Staphylococcus aureus colonization of healthy military service members in the United States and Afghanistan.

BACKGROUND: Staphylococcus aureus [methicillin-resistant and methicillin-susceptible (MRSA/MSSA)] is a leading cause of infections in military personnel, but there are limited data regarding baseline colonization of individuals while deployed. We conducted a pilot study to screen non-deployed and deployed healthy military service members for MRSA/MSSA colonization at various anatomic sites and assessed isolates for molecular differences. METHODS: Colonization point-prevalence of 101 military personnel in the US and 100 in Afghanistan was determined by swabbing 7 anatomic sites. US-based individuals had received no antibiotics within 30 days, and Afghanistan-deployed personnel were taking doxycycline for malaria prophylaxis. Isolates underwent identification and testing for antimicrobial resistance, virulence factors, and pulsed-field type (PFT). RESULTS: 4 individuals in the US (4 isolates- 3 oropharynx, 1 perirectal) and 4 in Afghanistan (6 isolates- 2 oropharynx, 2 nare, 1 hand, 1 foot) were colonized with MRSA. Among US-based personnel, 3 had USA300 (1 PVL+) and 1 USA700. Among Afghanistan-based personnel, 1 had USA300 (PVL+), 1 USA800 and 2 USA1000. MSSA was present in 40 (71 isolates-25 oropharynx, 15 nare) of the US-based and 32 (65 isolates- 16 oropharynx, 24 nare) of the Afghanistan-based individuals. 56 (79%) US and 41(63%) Afghanistan-based individuals had MSSA isolates recovered from extra-nare sites. The most common MSSA PFTs were USA200 (9 isolates) in the US and USA800 (7 isolates) in Afghanistan. MRSA/MSSA isolates were susceptible to doxycycline in all but 3 personnel (1 US, 2 Afghanistan; all were MSSA isolates that carried tetM). CONCLUSION: MRSA and MSSA colonization of military personnel was not associated with deployment status or doxycycline exposure. Higher S. aureus oropharynx colonization rates were observed and may warrant changes in decolonization practices.

Multidrug-resistant gram-negative bacteria colonization of healthy US military personnel in the US and Afghanistan.

BACKGROUND: The US military has seen steady increases in multidrug-resistant (MDR) gram-negative bacteria (GNB) infections in casualties from Iraq and Afghanistan. This study evaluates the prevalence of MDR GNB colonization in US military personnel. METHODS: GNB colonization surveillance of healthy, asymptomatic military personnel (101 in the US and 100 in Afghanistan) was performed by swabbing 7 anatomical sites. US-based personnel had received no antibiotics within 30 days of specimen collection, and Afghanistan-based personnel were receiving doxycycline for malaria chemoprophylaxis at time of specimen collection. Isolates underwent genotypic and phenotypic characterization. RESULTS: The only colonizing MDR GNB recovered in both populations was Escherichia coli (p=0.01), which was seen in 2% of US-based personnel (all perirectal) and 11% of Afghanistan-based personnel (10 perirectal, 1 foot+groin). Individuals with higher off-base exposures in Afghanistan did not show a difference in overall GNB colonization or MDR E. coli colonization, compared with those with limited off-base exposures. CONCLUSION: Healthy US- and Afghanistan-based military personnel have community onset-MDR E. coli colonization, with Afghanistan-based personnel showing a 5.5-fold higher prevalence. The association of doxycycline prophylaxis or other exposures with antimicrobial resistance and increased rates of MDR E. coli colonization needs further evaluation.

Detection of methicillin-resistant and methicillin-susceptible Staphylococcus aureus colonization of healthy military personnel by traditional culture, PCR, and mass spectrometry.

BACKGROUND: Methicillin-resistant (MRSA) and methicillin-susceptible (MSSA) Staphylococcus aureus colonization is associated with increased rates of infection. Rapid and reliable detection methods are needed to identify colonization of nares and extra-nare sites, particularly given recent reports of oropharynx-only colonization. Detection methods for MRSA/MSSA colonization include culture, PCR, and novel methods such as PCR/electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS). METHODS: We evaluated 101 healthy military members for S. aureus colonization in the nares, oropharynx, axilla, and groin, using CHROMagar S. aureus medium and Xpert SA Nasal Complete PCR for MRSA/MSSA detection. The same subjects were screened in the nares, oropharynx, and groin using PCR/ESI-TOF-MS. RESULTS: By culture, 3 subjects were MRSA-colonized (all oropharynx) and 34 subjects were MSSA-colonized (all 4 sites). PCR detected oropharyngeal MRSA in 2 subjects, which correlated with culture findings. By PCR, 47 subjects were MSSA-colonized (all 4 sites); however, 43 axillary samples were invalid, 39 of which were associated with deodorant/anti-perspirant use (93%, p < 0.01). By PCR/ESI-TOF-MS, 4 subjects were MRSA-colonized, 2 in the nares and 2 in the oropharynx; however, neither of these correlated with positive MRSA cultures. Twenty-eight subjects had MSSA by PCR/ESI-TOF-MS, and 41 were found to have possible MRSA (S. aureus with mecA and coagulase-negative Staphylococcus (CoNS)). CONCLUSION: The overall 3% MRSA colonization rate is consistent with historical reports, but the oropharynx-only colonization supports more recent findings. In addition, the use of deodorant/anti-perspirant invalidated axillary PCR samples, limiting its utility. Defining MRSA positivity by PCR/ESI-TOF-MS is complicated by co-colonization of S. aureus with CoNS, which can also carry mecA.

Septic subacromial bursitis caused by Mycobacterium kansasii in an immunocompromised host.

Mycobacterium kansasii is a common cause of pulmonary infection as a result of nontuberculous mycobacteria, but is less commonly described as a cause of an orthopedic infection. We present the first case of M. kansasii subacromial septic bursitis in an immunocompromised host. This case demonstrates the diagnostic and treatment challenges associated with orthopedic infections caused by M. kansasii.

Fatal Actinomucor elegans var. kuwaitiensis infection following combat trauma.

We report the first case of invasive mucormycosis secondary to Actinomucor elegans infection. A severely injured soldier with a fatal A. elegans var. kuwaitiensis infection is described. The identification of this fungus was performed by classical and molecular methods, and this report documents the pathogenicity of the recently described variety Actinomucor elegans var. kuwaitiensis.

Adenovirus-Associated Acute Appendicitis: An Under-Recognized Relationship?

OBJECTIVE: Acute appendicitis (AA) is one of the most common causes of a surgical abdomen worldwide, occurring most frequently in those age 10 to 29 years. Adenovirus (ADV) is a rare but reported cause of AA in children and a well-recognized cause of intussusception in infants and young children. Annually, about 36,000 basic military trainees (BMTs) undergo initial training at Joint Base San Antonio Lackland, Texas. Before reintroduction of the ADV 4/7 vaccine in November 2011, one-third of BMTs developed an adenoviral upper respiratory tract infection (URI) during the 8.5 weeks of training. We hypothesized that ADV may be a common cause of AA in the BMT population given their young age and high incidence of adenoviral URIs. The objective of this study was to determine the frequency with which ADV, cytomegalovirus (CMV), Epstein-Barr virus (EBV), and enterovirus were associated with AA in a population of young adults. MATERIALS AND METHODS: This study was a retrospective review of patient charts and existing pathological tissue specimens of all BMTs who underwent appendectomy at the Wilford Hall Medical Center from January 1, 2003, to August 31, 2011. Pathological tissue samples from 112 BMTs were assayed by quantitative polymerase chain reaction (qPCR) and immunohistochemistry (IHC) for viral targets. RESULTS: ADV DNA was detected in 16 of 112 samples (14%) via qPCR: ADV 4 in 13 cases, ADV B14 in 1 case, and nontypable ADV in 2 cases. IHC was positive in only the ADV B14 case (0.9%). All cases were negative for CMV, EBV, and enterovirus. CONCLUSION: By using qPCR, this study demonstrated an association between ADV and AA higher than has been previously reported: ADV was detected in 14% of AA cases in this series versus in only 0.23% of AA cases in previous studies (p < 0.01). There was no evidence of CMV, EBV, or enterovirus association with AA in this study. Comparison of qPCR to IHC shows that histologic analysis may overlook evidence of ADV in appendiceal tissue: qPCR is significantly more sensitive than light microscopy and IHC for detecting ADV in this setting. Because ADV 4 was detected in 81% of those with positive qPCR, the recently licensed live oral ADV vaccine might be useful for primary prevention against AA. Prospective studies evaluating young adults presenting with AA for evidence of infection with ADV are needed to determine if a causal relationship exists.

Prevalence and Seroprevalence of Trypanosoma cruzi Infection in a Military Population in Texas.

Recent biosurveillance findings at Joint Base San Antonio (JBSA), a large military installation located in south-central Texas, indicate the potential for vector-borne human Chagas disease. A cross-sectional study was conducted to determine the prevalence and seroprevalence of Trypanosoma cruzi infection in highest risk subpopulations on the installation, including students and instructors who work and sleep in triatomine-endemic field settings. Real-time polymerase chain reaction, enzyme-linked immunosorbent assay, and indirect immunofluorescent antibody assay were performed on enrolled subjects (N = 1,033), none of whom tested positive for T. cruzi or anti-T. cruzi antibodies. Current countermeasures used during field training on JBSA appear to be sufficient for preventing autochthonous human Chagas disease.

A single-center, six-year evaluation of the role of pulsed-field gel electrophoresis in suspected burn center outbreaks.

INTRODUCTION: Pulsed-field gel electrophoresis (PFGE) has been used as an adjunct to traditional hospital epidemiology in numerous outbreak investigations, including in burn centers. However, its most effective real-world application remains unclear, with few longitudinal descriptions of use. SETTING AND METHODS: A 425 bed military tertiary hospital with a 40 bed burn center, from July 2007 to July 2013; retrospective evaluation of hospital infection prevention records was performed and results of PFGE where used in outbreak investigation. RESULTS: Twenty-two inquiries for suspected outbreaks were performed. 418 isolates were collected from 168 subjects during this time. 325 (78%) of the isolates originated from the burn intensive care unit. 17 inquiries were for gram-negative bacteria, comprised of 5 for Acinetobacter baumannii-calcoaceticus complex, 4 Klebsiella pneumoniae, 3 Stenotrophomonas maltophilia, 2 Pseudomonas aeruginosa, and 1 of each of the following: Enterobacter cloacae, Raoultella planticola, and Aeromonas hydrophila. The other 5 inquiries were specifically for Staphylococcus aureus. The majority of investigations revealed a combination of clonal and non-clonal isolates, and in no instance did PFGE contribute to targeting of interventions. CONCLUSION: PFGE contributed little to infection prevention interventions, and outbreaks resolved with increased focus on basic practices. Longitudinal studies including greater numbers of outbreaks in different settings are needed to clarify the utility of molecular typing in routine investigations.

In vitro toxicity and activity of Dakin's solution, mafenide acetate, and amphotericin B on filamentous fungi and human cells.

OBJECTIVES: Posttraumatic invasive fungal infections threaten critically injured combat-related injuries and require a combination of extensive surgery and systemic antifungal therapy, along with topical antimicrobials used adjunctively to control the infection. We evaluated the in vitro activity of topical agents in varying combinations and concentrations against molds from patients that were responsible for wound invasive fungal infections and the topical agents' toxicity to human cells. METHODS: Mafenide acetate solutions (2.5%, 5%, and 7.5%), amphotericin B solutions (2 µg/mL, 2 mg/mL, and 20 mg/mL), SMAT (5% mafenide acetate in combination with 2 µg/mL, 2 mg/mL, and 20 mg/mL amphotericin B), and Dakin's solutions (buffered sodium hypochlorite) (0.5%, 0.25%, and 0.125% and 10-fold serial dilutions of 0.25%-0.00000025%) were evaluated for antifungal activity against 4 molds using a time-kill assay using standard conidial suspensions of 5 × 10(4) colony-forming units per milliliter. To assess cellular toxicity, confluent monolayers of human keratinocytes, dermal fibroblasts, and osteoblasts were exposed to these topical agents. Based upon efficacy and toxicity ratios, an additional 10 molds were screened with selected concentrations of the topical agents for antifungal activity and toxicity. RESULTS: All the topical agents seemed to have a dose-dependent killing with only mafenide acetate showing time killing associated with prolonged contact. There was overall evidence of dose-dependent cytotoxicity of the various topical agents against the various cell lines tested, but there did not seem to be increased cell death with continued exposure to the agents over time. Dakin's solution exhibited dose-dependent toxicity and efficacy with 0.00025% appearing to optimize those parameters. CONCLUSIONS: Mafenide acetate and amphotericin B did not seem to persistently meet the toxicity and efficacy balance as consistently as Dakin's solution.

Efficacy of minocycline and tigecycline in a hamster model of leptospirosis.

Leptospirosis is a widespread zoonotic infection characterized by acute febrile illness. Severely ill patients may require empiric treatment with broad-spectrum antibiotics prior to definitive diagnosis. We evaluated the efficacy of minocycline and tigecycline against leptospirosis in a hamster model. Hamsters were treated with either minocycline (5, 10, or 25 mg/kg per day) or tigecycline (5, 10, or 25 mg/kg per day) for 5 days. Controls included untreated animals and doxycycline-treated animals (5 mg/kg per day). Nine days after infection, all untreated animals were dead. All treated hamsters survived to the end of study (day 21). Study groups showed significantly improved survival compared to the untreated group (P < .01). Minocycline and tigecycline showed survival benefit comparable to the standard treatment, doxycycline. In the absence of doxycycline, minocycline may be considered as an alternative, while tigecycline may be useful in the management of severely ill patients prior to a definitive diagnosis.