The Genus Serratia

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234 F. Grimont and P.A.D. Grimont CHAPTER 3.3.11 Table 5. Identification of species in the Serratia liquefaciens complex. a Characteristic S. liquefaciens Clab a Symbols as in Table 4. b The type strain of S. proteamaculans (ATCC 19323) corresponds to biotype C1c. c The type strain of S. grimesii (ATCC 14460) corresponds to biotype C1d. The potato-like odor produced by S. odorifera, S. ficaria, and a few strains of S. rubidaea, was identified as a pyrazine (3-isopropyl-2-methoxy-5-methylpyrazine) (Gallois and Grimont, 1985). scens, 4 in S. proteamaculans, 2 in S. grimesii, 3 in S. rubidaea, 2 in S. odorifera, and 2 in S. entomophila. Characteristics of these biotypes are given in Tables 6–9. Carbon source utilization tests are major elements in the identification of these biotypes. Multipoint inoculation devices (e.g., Denley Multipoint Inoculator, Denley Instruments, Ltd., Bolney Cross, Bolney, Sussex, England), are the most useful for biotyping 20 or more strains at a time. Biotype identification is faster (1–4 days) when API strips containing carbon sources are used. Alternatively, filter paper disks impregnated with each carbon source can be deposited on an inoculated minimal agar S. proteamaculans subsp. proteamaculans subsp. quinovora S. grimesii C1c RQ b EB RB C1dc ADC Growth on: trans-Aconitate − + + − + − + Adonitol − − (+) − − − − Benzoate − − (+) v − + − m-Erythritol − − + − − − − Gentisate − − − + − − − D-Malate + − − − v (v) (v) L-Rhamnose − − − + d − − m-Tartrate + − − − d − − Arginine decarboxylase − − − − − + + Esculine hydrolyzed + + + + − + + Table 6. Identification of Serratia marcescens biotypes. a Characteristic a Symbols as in Table 4. b Growth on D-malate and meso-tartrate is correlated with growth on DL-carnitine (Grimont, unpublished observations). c Lactose-positive strains are occasionally isolated. d Nonpigmented strains are occasionally isolated. Biotype A1 A2 A6 A3 A4 a b a b a a b c d a b A5 a b c A8 (Sifuentes-Osornio and Gröschel, 1987). Differentiation between S. proteamaculans biotypes Cla and Clb is superfluous; electrophoresis of proteinases (Grimont et al., 1977a) could not discriminate between these two biotypes. Serotyping of Serratia marcescens TCT TC TT Growth on: m-Erythritol + + + + + + + + + + + − − − − − − − Trigonelline − − − + − − + − + − − + + + + + − + Quinate and/or 4-hydroxybenzoate − − − − + − − − − + − + + + + − − − 3-Hydroxybenzoate − − − − − + + − − − − − − + − − − − Benzoate + + − − − − − − − − − − − − − − − − D-Malate/m-tartrate b + − + + v − − v − + + + v − − + + − Gentisate − − + + + + + v − + + − v + v − − − Lactose − − − − − − c − − c − c − c − − c − − c + − c − c − Tetrathionate reduction + + + + + + + + + − − + + + + + + + Red pigment + d + d + + + d − − − − − − − − − − − − − The systematic inventory of somatic (O) antigens of S. marcescens began in 1957 (Davis and Woodward, 1957). Flagellar antigens (H) were described (Ewing et al., 1959) and an antigenic scheme was developed (Ewing, 1986; Ewing et al., 1959; Le Minor and Pigache, 1977, 1978; Le
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
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The Genus Serratia

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