Unit 3 exam - micro bio

antibiotic resistance

antibiotics are selective agents, because they kill susceptible bacteria, they select for resistant mutants, it’s a threat worldwide.

Overuse of antibiotics

high rates of resistance are attributed to overuse.

• human medicine

• agriculture: use of subtherapeutic antibiotics in animals

emerging antibiotic resistant bacterial pathogens

• MRSA, VMRSA

• carbapenem - resistant klebsiella pneumonia

• multi drug resistant uropathogenic e.coli (UPEC)

• NDM1 - positive bacteria

K. pneumoniae

an encapsulated gram negative bacterium

• lives in gut on humans and animals ( not causing problems )

• opportunistic pathogen

if gains access to extra intestinal sites (bloodstream, lungs) infections can become deadly

Nosocomial pathogen

hospital acquired pathogen

carbapenems

antibiotics that break down bacterial cell walls

transposons

genes for antibiotic resistance acquired via the transposons delivered by bacteriophages

NDM1

new type of drug resistance

• new delhi metallo beta lactamase

• some NDM1 positive bacteria are resistant to most/all antibiotics

• major problem in gram negative pathogens

• major genetic element encoding multiple drug resistance genes, contained within transposons on a plasmid

carbapenem resistant

carbapenem resistant NDM1 positive klebsiella is also resistant to most disinfectants

• emerging nosocomial pathogen

• very contagious - transmitted patient to patient, medical worker to patient, from fomites, indwelling devices.

UPEC leading cause of urinary tract infections

• cystitis

• pyelonephritis

• renal damage

• potential systemic infections

8-65% of UPEC strains are resistant to drugs commonly used to treat these infections

selectively toxic

should kill/ inhibits microbes without damaging host

“perfect” antimicrobial drug

• selectively toxic

• microbial (kills microbes) rather than microbistatic (stops from replicating)

• remains potential long enough to be effective

• doesn’t lead to antimicrobial resistance

• easily delivered to site of infections

• reasonably priced

antimicrobial drug origin

• mostly made by bacteria and fungi

• common bacterial producers

• common fungal producers

natural antibiotics

directly isolated from microbial source

semisynthetic drug

chemically modified after being isolated from natural source

synthetic drug

produced entirely by chemical reactions

narrow spectrum

• used to target specific group of microb

• ex only targets gram positives or only some gm+

medium spectrum

• effective against some gram positives and gram negatives but not all types

broad spectrum

effective against most gram positive and gram-negative bacteria

minimum inhibitory concentration assay

incubate bacterium in presence of increasing concentrations of drug, measuring the lowest concentration of the drug resistance to inhibit bacterial growth

antibacterial drug that targets the bacterial cell wall

• beta lactam

• glycopeptide

• polypeptide

antibacterial drug that targets protein synthesis

• aminoglycosides

• ampheniols

• tetracyclines

antibacterial drug that targets cell membrane

polymixins

antibacterial drug that targets bacterial nucleic acids systhesis

quinolones

antibacterial drug that targets folic acid sythesis

sulfonamides

beta lactam antibiotics

• penicillins

• cephalosporins

• (carbapenems)

glycopeptide antibiotics

vancomycin

polypeptide antibiotics

bacitracin

bacterial target

bacterial transpeptidases located in cell wall. These enzymes help build and repair peptidoglycan in the bacterial cell walls

• trans peptides are easier to access in gram positives than gram negatives

original source penicillin

mold penicillium chysogeum

natural penicillin

narrow spectrum, effective against gram positives

semisynthetic penicillins

medium spectrum, also effective against some gram negative bacteria

resistant bacteria produce

beta lactamases

• enzymes that break apart b lactam ring

drug development

penicillins that are resistant to some bacterial b lactamases

clavamox

amoxicillin with additional clavulanic acid

• clavulanic acids inhibit activity b lactamase enzymes

• medium spectrum

oxacillin and methicillin

inhibit some staphylococcal b lactamases

useful for treating s, aureus, but not for MRSA

narrow spectrum: mostly gram positives