General Outline
Best to think of Microbiology and treatment as follows. First, know the main groups of bacteria with their virulence factors and features. Then understand the mechanism of action of Antibiotics. Marry the 2 to understand which bacteria is countered with what antibiotic.
1) Bacteria in ENT
a) G stein and Features
b) Main to know Types and subtypes of importance
c) Virulence factors and what ENT manifestations do they cause.
2) Main types of antibiotics
a) cell wall inhibitors
b) stops protein synthesis,
c) nucleic acid
d) metabolism
3) Then what antibiotic to use for what (combine 1 and 2)
I BACTERIA IN ENT
OUTLINE
G+ves :
Streps and Staphs
G -ves :
HI, Moraxella C
Obligate Aerobes:
Pseudomonas
Obligate Anaerobes :
Bacteriodes, petostrep, Clostridium types, Fusobacterium
Without a capsule-:
Mycobacteria
SPECIFIC BACTERIA IN MORE DETAIL
Streps
Features G+ve diplococcus-or chains , facultative anaerobe
Types: 2 maintypes on haemolysis
1)Alpha H is Strep Pneumoniae
Causes - Pneumonia, Acute Sinusitis, AOM/ mastoiditis, meningitis
2) beta Haemolytic (groups A-F)
Group A is the most common Strep Pyogenes
Has exotoxins, supra AG can cause toxic shock (shock in the absence of culture)
Causes: Tonsillitis, Erysepelus, Impetigo, Neck Fasciitis, parotitis-lymph adenitis Mastoiditis also RF and post step GN
Staphylococcus
G+ve cocci in clumps, facultative anaerobe
2 main types: Coagulase - Promotes activation of thrombin
Cogulase - ve are usually commensals as Staph Epi (commensal)
Cogulalase +ve are pathogenic mostly Staph Aureus
causes: Skin infections ie cellulitis, furuncle, Otitis externa
Sinus: chronic sinusitis
Middle Ear: CSOM, Mastoiditis
Parotitis, lymph adentitis
Toxic Shock Sy
Haemophilus influenzae
G-ve coco bacillus, facultative anaerobe, produces B lactamase
Can be Typable or Non
Typable: most important is HI B
Causes Epiglottis in kids rare now
Non Typable
AOM/mastoiditis, Sinus, URTI,
Moraxella catarrhalis
Gram negative diplococcus which is a common respiratory pathogen in humans
Nasopharyngeal colonisation in 1-5% of adults, 30-100% of infants
Clinical manifestations
Otitis media
Lower respiratory tract infections
COPD, elderly, nosocomial
Sinusitis
Anaerobes
Some of these are +ve some -ve main importance is that they are anaerobic. This will help determine the choice of antibiotic
ie Pep Strep is G+ve ve anaerobe: can cause tonsillitis, dental infections
i.e. Fusobacterium NF: G-ve bacilli (AGNB) Deep neck infections with JV thrombosis, Parotitis, CSOM, mastoiditis
Aerobic
Pseudomonas
Motile gram negative aerobic bacillus which is ubiquitous in the environment and an opportunistic pathogen
CSOM, OE, Mastoiditis, Skull base OM
II ANTIBIOTICS
Consider Antibiotics- 4 main types
A) Acts on the cell wall
B) Acts on Protein synthesis
C) Acts on the nuclear nucleic acid synthesis
D) affects metabolism
A On cell wall (beta lactums and Non beta lactums)
OUTLINE
Beta lactums:
penicillins (Penicillin G, Amoxyl, Flucox)
Cefs. (1st, 2nd, 3rd)
cabapenems
and Monobactums
Non beta lactums:
Vancomycin
MORE IN DETAIL
penicillin G: for most streps, not staph, some good anaerobic activity
Amoxyl: Variable for strep , not staph, HI and anaerobes (better 90 mg /kg per day) (not for staph). All of this is increased with clay acid.
Flucox (good for staph, not for strep anaerobes)
Tazocillin: broad inc Pseudomonas
Cephs: 1st gen ceph +ves low anaerobes , 2n both +ves and -ves and some anaerobes, 3rd mostly -ves, 4th Gen alls and inc pusedomaonas
penums broad spectrum G+ves, -ves, anaerobes and pseudomonas
B Protein synthesis
Tetracyclines,
Macrolides,
Aminoglycosides,
Clinidamycin
C DNA synthesis ie Quinolones
mostly Cipro
good for strep, staph, HI and pseudomonas, G-ve No anaerobic cover
III CLINICAL CASES
A Pharyngo-tonsilitis
Streps, N gono, N mengid,
1st line -PO penicillin, IV ceph
less likely
Corynebact dip, anaerobes
(GABHS-
If recurrence after penicillin consider shielding by beta lactamase producers and try amox/clav)
Clinical Q2
Quinsy
As Above
Penicillin still 1st line and has sufficient anaerobic cover as well
Clinica Q 3
Deep neck abscess
Mostly anaerobes, Group A Strep,
staph, Fusobacterium
Must give broad spectrum until sensitivity, hence pipera/tazo, Imipenem is reaosnable.
Alternately Cef and Met (combination)
Parotitis/ lymph adenitis
SA, GABHS, G-ve bacilli, Anaerobes Amoxyl/Clav, 1st Gen Ceph/met
Clinda/fluroquinolone,
Acute OM
S pneu, Hi, M cat - High dose amoxl po
(If no response Augmentin rarely needed)
Acute, Chronic Mastoiditis
S. pneu, S pyo, S. aureus, HI, Pseudo
Enterobacter, AGNB, Peptostrep
Augmentin, if Pseudo: Pip/tazo, Imipenem
CSOM
Pseudo, S. aureus, AGNB, Peptostrep -Augmentin, clinda,
Acute Sinusitis
S pneu, H. i, M cat, S pyo, S. aureus -
1st line Augmentin,
Moxifloxacin
2nd gen ceph, clinda, doxy, macro
Erysepelus
Group A is the most common Strep Pyogenes
Has exotoxins, supra AG can cause toxic shock (shock in the absence of culture)
Treatment: Penicillin (+/- Flucox)
Nasal Furuncle
Staph
Flucox, 1st Gen Ceph if allergic Clindamycin
Other Cases....
Cervical lymph adenitis
Mostly viral, SA, GABHS,
-Augmentin, Clindamycin
Dental origin serious infection
Anaerobes, Fusobacteria, Treponemes
Penicillin +Metronidazole or Amox/clav
if allergic: clindamycin
Descending Mediastinitis
Polymicrobial with Anaerobes esp F. necrophorum
meropenem or cephalosporin + metronidazole