285
Legionella typing
Associating an environmental isolate of
Legionella
with a clinical 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
subtyped with a “Joly” panel of seven monoclonal antibodies (MAbs) that,
depending on the pattern of reactivity, may match isolates with one of 12
MAb type strains (58). Strains of Lp1 that react with monoclonal antibody 2
(MAb2) from the Joly panel or its European counterpart MAb3/1 from the
Dresden panel are responsible for the majority of outbreaks investigated by
CDC in the United States and reciprocal authorities in Europe (31, 33, 34,
59). Thus, MAb2 positivity is believed to be 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 increased hydrophobicity (60-62). Unfortunately, these monoclonal
antibodies are not available commercially and may only be supplied in
limited quantities by the developers (63).
In contrast to serological subtyping methods, the molecular method
of sequence-based typing may be used on all serogroups of
L. pneumophila
and can discriminate between thousands of distinct sequence types (STs)
based on the sequences of seven different gene fragments (64-66). No single
ST is predominantly associated with 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 12 MAb type strains, the
ST may be compared to a database of clinical and environmental isolates
maintained by the European Society of Clinical Microbiology Infectious
