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Microbiology Flashcards

1
Q

Pathogen

A

An organism capable of causing disease

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2
Q

Commensal

A

An organism which colonises the host but causes no disease in normal circumstances

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3
Q

Opportunist pathogen

A

A microbe that only causes disease if host defences are compromised

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4
Q

Virulence/pathogenicity

A

The degree to which an organism can cause disease

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5
Q

Asymptomatic change

A

When a pathogen is carried harmlessly to a tissue or site where it causes no disease

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6
Q

Bacterial nomenclature

A

Genus
Species
Streptococcus (genus) pyogenes (species)

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7
Q

Mucosal surfaces tend to be

A

colonised

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8
Q

Bacterial morphology

A 
Cocci - round
Bacilli - rod shaped
Diploccocus, chain, cluster (cocci shapes)
Filamentous/branching (rod shapes)
Spirochaetes (spiral shaped)
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9
Q

Stains

A

Purple - gram positive

Pink - gram negative

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10
Q

Protect bacteria from the host immune system

A

Polysaccharide capsule

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11
Q

Allow bacteria movement

A

Flagella

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12
Q

Allow bacteria to attach and colonise to host

A

Pili

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13
Q

Ziehl-neelsen stain

A

Stain for TB (mycobacterium tuberculosis)

Acid fast bacilli

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14
Q

Bacterial cell envelope

A

Gram-positive - single PL membrane containing peptidoglycan

Gram-negative - inner cytoplasmic with peptidoglycan and outer lipopolysaccharide membrane (double-membrane)

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15
Q

Spores

A

A hardened structure which is resistant to desiccation and harsh conditions within bacteria

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16
Q

Bacterial environemnt

A

Extreme temps
Low pH
Months without water
UV light

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17
Q

Growth rate of bacteria

A

Rapid

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18
Q

Bacterial toxins

A

Endotoxin - component of the outer membrane of bacteria - lipopolysaccharide in gram-negative bacteria, non-specific, stable under heat
Exotoxin - secreted proteins of gram-positive and gram-negative bacteria, can convert to toxoid, specific, unstable under heat

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19
Q

Tetanus

A

Clostridium tetani - causes muscle spasms due to nerve hosting

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20
Q

Bacterial plasmids

A

Provide resistance

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21
Q

Bacterial conjugation

A

‘bacterial sex’

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22
Q

Bacterial genetic variation

A

Mutation

Gene transfer

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23
Q

Impetigo

A

Crusty lesion on the face

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24
Q

Gram-positive bacteria

A

Streptococcus

Staphylococcus

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25
Bacteria can be
Aerobic | Anaerobic
26
Gram pos bacteria
peptidoglycan only | Purple on gram stain
27
Staph aureus treatment
Flucloxacillin
28
Staphylococcus species
40 Coagulase positive or negative Coagulase - enzyme produced that clots blood plasma and this fibrin clot formed around bacteria protects it from phagocytosis S aureus is coag pos Normal habitat - nose and skin Spread by air and touch MRSA - resistant to B-lactams, gentamicin, erythromycin, tetracycline. Resistance transferred by MecA gene between bacteria
29
Staph aureus
Virulence factors - Pore-forming toxins (PVL causes hemorrhagic pneumonia), Proteases (exofoliatin - attacks joints between desmosomes in the skin), Toxic shock syndrome toxin (stimulates cytokine release), Protein A (surface protein)
30
Staph aureus associated conditions
Wound infections Abscesses Septicaemia
31
Coagulase negative staphylococci
S epidermis - infections in catheters (opportunistic), main virulence factor is ability to form persistent biofilms) S saprophyticus - Acute cystitis (urease - kidney stones)
32
Strep pyogenes
Chains of gram positive cocci B haem Penicillin sensitive (treatment)
33
Haemolysis
Strep Alpha haem - partial greening, S intermedius, Beta haem - S pyogenes, clear zone Non haem - no lysis
34
Streptoccoci classification
Hemolysis Lancefield typing Biochemical properties
35
Sero-grouping (Lancefield grouping)
Method of grouping catalase negative, coagulase negative bacteria based on
36
Sero-grouping
Carb cell surface antigens - Lacefield A-H and K-V Antiserum to each group added to a suspension of bacteria - clumping indicates recognition Group A - strep pyogenes Group B - strep agalactiae
37
Strep pyogenes infections
``` Wound infections lead to cellulitis Tonsillitis and pharyngitis Otitis media Impetigo Scarlet fever Compllications of strep pyo infection - rheumatic fever, glomerulonephritis (both inflammatory) Anti-SLO titre test ```
38
S pyogenes virulence factors
Capsule - hyaluronic acid (protection) M protein - surface protein (encourages complement degradation) Exported factors - streptokinase (breaks down clots) Toxins - Streptolysins O and S (binds cholesterol helping to adhere to human cells)
39
Draughtsman colonies indicate infection by
S.pneuoniae
40
S pneumoniae
Normal commensal in oro-pharynx Causes - Pneumonia, meningitis, sinusitis Predisposing factors - impaired mucus trapping (viral infection)
41
S pneumoniae virulence factors
Capsule - polysaccharide (antiphagocytic) Polyvalent vaccine available Inflammatory wall constituents (peptidoglycan) Cytotoxin - pneumolysin
42
Viridans streptococci
Collective name for oral streptoccoci Oral infections such as caries and abscesses Important in infective endocarditis (S oralis) Cause deep organ abscesses (brain and liver) Most virulent are the Milleri group
43
Optochin test
Resistant | Sensitive (S pneumoniae)
44
Diphtheria treatment
Anti-toxin | Erythromycin
45
C diphtheria
Toxin - inhibit protein synthesis | Prevention - vaccination (toxoid - inactivated toxin)
46
C difficile
anaerobic gram pos
47
Important gram pos bacteria
``` S aureus S epidermidis S pyogenes S pneumoniiae Viridans streptocoocci C diphtheria ```
48
Gram positive vs negative
Gram pos - peptidoglycan wall is thicker than gram neg Gram neg - has inner and outer membrane (PL bilayer), outer part is composed of LPS (lipopolysaccharide) LPS - Lipid component is toxic (endotoxin)
49
Pathogenecity determinants
Colonisation factors - adhesins, invasins, nutrient acquisition, defence against host Toxins - secreted proteins which cause damage Protein secretion system - translocate toxins across PL bilayer
50
Proteobacteria
Enterobacteria - Rods, motile (flagella), facultatively anaerobic (both aerobic and anaerobic) Some species colonise the intestinal tract (can be good or bad)
51
3 Important enterobacteria
Shigella - not motile E coli - can use lactose as a carb source of energy, but the other 2 cannot, motile Salmonella enterica - motile
52
Enterobacteria testing
MacConkey-lactose agar Stool sample Lac positive (Lactose-fermenters produce red patches) (E.coli) Lac negative (Shigella and salmonella) Agglutination test - distinguish between salmonella and shigella
53
Cell surface antigens of gram neg bacteria
``` K antigen (exopolysaccharide capsule) H antigen (flagellum) O antigen (LPS) ```
54
E coli
Enterobacteria Commensal Most abundant facultative anaerobe in gut Flagella Infections caused are wound infections (surgical), UTIs (cystitis), catheterisation, gastroenteritis, traveller's diarrhoea, bacteraemia which can lead to sepsis syndrome, meningitis (rare)
55
E coli
``` Several pathovars (pathogenic strains) Common 'core genome' as well as blocks of genes (pathogenicity islands) which are acquired via lateral gene transfer ```
56
Shigella
Very closely related to E coli except it contains a virulence plasmid 4 species Severe bloody diarrhoea Acid-tolerant bacteria which means it has a small infective dose Person to person, contaminated water and food Entry through colonic macrophage cells (where colonic mucosa is invaded by shigella), leading to apoptotic macrophages and release of inflammatory cytokines, this results in the destruction of the gut epithelium, ulitmately bloody diarrhoea due to tissue damage
57
Shigella virulence determinant
Shiga toxin - cleaves a bond in rRNA, this inhibits protein synthesis. Complication includes kidney failure
58
Salmonella
2 species - enterica, bongori (v rare, don't need to know it) A frequent cause of food poisoning (milk, poultry, meat and eggs) Infections caused include - Gastroenteritis, enteric fever( Typhoid)
59
Salmonella
Ingestion of contaminated food/water | High infective dose required
60
Salmonella pathogenesis
``` Bacterial mediated endocytosis Induction of chemokine release Neutrophil recruitment and migration Neutrophil induced tissue injury Fluid and electrolyte loss (diarrhea) Inflammation/necrosis of gut mucosa ```
61
Vibrio cholerae
Facutative anaerobe Saline environments Most severe dirrhoeal disease - Cholera Pandemics
62
Cholera
Faecal-oral route (faecal contaminated water - poor sanitation or unndercooked shellfish) High infective dose Acid-sensitive (difficult to cross gastric barrier) Vominous watery stoolds (secretory diarrhoea) Deydration/death due to hypovolaemic shock No blood, pus or fever (not dysenteric) No invasion or damage to mucosa
63
Cholera virulence determinants
TCP pili - required for colonisation | Cholera toxin - works in same way as heat labile toxin except even more potent.
64
Pseudomonas aeruginosa
Motile Aerobe Opportunistic very difficult to treat due to multiple antibiotic resistance
65
Pseudomonas aeruginosa infections
Acute - burn/surgical wounds, UTI (catheters), neutropenic patients can become septic due to bacteremia Chronic - Cystic fibrosis patients
66
Cystic fibrosis and pseudomonas aeruginosa
thick mucus, difficult to clear, becomes home for various pathogen which can't be cleared, pseudomonas aeruginosa will not be cleared once trapped in this
67
Haemophilus influenzae
Exclusively human parasite Mostly nasopharyngeal carriage Opportunistic infections mainly in young children or adult smokers - Meningitis, bronchopneumonia, epiglottitis, bacteraemia, pneumonia Fastidious - requires lots of nutrients
68
Chocolate agar is
Heated blood agar which allows H influenzae to grow
69
H influenzae virulence determinants
Capsule - invasive strains are capsulates | LPS
70
Legionella pneumophila
Severe inflammatory pneumonia Immunocompromised patients affected Man made aquatic environments - shower heads Fastidious - charcoal agar Can infect alveolar macrophages - upregulates pro-inflam genes in alveolar macrophages
71
Bordetella pertusis
Whooping cough Person-to-person transmission (airborne) Low infective dose, highly contagious Non-specific flu-like symptoms, then followed by paroxysmal coughing
72
Hypersynthesis of cyclic AMP (cAMP) leads to
Suppression of innate immune functions (immunosuppression)
73
Neisseria
Non-flaggellated diplococci Fastidious 2 important species - N meningitidis, N gonorrhoeae Person to person contact
74
N meningitidis
Nasopharynx | Person to person (airborne)
75
N meningitidis pathogenesis
Crosses nasopharyngeal epithelium and enters blood stream Lowe level bacteraemia (asymptomatic) or septicaemia (sepsis) Meningitis - Invasion of meninges - bacteria enters CSF from blood stream after crossing BBB
76
N meningitidis - Virulence dterminants
LPS - Cytokine cascade, sepsis (DIC) | Capsule - anti-phagocytic
77
N Gonorrhoeae
2nd most common STD Person to person can be asymptomatic especially in women Urethritis and PID if infection ascends
78
N Gonorrhoeae - Virulence dterminants
LPS
79
Campylobacter
2 types - Jejuni, Coli Spiral rods Most common cause of food poisoning - undercooked poultry, unpasteurised milk Mild to severe diarrhoea often with blood
80
Helicobacter pylori
Spiral shaped | Gastritis and peptic ulcer disease
81
Bacteriodetes
Non motile Rods Found in large intestine (most abundant of all) Commensal flora Anaerobe Opportunistic - Tissue injury during surgery or perforated appendix
82
Chlamydiae
Small Non-motile Obligate intracellular parasites
83
Chlamydia life cycle
Elementry body - small, robust, non-replicative Endocytosed by a host cell Reprogrammed vacuole Differentiates into the reticulate body Replicates within vacuole Once vacuole is full it redifferentiates back into the elementary body and released
84
Chlamydia diseases
Trachoma biovar leads to irreversible blindness Genital tract biovar - most common STD, infects epithelial cells of mucous membranes of urethra and vagina, can ascend to uterus and ovaries (PID, Infertility)
85
How to prevent and control infections
Education Policy development - hand washing Surveillance - screening
86
Infection
Requires harm to be done to the individual - invasion, toxin, host response
87
Routes of transmission
Risk factors - E.g. recent return from sierra leone with fever Screening - MRSA admission screening Clinical diagnosis - Cough and cavity on CXR Lab diagnosis - Urinalysis (CPEs)
88
CPEs
Carbapenemase-producing enterobacteriaceae
89
Broadest spectrum beta-lactam antibiotics
Carbapenems (serious infections, often last resort ab)
90
How to stop transmission routes in the clinical environment
Isolation - barrier or protective ward design
91
Common skin and nasal commensal (colonisation)
Staph aureus
92
Infection prevention - Environment
Isolation Cleaning Ward design
93
Norovirus
Uncontained Vomiting and diarrhoea During winter Tends to be in children Low infective dose Difficult to clean - resistant to usual cleaning products and alcohol gel Traditional hand washing is the ideal method
94
Hand hygiene
Single most effective method of preventing cross-infection - can be hand-washing or alcohol gel
95
C Difficile
Hand washing required Transmitted via spores Spores germinate, cells multiply, C diff adheres to mucus and enterocytes, colonisation, toxin production, manifestations
96
Personal protective equipment
Gloves Apron Masks
97
Disposal of sharps
Prevent needle stick injuries
98
Virus
Infectious, obligate intracellular parasite, comprising genetic material (DNA/RNA) surrounded by a protein coat and/or membrane
99
Viral shapes
Helical Complex Icosahedral
100
Virus structure
No cell wall, organelles, only can have DNA or RNA - not both at once Not living as they do not feed or respire
101
Viral replication
Attachment to a specific receptor on the host cell (glycoproteins on the surface) Cell entry Host cell interaction and replication (using host cell machinery) Translation of viral mRNA to produce proteins Assembly of virions Release of new viral particles
102
How do viruses cause disease
Direct destruction of host cells - host cell lysis (lysis of neurons leads to paralysis in poliovirus) Modification of host cell - rotavirus causes villi of the gut to atrophy which decreases small intestine surface area, nutrients not absorbed effectively, and ultimately diarrhoea Over-reactivity of immune system - HepB (Cytotoxic T cells against hepatocytes) - Jaundice, pale stool, dark urine, RUQ pain, fever and malaise, itching Damage through cell proliferation - HPV causes cervical cancer (anti-tumour genes switched off) Evasion of host defences - Antigenic variability, cell-to-cell transport, downregulation of interferon and other host defence proteins. Herpes simplex virus (oral manifestations), Herpes zoster (chickenpox - vesicular rash (fluid filled) - reactivation will lead to shingles
103
Fungi forms
Yeast Mould Dimorphic fungi - some fungi exist as both yeasts and mould, switching between the 2 when conditions suit
104
Yeasts
Divide by budding | Less than 1% of fungi
105
Moulds
Multicellular hyphae and spores
106
Fungal diseases
``` Tinea pedis (athlete's foot) Onychomycosis (fungal nail infections) Candida spp Pneumocystis Invasive aspergillosis ```
107
Fungal disease - Diagnosis
Cultures of nail clippings/scrapings Microscopy and histology performed on cultures Serology
108
Onychomycosis - Differential diagnosis
Psoriasis Eczema Yellow nail syndrome
109
Onychomycosis - Treatment
Terbinafine | Itraconazole
110
Mucosal candidiasis
Thrush White adherent plaques on oral or genital mucosa Associated with diabetes, dentures and poorly ventilated underwear
111
Mucosal candidiasis - Treatment
Topical antifungals | Oral fluconazole
112
Mucosal candidiasis - Diagnosis
Clinical | Culture
113
Invasive aspergillosis and Galactomannan
Severely immunocompromised patients typically but also post-influenza disease Galactomannans - family of molecules found on cell wall of aspergillus
114
Invasive aspergillosis - Treatment
Amphotericin
115
Pneumocystis pneumonia
Immunocompromised patients - HIV often presenting illness
116
Pneumocystis pneumonia - Diagnosis
PCR of sputum
117
Pneumocystis pneumonia - Treatment
Co-trimoxazole
118
1,3 - B-D Glucan (1-3BDG)
Non-specific indicator for individual fungi | Released into serum during invasive infection
119
Fungi vs bacteria
Generally much more difficult to treat fungi than bacteria because they are eukaryotic
120
Fungal cell
Components not present in human cells but present in fungal cells - cell wall mannoproteins, plasma membrane contains ergosterol (human pm contains cholesterol)
121
Anti-fungals
Amphotericin and terbinafine - targets ergosterol in plasma membrane by inhibiting its synthetic pathway Echinocandins - targets cell wall mannoproteins
122
Summary of activity of Azoles
Fluconazole - Candida Itraconazole - Aspergillus Voriconazole - Invasive aspergillosis
123
Azole adverse events
Relatively safe Rare SEs Voriconazole - severe hepatitis, visual disturbances, skin maligancy (photosensitivity)
124
Azole resistance
Mutations in ERG11 gene
125
Polyenes
Pore formation in ergosterol containing membranes - fungicidal Amphotericin Toxic SEs - nephrotoxicity
126
Echinocandins
Inhibitors of 1,3-BG synthase Caspofungin Few SEs/interactions Excellent anti-candida activity
127
Protazoa classification
Amoeboids Ciliates Sporozoa Flagellates
128
Amoeboids
Caused by entamoebia histolytica many entamoebia colonise the gut in humans E histolytica causes severe dysenteric illness Faecal-oral transmission - ingestion of cysts from faecally contaminated food and water Can spread through the blood to liver, brain and lungs Treatment - Metronidazole
129
Trypanosomiasis - African
Flagellate Vector - tetse fly Fever, headaches, extreme fatigue, Diagnosis - Blood film, CSF
130
Trypanosomiasis - American
Flagellate Vector - Triatomine bug Headache, fevers, chagoma, romana's sign Later disease - cardiac manifestations
131
Leishmaniasis
Flagellate Vector - Female sand fly 3 types - cutaneous (skin), muco (oral), visceral (abdo - hepato-splenomegaly is main sign of this)
132
Giardia lambia
``` Giardiasis Diarrhoea, cramps, bloating Faecal-oral spread (travel, close-contact) Diagnosis - Stool microscopy (cysts) Treatment - Metronidazole ```
133
Trichomonas vaginalis
``` Flagellate STI Trichomoniasis Women - purulent discharge, abdo pain, dysuria Men - often asymptomatic, prostatitis Treatment - Metronidazole ```
134
Cryptosporidiosis
Contaminated food/water - ingestion of cysts Watery diarrhoea, no blood, vomiting, fever and fatigue Stool sample - Oocytes seen (acid-fast stain)
135
Taxoplasmosis
Taxoplasma gondii Ingestion of undercooked meat Taxoplasma encephalitis Retinochoroiditis
136
Trimethoprim
UTI
137
Congo
One of the highest cases of malaria
138
Thrombocytopenia
Low platelets
139
Fever after traveling tends to be
Malaria
140
Malaria
5 species | Vector - Female anopheles mosquito
141
Malaria - Liver stage (growth)
Mosquito takes blood meal and injects sporozoites Travel to liver and infect liver cells Mature into shizonts Shizonts rupture releasing merozoites into blood
142
Malaria - Blood stage (rupture)
Merozoites enters the circulation and infects RBCs Trophozoites mature into schizonts Shizonts rupture releasing more merozoites (cycles of this continue) Some differentiate into sexual stage - gametocytes Blood stage gives rise to all manifestations
143
Malaria - Vector stage
Another mosquito takes a blood meal ingesting gametocytes Mature into an oocyst which ruptures releasing sporozoites Sporozoites are injected into the host during the next blood meal
144
Malaria - Symptoms
``` Fever and chills Flue-like illness Headache Nausea Vomiting ```
145
Severe malaria
P Falciparum is responsible for most malaria related deaths Cycloadherence - Leads to cerebral malaria (haemorrhage) Rosetting Sequestration
146
Malaria - hematological changes
Anaemia Jaundice Haemaglobinuria Thrombocytopenia
147
Complicated malaria
Cerebral malaria - vascular occlusion (drowsy, raised ICP, seizures and coma) Renal failure - vascular occlusion (proteinuria, haemturia) ARDS (lungs) - hypoxia Bleeding - thrombocytopenia (DIC, bleeding, anaemia, sepsis) Shock is the ultimate result of all these
148
Diagnosis of malaria
Thick and thin blood films | 3 repeats over 24hr period
149
Malaria - Treatment
``` IV Artesunate (quinine + doxycycline) Primaquine (used to eliminate hypnozoites which may be living dormant in liver - prevention) ```
150
Sore throat
Infection so treat with antibiotic
151
Sore throat
Laryngitis - viral | Tonsilitis - viral/bacterial
152
Antimicrobials
Wider umbrella term which includes antifungals, antibacterials, antiprotazoals and antivirals
153
Antibiotic
Work by binding a target site on a bacteria | Antibiotic class - determined by binding point on bacterium
154
Penicillin
Beta-lactam | Inhibits cell wall synthesis
155
Beta lactams
Penicillins Cephalosporins Carbapenems Monobactams
156
Beta-lactams
Target peptidoglycan | Work better on gram-pos than gram-neg bacteria
157
Beta-lactams
Disrupt peptidoglycan production
158
Antibiotics - Nucleic acid synthesis
Rifampicin | Quinolones
159
Antibiotics - Protein synthesis
Aminoglycosides - gentamicin Tetracyclines - Doxycycline Macrolides - Clarithromycin (important alternative to penicillin for allergies to it)
160
Antibiotics - Folate synthesis
Trimethoprim
161
Antibiotics - function
Give time and support for the immune system to respond
162
How are bacteria pathogenic
``` Attach and enter Local spread Multiply Evade host defences Shed from body ```
163
Toxins produced by body
Exotoxin - protein production | Endotoxin - gram-neg
164
Gut bacteria symptoms
Diarrhoea
165
Bacteriostatic antibiotics
Prevent bacteria multiplying Inhibitory to growth Reduce toxin production
166
Bacteriocidal antibiotics
Agent that kills the bacteria Antibiotics that tend to inhibit cell wall synthesis Useful in infections more serious such as endocarditis and meningitis where an intervention is needed quickly
167
Minimum inhibitory concentration (MIC)
Determines how much antibiotic is needed to stop the bacteria growing Lowest MIC = best antibiotic (in theory)
168
2 major determinants of anti-bacterial effects
Concentration (one or two big doses) | Time (multiple doses)
169
Time-dependent killing
Beta-lactams
170
Conc-dependent killing
Aminoglycosides | Quinolones
171
Elimination of drugs
Liver (metabolism) | Kidney (excreted)
172
How bacteria resist antibiotics
Change antibiotic target - changes to the molecular configuration Destroy antibiotic - beta-lactam ring is hydrolysed by beta-lactamase Prevent antibiotic excess Remove antibiotic from bacteria - efflux pumps
173
Bacterial resistance to antibiotics
Intrinsic - natural resistance Acquired - spontaneous gene mutation changes cell structure and enzymes. Horizontal gene transfer (transduction - bacteriophages transfer DNA) , transformation, conjugation - plasmids containing resistance)
174
Resistant bacteria - Gram positive
MRSA - Methicillin resistant staph aureus (resistant to all beta-lactams). Treatment tends to be with glycopeptides VRE - Vancomycin-resistant enterococci
175
Resistant bacteria - Gram-negative
Beta-lactamase enzymes hydrolysing penicillins
176
Cephalosporins
Broad-spec antibiotics
177
Co-amoxiclav
Amoxicillin | Clavulanate (beta-lactamase inhibitor)
178
Gram negative bacteria - Further resistance
ESBL
179
Carbapenem-resistant Enterobacteriaceae (CRE)
Produce carbapenemases which provide resistance
180
Beta-lactams
All contain beta-lactam ring Penicillins Cephalosporins
181
Cephalosporins
Good for people with penicillin allergy
182
Gram-pos bacteria
Beta-lactams | thick cell wall
183
Cellulitis
Skin and soft tissue infection S aureus is the causative organism Flucloxacillin
184
Pharyngitis
Strep is causative Oral penicillin IV benzylpenicillin
185
Pneumonia
S pneumoniae is causative Oral amoxicillin IV benzylpenicillin
186
Glycopeptides
``` Target cell wall Vancomycin IV only Gram positive only Treat MRSA Used when there are penicillin allergies SE - Renal impairment ```
187
Gram neg
Thin cell wall
188
Gram positive vs negative bacteria
Pos - Thick cell wall | Neg - Thin cell wall
189
Antibiotic pathways
``` Cell wall synthesis inhibition Prevent protein synthesis Prevent DNA synthesis Anti-metabolites Inhibitors of membrane function ```
190
Macrolides
``` Protein synthesis inhibitors Clarithromycin and erythromycin (bioavailability is same for both Oral and IV) Target gram-positive Used in penicillin allergy Treats severe pneumonia ```
191
Lincosamides
``` Protein synthesis inhibitors Clindamycin (oral and IV) Gram positives Treats cellulitis if penicillin allergy Also treats necrotising fasciitis ```
192
Tetracyclines
Protein synthesis inhibitors Doxycycline (Oral only) Broad spec Treats cellulitis and pneumonia
193
Aminoglycosides
``` Inhibits protein synthesis Gentamicin - IV only Gram-negatives but also staphs Treat UTIs and infective endocarditis However, it is very nephrotoxic which can be irreversible ```
194
Quinolones
``` Inhibits DNA synthesis Ciprofloxacin (oral and IV) Gram negative but some gram positive UTIs and Intra-abdo infections Pencillin allergies also ```
195
Trimethoprim
Folate antagonist mainly gram negs but is broad-spec UTIs
196
Nitrofurantoin
UTIs | gram negs and pos
197
Lower UTI
Nitrofurantoin E coli Urine culture
198
Cellulitis
``` Lower limbs Unilateral Red, hot, painful, tender skin Spreading Systemic symptoms S aureus Blood cultures Oral or IV flucloxacillin Clarithromycin if pen allergy ```
199
Mycobacteria
TB
200
Ziehl-Nielson acid-fast stain
Mycobacteria High lipid content in cell wall makes mycobacteria resistant to gram stain Acid fast bacilli
201
Tuberculosis of spine
Gibbus formation
202
Fish tank granuloma
Mycobacterium marinum Fish tank granuloma Lesion on hand/arm Tend to be caused by fish bites
203
Buruli ulcer
M ulcerans | First presents as a nodule which develops into an ulcer which grows and deforms, results in done destruction
204
Leprosy
M leprae
205
Mycobacteria
Aerobic, non-spore forming, non motile bacillus Gram-pos Cell wall - high molecular weight lipids (protective coat) - survive inside macrophages Slow reproduction and slow growth - gradual onset of Slow response to treatment (6 months) disease Slow growth means takes much longer to culture in lab
206
Immunology of mycobacterial disease
Mycobacteria are phagocytosed by macrophages and traffic to a phagolysosome Antigen presentation on macrophage occurs Adaptive immunity activated with T cell-mediated cytokines such as interferon Some macrophages fuse with each other to form giant multinucleated cells (Langhans giant cells) Cytotoxic T cells infiltrate the mycobacterial lesion Central tissue may necrose and form a granuloma If this works mycobacteria shut down metabolically in order to survive (dormancy) If it fails then it results in a cavity full of mycobacteria and in the lungs this is dangerous
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Granulomata
Lesions that arise in response to trying to contain mycobacteria
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Erythema nodosum
Hypersensitivity reactions to mycobacterial antigen | Inflammatory response
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Mantoux test
Tuberculin skin test
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Immunology of tuberculoid leprosy
Tissue hypersensitivity and granulomata Tissue damage - nerves Interferon production
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Primary TB
Bacilli taken in lymphatics to hilar lymph nodes Cell mediated immune response from T cells Latent TB - no clinical disease formed Pulmonary TB - Granuloma forms around bacilli that settled in apex
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TB
Can be systemic
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Main 2 mycobacterial illness
TB | Leprosy
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HIV
Sexually transmitted Has a dormancy period Attacks the immune system High ability to mutate
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HAART
Highly active antiretroviral therapy
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HIV Phases
Acute primary infection Asymptomatic phase Early symptomatic HIV AIDS
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Markers used to monitor HIV infection
CD4 and T cell count | HIV viral load (RNA copies)
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AIDS
Acquired immune deficiency syndrome | Rapid progression in elderly and children
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AIDS-defining conditions
``` Candidiasis Pneumonia Dementia/encephalopahy TB Non-hodgkin's lymphoma Aseptic meningitis ```
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HIV presenting symptoms
``` Fever Sweats Headache Diarrhoea Hepatosplenomegaly Weight loss Lethargy ```
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Fever and rash differential diagnosis other than HIV
Syphillis
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Patient with fever, rash and non-specific symptoms - Protocol for investigation
Take sexual history HIV seroconversion illness Tell lab - check for antigen
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Shingles - Treatment
Aciclovir
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AIDS CD4 count indicator
Less than 200 units
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Early symptomatic HIV
Recurrent shingles | Candidiasis
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AIDS
PCP - Pneumonia Oesophageal candida TB Dementia
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HIV - Respiratory diseases
``` TB Pneumonia Lung cancer Emphysema/COPD Lymphoma ```
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Pneumocystis - Treatment
Treatment - Co-trimoxazole
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TB
Diagnosis - Sputum sample sent to a lab and stained under a microscope with Ziehl-Nielson stain - acid-fast bacilli All patients with TB require HIV test in UK
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Resp disease in HIV
Bacterial pneumonia TB PCP
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Cerebral toxoplasmosis
Latent HIV Space occupying lesion in the brain Treat with sulphadiazine
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HIV related neoplasms
Lymphoma - Non-hodgkin's | Kaposi's sarcoma (mostly causes skin lesions)
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Site of action of HIV drugs
Protease inhibitors | Reverse transcriptase inhibitors
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HAART
Highly active antiretroviral therapy - HIV treatment | 3 drugs
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AIDS
Many opportunistic infections and neoplasms which occur when CD4 falls below 200 units
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UNAIDS 90/90/90 goals
Global target to be achieved by 2020: 90% diagnosed 90% diagnosed on ART (antiretroviral therapy) 90% viral suppression for those on ART
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HIV
Chronic treatable condition
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HIV prevention
``` Antiretroviral treatment (Undetectable = untransmittable) Circumcision Vaccines HIV diagnosis/partner notification Behavioural - condom use Needle exchange programmes ```
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U=U
Undetectable = untransmittable
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Prep
Pre-exposure prophylaxis (pre-sex)
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Pep
Post-exposure prophylaxis (post-sex)
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Infections which need to be tested for HIV
Unexplained lymphadenopathy Unexplained oral candida Unexplained weight loss Multi-dermatomal shingles
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Rash on palms of hands and feet can be due to either
Secondary syphilis | HIV
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Gradually increasing shortness of breath and cough
Pneumocystis
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HIV screening test
Venous blood sample - 4th generation includes p24 antigen Takes 4 weeks High sensitivity and specificity Salivary antibody screening tests also available
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Retroviruses
Enveloped viruses | Have to turn their RNA into DNA
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Lentiviruses
Genus of slow viruses with a long incubation period
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HIV
An enveloped virus with glycoproteins Inside is a protein capsid which houses nucleic aid and enzymes Glycoproteins - GP41, GP120 Targets CD4 helper cells - HIV fuses to CD4 receptor and passes its contents into the CD4 cell
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HIV receptors
HIV infects cells that express CD4 The interaction between CD4 and GP120 is conserved among all primate lentiviruses The co-receptors are chemokine receptors (CCRS)
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Cell tropism - cells which become infected
CD4 T cells | Macrophages (have CD4 and CCRS receptors too)
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Immune system response to HIV
Humoral - Antibodies | Cell-mediated - CD8, CD4
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Immune system consequences of HIV
Progressive decline in number and function of CD4 T cells characterises HIV infection and leads to susceptibility to infection
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Mechanisms of CD4 T cell depletion
``` Direct cytotoxicity Activation-induced death Decreased production Redistribution Ultimate drop in the number of CD4 T cells ```
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Reservoirs of HIV replication
Genital tract CNS GI system Bone marrow
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HIV1
Retrovirus evolved from simian immunodeficiency virus in chimpanzees
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Who is at risk of HIV
``` Men who have sex with men Injecting drug users Commercial sex workers Heterosexual women Migrant workers ```
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Preventing HIV transmission
PrEP PEP Circumcision Condom
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Risk of mother to child transmission - HIV
Less than 1% with HAART intervention and no breastfeeding | 35% with no intervention
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How to stop mother to child HIV transmission
Antenatal screening | Life-long antiretroviral treatment for mother
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Helminths
Worms | Mostly resident in bowel
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Helminths - 3 groups
Nematodes (roundworms) - Intestinal Trematodes (flatworms, flukes) - Blood Cestodes (tapeworms) - Invasive or non-invasive
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Pre patent period
Interval between acquiring infection and appearance of eggs/larvae in the stool
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Intestinal nematodes
Soil-transmitted Faecal-oral spread Transmitted from human to human via eggs or larvae
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Ascariasis
Ascaris lumbricoides | Large roundworms
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Loeffler's syndrome - Symptoms and signs
Cough Fever CXR infiltrates Wheeze
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Asacariasis - Diagnosis
Stool microscopy for eggs
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Ascariasis - Treatment
Mebendazole
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Hookworm
2 species - Anycylostoma duodenale, Necator americanus | Small size
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Hookworm - Clinical features
Ground itch
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Hookworm - Diagnosis
Stool microscopy for eggs
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Hookworm - Treatment
Mebendazole
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Pinworm/Threadworm
Common in UK | Enterobius vermicularis
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Pinworm/Threadworm - Clinical features
Pruritus ani | Appendicitis
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Whipworm
Trichuris trichiura
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Whipworm - Clinical features
Bloody diarrhoea
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Strongyloidiasis
Strongyloides stercoralis
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Hyperinfection syndrome
Auto infection | Immunocompromised state
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Larva migrans
Toxocara canis/cati | Causes ocular toxocariasis (granulomatous reaction) which leads to blindness
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Cutaneous larva migrans
Itchy skin eruption due to dog hookworm
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Anisakiasis
Due to raw fish (sushi) Anisakidae Sea creature which invades fish bodies
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Tissue nematodes
Filaria | Causes elephantiasis
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Tapeworm
Taenia saginatum | Due to uncooked beef
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Neurocysticercosis
Pork tapeworm
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Schistosomiasis
Schistosoma Swimmer's itch Infection can cause bladder cancer
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Liver flukes
Invade liver by biliary tree
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Bacterial enzymes
Deconjugate compounds within enterohepatic circulation aiding reabsorption back across the intestinal wall (bilirubin, cholesterol, bile)
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If normal bowel barriers are breached by bacteria this leads to
Peritonitis
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Gastric acid
First defence against pathogens trying to colonise gut
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Disruption to normal flora by antibiotics causes
C difficile
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Diarrhoea
Main drug cause is Antibiotics
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Diarrhoea - stool charactertics
Blood, mucus, watery, fat content
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Viral diarrhoea
The commonest cause of diarrhoea is viral Rotavirus - children Norovirus - all ages Damage mucosal architecture - villi, inflamamtory exudate Watery diarrhoea
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Bacterial diarrhoea - Types
Enterotoxin mediated - Cholera, Colonise upper bowel, water diarrhoea, dehydrated v quickly, mucosal architecture remains intact Invasive - Lower colon, shigella, salmonella, damages architecture, bloody mucoid stools
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Cholera
Faeco-oral spread Watery diarrhoea, vomiting, rapid dehydration Treatment - Doxycycline, fluids
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Travellers diarrhoea
3 or more unformed stools in 24hrs | Fever, N/V, cramps, bloody stools
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Diarrhoea - Investigations
Bloods - Blood cultures | Stool tests - Microscopy, culture
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Diarrhoea - Management
Antibiotics Fluids Electrolytes (prevent arrhythmias)
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Peptic ulcer disease
``` LUQ/RUQ pain H.pylori infection Causes gastritis and ulceration N/V, indigestion Increased RF for gastric cancer Treatment - Antibiotics (Clarithromycin, amoxicillin), PPI (Omeprazole) ```
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Ascending cholangitis/biliary sepsis
Jaundice Fever RUQ pain Treat with antibiotics
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Cholecystitis vs cholangitis
Cholecystitis - Gall bladder | Cholangitis - Tract
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Liver abscess
RUQ pain, fever Aspirate sample - E coli USS/CT Antibiotics and drainage
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Enteric fever
Salmonella (typhoid) RLQ pain, fever, bradycardia, headache, myalgia, constipation or diarrhoea Diagnosis - Blood cultures Treatment - IV antibiotics (Ceftriaxone)

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