Gram Positive Rods Flashcards
- Describe the key identifying characteristics of Bacillus anthracis
Spore forming Gram positive rod
Widespread in nature
Prefers aerobic conditions
Culture; skin, blood, sputum, CSF
Gram + box car shaped bacilli
Biochemical tests
Motility - negative (all other bacilli are motile)
Non-Hemolytic (all other bacilli are hemolytic)
PCN susceptibile
- Describe the key identifying characteristics of Listeria monocytogenes
Culture blood, CSF, fluids
grows in 1-2 days
Beta hemolytic similar to Group B Strep
Gram Stain:
regular Gram-Positive rods (Non-spore forming)
Biochemical tests Catalase + Tumbling motility Motile at RT Non-Motile at 37 C Demonstrates “Umbrella” Motility
- Describe the key identifying characteristics of Erysipelothrix rhusiopathiae
- Pleomorphic Gram positive rods that form long filaments (“hairlike”)
- Microaerophilic or facultative anaerobe
- Slow growth, requires 2-3 days incubation
- Small, grayish, α-hemolytic colonies
- Catalase neg, non-motile, weakly fermentative, produces H2S on triple sugar iron agar (TSI)*
- Describe the key identifying characteristics of Corynebacterium diphtheriae
Pleomorphic Gram positive rods Clumps of organisms resembling Chinese “letters” (Y,V,X shapes) Grows aerobic or facultatively anaerobic Small white nonhemolytic colonies Commonly called “diphtheroids”
- Describe the key identifying characteristics of Arcanobacterium hemolyticum
Non-spore forming Gram-positive rod producing irregular, club-shaped, curved or “V” formation
Catalase-negative
Beta hemolytic* - colonies appear similar to β-hemolytic Group A Strep on blood agar
Isolated mostly from young adults* (15-25 Y.O.) symptomatic pharyngitis, fever, occ. cutaneous rash, some with pseudomembranes pharynx/tonsils, and submandibular lymphadenopathy
Also isolated from wounds, abscesses and blood of patients with septicemia and endocarditis
- Describe the key identifying characteristics of Nocardia species
Gram-positive, partially acid-fast rods; cell wall with mycolic acid
Strict aerobe, will grow on most nonselective agars, prolonged incubation (7 days or more may be required)
beaded appearence
- Describe the epidemiology of infections caused by: Bacillus anthracis
Inoculation (95%) - Contaminated soil or infected animal products Ingestion Inhalation - Wool Sorters disease - Processing goat hair - Biological weapons
- Describe the epidemiology of infections caused by: Listeria monocytogenes
Found in soil, stream water, sewage
Part of the fecal flora of many animals
Plants, meats and dairy are contaminated with the water or animal feces
Undercooked and unpasteurized foods
Asymptomatic human fecal carriage (small%)
Soft cheeses, veggies, and cold cuts at the deli counter become contaminated
“Ready to eat” foods, smoked seafood
- Describe the epidemiology of infections caused by: Erysipelothrix rhusiopathiae
Ubiquitous in soil and groundwater, distributed worldwide
Animal disease widely recognized but human disease is uncommon
Recovered from tonsils and digestive tract of mammals, birds and fish.
Colonization high in swine and turkeys
* Human infection acquired from animals, primarily occupational: butchers, meat processors, farmers, poultry workers, fish handlers and veterinarians
- Describe the epidemiology of infections caused by: Corynebacterium diphtheriae
Ubiquitous in plants and animals Colonize humans Skin Upper respiratory tract Gastrointestinal tract Urogenital tract
infection transmitted by respiratory droplets or direct contact with cutaneous infection
Etiologic agent of diphtheria
Rare disease in U.S. due to immunization
Ab produced against toxin in natural infection
Vaccinate with toxoid = formalin treated toxin
Re-vaccinated every 10 years
- Describe the epidemiology of infections caused by: Arcanobacterium hemolyticum
Isolated mostly from young adults (15-25 Y.O.) symptomatic pharyngitis, fever, occ. cutaneous rash, some with pseudomembranes pharynx/tonsils, and submandibular lymphadenopathy
Also isolated from wounds, abscesses and blood of patients with septicemia and endocarditis
- Describe the epidemiology of infections caused by: Nocardia species.
Worldwide distribution in soil
Exogenous infections acquired by inhalation (pulmonary) or traumatic introduction (cutaneous)
Disease most common in immunocompetent pts. with chronic pulmonary disease or immunocompromised pts. with T-cell deficiencies
- Describe the clinical presentation of infections caused by: Bacillus anthracis
Cutaneous Painless papule Ulcer surrounded by vesicles Necrotic eschar (center) Anthrax = Greek word for “coal” 20% mortality
Upper GI Ulcers in mouth and esophagus Lower GI Terminal ileum most common N/V, malaise, bloody diarrhea Mortality 100%
Inhalation
Prolonged latent period (2 months or more)
Initial symptoms – nonspecific
Fever, SOB, cough, HA, vomiting, chills, chest and abdominal pain
Second stage
Rapidly worsening fever, edema and enlargement of mediastinal lymph modes (responsible for the widened mediastinum observed on chest Xray)
Pulmonary disease rare, meningeal symptoms occur in 50% of patients
Shock & death occurs within 3 days unless treatment is initiated immediately
- Describe the clinical presentation of infections caused by: Listeria monocytogenes
Neonates
Early-onset disease: acquired transplacentally in utero, characterized by disseminated abscesses and granulomas in multiple organs
Late-onset disease: acquired at or shortly after birth presents as meningitis with septicemia
Elderly
typically influenza-like illness with or without gastroenteritis
Pregnant women or patients with cell-mediated immune defects
primary bacteremia or disseminated disease with hypotension and meningitis
- Describe the clinical presentation of infections caused by: Erysipelothrix rhusiopathiae,
• Cutaneous infections typically develop after the organism is inoculated subcutaneously
Two forms of human infection
- Erysipeloid: localized skin infection, on fingers or hands and appears violaceous with a raised edge. Slowly spreads peripherally as discoloration fades. Suppuration is uncommon (separates from streptococcal erysipelas)
- Septicemic form: uncommon, when present frequently associated with endocarditis
•Treatment – Penicillin is antibiotic of choice
