Lynn L. Horvath

Direct Comparison of the BACTEC 9240 and BacT/ALERT 3D Automated Blood Culture Systems for Candida Growth Detection

ABSTRACT A direct comparison of two automated blood culture systems was conducted to compare their ability to detect Candida growth. The systems evaluated were the BACTEC 9240 (Bactec) and BacT/ALERT 3D (BacT). The aerobic, anaerobic, and mycology media for each system were evaluated: Bactec Plus Aerobic/F, Plus Anaerobic/F, and Myco/F Lytic bottles,, respectively, and BacT FA, SN, and MB bottles, respectively. Each blood culture bottle was inoculated with fresh blood from healthy donors. Fifty isolates of Candida spp. were used. The six different blood culture bottles were each inoculated with 1,000 yeasts per bottle and then incubated in the corresponding automated system. The BacT detected growth of 90% (135 of 150) of Candida pathogens, while Bactec detected 66% (100 of 150). Growth was detected in all BacT and Bactec mycology bottles, all BacT aerobic bottles, and by terminal subculture of all bottles. Sixty-five of 300 (22%) bottles had no growth detected; 50 from the Bactec (5 aerobic and 45 anaerobic) and 15 from the BacT (all anaerobic). Terminal subculture of “negative” bottles demonstrated viable yeast growth from all 65 bottles, representing 65 false-negatives. The mean time to growth detection in the BacT system was 25.62 h while the Bactec was 27.30 h (P < 0.01). Both automated blood culture systems detected all episodes of simulated candidemia when specialized mycology media were used. However, when only standard aerobic and anaerobic media were used, the BacT performed better than the Bactec in overall growth detection, time to growth detection, and number of false-negatives.

Presumptive identification of Candida species other than C. albicans, C. krusei, and C. tropicalis with the chromogenic medium CHROMagar Candida.

BackgroundCHROMagar Candida (CaC) is increasingly being reported as a medium used to differentiate Candida albicans from non-albicans Candida (NAC) species. Rapid identification of NAC can assist the clinician in selecting appropriate antifungal therapy. CaC is a differential chromogenic medium designed to identify C. albicans, C. krusei, and C. tropicalis based on colony color and morphology. Some reports have proposed that CaC can also reliably identify C. dubliniensis and C. glabrata.MethodsWe evaluated the usefulness of CaC in the identification of C. dubliniensis, C. famata, C. firmetaria, C. glabrata, C. guilliermondii, C. inconspicua, C. kefyr, C. lipolytica, C. lusitaniae, C. norvegensis, C. parapsilosis, and C. rugosa.ResultsMost NAC produced colonies that were shades of pink, lavender, or ivory. Several isolates of C. firmetaria and all C. inconspicua produced colonies difficult to differentiate from C. krusei. Most C. rugosa isolates produced unique colonies with morphology like C. krusei except in a light blue-green color. C. glabrata isolates produced small dark violet colonies that could be differentiated from the pink and lavender colors produced by other species. All seventeen isolates of C. dubliniensis produced green colonies similar to those produced by C. albicans.ConclusionC. glabrata and C. rugosa appear distinguishable from other species using CaC. Some NAC, including C. firmetaria and C. inconspicua, could be confused with C. krusei using this medium.

Detection of Simulated Candidemia by the BACTEC 9240 System with Plus Aerobic/F and Anaerobic/F Blood Culture Bottles

ABSTRACT We studied the ability of the BACTEC 9240 automated blood culture system to detect simulated candidemia, including both Candida albicans and non-albicans Candida species. Simulated blood cultures were produced using 50 Candida isolates and BACTEC Plus Aerobic/F and Anaerobic/F blood culture bottles. Ten milliliters of blood and a suspension of each isolate containing 1,000 CFU were introduced into each bottle and then incubated at 35°C in the BACTEC 9240 system. The system detected growth in 56 of 100 bottles. Four isolates did not have growth detected in either bottle after 21 days of incubation, resulting in four missed episodes of candidemia. If the blood culture bottles had been incubated for 5 days, an additional episode of candidemia would have remained undetected. If the bottles had been incubated for only 3 days, another episode would have been missed, resulting in up to six missed episodes of candidemia (four Candida glabrata isolates, one C. albicans isolate, and one Candida rugosa isolate). Terminal subculture of bottles without detected growth recovered yeast in 93% (41 of 44) of the bottles, representing 41 false negatives. In bottles where growth was detected, the time to detection was ∼24 h. However, the mean time to growth detection for C. glabrata isolates in anaerobic medium was 22.14 ± 2.47 h, but it was 120.89 ± 35.33 h in aerobic medium (P < 0.001). The BACTEC 9240 system detected growth of most Candida isolates; however, the delayed time to detection of C. glabrata is clinically significant. Given the high rate of false negatives, terminal subcultures may be helpful in certain situations.

Direct Isolation of Candida spp. from Blood Cultures on the Chromogenic Medium CHROMagar Candida

ABSTRACT CHROMagar Candida is a selective and differential chromogenic medium that has been shown to be useful for identification of Candida albicans, Candida krusei, Candida tropicalis, and perhaps Candida glabrata. Colony morphology and color have been well defined when CHROMagar Candida has been used to isolate yeast directly from clinical specimens, including stool, urine, respiratory, vaginal, oropharyngeal, and esophageal sources. Direct isolation of yeast on CHROMagar Candida from blood cultures has not been evaluated. We evaluated whether the color and colony characteristics produced by Candida spp. on CHROMagar Candida were altered when yeasts were isolated directly from blood cultures. Fifty clinical isolates of Candida were inoculated into aerobic and anaerobic blood culture bottles and incubated at 35°C in an automated blood culture system. When growth was detected, an aliquot was removed and plated onto CHROMagar Candida. As a control, CHROMagar Candida plates were inoculated with the same isolate of yeast grown on Sabouraud dextrose agar simultaneously. No significant difference was detected in color or colony morphology between the blood and control isolates in any of the tested organisms. All C. albicans (n = 12), C. tropicalis (n = 12), C. glabrata (n = 9), and C. krusei (n = 5) isolates exhibited the expected species-specific colony characteristics and color, whether isolated directly from blood or from control cultures. CHROMagar Candida can be reliably used for direct isolation of yeast from blood cultures. Direct isolation could allow mycology laboratories to more rapidly identify Candida spp., enable clinicians to more quickly make antifungal agent selections, and potentially decrease patient morbidity and mortality.

Detection of Fifteen Species of Candida in an Automated Blood Culture System

ABSTRACT Candidemia was simulated with 15 Candida spp. by using an automated blood culture system. Candida growth was detected in 479/648 (74%) bottles: 211/216 (98%) aerobic bottles, 58/216 (27%) anaerobic bottles, and 210/216 (97%) mycology bottles. Only the growth of Candida lipolytica failed to be detected in all media.

Effect of Inoculum Size on Detection of Candida Growth by the BACTEC 9240 Automated Blood Culture System Using Aerobic and Anaerobic Media

ABSTRACT Simulated candidemia was produced with 20 Candida isolates at three inoculum sizes (100, 10, and 1 CFU/ml of blood). Growth detection was better with larger inocula. The time to growth detection was shorter with larger inocula. Inoculum size does effect Candida growth detection and time to detection in BACTEC 9240 automated systems.

An Approach to Prevention of Infectious Diseases during Military Deployments

The US military conducts missions that range from major ground combat operations to disaster and humanitarian relief efforts. A primary goal of military medical professionals is disease prevention, which can be made more difficult in the context of short preparation times and prolonged deployment duration. The military uses a 6-component approach to deployment medicine, emphasizing preparation, education, personal protective measures, vaccines, chemoprophylaxis, and surveillance in an attempt to prevent infectious diseases. Many of the components of military deployment medicine are applicable to civilian disaster relief and humanitarian missions.

Travel Health Information at Commercial Travel Websites

BACKGROUND Internet travel purchases accounted for 10% of the travel industry revenue generated in 2001. To ensure that travelers remain healthy during excursions to developing countries, travel health information needs to be available at commercial travel websites. We evaluated the current availability of travel health information at these websites. METHODS The existence, adequacy and ease of access of the travel health information provided on commercial travel websites was assessed through a review of the top 25 airline and 20 discount travel websites. Each site was examined to determine whether it provided general information, such as jet lag, or international travel health information, such as malaria prophylaxis. We also assessed hyperlinks to external travel health information websites, such as the CDC, when provided. RESULTS Travel health information was not available at 20 (44%) commercial travel websites, including 36% of airline and 55% of the discount travel websites. Twenty-eight percent of airline websites contained general information only, 8% links only, and 28% general and international information. Travel health information available at discount travel websites included 10% general only, 30% link only, and 5% general and international information. On average, it took three clicks to access travel health information. Keywords clicked to access travel health information frequently did not obviously refer to health. Each of the six travel health website links provided accurate vaccine and travel health information. However, several links lacked disease-specific maps and details of disease risk (i.e. seasonal and regional variations of malaria risk). CONCLUSIONS Travel health information on commercial travel websites may be the only data available to travelers purchasing online. The information currently provided is generally inadequate. Ideally, commercial travel websites would provide uniform information that is accurate and easily accessible. Internationally recognized organizations should consider establishing guidelines for the information provided on commercial travel websites.

Minocycline Therapy for Traumatic Wound Infections Caused by the Multidrug-resistant acinetobacter baumannii-acinetobacter calcoaceticus Complex

The Acinetobacter baumannii-Acinetobacter calcoaceticus complex has become an important cause of traumatic wound infections in US Army soldiers injured in Iraq. Treatment options for these infections are limited by the organisms ability to acquire broad antimicrobial resistance. Alternative antimicrobial agents that are safe and well tolerated are needed. Minocycline has activity against Acinetobacter and has been used by some in the treatment of pneumonia caused by this pathogen. We report a case series of 8 patients treated with minocycline for traumatic wound infections caused by the multidrug-resistant A. baumannii-A. calcoaceticus complex. Minocycline therapy led to clinical cure for 7 of these patients. The remaining patient experienced adverse effects from minocycline requiring a change in therapy. Minocycline is an alternative agent that may be an effective therapy for multidrug-resistant A. baumannii-A. calcoaceticus complex.

The remote diagnosis of malaria using telemedicine or e-mailed images.

We determined the ability of blinded remote expert microscopy to identify malaria parasites through transmission of malaria smear images via telemedicine and as e-mail attachments. Protocols for malaria smear transmission included: (1) transmission of sender-selected televised smears at various bandwidths (Bw), (2) transmission of remote reader-directed televised smears at various Bw, and (3) transmission of digital photomicrographs as e-mail attachments. Twenty (14%) of 147 sender-selected, and 13 (6%) of 221 reader-directed, images were deemed unreadable by slide readers. The presence or absence of malaria was correctly identified in 98% of the remaining images. Sixty-four (34%) of 190 digital microphotographs were deemed unreadable, while the presence or absence of malaria was correctly identified in 100% of the remaining images. Correct speciation ranged from 45% to 83% across various transmission methods and Bw. The use of telemedicine and e-mail technology shows promise for the remote diagnosis of malaria.