- Email: [email protected]
Evaluation of a New Bacterial Culture and Sensitive Device
CORRECTION OF APHAKIA
VOL. 68, NO. 2
4. Pieries, C. L. : The contact lens in unilateral aphakia. Tr. Ophth. Soc. Ceylon 7:45, 1964. 5. Gerhard, J. P. and Bronner, A.: La durée de port dans le temps du verre de contact chez l'aphaque unilateral: Etude des causes d'abandon. Bull. Soc. Ophth. France 65:633, 1965. 6. Bellamare, F.: L'aphaquie et sa correction par les lunettes et les lentilles corneennes. Laval Med. 38:308, 1967. 7. Shumate, R. E. : Contact lenses following cataract surgery. Med Trial Techniq. Quart. 13:31, 1967. 8. Berges, S. G.: Contact lenses in aphakia. Bol. Hosp. Oztal, N. S. de la Luz (Mex) 19:101, 1966.
323
9. Dixon, J. M., Young, C. A. Baldone, J. A., Halberg, G. P., Sampson, W. and Stone, W., Jr.: Complications associated with the wearing of con tact lenses. JAMA 195:901, 1966. 10. Spaeth, P. G.: The pathology of contact lenses. Tr. Am. Acad. Ophth. Otolaryn. 66: 294, 1962. 11. Mandelbaum, J.: Corneal vascularization in aphakic eyes following the use of contact lenses. Arch. Ophth. 71:633, 1964. 12. Welsh, R. G : Distressing wound complica tions from contact lenses for aphakia. (Correspon dence.) Arch. Ophth. 79: 507, 1968.
EVALUATION O F A N E W BACTERIAL CULTURE AND S E N S I T I V E DEVICE ADA
PADGETT AND ARTHUR
H.
KEENEY,
M.D.
Philadelphia, Pennsylvania
Anti-infective therapy frequently requires laborious and expensive culturing and sensi tivity testing to select appropriate agents. As the number of agents increases, selection by traditional methods also increases in com plexity. The primary diagnostic medium ( P D x ) * is a new bactériologie aid for cul turing micro-organisms and for initial anti biotic sensitivity screening. It is intended for the practicing ophthalmologist and not as a substitute for major laboratory facilities. This report evaluates the PDx for accuracy and economy as compared to traditional cul ture methods. The PDx is a clear plastic (acrylic) tube six inches long, one inch square in cross sec tion, and divided into four chambers, each containing a serum-enriched agar medium capable of supporting the growth of most common pathogens found in localized infec tions. Table 1 lists the 12 organisms success fully grown in the device to date. The manu facturer indicates that the shelf-life of the PDx is up to six months when stored under From the Wills Eye Hospital and the Depart ment of Ophthalmology, Temple University. Reprint requests to Arthur H. Keeney, M.D., Wills Eye Hospital, 1601 Spring Garden Street, Philadelphia, Pennsylvania 19130. »Manufactured by Allergan Pharmaceuticals, Santa Ana, California.
TABLE 1 ORGANISMS GROWN ON THE PDx™ CULTURE MEDIA
Micrococcus species (coagulase negative) Aerobacter aerogenes Moraxella lucunata Corynebacterium xerosis Hemophilus aegyptius Staphylococcus aureus (coagulase positive) hemolytic nonhemolytic Staphylococcus albus hemolytic nonhemolytic Proteus vulgaris Proteus mirabilis Diphtheroids Streptococcus beta hemolytic alpha hemolytic Pseudomonas aeruginosa
refrigeration in its individual plastic bag. Three of the four chambers incorporate common anti-infective agents in the me dium ; the fourth, a control, contains only the medium. The anti-infectives studied to date are the three provided by the manufacturer: chloramphenicol (0.5%), neomycin (0.5%) and sulfacetamide (10%). Other combina tions may be obtained on request: lincomycin, tetracyline, erythromycin, polymyxin and so forth. A removable cap to which a sterile cotton swab is attached covers one end of the tube
324
AMERICAN JOURNAL OF OPHTHALMOLOGY
Fig. 1 (Padgett and Keeney). Primary diagnos tic medium (PDx) as viewed from above, showing the swab attached to the cap and in position to streak the first of the four separate chambers.
(fig. 1). In use, the swab is removed from the unit by holding the attached cap and placed in contact with the infected site. It is then used to streak the surface of the me dium in each chamber. The first chamber is streaked, then the swab is rotated 90 degrees to bring a new surface in contact with the medium, then the second chamber is streaked. The streaking procedure is re peated until the fourth (the control) cham ber has been innoculated. The cap is replaced following streaking without discarding the contaminated swab from the tube. The PDx is then incubated at 35°C and observed for growth of colonies of bacteria and fungi. When micro-organisms are pres ent in the material obtained from a patient, growth usually occurs on the control medium within 24 hours. Lack of growth in a specific antibiotic chamber suggests in vitro sensitiv ity, whereas growth indicates resistance to the antibiotic in the concentration present. An indicator (phenol red) in the medium turns yellow if the growing organism pro duces acid (for example, Staphylococcus), and a deep red or purple color if the orga nism produces ammonia ( for example, Pseudomonas). COMPARISON WITH CONVENTIONAL CULTURES
Aragones and Eriksen 1 compared the effi ciency of PDx with traditional laboratory methods in providing rapid, accurate culture
AUGUST, 1969
and sensitivity information. From 115 con secutive comparisons of cultures taken before, during and after treatment, the PDx and their laboratory methods yielded identical results in 99 cases. In 11 of the 115 comparisons, the PDx yielded positive growth when their con ventional laboratory tests did not. They concluded that success in therapy, when agent selection was based on PDx reading, indicated a strong correlation with PDx find ings, and also reported that gross identifica tion of the organism was possible in many cases and that, in all instances in which the device yielded growth, sensitivity informa tion was available within 24 hours. These conclusions are substantiated by our studies of 33 cultures. The PDx in com parison with our routine laboratory methods, using brain-heart infusion broth, blood-agar plates and sensitivity discs, showed correla tion of growth and identification in all but one of the 33 cases (table 2). Of the 32 cases with identical growth results, the two methods revealed similar sensitivity data in all but five cases—two instances of Strepto coccus, two of Staphylococcus aureus and one of Proteus. Each of these differences involved sensitivity to sulfacetamide ; however, the sulfacetamide concentration in the PDx ( 10% ) is higher than that used in most gen eral laboratory sensitivity procedures and thus more closely parallels the topical ther apy with the 10% to 30% preparations used ophthalmologically. The PDx is also helpful when more specific identification of orga nisms is required, as it can provide colonies from the control chamber for subculture and further study. Comparison of our culturing and sensitivity test procedures with the PDx indicated both convenience and economy. Culture and sensitivity studies are con ducted in a manner generally similar throughout the medical profession. Orga nisms are removed from an infected site with a flamed loop or cotton swab. They are grown in a broth for 24 hours, and/or streaked onto agar plates. Subcultures of in dividual colonies are then made, sensitivity
325
BACTERIAL CULTURE DEVICE
VOL. 68, NO. 2
TABLE 2 COMPARATIVE STUDY OF CULTURES OBTAINED AT WILLS EYE HOSPITAL EMPLOYING STANDARD LABORATORY PROCEDURES AND THE P D X ™ DIAGNOSTIC PROCEDURE Standard Procedure M icro-organisms Recovered
Staphylococcus aureus Staphylococcus albus Proteus vulgaris Diphtheroids Streptococcus beta hemolytic Pseudomonas
P D x ™ Procedure
Resistant t o No. Isolates
Sulfacetamide
Polymyxin
Neomycin
7
3
7
3
8
1
8
6
5
1 2 1
No. Isolates
Resistant t o Sulfacetamide
Polymyxin
Neomycin
7
S
7
3
1
8
1
8
1
3
4
6
6
3
4
1 1
1 1
1 1
1 2
1 0
1 2
1 2
1
0
1
1
1
0
1
discs applied and the plate incubated for still another 24 hours. The plate is read for sen sitivity information and, if more specific identification of the organism is required, further tests (for example, a coagulase test for Staphylococcus) are conducted, requir ing an additional 24 to 48 hours. In contrast, the PDx requires fewer steps and is readable in a shorter time. No con tamination of the cap can occur during swab removal or use because the cap remains in the user's hand. PDx offers savings in laboratory material and time. Traditional methods require that various agar media and broths be prepared, mixed, cooked, sterilized and poured into Petri dishes. This usually necessitates the purchase and maintenance of significant amounts of glassware. Initial costs, depre ciation of glassware and other laboratory equipment, such as hot-air ovens and auto claves, are reduced by using the PDx.
Though figures may differ regionally, the basic relationships are approximately the same. At Wills Eye Hospital, over 7,000 routine cultures are done yearly at an aver age cost to the institution of approximately $5.00 each. In this institution the use of PDx could result in a savings of approxi mately 60% without loss of efficacy. SUMMARY
An initial bactériologie aid, PDx, provid ing diagnostic information rapidly and at re duced expenditures for materials, glassware, equipment usage and labor costs, has been evaluated against standard laboratory tech niques. The device offers accurate and par ticularly helpful aid to the ophthalmic practi tioner. REFERENCES
1. Aragones, J. V. and Eriksen, S. P. : A control test of a new microbiological testing device under office conditions. Am. J. Ophth. 67 :728, 1969.
VOL. 68, NO. 2
4. Pieries, C. L. : The contact lens in unilateral aphakia. Tr. Ophth. Soc. Ceylon 7:45, 1964. 5. Gerhard, J. P. and Bronner, A.: La durée de port dans le temps du verre de contact chez l'aphaque unilateral: Etude des causes d'abandon. Bull. Soc. Ophth. France 65:633, 1965. 6. Bellamare, F.: L'aphaquie et sa correction par les lunettes et les lentilles corneennes. Laval Med. 38:308, 1967. 7. Shumate, R. E. : Contact lenses following cataract surgery. Med Trial Techniq. Quart. 13:31, 1967. 8. Berges, S. G.: Contact lenses in aphakia. Bol. Hosp. Oztal, N. S. de la Luz (Mex) 19:101, 1966.
323
9. Dixon, J. M., Young, C. A. Baldone, J. A., Halberg, G. P., Sampson, W. and Stone, W., Jr.: Complications associated with the wearing of con tact lenses. JAMA 195:901, 1966. 10. Spaeth, P. G.: The pathology of contact lenses. Tr. Am. Acad. Ophth. Otolaryn. 66: 294, 1962. 11. Mandelbaum, J.: Corneal vascularization in aphakic eyes following the use of contact lenses. Arch. Ophth. 71:633, 1964. 12. Welsh, R. G : Distressing wound complica tions from contact lenses for aphakia. (Correspon dence.) Arch. Ophth. 79: 507, 1968.
EVALUATION O F A N E W BACTERIAL CULTURE AND S E N S I T I V E DEVICE ADA
PADGETT AND ARTHUR
H.
KEENEY,
M.D.
Philadelphia, Pennsylvania
Anti-infective therapy frequently requires laborious and expensive culturing and sensi tivity testing to select appropriate agents. As the number of agents increases, selection by traditional methods also increases in com plexity. The primary diagnostic medium ( P D x ) * is a new bactériologie aid for cul turing micro-organisms and for initial anti biotic sensitivity screening. It is intended for the practicing ophthalmologist and not as a substitute for major laboratory facilities. This report evaluates the PDx for accuracy and economy as compared to traditional cul ture methods. The PDx is a clear plastic (acrylic) tube six inches long, one inch square in cross sec tion, and divided into four chambers, each containing a serum-enriched agar medium capable of supporting the growth of most common pathogens found in localized infec tions. Table 1 lists the 12 organisms success fully grown in the device to date. The manu facturer indicates that the shelf-life of the PDx is up to six months when stored under From the Wills Eye Hospital and the Depart ment of Ophthalmology, Temple University. Reprint requests to Arthur H. Keeney, M.D., Wills Eye Hospital, 1601 Spring Garden Street, Philadelphia, Pennsylvania 19130. »Manufactured by Allergan Pharmaceuticals, Santa Ana, California.
TABLE 1 ORGANISMS GROWN ON THE PDx™ CULTURE MEDIA
Micrococcus species (coagulase negative) Aerobacter aerogenes Moraxella lucunata Corynebacterium xerosis Hemophilus aegyptius Staphylococcus aureus (coagulase positive) hemolytic nonhemolytic Staphylococcus albus hemolytic nonhemolytic Proteus vulgaris Proteus mirabilis Diphtheroids Streptococcus beta hemolytic alpha hemolytic Pseudomonas aeruginosa
refrigeration in its individual plastic bag. Three of the four chambers incorporate common anti-infective agents in the me dium ; the fourth, a control, contains only the medium. The anti-infectives studied to date are the three provided by the manufacturer: chloramphenicol (0.5%), neomycin (0.5%) and sulfacetamide (10%). Other combina tions may be obtained on request: lincomycin, tetracyline, erythromycin, polymyxin and so forth. A removable cap to which a sterile cotton swab is attached covers one end of the tube
324
AMERICAN JOURNAL OF OPHTHALMOLOGY
Fig. 1 (Padgett and Keeney). Primary diagnos tic medium (PDx) as viewed from above, showing the swab attached to the cap and in position to streak the first of the four separate chambers.
(fig. 1). In use, the swab is removed from the unit by holding the attached cap and placed in contact with the infected site. It is then used to streak the surface of the me dium in each chamber. The first chamber is streaked, then the swab is rotated 90 degrees to bring a new surface in contact with the medium, then the second chamber is streaked. The streaking procedure is re peated until the fourth (the control) cham ber has been innoculated. The cap is replaced following streaking without discarding the contaminated swab from the tube. The PDx is then incubated at 35°C and observed for growth of colonies of bacteria and fungi. When micro-organisms are pres ent in the material obtained from a patient, growth usually occurs on the control medium within 24 hours. Lack of growth in a specific antibiotic chamber suggests in vitro sensitiv ity, whereas growth indicates resistance to the antibiotic in the concentration present. An indicator (phenol red) in the medium turns yellow if the growing organism pro duces acid (for example, Staphylococcus), and a deep red or purple color if the orga nism produces ammonia ( for example, Pseudomonas). COMPARISON WITH CONVENTIONAL CULTURES
Aragones and Eriksen 1 compared the effi ciency of PDx with traditional laboratory methods in providing rapid, accurate culture
AUGUST, 1969
and sensitivity information. From 115 con secutive comparisons of cultures taken before, during and after treatment, the PDx and their laboratory methods yielded identical results in 99 cases. In 11 of the 115 comparisons, the PDx yielded positive growth when their con ventional laboratory tests did not. They concluded that success in therapy, when agent selection was based on PDx reading, indicated a strong correlation with PDx find ings, and also reported that gross identifica tion of the organism was possible in many cases and that, in all instances in which the device yielded growth, sensitivity informa tion was available within 24 hours. These conclusions are substantiated by our studies of 33 cultures. The PDx in com parison with our routine laboratory methods, using brain-heart infusion broth, blood-agar plates and sensitivity discs, showed correla tion of growth and identification in all but one of the 33 cases (table 2). Of the 32 cases with identical growth results, the two methods revealed similar sensitivity data in all but five cases—two instances of Strepto coccus, two of Staphylococcus aureus and one of Proteus. Each of these differences involved sensitivity to sulfacetamide ; however, the sulfacetamide concentration in the PDx ( 10% ) is higher than that used in most gen eral laboratory sensitivity procedures and thus more closely parallels the topical ther apy with the 10% to 30% preparations used ophthalmologically. The PDx is also helpful when more specific identification of orga nisms is required, as it can provide colonies from the control chamber for subculture and further study. Comparison of our culturing and sensitivity test procedures with the PDx indicated both convenience and economy. Culture and sensitivity studies are con ducted in a manner generally similar throughout the medical profession. Orga nisms are removed from an infected site with a flamed loop or cotton swab. They are grown in a broth for 24 hours, and/or streaked onto agar plates. Subcultures of in dividual colonies are then made, sensitivity
325
BACTERIAL CULTURE DEVICE
VOL. 68, NO. 2
TABLE 2 COMPARATIVE STUDY OF CULTURES OBTAINED AT WILLS EYE HOSPITAL EMPLOYING STANDARD LABORATORY PROCEDURES AND THE P D X ™ DIAGNOSTIC PROCEDURE Standard Procedure M icro-organisms Recovered
Staphylococcus aureus Staphylococcus albus Proteus vulgaris Diphtheroids Streptococcus beta hemolytic Pseudomonas
P D x ™ Procedure
Resistant t o No. Isolates
Sulfacetamide
Polymyxin
Neomycin
7
3
7
3
8
1
8
6
5
1 2 1
No. Isolates
Resistant t o Sulfacetamide
Polymyxin
Neomycin
7
S
7
3
1
8
1
8
1
3
4
6
6
3
4
1 1
1 1
1 1
1 2
1 0
1 2
1 2
1
0
1
1
1
0
1
discs applied and the plate incubated for still another 24 hours. The plate is read for sen sitivity information and, if more specific identification of the organism is required, further tests (for example, a coagulase test for Staphylococcus) are conducted, requir ing an additional 24 to 48 hours. In contrast, the PDx requires fewer steps and is readable in a shorter time. No con tamination of the cap can occur during swab removal or use because the cap remains in the user's hand. PDx offers savings in laboratory material and time. Traditional methods require that various agar media and broths be prepared, mixed, cooked, sterilized and poured into Petri dishes. This usually necessitates the purchase and maintenance of significant amounts of glassware. Initial costs, depre ciation of glassware and other laboratory equipment, such as hot-air ovens and auto claves, are reduced by using the PDx.
Though figures may differ regionally, the basic relationships are approximately the same. At Wills Eye Hospital, over 7,000 routine cultures are done yearly at an aver age cost to the institution of approximately $5.00 each. In this institution the use of PDx could result in a savings of approxi mately 60% without loss of efficacy. SUMMARY
An initial bactériologie aid, PDx, provid ing diagnostic information rapidly and at re duced expenditures for materials, glassware, equipment usage and labor costs, has been evaluated against standard laboratory tech niques. The device offers accurate and par ticularly helpful aid to the ophthalmic practi tioner. REFERENCES
1. Aragones, J. V. and Eriksen, S. P. : A control test of a new microbiological testing device under office conditions. Am. J. Ophth. 67 :728, 1969.