Microbial transport media

BACKGROUND OF THE INVENTION

The collecting and processing of biological samples is an important aspect in the identification of specific causative agents of disease in the diagnostic process. General considerations in collecting biological samples for examination and culture include the minimization of external contamination of the sample. Once the sample has been collected, the handling of that sample and its transport to the clinical or diagnostic laboratory are also important aspects of the diagnostic process. Nearly all samples, regardless of their type and content, preferably need to be kept hydrated. For example, most viruses are inactivated by desiccation. Further, oxidative processes and enzymatic destruction of the pathogens within the sample should be prevented. Thus, the time between sample collection and the conducting of diagnostic assays, including cell culture inoculation, can be critical to obtaining reliable results.

A variety of general and specialized transport media have been devised for the collection, delivery and delayed processing of clinical samples. See, for example, Amies (1967) Can. J. Public Health 58: 296-300; Bailey et al. (1978) "Specimen Containers and their Transport," in Diagnostic Microbiology, The C. V. Mosby Co., St. Louis, Mo., pp.29-32; U.S. Pat. No. 4,529,702. However, it is known that different organisms can have particular requirements in order to retain viability in a collection or transport medium. Certain of these organisms, many of which are clinically significant due to their pathogenicity or resistance to treatments, can present difficulties in retaining viability using a single collection or transport media. Examples of some of these organisms are discussed below.

A. Chlamydia.

Chlamydia are non-motile, Gram-negative, obligate intracellular parasites. These microbes have been identified as the causative agents of psittacosis-ornithosis, lympho-granuloma venereum, and trachoma and inclusion conjunctivitis in humans. Chlamydia trachomatis has also been implicated in a pneumonia-type syndrome in infants. Chlamydia has further been identified as the agent most frequently involved in non-specific or nongonococcal urethritis. In studies conducted in England and the United States, Chlamydia trachomatis was isolated from between 30% and 50% of patients with nonspecific urethritis. Bowie and Holmes (1977) in Infectious Diseases, 2nd Ed. (Hoeprich, Paul D., ed.), Harper & Row, Hagerstown, pp. 486-487.

Chlamydia must be grown within a cell and can be cultivated in tissue culture or in the yolk sac of an embryonated egg. Biological samples suspected of having the Chlamydia pathogen must therefore be collected in a manner so as to minimize external bacterial contamination that would hinder cell culture growth. Samples suspected of containing Chlamydia are typically stored at -70.degree. C.

B. Mycoplasmas.

Mycoplasmas, which include the genera Mycoplasma and Ureaplasma, are extremely small, free-living bacteria which lack a cell wall. Mycoplasmas are therefore resistant to conventional antimicrobials which act upon the bacterial cell wall, such as penicillin and penicillin derivatives. Organisms classified in the genus Mycoplasma do not hydrolyze urea. The organisms in the genus Ureaplasma include those that hydrolyze urea. Both genera have been implicated as agents in diseases of humans. For example, Mycoplasma pneumoniae has been reported to cause approximately 20% of the cases of primary atypical pneumonia and bronchitis. Ureaplasma have been associated with nongonococcal urethritis. Other diseases and illnesses suggested to be linked to mycoplasmal infections include rheumatoid arthritis and neurological disorders.

Specialized growth media specific for mycoplasma often include a pH indicator for the identification of acid production and various antimicrobials to destroy hardy commensals and prevent overgrowth of the sample. A transport medium that has been used satisfactorily for swab specimens of mycoplasmas comprises trypticase soy broth with 0.5% bovine albumin (Bailey, supra).

C. Viruses.

Viral pathogens are many and diverse. A common feature of most viruses, however, is that they are preferably grown and propagated in cell culture. Therefore, the collection and handling of biological specimens having, or suspected of having, virus present therein is extremely important. Such specimens must be collected to, inter alia, minimize the possibility of bacterial contamination of the cell cultures.

It is clear that the use of a previously available collection or transport medium may be optimal for one type of these organisms, i.e., Chlamydia, mycoplasmas, or viruses, but may not be optimal for use with more than one or all of these organisms. A sample suspected of having present one or more of the above pathogenic organisms previously required the collection of more than one sample. It is therefore desirable to have a single universal collection or transport medium which can sustain viability of a plurality of organisms, including those within the Chlamydia, Mycoplasma, Ureaplasma, and virus classifications. One example of a general support media for a variety of organisms in a clinical sample is Stuart's medium. See, e.g., Stuart, R. D. et al. (1954) Can. J. Publ. Health 45:73-83. Stuart's medium is a well-known buffered transport medium which includes the component sodium glycerophosphate to permit minimal multiplication and sodium thioglycollate as a reducing agent to prevent oxidation within the sample. Stuart's medium contains no nutrients. The absence of nutrients retards the growth of commensal organisms within the sample which can multiply and overgrow the less hardy pathogens. However, the absence of nutrients in Stuart's media can be detrimental to the viability of less hardy pathogens.

The presence or suspected presence of fastidious pathogens e.g., mycoplasmas, Chlamydia, or certain viruses, in a biological sample can require that special care be taken with that sample. Specialized media are known which support the viability of a variety of fastidious pathogens. However, these known media are not able to be used successfully with a wide variety of diagnostic procedures, e.g., membrane enzyme-linked immunosorbent assay (membrane ELISA) or polymerase chain reaction (PCR). A collection or transport media which is compatible with reagents or can be used as a reagent itself in diagnostic procedures performed on the sample can provide an advantage in the field of microorganism diagnostics.

Diagnostic procedures for which a universal transport medium capable of being used as, or in conjunction with, a standard reagent include membrane ELISA and polymerase chain reaction (PCR). Membrane ELISA utilizes a porous membrane to allow certain particles of a particular size to pass through the membrane enhancing the ability of reactants to come into contact, e.g., the antigen and antibody in the formation of the antigen/antibody complex. Polymerase chain reaction (PCR) is becoming a valuable technique for organism identification in the clinical and reference laboratory and can require specialized reagents for its successful application to microbial diagnostics. Saiki, R. K. (1989) in PCR Technology, Stockton Press, United Kingdom pp. 7-16. PCR is a process by which selected fragments of DNA are amplified within a sample through the action of the enzyme, DNA polymerase, so that organisms can be selectively and specifically identified even when present in extremely small amounts. In a clinical diagnostic procedure, primers to a single fragment or sequence of DNA of a target organism can be added directly to a biological sample. If the suspected pathogen is present in the sample, PCR techniques can amplify the pathogen DNA so that it is then easily detectable and its presence confirmed. PCR thus allows a sample to be tested directly for the presence of pathogens without requiring that the pathogen be isolated from the clinical sample and cultured separately before positive identification.

A single medium which can be used in the collection of a biological sample, transport of the sample, and in the diagnostic procedure, e.g. ELISA or PCR, is therefore an advantageous tool in the collecting and processing of biological samples. The advantages include not only convenience for the clinician or diagnostician, but can provide an economic benefit in the reduction of redundant sample collection and performance of a plurality of identification procedures.

BRIEF SUMMARY OF THE INVENTION

The subject invention concerns a novel, universal medium which can be useful for the collection, transport, storage or testing of biological samples suspected of having one or more of a variety of pathogens, including the fastidious pathogens Chlamydia, Mycoplasma, Ureaplasma or viral pathogens and wherein the medium is further compatible with the detection procedures and methodologies. For purposes of the subject invention, a universal medium refers to a medium in which viability for a plurality of organisms can be sustained. The subject universal transport medium comprises an aqueous balanced salt solution buffered at approximately physiological pH, at least one protein stabilizer, and particular combinations of carbohydrate and amino acid nutrient sources. The composition also comprises an antimicrobial component and an indicator of pH. A preferred embodiment of the subject invention is phosphate-free. Also, a preferred embodiment of the invention is a medium which is approximately isotonic with the cells of interest in the sample.

The subject invention also concerns an article of manufacture which provides specific directions for use with ELISA, PCR, or other identification techniques. Novel methods of use relating to these novel compositions and articles of manufacture, and kits comprising same, are also provided by the subject invention.

One object of the invention is to provide a single transport medium which can sustain the viability of the suspect organisms in a biological sample and which can be used as a reagent, or is compatible with other employed reagents, in standard detection methods. The detection methods of interest include, inter alia, standard microbial assays, enzyme-linked immunosorbent assay (ELISA), and PCR. A particular advantage of the subject invention is its successful and direct use with, or applicability to membrane ELISA and commercial PCR assays.

It is a further object of the subject invention to provide a transport medium which can support the viability of fastidious organisms and minimize the risk of contamination resulting from overgrowth by commensal organisms. In a preferred embodiment, the subject invention can comprise a composition which has a specific viscosity. In another embodiment of the subject invention, the buffer salts can include a phosphate component; however, a unique aspect of this embodiment is that only a single monophosphate component is used in an embodiment comprising phosphate.

It is still another object of the subject invention to provide a method for using the novel transport medium to collect and transport the sample whereby the medium is capable of being used with a reagent, or is compatible with other reagents, in standard detection or diagnostic procedures.

Thus, the advantages provided by the subject universal transport medium include:

1. utilization of the subject universal transport media for more than one type of test and for more than one type or organism (e.g., viruses, Chlamydia, mycoplasmas);

2. reduction of the number of rejected or inconclusive diagnostic tests due to improper transport media;

3. reduction of costs to the laboratory because providing multiple types of transport media becomes unnecessary;

4. minimization of physician education or training concerning the appropriate transport medium for particular detection or diagnostic assays;

5. allowance of conducing confirmatory tests on the same sample as the initial detection or diagnostic assay; and

6. allowance of requesting other or additional tests subsequent to the collection of the sample.

DETAILED DESCRIPTION OF THE INVENTION

The subject invention concerns microbial collection or transport media for the collection, storage and delivery of biological samples suspected of harboring fastidious microorganisms, including Chlamydia, Mycoplasma, Ureaplasma or viral pathogens. The subject transport media supports the viability of these fastidious pathogens while hindering the growth of the more hardy normal flora which can be present in the sample. Hindering growth of normal flora organisms can prevent contamination of the sample which can render it incapable of yielding positive identification of those pathogens.

More specifically, the transport medium of the subject invention comprises, in an aqueous solution: carbohydrate in the form of sugar, e.g., the complex sugar, sucrose; buffer salts, including HEPES, sodium, calcium, and magnesium salts; an amino acid nutrient source; a pH indicator; a proteinaceous stabilizing agent; and antimicrobial compositions, which can include vancomycin, gentamicin, colistin, or amphotericin B. A separate viscosity stabilizer can also be included.

The preferred composition includes as a stabilizing component, bovine serum albumin (BSA) rather than whole bovine serum, as is used in many currently available media. BSA has the added advantage that it does not contain lipoproteins which can inhibit attachment and growth of myxo- and paramyxoviruses, as can occur with whole serum. BSA can provide a further advantage over whole serum in that whole serum can potentially introduce antibodies specific for the target organism, thereby interfering with detection or diagnosis.

A preferred embodiment of the subject invention has, in an aqueous solution of about 1.0 liter (total volume) the following composition:

______________________________________ gelatin (Bloom value 40-125) 0-20.0 g sugar 65-75 g HEPES 5-7 g KCl 0.3-0.6 g L-glutamic acid 0.5-1.0 g phenol red 5-15 mg CaCl.sub.2 0.1-0.5 g MgSO.sub.4.7H.sub.2 O 0.1-0.3 g bovine serum albumin V 1.0-20.0 g vancomycin 0.01-0.05 g colistin 100,000-250,000 units amphotericin B 0.5-3.0 mg ______________________________________

The particular preferred embodiment includes the following ingredients in about 995 ml of H.sub.2 O, q.s. 1 liter: sucrose, 68.46 g; HEPES, 5.96 g; KCl, 0.4 g; L-glutamic acid, 0.72 g; phenol red, 11.0 mg; CaCl.sub.2, 0.27 g; MgSO.sub.4.7H.sub.2 O, 0.20 g; BSA, 5.0 g; gelatin, 5.0 g; vancomycin, 0.025 g; colistin, 200,000 units; amphotericin B, 1.0 mg. The pH of the medium can be adjusted with acidic or basic solutions to arrive at a final pH within physiological limits. For example, in a typical formulation for making 1.0L of Transport Medium as described above, 1N NaOH can be added until pH is adjusted to about 7.4. If the pH of the solution is alkaline (i.e., higher than physiological pH), adjustment to within the physiological pH range can be achieved by addition of an acidic component, typically hydrochloric acid (e.g., glacial HCl) as needed. Adjustment of pH is a standard and well-known procedure readily recognized in the art. This particular preferred embodiment of the subject composition is hereinafter referred to as Transport Medium A.

The medium of the subject invention has relatively low viscosity and can be used in a variety of laboratory procedures. A preferred embodiment can comprise an aqueous solution of the above components where the viscosity of the gelatin has a Bloom value less than 125. A preferred Bloom value for the gelatin is less than 100, more preferably between 40 and 100 and most preferably about 60. "Bloom value" is the standard measure of viscosity and is well known in the art. One example of a component which can provide the desired viscosity is gelatin, which is commercially available from suppliers of scientific chemicals, for example, Sigma Chemical Co., St. Louis Mo. Gelatin can also advantageously impart a cryoprotectant property to the transport medium. Gelatin further supplements the stabilizing effect of BSA for extended storage of the clinical sample and therefore can permit the reduction of BSA amounts in embodiments where gelatin is present.

In an embodiment where gelatin is absent, BSA is typically provided at about two times the normal amount. For example, an embodiment having no gelatin and about 10 grams of BSA per liter of medium is referred to herein as Transport Medium B.

Transport Medium C is identical to Transport Medium A, except that 10 .mu.g/ml of gentamicin is substituted for vancomycin and colistin. Also, a higher concentration of amphotericin B (approximately 3 .mu.g/ml) can be used. Transport Medium C is preferably used when organisms other than Mycoplasma or Ureaplasma are present or suspected of being present. The presence of gentamicin and higher concentration of amphotericin B provides an advantage of improved room temperature storage capability for the medium.

One advantage of the subject medium is its capability to preserve samples that have been frozen and thawed. Dimethyl sulfoxide (DMSO) glycerol or sorbitol, which are typically used as cryoprotectants in other media, are not used in the subject medium. These components can be toxic to living cells at certain levels or upon prolonged storage at ambient temperatures. Use of the subject transport media can maintain viability of pathogens within a sample that is frozen then thawed, without the toxic effects that can result from the presence of DMSO, glycerol, or sorbitol in the medium.

It should be understood by persons of ordinary skill in the art that the subject invention can also include equivalent components. For example, the carbohydrate nutrient source can include other complex sugars as well as simple sugars, including glucose, fructose, and the like. In addition, other L-amino acids can be used instead of L-glutamic acid.

It would also be within the capability of those with ordinary skill in the art to include other salts which function in substantially the same way as those listed in the preferred embodiment. For example, in one embodiment of the subject invention, the medium can comprise these other salts as a buffer or pH stabilizer. In an embodiment which comprises phosphate salt, sodium phosphate monobasic (NaH.sub.2 PO.sub.4) can be added to the solution at approximately 0.1 to 0.15 grams per liter, and preferably about 0.12 grams per liter. However, it is noted that phosphate salts can interfere with PCR assays and therefore the preferred embodiment of the subject medium is phosphate-free.

Vancomycin, gentamicin, amphotericin, and colistin are antimicrobial agents that inhibit growth of the normal flora within a clinical sample. Vancomycin is a narrow spectrum antibiotic which inhibits cell wall synthesis and therefore inhibits Gram-positive microbes such as Staphylococcus and Clostridia. It would be understood by persons of ordinary skill in the art that other narrow spectrum antibiotics effective in inhibiting cell wall synthesis in Gram-positive bacteria can also be used.

Amphotericin is a broad spectrum antifungal and antiprotozoan agent that interacts with the sterols of the cell membrane. It would also be understood by ordinarily skilled artisans that other agents which have, either singularly or separately, antifungal or antiprotozoal activity can also be used in the subject medium.

Colistin is a narrow spectrum antimicrobial effective on Gram-negative enterics. Substitution of other narrow spectrum antibiotics effective against Gram-negative enterics would also be readily recognized in the art. The inclusion of these antimicrobial agents in the medium of the subject invention can prevent the overgrowth by the hardy normal flora in the specimen having Chlamydia, Mycoplasma, Ureaplasma or a virus.

In a preferred embodiment, the medium is adjusted to approximately physiological pH, which is understood in the art to be about 7.1-7.5. A particularly preferred embodiment comprises a medium which is adjusted to a pH of 7.4.+-.0.2 and is most preferably 7.4. The subject medium is isotonic and non-toxic to mammalian cells. For example, the medium is particularly advantageous in that it is compatible with use in commercial ELISA (including membrane ELISA), PCR or DNA probe assays.

In practice, the subject transport media can be provided in 1 dram vials for convenient inoculation, or can be provided in a standard 15 ml polypropylene centrifuge tube, containing a premeasured 3 ml volume of medium. It would be understood that other biologically inert materials can also be used for the container tubes. Also, the volumes and sizes used herein are easily and readily adaptable to other situations. Also within the centrifuge tube along with the medium can be included glass beads. Typically, four (3 mm) glass beads can be included. This size of glass bead is preferred in order to prevent them from becoming trapped in the bottom of the centrifuge tube while being vortexed.

The novel media of the subject invention, as stated above, are advantageously useful with certain diagnostic procedures, including ELISA (especially membrane ELISA), PCR, and DNA probe techniques. Thus, the subject invention includes novel methods of using a transport medium where a single medium can be employed for collection, storage, transport, or analysis of a sample. The subject method of collecting and transporting the sample, which would be readily recognized by persons of ordinary skill in the art, includes the steps of collecting the sample by standard procedures, and inoculating the medium with the sample according to known techniques.

A further advantage of the subject invention results from the subject medium's compatibility with analysis procedures which can be performed on the sample to detect a particular fastidious organism and thereby diagnose an infection with such an organism in a patient. A particularly useful aspect of the subject medium, e.g., Transport Medium A, is the novel method of using the medium to collect, transport, and analyze the sample for detecting or diagnosing a viral, chlamydial, mycoplasmal, or ureaplasmal infection by membrane ELISA methods. The particular utility includes the capability of the subject transport medium to serve as a collection, transport, or storage medium which retains viability of more than one or all of those organisms, namely, Chlamydia, Mycoplasma, Ureaplasma, or viruses. Another novel method of use employs the subject media in PCR techniques for the detection and diagnosis of those organisms. The subject media also provide a novel method of using nucleic acid probe techniques e.g., DNA probes. The subject media inoculated with the test sample can be used directly with the reagents employed in these analysis procedures, i.e., the subject medium does not interfere with the normal properties or activities of these standard reagents. In certain instances, the subject medium can effectively become a reagent, e.g., a buffer solution for use in the assay procedure. This is advantageous in that the transport medium does not have to be completely removed from the sample, e.g., cells, prior to conducting these ELISA, PCR or nucleic acid probe procedures.

By incorporating a label indicating specific instructions for using the novel media with ELISA, PCR or nucleic acid probe techniques with the tubes containing media and glass beads, the subject invention includes a novel article of manufacture.

Kits can also be provided where the novel medium is provided and is separately packaged with other materials useful for collection, transport, and analysis of a sample. For example, in a preferred embodiment, the kit comprises the novel medium (3 ml) provided with four 3 mm glass beads in a 15 ml polypropylene centrifuge tube, pre-scored swabs for collection of the sample and inoculation in the medium, and a patient information card, in a leak-resistant compartmentalized package. A typical compartmentalized package for the subject kit can be a polypropylene bag, preferably having two or more pockets for convenience of use.

Following are examples which illustrate procedures, including the best mode, for practicing the invention. These examples should not be construed as limiting. All percentages are by weight and all solvent mixture proportions are by volume unless otherwise noted.

EXAMPLE 1

Preparation and Quality Control of Transport Medium A

To prepare a 25 liter batch of Transport Medium A, the following components provided in amount as shown in Table 1, below.

TABLE 1 ______________________________________ Transport Medium A Component Amount of Component ______________________________________ H.sub.2 O 24.89 liters sucrose 1711.43 g HEPES 148.99 g KCl 10.0 g L-glutamic acid 18.0 g phenol red 275 mg gelatin 125 g CaCl.sub.2 6.63 g MgSO.sub.4.7H.sub.2 O 5.0 g BSA 125 g vancomycin 0.62 g colistin 5 .times. 10.sup.6 units amphotericin B 25.0 mg ______________________________________

In the amounts shown in Table 1, HEPES, KCl, L-glutamic acid, and phenol red are initially dissolved in 1667 ml of water and added to 18.89 liters of water. Calcium chloride (6.63 g) is dissolved in 833 ml of water and added to the initial solution. 5 g of MgSO.sub.4.7H.sub.2 O are dissolved in 834 ml of water and added to the solution. 125 g of BSA and 125 g of gelatin are dissolved in 1667 ml of water and added to the solution. The antimicrobial components, as shown in Table 1 are dissolved in 1 liter of water and added to the solution to yield the final product, Transport Medium A. The final pH of 7.4 can be arrived at with addition of acid or base. Typically, an amount of 1N NaOH can be added to arrive at the desired pH. An amount of 30-50 ml of 1N NaOH can be a typical amount of base used.

Each lot of the subject transport medium is tested for quality control in the following manner:

Appearance. Each lot should be orange-red (when frozen) and red in color at refrigerated or room temperature. The media should be almost clear with a small amount of turbidity. Lots that are yellow, purple or turbid are rejected.

Toxicity. A 0.3 ml aliquot of medium is inoculated into each of 2 MRC-5 shell vials. The vials are incubated for 18 hours at 37.degree. C. The result is recorded as normal or abnormal.

Acceptable pH range. 7.1-7.5.

Microbial contamination check. 55 tubes or 1% of each lot are randomly selected for bioburden testing. Sets of 10 tubes are placed in racks which contain 20 tryptic soy broth (TSB) tubes. One 2 ml and one 0.5 ml TSB tube is pipetted into a 0.5 ml TSB tube. After all pipetting is done, 3 racks are placed in a 37.degree. C. incubator with ambient atmosphere and 2 racks are placed in a 37.degree. C. incubator with a 5% CO.sub.2 atmosphere.

After a 72 hour incubation, the racks are removed from the incubators and examined for visible turbidity. Tubes showing turbidity are plated onto chocolate agar and MacConkey agar for isolation and identification of the contaminating organism. All TSB tubes (regardless of turbidity) are further checked for growth on solid media. This is done by plating aliquots of 0.05 ml from each TSB tube onto chocolate agar and incubating for 72 hours in the same atmosphere as the broths.

Maintenance of Chlamydia trachomatis. Type E (Seattle strain) is used for testing of the subject media. A volume (less than 50 microliters) of frozen Type E is added to a transport medium tube such that the inclusion forming units are approximately 2500 per ml. The inoculated tube is stored at 2.degree. C. to 8.degree. C. for 24 hours. An inoculum of 250 microliters from the stored tube should result in a positive culture with 200 to 400 inclusion forming units when cultured in McCory or BGMK cells. Results are recorded as Chlamydia maintained or Chlamydia not maintained. Any lots which do not maintain Chlamydia are rejected.

Maintenance of Mycoplasma/Ureaplasma. M. pneumoniae, M. hominis, and U. urealyticum are used for testing of the subject transport media. The organisms are grown to a simulated patient specimen titer and are inoculated into the media. They are stored at 2.degree.-8.degree. C. for 48 hours and are re-inoculated into plates to determine growth and viability. The results are recorded as Mycoplasma/Ureaplasma maintained or not maintained. Any lots which do not maintain these organisms will be rejected.

EXAMPLE 2

Percent Recovery of a Variety of Agents From Transport Medium A

The recovery rates following storage in Transport Medium A of various microbial agents are shown in Table 2 below. Vials containing transport Medium A were inoculated with viral (respiratory syncytial virus, herpes simplex 1, cytomegalovirus, and influenza) and non-viral test organisms (Chlamydia, Mycoplasma, and Ureaplasma) and stored at 2.degree.-8.degree. C. The samples were tested at 8 hours, 24 hours, and 48 hours. Each of the tested microbial agents was successfully recovered from the vials after 48 hours showing Transport Medium A supports microbial viability of these fastidious pathogens during storage at refrigeration temperatures.

TABLE 2 ______________________________________ Recovery Percentages of Various Agents Microbe Name/Time 8 Hours 24 Hours 48 Hours ______________________________________ respiratory syncytial virus 75% 64% 58% herpes simplex type 1, McIntyre 88% 49% cytomegalovirus (AD 169) 58% 27% influenza A H3N2, Shanghai 87 87% 74% Chlamydia trachomatis 82% 43% 33% Mycoplasma pneumoniae Recovered Recovered Mycoplasma hominis Recovered Recovered Ureaplasma ureatyticum Recovered Recovered ______________________________________

EXAMPLE 3

Comparisons of Transport Media for the Recovery of Various Agents

The subject transport medium was compared to other transport media for its ability to sustain viability of certain fastidious viral, mycoplasmal, and ureaplasmal pathogens over a one-week period of time and under different temperature conditions. For example, the storage of various pathogens in the subject medium versus Bartels Viral Transport Medium (VTM) (Baxter, Chicago, Ill.) is known for the viruses influenza A H3N2, respiratory syncytial virus (RSV), cytomegalovirus (CMV) and herpes simplex type 1, McIntyre, in Tables 3, 4, 5, and 6, respectively. Samples were compared at 25.degree. C. and 2.degree. C. Viral agents were stored in the transport media for up to one week. Recovery of most viral agents from the transport medium after one week were markedly superior than corresponding media where samples were held at 25.degree. C.

TABLE 3 ______________________________________ Transport Media Comparison, influenza A H3N2 (19,250 ff at time zero) 24 Hours 48 Hours 72 Hours 96 Hours 1 Week ______________________________________ 25.degree. C. Transport 15280 8965 5610 3135 605 Medium A Bartels VTM 14685 9295 5500 3080 460 2.degree. C. Transport 16885 14300 12210 10615 6875 Medium A Bartels VTM 16610 14575 11990 10725 6600 ______________________________________ VTM = Viral Transport Medium

TABLE 4 ______________________________________ Transport Media Comparison, RSV (2255 .times. 55 ff at time zero) 8 Hours 24 Hours 48 Hours 72 Hours 1 Week ______________________________________ 25.degree. C. Transport 1925 1760 1210 935 475 Medium A Bartels VTM 1375 990 660 490 58 2.degree. C. Transport 1705 1455 1320 1205 330 Medium A Bartels VTM 1375 1155 1045 630 275 ______________________________________

TABLE 5 ______________________________________ Transport Media Comparison, CMV Strain AD 169 (20,460 ff at time zero) 24 Hours 48 Hours 72 Hours 96 Hours 1 Week ______________________________________ 25.degree. C. Transport 9295 6655 5335 3960 287 Medium A Bartels VTM 11440 8030 5390 4510 301 2.degree. C. Transport 11880 5555 2585 1760 1430 Medium A Bartels VTM 11605 6435 2530 1760 1045 ______________________________________

TABLE 6 ______________________________________ Transport Media Comparison, herpes simplex type I McIntyre-A549 (40,865 .times. 55 infectious particles at time zero) 24 Hours 48 Hours 72 Hours 96 Hours 1 Week ______________________________________ 25.degree. C. Transport 26950 12265 3520 2530 475 Medium A Bartels VTM 28050 7810 3575 495 183 2.degree. C. Transport 36025 19965 12980 8910 4895 Medium A Bartels VTM 36850 19030 13035 9295 3905 ______________________________________

In addition, the subject medium was compared to both MSP and Bartels CTM for storage of Chlamydia samples (Table 7). In this comparison, the inoculum was 9700 IFU at time zero.

As clearly shown in Table 7, the subject transport medium demonstrated far greater recovery rates than samples stored in the other media. For example, Chlamydia samples kept at 2.degree. C. supported Chlamydia viability for up to 72 hours in Transport Medium B whereas, using the other media, no Chlamydia was recovered after only 24 hours of storage.

TABLE 7 ______________________________________ Transport Media Comparison Chlamydia - Type E-Seattle Strain 8 Hours 24 Hours 48 Hours 72 Hours ______________________________________ 25.degree. C. Transport Medium A 3500 1220 188 106 MSP 2600 100 0 0 Bartels CTM 1600 256 0 0 2.degree. C. Transport Medium A 7920 4180 3240 2260 MSP 5520 3460 2680 1360 Bartels CTM 5580 3100 500 480 ______________________________________

EXAMPLE 4

Freeze-Thaw Properties of Transport Medium A

In one study, 33 positive clinical specimens of varicella-zoster virus (VZV) were identified from a batch of 102 patient samples. VZV is an extremely labile virus under cryopreservation. All samples had been frozen in Transport Medium A for a period of one year, at -70.degree. C. Two additional positive specimens were identified from a different batch of 44 samples which had originally been identified as negative specimens.

EXAMPLE 5

Use of Transport Medium A in a Commercial PCR Assay for Chlamydia trachomatis (Ct.)

The effectiveness of Transport Medium A as compared to Amplicor transport medium (Roche Diagnostics, Nutley, N.J.) for use in the C1 PCR assay (Roche).

(a) Two female cervical swabs were collected from each participant randomly selected from a high prevalence population. The first swab was placed in Transport Medium A. The second was swirled in the Amplicor and discarded as per the manufacturer's instructions. One ml of the vortexed Transport Medium A and Amplicor were each mixed with 1.0 ml of Specimen Diluent (Roche) and incubated for 10 minutes at room temperature. Then, 50 .mu.l of each prepared sample was used for PCR amplification according to the manufacturer's instructions.

(b) The second group of samples were those received routinely in Transport Medium A for testing, i.e., a low prevalence group. A group of 100 negatives and 25 true positives were analyzed by PCR. After vortexing, a 1.0 ml aliquot was removed from the Transport Medium A and placed in the Amplicor transport media. One ml of the Amplicor/Transport Medium A mix and of the Transport Medium A alone were then mixed with Specimen Diluent and assayed as above.

All specimens were tested by multiple methods: culture, EIA (Syva, Palo Alto, Calif.), SFA (Syva, Palo Alto, Calif.), or DNA probe (GenProbe, San Diego, Calif.). True positives were those determined to be positive by culture, or by at least two nonculture methods.

(c) Results. Among 30 samples from the high prevalence population there were 10 true positives. Nine were positive by PCR and culture, or by two or more of the antigen/probe methods. One was positive by PCR alone (both the Transport Medium A and Amplicor Media). One Amplicor PCR positive specimen was negative with the Transport Medium A PCR test.

In the low prevalence group, both Amplicor and Transport Medium A detected 19 of the 25 true positives. Transport Medium A detected 5 positives which were missed by Amplicor (perhaps due to dilution), and both missed 1 positive. One additional PCR positive specimen was detected in both transports from the 100 negatives. Thus, it can be concluded that Transport Medium A can be used directly with Specimen Diluent in this PCR assay without significant reduction in true positives or increase in false positives. Specimens received in Transport Medium A which are then placed in Amplicor medium prior to mixing with the Specimen Diluent may show false negatives due to dilution or other factors.

It should be understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and the scope of the appended claims.

References

Amies (1967) Can. J. Public Health 58: 296-300.

Bailey et al. (1978) "Specimen Containers and their Transport," Diagnostic Microbiology 29-32, The C. V. Mosby Co., St. Louis, Mo.

Bowie and Holmes (1977) in Infectious Diseases, 2 ed., (Hoeprich, Paul D., ed.) Harper & Row, Hagerstown, pp. 486-487.

Saiki, R. K. (1989) in PCR Technology, Stockton Press, United Kingdom, pp. 7-16.

Smart et al. (1954) Can. J. Public Health, 45: 73-83.