291
Legionella typing
Associatinganenvironmental isolateof
Legionella
withaclinical isolate
from a patient with legionellosis usually requires subtyping.There are 15
recognized serogroups of
L. pneumophila
, but there are also numerous
atypical strains that cannot be typed by this method (57). Lp1 may be
subtypedwith a “Joly” panel of sevenmonoclonal antibodies (MAbs) that,
depending on the pattern of reactivity, maymatch isolates with one of 12
MAb typestrains (58).StrainsofLp1 that reactwithmonoclonal antibody2
(MAb2) from the Jolypanel or itsEuropean counterpartMAb3/1 from the
Dresdenpanel are responsible for themajorityof outbreaks investigatedby
CDC in theUnited States and reciprocal authorities inEurope (31, 33, 34,
59).Thus,MAb2positivity is believed tobe a strong indicator of virulence
potential though, to date, no virulence phenotype is directly associated
with expression of the lag-1 gene required for the expression of MAb2
epitope, besides alteration of lipopolysaccharide acetylation and perhaps
slightly increasedhydrophobicity(60-62).Unfortunately, thesemonoclonal
antibodies are not available commercially and may only be supplied in
limitedquantities by thedevelopers (63).
In contrast to serological subtyping methods, the molecular method
of sequence-based typingmaybeusedonall serogroupsof
L. pneumophila
and can discriminate between thousands of distinct sequence types (STs)
basedon thesequencesof sevendifferentgene fragments (64-66).Nosingle
ST is predominantly associatedwith clinical isolates, though some STs are
more frequently associated with disease than others (31-34, 59).With a
much higher degree of discrimination than the 12MAb type strains, the
STmay be compared to a database of clinical and environmental isolates
maintained by the European Society of Clinical Microbiology Infectious
