Bacteriology - Clostridium, Pseudomonas Aeruginosa, Actinomyces

Clostridium?

Gram-positive rods

- Obligate anaerobes - CANNOT survive in oxygen

- Generate energy solely by fermentation

- Spore-forming

Clostridium - important human pathogens?

C. tetani

C. botulinum

C. difficile

C. perfringens

C. tetani?

Mostly found in soil

- It needs to enter under the skin into anaerobic environment - to cause infection

How to get infected with C. tetani?

Ideally: a puncture wound closed off to air

- Rusty nails

- Barb wire

Tetanus?

C. tetani

- Spastic paralysis

- Rigidity

Exactly opposite of botulism: where affected patient experience flaccid paralysis

Clinical symptoms - C. tetani?

Risus sardonicus - lock jaw

- Trismus

Opisthotonos - extension and arching of the back due to heavy spasm

What causes the symptoms in C. tetani?

Not the bacteria itself, but its toxin

"Tetanospasmin"

- Travels retrograde - through axons to the spinal cord

- Cleaves a protein called SNARE

- Inhibits exocytosis of NTs such as GABA and glycine -> from Renshaw cells in the synapse

Aka: it inhibits the inhibitor = activation -> SPASM

Prevention tetani?

Toxoid vaccine

- Toxin molecule that has lost its toxicity but retained its antigenicity

Given together with pertussis and diphtheria - DPT vaccine

Diagnosis tetani?

- Clinical manifestation

(no question when it develops)

Treatment tetani?

Large doses of metronidazole

&

penicillin

How to neutralize the tetani toxins in an infection?

With tetanus immune globulin

(antitoxin)

How long is a tetanus shot good for?

10 years

Should be repeated every 10 years

Clostridium Botulinum?

Causes botulism

- Descending flaccid paralysis

(Opposite of Guillian-Barre - with ascending paralysis)

Transmission C. botulinum?

Improper canning or insufficient heating of canned food

- Allow for survival of spores in anaerobic environment

= While producing toxins

- They are heat stable

Adults usually acquire this condition by ingestion of pre-formed toxins

The toxin of C. botulinum acts how?

Botulinum toxin

- ONLY affects the peripheral nervous system

(NOT CNS - as it cannot cross BBB)

Pathogenesis of C. botulinum?

Very similar to that of c.tetani

However:

- Botulism attack motor neurons that release acetylcholine (excitatory NT)

= When inhibited, there will not be muscle contraction = aka descending flaccid paralysis

Early symptoms C. botulinum?

Diplopia and ptosis of the eyes

As it starts superiorly and descends from there

Transmission of botulism in neonates?

"Floppy baby syndrome"

Lack of bacterial flora in neonates - spores have the perfect environment for production of toxins

(adults would not be affected by ingesting just the spore - there has to be pre-made toxins, as microbiota would eliminate the endospore)

What type of food is C. botulinum spores found in?

Honey

C. botulinum as botox?

Type A can be used for botox

- Cosmetic

- Migraine

- Asthma

Treatment C. botulinum?

Antitoxin

Clostridium difficile?

Nosocomial infections

- Easily transmitted from person to person

Pathogenesis C. difficile?

Hospitalized patients taking a lot of ABs

- Wipe out normal gut flora

- Allow for C. difficile to grow & produce toxins

What is associated with C. difficile?

- Clindamycin treatment

+

- Improper handwash by the health care workers

Toxins of C. difficile?

Exotoxin A

- Inflammation, cell death & watery diarrhea

Exotoxin B

- Disrupt cytoskeleton integrity

- Form pseudomembranes

Diagnosis C. difficile?

- Endoscope

- Look for toxins in feces

Treatment C. difficile?

Metronidazole or oral vancomycin (as it has a weak GI absorption)

Fecal transplantation

Clostridium perfringens?

Often found in soil/dirt

Transmission: Motorcycle accident & military combat

Toxins C.perfringens?

Alpha, beta, epsilon and iota

Clinical syndromes? C.perfringens

Gas gangrene:

- Crepitation on skin palpitation

- Gas is produced as the bacteria consumes carbs

- Alpha toxins

- Double zone of hemolysis on agar plate

Food poisoning:

- Result in late onset of diarrhea

- Iota toxin

Treatment C.perfringens?

Gas gangrene:

- IV penicillin G

(without - death follows after 48h)

Clean the wounds

Food poison: self-limiting, no treatment needed

Pseudomonas aeruginosa?

Gram-negative, rod-shaped bacteria

- Non-fermenting

- Oxidase positive

- Catalase positive

Dangerous for patients with chronic granulomatous infection

Is obligate aerobes

Where does Pseudomonas aeruginosa thrive?

Wet and moist environments

- Hot tubs folliculitis

Culture of Pseudomonas aeruginosa?

- Fruity odor

- Blue-green color

What type of infections does Pseudomonas aeruginosa cause?

Nosocomial infections

- From medical staff to patients

- In sinks/humidifier in hospitals

What type of people does Pseudomonas aeruginosa affect the most?

Immunocompromised patients

- An opportunistic pathogen

(can also infect healthy people)

Clinical features - Pseudomonas aeruginosa?

Pneumonia

- Number one cause of Gr- nosocomial pneumonia

Pulmonary infection in Cystic Fibrosis patients

- Most common cause of respiratory failure in these patients

Osteomyelitis

- IV drug users

- Diabetics

Complications of burn injuries

- Often cause death and respond poorly to ABs

UTIs

- Indwelling catheter infections - nosocomial

Hot tub folliculitis

- Under-chlorinated infections

Otitis externa

- "Swimmers ear"

Toxins by Pseudomonas aeruginosa?

- Exotoxin A

Inhibition of protein synthesis

Treatment Pseudomonas aeruginosa?

1) Piperacillin + tazobactam

- penicillin that is paired w/ ß-lactamase inhibitors

= Together known as Zosyn

2) Fluoroquinolines - mainly the UTIs

- Carbapenems like imipenem

- 3rd and 4th generation of cephalosporins

Mechanisms of Pseudomonas aeruginosa for AB resistance?

1. Intrinsic resistance

- Outer membrane pores and efflux pump

2. Acquired resistance

- Horizontal gene transfer

3. Adaptive resistance

- Biofilm

Actinomyces?

Actinobacteria

- Gram-positive, rod-shaped bacteria

A. israelii

Growth pattern reminds of hyphae of fungi

Obligate anaerobe

Clinical features - A. israelii?

Oral: found in normal flora

- Infection w/ jaw trauma

- Recent dental procedure

- "Cervicofacial actinomyces infection"

- Thick, yellow pus

- Sulfur granules

Thoracic: Aspiration of oral bacterial flora

Abdominal: Perforation of bowel, after disease/surgery

Pelvic:

Pelvic inflammatory disease

- Intrauterine contraceptive devices

Treatment A. israelii?

Penicillin G

+

surgical drainage