Pharmacology 2060A/B Lecture 16: Module 16

• School: Western University
• Department: Pharmacology
• Course: Pharmacology 2060A/B
• Professor: Andrea Di Sebastiano

Document Summary

16. 1$ : bacteria!are!single!celled!organisms!that!can!be!shaped!as!rods,!spheres,!or! spirals, bacteria!occupy!almost!every! habitat!on!earth,!including! humans!!, most!bacteria!are!rendered! harmless!by!our!immune!system! and!some!even!play!beneficial! roles, however,!some!bacteria!are! pathogenic!and!cause!diseases! such!as!cholera,!syphilis!and!tuberculosis, before!the!discovery!of!antibiotics,!bacterial!infection!was!a!major!cause!of! morbidity!and!death. ! !bacterial!pathogenicity: bacteria!have!a!number!of!virulence!factors!that!they!use!to!cause!infection, virulence!factors!include:, fimbriae!and!pilli, flagella, secretion!of!toxins!and!enzymes, invasion! !fimbriae!and!pilli: fimbriae!and!pilli!are!hair!like! structures!that!project!from! the!surface!of!bacterial!cells, they!allow!bacteria!to!attach! to!certain!sites!in!our!body!so! they!are!not!washed!away, for!example,!the!bacteria!e. # coli#are!known!to!cause! bladder!infections, e. #coli#produce!fimbriae!that! attach!to!the!urogenital!tract. ! Flagella: bacteria!typically!live!in!aqueous! environments!and!need!to!move! to!sites!where!they!can!survive, the!flagellum!that!bacteria! possess!allows!them!to! swim ! through!the!watery!environment! of!our!body!to!the!site!where! they!may!survive. !gram!staining!of!bacteria: gram!staining!is!a!technique!that! is!used!to!classify!bacteria!as! either!gram!positive!or!gram! negative, why!is!this!classification! important?! !this! can!be!important!in!the! determination!of!which! antibiotic!we!use: gram!positive!cells!have!a!thick! peptidoglycan!wall!that!stains!purple!during!gram!staining, gram!negative!cells!have!a!thin!peptidoglycan!layer!and!stain!pink!during! gram!staining. ! Signs!of!infection: the!typical!signs!of! infections!include!fever,! overall!malaise,!local! redness,!and!swelling, other!signs!of!infection! include!increased! respiratory!rate!and! tachycardia. Selective!toxicity: the!treatment!of!a!bacterial!infection!is!critically!dependent!on!the!ability!to! produce!selective!toxicity, selective!toxicity!means!the!therapy!is!able!to!destroy!the!bacteria!without! harming!the!host!(i. e. !human!cells), selective!toxicity!is!produced!by!targeting!differences!between!the!cellular! chemistry!of!bacteria!and!humans, antibiotic!therapy!produces!selective!toxicity!by:, disrupting!the!bacterial!cell!wall!(human!cells!do!not!have!a!cell!wall), targeting!enzymes!that!are!unique!to!bacteria, disrupting!bacterial!protein!synthesis! (bacterial!and!human! ribosomes!are!different). 1. !identification!of!the!bacteria: ideally,!bacteria!are!identified!prior!to!selection!of!the!treatment, the!gram!stain!is!a!rapid!test!that!provides!information!on!the!structural! features!of!the!bacteria, in!general,!culturing!the!bacteria!to!properly!identify!it!will!provide!the!best! basis!for!selection!of!the!therapy, in!some!cases,!cultures!are!not!possible!or!reliable!for!identifying!the! bacteria. ! !these!infections! require!careful!selection!of!antibiotics!that!are!able!to!penetrate!to!the!site!of! action: meningitis, urinary!tract!infections, osteomyelitis, abscesses, otitis!media! Is!an!infection!of!the!meninges,! which!are!the!membranes!that! cover!the!brain!and!spinal!cord: bacterial!meningitis!is!rare!but! is!much!more!serious!than!viral! meningitis!(i. e. !life!threatening), many!antibiotics!are!unable!to! penetrate!the!meninges, therefore,!effective!treatment! requires!an!antibiotic!that! penetrates!the!meninges!and! effectively!eradicates!the! bacteria. ! Urinary!tract!infections! (utis): urinary!tract!infections!occur! when!bacteria!enter!any!part! of!the!urinary!system, the!most!common!type!is!an! infection!of!the!bladder,! which!may!be!caused!during! catheterization, effective!treatment!of!utis! requires!an!antibiotic!that! enters!the!urinary!system. Osteomyelitis: osteomyelitis!is!an!infection! of!the!bone, very!few!antibiotics!are!able! to!enter!the!bone,!making! treatment!options!limited, treatment!of!osteomyelitis! usually!requires!antibiotics! for!4! !6!weeks. !abscesses: skin!abscesses!occur!when!pus! or!other!infected!material! collect!under!the!skin, abscesses!are!difficult!to!treat! with!antibiotics!because!they! are!poorly!perfused!with!blood. Otitis!media: otitis!media!is!an!infection!of! the!middle!ear!and!more! commonly!referred!to!as!an! ear!infection, anybody!can!get!an!ear! infection,!but!they!are!much! more!common!in!children, many!antibiotics!do!not! penetrate!the!inner!ear!and! are!therefore!not!effective!in! the!treatment!of!otitis!media. !