L7 Hx Hyg And Hosp Infec

Question 1

LO2: expl imp kochs postulates. 1877.

Answer 1

To determ if infec Ag in cause of dis.

• org occs in ev case of dis. Occs in no other dis. On remov from bod and pure cult can induce dis in new indiv.
• LIMS- org in ev case- defin of dis, diffic isol eg can’t pure cult leprosy/syph. Occ in no other dis, or in health- commensalism can be pathogens, endoc infec, colonisat w/o symp. Pure cult re infec- no mod if eg fatal, no pure cult eg virus.
• SUCC- anthrax, thyroid, gonorrhoea, TB, cholera, leprosy. Agents sev dis, absent in healthy.
• FAIL- influ and vits- many contradict findings. New meths- Ab and skin tests. Now molec biol and molec KPs to ID sing molecs as causal agents.

Question 2

LO3: role pop studies in link microorganism to dis.

Answer 2

• influ 1st vir isol, lot pandemics. Bef 1890 miasma so/poison vamp. 1892 gram neg bacillus isol from pt=H influenza epidemic. 1918 pandem 100mill die. Not isol ev case so not consid cause. 1932 nasal sec inoc ferret, isol cult. Ab in pt and pop- pop studies linked seas flu an pandemics.
• Ebola Sudan and Zairean vir isol, Ab in over 80% surv, 20% loc comm had Ab w/o ever symps.
• new patt time and place=investig. HUS assoc cytotox prod of ecoli. Case contr study. NOT Koch but clear, coherent, consis, biol plausib and built on prior lit.
• lot new infec agents post 19770 eg HIV, campylobacter, Lyme, parvovirus.

Question 3

LO4: desc how infec dis spread.

Answer 3

• PATHOG- encounter. Ent/est. to infec directly or after colonisat. Spread, surv, multip. Incr dam/dysfunc event=symp. Pathog ent norm biota-carrier status.
• infec transm- reservoir where agent grows. To immed source, own microbiota when endog. Mode of transm to susceptible host. Handwash best protec even aerosols.
• exog eg pharyngitis/quinsy- reserv and source hum upper RT. Airb transm.
• endog eg UTI. Reserv hum colonic bact. Immed source peri anal skin. Mech transm.
• tetanus- reserv soil/anim int. Immed source is anyth contam. Transm by inj/impl.
• syphill- reserv infec hum, immed source is infec lesion. Sex transm.
• haemorr fever- reserv anim, source anim bod fluid or insect vec. Transm by contact/bite/bod fluid.

Question 4

LO5: Id key elems in underpinn probs and sols in contr infec in hosp.

Answer 4

-prev transm- elim microbe from immed source and/or reserv if exog. Or isol suscep host from immed source. Or just protect immed source. Or prev mode transm.
-HAI-1/10 admiss. Incr AV stay 11d. 5000die/yr. £1bn NHS. Partic ICU and AB resis. Eg vancomycin resis enterococcus. Cohort int, hand washing, AB restric.
-mod infec- R0=rate indiv infec prods new infec in new indivs, any exog agent. Deps on: time period of infective try (D), rate of mix btw infec and suscep, capac for transm (beta coefficient), no infected indivs contacted by infec indivs dur infective period (X).
Capac basic repro rate of infec after intro to suscep pop.
R0=beta X D. If over 1=infec propagates. Under 1 dies out.

Question 5

LO1: prov historic perspective to sci underst of cause infec dis.

Answer 5

Hippoc epidemics.
16C seeds infec.
17C Leeuwenhoek microorganism purp movem.
18C hunter transm physic mater. Gonorrhoea, Soph.
19C snow prev transm. Semmelweis fever post natal. Pasteur spont gen. Nightingale stat. Lister phenol. Koch dis from microbes propag in vitro, isol pure cult, induces dis. Beijerwick filt Gas of dis- vits.
20C Ehrlich magic bullet, selec kill. Fleming Eric. Andrews isol influ.
21C post AB era.