Gram Positive Rods

Question 1

• Describe the key identifying characteristics of Bacillus anthracis

Answer 1

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

Question 2

• Describe the key identifying characteristics of Listeria monocytogenes

Answer 2

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

Question 3

• Describe the key identifying characteristics of Erysipelothrix rhusiopathiae

Answer 3

• 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)*

Question 4

• Describe the key identifying characteristics of Corynebacterium diphtheriae

Answer 4

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”

Question 5

• Describe the key identifying characteristics of Arcanobacterium hemolyticum

Answer 5

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

Question 6

• Describe the key identifying characteristics of Nocardia species

Answer 6

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

Question 7

• Describe the epidemiology of infections caused by: Bacillus anthracis

Answer 7

Inoculation (95%)
 - Contaminated soil or infected animal products
Ingestion
Inhalation
 - Wool  Sorters disease
 - Processing goat hair
 - Biological weapons

Question 8

• Describe the epidemiology of infections caused by: Listeria monocytogenes

Answer 8

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

Question 9

• Describe the epidemiology of infections caused by: Erysipelothrix rhusiopathiae

Answer 9

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

Question 10

• Describe the epidemiology of infections caused by: Corynebacterium diphtheriae

Answer 10

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

Question 11

• Describe the epidemiology of infections caused by: Arcanobacterium hemolyticum

Answer 11

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

Question 12

• Describe the epidemiology of infections caused by: Nocardia species.

Answer 12

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

Question 13

• Describe the clinical presentation of infections caused by: Bacillus anthracis

Answer 13

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

Question 14

• Describe the clinical presentation of infections caused by: Listeria monocytogenes

Answer 14

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

Question 15

• Describe the clinical presentation of infections caused by: Erysipelothrix rhusiopathiae,

Answer 15

• Cutaneous infections typically develop after the organism is inoculated subcutaneously

Two forms of human infection

1. 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)
2. Septicemic form: uncommon, when present frequently associated with endocarditis

•Treatment – Penicillin is antibiotic of choice

Question 16

• Describe the clinical presentation of infections caused by: Corynebacterium diphtheriae

Answer 16

• Pharyngitis with patchy exudates on tonsils, uvula, soft palate
• Tough gray pseudomembrane consists of fibrin, white cells, bacteria, debris&raquo_space; respiratory obstruction and suffocation
• Toxin circulates to heart&raquo_space; injury
• Toxin circulates to CNS&raquo_space; reversible paralysis

Question 17

• Describe the clinical presentation of infections caused by: Arcanobacterium hemolyticum

Answer 17

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

Question 18

• Describe the clinical presentation of infections caused by: Nocardia species.

Answer 18

Bronchopulmonary disease
Primary or secondary cutaneous infections
Secondary CNS infections (e.g., brain abscesses)
Infections are treated with antibiotic therapy (usually sulfonamides) and proper wound care

Question 19

*Describe the three forms of disease caused by Bacillus anthracis

Answer 19

cutaneous
GI
Inhalation

Question 20

*Explain why patients with defects in cellular immunity are particularly susceptible to infections with Listeria monocytogenes

Answer 20

The bacteria move from cell to cell without ever being exposed to the outside therefore the bacteria avoid antibody-mediated clearence– humoral immunity is ineffective therefore cellular immunity is necessary to clear the infection

Question 21

*list three patient populations that are at risk for listeriosis.

Answer 21

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

Question 22

*Name two aerobic Gram-positive rods that can cause food poisoning.

Answer 22

Bacillus cereus

Question 23

*List the diseases associated with Nocardia

Answer 23

Pulmonary diseases, 1o or 2o cutaneous infections; 2o CNS infections

Question 24

*List the diseases associated with Rhodococcus

Answer 24

Pulmonary diseases, opportunistic infect. (e.g., wound infect., peritonitis, traumatic endophthalmitis

Question 25

*List the diseases associated Trypheryma

Answer 25

Whipple’s Disease

Question 26

treatment of Anthrax

Answer 26

PCN, ciprofloxacin*, or doxycycline* Prophylaxis for inhalation 60 days * preferred when possible terrorist origin because of manipulated PCN resistance (but all are currently penicillin susceptible)

Question 27

Bacillus cereus Infections

Answer 27

``` Food poisoning Caused by exotoxins Emetic form Diarrheal form Ocular infections Central line infections Contaminated lines must be removed Opportunistic infections ```

Question 28

ActA gene

Answer 28

gene that allows host cells actin is utilized to move bacteria into adjacent cells without exposure to immune system bc it is never outside of the cell, humoral immunity is ineffective

Question 29

Listeria pathogenisis

Answer 29

Bacteria invade epithelial cells, M cells, macrophages by internalin protein Bacteria are engulfed in vacuole Bacteria produce listeriolysin and phospholipases escapes from phagosome Encoded by ActA gene, host cell actin utilized to move bacteria into adjacent cells without exposure to immune system

Question 30

Listeria treatment

Answer 30

Treat with PCN or ampicillin +/- gentamicin Resistant to all cephalosporins High risk people should avoid eating raw or partially cooked foods of animal origin, soft cheeses, and unwashed raw vegetables and fruits (cantalope)

Question 31

how does C. diphtheriae cause disease?

Answer 31

``` Disease caused by potent exotoxin >> inhibits protein synthesis of eukaryotic cells Two subunits of toxin A = shuts off protein synthesis B = binds to cell receptor Toxin gene carried in bacteriophage ```

Question 32

diagnosis of C. diptheriae

Answer 32

``` Diagnosed by clinical evaluation No rapid lab test Must notify lab to look at throat cultures for diphtheria Grow the organism on selective agar Prove presence of toxin ```

Question 33

treatment of C. diptheriae

Answer 33

Treat with antitoxin and penicillin / erythromycin

Question 34

Corynebacterium pathogenic species

Answer 34

Corynebacterium diphtheriae | Corynebacterium jeikeium

Question 35

Corynebacterium jeikeium

Answer 35

Infects immunocompromised patients Isolated from blood cultures, catheter lines, skin Colonies are slow to grow on agar media Organisms are resistant to most antibiotics, except vancomycin

Question 36

Characteristics of Lactobacillus

Answer 36

Non-spore forming Gram positive rod Normal flora of oral cavity, vaginal tract Found in food products (yogurt) Prefers carbon dioxide or anaerobic atmosphere Opportunistic pathogen Sepsis Endocarditis

Question 37

Aerobic Actinomycetes common features

Answer 37

Aerobic gram-positive, catalase-positive rods that can colonize animals and humans and are found commonly in soil and decaying vegetation.

Question 38

A 22 year old medical student presents with symptoms of pharyngitis with a fever, and cutaneous rash. A throat culture reveals small beta hemolytic colonies that are catalase-negative and stain as short Gram-positive rods exhibiting Chinese character morphology. What is the most likely agent of this students pharyngitis?

Answer 38

Arcanobacterium hemolyticum