Ampicillin resistance

Cefuroxime (35) is effective against community-acquired pneumonia in which ampicillin-resistant Haemophilus influence is the probable etiologic agent. Cefoxitin (23) is used to treat mixed aerobic—anaerobic infections including pelvic infections, intra-abdorninal infections, and nosocomial aspiration pneumonia. Cefonicid (31), because of its long half-life has been used in a once-a-day regimen to treat a variety of mild to moderate infections including community-acquired pneumonias, urinary tract infections, and infections of the skin and soft tissue (132,215). 

Bacterial resistance to antibiotics has been recognized since the first drugs were introduced for clinical use. The sulphonamides were introduced in 1935 and approximately 10 years later 20% of clinical isolates of Neisseria gonorrhoeae had become resistant. Similar increases in sulphonamide resistance were found in streptococci, coliforms and other bacteria. Penicillin was first used in 1941, when less than 1 % of Staphylococcus aureus strains were resistant to its action. By 1947,3 8% of hospital strains had acquired resistance and currently over 90% of Staph, aureus isolates are resistant to penicillin. Increasing resistance to antibiotics is a consequence of selective pressure, but the actual incidence of resistance varies between different bacterial species. For example, ampicillin resistance inEscherichia coli, presumably under similar selective pressure as Staph, aureus with penicillin, has remained at a level of 30-40% for mai years with a slow rate of increase. Streptococcus pyogenes, another major pathogen, has remained susceptible to penicillin since its introduction, with no reports of resistance in the scientific literature. Equally, it is well recognized that certain bacteria are unaffected by specific antibiotics. In other words, these bacteria have always been antibiotic-resistant. 

Approximately 30% to 40% of H. influenzae are ampicillin resistant. For this reason, many clinicians use a third-generation cephalosporin (cefotaxime or ceftriaxone) for initial antimicrobial therapy. Once bacterial susceptibilities are available, ampicillin may be used if the isolate proves ampicillin sensitive. Cefepime and fluoroquinolones are suitable alternatives regardless of /1-lactamase activity. 

TMP-SMX is also used in the treatment of infection caused by ampicillin-resistant Shigella spp. and for antibiotic-resistant Salmonella spp.. The combination is also effective for covering the carrier state of Salmonella typhi, the agent of typhoid fever, and other Salmonella spp.. Successful treatment of traveler s diarrhea due to susceptible E. coli is another advantage of the use of this combination. The combination is not indicated in the therapy of enterohemorrhagic E. coli strains such as 0157 H7 because of the risk of developing hemolytic-uremic syndrome associated with the release of the cytotoxic enterotoxin by the drugs. 

Ampicillin-resistant influenza Bacterial meningitis early Lyme disease GU tract, gynecologic, skin, and Bone infections septicemia gonorrhea, and other gonococcal infections ... 

Clones with ampicillin resistance but without kanamycin resistance are examined with the CloneChecker System. By this antibiotic selection, the undesired vector heterodimer is removed. If both of the clones are false, additional clones are analyzed using the same protocol. When appropriate clones are obtained for almost all of the genes, they are inoculated from the ampicillin plates to prepare plasmids in a 96-well format by using the Wizard SV 96 Plasmid DNA Purification System see Note 6). 

YEP24 Plasmid E. coli, yeast Ampicillin resistance. Yeast shuttle vector... 

Hoyle, D.V., Shaw, D.J., Knight, H.I., Davison, H.C., Pearce, M.C., Fow, J.C., Gunn, G.J. and Woolhouse, M.E.J. 2004. Age-related decline in carriage of ampicillin-resistant Escherichia coli in young calves. Applied and Environmental Microbiology 70 6927-6930. 

Foreign DNA is ligated to cleaved pBR322. Where ligation is successful, the ampicillin-resistance element is disrupted. The tetracycline-resistance element remains intact. 

Cells that grow on tetracycline but not on tetracycline + ampicillin contain recombinant plasmids with disrupted ampicillin resistance, hence the foreign DNA. Cells with pBR322 without foreign DNA retain ampicillin resistance and grow on both plates. 

Figure 26-7 Genetic map of cloning plasmids pBR322 and pUC18. Abbreviations ori, origin of replication Amp1, ampicillin resistance gene Tet1, tetracycline resistance gene. Other abbreviations are for sites cleaved by specific restriction endonucleases, a few of which are defined in Table 26-2. The nucleotide sequence numbers and directions of transcription are also indicated. Reproduced by permission of Amersham Pharmacia Biotech Inc.

ANTIBIOTICS CHLORAMPHENICOL AND ANALOGUES. Chloramphenicol (1. R = N02), CnH CLNjOs, is a commercially significant antibacterial agent and its status in clinical practice has been reviewed. Although widespread use of this antibiotic declined in the United States in the 1960s because of reports of serious toxic effects, this situation changed a decade later when ampicillin-resistant Hemophilus influenzae emerged on the clinical scene. The appearance of Bacteroides species and of Streptococcus pneumoniae resistant to /1-lactam antibiotics contributed further to... 

Plasmid incompatibility is a situation where plasmids that replicate themselves in similar ways cannot coexist in the same bacterial cell because of forced competition for replication proteins and RNA. Apramycin 18 mimics the function of a small piece of RNA that dictates incompatibility with an ampicillin-resistance plasmid and triggers the eviction of those plasmids from the bacterial cells rendering them susceptible to ampicillin treatment. 

FIGURE 17.5 Bacterial plasmid vector FliTrx used for random peptide display library [10]. FliC, flagellin gene trxA, thyoredoxin PPL, PL, promoter Col El, E. coli origin of replication ampicillin, gene for ampicillin resistance. 

ImmEI—immune to colicin El, Ap —ampicillin-resistant, CmR—chloramphenicol resistance, Km —kanamycin-resistant, Tc —tetracycline-resistant. 

Figure 15.4 pBR322 plasmid vector showing antibiotic resistance genes (tetR, tetracycline resistance ampR, ampicillin resistance) and the direction of their transcription. Some restriction sites are also shown, as well as the effect of cloning a new sequence into the Hindlll site. 

---