Sensitivities of clinically significant organisms to four cephalosporins, ampicillin and mecillinam

Specimens received at a district laboratory over a period of 4 months were investigated for determination of the sensitivities of common pathogens to 4 cephalosporins, ampicillin and mecillinam. A total of 1035 freshly isolated clinically significant organisms was studied. When sensitivities of all pathogens were considered, the majority were found to be resistant to ampicillin and mecillinam and sensitive to the cephalosporins. Sensitivity figures changed considerably when individual groups of organisms were considered. The great majority of urinary pathogens were sensitive to mecillinam, but not to ampicillin. This pattern was reversed when respiratory pathogens were considered. Only a few pathogens from wound swabs were sensitive to either ampicillin or mecillinam. All the cephalosporins tested showed much wider spectrum of activities. Of all antibiotics tested, only cefoxitin was active against the vast majority of Bacteroides spp. These findings are discussed in relation to the clinical uses of these antibiotics.