Bacterial Infections Flashcards
(193 cards)
1
Q
Staphylococcus aureus - morphology and gram stain
A
Gram positive (purple) bunches of cocci
2
Q
Streptoccus pneumoniae - morphology, gram stain
A
Gram positive (purple) diplococci
3
Q
Staphylococcus epidermidis - morphology and gram stain
A
Gram positive (purple) bunches of cocci
4
Q
Neisseria meningitidis - morphology and gram stain
A
Gram negative (pink) diplococci
5
Q
Neisseria gonorrhoea - morphology and gram stain
A
Gram negative (pink) diplococci
6
Q
Clostridium difficile - morphology and gram stain
A
Gram postive (purple) rods
7
Q
Clostridium perfringens - morphology and gram stain
A
Gram positive (purple) rods
8
Q
Streptococcus pyogenes - morphology, gram stain and group
A
Gram positive (purple) chains of cocci, referred to as Group A Streptococci or GAS
9
Q
Escherichia coli - morphology and gram stain
A
Gram negative (pink) rods
10
Q
Salmonella - morphology and gram stain
A
Gram negative (pink) rods
11
Q
Bordetella - morphology and gram stain
A
Gram negative (pink) cocci
12
Q
Non typhoidal salmonella (NTS) - morphology and gram stain
A
Gram negative (pink) rods
13
Q
Typhoidal salmonella (enteric fever) - morphology and gram staining
A
Gram negative (pink) rods
14
Q
Haemophilus influenzae - morphology and gram stain
A
Gram negative (pink) cocci
15
Q
What is the test for gram staining?
A
1 - Stain slide with crystal violet for 1-2 minutes
2 - Flood slide with Gram’s iodine for 1-2 minutes
3 - Decolourize slide by briefly washing with acetone for 2-3 seconds
4 - Stain with safranin counterstain for 2 minutes
5 - View under microscope
16
Q
What are the main differences between Gram positive and negative bacteria?
A
Gram negative bacteria have an outer membrane.
Gram positive have 90% peptidoglycan and negative have 10%.
17
Q
What are the implications of differences between gram positive and gram negative bacteria?
A
Susceptible to different antibiotics, different ability to survive infection control procedures and cause different diseases.
18
Q
Cocci can be arranged…
A
Singularly, in pairs, in bunches, in chains.
19
Q
Rods can be arranged…
A
Singularly or in chains.
20
Q
Rods can be shaped…
A
Fat or thin, long or short.
21
Q
Streptococcus pyogenes is (?)-haemolytic and which colour does this show on blood agar?
A
Beta-haemolytic and this shows as yellow with zone of clearing around colonies. (Beta-better at degrading)
22
Q
Streptococcus pneumonia is (?)-haemolytic and which colour does this show on blood agar?
A
Alpha-haemolytic and this shows as green and is partially degrading.
23
Q
Clostridium difficile and perfringens form what?
A
Anaerobic (air hating) spores.
24
Q
Neisseria meningitidis is capsulated/non-capsulated?
A
Capsulated.
25
Neisseria gonorrhoea capsulated/non-capsulated?
Non-capsulated.
26
Haemophilus influenzae capsulated/non-capsulated?
Capsulated.
27
Neisseria meningitidis is motile/non-motile?
Non-motile.
28
Neisseria gonorrhoea is motile/non-motile?
Motile.
29
Neisseria meningitidis is referred to as what?
The meningococci.
30
Non-haemolytic bacteria is called what?
The enterococci.
31
Which of these is more important medically? Alpha and beta haemolytic or non-haemolytic.
Alpha and beta haemolytic.
32
Which bacteria are classified by putting on blood agar (haemolytic)?
Streptococcus (e.g. this method is used to determine streptococcus pneumoniae from streptococcus pyogenes).
33
What percentage of infections caused by Haemophilus influenzae are invasive?
80%.
34
Haemophilus influenzae causes what mainly?
Meningitis - however not most common cause of meningitis due to vaccine.
35
Bordetella pertussis causes what?
Whooping cough.
36
The only reservoir for bordetella pertussis is what?
Humans.
37
Whooping cough most commonly affects who, and what are the important death rates for this group?
Under 1's, with 90% of deaths from this in babies under 3 months old.
38
Recent cases of whooping cough has been observed in which age range?
15-40 year olds.
39
Whooping cough is more severe in whom: adults or babies?
Babies, cases in adults are more mild.
40
Neisseria gonorrhoea is commonly called what?
The gonococci.
41
Neisseria gonorrhoea is ranked where in STD's in the UK?
2nd.
42
What type of infections does Neisseria gonorrhoea cause?
Urethral, rectal, throat - men and women. Endocervical - women. Eye infections in newborns - contracted during passage through birth canal - conjunctivitis - yellow, crusty eyes.
43
Neisseria gonorrhoea is symptomatic/asymptomatic?
Asymptomatic - causes increase in cases in new sexual partners as not showing signs of infection.
44
Neisseria gonorrhoea can lead to what?
Pelvic inflammatory disease and ectopic pregnancy.
45
What is the leading cause of meningitis?
Neisseria meningitidis.
46
What type of meningitis is caused by Neisseria meningitidis?
Typically Group B due to lack of vaccine.
47
Meningitis caused by Neisseria meningitidis can be associated with what and what does this mean must happen?
Septicaemia - prompt antibiotics are needed.
48
Non-typhoidal salmonella is abbreviated to what?
NTS.
49
Typhoidal salmonella is sometimes called what?
Enteric fever.
50
Non-typhoidal salmonella causes what?
Gastrointestinal disease previously associated with eggs. Associated with gastroenteritis and diarrhoea.
51
How is non-typhoidal salmonella transmitted?
Faecal-oral route or contaminated foods.
52
Typhoidal salmonella causes what?
Typhoid fever.
53
What are the symptoms of typhoid fever?
Systemic symptoms - fever. Symptoms to look out for are diarrhoea in the returning traveller.
54
Typhoidal salmonella is maintained by carriers how?
Passing it on through poor hygiene- e.g. Typhoid Mary.
55
The enterobacteriaceae includes what?
Escherichia coli and salmonella.
56
Escherichia coli typically colonises/infects the GI tract.
Typically colonises but virulent (disease-causing) strains can cause infections.
57
What type of infections does Escherichia coli commonly cause?
UTI's - simple - resolve without treatment, complicated - can lead to kidney infections such as pyelonephritis. Bacteraemia, GI infections (travellers diarrhoea).
58
Predisposing factors for developing UTI's include what?
Being female (shorter urethra), sexual intercourse, pregnancy and catheterisation.
59
Escherichia coli also causes what?
Severe infection is caused by EHEC (enterohaemorrhagic e.coli) e.g. E.coli 0157 - can lead to haemorrhagic colitis and haemolytic uremic syndrome. Rarely causes neonatal meningitis.
60
Clostridium perfringens flourishes in what?
Necrotic (dead) tissue.
61
Clostridium perfringens can cause what?
Gas gangrene.
62
Treatment for clostridium perfringens is what?
Surgical debridement or amputation.
63
Streptococcus pyogenes can cause what?
Tonsillitis, skin and soft tissue infections such as impetigo and cellulitis and necrotising infections such as necrotising fasciitis.
64
Necrotising fasciitis is also referred to as what?
Flesh eating disease.
65
Streptococcus pneumoniae is capsulated/non-capsulated?
Capsulated.
66
The presence of a capsule around streptoccus pneumoniae is linked to what?
Invasive infections.
67
Invasive infections are linked to what?
Capsules around the bacterium.
68
Streptococcus pneumoniae can cause what?
Pneumonia, meningitis, septicaemia, otitis media, ear infections, septic arthritis and sinusitis.
69
Urgent antibiotics are needed for meningitis - true/false?
True.
70
Symptoms of pneumococccal meningitis in adults include?
Blotchy, non-blanching, red rash; headache; fever; nausea and vomiting.
71
Streptococcus pneumonia colonises the nasopharynx in..
5-10% healthy adults, 40% healthy children.
72
Symptoms of pneumococcal meningitis in under 2 year olds include?
Floppy; unresponsive; pale, blotchy skin; staring expression; loss of appetite and vomiting.
73
How is streptococcus pneumonia treated?
Depends on sensitivity - if sensitive - penicillin. Vancomycin can be used. Sensitivity takes time to determine due to needing to grow culture.
74
How streptococcus pneumonia be prevented?
Vaccination: Pneumococcal conjugate vaccine in under two's, pneumococcal polysaccharide vaccines in over 65's.
75
Invasive pneumococcal diseases mainly affect?
Under two's: 20% cases, over 65's.
76
Symptoms of pneumonia (Streptococcus pneumoniae)?
Productive cough, rusty sputum, fever.
77
Streptococcus pneumoniae accounts for what percentage of pneumonias?
25-60%.
78
What percentage of sore throats are viral?
90%.
79
GAS infections in the throat can cause what complications?
Scarlet fever, Quinsy, Sinusitis.
80
How are GAS throat infections treated?
Oral antibiotics - amoxicillin.
81
Impetigo is most commonly seen in who and when?
Children: 2-5 year old, more commonly in summer than winter.
82
Symptoms of impetigo are?
Bullae/blisters which burst releasing a yellow discharge which crusts.
83
How is impetigo treated?
With oral antibiotics - flucloxacillin.
84
Impetigo is contagious - true or false?
True.
85
How is cellulitis contracted?
Enters skin through trauma or previous lesion/boyle?
86
What are the symptoms of cellulitis?
Hot red skin that rapidly spreads.
87
Treatment for cellulitis is what?
Anti staph/strep antibiotics such as flucloxacillin or penicillin.
88
How is cellulitis monitored?
Draw around redness to monitor progress from treatment.
89
Necrotising fasciitis is a medical emergency - true/false?
True.
90
What is necrotising fasciitis?
Acute infection of deeper layer of skin (fascia).
91
What are the symptoms of necrotising fasciitis?
Red, hot, painful, swollen skin.
92
What can necrotising fasciitis progress to?
Cutaneous gangrene (death of tissue) or if severely unwell - septic shock.
93
What are the predisposing factors for necrotising fasciitis?
Trauma/surgical wounds, diabetes, intravenous drug use.
94
What is the mortality for necrotising fasciitis?
20-30%
95
Treatment for necrotising fasciitis?
Aggressive treatment with intravenous antibiotics and debridement of dead tissue.
96
How does c.perfringens cause gas gangrene?
Spore makes its way into wound.
Germinates and produces toxins.
Foul discharge and pain.
97
How can c.perfringens be prevented?
Clean and debride wounds.
98
How does c.diff cause diarrhoea?
Antibiotic use kills normal flora allowing c.diff to flourish. Releases toxins which at a certain level cause diarrhoea.
99
Gut commensal for c.diff?
3% adults, 75% children.
100
Main risk factors for c.diff?
Over 65 (80% cases), using a broad spectrum antibiotic.
101
Treatment for c.diff?
Metronidazole, Vancomycin, Fidaxomicin.
102
Outcomes of c.diff?
Can cause pseudomembranous colitis - inflammation of the colon causing diarrhoea (offensive smelling), abdominal pain and fever.
103
What can pseudomembranous colitis as a result of c.diff lead to?
Toxic mega colon - extreme dilation of the colon.
104
Fatality of toxic mega colon?
40-50% of cases.
105
Treatment for toxic mega colon?
Possible removal of bowel and vancomycin.
106
Treatment for pseudomembranous colitis?
Vancomycin.
107
American treatment for c.diff?
Homogenise relatives faeces and feed to patient to replace natural flora.
108
What is SIGHT prevention?
```
Suspect that a case is infective
Isolation
Gloves and aprons
Hand washing
Test stool for toxin
```
109
Prevention is better than cure - true or false?
True.
110
Why has incidence of c.diff declined?
Better prescribing of antibiotics
More isolation
Better environmental disinfection
Better hand hygiene
111
Many gram positive bacteria are members of the normal flora - asymptomatic carriage - true or false?
True.
112
Bacteria can cause a range of diseases from minor to medical emergencies - true or false?
True.
113
The prevention of spore contamination is essential in preventing clostridial infections - true or false?
True.
114
Staphylococcus aureus causes what?
Skin and soft tissue infections such as cellulitis and impetigo (leading cause), food poisoning, bone infections, endocarditis and bacteraemia (bugs in blood).
115
Staphylococcus aureus is present in what percentage of the population and where?
Nose of 30-40% of population.
116
How does s.aureus cause scalded skin syndrome?
Caused by 6-10% of s.aureus strains. Strain grows locally and then moves to blood but only affects the skin causing top layers to shed (exfoliation).
117
Who is affected by scalded skin syndrome?
Children under 6.
118
What is the mortality of scaled skin syndrome?
Less than 3% of cases.
119
How is scalded skin syndrome treated?
With oral antibiotics
120
Side effects of scalded skin syndrome?
Fluid loss through impaired sweating and blistering.
121
Strep toxic shock has a mortality of what?
40%.
122
Toxic shock syndrome related to s.aureus has a mortality of what?
<3%.
123
Why are adults not affected by scalded skin syndrome?
The adult immune system can deal with the toxin.
124
Fluid found in scalded skin syndrome blisters are sterile - true/false?
True.
125
Mortality of scalded skin syndrome?
<3%.
126
Toxic shock syndrome is caused by what?
S.aureus.
127
Scalded skin syndrome is caused by what?
S.aureus.
128
What percentage of T-Cells are activated in TSS?
30% - massive immune response effecting multiple organs. Normal infections activate 0.1%
129
Effects of TSS?
Fever, hypotension, rash, desquamation of skin on soles and palms.
130
TSS is associated with what?
Tampons - breeding ground for S.aureus causing toxin secretion and mass immune response.
131
MRSA stands for?
Methicillin resistant staphylococcus aureus.
132
What is MRSA resistant to?
Penicillin and other antibiotics
133
MRSA is common in...
Elderly
Lines and catheters
Surgical wounds
Intensive Care Units
134
Treatments for MRSA?
Vancomycin
135
Staphylococcus epidermidis causes infection where?
Catheters
Long lines
Cannulae
Indwelling medical devices (pacemakers etc.)
136
How often should cannulae be changed?
Every 72 hours.
137
How are bacteria classified?
First by gram stain and what they look like under a microscope, then by properties often based on biochemical reactions - e.g. one may be able to metabolise a sugar that another can't.
138
Gram stain differentiates most bacteria but not all - true/false?
True.
139
What is the gram stain based on?
Cell wall type.
140
Bacteria are what size?
<15 micrometres length
141
Bacteria are capable of independent replication - True/false?
True.
142
Bacteria are the cause of most infections seen in hospital - true/false?
True.
143
There are many different species on bacteria - true/false?
True.
144
Bacteria is treated using antibiotics?
True.
145
Humans are super organisms comprising of what ration bacterial to human cells?
10:1
10^14 bacterial cells
10^13 human cells
146
How are complications from GAS infections treated?
With oral antibiotics - amoxicillin.
147
Medically important gram negative bacteria include?
Escherichia, salmonella, shigella, proteus, klebsiella, enterobacter, citrobacter, yersinia.
148
Which bacteria is notorious for encrustation of catheters and how long does it take to do so?
Proteus mirabilis (gram negative) - withing 10 days.
149
What does shigella cause?
Watery diarrhoea.
150
Salmonella are not commensal - true or false?
True.
151
All strains of salmonella cause disease in humans - true or false?
True.
152
How many eggs are now contaminated with salmonella due to chicken vaccination?
0.1%
153
What is the source of salmonella?
Poultry, cattle, reptiles, arthropods and humans (enteric fever).
154
What type of infection can salmonella cause?
Self-limiting (diarrhoea) or enteric fever (typhoid).
155
What is the pathway for gastroenteritis caused by salmonella?
Ingestion of viable bacteria (10^4-7 cells)
Non typhoidal salmonella - 12-72 hours
Gastroenteritis - often localised to GI, diarrhoea, short clinical course (<10 days).
156
What is the pathway for enteric fever caused by salmonella?
Ingestion of viable bacteria (10^4-7 cells)
Typhoidal salmonella - 7-14 days
Enteric fever - system infection, diarrhoea/constipation
Longer symptom duration than gastroenteritis (3 weeks)
Can lead to either acute or chronic carriage
157
Shigella is also called?
Bacillary dysentery.
158
Shigella causes what?
Shigellosis - dysentery.
159
Enteric fever is caused by what?
Salmonella paratyphi or typhi
160
How many people are infected annually with enteric fever?
17 million.
161
How many deaths annually from enteric fever.
600,000.
162
What percentage of people infected with enteric fever become chronic carriers?
5%.
163
The infectious does of shigella is very low - true or false?
True.
164
Symptoms of shigellosis are?
Abdominal cramps, tenesmus (intense desire to use the toilet), frequent passage of mucoid - bloody diarrhoea.
165
How is shigella spread?
Person to person via faecal-oral route.
166
Outbreaks of shigella are typically seen where?
Primary schools.
167
E.coli is commensal in the human gut - true or false?
True.
168
Source and transmission of E.coli?
Natural habitats - GI tracts of human, pigs, amphibians, fish and cattle. Transmission: undercooked contaminated meat, unpasteurised dairy products, contaminated fruit and vegetables, environmental contamination.
169
Which is the first type of clincal syndrome for E.coli and which version of this is most relevant to us? Is it commensal?
Diarrhoeagenic
| EHEC - enterohaemorrhagic - Most important - non-commensal.
170
Most relevant strain of EHEC?
E.coli 0157.
171
How common is e.coli 0157?
Relatively rare
172
What does e.coli 0157 cause?
Mild gastroenteritis to severe bloody diarrhoea.
Can result in:
Haemorrhagic colitis: Abdominal pain, watery diarrhoea.
Haemolytic uremic syndrome (HUS): Renal failure, bloody diarrhoea.
173
For positive ID of UTI there must be:
High bacterial cell numbers, symptoms and raised white blood cell count in urine.
174
What is used to treat e.coli UTI's?
Trimethoprim.
175
Types of UTI and where are they found:
Kidney: Pyelonephritis
Bladder: Cystitis
Urethra: Urethritis
176
How do UTI's get to the kidney?
Through the cysto-ureteric valve and bacterial ascension to the kidney.
177
Cystitis is most common in?
Young females who have been sexually active recently.
178
What percentage of women report 1 or more than 1 case of cystitis?
50%
179
Treatment for cystitis?
Can be treated empirically (before diagnosis) by GP with antibiotics or may be uncomplicated and resolve alone.
180
Symptoms of cystitis?
Burning sensation when urinating.
181
Symptoms of pyelonephritis?
Same as cystitis but also severe lower back pain, fever, chills and nausea and vomiting. Bacteraemia may be present. Costovertebral (CVA) tenderness. Elevated red blood cell count in urine and white blood cell casts may be seen.
182
Pyelonephritis can lead to what?
Urosepsis.
183
Which two bacteria are the most responsible for UTI's?
E.coli and staphylococcus prophyticus.
184
Less common causes of UTI's include?
Klebsiella spp., Enterobacter spp., Proteus spp., Citrobacter spp., Pseudomonas spp., Group B Strep, Group D Strep, Enterococci, Corynebacterium urealyticum and Yeasts.
185
How does proteus mirabilis act on culture plates?
Swarming.
186
Besides catheter encrustation what does proteus cause?
UTI, bacteraemia and pneumonia.
187
What does proteus form?
A biofilm.
188
What does bacteria in catheter urine indicate?
Not definitely indicative of infection, often indicates colonisation but catheter should be removed.
189
Bacteraemia can lead to what?
Sepsis.
190
Increase of bacteraemia between 2004-2008 and 2009-2010? What happened in June 2011?
2004-2008: 33%
2009-2010: 5%.
June 2011: Mandatory surveillance
191
What are 50% cases of sepsis attributed to?
Pneumonia.
192
Diagnosis of sepsis?
Symptoms: Fever - over 38 or hypothermia under 36.
Raised heart rate - over 90 bpm.
Fast breathing.
Nausea.
Confusion.
Evidence of an infection. (50% attributed to pneumonia)
193
Types of sepsis?
Uncomplicated: no need for hospital admission.
Severe: Interference with vital organs - heart, kidneys and lungs.
Septic shock: Severe, organ failure, 20-30% mortality, over 60% cases yield gram negative bacteria.
