Formaldehyde resistant bacteria

As the MIC in Table 32 prove, Dazomet has an extraordinary broad spectrum of high activity which covers bacteria including formaldehyde resistant bacteria , fungi and yeasts, indicating that the substance is a very special formaldehyde releasing compound. One finds an explanation by looking at the pattern of synthesis which is reversible that means an intermediate of neutral to alkaline hydrolysis is iV-methyl-dithiocarbamate (see Section 9.9), a known antifungal slimicide. A pH between 4 and 9 is the optimum for Dazomet. 

In addition, on the extensive use of formaldehyde releasing compounds alone problems may occur with the selection of formaldehyde resistant bacteria (Paulus, 1976). It therefore makes sense to use different types of active ingredients to increase the spectrum of activity or even better, combinations which are characterized by synergistic effects. Fungicides are especially suitable for the so-called bioresistant metal working fluids. 

Features Synergistic effective against bacteria incl. formaldehyde-resist. species, mold fungi, and yeasts Preventol D 7 [Bayer AG]... 

Methenamine mandelate is a salt of mandelic acid and methenamine and both of these possess property of urinary antiseptic. It is rapidly absorbed in gastrointestinal tract and excreted unchanged in urine, where it broken down in acidic pH (< 5) of urine and formaldehyde is released, which inhibits most of the bacteria. It is administered with sodium biphosphate, mandelic acid or ascorbic acid to keep the urinary pH below 6. Its use is restricted to chronic, resistant type of UTI. 

Methenamine (Hiprex, Mandelamine, Urex) exerts antibacterial properties in a unique fashion. In an acidic environment, this drug decomposes into formaldehyde and ammonia. Formaldehyde is bactericidal to almost all bacteria, and bacteria do not develop resistance to this toxin. This mechanism enables methenamine to be especially useful in treating urinary tract infections, because the presence of this drug in acidic urine facilitates the release of formaldehyde at the site of infection (i.e., within the urinary tract). Use of methenamine is safe, although high doses are associated with gastrointestinal upset and problems with urination (bloody urine, pain while urinating). 

Sterilization of a membrane system is also required to control bacterial growth. For cellulose acetate membranes, chlorination of the feed water is sufficient to control bacteria. Feed water to polyamide or interfacial composite membranes need not be sterile, because these membranes are usually fairly resistant to biological attack. Periodic shock disinfection using formaldehyde, peroxide or peracetic acid solutions as part of a regular cleaning schedule is usually enough to prevent biofouling. 

Mechanism of action In order to act, methenamine [meth EN a meen] must decompose at an acidic pH of 5.5 or less in the urine, thus producing formaldehyde, which is toxic to most bacteria (Figure 32.5). The reaction is slow, requiring 3 hours to reach 90% decomposition. Methenamine should not be used in patients with indwelling catheters. Bacterial resistance to formaldehyde does not develop. [Note Methenamine is frequently formulated with a weak acid such as mandelic acid, which lowers the pH of the urine thus aiding decomposition of the drug.]... 

Nearly all bacteria are sensitive to free aldehyde at concentrations of about 20 pg/mL. Urea-splitting microorganisms (e.g., Proteus spp.) tend to raise the pH of the urine and thns inhibit the release of formaldehyde. Microorganisms do not develop resistance to formaldehyde. 

Thus, at the end of 24 hours, the milk coagulates less easily than an hour after the treatment. On the contrary, if the same milk is kept at ordinary temperature, it is found that at the end of ten hours it shows no notable modifications in its resistance to rennet-action. The difference in these results comes from the fact that, in the preservation at ordinary temperature, the lactic microbes have been able to develop and the activating action of the acid formed counterbalances the increasing resistance of the pure milk with age. The proof of this hypothesis is that if the lactic bacteria are prevented from developing, either by the use of formaldehyde, of mercury bichromate, or chloride, added to the milk at the temperature of the sunounding air, or quite simply by maintaining the milk at a temperature of 58 , we see that this milk acts like that kept in the refrigerator. This observation shows the precautions necessary to cany on experiments results of which shall be comparative. 

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