Will Antigen Testing Remain Relevant in the Point-of-Care Testing Environment?

Before the molecular age, cell culture was the gold standard for confirmatory diagnosis of viral and atypical infectious diseases. Typical cell culture methodologies are costly, require days (or weeks) for results, and require significant technical expertise. As a result, cell culture is impractical for timely diagnostic testing in most of the health care environments. Traditional bacterial culture methods, also have disadvantages due to the need for incubation, subsequent identification of pathogens, and significant technical expertise. This article discusses the general considerations of antigen and molecular assays and the merits and factors to consider when implementing diagnostic assays for several common pathogens.

Murine Typhus Presenting With Mucosal Involvement.

Lipschutz ulcers (LU) present as painful genital ulcers in nonsexually active females. Associated infections include Epstein Barr virus, Mycoplasma pneumoniae, Cytomegalovirus, and influenza. To our knowledge, this is the first report of LU occurring with murine typhus. Murine typhus is caused by Rickettsia typhi, a Gram-negative, obligate intracellular organism. Rat fleas (Xenopsylla cheopis) are the classic vector, although cat fleas (Ctenocephalides felis) found on cats, dogs, and opossums have been implicated in maintaining the life cycle of R. typhi in suburban areas. Murine typhus can have a nonspecific presentation making a strong index of suspicion crucial to its diagnosis. The most common presenting signs include fever, poor appetite, malaise, and headache. Laboratory abnormalities may include elevated C-reactive protein, elevated erythrocyte sedimentation rate, hypoalbuminemia, elevated transaminases, elevated neutrophil band count, and thrombocytopenia. The treatment of choice for R. typhi is doxycycline.

Economic Evaluation: Onsite HSV PCR Capabilities for Pediatric Care.

OBJECTIVE: Herpes simplex virus (HSV) encephalitis has an overall mortality rate of 11%-29% with treatment. Although rare, HSV encephalitis is frequently tested for and empirically treated, especially in the neonatal population. HSV infection can be diagnosed with polymerase chain reaction (PCR) testing, although this frequently requires sending samples to reference laboratories. The inherent delay in results may lead to prolonging empiric treatment and hospital stay, resulting in increased costs. This study investigates whether onsite HSV PCR testing decreases hospitalization duration, acyclovir treatment duration, and financial cost on an institution. PROJECT DESIGN: This single-center project utilized the IHI model for improvement to evaluate third-party HSV PCR processing versus an implemented onsite PCR-based meningitis-encephalitis panel for HSV central nervous system evaluation. The primary outcome was hospital cost differential with secondary outcomes, including duration of acyclovir administration and time to result. RESULTS: We identified 96 children age 0-18 from 2010 to 2016, 74 patients utilizing offsite third-party testing, and 22 patients utilizing onsite. We observed a per-patient cost savings of $428 ($618.43-$190.43, P = 0.029) upon the implementation of onsite testing. The mean duration of acyclovir therapy decreased from 3.7 to 0.26 days per patient (P < 0.001). Time to result decreased from 4.6 to 0.13 days (P < 0.001). CONCLUSIONS: Acquisition of real-time local HSV PCR capabilities significantly decreased time to result and empiric medication use while significantly reducing hospital costs in a military treatment facility.

Improvement in adherence to antibiotic duration of therapy recommendations for uncomplicated cystitis: a quasi-experimental study.

BACKGROUND: Acute uncomplicated cystitis is one of the most common diagnoses for which antibiotic treatment is prescribed in the outpatient setting. Despite the availability of national guidelines, there remains a wide pattern in prescriber choices for therapy. Recent data portray a picture of consistently longer durations than recommended prescribed in outpatient settings. OBJECTIVE: The objective was to evaluate the effect of a system-based intervention on adherence to guideline-recommended durations of therapy for uncomplicated cystitis in the outpatient setting. METHODS: This quasi-experimental study included women aged 18-64 years who were seen at five family medicine clinics at an academic medical centre and were prescribed targeted antibiotics for uncomplicated cystitis (nitrofurantoin monohydrate/macrocrystals 100 mg, trimethoprim-sulfamethoxazole 160/800 mg or ciprofloxacin 250 mg). The intervention involved revising or adding pre-filled, but modifiable, default prescribing instructions in the electronic health record (EHR) for the targeted antibiotics. We evaluated adherence to guideline-recommended duration of therapy as well as days of therapy (DOT) before and after the intervention. RESULTS: A total of 787 pre-intervention and 862 post-intervention cases were included. Adherence to recommended duration of therapy increased from 29.4% to 76.3% (P < 0.01). The average DOT decreased by 23% from 6.6 to 5.1 (P < 0.01). CONCLUSION: A stewardship intervention consisting of revising/adding default prescribing instructions to targeted antimicrobials in an EHR was associated with increased adherence to recommended durations of therapy for uncomplicated cystitis and reduction of unnecessary antibiotic exposure. More studies are needed to confirm effectiveness across multiple medical record platforms.

Nephrogenic diabetes insipidus in a 15-year-old Hispanic female with a novel AQP2 mutation.

Nephrogenic diabetes insipidus (NDI) is a rare inherited disorder most often caused by mutations in the arginine-vasopressin receptors or aquaporin channels, which subsequently impairs the water reabsorption in the kidney. This case report describes a 15-year-old female diagnosed with NDI after an acute gastroenteritis and multiple fluid boluses leading to intractable emesis. Gene testing reveals our patient is compound heterozygous for novel AQP2 gene mutations with a cytosine-to-thymine substitution at nucleotide position 277 and adenine-to-cytosine substitution at nucleotide position 659. Therefore, we report a novel AQP2 gene mutation in an adolescent patient which is outside the common age for diagnosis.

Right Middle Lobe Collapse and Pleural Effusion in an 18-Year-Old Man.

An 18-year-old African American male subject presented to an acute care clinic with 3 days of productive cough, chills, pleuritic right chest pain, sore throat with hoarseness, congestion, and intermittent shortness of breath. He recently relocated to Texas from Georgia to undergo basic military training. He denied any other recent travel or contact with persons with pulmonary TB or other respiratory illnesses. His medical history was significant for glucose-6-phosphate dehydrogenase deficiency and sickle cell trait.

Tolerability of Japanese Encephalitis Vaccine in Pediatric Patients.

BACKGROUND.: Japanese encephalitis virus (JEV) is a mosquito-borne flavivirus endemic to parts of Asia. Manufacture of JE-VAX, the mouse brain-derived vaccine against JEV, was discontinued in February 2011. IXIARO, an inactivated cell culture-derived vaccine, was approved in 2009 for use in adult patients. Although IXIARO was not licensed for pediatric patients until 2013, our clinic routinely used this vaccine in at-risk children starting in 2011. The purpose of this study was to review our experience as to the tolerability of the new IXIARO vaccine in children. METHODS.: We performed a retrospective chart review of all patients less than 18 years of age who received at least 1 dose of IXIARO in our Family Travel Clinic from November 2011 through August 2014. Subjects' electronic medical records were reviewed for any documented medical visits within 3 months after vaccination. Each visit was assessed for possible adverse events with relationship to vaccine administration as determined by the reviewer. RESULTS.: Ninety-two patients less than 18 years of age received a total of 145 doses of IXIARO between November 2011 and August 2014. Seven adverse events were documented. Only 1 was deemed to be possibly related. No serious adverse events were found on chart review. CONCLUSIONS.: Our study reinforces the recent decision to expand IXIARO vaccination to the pediatric population. The experience in our clinic since vaccine introduction shows it to be overall tolerable when used in routine clinical practice. Practitioners should feel comfortable recommending vaccination against JEV for any pediatric traveler to an area of risk.

Changing Susceptibility of Staphylococcus aureus in a US Pediatric Population.

BACKGROUND: Staphylococcus aureus is a major cause of infection in both adult and pediatric populations. After several decades of increasing prevalence, the proportion of S aureus infections due to methicillin-resistant S aureus has been reported to be in decline in adults. Data for similar changes in pediatric populations are limited. METHODS: Evaluation of S aureus susceptibility data for pediatric patients receiving care in the US Military Health System was performed. Microbiology and demographic data were collected for years 2005 through 2014. Trends in antibiotic susceptibility results were evaluated. Clinical and demographic characteristics were explored to assess for association with antibiotic susceptibilities. RESULTS: In this study, 41 745 S aureus isolates from 39 207 pediatric patients were included. An overall increase in susceptibility of isolates to oxacillin was noted over this 10-year period; with over 60% of isolates oxacillin-susceptible in 2014. S aureus susceptibility to clindamycin declined over the study period; notably methicillin-susceptible S aureus susceptibility to clindamycin declined from 90% to 83% (P < .0001). Differences in oxacillin susceptibility between US regions decreased over time. CONCLUSIONS: Similar to recent trends seen in adults, the proportion of pediatric S aureus infections secondary to methicillin-resistant S aureus appear to be decreasing, as is variability in US geographical resistance rates. Increasing clindamycin resistance among methicillin-susceptible S aureus should raise caution in the use of empirical clindamycin in presumed S aureus infection. Clinicians should be aware of regional susceptibility patterns when choosing empirical regimens.

IS5 element integration, a novel mechanism for rapid in vivo emergence of tigecycline nonsusceptibility in Klebsiella pneumoniae.

Tigecycline nonsusceptibility is concerning because tigecycline is increasingly relied upon to treat carbapenem- or colistin-resistant organisms. In Enterobacteriaceae, tigecycline nonsusceptibility is mediated by the AcrAB-TolC efflux pump, among others, and pump activity is often a downstream effect of mutations in their transcriptional regulators, cognate repressor genes, or noncoding regions, as demonstrated in Enterobacteriaceae and Acinetobacter isolates. Here, we report the emergence of tigecycline nonsusceptibility in a longitudinal series of multidrug-resistant (MDR) and extensively drug-resistant (XDR) Klebsiella pneumoniae isolates collected during tigecycline therapy and the elucidation of its resistance mechanisms. Clinical isolates were recovered prior to and during tigecycline therapy of a 2.5-month-old Honduran neonate. Antimicrobial susceptibility tests to tigecycline determined that the MIC increased from 1 to 4 µg/ml prior to the completion of tigecycline therapy. Unlike other studies, we did not find increased expression of ramA, ramR, oqxA, acrB, marA, or rarA genes by reverse transcription-quantitative PCR (qRT-PCR). Whole-genome sequencing revealed an IS5 insertion element in nonsusceptible isolates 85 bp upstream of a putative efflux pump operon, here named kpgABC, previously unknown to be involved in resistance. Introduction of the kpgABC genes in a non-kpgABC background increased the MIC of tigecycline 4-fold and is independent of a functional AcrAB-TolC pump. This is the first report to propose a function for kpgABC and identify an insertion element whose presence correlated with the in vivo development of tigecycline nonsusceptibility in K. pneumoniae.

Bacterial peritonitis due to Acinetobacter baumannii sequence type 25 with plasmid-borne new delhi metallo-ß-lactamase in Honduras.

A carbapenem-resistant Acinetobacter baumannii strain was isolated from the peritoneal fluid of a patient with complicated intra-abdominal infection and evaluated at the Multidrug-resistant Organism Repository and Surveillance Network by whole-genome sequencing and real-time PCR. The isolate was sequence type 25 and susceptible to colistin and minocycline, with low MICs of tigecycline. blaNDM-1 was located on a plasmid with >99% homology to pNDM-BJ02. The isolate carried numerous other antibiotic resistance genes, including the 16S methylase gene, armA.

Performance of five FDA-approved rapid antigen tests in the detection of 2009 H1N1 influenza A virus.

Rapid antigen tests are commonly used by clinicians for rapid, simple, point-of-care testing. Five rapid antigen tests were shown to have low sensitivity (40.3-58.8%) when compared to real-time RT-PCR using nasal wash specimens from patients with influenza-like-illness (N = 167) that were collected previously and confirmed as 2009 pandemic influenza A (H1N1)-positive by PCR. Rapid antigen test sensitivity correlated with virus levels in nasal secretions when comparisons were made to cycle threshold (C(T)) values obtained from real-time RT-PCR. When C(T) values are <25 (equating to viral concentrations of >10(4) TCID(50)/ml) sensitivity for all five rapid antigen kits was high (range: 83-94% positive); however, when C(T) values are >30 (10(2) TCID(50)/ml), sensitivities of only 16-18% were observed for four of five rapid antigen kits. The Directigen EZ Flu A + B test detected more positive samples (35%) at lower viral concentrations with C(T) values >30 when compared with other commercial kits (P = 0.05). Rapid antigen test results must be interpreted with caution, and negative specimens may need confirmation by sensitive molecular assays.

Executive summary: Guidelines for the prevention of infections associated with combat-related injuries: 2011 update: endorsed by the Infectious Diseases Society of America and the Surgical Infection Society.

Despite advances in resuscitation and surgical management of combat wounds, infection remains a concerning and potentially preventable complication of combat-related injuries. Interventions currently used to prevent these infections have not been either clearly defined or subjected to rigorous clinical trials. Current infection prevention measures and wound management practices are derived from retrospective review of wartime experiences, from civilian trauma data, and from in vitro and animal data. This update to the guidelines published in 2008 incorporates evidence that has become available since 2007. These guidelines focus on care provided within hours to days of injury, chiefly within the combat zone, to those combat-injured patients with open wounds or burns. New in this update are a consolidation of antimicrobial agent recommendations to a backbone of high-dose cefazolin with or without metronidazole for most postinjury indications and recommendations for redosing of antimicrobial agents, for use of negative pressure wound therapy, and for oxygen supplementation in flight.

Guidelines for the prevention of infections associated with combat-related injuries: 2011 update: endorsed by the Infectious Diseases Society of America and the Surgical Infection Society.

Despite advances in resuscitation and surgical management of combat wounds, infection remains a concerning and potentially preventable complication of combat-related injuries. Interventions currently used to prevent these infections have not been either clearly defined or subjected to rigorous clinical trials. Current infection prevention measures and wound management practices are derived from retrospective review of wartime experiences, from civilian trauma data, and from in vitro and animal data. This update to the guidelines published in 2008 incorporates evidence that has become available since 2007. These guidelines focus on care provided within hours to days of injury, chiefly within the combat zone, to those combat-injured patients with open wounds or burns. New in this update are a consolidation of antimicrobial agent recommendations to a backbone of high-dose cefazolin with or without metronidazole for most postinjury indications, and recommendations for redosing of antimicrobial agents, for use of negative pressure wound therapy, and for oxygen supplementation in flight.

High incidence of multidrug-resistant gram-negative bacteria recovered from Afghan patients at a deployed US military hospital.

OBJECTIVE: To investigate potential sources and risks associated with multidrug-resistant (MDR) bacteria in a deployed US military hospital. DESIGN: Retrospective analysis of factors associated with recovery of MDR bacteria, supplemented by environmental sampling. SETTING: The largest US military hospital in Afghanistan. PATIENTS: US and Afghan patients with positive bacterial culture results, from September 2007 through August 2008. METHODS: Microbiologic, demographic, and clinical data were analyzed. Potential risk factors included admission diagnosis or mechanism of injury, length of stay, gender, age, and nationality (US or Afghan). Environmental sampling of selected hospital high-touch surfaces and equipment was performed to help elucidate whether environmental MDR bacteria were contributing to nosocomial spread. RESULTS: A total of 266 patients had 411 bacterial isolates that were identified during the study period, including 211 MDR bacteria (51%). Gram-negative bacteria were common among Afghan patients (241 [76%] of 319), and 70% of these were classified as MDR. This included 58% of bacteria recovered from Afghan patients within 48 hours of hospital admission. The most common gram-negative bacteria were Escherichia coli (53% were MDR), Acinetobacter (90% were MDR), and Klebsiella (63% were MDR). Almost one-half of potential extended-spectrum ß-lactamase (ESBL) producers were community acquired. Of 100 environmental swab samples, 18 yielded MDR bacteria, including 10 that were Acinetobacter, but no potential ESBL-producing bacteria. CONCLUSIONS: Gram-negative bacteria from Afghan patients had high rates of antimicrobial resistance. Patients experiencing complex trauma and prolonged hospital stays likely contribute to the presence of MDR bacteria in this facility. However, many of these patients had community-acquired cases, which implies high rates of colonization prior to hospital admission.

Capsular serotype of Staphylococcus aureus in the era of community-acquired MRSA.

Capsular polysaccharide (CP) plays an important role in the pathogenicity and immunogenicity of Staphylococcus aureus, yet the common serotypes of S. aureus isolated from US pediatric patients have not been reported. We investigated capsular serotype as well as methicillin susceptibility, presence of Panton-Valentine leukocidin (PVL), and clonal relatedness of pediatric S. aureus isolates. Clinical isolates were tested for methicillin susceptibility, presence of mecA, lukS-PV and lukF-PV, cap5 and cap8 genes by PCR, and for capsular or surface polysaccharide expression (CP5, CP8, or 336 polysaccharide) by agglutination. Genetic relatedness was determined by pulsed-field gel electrophoresis. All S. aureus isolates encoded cap5 or cap8. Sixty-nine percent of 2004-2005 isolates were methicillin-susceptible (MSSA) and most expressed a detectable capsule. The majority of MRSA isolates (82%) were unencapsulated, exposing an expressed cell wall techoic acid antigen 336. Pulsed-field type USA300 were MRSA, PVL-positive, unencapsulated strains that were associated with deep skin infections and recurrent disease. Over half (58%) of all isolates from invasive pediatric dermatologic infections were USA300. All pediatric isolates contained either capsule type 5 or capsule type 8 genes, and roughly half of the S. aureus clinical disease isolates from our population were diverse MSSA-encapsulated strains. The majority of the remaining pediatric clinical disease isolates were unencapsulated serotype 336 strains of the PVL(+) USA300 community-associated-MRSA clone.

Polymicrobial bloodstream infection in pediatric patients: risk factors, microbiology, and antimicrobial management.

BACKGROUND: Few studies focus on polymicrobial bloodstream infections (PBSIs) in children. In previous reports, children with PBSI frequently had complex underlying medical conditions and a high incidence of specific microorganisms, but systematic evaluation with controls was not performed. We postulated that specific clinical risk factors are associated with an increased risk of PBSI, and that illness may be more severe with these infections. Additionally, we suspected that routine empiric antimicrobial therapy may frequently be inadequate to treat the variety of pathogens in PBSI. METHODS: Positive blood cultures from 1998 to 2004 were reviewed. Patients whose cultures grew >1 organism were age-matched with monomicrobial bloodstream infection controls. Records were reviewed to compare their underlying medical conditions, organisms isolated, adequacy of therapy, and clinical characteristics of illness. RESULTS: Twenty-nine episodes of PBSI were identified in 18 subjects. PBSI patients were more likely to have chronic medical conditions, chronic gastrointestinal pathology, central venous catheters, and to be receiving parenteral nutrition than controls. Pathogens found more commonly in PBSI episodes included Enterococcus spp., coagulase-negative staphylococci, and Candida spp. Empiric antimicrobial therapy was less likely to be adequate in patients with PBSI. PBSI patients were hospitalized longer, required longer intensive care and had prolonged bloodstream infection. Subjects with PBSI had prolonged duration of fever and had higher degrees of sepsis than controls. CONCLUSIONS: Chronic medical conditions, particularly gastrointestinal disease, are risk factors for PBSIs. Because clinical illness may be more severe, alteration of the empiric antimicrobial regimen should be considered in some of these patients.

Co-infection of the cotton rat (Sigmodon hispidus) with Staphylococcus aureus and influenza A virus results in synergistic disease.

Bacterial super-infection of influenza patients is the primary cause of excess mortality during influenza pandemics, with Staphylococcus aureus (S. aureus) having the highest fatality rate. The cotton rat (Sigmodon hispidus) is an excellent model for both influenza and S. aureus pathogenesis, and therefore a potential tool to model co-infection. We compared physiologic and pathologic changes in cotton rats infected with both S. aureus and influenza A/Wuhan/359/95 (H3N2), with animals infected with each pathogen alone. Co-infected cotton rats demonstrated significantly higher mortality, lower temperatures on 2 and 3 days post-inoculation (p.i.), higher levels of bacteremia and pulmonary bacterial load 4 days p.i., and worse pathology 7 days p.i. Early indicators of exacerbated disease coincided with higher pulmonary mRNA levels for IL-1beta, IL-6, IL-10 and IFNy, supporting the idea that these may contribute to disease severity. Our results demonstrate that the cotton rat is a good model of influenza and S. aureus co-infection, with increased mortality and hypothermia as well as prolonged bacterial duration indicative of synergistic disease that may be the result of increased induction of both pro- and anti-inflammatory cytokines.