The Genus Serratia

CHAPTER 3.3.11 The Genus Serratia 235
Table 7. Identification of Serratia rubidaea biotypes. a
Trait
Biotype b
B1 B2 B3
Growth on:
Histamine v − +
D-Melezitose − + +
D-Tartrate + − v
Tricarballylate − v −
Voges-Proskauer (O’Meara) + − v
Lysine decarboxylase + + −
Malonate (Leifson) + + −
a Symbols as in Table 4.
b Biotype B1 corresponds to the subspecies designated as
S. rubidaea subsp. burdigalensis; B2 to S. rubidaea subsp.
rubidaea; and B3 to S. rubidaea subsp. colindalensis.
Unpublished observations, F. Grimont and P. A. D. Grimont.
Table 8. Identification of Serratia odorifera biotypes. a
Trait
a Symbols as in Table 4.
b The type strain corresponds to biotype 1.
c Some strains were positive in 3–7 days.
Biotype
1 b 2
Growth on:
m-Erythritol − +
L-Fucose v +
D-Raffinose + −
Sucrose + −
D-Tartrate + −
Ornithine decarboxylase + −
Acid from sucrose + −
Acid from raffinose + − c
Table 9. Identification of Serratia entomophila biotypes. a
Trait
Biotype
1 b 2
Growth on:
D-Arabitol + −
L-Arabitol − +
D-Malate − v
Quinate + v
D-Xylose − +
a Symbols as in Table 4.
b The type strain corresponds to biotype 1.
Biotyping of S. marcescens is epidemiologically useful (Grimont
and Grimont, 1978b, Sifuentes-Osornio et al., 1986).
Pigmentation occurs only in five S. marcescens biotypes: A1a,
A1b, A2a, A2b, and A6. The 13 other S. marcescens biotypes
correspond to nonpigmented strains: A3a, A3b, A3c, A3d,
A4a, A4b, A5, A8a, A8b, A8c, TCT, TT, and TC. Biotypes TT
and TC are rarely found and their ecological-epidemiological
significance is unknown. Nonpigmented biotypes A3abcd
and A4ab are ubiquitous, whereas nonpigmented biotypes
A5, A8abc, and TCT seem restricted to hospitalized patients
(these biotypes can however be isolated from sewagepolluted
river water). Pigmented biotypes are ubiquitous.
Minor and Sauvageot-Pigache, 1981; Le Minor
et al., 1983; Sedlak et al., 1965; Traub, 1981, 1985;
Traub and Fukushima, 1979b; Traub and Kleber,
1977). The present system consists of 24 somatic
antigens (O1 to O24) and 26 flagellar antigens
(H1 to H26). Serotyping of S. marcescens is not
easy. Cross-reactions occur between O antigens
2 and 3 (the common antigen is referred to as
Co/2, 3); 6 and 7; 6, 12, and 14; and 12, 13, and
14 (the common antigen is referred to as Co/12,
13, 14). Some strains seem to have more than one
O-factor (e.g., O3,21). Cross-reactions between
O6 and O14 are so extensive that the epidemiological
distinction between these two
antigens (now referred to as O6/O14) was
abandoned.
The accuracy of the O-agglutination test with
boiled antigens has been questioned (Gaston et
al., 1988; Gaston and Pitt, 1989a). Immunoblotting
with electrophoresced lipopolysaccharide
(LPS) antigens showed that O-agglutining sera
often reacted with a heat-stable surface antigen
rather than with LPS. This heat-stable surface
antigen masks the expression of O-specific LPS
antigens. Gaston and Pitt (1989b) proposed a
simple dot enzyme immunoassay (dot EIA) that
could offer greater accuracy than agglutination
tests for serotype identification. Most strains
possess distinct acidic polysaccharides of microcapsular
origin. Oxley and Wilkinson (1988a)
have shown that the O13 antigen is a microcapsular,
acid polymer, rather than an integral part
of the lipopolysaccharide. No high-molecular
weight LPS corresponding to O-side chain material
was detected in O-serogroup reference strain
O11 or O13 (Gaston and Pitt, 1989a). The O6/
O14 antigen is a partially acetylated acidic
glucomannan (Brigden and Wilkinson, 1985).
Three different neutral polymers (O-side chain
polysaccharides) have been found in three O14
strains. Each of these polymers has been shown
to occur also in strains of serogroups O6, O8, or
O12. The polymer with a disaccharide repeatingunit
of D-ribose and 2-acetamido-2-deoxy-Dgalactose
present in the O12 reference strain, the
O14:H9 reference strain, and in a O13:H7 reference
strain all correspond to the Co/12,13,14
antigen shared by these strains (Brigden et al.,
1985; Brigden and Wilkinson, 1983; Oxley and
Wilkinson, 1988b).
To overcome the tediousness of measuring
flagellar agglutination, an immobilization test in
semisolid agar has been described for determination
of H antigens (Le Minor and Pigache, 1977).
The technique is facilitated by the use of pools
of nonabsorbed sera. No anti-H:9 serum is
needed in pools, as bacteria with H:9 antigen are
immobilized by anti-H:8 and anti-H:10 sera.
Once the unknown strain is immobilized by a
serum pool, corresponding individual sera are