Petrella S, Clermont D, Casin I, Jarlier V, Sougakoff W
Laboratoire de Recherche Moléculaire sur les Antibiotiques, Faculté de Médecine Pitié-Salpêtrière, Université Pierre et Marie Curie, Paris, France.
Antimicrob Agents Chemother. 2001 Aug;45(8):2287-98. doi: 10.1128/AAC.45.8.2287-2298.2001.
Citrobacter sedlakii 2596, a clinical strain resistant to aminopenicillins, carboxypenicillins, and early cephalosporins such as cephalothin, but remaining susceptible to acylureidopenicillins, carbapenems, and later cephalosporins such as cefotaxime, was isolated from the bile of a patient treated with beta-lactam and quinolone antibiotics. The isolate produced an inducible class A beta-lactamase of pI 8.6, named Sed-1, which was purified. Characterized by a molecular mass of 30 kDa, Sed-1 preferentially hydrolyzed benzylpenicillin, cephalothin, and cloxacillin. The corresponding gene, bla(Sed-1), was cloned and sequenced. Its deduced amino acid sequence shared more than 60% identity with the chromosome-encoded beta-lactamases from Citrobacter koseri (formerly C. diversus) (84%), Klebsiella oxytoca (74%), Serratia fonticola (67%), and Proteus vulgaris (63%) and 71% identity with the plasmid-mediated enzyme MEN-1. A gene coding for a LysR transcriptional regulator was found upstream from bla(Sed-1). This regulator, named SedR, displayed 90% identity with the AmpR sequence of the chromosomal beta-lactamase from C. koseri and 63 and 50% identity with the AmpR sequences of P. vulgaris and Enterobacter cloacae, respectively. By using DNA-DNA hybridization, a bla(Sed-1)-like gene was identified in two reference strains, C. sedlakii (CIP-105037) and Citrobacter rodentium (CIP-104675), but not in the 18 strains of C. koseri studied. Two DNA fragments were amplified and sequenced from the reference strains of C. sedlakii CIP-105037 and C. rodentium CIP-104675 using two primers specific for bla(Sed-1). They shared 98 and 80% identity with bla(Sed-1), respectively, confirming the diversity of the chromosomally encoded class A beta-lactamases found in Citrobacter.
塞德拉克柠檬酸杆菌2596是从一名接受β-内酰胺类和喹诺酮类抗生素治疗的患者胆汁中分离出的临床菌株，对氨基青霉素、羧基青霉素以及早期头孢菌素（如头孢噻吩）耐药，但对酰脲基青霉素、碳青霉烯类以及后期头孢菌素（如头孢噻肟）敏感。该分离株产生了一种诱导型A类β-内酰胺酶，其pI为8.6，命名为Sed-1，并进行了纯化。Sed-1的分子量为30 kDa，优先水解苄青霉素、头孢噻吩和氯唑西林。克隆并测定了相应基因bla(Sed-1)的序列。其推导的氨基酸序列与科氏柠檬酸杆菌（原奇异柠檬酸杆菌）（84%）、产酸克雷伯菌（74%）、弗氏沙雷菌（67%）和普通变形杆菌（63%）的染色体编码β-内酰胺酶有60%以上的同一性，与质粒介导的酶MEN-1有71%的同一性。在bla(Sed-1)上游发现了一个编码LysR转录调节因子的基因。该调节因子命名为SedR，与科氏柠檬酸杆菌染色体β-内酰胺酶的AmpR序列有90%的同一性，与普通变形杆菌和阴沟肠杆菌的AmpR序列分别有63%和50%的同一性。通过DNA-DNA杂交，在两株参考菌株塞德拉克柠檬酸杆菌（CIP-105037）和鼠柠檬酸杆菌（CIP-104675）中鉴定出一个bla(Sed-1)样基因，但在所研究的18株科氏柠檬酸杆菌中未鉴定出。使用针对bla(Sed-1)的两种特异性引物，从塞德拉克柠檬酸杆菌CIP-105037和鼠柠檬酸杆菌CIP-104675的参考菌株中扩增并测序了两个DNA片段。它们与bla(Sed-1)分别有98%和80%的同一性，证实了柠檬酸杆菌中发现的染色体编码A类β-内酰胺酶的多样性。
