David P. Dooley

Natural History of Community-Acquired Methicillin-Resistant Staphylococcus aureus Colonization and Infection in Soldiers

BACKGROUND Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) is an emerging pathogen for which the prevalence, risk factors, and natural history are incompletely understood. METHODS In this prospective observational study, we evaluated 812 US Army soldiers to determine the prevalence of and risk factors for CA-MRSA colonization and the changes in colonization rate over time, as well as to determine the clinical significance of CA-MRSA colonization. Demographic data and swab samples from the nares for S. aureus cultures were obtained from participants at the start of their training and 8-10 weeks later. Over this time period, participants were observed prospectively to monitor for soft-tissue infections. S. aureus isolates were characterized by in vitro examination of antibiotic susceptibilities, mecA confirmation, pulsed-field gel electrophoresis, and Panton-Valentine leukocidin (PVL) gene testing. RESULTS At the initial sampling, 24 of the participants (3%) were colonized with CA-MRSA, 9 of whom (38%) developed soft-tissue infections during the study period. In contrast, 229 participants (28%) were colonized with methicillin-susceptible S. aureus (MSSA), 8 (3%) of whom developed clinical infections during the same period (relative risk, 10.7; 95% confidence interval, 4.6-25.2; P<.001). At follow-up culture, the CA-MRSA colonization rate dropped to 1.6% without eradication efforts. Previous antibiotic use was a risk factor for CA-MRSA colonization at the initial sampling (P=.03). PVL genes were detected in 66% of 45 recovered CA-MRSA isolates, including all 9 clinical isolates available for analysis. Of subjects hospitalized, 5 of 6 had PVL-positive CA-MRSA infections. CONCLUSIONS CA-MRSA colonization with PVL-positive strains was associated with a significant risk of soft-tissue infection, suggesting that CA-MRSA may be more virulent than MSSA. Previous antibiotic use may play a role in CA-MRSA colonization.

Bacteriology of War Wounds at the Time of Injury

Bacterial contamination of war wounds occurs either at the time of injury or during the course of therapy. Characterization of the bacteria recovered at the time of initial trauma could influence the selection of empiric antimicrobial agents used to prevent infection. In the spring of 2004, U.S. military casualties who presented to the 31st Combat Support Hospital in Baghdad, Iraq, with acute traumatic injuries resulting in open wounds underwent aerobic culture of their wounds to identify the bacteria colonizing the wounds. Forty-nine casualties with 61 separate wounds were evaluated. Wounds were located predominantly in the upper and lower extremities and were primarily from improvised explosive devices or mortars. Thirty wounds (49%) had bacteria recovered on culture, with 40 bacteria identified. Eighteen casualties (20 wounds) had undergone field medical therapy (irrigation and/or antimicrobial treatment); six of these had nine bacterial isolates on culture. Of the 41 wounds from 31 patients who had received no previous therapy, 24 grew 31 bacteria. Gram-positive bacteria (93%), mostly skin-commensal bacteria, were the predominant organisms identified. Only three Gram-negative bacteria were detected, none of which were characterized as broadly resistant to antimicrobial agents. The only resistant bacteria recovered were two isolates of methicillin-resistant Staphylococcus aureus (MRSA). Our assessment of war wound bacterioly soon after injury reveals a predominance of Gram-positive organisms of low virulence and pathogenicity. The presence of MRSA in wounds likely reflects the increasing incidence of community-acquired MRSA bacteria. These data suggest that the use of broad-spectrum antibiotics with efficacy against more resistant, Gram-negative bacteria, such as Pseudomonas aeruginosa and Acinetobacter spp., is unnecessary in early wound management.

Bacteria Recovered from Patients Admitted to a Deployed U.S. Military Hospital in Baghdad, Iraq

The predominant bacteria and antimicrobial susceptibilities were surveyed from a deployed, military, tertiary care facility in Baghdad, Iraq, serving U.S. troops, coalition forces, and Iraqis, from August 2003 through July 2004. We included cultures of blood, wounds, sputum, and urine, for a total of 908 cultures; 176 of these were obtained from U.S. troops. The bacteria most commonly isolated from U.S. troops were coagulase-negative staphylococci, accounting for 34% of isolates, Staphylococcus aureus (26%), and streptococcal species (11%). The 732 cultures obtained from the predominantly Iraqi population were Klebsiella pneumoniae (13%), Acinetobacter baumannii (11%), and Pseudomonas aeruginosa (10%); coagulase-negative staphylococci represented 21% of these isolates. These differences in prevalence were all statistically significant, when compared in chi2 analyses (p < 0.05). Antimicrobial susceptibility testing demonstrated broad resistance among the Gram-negative and Gram-positive bacteria.

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.

Persistence of Pigment Production by Yeast Isolates Grown on CHROMagar Candida Medium

ABSTRACT We evaluated the persistence of pigmentation in yeast isolates grown on the chromogenic medium CHROMagar Candida over 7 days. Candida, Cryptococcus, and Trichosporon isolates were inoculated alone or mixed onto duplicate sets of plates and incubated at 30 and 35°C. Candida albicans and Candida krusei were readily identified throughout the reading period, but Candida glabrata was difficult to differentiate from other species until the 3- or 4-day time point. Candida tropicalis produced colonies similar to those of rare Cryptococcus and Trichosporon species, and mixed cultures were often difficult to identify as such.

Development of Quinolone-Resistant Campylobacter fetus Bacteremia in Human Immunodeficiency Virus-Infected Patients

Campylobacter fetus subspecies fetus has been recognized as a cause of systemic illness in immunocompromised hosts, including relapsing bacteremia in human immunodeficiency virus (HIV)-infected patients. Acquired resistance to quinolone therapy, while reported for a variety of bacteria, including Campylobacter jejuni, has not been previously documented for C. fetus. Two cases of quinolone-resistant C. fetus bacteremia were detected in HIV-infected patients. Cloning and nucleotide sequencing of the C. fetus gyrA gene in the 2 resistant isolates demonstrated a G-to-T change that led to an Asp-to-Tyr amino acid substitution at a critical residue frequently associated with quinolone resistance. In addition, comparison of the pre- and posttreatment isolates from 1 patient documented outer membrane protein changes temporally linked with the development of resistance. Relapsing C. fetus infections in quinolone-treated HIV-infected patients may be associated with the acquisition of resistance to these agents, and this resistance may be multifactorial.

Outcomes of community-acquired, methicillin-resistant Staphylococcus aureus, soft tissue infections treated with antibiotics other than vancomycin.

Community-acquired, methicillin-resistant Staphylococcus aureus (cMRSA), soft tissue infections are becoming increasingly prevalent in the outpatient setting. Few studies have been specifically designed to examine the efficacy of oral antibiotic therapy for these infections. We performed an observational study to determine the effect of alternative, orally administered antibiotics on cMRSA soft tissue infections. Consecutive patients between January 2001 and March 2004 who had skin or soft tissue infections from which cMRSA was isolated and who had never received vancomycin were studied through retrospective and concurrent review. Primary outcome measures were improvement or resolution of infection 5 and 14 days after initiation of treatment with orally administered antibiotics and rates of recurrence within 30 days after completion of treatment. Thirty subjects met the inclusion criteria. Twenty-one subjects received either clindamycin, trimethoprim/sulfamethoxazole, doxycycline/minocycline, or a fluoroquinolone. Five subjects received a beta-lactam antibiotic with abscess drainage, and four subjects underwent abscess drainage alone. Improvement was noted for all subjects at 5 days, complete resolution of infection occurred for all subjects by 14 to 17 days, and in no case did relapse occur within 30 days. cMRSA skin and soft tissue infections can be successfully treated with orally administered antibiotics to which the organism has demonstrable in vitro susceptibility.

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.

Effect of Maximizing a Travel Medicine Clinic—s Prevention Strategies

BACKGROUND Even among travelers who undergo evaluation in travel medicine clinics, illnesses develop despite the emphasis placed on prevention. It is possible that travel-associated disease rates may be modified by maximizing access to care and augmenting educational methods of disease prevention. Use of alternative preventive measures such as alcohol hand gel sanitizers may also alter illnesses among travelers. METHODS We assessed medical outcomes in a travel population cared for in the setting of free vaccinations, medications, and travel medicine consultation, in which personal preventive measures were presented in numerous formats by a physician specializing in infectious diseases. An initial demographic questionnaire was administered at the time of travel consultation. A post-travel telephone interview conducted 2 weeks after return from travel evaluated illness while abroad, illness upon return, and adherence to travel recommendations. An assessment was also performed regarding the utility of an alcohol hand gel sanitizer. RESULTS One hundred fifty-five travelers were evaluated (primarily older, well-educated US-born travelers, on vacation with family or coworkers). Travelers filled their prescriptions 98% of the time; 77% reported adherence to antimalarial chemoprophylaxis. Sixty-four percent of travelers developed illness abroad, and 20% developed illness upon return. The most frequent complaints were diarrhea and upper respiratory illness. Ten percent of travelers altered their itinerary owing to illness. The use of alcohol hand gel sanitizers did not appear to impact the development of diarrhea or respiratory illnesses. CONCLUSION In this small group of travelers, access to free consultation, vaccinations, and medications along with presentation of personal protective measures in various formats did not seem to influence the development of illnesses among travelers. Although not rigorously analyzed, alcohol hand gel sanitizers did not seem to alter diarrhea or respiratory tract illness rates. These data highlight the need for new or more effective methods to prevent illness among travelers.