GASEOUS ENVIRONMENT AND GROWTH OF MICROAEROPHILIC VIBRIOS

Evaluating 3 gas-delivery systems for culturing Campylobacter jejuni in a microaerophilic environment

Campylobacter spp. require a microaerophilic environment (80% N(2), 10% CO(2), 5% H(2), and 5% O(2)) for growth. Since the late 1800s, several systems for creating and maintaining specific microbial atmospheres have been developed and applied. The objective of this study was to evaluate Campylobacter jejuni growth by means of 3 commonly used gas-delivery systems for generating a microaerophilic environment: automated, gas-generating sachet, and plastic storage bag. Pure culture C. jejuni cells were suspended in Brucella broth and spread onto campy cefex agar plates. For the automated gas-delivery system, plates were positioned in a Mart anaerobic jar and flushed with a microaerophilic gas mixture using an Anoxomat Mart II system (Mart Microbiology B. V., Netherlands). For the sachet samples, plates were placed in a Mart anaerobic jar and 3 Gaspak EZ campy sachets (Becton Dickinson and Company, Franklin Lakes, NJ) were activated to induce a microaerophilic gas environment. The plates placed in plastic storage bags were flushed with a microaerophilic gas mixture from a premixed tank. For all 3 systems, plates were placed in a low-temperature incubator at 42°C for 24 h. After 24 h, plates were removed from the incubator and colonies were counted. The entire experiment was repeated 5 times. Results indicated no significant difference in colony counts among the gas-delivery systems tested, but colonies grown under the sachet-generated environment were smaller than colonies in the other 2 methods. Smaller colonies could have resulted from the type of media used or the length of time the plates were incubated. In conclusion, all 3 gas-delivery methods were able to produce similar Campylobacter growth results. Initial and long-term costs of equipment, as well as laboratory space availability, may be influential when choosing a gas-delivery method for generating a microaerophilic environment.

BIOCHEMICAL CHARACTERISTICS OF VIBRIO SPUTORUM AND RELATIONSHIP TO VIBRIO BUBULUS AND VIBRIO FETUS

Loesche, Walter J. (Forsyth Dental Center and Harvard School of Dental Medicine, Boston, Mass.), Ronald J. Gibbons, and Sigmund S. Socransky. Biochemical characteristics of Vibrio sputorum and relationship to Vibrio bubulus and Vibrio fetus. J. Bacteriol. 89:1109-1116. 1965.-Twenty-seven strains of Vibrio sputorum were isolated from human gingival debris. All strains reduced nitrate beyond nitrite, and all produced H(2)S. None produced catalase, indole, or acetylmethylcarbinol. Carbohydrates were not fermented, and acid end products or volatile neutral products could not be detected. Motility was observed infrequently, although 14-hr cultures usually had a few cells which displayed darting motility. Shadowed electron microscopic preparations demonstrated that most cells in a given culture were nonflagellated, although some cells with a single terminal or subterminal flagellum were always observed. V. sputorum was demonstrated not to be a strict anaerobe as previously described, but rather a microaerophile. Addition of nitrate to culture media markedly enhanced growth. V. sputorum was found to be closely related to the animal microaerophilic vibrios, V. bubulus and V. fetus. V. sputorum differed from V. fetus by being capable of anaerobic growth, producing H(2)S, and failing to produce catalase or to grow in 10% O(2). Antigens of V. sputorum cross-reacted in low titer with antisera to V. fetus serotypes I, II, III, and V. V. sputorum differed from V. bubulus by being inhibited by 3.5% NaCl and by qualitative differences in growth in the presence of 1% glycine and 10% O(2). These differences do not appear sufficient to recognize two distinct species, and it is proposed that both species be recognized as V. sputorum, which has priority. Strains unable to grow in 3.5% NaCl would be considered V. sputorum var. sputorum, whereas strains capable of growth in 3.5% NaCl would be V. sputorum var. bubulum.

The stability of small number of campylobacteria in four different transport media

Four different transport media (SIFF, Cary–Blair, RAPW and brucella broth with charcoal and FBP) were evaluated for their ability to support small number of campylobacteria. The best medium was SIFF, although Cary–Blair medium was almost equally efficient. It was possible to store less than 1 000 CFU (5/7 strains) for 1 week at room temperature in SIFF medium and less than 100 000 CFU (5/7 strains) for 3 days at room temperature in Cary–Blair medium. On the basis of the results of this study SIFF medium is recommended for use with samples having low campylobachter concentrations.

Comparison of CampyPak II with standard 5% oxygen and candle jars for growth of Campylobacter jejuni from human feces

To determine optimal temperature and atmospheric conditions for isolating Campylobacter jejuni from fecal specimens of humans, we studied six laboratory isolates and 19 fecal specimens that were known to contain C. jejuni. We compared incubations in 5% oxygen, the CampyPak II (BBL Microbiology Systems, Cockeysville, Md.) with 6 plates per jar (CP-6) and 12 plates per jar (CP-12), and candle jars at 37 and 42 degrees C. At both temperatures, the colony sizes for the laboratory strains were larger in the 5% O2 and the CP-6 than under the other two conditions. For the primary isolations, CP-12 failed to detect one and two campylobacters at 42 and 37 degrees C, respectively, whereas the candle jar failed to detect one at 42 degrees C and four at 37 degrees C. Colony size was again larger in the 5% O2 and the CP-6. For all four atmospheric conditions tested, colonies were significantly larger at 42 degrees C than at 37 degrees C. These studies showed that incubation at 42 degrees C in either 5% O2 or the CampyPak II with six plates per jar was optimal for primary isolation of C. jejuni from fecal specimens of humans. The candle jars incubated at 42 degrees C appeared to be satisfactory for primary isolation of C. jejuni from human feces, but incubation at 37 degrees C was not acceptable.

Comparison of atmospheres of incubation for primary isolation of Campylobacter fetus subsp. jejuni from animal specimens: 5% oxygen versus candle jar

An atmosphere with reduced oxygen tension is required for the primary isolation of Campylobacter fetus subsp. jejuni. Therefore, we compared use of the conventional atmosphere of 5% oxygen and 8% carbon dioxide with use of a candle jar (17% oxygen and 3% carbon dioxide) for primary isolation of C. fetus subsp. jejuni from 263 positive canine, cattle, and turkey fecal or cecal specimens. At an incubation temperature of 42 degrees C, the atmosphere with 5% oxygen resulted in more Campylobacter colonies per plate (P less than 0.005) and consistently larger Campylobacter colonies (P less than 0.005) than did the candle jar, whereas the growth of interfering flora was similar. Overall, 96% of the 263 specimens were positive for C. fetus subsp. jejuni with 5% oxygen, and 90% were positive with the candle jar (P less than 0.02). More striking differences in isolation rates were seen when both the temperature and the atmosphere were varied: 5% oxygen at 42 degrees C enabled recovery of 93% of the isolates from 70 positive specimens, versus 46% recovery with the candle jar at 37 degrees C. Results with 5% oxygen at 37 degrees C were intermediate. The addition of FBP supplement (0.25% each of ferrous sulfate, sodium metabisulfite, and sodium pyruvate) to Campy-BAP selective medium made no improvement over unsupplemented medium at 42 degrees C (whether in 5% oxygen or in the candle jar), but there was significant improvement over unsupplemented medium when both media were incubated at 37 degrees in the candle jar.

Effect of high oxygen tensions on the growth of selected, aerobic, gram-negative, athogenic bacteria

The in vitro effects of high O(2) tensions (P(O2)) on aerobic, enteric pathogens were examined at pressures of up to 3 atm absolute. Organisms from the genera Salmonella, Shigella, and Vibrio were usually subjected to 24-hr exposures. Tensions of 0.87, 1.87, and 2.87 atm absolute of O(2) (plus traces of CO(2) and N(2)) became progressively inhibitory for Salmonella and Shigella growth, but were bactericidal only for V. comma strains at tensions greater than 0.87 atm absolute of O(2). Growth inhibition of enteric organisms resulted from increased P(O2), rather than pressure per se, and could be mitigated nutritionally; an appropriate carbohydrate source is at least partially involved. Further studies with vibrios indicated that such mitigation was independent of medium pH. In addition, a synergistic relationship existed between O(2) and sulfisoxazole when tensions from 0.87 to 2.87 atm absolute of O(2) were maintained for 3 to 24 hr. Synergism occurred even under nutritional conditions which negated growth inhibition by O(2) alone. Bactericidal concentrations of sulfisoxazole, in the presence of increased P(O2), were reducible up to 4,000-fold. The combined procedure employed in this investigation, by use of an antimicrobial drug of known action, which also synergizes with O(2), plus nutritional studies, suggests a means for establishing a site of O(2) toxicity. These data support the concept that O(2) inhibition of growth represents a metabolic disturbance and that metabolic pathways involving p-aminobenzoic acid may be O(2)-labile. Such an approach could also guide development of antimicrobial agents as O(2) substitutes for promoting synergism.

Human vibriosis: indigenous cases in England

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