Adaptation and growth of Serratia marcescens in contact lens disinfectant solutions containing chlorhexidine gluconate.

Serratia marcescens (11 of 12 strains) demonstrated an ability to grow in certain chlorhexidine-based disinfecting solutions recommended for rigid gas-permeable contact lenses. For a representative strain, cells that were grown in nutrient-rich medium, washed, and inoculated into disinfecting solution went into a nonrecoverable phase within 24 h. However, after 4 days, cells that had the ability to grow in the disinfectant (doubling time, g = 5.7 h) emerged. Solutions supporting growth of S. marcescens were filter sterilized. These solutions, even after removal of the cells, showed bactericidal activity against Pseudomonas aeruginosa and a biphasic survival curve when rechallenged with S. marcescens. Adaptation to chlorhexidine by S. marcescens was not observed in solutions formulated with borate ions. For chlorhexidine-adapted cells, the MIC of chlorhexidine in saline was eightfold higher than that for unadapted cells. Cells adapted to chlorhexidine showed alterations in the proteins of the outer membrane and increased adherence to polyethylene. Cells adapted to chlorhexidine persisted or grew in several other contact lens solutions with different antimicrobial agents, including benzalkonium chloride.     

Bacterial and fungal growth in total parenteral nutrition solutions

The most serious complication of prolonged intravenous infusion of hypertonic dextrose and amino acids is infection. Frequently, the etiology is fungal rather than bacterial. Previous authors have suggested that bacterial survival and growth in the solutions is suppressed by (a) high dextrose concentration, (b) high osmolality, or (c) low pH. This paper presents evidence that proposals (a) and (b) are untenable and (c) is only partly responsible. We call attention to the presence of a factor that is antibacterial but not antifungal; namely, a high concentration of glycine.     

Bacterial and fungal growth in total parenteral nutrition solutions,.

The most serious complication of prolonged intravenous infusion of hypertonic dextrose and amino acids is infection. Frequently, the etiology is fungal rather than bacterial. Previous authors have suggested that bacterial survival and growth in the solutions is suppressed by (a) high dextrose concentration, (b) high osmolality, or (c) low pH. This paper presents evidence that proposals (a) and (b) are untenable and (c) is only partly responsible. We call attention to the presence of a factor that is antibacterial but not antifungal; namely, a high concentration of glycine.     

Bacterial disinfectant resistance—a challenge for the food industry

The focus on hygiene in the food industry has resulted in an increasing use of chemical disinfection and it has been speculated that this will impose a selective pressure and contribute to the emergence of disinfectant-resistant microorganisms. The frequency of strains with a low-level resistance to quaternary ammonium compounds (QAC) is relatively high for Listeria monocytogenes (10%), Staphylococcus spp. (13%) and Pseudomonas spp. (30%) and lower for lactic acid bacteria (1.5%) and coliforms (1%) isolated from food and food processing industry. In general, bacteria isolated after disinfection are more resistant and represent a potential food safety or food spoilage problem. Adaptation to disinfectants may be accompanied by cross-resistance to related disinfectants. We have recently found a genetic linkage between resistance to QAC and antibiotics in food associated staphylococci, and there is a growing concern about cross-resistance between antibiotics and disinfectants.Disinfectant resistance can in most cases be prevented by effective cleaning and disinfection procedures. More effort should be made to avoid build-up of resistance in food production environments.     

Bacterial growth in seafoood on restaurant premises.

Operational guidelines for a chain of the newer type of seafood restaurants and take-out stores were derived from plots of bacteriological and trimethylamine changes during the preparation and storage of cod fillets, shrimp, and clams. If fish is to be defrosted at room temperature it should be washed and portioned within 14 h. Subsequent storage at 5 degrees C should not exceed 72 h and once removed from the refrigerator it should be fried within 3 h. New stores should consider improved methods of defrosting. Trimethylamine content was a more sensitive measure of quality loss than bacterial growth. Shrimp quality can be improved by emphasizing the way shells are removed because most of the contamination was external. Shrimp shelled while still frozen had the best potential keeping quality. Clam meat is handled less and is always held at 5 degrees C; but bacterial growth indicated that it should not be held on the premises for more than 3 days including the time necessary for defrosting. Batter prepared fresh daily can be feft at room temperature. Frying can obliterate poor handling procedures, but adequate cooking is essential under any conditions. Clams are a gourmet item but the practice of cooking them lightly at customer request proved inadvisable.     

Efficacy of standard disinfectant test methods for contact lens-care solutions

Two disinfection systems based on hydrogen peroxide (0.5, 1.5 and 3%) and chlorhexidine gluconate (0.004%) were challenged in suspension tests using a modification of a standard method, with inocula containing 10⁶ or 10⁸ cfu/ml of the standard organisms Serratia marcescens, Pseudomonas aeruginosa and Staphylococcus warneri. The effect of an organic load on the shapes of microbial inactivation curves was also investigated. Although there were rapid declines in viability of 1–2 log units (cfu/ml) within the first minute of challenge in all cases, declines in viability subsequently levelled out rapidly, and with hydrogen peroxide viable counts increased slightly thereafter. These increases are unexplained, but may in part be attributable to disruption of cell clumps during challenge.     

Bacterial growth on organic polymers

Mathematical models are developed describing unsteady-state bacterial growth on organic polymers that are hydrolyzed by extracellular enzymes secreted by the bacteria to yield low-molecular-weight oligomers that may be directly transported across bacterial cytoplasmic membranes and hence metabolized. Two different modes of extracellular enzyme action on the organic polymer are considered. In one case, the enzyme is exoacting yielding a transportable oligomer with each polymer bond hydrolyzed. In the other case, the enzyme is endoacting yielding a series of oligomers upon random cleavage of the polymer bonds with oligomers up to a certain chain length assumed to be transportable. These models are exploited to show under what circumstances the rate of hydrolysis by the extracellular enzyme to yield transportable oligomers influences the bacterial growth rate. It is shown that an initial lag period, an accentuated declining growth phase, and a low overall rate of bacterial growth will be some of the manifestations when the rate of hydrolysis has a strong influence.     

Bacterial growth on aminoalkylphosphonic acids

Harkness, Donald R. (University of Miami School of Medicine, Miami, Fla.). Bacterial growth on aminoalkylphosphonic acids. J. Bacteriol. 92:623-627. 1966.-Of 10 bacterial strains tested, 9 were found to be able to utilize the phosphorus of at least one of eight different aminoalkylphosphonic acids for growth, indicating that the ability to catabolize the carbon-phosphorus (C-P) bond is widespread among bacteria. Several organisms gave comparable growth rates as well as cell yields when an equimolar amount of either P(i) or 2-aminoethylphosphonic acid (2-AEP) was added to the medium. No compounds containing C-P bonds were detected in Escherichia coli B grown on 2-AEP(32)-orthophosphate. No degradation of phosphonates by cell-free extracts or suspensions of dried cells was demonstrated. The direct involvement of alkaline phosphatases in cleaving the C-P bond was excluded.     

Bacterial growth in plant tissue culture media

C. LEIFERT AND W.M. WAITES. 1992. When Murashige and Skoog's liquid plant medium was inoculated with 10 different bacterial species in the absence of plants only Bacillus subtilis showed significant growth. The numbers of Lactobacillus plantarum, Pseudomonas maltophilia, Erwinia carotovora and Staphylococcus saprophyticus decreased rapidly and were not detected at 28 d.
Bacillus subtilis, Lact. plantarum, Ps. maltophilia, Erw. carotovora and Staph. saprophyticus grew and persisted in the same medium in the presence of Delphinium plants, while only Lact. plantarum and Erw. carotovora grew and persisted in the presence of Hemerocallis plants.
Hemerocallis plants lowered the pH of media from 5.6 to about 3.9 while Delphinium plants increased it to about 5.9 within 7 d after subculturing on fresh media. The pH drop in Hemerocallis media is thought to prevent the growth and persistence of bacteria such as B. subtilis, Staph. saprophyticus and Ps. maltophilia , which were found to be more sensitive to low pH than Lact. plantarum and Erw. carotovora. Bacterial growth in the medium altered the pH, reduced the plant growth and/or resulted in plant death.