Capnocytophaga, Legionella Flashcards
Capnocytophaga - normal habitat
oral cavities of humans (children- 16-61%; adults- 100%) and other vertebrates such as dogs (58% - 70%) and cats (15-57%)
Dysgonic fermentor 2 aka
Capnocytophaga canimorsus
Virulence factors of capnocytophaga
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
Species of legionella; serotypes and serogroups
most important: Legionella pneumophila (Serogroups 1-6; Pontiac fever group); L. longbeachae; L.mcdadei; intracytoplasmic, nonphagosomal L. dumoffii, L. feeleii, L. jordanis
Legionellosis comprises of what all
Legionnaires disease, pontiac fever, extrapulmonary focal infections
Legionella and pontiac- how did they get the name
American Legion convention in philadelphia 1976
pontiac michigan outbreak
Environmental reservoir of legionella;
how acquired
(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
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
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%
Media for Legionella; what it requires for growth;
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
Culture of Legionella: How identify
How inoculate
Samples
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
Virulence factors and pathogenesis of Legionella
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
Pathogenesis of Pontiac
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
IP of LD
2-10 days; medion 4-6
Risk factors for LD (env, host)
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
LD presentation- cxr, bronchoscopy, altered parameters; complications
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
Pontiac fever- cf
non pneumonia, shorter IP, self resolving
Culture sens and sp and sample for LD
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
Diagnsotic modalitis of LD ; what to use for other sp
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
Legionella Rx
Mild- azithro or fluroquinolones or tetra
Moderate to severe/immunocom; Longer duration; Azithro, levo best
Resistance in legionella
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
prevention of legionella
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
