This study examined the antibiotic resistance patterns of group B streptococci (GBS) isolated from gravid women. A total of 156 vaginal and cervical isolates of GBS were examined for resistance to penicillin, ampicillin, clindamycin, cefoxitin, gentamicin, and erythromicin. No resistance to penicillin or ampicillin was found, nor was penicillinase production demonstrated. A high level of resist...

The efficacy of treatment with a combination of ampicillin, imipenem, and vancomycin was compared with that of two-drug combinations or monotherapy in a model of experimental endocarditis using a strain of Enterococcus faecium with high-level resistance to vancomycin and moderate intrinsic resistance to ampicillin and imipenem. In vitro time-kill synergy studies demonstrated bactericidal synerg...

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 r...

We questioned whether the apparent rarity of ampicillin-resistant, non-beta-lactamase-producing (NBLP) Haemophilus influenzae was due to failure of detection. We identified ampicillin-resistant and ampicillin-susceptible H. influenzae by the agar dilution technique, using 10(5)- and 10(3)-CFU inocula. We compared the disk susceptibility of 18 ampicillin-resistant NBLP strains, 13 ampicillin-res...

Over a 3-year period, 96% of systemic infections in children caused by Haemophilus influenzae were of serotype b. Of 346 invasive infections, 15 (4%) were caused by non-type b H. influenzae. The monthly prevalence of ampicillin resistance in all isolates was highly variable (0 to 63%). Ampicillin resistance in H. influenzae causing invasive disease occurred in 13% of non-type b and 21.8% of typ...

Antibiotics that are excreted into the intestinal tract promote antibiotic resistance by exerting selective pressure on the gut microbiota. Using a beagle dog model, we show that an orally administered targeted recombinant beta-lactamase enzyme eliminates the portion of parenteral ampicillin that is excreted into the small intestine, preventing ampicillin-induced changes to the fecal microbiota...

Results: 1538 isolates from respiratory specimens of 349 CF patients over 15 years were investigated. Annual prevalence increased significantly for both bacteria, being more pronounced for H. parainfluenzae. Average percentage of resistant cultures increased by 46% (H. Influenzae) and 61% (H. Parainfluenzae). For H. influenzae, resistance to ampicillin was 34.4%, co-trimoxazole 21.4%. For H. pa...

The aim of this study was to assess the impact of three ampicillin dosage regimens on ampicillin resistance among Enterobacteriaceae recovered from swine feces by use of phenotypic and genotypic approaches. Phenotypically, ampicillin resistance was determined from the percentage of resistant Enterobacteriaceae and MICs of Escherichia coli isolates. The pool of ampicillin resistance genes was al...

The genes relA and spoT of Escherichia coli are required for the production of guanosine tetraphosphate, a critical molecule for the adoption of a stringent state that minimizes harm during metabolic and environmental stress. Subinhibitory treatments of antibiotics have been shown to result in subsequent antibiotic resistance, an effect also seen after stringency is induced through amino acid s...

Step-wise intrinsic resistance to ampicillin in Neisseria gonorrhoeae was analyzed genetically by DNA-mediated transformation experiments. A first-step ampicillin-resistant (Ampr1) mutant and a second-step ampicillin-resistant (Ampr2) mutant generated during sequential selection were used in these studies. Each selection step was accompanied by an approximate twofold increase in resistance. Fou...