BACTERIA OF KEY PUBLIC HEALTH IMPORTANCE Flashcards
WHAT DOES IT MEAN IF AN ORGANISM IS ‘FACULTATIVE ANAEROBIC’?
THAT IT CAN FUNCTION WITH OR WITHOUT OXYGEN
HOW ARE BACTERIA COMMONLY GROUPED BASED ON THEIR ABILITY TO CAUSE DISEASE?
TO PATHOGENIC (CAUSES DISEASE) AND COMMENSAL (LIVES ON HOST WITHOUT CAUSING HARM)
WHAT ARE COMMENSAL BACTERIA?
BACTERIA WHO LIVE ON A HOST BUT DON’T CAUSE ANY HARM
BASED ON WHICH FEATURES DO WE USUALLY DESCRIBE BACTERIA?
GRAM STAIN, SHAPE, O2 USE, DRUG RESISTANCE, TOXINS, POTENTIAL TO CAUSE DISEASE
WHAT IS THE DIFFERENCE BETWEEN GRAM POSITIVE AND GRAM NEGATIVE BACTERIA?
Gram-negative bacteria are surrounded by a thin peptidoglycan cell wall, which itself is surrounded by an outer membrane containing lipopolysaccharide. Gram-positive bacteria lack an outer membrane but are surrounded by layers of peptidoglycan many times thicker than is found in the Gram-negatives.
WHAT IS GRAM STAINING?
Gram stain or Gram staining, also called Gram’s method, is a method of staining used to classify bacterial species into two large groups: gram-positive bacteria and gram-negative bacteria.
Gram staining differentiates bacteria by the chemical and physical properties of their cell walls. Gram-positive cells have a thick layer of peptidoglycan in the cell wall that retains the primary stain, crystal violet. Gram-negative cells have a thinner peptidoglycan layer that allows the crystal violet to wash out on addition of ethanol. They are stained pink or red
COLOUR OF GRAM POSITIVE VS GRAM NEGATIVE BACTERIA UPON STAINING?
POSITIVE: VIOLET
NEGATIVE: RED OR PINK
WHAT IS A NATURAL HISTORY OF A DISEASE?
IT DESCRIBES THE DISEASE’S EXPECTED PROGRESSION OVER TIME, FROM WHEN A PERSON IS FIRST INFECTED ONWARDS; THIS WOULD INCLUDE WHICH SYMPTOMS TYPICALLY APPEAR AND IN WHAT ORDER
WHAT IS THE INCUBATION PERIOD?
THE TIME BETWEEN A PERSON BEING INFECTED AND WHEN THEY START TO SHOW SYMTPOMS
WHAT IS THE LATENT PERIOD?
THE TIME BETWEEN A PERSON BEING INFECTED AND WHEN THEY START BEING INFECTIOUS TO OTHERS
WHAT IS THE INFECTIOUS PERIOD?
THE PERIOD OF TIME A PERSON IS INFECTIOUS
EXPLAIN THE COMMON EPIDEMIOLOGICAL FRAMEWORK FOR DESCRIBING PATTERNS OF DISEASE?
TIME-PLACE-PERSON
TIME: IS THE DISEASE SEASONAL?, HAS THE PATTERN OF DISEASE BEEN CHANGING OVER TIME?
PLACE: DOES THE PATTERN OF DISEASE VARY BY PLACE?
PERSON: WHO IS AT RISK? WHO IS AT RISK OF SEVERE DISEASE?
TYPES OF PREVENTION STRATEGIES; EXPLAIN:
PRIMARY: AIMS TO PREVENT A CONDITION FROM OCCURRING
SECONDARY: AIMS TO LIMIT DISEASE PROGRESSION AND MODIFY THE DISEASE BY EARLY INTERVENTION ONCE IT HAS ALREADY OCCURRED
TERTIARY: AIMS TO PREVENT COMPLICATIONS OF THE DISEASE
EXAMPLES OF PRIMARY, SECONDARY AND TERTIARY PREVENTION?
PRIMARY: VACCINATION, HAND WASHING, PROGRAMMES ENCOURAGING HEALTHY LIFESTYLES
SECONDARY: BREAST CANCER SCREENING
TERTIARY: DIABETIC EYE SCREENING
DESCRIBE THE NEISSERIA MENINGITIDIS PATHOGEN?
- GRAM NEGATIVE
- AEROBIC
- DIPLOCOCCAL BACTERIUM (OCCURS AS PAIRS OF COCCI, CIRCULAR)
SOME NEISSERIA SPECIES EXCEPT FOR N. MENINGITIDIS?
N. GONORRHOEAE (CAUSES THE STI GONORRHOEA)
N. LACTAMICA (COMMENSAL)
1 IN HOW MANY PEOPLE HAVE N. MENINGITIDIS LIVING HARMLESSLY IN THEIR THROATS AND NOSES?
1/10
UP TO 1/4 IN ADOLESCENTS
WHAT DOES THE TERM MENINGOCOCCAL DISEASE OR INVASIVE MENINGOCOCCAL DISEASE (IMD) REFER TO?
DISEASES CAUSED BY N. MENINGITIDIS;
A) MENINGITIS
B) SEPTICAEMIA
WHAT IS MENINGITIS?
INFLAMMATION OF THE MENINGES - THE MEMBRANES COVERING THE BRAIN AND SPINAL CORD
WHAT IS SEPTICAEMIA?
BLOODSTREAM INFECTION
HOW MANY SEROGROUPS DOES N. MENINGITIDIS HAVE? WHICH ONES ACCOUNT FOR MOST CASES OF INVASIVE DISEASE?
13 SEROGROUPS
6 ACCOUNT FOR MOST CASES OF INVASIVE DISEASE:
A, B, C, W-135, X, Y
WHAT ARE THE 2 MAIN STRAINS OF N. MENINGITIDIS?
ENCAPSULATED AND UNENCAPSULATED
FEATURES OF N. MENINGITIDIS THAT MAKE IT MORE DIFFICULT FOR THE IMMUNE SYSTEM TO FIGHT IT?
THE CAPSULES (IN THE CAPSULATED FORMS WHICH MORE COMMONLY CAUSE INVASIVE DISEASE) CONTAIN A TYPE OF SIALIC ACID THAT IS SIMILAR TO THOSE FOUND IN THE HUMAN BODY, AND THIS ACTS AS A PARTIAL CAMOUFLAGE TO THE IMMUNE RESPONSE
N. MENINGITIDIS ALSO CONTAINS PILI (HAIR LIKE STRANDS) WHICH HELP THE BACTERIA STICK TO THE CELLS ON THE INSIDE OF THE THROAT/NOSE
WHICH CAPSULATED GROUP OF N. MENINGITIDIS DOES NOT CONTAIN SIALIC ACID?
GROUP A