Strains of Haemophilus influenzae type b sporadically isolated from clinical specimens are ampicillin resistant due to production of a beta-lactamase. This enzyme which inactivates ampicillin and penicillin G is not produced by ampicillin-susceptible strains. Various characteristics of beta-lactamase production and ampicillin resistance of three H. influenzae type b isolates were investigated. ...

Mechanism-based inactivators of b-lactamases are used to overcome the resistance of clinical pathogens to b-lactam antibiotics. This strategy can itself be overcome by mutations of the b-lactamase that compromise the effectiveness of their inactivation. We used PCR mutagenesis of the TEM-1 b-lactamase gene and sequenced the genes of 20 mutants that grew in the presence of ampicillin-clavulanate...

The antimicrobial resistance profiles, comprising 12 antibiotics, of 2478 isolates of Escherichia coli from the ECO.SENS Project involving women with acute uncomplicated urinary tract infection at 252 community health care centres in 17 countries were determined. Resistance to ampicillin alone (6.3%) and sulfamethoxazole alone (5.4%) were the most common 'single resistances'. Multiple resistanc...

The ampicillin resistance locus of three different ampicillin-resistant, temperature-sensitive Escherichia coli mutants was mapped between proC and purE and does not correspond to any of the known genes in this region. The mutant gene responsible for the temperature sensitivity and consequent morphological changes in each mutant strain was not located in the same 5-min region, even though the t...

The Infectious Diseases Society of America advocates trimethoprim-sulfamethoxazole (SXT) as initial therapy for females with acute uncomplicated bacterial cystitis in settings where the prevalence of SXT resistance does not exceed 10 to 20%. To determine trends in the activities of SXT, ampicillin, ciprofloxacin, and nitrofurantoin among urine isolates of Escherichia coli from female outpatient...

The Infectious Diseases Society of America advocates trimethoprim-sulfamethoxazole (SXT) as initial therapy for females with acute uncomplicated bacterial cystitis in settings where the prevalence of SXT resistance does not exceed 10 to 20%. To determine trends in the activities of SXT, ampicillin, ciprofloxacin, and nitrofurantoin among urine isolates of Escherichia coli from female outpatient...

Fifty-seven clinical isolates of enterococcus were tested for susceptibility to 10 antibiotics in a microtiter broth dilution system. Amoxicillin, ampicillin, vancomycin, and rifampin inhibited all strains at concentrations easily achievable in blood. Resistance to rifampin developed rapidly. Of the aminoglycosides, gentamicin was most active, followed in decreasing order by tobramycin, amikaci...

Enterococcus faecium has become a nosocomial pathogen of major importance, causing infections that are difficult to treat owing to its multi-drug resistance. In particular, resistance to the β-lactam antibiotic ampicillin has become ubiquitous among clinical isolates. Mutations in the low-affinity penicillin binding protein PBP5 have previously been shown to be important for ampicillin resistan...

Fourteen out of 150 (9.3%) consecutive strains of Haemophilus influenzae isolated on culture of sputum in the Bacteriology Department, Belfast City Hospital, during 1982/83 were found to be ampicillin-resistant (beta-lactamase-producing). Susceptibility testing to other antibiotics of these ampicillin-resistant strains showed that cefuroxime, cefotaxime, gentamicin, and amoxycillin with clavula...

Sixty-four ampicillin-resistant strains of Escherichia coli were studied. Six characters were examined: (i) resistance to ampicillin, cephalothin, and carbenicillin, (ii) synergy between ampicillin and cloxacillin, (iii) level of beta-lactamase activity after osmotic shock, (iv) transferability of ampicillin resistance, (v) immunological characterization of the enzyme, and (vi) determination of...