TABLE 1.
Essential characteristics of established genetic elements responsible for erythromycin resistance in streptococci
| Element | Erythromycin resistance
|
Sizeb | Sequence accession no.c | Streptococcus or related species | Other resistance gene(s)d | Reference(s) | |
|---|---|---|---|---|---|---|---|
| Gene(s) | Phenotypea | ||||||
| Tn917 | erm(B) | iMLS, cMLS | 5,614 bp | M11180 | E. faecalise, S. pyogenes, S. pneumoniae | 13, 19, 94, 101, 102 | |
| Tn3872 | erm(B) | cMLS | 23.6 kb | AH007276, AM411624, AM411452 | S. pneumoniae, S. pyogenes, Abiotrophia defectivaf, S. agalactiae | tet(M) | 13, 70, 78, 80 |
| Tn6002 | erm(B) | cMLS | 20,880 bp | AY898750 | S. oralis, S. cristatus, S. pneumoniae, S. pyogenes | tet(M) | 13, 19, 27, 35, 108 |
| Tn6003 | erm(B)g | cMLS | 25,101 bp | AM410044 | S. pneumoniae | tet(M), aadE, sat4, aphA-3 | 27 |
| Tn1545 | erm(B)g | cMLS | 26.3 kb | X04388, X05577, X61025, X52632, AM889142, AM903082 | S. pneumoniae | tet(M), aadE, sat4, aphA-3 | 16, 17, 18, 26, 31,32, 68, 79, 103 |
| Tn2010 | erm(B), mef(E), msr(D) | cMLS | 26,390 bp | DQ426906, DQ426907, EF592165, AB426620 | S. pneumoniae | tet(M) | 35, 37 |
| Tn1116 | erm(B) | iMLS | 50 kb | AM411377 | S. pyogenes | 13 | |
| ICE 10750-RD.2 | erm(TR) | iMLS | 48.9 kb | CP000262 | S. pyogenes | SpyM4_1701, SpyM4_1702, SpyM4_1705 | 11 |
| Unnamed | erm(TR) | iMLS | 40 kb | FM162351 | S. pyogenes | orf3, orf4, orf7 | 54 |
| Tn1806 | erm(TR) | iMLS | 56 kb | EF469826 | S. pneumoniae | orf3, orf4, orf6 | 20 |
| Unnamed | erm(T) | iMLS | AY894138 | Group D streptococci | 104 | ||
| pRW35 | erm(T) | iMLS | 4,962 bp | EU192194 | S. pyogenes | 111 | |
| Tn1207.1 | mef(A), msr(D) | M | 7,244 bp | AF227520 | S. pneumoniae | 36, 89 | |
| Tn1207.3 | mef(A), msr(D) | M | 52,491 bp | AY657002 | S. pyogenes, S. agalactiae, S. dysgalactiae subsp. equisimilis | 7, 14, 42, 45, 53, 67, 88 | |
| Φ10394.4 | mef(A), msr(D) | M | 58,761 bp | AY445042 | S. pyogenes | 7, 9, 10, 14, 42 | |
| Φm46.1 | mef(A), msr(D) | M | 60 kb | AJ715499, AM492531 | S. pyogenes | tet(O) | 7, 14, 53 |
| mega | mef(E), msr(D) | M | 5,532 bp | AF274302 | S. pneumoniae | 35, 48, 109 | |
| mega variant | mef(E), msr(D) | M | 5,511 bp | AJ318993 | S. salivarius | 95 | |
| Tn2009 | mef(E), msr(D) | M | 23.5 kb | AF376746, AY466609, AY466610, AY466395 | S. pneumoniae | tet(M) | 35, 38 |
| 5216IQ complex | mef(I), msr(D) | M | 30,505 bp | AJ971089 | S. pneumoniae | catQ, tet(M) | 73 |
That is, the generally corresponding or expected phenotype. The resistance phenotype expressed by an erythromycin-resistant isolate may also be affected by factors other than the genetic element harbored, especially when an erm class gene is involved. In case of copresence of erm and mef genes carried by the same or by different genetic elements, the MLS phenotype usually overrides the M phenotype (52, 71, 106). cMLS, constitutive phenotype; iMLS, inducible phenotype; M, M phenotype (55, 63, 96).
The size of the genetic element is expressed as base pairs when it results from sequence analysis, otherwise it is expressed as kilobases.
Accession numbers refer to complete or partial sequencing of the genetic element.
Resistance genes carried on the same genetic element responsible for erythromycin resistance. Reported genes confer antibiotic resistances as follows: tet(M) and tet(O), tetracycline; aadE, streptomycin; sat4, streptothricin; aphA-3, kanamycin; SpyM4_1701 and SpyM4_1702 (ICE 10750-RD.2) or orf3 and orf4 (sequence accession no. FM162351) or orf3 and orf4 (Tn1806), tetronasin; SpyM4_1705 (ICE 10750-RD.2) or orf7 (sequence accession no. FM162351) or orf6 (Tn1806), spectinomycin; and catQ, chloramphenicol.
For some time after discovery and in early studies of Tn917, E. faecalis was regarded as a Streptococcus species (S. faecalis).
Formerly S. defectivus.
Two erm(B) genes, one lacking the stop codon.