Capnocytophaga, Legionella

Question 1

Capnocytophaga - normal habitat

Answer 1

oral cavities of humans (children- 16-61%; adults- 100%) and other vertebrates such as dogs (58% - 70%) and cats (15-57%)

Question 2

Dysgonic fermentor 2 aka

Answer 2

Capnocytophaga canimorsus

Question 3

Virulence factors of capnocytophaga

Answer 3

C MP3 BLASTS

Complement mediated lysis inhibition
motility- gliding
phospholipase A2
protease IgA
Phagocytosis inhibition
biofilm
lipopolysaccharide and lipid A modified
Aminopeptidase
Sialidase
TLR not recognised
Secretory system type 9

Question 6

Species of legionella; serotypes and serogroups

Answer 6

most important: Legionella pneumophila (Serogroups 1-6; Pontiac fever group); L. longbeachae; L.mcdadei; intracytoplasmic, nonphagosomal L. dumoffii, L. feeleii, L. jordanis

Question 7

Legionellosis comprises of what all

Answer 7

Legionnaires disease, pontiac fever, extrapulmonary focal infections

Question 8

Legionella and pontiac- how did they get the name

Answer 8

American Legion convention in philadelphia 1976

pontiac michigan outbreak

Question 9

Environmental reservoir of legionella;

how acquired

Answer 9

(can grow in 5-50 degree celsius; best 20-42) all except L.lb : water bodies - warm water, water heater, cooling towers, potable water plumbing
(exist as biofilms, extracellular, within amoeba)

L.lb: soil - potting by gardener

aerosolisation or microaspiration; no person to person or lab transmission

Question 10

Percentages in legionella

legionella in CAP worldwide
legionella in CAP india
Lp as the cause
Lp1 as the cause
Pontiac subtype
cooling towers
home water heaters
fatality rates in sporadic cases

Answer 10

1-5%

Serology- 23%, Urinary Ag 17%, PCR 6%

Worldwide- 90-95% (even in india)- astralia and NZ L.lb is 50-85%

65-90% of all LD

55-75% of all LD due to Lp

80%

5-30%

10-15%

Question 11

Media for Legionella; what it requires for growth;

Answer 11

intracellular growth- glycerol and glucose, iron

extracellular- cysteine, iron

BCYE-GPVC
fastidous
takes 3-5 days- negative by 14 days 35 degree obligate aerobe
buffered charcoal yeast extract agar with organic buffer, charcoal, yeast extfract, iron, cysteine, alpha ketoglutarate - glycine vancomycin, polymyxin, cycloheximide

Question 12

Culture of Legionella: How identify
How inoculate
Samples

Answer 12

Opal - like colonies

MALDI - not fully accurate

Catalse oxidase positive; hippurate hydrolysis positive

Direct sample; heat preatment, acid pretreatment

Sputum enough- no need Washington murray

Question 13

Virulence factors and pathogenesis of Legionella

Answer 13

biofilm or amoebal forms have more bacteria- so more chances of inf; extracellular needs relative humidity- so warmer climate

inhaled- opsonise by C3- binds to outer membrane protien; opsonin mediated coiling phagocytosis (host cell actin cytskeleton) - this dampens intracellular killing; Type 4 pili and flagellin also used to attach to macrophage

extrudes proteins through secretion system Type IVb - Dot/Icm and prevents lysosomal fusion; flagellin, LPS and peptidoglycan recognised by NLR and caspases

phagosome also recruits membranes from RER by proteins- RalF, Sid M, Sid J, Lid A, LepB- so it becomes embedded with ribosomes, so not acidified

Lp is also resistant to superoxides; replication “ replicative phase”as in stationary phase - small and flagellated motile forms “transmissive phase”- multiple and apoptosis mediated killing - spread to other macrophages

TLR5 recognises flagellin; 2 - lipoproteins and lipopeptides; 9- DNA - chemokines cytokines relased such as TNFa, il 18, 12, IFN y; (TLR 5 polymorphism- more susceptible; 4- less susceptible)—- neutrophils and NK cells come; activate macrophage and kill

Iron transporters too; Kat B

Question 14

Pathogenesis of Pontiac

Answer 14

we dont know exactly if due to toxin (4-6 hrs IP) or actual organism (median 36 hrs IP) - or it is this org or others in the aerosol

Self resolving ; very few have positive urine ag

Question 15

IP of LD

Answer 15

2-10 days; medion 4-6

Question 16

Risk factors for LD (env, host)

Answer 16

Nosocomial: tap water filled in nebuliser, humdifier, ventilator tubing, cooling tower, irrigation of wounds

Pontiac: soil handling, not washing hands after

LD:
recent travel,
well water use,
recent plumbing work,
using brown stagnated waterm old plumbing,
spas,
cooling tower,
fountains

Host risk factors: (L.lb happens in immune competent also) others non Lp- immunocompromised only; Lp- men, >50, cigarette, lung dis, transplant, cancer esp lung, alcoholism, heart dis, frenal fialure, immune suppression- tnf A inh, anti- CD52

Question 17

LD presentation- cxr, bronchoscopy, altered parameters; complications

Answer 17

atypical pneumonia- prodrome + rigors, ab pain, diarrhoae, cough , 50% sputum, headache; initial cxr normal- then acute consolidating pneumonia difficult to differentiate from strep

broncho- normal large airways

hyponatremia, hypophospatemia, raised CK, LDH, leukopenia, thrombocytopenia, DIC, myoglobinuria

pericarditis, mycocarditis, peritonitis, focal abscesses in the brain, spleen, liver, lymp node

Question 18

Pontiac fever- cf

Answer 18

non pneumonia, shorter IP, self resolving

Question 19

Culture sens and sp and sample for LD

Answer 19

all samples; GS not sensitive - pleomoprhic GNB- basic fuschin should be used and not safranine; L. mcdadei and few strains of Lp are AFB

Sputum more than enough- no need BAL if collected right; washington murray not eligible

sp for all tests 95-100 (always culture 100)

mild illness: 20% sens
sever immunocomp- 95% sens- blood positive in 10 % of sevevere

may be positive for days after treatment

Question 20

Diagnsotic modalitis of LD ; what to use for other sp

Answer 20

Culture; IF- DFA - 20-50% sensitivity
U. Ag- 65-95% sens- Pontiac fever 95- Lp1 is 60; Other l- <5% sens; positive from 3 days of onset of illness to 1 year- cant rule out

Antibody- need paired- 20-70%

PCR- 70-95% sens- we use ssr A gene

Culture and PCR

Question 21

Legionella Rx

Answer 21

Mild- azithro or fluroquinolones or tetra
Moderate to severe/immunocom; Longer duration; Azithro, levo best

Question 22

Resistance in legionella

Answer 22

Tet(56); erythromycin acquired resistance, low level quinolone heteroresistance

AG, Beta lactams- all dont work

Follwoup by clinical imp[rovemnet; radiological flare up common- takes upto 4 monthss to clear

Question 23

prevention of legionella

Answer 23

water bodies- monochloramine or superheat and flush

chrmoprophylaxis- in outbreak, in immunocomp

environmental sampling- not routinely recommended; for hospitals- should do; if >30% positive- remediation