Punched-Out Agar Petri Plates for Systematic Fixation and Embedding of Multiple Small Tissue Samples

A 5% agar solution is poured into Petri dishes, jelled, and a pattern of cylindrical holes punched out according to the number and size of tissue samples to be processed. These punched-out Petri plates withstand neutral formalin, water, benzene, and paraffin immersion at 60 C; thus providing an adaptable container for processing small tissue samples. Reduced handling of the tissues, minimized risk of loss, and easy identification of samples by means of the map-like arrangement of the holes are among the virtues of such plates. An optimal fixative-volume: tissue-weight ratio can be attained by using wells of varying diameter and depth according to the sample size.     

Pneumatic, Multiple, Simultaneous Inoculator for Plastic Trays

A device is described which consists of a bonded Plexiglas-silicone rubber plate, perforated to hold capillary pipettes in register with the wells of a plastic tray to be inoculated. Pipette contents are simultaneously discharged by positive air pressure, initiated by closing an exhaust port with the thumb.     

Method for Staining and Preserving Agar Gel Diffusion Plates

An improved method for the preservation of agar gel precipitin lines has been developed.     

Stability of Antibiotics and Chemotherapeutics in Agar Plates

The stability of chemotherapeutic agents incorporated into agar plates was studied by comparison of minimum inhibitory concentrations on fresh and stored plates and by direct bioassay of the chemotherapeutic agar plates. Plates were stored in sealed bags at 4 C. No loss of bioactivity was demonstrated after 30 days of storage in plates containing methicillin, erythromycin, cephalothin, tetracycline, chloramphenicol, kanamycin, streptomycin, polymyxin B, or nalidixic acid. Penicillin G, ampicillin, and nitrofurantoin showed statistically significant losses of activity after 4 weeks. None of the chemotherapeutics tested showed significant loss in activity after 1 week.     

Improved Automatic Inoculator for Bacterial Cultures

A simple automatic inoculator which allows the simultaneous inoculation of several cultures with identical or different inocula is described. The use of Teflon spaghetti tubing allows great flexibility in handling and placing of components. The inoculator can be adapted to handle aerobic and anaerobic bacteria.     

Use of Sealed Agar Plates for Bacterial Cultures Under Jungle Conditions

Commercially available sealed blood-agar plates have been demonstrated to retain their usefulness for as long as 3 months under jungle conditions without refrigeration.     

Modeling Surface Growth of Escherichia coli on Agar Plates

Surface growth of Escherichia coli cells on a membrane filter placed on a nutrient agar plate under various conditions was studied with a mathematical model. The surface growth of bacterial cells showed a sigmoidal curve with time on a semilogarithmic plot. To describe it, a new logistic model that we presented earlier (H.Fujikawa et al., Food Microbiol. 21:501-509, 2004) was modified. Growth curves at various constant temperatures (10 to 34°C) were successfully described with the modified model (model III). Model III gave better predictions of the rate constant of growth and the lag period than a modified Gompertz model and the Baranyi model. Using the parameter values of model III at the constant temperatures, surface growth at various temperatures was successfully predicted. Surface growth curves at various initial cell numbers were also sigmoidal and converged to the same maximum cell numbers at the stationary phase. Surface growth curves at various nutrient levels were also sigmoidal. The maximum cell number and the rate of growth were lower as the nutrient level decreased. The surface growth curve was the same as that in a liquid, except for the large curvature at the deceleration period. These curves were also well described with model III. The pattern of increase in the ATP content of cells grown on a surface was sigmoidal, similar to that for cell growth. We discovered several characteristics of the surface growth of bacterial cells under various growth conditions and examined the applicability of our model to describe these growth curves.     

Rapid Screen for Bacteria Degrading Water-Insoluble, Solid Hydrocarbons on Agar Plates

A rapid procedure was devised for detecting on solid media bacteria able to degrade water-insoluble, solid hydrocarbons such as the polycyclic aromatic hydrocarbons phenanthrene, anthracene, and biphenyl. After Alcaligenes faecalis AFK2 was inoculated on a plate containing mineral salts agar, an ethereal solution of phenanthrene (about 10%, wt/vol) was sprayed on the surface of the plate, and the plate was incubated at 30°C for 2 to 3 days. Colonies showing degradation were surrounded with clear zones on the opaque plate. A similar clear zone also was formed around colonies which had been grown on a succinate-mineral salts agar or nutrient agar, followed by spraying of the ethereal solution of phenanthrene and further incubating for 1 day. Other phenanthrene-assimilating bacteria, including Beijerinckia Bwt and Pseudomonas SPM64, also formed clear zones on phenanthrene-covered agar plates. This method was applicable to detection of bacteria able to assimilate anthracene, naphthalene, and biphenyl.     

Effect of Storage of Mueller-Hinton Agar Plates on Zone Sizes for Antimicrobial Testing

The length of time Mueller-Hinton agar plates can be stored at 4 C without affecting the size of zones of inhibition in susceptibility testing by the Bauer-Kirby method was studied. It was found that these plates can be stored for 3 weeks at 4 C without an appreciable affect on zone sizes. Storage of plates in sealed plastic bags did not alter the results significantly. The findings indicate that commercially prepared Mueller-Hinton agar plates, which may be several days old when received at the laboratory, are suitable for use in routine susceptibility tests by the Bauer-Kirby method.     

Aerosol Inoculator for Exposure of Human Volunteers

The performance of an aerosol inoculator for human volunteers is described in tests that used the PR8 strain of type A influenza virus and sodium fluorescein as a physical tracer. Virus recovery from the aerosols was approximately 1% and was unaffected by such variables as prolonged aerosolization, total airflow, relative humidity, or method of sampling. The recovery of sodium fluorescein from the aerosol was approximately 12% and was influenced by total airflow rates and relative humidity. With this apparatus, it should be possible to deliver reasonably predictable and measurable doses of respiratory viruses to human subjects. The design makes it possible to dismantle the inoculator into its component parts to facilitate portability.     

Evaluation of Agar Plates for Direct Enumeration of Campylobacter spp. from Poultry Carcass Rinses

Campy-Cefex, a modification of Campy-Cefex, modified charcoal cefoperazone deoxycholate (mCCDA), Karmali, CAMPY, and Campy-Line agars were evaluated for their efficiency to isolate and enumerate Campylobacter spp. from poultry carcass rinses. Campy-Cefex and its modification produced the best results but were statistically similar to CAMPY, mCCDA, and Karmali.     

A Simple Method for Isolation and Photography of Clostridium Botulinum Colonies from Surface Cultures on Agar Plates

Reflected light gives a very good contrast using blood agar plates in an obliquous position under a stereoscopic microscope. Thus it is possible to isolate pure colonies of Cl. botulinum in the early stage of the growth on blood agar plates.     

A Method for the Detection of Weak Lipolysis of Dairy Lactic Acid Bacteria on Double-Layered Agar Plates

A marine bacterium, strain 7-246-6, isolated from sea water was found to elaborate aerobically an extracellular enzyme specific for native collagen and gelatin. The strain was identified as Pseudomonas marinoglutinosa from the morphological and physiological characteristics, though the strain 7-246-6 slightly differs from the latter in the following points; the shape of the colony on the plate culture, the optimum growth temperature, the presence of granule by granular staining, the utilization of carbohydrates and the number of flagellum.     

Use of Hydrogen Peroxide Treatment and Crystal Violet Agar Plates for Selective Recovery of Bacteriophages from Natural Environments

Hydrogen peroxide inactivated bacteriophages and bacteria at different rates. A concentration of 0.1% hydrogen peroxide reduced the numbers of several bacteria by an average of 94% but caused an average of 25% inactivation in the numbers of bacteriophages tested. Treating natural samples with hydrogen peroxide selectively reduced the indigenous bacterial flora and permitted better visualization of plaques of lawns of Escherichia coli C-3000. In some cases indigenous gram-positive bacteria were relatively resistant to hydrogen peroxide, but their growth could be limited by incorporation of crystal violet into the bottom agar used for plaque assays. The use of hydrogen peroxide treatment and crystal violet-containing plates permitted recovery of more phages from natural samples than did other procedures, such as chloroform pretreatment or the use of selective plating agar such as EC medium.