Antibiotics: An Overview

Pre-Test

Which statements are true about E.coli?a) It is a Gram positive bacteria.

b) It is a Gram negative bacteria.

c) It is a bacteria normally found in the colon.

d) It is the most common cause of a UTI.

e) It can cause diarrhea.

Pre-Test

The 6 year old boy has high volume watery diarrhea that looks like ‘rice in water’. He is dehydrated. You resuscitate him with IV normal saline. What is the best antibiotic treatment?a) Penicillin G or Penicillin V

b) Ampicillin or Amoxicillin

c) Doxycycline or Erythromycin

d) Cefalexin or Cefazolin

Pre-Test

A 3-year old child is brought to the emergency. The child is irritable and complains of a headache. On exam, the child has a fever of 39ºC and has neck stiffness. You are worried about meningitis. What antibiotic should you consider?a) Metronidazole

b) Ciprofloxicillin

c) Cefazolin

d) Cloxicillin

e) Ceftriaxone

Pre-Test

What statements are true about rickettesia?a) Typhus fever is caused by rickettesia.

b) Rickettesia is an atypical bacteria.

c) Rickettesia can be treated with doxycycline.

d) Rickettesia can be treated with tetracycline.

e) Rickettesia can be treated with chloramphenicol.

Pre-Test

A 20-year old male comes in with 2 week history of general malaise and recurrent fever. He recently developed a papular rash on his chest. His abdomen is tender and distended. The patient should be treated with:a) Ampicillin for a probable UTI.

b) Levofloxacin for a probable lobar pneumonia.

c) Cloxicillin for a probable Staphylococcus rash.

d) Ceftriaxone for probable Salmonella typhi.

e) No antibiotics.

Types of Microorganisms that cause Infectious Disease

Bacteria

Protozoa

Fungi

Helminths

Viruses

Types of Microorganisms that cause Infectious Disease Bacteria

Single cell organism with cell wall No nucleus / Has circular DNA within cell

Protozoa (ie. Plasmodium, Entamoeba, Giardia) Single cell organism with nucleus

Fungi: Yeast (ie. Candida albicans)

Helminths: Worms

Viruses Not a cell, but are DNA or RNA wrapped in protein coat They reproduce by taking over an animal cell and

reproducing

Types of Microorganisms that cause Infectious Disease Antibiotics treat bacteria and protozoans

Type of Bacteria

TYPICAL Bacteria Gram positive Gram negative

ATYPICAL Bacteria Acid fast No cell wall Intracellular (lives inside host cells)

Gram Stains Divides bacteria into 2 groups

Gram positive Gram negative

Based on cell wall differences

Detects peptidogylcan which is a part of the cell wall Gram positive = THICK peptidoglycan layer Gram negative = Thin petidoglycan layer

Detects shape of bacteria Cocci - circle Bacillus - rod (straight or curved) Spirochete - spiral

What color are the gram positive bacteria on gram stain?

Can you give some examples of Gram + and Gram –

BACTERIA?

Gram positive Gram negative

Can you give some examples of Gram + and Gram –

BACTERIA?

Gram positive

Staphylococcus

Streptococcus

Enterococcus

Clostridium

Gram negative

E. coli

Klebsiella

Hemophilus

Pseudomonas

Niesseria

Classification of Bacteria

Typical Bacteria Atypical Bacteria

Gram + Gram -

Cocci Rod

StaphylococcusStreptococcusEnterococcus

Clostridium (anaerobic)

Cocci Rod

Niesseria

Straight Curved

E.coliSalmonella /ShigellaProteus / EnterobacterKlebsiellaHemophilusBordetellaPseudomonasBacteroides (anaerobic)

VibrioCampylobacterHelicobacter

Spiral

Treponema

Acid fast No cell wall

Intracellular

RickettsiaChlamydia

Mycoplasma

Mycobacterium

Protozoans

Examples: Plasmodium: malaria Entamoeba histolytica: dysentery and liver abscesses Giardia intestinalis: diarrhea Trichimonal vaginalis: STI

Types of Antibiotics

Beta-Lactams

Sulpha drugs

Fluroquinolones

Aminoglycocides

Tetracyclines

Macrolides

Beta-Lactam Antibiotics

Detects peptidogylcan which is a part of the cell wall Gram positive = thick peptidoglycan layer Gram negative = thin petidoglycan layer

Inhibit the synthesis of peptidoglycan cell wall of bacteria The peptidoglycan layer is important in cell wall structure,

especially in Gram positive bacteria

Can you give some examples of beta-lactam antibiotics?

Beta-Lactam Antibiotics

Types of beta-lactam antibiotics Penicillins Cepalosporins

Penicillins

There are different kinds of penicillins

Each kind has slightly different bacterial coverage

Can you give me some names of penicillins that you have heard of?

Penicillins

Natural penicillins Penicillin G (IM or IV) Penicillin V (PO)

What bacteria do the natural penicillins cover?

Penicillins

Natural penicillins Penicillin G (IM or IV) Penicillin V (PO)

What bacteria does it cover? Some Gram +

Streptococci Enterococci

Few Gram - Neisseria

Penicillins

Aminopenicillins Ampicillin Amoxicillin

What bacteria does it cover?

Penicillins

Aminopenicillins Ampicillin Amoxicillin

What bacteria does it cover? Some Gram +

Streptococcus Enterococci

More Gram – than natural penicillins E. Coli, Salmonella, Shigella, Hemophilus

Penicillins

Anti-staphylococcal penicillins Cloxacillin Methicillin

What bacteria does it cover?

Penicillins

Anti-staphylococcal penicillins Cloxacillin Methicillin

What bacteria does it cover? More Gram +

Staphylococcus Streptococcus No enterococcus

No Gram - coverage

Penicillins

Extended Spectrum Piperacillin

What bacteria does it cover?

Penicillins

Extended Spectrum Piperacillin

What bacteria does it cover? Some Gram +

Streptococcus Enterococcus Staphylococcus if tazobactam added

Most Gram – E. coli, Klebsiella, Proteus, Pseudomonas Anaerobic bacteria

Cephalosporins

Divided into 4 generations

As generation increases Decreasing Gram + activity Increasing Gram – activity

3rd generation cephalosporins can penetrate the CNS (so use these for meningitis)

What cephalosporin antibiotics do you know?

Cephalosporins: Examples

1st generation Cefalexin, Cephalothin, Cefazolin, Cefadroxil

2nd generation Cefuroxime, Cefaclor, Cefprozil, Cefoxitin

3rd generation Ceftriaxone, Ceftazidime, Cefotaxime, Cefixime

1st gen.

2nd gen

3rd gen

Gram + Staph Y Y

Strep Y Y Y

Gram - Proteus Y Y Y

E. coli Y Y Y

Klebsiella Y Y Y

Hemophilus Y Y

Enterobacter Y Y

Neisseria Y Y

Pseudomonas (Y)

Cephalosporin coverage

Trimethoprim-Sulfamethoxazole

What bacteria does it cover?

Trimethoprim-Sulfamethoxazole

Gram positive Staphylococcus Weak Streptococcus coverage

Gram negatives E. coli, Klebsiella, Proteus Salmonella, Shigella Hemophilus

Side effects: Rash, allergy, Bone marrow suppression

Fluoroquinolones

2 types Ciprofloxacin

Good Gram - Good atypical coverage: Mycoplasma, Chlamydia No Gram +

Respiratory Fluoroquinolones (levofloxacin, moxifloxacin) Good Gram – Better Gram +, especially Streptococcus Moxifloxacin also good for anaerobes Good antibiotic choice for respiratory infections

Aminoglycosides

Gentamicin, Tobramycin

Activity Good Gram – No Gram + or Anaerobic coverage

Side effects Hearing loss (permanent) Renal failure (reversible)

Tetracyclines

Tetracycline, Doxycycline

Activity Better Gram + than Gram – Good for atypical bacteria: Rickettsia, Chlamydia Good for protozoans: Plasmodium, Entamoeba

In children (<8 years old) can cause permanent teeth staining

Macrolides

Erythromycin, Clarithromycin, Azithromycin

Activity Some Gram +: Streptococci Some Gram -: Hemophilus, Neisseria, Campylobacter Atypicals: Mycoplasma, Chlamydia, Rickettsia

Mostly for respiratory and soft tissue infections

Antibiotics against anaerobes

Clindamycin Good Gram positive coverage:

Staphylococcus Streptococcus

Good Gram negative anaerobic coverage: Bacteroides

Poor Gram negative aerobic coverage Used for:

Skin and soft tissue infections Pelvic and Intraabdominal infections (in combination

with other antibiotics that cover Gram negative bacteria)

Antibiotics against anaerobes

Metronidazole Good anaerobic coverage

Bacteroides, Clostridium Good protozoal coverage

Entamoeba, Giardiasis Use: Intraabdominal and pelvic infections (in combination

with other antibiotics to cover anaerobic Gram -) Good for Clostridium difficile (diarrheal infection especially

in patients who have received antibiotics for another reason)

Chloramphenicol

Activity Gram +: Staphylococci, Streptococci, Clostridium Gram -: Hemophilus, Neisseria, E. coli, Vibrio, Salmomella

Side effects Bone marrow toxicity; Pancytopenia

Common uses Typhoid fever Scrub typhus / Rickettsia Meningitis

Summary

Antibiotics should be chosen based on what the

most likely bacteria are causing the disease and

what antibiotics will target those bacteria

Case 1

Diagnosis?

Common Bacteria?

Case 1

Diagnosis?

Common Bacteria? Streptococci Staphylococci

Treatment?

Case 1

Diagnosis?

Common Bacteria? Streptococci Staphylococci

Treatment? Penicillins

Amoxicillin Cloxacillin

1st gen cephalosporin

Case 2: Meningitis

What are common bacteria?

Case 2: Meningitis

What are common bacteria? Streptococcus pneumoniae Neisseria meningitidis Hemophilus influenzae Listeria monocytogenes

Treatment?

Case 2: Meningitis

What are common bacteria? Streptococcus pneumoniae Neisseria meningitidis Hemophilus influenzae Listeria monocytogenes

Treatment? High dose Ceftriaxone (2g IV q12 h) Add Ampicillin if age > 50 for Listeria

Case 2: Quality Assurance

A 20year old male presents with fever, chills, severe headache, and neck stiffness

He traveled 6 hours to get to the hospital

When he arrives, he is drowsy and BP is 100/60. He waits in the emergency room for another 2 hours

A medical student sees him first, but is not sure what to do, so waits to discuss with the teacher who arrives 1 hour later

In the meantime, the patient becomes hypotensive, has a seizure, and loses consciousness

Case 2: Quality Assurance

Why did the patient deteriorate so quickly?

Case 2: Quality Assurance

Why did the patient deteriorate so quickly? Delaying antibiotics in meningitis increases risk of death

and irreversible neurologic deficits

Case 2: Quality Assurance

What could have been done differently to improve patient care? By the student? By the teacher? By the hospital/ health care system?

Case 3

Probable Diagnosis?

Case 3

Probable Diagnosis? Lobar Pneumonia

Common bacteria?

Case 3

Common bacteria? Streptococcus pneumoniae Mycoplasma, Chlamydia Hemophilus (if chronic lung disease)

Treatment? Outpatients In patients

Case 3

Common bacteria? Streptococcus pneumoniae Mycoplasma, Chlamydia Hemophilus (if chronic lung disease)

Treatment? Outpatients

Doxycycline Amoxicillin 2nd gen cephalosporin

In patients Ceftriaxone + macrolide Levofloxacin or Moxifloxacin

Case 4: Urinary Tract Infection

What are common bacteria?

Case 4: Urinary Tract Infection

What are common bacteria? E. coli** (Most common) Proteus Klebsiella

Treatment?

Case 4: Urinary Tract Infection

What are common bacteria? E. coli** (Most common) Proteus Klebsiella

Treatment? TMP-SMX Ciprofloxacin Amoxicillin/Clavulanate Ceftriaxone if severe Aminoglycosides if severe

Case 5: Bloody Diarrhea

Common bacteria?

Case 5: Bloody Diarrhea

Common bacteria? Salmonella Shigella, Campylobacter E. coli

These are all Gram negatives

Treatment?

Case 5: Bloody Diarrhea

Salmonella Fluoroquinolone, Ceftriaxone More resistance to TMP-SMX, Macrolides, and Amoxicillin

Shigella Fluoroquinolone, Ceftriaxone More resistance to TMP-SMX, Macrolides, and Amoxicillin

Campylobacter Fluoroquinolone All are resistant to TMP-SMX, Penicillins, and

Cephalosporins

E. coli No antibiotics

Case 6

Diagnosis?

Case 6

Diagnosis?

Bacteria? Scrub typhus Rickettsia family

Treatment?

Case 6

Diagnosis?

Bacteria? Scrub typhus Rickettsia family

Treatment? Doxycycline Chloramphenicol Tetracycline

Case 7

Patient presents with: Fever, Relative bradycardia Develops abdominal pain and rash

Diagnosis?

Case 7

Patient presents with: Fever, Relative bradycardia Develops abdominal pain and rash

Diagnosis?

Bacteria? Salmonella typhi (Gram negative)

Treatment?

Case 7

Patient presents with: Fever, Relative bradycardia Develops abdominal pain and rash

Diagnosis?

Bacteria? Salmonella typhi (Gram negative)

Treatment? Ciprofloxacin Ceftriaxone

Post Test

Which statements are true about E.coli?a) It is a Gram positive bacteria.

b) It is a Gram negative bacteria.

c) It is a bacteria normally found in the colon.

d) It is the most common cause of a UTI.

e) It can cause diarrhea.

Post Test

A 6 year old boy has high volume watery diarrhea that looks like ‘rice in water’. He is dehydrated. You resuscitate him with IV normal saline. What is the best antibiotic treatment?a) Penicillin G or Penicillin V

b) Ampicillin or Amoxicillin

c) Doxycycline or Erythromycin

d) Cefalexin or Cefazolin

Post Test

A 3-year old child is brought to the emergency. The child is irritable and complains of a headache. On exam, the child has a fever of 39ºC and has neck stiffness. You are worried about meningitis. What antibiotic should you consider?a) Metronidazole

b) Ciprofloxicillin

c) Cefazolin

d) Cloxicillin

e) Ceftriaxone

Post Test

What statements are true about rickettesia?a) Typhus fever is caused by rickettesia.

b) Rickettesia is an atypical bacteria.

c) Rickettesia can be treated with doxycycline.

d) Rickettesia can be treated with tetracycline.

e) Rickettesia can be treated with chloramphenicol.

Post Test

A 20-year old male comes in with 2 week history of general malaise and recurrent fever. He recently developed a papular rash on his chest. His abdomen is tender and distended. The patient should be treated with:a) Ampicillin for a probable UTI.

b) Levofloxacin for a probable lobar pneumonia.

c) Cloxicillin for a probable Staphylococcus rash.

d) Ceftriaxone for probable Salmonella typhi.

e) No antibiotics.

Questions