• Nalaka de Silva

Microbiology in ENT

Updated: Jun 28, 2019


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




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