PubMed Health⌕ Search

PubMed · 2194159

Efficient site directed in vitro mutagenesis using ampicillin selection.

Abstract

A novel plasmid vector pSELECT-1 is described which can be used for highly efficient site-directed in vitro mutagenesis. The mutagenesis method is based on the use of single-stranded DNA and two primers, one mutagenic primer and a second correction primer which corrects a defect in the ampicillin resistance gene on the vector and reverts the vector to ampicillin resistance. Using T4 DNA polymerase and T4 DNA ligase the two primers are physically linked on the template. The non-mutant DNA strand is selected against by growth in the presence of ampicillin. In tests of the vector, highly efficient (60-90%) mutagenesis was obtained.

Explore related subjects

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

M K Lewis, D V Thompson. 1990-06-25. Efficient site directed in vitro mutagenesis using ampicillin selection.. https://doi.org/10.1093/nar%2F18.12.3439

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

Risk factors associated with ampicillin-resistant infection in newborns in the era of group B streptococcal prophylaxis.

OBJECTIVES: To document the trend of ampicillin-resistant infections in newborns weighing at least 1500 g and to determine factors associated with ampicillin-resistant neonatal early-onset infection in the era of routine group B streptococcal prophylaxis. DESIGN: Case-control study. SETTING: Referral hospital with level I through level III nurseries.Patients Newborns aged 0 to 7 days with cultures positive for bacterial infection, born from January 1994 to August 2002 (n = 53). Random controls were matched to admission year and nursery level (n = 159). MAIN OUTCOME MEASURES: Trends of and factors associated with ampicillin-resistant infections. RESULTS: Trends in our institution were the same as those found in some recent reports, a decrease in group B streptococcal early-onset infections without a concomitant increase in gram-negative early-onset infections. Specifically, when stratified by birth weight, newborns weighing at least 1500 g had no increase in gram-negative pathogens in the eras both before and after group B streptococcal prophylaxis (0.8 per 1000 live births to 0.3 per 1000 live births; incidence ratio, 2.3 [95% confidence interval, 0.5-10.9]). No increase in ampicillin resistance was seen during the same 3 periods (50%, 60%, and 50%, respectively; P =.97). Independent risk factors associated with ampicillin-resistant early-onset infection were intrapartum antibiotics for a 24-hour duration or longer (odds ratio, 4.8 [95% confidence interval, 1.0-23.3]) and clinical chorioamnionitis (odds ratio, 9.2 [95% confidence interval, 2.6-32.9]). CONCLUSIONS: No increase in early-onset infections with gram-negative or ampicillin-resistant pathogens was detected. Ampicillin-resistant early-onset infection was associated with intrapartum antibiotics given for 24 hours or longer prior to delivery and with clinical chorioamnionitis. Ampicillin sodium and gentamicin sulfate remain appropriate initial antibiotic therapies for early-onset infection in newborns weighing at least 1500 g and without these risk factors.

Ampicillin Resistance↗

Evidence for transmission between humans and the environment of a nosocomial strain of Enterococcus faecium.

An ampicillin- and ciprofloxacin-resistant Enterococcus faecium (ARE) strain, named FMSE1, with a characteristic biochemical phenotype, was in a recent study found to dominate among faecal ARE isolates from patients in several Swedish hospitals. In the present study, the prevalence of this strain among 9676 enterococcal isolates from healthy children, hospital sewage, urban sewage, surface water, slaughtered animals (broilers, pigs and cattle) and pig faeces and manure was investigated. Enterococcal isolates having the same biochemical phenotype as the FMSE1 were most common in samples of hospital sewage (50%), surface water (35%), treated sewage (28%) and untreated sewage (17%), but rare in samples from healthy children (0.8%) and animals (2%). PFGE typing of FMSE1-like isolates from hospital sewage indicated that they were closely related to the nosocomial FMSE1 strain. Thus, this study indicated a possible transmission route for nosocomial E. faecium from patients in hospitals to hospital sewage and urban sewage, and further via treatment plants to surface water and possibly back to humans. This proposed route of circulation of drug-resistant enterococci might be further amplified by antibiotic usage in human medicine. In contrast, such transmission from food animals seems to play a negligible role in Sweden.

Ampicillin Resistance↗

Inhibition of ampicillin-resistant bacteria by novel mono-DNAzymes and di-DNAzyme targeted to beta-lactamase mRNA.

In view of the weakness of antibiotics and the properties of antisense drugs, we applied DNAzymes to the field of drug resistance in bacteria. Two 10-23 mono-DNAzymes (Dz1, Dz2) and a di-DNAzyme (Dz1-2) targeted to beta-lactamase mRNA were designed to determine to what degree the growth of ampicillin-resistant bacteria (TEM-1, TEM-3) was inhibited. All three DNAzymes can play a role both in vitro and in vivo. In vitro, they exhibited high catalytic efficiency (kcat/KM) of 63.5, 91.1, and 30.8 pM(-1) min(-1), respectively, under multiple-turnover conditions. In vivo, after 9 hours' incubation, the degree of inhibition of Dz1, Dz2, and Dz1-2 for TEM-1 bacteria was 27.2%, 39.6%, and 57.7%, respectively, and that for TEM-3 bacteria was 39.1%, 44%, and 62.6%, respectively. Dz1-2 showed the greatest inhibiting effect, demonstrating in vivo activity may be increased by constructing multiple-target DNAzymes. The results indicated a potential possibility for DNAzymes to act as a new type of antibacterial or a tool of gene functional analysis for prokaryocytes.

Ampicillin Resistance↗