LegionellaBIOL

533Lecture

14BIOL

533Lecture

14Medical

MicrobiologyHistoryBIOL

533Lecture

14American

Legion

Convention

in

1976

inPhiladelphia

hotelRespiratory

distress

and

fever200

affected34

diedHistoryBIOL

533Lecture

14Six

months

after

outbreak,

CDC

isolatedbacteria

from

post-mortum

lungtissueInoculated

lung

tissue

into

peritoneal

cavityguinea

pigsAfter

animal

became

ill,

removed

its

spleenand

injected

tissue

into

fertilized

chicken

egg(rickettsial

methodology)HistoryBIOL

533Lecture

14Organism

was

thought

to

be

unique,

givennew

genus

and

species

name:Legionella

pneumophilaEpidemiological

search

revealed

outbreak

insame

hotel

two

years

earlierCulture

problems

because

organisms:Do

not

grow

on

common

laboratorymediaDo

not

readily

stainLecture

14Microbial

Physiologyand

StructureBIOL

533Lecture

14Species

can

be

differentiated

by:DNA

homologyCell

wall

fatty

acidsBiochemical

testingImmunological

serotypingMicrobial

Physiologyand

StructureBIOL

533Lecture

14MorphologyGram—

rods

(pleomorphic

on

artificial

media)Do

not

stain

well

except

with

special

silver

stainCulture:

do

not

grow

in

ordinary

lab

media,even

though

they

are

aerobic

organismsRequire

high

concentration

of

cysteine

and

areinhibitedbysodiumionsand

aromatic

compoundsMicrobial

Physiologyand

StructureBIOL

533Lecture

14Media

developed

have:Charcoal

to

absorb

aromatic

compoundsNon-sodium

ion

bufferAntibiotics

to

suppress

other

organismsDyes

to

make

colonies

visible

on

solid

mediaLecture

14PathogenesisEncounter:

aquatic;

found

in

lakes

andstreamsLarge

numbers

in

polluted

water

around

powerstationsCan

live

in

chlorinated

drinking

waterNormally

found

in

hot

water

tanks

of

buildingsGet

into

pipes

and

multiply

in

sediment

andaccumulate

over

period

of

yearsDo

not

spread

from

person

to

personSediment

provides

shelter

as

well

as

nutrition

for

otherbacteria

that

can

supply

cysteineBIOL

533PathogenesisBIOL

533Lecture

14Entry,

spread,

and

multiplicationEntry:

inhalation

of

organismsIncubation

period:

2-10

daysInitial

host

response:

acute

inflammatoryresponse

of

aveoli

and

then

bronchioles(similar

to

pneumococcal

infection)Neutrophils

accumulate

followed

by

macrophagePathogenesisBIOL

533Lecture

14Different

from

pneumococcal

infectionOrganisms

located

inside

of

macrophageInhibit

lysosomal

fusion

and

acidification

ofphagocyteDamageBIOL

533Lecture

14Organism

possesses

several

exotoxinsProteases,

hemolysins,

and

other

cytotoxinsOne

inhibits

oxidative

killing

of

neutrophilsMay

also

damage

tissue

directlySpread

rapidly

in

lung

tissueSymptoms

resulting

from

inflammatory

disease

inlung–

Cough,

chest

pains,

abnormal

breathing

sounds,

andfeverDamageBIOL

533Lecture

14Other

target

sites:

heart,

kidney,

lymphnodes,

spleen,

liver,

and

brainNeurological

symptoms

and

diffusemetabolic

abnormalities

result

frombloodstream

invasion:

confusion,

deliriumSome

patients

have

gastrointestinalsymptoms,

including

diarrheaDisease

SyndromesBIOL

533Lecture

14In

general,

healthy

people

rarely

getdisease–

Immunosuppressed

patients

and

heavysmokerswith

a

history

of

respiratory

problemsDisease

SyndromesBIOL

533Lecture

14Pontiac

fever

(flu-like

illness)Pontiac,

Michigan

in

1968Symptoms:

fever,

chills,

muscle

aches,malaise,

headacheDevelops

over

12-hour

period,

persists

for

2-5days,

then

spontaneously

resolvesMinimal

morbidity

and

no

mortalityDisease

SyndromesBIOL

533Lecture

14Legionaire’s

diseaseMuch

more

severe,

with

high

mortality

unlesspromptly

treatedOverall

mortality

is

15-20%Symptoms

reviewed

in

Pathogenesis

sectionEpidemiologyBIOL

533Lecture

14Incidence

is

poorly

understood

becausedisease

documentation

is

difficultPneumonias

due

to

organism:

less

than

1%

togreater

than

30%Estimated

that

25,000

to

50,000

cases

occurannuallyEpidemiologyBIOL

533Lecture

14Time

of

yearSporadic

infections

throughout

yearEpidemic

infections

occur

in

late

summer

and

fallElderly

with

decreased

pulmonary

function

andcellular

immunityare

at

increased

riskLaboratory

DiagnosisBIOL

533Lecture

14MicroscopyDifficult

because

oflack

of

stainingintracellular

natureRequire

large

number

of

organisms

to

detectBest

test:

direct

fluorescent

antibodyTest

is

very

specificFalse

positives

observed

rarely

with

Pseudomonas,Bacteriodes,

and

other

organismsLaboratory

DiagnosisBIOL

533Lecture

14Culture:

buffered

charcoal

yeast

extract(BCYE)Grow

after

3-5

daysAppear

as

small

colonies

withgroundglassappearanceLaboratory

DiagnosisBIOL

533Lecture

14Detection

of

Ag

in

respiratory

secretions

ourineCan

be

detected

immunologically

or

byhybridizationExcretion

in

urine

can

occur

for

as

long

as

ayearLaboratory

DiagnosisBIOL

533Lecture

14Serology:

indirect

fluorescent

antibody

teFour-fold

or

greater

increase

in

antibody

titeResponse

can

be

delayed

as

long

as

eightweeksLaboratory

DiagnosisBIOL

533Lecture

14IdentificationDemonstration

of

typical

morphology

andgrowth

requirementsGram—