Gram Positive Rods

Question 1

Gram positive bacilli

Answer 1

-Clostridium spp: Tetanus botuluism, gas gangrene -Corynebacterium: Diptheria and skin flora Nocardia -Bacillus sp: usually contaminant but anthrax “Bacillus” describes both the genus and the shape

Question 2

Anaerobic gram positive bacilli

Answer 2

Bacillus and Clostridium

Question 3

Spore that looks like a tennis racket (terminal spore)

Answer 3

Clostridium tetani

Question 4

Spore in the center of the bug

Answer 4

Bacillus

Question 5

Different Clostridium species

Answer 5

-Perfringens -Difficile -Tetani -Botulinum

Question 6

Clostridium Perfringens common name and disease

Answer 6

-Gas gangrene -Vomiting -Gangrene, food poisoning

Question 7

Clostridium Difficile common name and disease

Answer 7

-C. Diff, antibiotic associated diarrhea -diarrhea can be fatal (colon pops)

Question 8

Clostridium Tetani common name and disease

Answer 8

-Tetanus -muscle spasms also lead to asphyxiation, also autonomic instability

Question 9

Clostridium Botulinum common name and disease

Answer 9

-Botulism -muscle paralysis, long term binding of toxin to nerve endings - may need months on ventilator to survive

Question 10

C. Diff pathogenesis

Answer 10

-Look for toxin (TcdA, TcdB) - disrupt G-proteins and tight junctions -Leads to fluid leakage

Question 11

C. Diff Diagnostics

Answer 11

Question 12

C. Botulinum basics

Answer 12

• Large gram+ rod
• Anaerobic spore former
• Soil & Water
• Needs pH >7 for growth
• Highly potent toxin

Question 13

C. Botulinum infection and incubation

Answer 13

• Incubation: 12-36 hrs 
• Adults (PRE-formed toxin) Diplopia (double vision) 
• Any muscle weakness droopy eyelids 
• Swallowing difficulty 
• Breathing difficulty 
• Babies (spore ingestion) Colonic flora not developed 
• Floppy baby syndrome 
• Wound infection 
• Diagnosis: Clinical Food sent for toxin ID 
• Anaerobic culture 
• Treatment: supportive and trivalent antitoxin (A, B, E) but high rates of hypersensitivity

Question 14

C. Perfringens

Answer 14

Gram positive rod with “boxcar” gram stain 

“A” strain – food disease 

Toxins

α-toxin: lethicinase 

Φ-toxin: hemolysin 

Other Diseases:

Clostridial Myonecrosis aka “gas gangrene” 

Enteritis necroticans 

Question 15

C. Tetani

Answer 15

Anaerobic conditions spores germinate 

Toxin: Tetananospasm: 

Heavy(100kd) Cell surface receptors binding neuronal cells. 

Light 50kd: affects inhibitory systems of motor firing 

Week 1 die of unopposed muscle spasms  (opsithotonus)

Autonomic dysfunction 2nd week as toxin affect brainstem 

Works almost opposite to mechanism of botulinum

Question 16

Anaerobic non-spore formers

Answer 16

• Propionibacteria
• Actinomycetes

Question 17

Propionibacteria

Answer 17

Small on gram stain 

Skin flora 

Smelly feet 

Acne 

Biofilm on lines and metal 

Question 18

Actinomycosis

Answer 18

• Gram-positive, Branched  
• Anaerobic (microaerophilic or facultative) 
• Filamentous branching rods/bacilli 
• Can be part of normal flora (mouth, GI, vagina) 
• Usually found as part of “polymicrobial” infection >>> Not usually found in isolation 
• Ex: Tooth flora, Pelvic inflammatory disease

Question 19

Actinomycosis clinical manifestations

Answer 19

-Draining sinus tracts!!! 

-Cervicofacial (most common)

*Dental work/trauma 

*“lumpy jaw” 

-Thoracic

*Aspiration of mouth secretions 

*Extension of “lumpy jaw” 

-Abdominal

*Penetrating trauma 

*Intestinal perforation 

Question 20

Actinomycosis diagnosis

Answer 20

Gram stain: beaded/branching GPR 

AFB stain: negative

Unlike Nocardia: partially + AFB 

“sulfur granules” 

Question 21

Aerobic spore formers

Answer 21

Bacillus Anthracis

Bacillus Cereus

Question 22

Bacillus Cereus

Answer 22

most likely contamination if pre-formed toxin is ingested: food poisoning (refried rice in chinese take-out)

Question 23

Bacillus Anthracis

Answer 23

• wool sorters disease or pneumonia
• malignant pustule if it is cutaneous

Question 24

aerobic non-spore formers

Answer 24

• Listeria
• Corynebacteria
• Nocardium

Question 25

Listeria

Answer 25

- contaminated food (soft cheese) - Listeria uses human actin tail to invade from cell to cell - Can moves intracellularly - When host defense is compromised, bloodstream infection can occur - important in pregnant women (harms mom since immunocompromised)

Question 26

Corynebacteria

Answer 26

- Many species that commensals on skin: only pathogenic if get onto prosthetic material ( heart valves) - Corynebacterium diphtheria  - Prevented by vaccination.  - Spread: contact and droplet.  - Endemic in India 

Question 27

Corynebacteria diptheria diease and diagnosis

Answer 27

**Disease:** - sore throat -\> airway obstruction,  - exotoxin =\> carditis &/or neuropathy  **Diagnosis:** - Culture: black colonies on cystine-tellurite agar  - Loeffler’s selective media is helpful  - Elek’s test for toxin 

Question 28

Nocardia

Answer 28

- Environmental saphrophytes: Soil, organic matter, water  - Some species are pathogenic *N. brasieliensis * - Direct inoculum onto skin  - Some species are opportunistic *N. asteroides*  - Inhaled, then into lungs and/or brain

Question 29

Nocardia clinical manifestations

Answer 29

Depends on host immunity -Immunocompetent \*Soil contaimination of skin injury \*Cutaneous disease -Immunocompromised \*Lung disease, spread to brain