Infection 2 Flashcards
What are the mechanisms by which a human may become infected with pathogenic organisms?
For each mechanism, include an example of how it might occur or an example of an infection that occurs due to this mechanism
Contiguous:
Anus to vagina spread of faeces (UTI)
Peritonitis secondary to burst appendix
Inoculation:
Bite/Stabbing (Tetanus, Rabies)
Haematogenous:
Vascular transmission of bacteria from mouth to heart (Endocarditis)
Ingestion:
Faeco-oral transmission (Food poisoning)
Inhalation:
Aerosols (TB, Chickenpox)
Vector:
Insects (Mosquitos and Malaria)
Vertical transmission:
In utero or during birth (Syphilis, HIV)
What are the major patient factors that influence suseptibility to infection?
Person:
Age
Gender
Physiological state
Pathological state
Social factors
Time:
Calendar time
Relative time
Place:
Current
Recent
Give some ways in which age can affect infection
Early life:
0-3 months protection provided by mother’s antibodies
3mnths to 3yrs High risk
Sexual activity:
Rise in STDs after mid teens until 30s
Old age:
Infections steadily rise post 50
Give examples of how physiological state can affect infection
Puberty, Pregnancy and menstrual cycle affect pH of vagina, raising suseptibility to vaginal infection
During pregnancy it is theorised that that colonic microbiota can affect gestational diabetes development
Give examples of how pathological state can affect infection
HIV caused immunocompromised patients to pick up additional infections
Cancer, bone marrow transplant and haemotology patients immunocompromised, can cause physiological aspergillus colonies becoming pathological
Give an example of how social factors may affect infection
Young school children can pick up infections such as chickenpox from classmates (association with specific groups can increase risk of infection)
How does calendar time affect infection?
Certain infections more likely in certain seasons
Eg. Norovirus and influenza spread during winter
What is meant by ‘relative time’ in regards to infection and how does it affect infection?
Refers mainly to differences in time scales of infections
E.g. Length of incubation period if known can guide how long we quarantine possible cases of severe pathogenic infection
How does the patient’s recent travel and current location affect our management of infection?
Both can guide the physican to possible micro-organisms that are causing infection based on where those micro-organisms are found
What are the two major modes of host damage caused by infection?
Direct damage from toxins
OR
Interaction with host defenses leading to direct damage or inflammation (which in turn causes damage)
What are the 3 things that must be done to make a diagnoses in a patiet with suspected infection?
History taking
Examinations
Investigations
What are the differences between specific and supportive treatment of infection?
Give specific examples
Supportive:
Focused on symptom relief and restoring normal physiological state
E.g. Fluid replacement
Specific:
Targeted treatments at specific micro-organisms or body systems
E.g.
Antimicrobials
Surgery (drainage, debridement, dead space removal)
Where does infection prevention occur and why is it important?
Occurs in hiospital and community
Important because it prevents transmission to other patients, healthcare workers etc.
Explain the different outcomes of infection
Cure:
Infection completely removed
Chronic:
Chronic infection can persist
Can cause disability
Death
What are the different broad types of anti-microbial?
Antibacterial
Antifungal
Antivarial
Antiprotozoal
What are the different ways of classifying antibacterial agents?
Bacteriocidal or bacteriostatic
Broad or narrow spectrum
Target site (mechanism of action)
Chemical structure (antibacterial class)
What ae the ideal features of an antimicrobial agent?
Selectively toxic
Few adverse effects
Reach site of infection
Both oral and IV formulations
Long half life (infrequent dosing)
No interference with other drugs
What are the 4 major targets of antibacterial action?
Give examples of classes of each
Cell wall synthesis
Beta lactams
Glycopeptides
Protein synthesis
Tetracyclines
Aminoglycosides
Macrolides
Cell membrane function
Polymixin
Nucleic acid synthesis
Quinolones
Rifampicins
Give the two mechanisms of inhibition of bacterial cell wall synthesis and an example of an antibacterial that utilises this method
Penicillin:
Inhibits penicillin binding protein, which creates crosslinks between cell wall proteoglycans
Vancomycin:
Stops cell wall cross linking enzyme from binding to preoteoglycans and cross linking them
