comparative evaluation of two new amies swab transport ... · fisherﬁnest® (starplex) swab in...

C-295 ASM 105th General Convention - Atlanta, Georgia, June 2005

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Comparative Evaluation of Two New Amies Swab Transport Systems BD CultureSwab™ Max V(+) (Copan) and the Fisherfinest® (Starplex) Swab

M. SARINA*, D.M. LAWRENCE, CENTRAL COAST PATHOLOGY, San Luis Obispo, CA

ABSTRACTBackground: In light of the emphasis being placed on quality in the clinical laboratory, and given the increased awareness of the importance of the pre-analytical phase of specimen processing, the selection of the most appropriate collection device cannot be overemphasized. The objective of this study was to compare the ability of 2 new swab transport systems to maintain the viability of several strains of clinically significant bacteria. Evaluations were performed at 0, 6, 24 and 48 hours using the roll plate method as described in NCCLS M-40(1). Testing was conducted at room temperature. In this author’s opinion, survival of clinical isolates held at room temperature prior to processing poses a major chal-lenge for laboratories.

Method: Two new transport devices containing Amies clear gel were evaluated. Swabs were inoculated with 100 ul of standardized suspensions (10-2, 10-3 and 10-4) using clinical isolates and ATCC strains. Swabs were inoculated in trip-licate (12 swabs for each brand). Colony counts were com-piled for each dilution and incubation period and compared to the 0 hr colony counts to determine % recovery of each organism. A total of 25 strains were tested including: S. pyogenes (GAS) ATCC 19615, S. agalactiae (GBS) ATCC 27956, H. influenzae (H flu) ATCC 49247 and N. gonorrhoeae (GC) ATCC 43069. Several clinical isolates were also tested since ATCC strains do not appear to offer the same challenges as clini-cal isolates in many cases.

Results: Organism dilutions with countable growth within the range of 30-300 CFU’s were averaged and included for the pur-pose of comparisons. Estimated CFU’s that were greater than 300 were approximated and included for comparison. The difference in counts between the two brands were recorded for the various dilutions and time points.

Conclusion: Based on the results of this study, the BD Max V(+) swab was superior to the Fisherfinest® (Starplex) in promoting survival and release of significant clinical isolates held at room temperature prior to processing. Either swab would be suitable for samples processed within 6 hours but if transport is expected to exceed 6 hrs, the BD Max V(+) would be the recommended choice.

INTRODUCTIONThe emphasis placed on quality in healthcare has never been greater and the importance of the pre-analytical phase of testing cannot be overstated. Delays in specimen transport and process-ing may lead to reduced recovery of significant pathogens and ul-timately, these elements have a significant impact on the quality of laboratory results (2,3). In order to assess the importance of proper specimen collection & transport, we compared two new trans-port devices – the BD Max V(+) (Copan) and the Fisherfinest® (Starplex) swab. Both incorporate Amies clear gel. The BD MaxV(+) (Copan) swab is manufactured by Copan Diagnostics for Becton Dickinson. Copan has incorporated vegetable proteins

in the standard swab winding process. This unique feature ap-pears to improve organism stability and viability during specimen transport and storage without creating organism overgrowth.

METHODThe following stock culture strains were used in this study: • Haemophilus influenzae ATCC 49247

• Neisseria gonorrhoeae ATCC 43069 • Streptococcus agalactiae ATCC 27956 • Streptococcus pyogenes ATCC 19615

In addition to the ATCC strains listed above, several clinical iso-lates from each group were tested because clinical strains histori-cally offer additional challenges. Culture Swabs:The following swabs were evaluated in this study:• BD Culture Swab™ Max V(+) Amies Clear (Copan)

Lot # 42109 Exp. 03/2006

• Fisherfinest® Amies Clear (Starplex) Lot # 4D05A Exp. 04/2006

Test Protocol: Roll Plate Method• For each organism, a 0.5 McFarland standard (1.5 x 108

CFU/mL) was prepared in 0.85 physiological saline (pH 6.8 –7.2) from 18-24 hr. cultures using a Vitek turbidity meter (BioMerieux)

• From this suspension, four 1:10 serial dilutions were prepared: 1:10, 1:100, 1:1000 and 1:10,000 representing 1.5 x 107 – 1.5 x 104 CFU/mL.

• An Eppendorf pipette was used to deliver 100 ul of the 102, 103 and 104 dilutions into the wells of a microtiter plate.

• Each swab was placed into the appropriately labeled wells allowing the fluid to absorb for 10 sec. Swabs were tested in triplicate.

• Swabs were then inserted back into the transport device.

• To obtain baseline counts (zero time) the 3 swabs of each organism/dilution were removed from the transport device after 15 min. incubation at room temperature and spread over the agar surface using the roll plate technique as illustrated in Figure 1.

• The remaining swabs were held at room temperature for 6, 24 and 48 hrs.

• Swabs were plated out at the end of each time period and incubated at 35º C for 48 hrs. Counts were then recorded.

• Colony counts of >300 colonies were approximated and averaged for each of the 3 swabs for each time point and dilution.

• Counts at zero hours were compared to counts at 6, 24 and 48 hours.


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Figure 1.

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Roll Plate Method


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Comparison of Organism Recovery from BD Max V (+) and Fisherfinest® (Starplex) Swabs

Roll Plate Method - Colony Count (% Survival)* at Room Temperature/103 dilution

Organism Swab 0 hr 6 hr 24 hr 48 hr

H. influenzaeBD Max V (+) >300 (100%) >300 (100%) 280 (93%) 250 (83%)

Fisherfinest® >300 (100%) >300 (100%) 50 (17%) 0 (0%)

N. gonorrhoeaeBD Max V (+) 300 (100%) 250 (83%) 125 (42%) 75 (25%)

Fisherfinest® 300 (100%) 230 (77%) 5 (1.7%) 0 (0%)

S. agalactiaeBD Max V (+) 300 (100%) 300 (100%) 300 (100%) 300 (100%)

Fisherfinest® >300 (100%) 300 (100%) 100 (33%) 50 (17%)

S. pyogenesBD Max V (+) 250 (100%) 250 (100%) 250 (100%) 250 (100%)

Fisherfinest® 280 (100%) 280 (100%) 200 (71%) 150 (54%)

*% Recovery is calculated relative to the zero-hour count (100%)

RESULTS


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DISCUSSION / CONCLUSIONS• The benefits of refrigeration have been noted in numerous

publications, however, maintaining specimens at 4°C prior to processing is not routinely practiced on a day-to-day basis. For this reason, we chose to evaluate swabs held at room temperature as we feel this poses the greatest challenge to laboratories.

• Loss of viability during transport will have an obvious negative effect on culture results, especially when the organisms are present in low numbers.

• We conclude that the BD Max V(+) was superior to the Fisherfinest® (Starplex) swab in promoting survival and eventual release of fastidious pathogens during storage at room temperature if plating of cultures exceeded 6 hours. This may be related to the use of the non-animal proteins embedded in the BD Max V(+) (Copan) rayon swab. The protective effects of these proteins may be responsible for the superior performance noted with the BD Max V(+) (Copan) swab.

REFERENCES:1. Clinical Laboratory Standards Institute – Formerly NCCLS,

2003. Quality control of microbiological transport systems. M40A. CLSI, Wayne, PA.

2. Perry J.L. 2001. Effects of temperature on fastidious organism viability during swab transport. In Abstracts of the 101st General Meeting of the ASM, Orlando, FL, 2001.

3. Bourbeau P, 2004. Delivering the goods to microbiology labs. College of American Pathologists (CAP) Update, January, 2004.

ACKNOWLEDGEMENTS:The author wishes to thank Copan Diagnostics for support of this poster and to Ryan Middleton and Tim Zumwalt for their techni-cal assistance.

GC - N. gonorrhoeae = Rm Temp (48 hrs) 10-4 BD Max V(+) - LeftGC - N. gonorrhoeae = Rm Temp (48 hrs) 10-4 Fisherfinest® (Starplex) - Right



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comparative evaluation of two new amies swab transport ... · fisherﬁnest® (starplex) swab in...

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