August , with a peak in June . Blacklegged ticks have a 2-to-3-year life cycle. During this time, they go through four life stages : Egg , Larva , Nymph , and Adult .

4. Lyme disease is characterized by three stages , not all of which occur in any given patient. The first stage , early localized , is characterized by erythema migrans (EM) (“bull’s eye” appearance). The second stage , early disseminated , beginning weeks to months after infection, may include arthritis, but the most important features are neurologic disorders and carditis (spread of spirochetes to organs and tissues). Third stage , late disseminated , is usually characterized by chronic arthritis or acrodermatitis chronica atrophicans (ACA) .

5. begins with an immunoassay detecting IgM and /or IgG antibodies to B. burgdorferi. A variety of different immunoassay formats have been FDA-cleared for first tier testing (e.g., enzyme, fluorescent, chemiluminescent, lateral flow , etc. If the initial first tier immunoassay(s) are negative, no further testing is necessary. If the total IgM/IgG immunoassay are positive or equivocal, reflex testing by immunoblot is required. Negative results may occur in patients recently infected (<14 days). If recent infection is suspected, repeat testing on a new sample collected in 7-14 days is recommended. CDC recommends a two-step serologic testing process using FDA-cleared assays .

6. Treatment of Lyme Disease Lyme disease is treated with antimicrobials with activity against B. burgdorferi. Treatment of Specific Manifestations of Lyme Disease.

7. Granulicatella spp previously known as nutritionally variant Streptococci, are unable to multiply without the addition of pyridoxal hydrochloride ( also called thiol or vitamin B 6 ) These Streptococci have been associated with bacteremia and endocarditis . Subculturing to a 5% sheep blood agar plate and overlaying a streak of Staphylococcus aureus will produce the supplement generally allows colonies of the Granulicatella to grow as tiny satellites next to the streak. Granulicatella adiacens

8. Granulicatella spp. Habitat (Reservoir) Normal microbiota; Oral cavity and upper respiratory tract. Mode of Transmission Endogenous strains: gain access to normally sterile sites. Spectrum of Disease Endocarditis; also isolated from ophthalmic, central nervous system, peritonitis, musculoskeletal infection, and septic arthritis.

9. Laboratory Diagnosis Granulicatella adiacens is a catalase-negative, oxidase-negative, Pyrrolidonyl arylamidase (PYR) positive, facultatively anaerobic, Gram-positive coccus. Identification Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). VITEK-2 Compact.

10. Treatment The American Heart Association (AHA) recommends penicillin or ceftriaxone, but G. adiacens can develop resistance to beta lactam and macrolide antibiotics. Other options include long-term combination therapy with penicillin and an aminoglycoside, or vancomycin for resistant strains. Some case reports have also used double beta-lactam therapy with ampicillin and ceftriaxone, or teicoplanin and ceftriaxone. 

11. Mycobacteria tuberculosis Tuberculosis (TB) is caused by a bacterium called Mycobacterium tuberculosis.

12. AFB Microscopy Staining Techniques The cell wall of Mycobacteria contain long-chain multiple cross-linked fatty acids call mycolic acids. These contribute to the characteristic of acid-fastness that distinguishes mycobacteria from other bacteria. Two basic techniques: same principle: 1. Fluorescence: Auramine staining – Also known as Fluorochrome staining – Contrast light & dark 2. Brightfield: carbol fuchsin staining – Contrast red AFB on blue or green background

13. Clinical and Laboratory Diagnosis for Tuberculosis There are two kinds of screening tests for TB: Mantoux - tuberculin skin test (TST) and Blood test - interferon gamma release assay (IGRA). Further tests to determine if an infection is active: Lab tests on sputum and lung fluid. Chest X-ray . Computed tomography (CT) scans .

14. Therapy Therapy directed against M. tuberculosis depends on the susceptibility of the isolate to various antimicrobial agents. To prevent the selection of resistant mutants, treatment of tuberculosis requires four drugs: Isoniazid, Rifampin, Ethambutol, and Pyrazinamide. Initial therapy includes all four drugs for 8 weeks. This is the preferred therapy for initial treatment, followed by isoniazid and rifampin for an additional 18 weeks. The most common two-drug regimen is isoniazid and rifampin.

15. Thank you!