Board Review

1. Board Review Paul O’Keefe April 16, 2003

2. Skin/Soft Tissue Infections • Impetigo • Cellulitis • Fasciitis

3. Impetigo • Group A streptococcus, Staphylococcus arueus • Superficial blistershoney colored crusts on erythematous base • No systemic signs • Mainly in children • May be associated with glomerulonephritis • Treat with penicillin/antistaphylococcal penicillin

4. Cellulitis • Deeper infection usually involving skin and subcutaneous tissue • Erythema, pain and swelling often with distinct border (erysipelas) • Fever and lymphangitis or adenitis common • Gp A streptococcus, Staphylococcus aureus most common • Treat with antistaphylococcal penicillin unless culture positive

5. Necrotizing Fasciitis • Streptococcal gangrene (Gp A strept) • Deeper infection involving fascia and often muscle • Extreme toxicity and rapid spread (“flesh-eating virus”) • May have associated toxic shock • Treatment – surgical removal of necrotic tissue and antibiotics • Penicillin and clinidamycin

6. Staphylococcus aureus Coagulase negative staphylococcus Streptococcus pyogenes Sterptococcus pneumoniae Enterococcus faecalis A three year old boy presents with an itchy rash that is spreading. Afebrile with numerous cursted lesions in erythematous base involving left shoulder and upper chest and back with few lesions in the right thigh. Culture growing gram positive coccus, beta hemolytic on SBA, catalase negative, inhibited by bacitracin disc. The isolated agent is

7. A 13 year old develops high fever and a severely • painful red rash on the right arm beginning at the • site of a minor laceration. He has high fever, hypo- • tension and extreme toxicity. The arm is red, very • swollen, firm and there are areas of black discolor- • ation of the skin. The remainder of the skin has a • red sunburned appearance. The extreme toxicity • is thought to be caused by • Streptolysin O • Hyaluronidase • M Protein • Pyrogenic exotoxin • Peptidoglycan

8. Upper Respiratory Tract Infection • Pharyngitis • Sinusitis • Otitis media

9. Pharyngitis • Viral • Group A streptococcus (S. pyogenes) • Corynebacterium diphtheriae • Infectious mononucleosis

10. Characteristics of Pharyngitis

11. Pharyngitis and Fatigue A 15 year old presents with fever, sore throat and extreme fatigue. Temperature is 103.2 and there is a yellowish exudate covering both enlarged tonsils. Submandibular, anterior cer- vical, and posterior cervical lymph nodes are enlarged on both sides. Which of the following is most characteristic of infectious mononucleosis? • Atypical lymphocytosis • Positive culture for Group A streptococcus • Neutrophilia with left shift • Low serum globulin • Hematuria

12. Sinusitis A 15 yo woman presents with fever, facial pain and severe nasal congestion. She has been suffering with hay fever. CT showed opacification of the R maxillary sinus and an air- fluid level in the left. Gram stain of material obtained by antral puncture disclosed gram negative coccobacilli. Which of the following characterizes the organism most likely respon- sible for the infection? • Requires neither X nor V factor for growth • Requires X factor but not V factor • Requires V factor but not X factor • Requires both X and V factors • Exuberant growth on sheep blood agar

13. Otitis Media A 9 month old child with fever and congestion is diagnosed with right otitis media. Common causes of this infection are? • Gp A streptococcus and Gp B streptococcus • Neisseria meningitidis and Streptococcus pneumoniae • Streptococcus pneumoniae and Haemophilus influenzae • Haemophilus parainfluenzae and Gp A streptococcus • Staphylococcus aureus and Gp A streptococcus

14. Community Acquired Pneumonia • Streptococcus pneumoniae • Mycoplasma pneumoniae • Legionella pneumophila • Haemophilus influenzae • Chlamydia pneumoniae • Tuberculosis

15. Community acquired pneumonia A 33 year old male presents with fever and cough 3 weeks after his 7 year old son was treated for pneumonia. X-ray shows a patchy bronchopneumonia involving the right middle and lower lung field. Cold agglutinin test is positive What is the likely cause?

16. Features of Community Acquired pneumonia

17. Communinty Acquired Pneumonia A 26 year old woman complained of fever, night sweats and cough for 2 months. She had occasional hemoptysis and 15 pound weight loss. Chest x-ray showed fibronodular infiltrates with a cavity in the posterior segment of the right upper lobe. Please answer the following: What type of isolation would you order?What diagnostic tests would you order? Sputum smear returned positive for AFB. What treatment would you order? Why are multiple drugs necessary for treatment of tuberculosis?

18. Food Poisoning

19. Infectious Diarrhea

20. Cause of diarrhea 4 hours after eating fried rice • B. cereus • S. aureus • Salmonella • Shigella • C. jejuni • Yersinia enterocolitica • Vibrio parahemolyticus

21. Contaminated poultry is the most likely source of • Salmonella • Vibrio cholerae • Shigella dysenteriae • Campylobacter jejuni • S. aureus

22. An important virulence factor of the organism found on biopsy of the stomach in patients with chornic epigastric pain is • Enterotoxin • Polysaccharide capsule • Endotoxin • Urease • Beta-lactamase

23. Urinary Tract Infection A 23 year old woman presents with acute dysuria one day after intercourse. Urinalysis discloses 15-20 WBC’s /HPF. Gram stain discloses gram negative rods. What is the recommended treatment? • Penicillin V • Erythromycin • Trimethoprim/sulfamethosoxazole • Gentamicin • Clindamycin

24. Which of the following strongly favors the diagnosis of pyelonephritis? • Burning on urination • Hematuria • Suprapubic tenderness • Fever • WBC casts on urinalysis

25. Causes of Meningitis by Age

26. Meningitis A 6 year old boy presents with fever and lethargy. He has nuchal rigidity on examination. Lumbar puncture discloses many PMN’s and Gram positive cocci in pairs. Which of the following characterizes this organism? • Beta hemolytic on sheep’s blood agar • Inhibited by bacitracin dise • Inhibited by optichin disc • Beta-lactamase positive • Growth on MacConkey agar

27. Vaccines are available to prevent meningitis caused by which organisms ? • E. coli and Streptococcus pneumoniae • Haemophilus influenzae and Listeria monocytogenes • Group B streptococcus and E. coli • Neisseria meningitidis and Haemophilus influenzae • Streptococcus pneumoniae and Group B streptococcus

28. Bone and Joint Infections A 22 year-old woman with sickle cell disease presents with fever and pain in the left upper arm. X-ray of the humerus shows a lytic lesion. Biopsy is growing gram negative Bacilli. Which of the following best describes the organism? • Comma-shaped with single polar flagellum • Motile and oxidase positive • Nonmotile facultative anaerobe • Motile and does not ferment lactose • Coccobacilli that require X and V factors

29. Sexually Transmitted Diseases A 16 year old man presents with burning on urination and a scant urethral discharge 3 days after intercourse with a new partner. Gram stain of discharge discloses many PMN’s but no bacteria. The organism most likely responsible for the infection is • Gram positive coccus, catalase positive • Gram positive coccus, catalase negarive, beta-hemolytic • Has infectious elementary body and intracellular reticulate body • Gram negarive coccus, oxidase positive • Gram negarive rod, ixidase negarive lactose fermenting

30. Arthritis A 29 yo female presents with fever, rash and arthritis 5 days after onset of menses. She has a new sex partner. Exam discloses about 25 papular lesions on distal extremities and inflamed tendon sheaths of the wrists and ankles with painful motion but no fluid in the joints. Cultures of blood and endocervix are growing • Catalase positive, gram positive coccus • Gram negative coccus that ferments glucose but not maltose • Gram negative coccus that ferments glucose and maltose • Gram negative coccus that requries X and V factors for growth • Gram negative bacillus that ferments lactose

31. Neisseria gonorrhoeae undergoes antigenic variation by altering • Antigenic structure of pilus or expression of outer membrane protein II • Antigenic structure of OMP II or expression of OMP I • Expression of polysaccharide capsule • Antigenic structure of pilus and expression of OMP I • Expression of cytochrome c (Oxidase)

32. Lesion A 32 yo homosexual man presents with a painless lesion on the penis of one week’s duration. It developed 3 weeks after unprotected sex with an anonymous partner. The cause of the infection is identified from a specimen obtained from the lesion which shows. • Gram negative coccobacilli • Gram positive cocci in clusters • Gram negative diplococci • Gram negative bacilli • Motile corkscrew-shaped organisms on darkfield microscopy

33. Response to Treatment A 20 yo asymptomatic woman in the 6th week of pregnancy has a positive RPR of 1:16. FTA Abs is positive. She is treated with 3 doses of benzathine penicillin. Follow up testing after treatment should demonstrate • Progressive rise in RPR and reversion of FTA Abs to negative • No fall in RPR and reversion of FTA to negative • Progressive fall in RPR and reversion of FTA to negative • Progressive fall in RPR while FTA remains positive • No change in RPR while FTA remains positive

34. Discharge A 33 yo sexually active woman complains of vaginal discharge. Examination of the greenish frothy discharge discloses pH of 5.5 with numerous WBC’s and organisms with a jerking motion on saline wet mount. Treatment is best accomplished with • Doxycycline for 5 days • Metronidazole – single dose • Ciprofloxacin – single dose • Ceftriaxone intramuscular – one dose • Benzathine penicillin G IM – one dose

35. Fever and Abdominal Pain An 18 yo woman presents with fever and lower abdominal pain. She has recently had intercourse with a new partner. Pelvic examination discloses vaginal discharge, pain on motion of the cervix and bilateral adnexal fullness. Causes of these symptoms include? • Neisseria gonorrhoeae • Treponema pallidum • Chlamydia trachomatis • E. coli, Prevotella bivia, enterococcus • Herpes simplex

36. Vaginitis A 35 year old woman complains of scant vaginal discharge and itching. Exam discloses erythema of the vaginal mucosa with patches of white discharge. The pH is 4.3. What is appropriate treatment for this condition? • Metronidazole for 5 days • Ciprofloxacin – one dose • Doxycycline for 5 days • Topical acetic acid • Topical miconazole

37. Zoonoses

38. Plague – Yersinia pestis • Highly virulent, encapsulated, small gram negative rod • Endemic in wild rodents Europe and Western N. America • Transmitted by flea • Virulence: endotoxin, exotoxin, proteins • Spreads to nodes – Buboes, severe sepsis • Pneumonic plague – droplet spread • Diagnosis – aspirate bubo, blood (careful in lab) • Treatment – Gentamicin, Streptomycin, tetracycline

39. Pastuerella multocida • Short, gram-negative rod • Cellulitis or osteomyelitis following cat bite or dog bite • Treatment penicillin

40. Anthrax – Bacillus anthracis • Gram positive, spore-forming rod with capsule “Box cars”. Spores in soil, on animal productrs • Enter through skin, alimentary, respiratory tracts • Toxin: Protective antigen, edema factor (cyclase), lethal factor • Painless ulcer with marked local edema • Pneumonia (mediastinitis) meningitis • Necrotizing enteritismeningitis • Diagnosis-culture • Treatment: ciprofloxacin+clindamycin+rifampin, penicillin if susceptible

41. Gram Stain - CSF

42. Tularemia • Francisella tularensis – small gram negative rod, enzootic in wild animals (rabbit) • Transmission – ticks or contact with dead animal • Clinical • Ulceroglandular – ulcer with swollen regional lymph nodes • Typhoidal – fever, adenopathy • Pulmonary • Diagnosis – Culture dangerous in lab; serology and direct fluorescence • Treatment – Gentamicin or tobramycin

43. Brucellosis • Small, slow growing gram negative rod • B. melitensis (goats, sheep), B. abortus (cattle), B. suis (swine) • Transmission – Occupation, milk • Small granulomas in lymph nodes, spleen, marrow • Fever, weakness, fatigue • Diagnosis – cluture blood and tissue, serology • Treatment – tetracycline, gentamicin

44. Rocky Mountain Spotted Fever • Tick borne rash illness caused by Rickettsia rickettsii, a small gram negative rod. Obligate intracellular parasite. Eastern and Midwestern US • Vasculitis – organism in endothelium • Fever, headache, weakness followed by rash, DiC and shock • Diagnosis: Clinical, serology, ElISA, Weil Felix (Culture dangerous) • Treatment – Doxycycline

45. Q Fever • Coxiella burnetti • Transmission – contact with infectious aerosol from cattle, sheep, goats. Parturient cats • Fever, headache, cough; frequent hepatitis, endocarditis • Diagnosis – serology • Treatment – Doxycycline

46. Lyme Disease • Borrelia burgdorferi – spirochete transmitted by Ixodes ticks • Reservoir – field mice and deer • Erythema migrans, meningitis, encephalitis • Heart disease, arthritis • Diagnosis – Serology ELISA and Western blot • Treatment – Doxycycline, amoxicillin, ceftriaxone

47. Fungi

48. Histoplasmosis • Dimorphic fungus – mold in soil, yeast in tissue • Ohio and Mississippi river valleys, disturbed soil with bird droppings, bat caves • Small oval yeast in macrophages • Clinical • Pulmonary – acute pneumonia, chronic like tuberculosis • Disseminated in immunocompromised – esp AIDS • Diagnosis – Culture, Serology, Antigen in urine • Treatment – Self limited, Itraconazole, Amphotericin b

50. Blastomycosis • Dimorphic fungus – large refractile yeast with broad based budding • Ohio, Mississippi, St. Lawrence river valleys, Great Lakes. Soil with decaying organic material • Clinical • Pulmonary, pneumonia (refractory) • Dissemination to skin common • Diagnosis – culture, histology • Treatment – Itraconazole, Amphotericin b