Smith J T, Bremner D A, Datta N
Antimicrob Agents Chemother. 1974 Oct;6(4):418-21. doi: 10.1128/AAC.6.4.418.
The ampicillin resistance of clinical isolates of Shigella sonnei is due to beta-lactamase production. Two kinds of resistance are found: low level, nontransmissible; and high level, tranmissible. The nontransmissible type of resistance results from a chromosomal mutation which increases the production of a beta-lactamase that hydrolyses cephalosporins relatively rapidly and gives cephalothin resistance. The transmissible type of resistance is due to an R factor mediating the synthesis of a different beta-lactamase that does not significantly hydrolyze cephalosporins or confer cephalothin resistance. One clinical isolate is shown to possess simultaneously both these mechanisms of ampicillin resistance.
宋内志贺菌临床分离株对氨苄西林的耐药性是由于产生β-内酰胺酶所致。发现了两种耐药类型：低水平、不可传递的；以及高水平、可传递的。不可传递型耐药是由染色体突变引起的，该突变增加了一种β-内酰胺酶的产生，这种酶能相对快速地水解头孢菌素并导致对头孢噻吩耐药。可传递型耐药是由于一种R因子介导合成了一种不同的β-内酰胺酶，这种酶不会显著水解头孢菌素或导致对头孢噻吩耐药。有一株临床分离株被证明同时具有这两种氨苄西林耐药机制。
