Aerobic resistance

Surprisingly, monitoring of changes in metabolism and protein expression that accompany in vitro development of metronidazole resistance in I vaginalis (Rasoloson et al. 2002) revealed that the two types of resistance belong to a common multistep process, with aerobic resistance occurring at its earliest stage. 

Altered ferredoxin function or an insufficient amount of ferredoxin caused by defective transcription has been proposed to participate in mechanisms of aerobic resistance in I vaginalis (Yarlett et al. 1986b Quon et al. 1992). Down-regulated transcription of one of the two genes for ferredoxin was also reported in laboratory-induced metronidazole-resistant E. histolytica (Wassmann et al. 

Of the two types of resistance identified, aerobic resistance is of clinical importance as most clinical isolates from treatment-refractory patients show resistance of this type. However, findings regarding the stepwise development of resistance, and continuity of resistance development from the aerobic to the anaerobic type, point to the possibility that I vaginalis strains at the early stage of anaerobic resistance could also appear in the field. In fact, some isolates reported from Upcroft s laboratory (Dunne al. 2004) and occasional isolates from surveys (e.g., Lossick et al. 1987) displaying high aerobic MLC... 

Tachezy J, Kulda J, Tomkovd E (1993) Aerobic resistance of Trichomonas vaginalis to metronidazole induced in vitro. Parasitology 106 31-37... 

Saunders, M.P., Patterson, A.V., Chinje, E.C., Harris, A.L., and Stratford, I.J. (2000). NADPH cytochrome c (P450) reductase activates tirapazamine (SR4233) to restore hypoxic and oxic cytotoxicity in an aerobic resistant derivative of the A549 lung cancer cell line. Br. J. Cancer S2, 651-656. 

Aerobic, Anaerobic, and Combined Systems. The vast majority of in situ bioremediations ate conducted under aerobic conditions because most organics can be degraded aerobically and more rapidly than under anaerobic conditions. Some synthetic chemicals are highly resistant to aerobic biodegradation, such as highly oxidized, chlorinated hydrocarbons and polynuclear aromatic hydrocarbons (PAHs). Examples of such compounds are tetrachloroethylene, TCE, benzo(a)pyrene [50-32-8] PCBs, and pesticides. 

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). 

Although the possibility of bioremediation of sites contaminated with nitrotoluene waste is clearly possible, important issues should be clearly appreciated. These include (a) additional carbon sources may be necessary to accomplish partial or complete reduction of nitro groups, (b) under aerobic conditions, dimeric azo compounds may be formed as terminal metabolites, and (c) aromatic amines may be incorporated into humic material by covalent bonding and thereby resist further degradation. 

Tetrachoroethylene (perchloroethylene, PCE) is the only chlorinated ethene that resists aerobic biodegradation. This compound can be dechlorinated to less- or nonchlorinated ethenes only under anaerobic conditions. This process, known as reductive dehalogenation, was initially thought to be a co-metabolic activity. Recently, however, it was shown that some bacteria species can use PCE as terminal electron acceptor in their basic metabolism i.e., they couple their growth with the reductive dechlorination of PCE.35 Reductive dehalogenation is a promising method for the remediation of PCE-contaminated sites, provided that the process is well controlled to prevent the buildup of even more toxic intermediates, such as the vinyl chloride, a proven carcinogen. 

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