antibiotic by oral route with ed 50 comparable to 5r 6s 2 5r 6s 2 carbamoyloxymethyl 6 1 r hydroxyethyl 2 penem 3 carboxylic acid given subcutaneously as reported in table 2 table 2______________________________________ administration infectioncompound route i p ed sub 50 mg kg______________________________________acetoxymethyl per os per os 3 2ester compound compound s c staf aureus 1 smith______________________________________ 5r 6s 2 5r 6s 2 carbamoyloxymethyl 6 1 r hydroxyethyl 2 penem 3 caroxylic acid the acetoxymethyl ester of 5r 6s 2 carbamoyloxymethyl 6 1 r hydroxyethyl 2 penem 3 carboxylic acid is particularly valuable owing to its efficacy for various bacterial more specifically owing to the high antibacterial activity either in animals or in humans against both gram positive and gram negative bacteriathe compound of the present invention is useful in the treatment of the infections caused by said microorganisms such as respiratory tract infections for example bronchitis bronchopneumonia pleurisy hepatobiliary and abdominal infections for example septicemia urinary tract infections for example pyelonephritis cystitis obstetrical and gynecological infections for instance cervicitis endometritis ear nose and throat infections for instance otitis sinusitis parotitis the toxicity of the compounds of the invention is quite low and therefore they can be safely used in therapy the compound of the invention is useful in the treatment of bacterial infections in mammals including man it is administered orally and may bein capsule form or as tablets powders liquid solution suspensions elixirs or the like the compound may be used alone or in combination with other active ingredients it may be used in compositions including one or more pharmaceutically acceptable carriers or diluents as well as other ingredients.