In this age of emerging antibiotic resistance, limited therapeutic options exist for treating multidrug-resistant organisms. Combination therapy is commonly employed to manage these infections despite little laboratory guidance as to the efficacy of this approach. Synergy testing methods have been used to assess the interaction of antibiotic combinations in vitro. This review will discuss the four primary methods used to assess synergy, as well as the data that exist for testing of cystic fibrosis. In the final analysis, this review concludes that there is not enough evidence to endorse synergy testing for routine clinical use.

2The viridans group streptococci (VGS) are a heterogeneous group of organisms that can be human commensals, colonizing the gastrointestinal and genitourinary tracts in addition to the oral mucosa. VGS are generally considered to be of low pathogenic potential in immunocompetent individuals. However, in certain patient populations, VGS can cause invasive disease, such as endocarditis, intra-abdominal infection, and shock. Within the VGS, the rates and patterns of antimicrobial resistance vary greatly depending upon the species identification and the patient population. In general, Streptococcus mitis group organisms are resistant to more antimicrobial agents than the other VGS species. This review addresses current VGS taxonomy, in addition to the current methodologies being used in clinical microbiology laboratories for identification of VGS. Automated systems struggle overall with species level identification and susceptibility testing for VGS. Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) identification is emerging as a potential alternative for organism identification. A review of recent pediatric-specific data regarding the clinical manifestations of VGS revealed that the Streptococcus anginosus group (SAG) organisms may be important pathogens in pediatric patients and that the VGS may contribute to disease in patients with cystic fibrosis. It also appears that rates of antimicrobial resistance in VGS in pediatric patients are surpassing those of the adult population. TAXONOMY AND MICROBIOLOGYThe viridans group streptococci (VGS) are a heterogeneous group of organisms that can be both commensal flora and pathogens in humans. They are the "grab bag" that remains when the beta-hemolytic streptococci, enterococci, and pneumococci are excluded from the streptococci. The purpose of this review is to summarize the currently accepted taxonomic classification of this group of organisms, examine the state of the art for identification of the VGS, and then focus on the pediatric clinical manifestations associated with the VGS.Perhaps the only consistency observed in discussions regarding the taxonomy of the VGS is a lack of consistency. The taxonomy is very controversial, and for many years, a standardized naming scheme or typing system for this group of organisms was lacking; therefore, discussions on this topic frequently include the phrase "poorly classified." There are now at least 30 recognized species of VGS (11,14).

POINT

Recently, biofilms have become a topic of interest in the study of the human pathogen group A Streptococcus (GAS). In this study, we sought to learn more about the make-up of these structures and gain insight into biofilm regulation. Enzymic studies indicated that biofilm formation by GAS strain MGAS5005 required an extracellular protein and DNA component(s). Previous results indicated that inactivation of the transcriptional regulator Srv in MGAS5005 resulted in a significant decrease in virulence. Here, inactivation of Srv also resulted in a significant decrease in biofilm formation under both static and flow conditions. Given that production of the extracellular cysteine protease SpeB is increased in the srv mutant, we tested the hypothesis that increased levels of active SpeB may be responsible for the reduction in biofilm formation. Western immunoblot analysis indicated that SpeB was absent from MGAS5005 biofilms. Complementation of MGAS5005Dsrv restored the biofilm phenotype and eliminated the overproduction of active SpeB. Inhibition of SpeB with E64 also restored the MGAS5005Dsrv biofilm to wild-type levels.

i Diarrhea due to enteric bacterial pathogens causes significant morbidity and mortality in the United States and worldwide. However, bacterial pathogens may be infrequently identified. Currently, culture and enzyme immunoassays (EIAs) are the primary methods used by clinical laboratories to detect enteric bacterial pathogens. We conducted a multicenter evaluation of the BD Max enteric bacterial panel (EBP) PCR assay in comparison to culture for the detection of Salmonella spp., Shigella spp., Campylobacter jejuni, and Campylobacter coli and an EIA for Shiga toxins 1 and 2. A total of 4,242 preserved or unpreserved stool specimens, including 3,457 specimens collected prospectively and 785 frozen, retrospective samples, were evaluated. Compared to culture or EIA, the positive percent agreement (PPA) and negative percent agreement (NPA) values for the BD Max EBP assay for all specimens combined were as follows: 97.1% and 99.2% for Salmonella spp., 99.1% and 99.7% for Shigella spp., 97.2% and 98.4% for C. jejuni and C. coli, and 97.4% and 99.3% for Shiga toxins, respectively. Discrepant results for prospective samples were resolved with alternate PCR assays and bidirectional sequencing of amplicons. Following discrepant analysis, PPA and NPA values were as follows: 97.3% and 99.8% for Salmonella spp., 99.2% and 100% for Shigella spp., 97.5% and 99.0% for C. jejuni and C. coli, and 100% and 99.7% for Shiga toxins, respectively. No differences in detection were observed for samples preserved in Cary-Blair medium and unpreserved samples. In this large, multicenter study, the BD Max EBP assay showed superior sensitivity compared to conventional methods and excellent specificity for the detection of enteric bacterial pathogens in stool specimens. The World Health Organization reports that, worldwide, there are nearly 1.7 billion cases of diarrheal disease every year and that diarrheal disease is the second leading cause of death of children Ͻ5 years old. Each year, diarrhea kills ϳ760,000 children under the age of 5 years, and most importantly, it is preventable and treatable. Diarrhea is also a leading cause of malnutrition in this same age group. Most of this disease is related to unsafe drinking water, inadequate sanitation, and poor hygiene (1, 2).Acute gastroenteritis is caused by a number of bacterial, viral, and parasitic agents (3). In the United States, noroviruses cause most cases of self-limited, acute gastroenteritis. However, Salmonella, Campylobacter, Shigella, and Shiga toxin-producing Escherichia coli (STEC) are the most common diarrheagenic bacteria, and they are usually associated with foodborne illness (4). Furthermore, Shigella is more frequently transmitted from person to person due to the low infectious dose. Importantly, agents of gastroenteritis may not be distinguished clinically. Identifying the cause of diarrhea is important for both the treatment of individual patients and public health intervention through outbreak management (5).Conventional microbiological cultures remain the gold standard...

Group A Streptococcus (GAS) is a common causative agent of pharyngitis, but the role of GAS in otitis media is underappreciated. In this study, we sought to test the hypothesis that GAS colonizes the middle ear and establishes itself in localized, three-dimensional communities representative of biofilms. To test this hypothesis, the middle ears of chinchillas were infected with either a strain of GAS capable of forming biofilms in vitro (MGAS5005) or a strain deficient in biofilm formation due to the lack of the transcriptional regulator Srv (MGAS5005 ⌬srv). Infection resulted in the formation of large, macroscopic structures within the middle ears of MGAS5005-and MGAS5005 ⌬srv-infected animals. Plate counts, scanning electron microscopy, LIVE/ DEAD staining, and Gram staining revealed a difference in the distributions of MGAS5005 versus MGAS5005 ⌬srv in the infected samples. High numbers of CFU of MGAS5005 ⌬srv were isolated from the middle ear effusion, and MGAS5005 ⌬srv was found randomly distributed throughout the excised macroscopic structure. In contrast, MGAS5005 was found in densely packed microcolonies indicative of biofilms within the excised material from the middle ear. CFU levels of MGAS5005 from the effusion were significantly lower than that of MGAS5005 ⌬srv early during the course of infection. Allelic replacement of the chromosomally encoded streptococcal cysteine protease (speB) in the MGAS5005 ⌬srv background restored biofilm formation in vivo. Interestingly, our results suggest that GAS naturally forms a biofilm during otitis media but that biofilm formation is not required to establish infection following transbullar inoculation of chinchillas.

No abstract

bUrinary tract infections (UTIs) are a common occurrence in children. The management and laboratory diagnosis of these infections pose unique challenges that are not encountered in adults. Important factors, such as specimen collection, urinalysis interpretation, culture thresholds, and antimicrobial susceptibility testing, require special consideration in children and will be discussed in detail in the following review.