Sanitation and Hygiene-Specific Risk Factors for Moderate-to-Severe Diarrhea in Young Children in the Global Enteric Multicenter Study, 2007–2011: Case-Control Study

BackgroundDiarrheal disease is the second leading cause of disease in children less than 5 y of age. Poor water, sanitation, and hygiene conditions are the primary routes of exposure and infection. Sanitation and hygiene interventions are estimated to generate a 36% and 48% reduction in diarrheal risk in young children, respectively. Little is known about whether the number of households sharing a sanitation facility affects a child''s risk of diarrhea. The objective of this study was to describe sanitation and hygiene access across the Global Enteric Multicenter Study (GEMS) sites in Africa and South Asia and to assess sanitation and hygiene exposures, including shared sanitation access, as risk factors for moderate-to-severe diarrhea (MSD) in children less than 5 y of age.Methods/FindingsThe GEMS matched case-control study was conducted between December 1, 2007, and March 3, 2011, at seven sites in Basse, The Gambia; Nyanza Province, Kenya; Bamako, Mali; Manhiça, Mozambique; Mirzapur, Bangladesh; Kolkata, India; and Karachi, Pakistan. Data was collected for 8,592 case children aged <5 y old experiencing MSD and for 12,390 asymptomatic age, gender, and neighborhood-matched controls. An MSD case was defined as a child with a diarrheal illness <7 d duration comprising ≥3 loose stools in 24 h and ≥1 of the following: sunken eyes, skin tenting, dysentery, intravenous (IV) rehydration, or hospitalization. Site-specific conditional logistic regression models were used to explore the association between sanitation and hygiene exposures and MSD. Most households at six sites (>93%) had access to a sanitation facility, while 70% of households in rural Kenya had access to a facility. Practicing open defecation was a risk factor for MSD in children <5 y old in Kenya. Sharing sanitation facilities with 1–2 or ≥3 other households was a statistically significant risk factor for MSD in Kenya, Mali, Mozambique, and Pakistan. Among those with a designated handwashing area near the home, soap or ash were more frequently observed at control households and were significantly protective against MSD in Mozambique and India.ConclusionsThis study suggests that sharing a sanitation facility with just one to two other households can increase the risk of MSD in young children, compared to using a private facility. Interventions aimed at increasing access to private household sanitation facilities may reduce the burden of MSD in children. These findings support the current World Health Organization/ United Nations Children''s Emergency Fund (UNICEF) system that categorizes shared sanitation as unimproved.     

Using the general-purpose reactivity indicator: challenging examples

We elucidate the regioselectivity of nucleophilic attack on substituted benzenesulfonates, quinolines, and pyridines using a general-purpose reactivity indicator (GPRI) for electrophiles. We observe that the GPRI is most accurate when the incoming nucleophile resembles a point charge. We further observe that the GPRI often chooses reactive “dead ends” as the most reactive sites as well as sterically hindered reactive sites. This means that care must be taken to remove sites that are inherently unreactive. Generally, among sites where reactions actually occur, the GPRI identifies the sites in the molecule that lead to the kinetically favored product(s). Furthermore, the GPRI can discern which sites react with hard reagents and which sites react with soft reagents. Because it is currently impossible to use the mathematical framework of conceptual DFT to identify sterically inaccessible sites and reactive dead ends, the GPRI is primarily useful as an interpretative, not a predictive, tool.     

First multi-locus sequence typing scheme for Arcobacter spp.

Background  

Arcobacter spp. are a common contaminant of food and water, and some species, primarily A. butzleri and A. cryaerophilus, have been isolated increasingly from human diarrheal stool samples. Here, we describe the first Arcobacter multilocus sequence typing (MLST) method for A. butzleri, A. cryaerophilus, A. skirrowii, A. cibarius and A. thereius.     

CXCR4 drives the metastatic phenotype in breast cancer through induction of CXCR2 and activation of MEK and PI3K pathways

Aberrant expression of CXCR4 in human breast cancer correlates with metastasis to tissues secreting CXCL12. To understand the mechanism by which CXCR4 mediates breast cancer metastasis, MCF-7 breast carcinoma cells were transduced to express wild-type CXCR4 (CXCR4WT) or constitutively active CXCR4 (CXCR4ΔCTD) and analyzed in two-dimensional (2D) cultures, three-dimensional reconstituted basement membrane (3D rBM) cultures, and mice using intravital imaging. Two-dimensional cultures of MCF-7 CXCR4ΔCTD cells, but not CXCR4WT, exhibited an epithelial-to-mesenchymal transition (EMT) characterized by up-regulation of zinc finger E box–binding homeobox 1, loss of E-cadherin, up-regulation of cadherin 11, p120 isoform switching, activation of extracellular signal-regulated kinase 1/2, and matrix metalloproteinase-2. In contrast to the 2D environment, MCF-7 CXCR4WT cells cultured in 3D rBM exhibited an EMT phenotype, accompanied by expression of CXCR2, CXCR7, CXCL1, CXCL8, CCL2, interleukin-6, and granulocyte–macrophage colony stimulating factor. Dual inhibition of CXCR2 with CXCR4, or inhibition of either receptor with inhibitors of mitogen-activated protein kinase 1 or phosphatidylinositol 3-kinase, reversed the aggressive phenotype of MCF-7 CXCR4-expressing or MDA-MB-231 cells in 3D rBM. Intravital imaging of CXCR4-expressing MCF-7 cells revealed that tumor cells migrate toward blood vessels and metastasize to lymph nodes. Thus CXCR4 can drive EMT along with an up-regulation of chemokine receptors and cytokines important in cell migration, lymphatic invasion, and tumor metastasis.     

β-Lactam Resistance in Salmonella Strains Isolated from Retail Meats in the United States by the National Antimicrobial Resistance Monitoring System between 2002 and 2006

Ampicillin-resistant (Amp^r) Salmonella enterica isolates (n = 344) representing 32 serotypes isolated from retail meats from 2002 to 2006 were tested for susceptibility to 21 other antimicrobial agents and screened for the presence of five beta-lactamase gene families (bla_CMY, bla_TEM, bla_SHV, bla_OXA, and bla_CTX-M) and class 1 integrons. Among the Amp^r isolates, 66.9% were resistant to five or more antimicrobials and 4.9% were resistant to 10 or more antimicrobials. Coresistance to other β-lactams was noted for amoxicillin-clavulanic acid (55.5%), ceftiofur (50%), cefoxitin (50%), and ceftazidime (24.7%), whereas less than 5% of isolates were resistant to piperacillin-tazobactam (4.9%), cefotaxime (3.5%), ceftriaxone (2%), and aztreonam (1.2%). All isolates were susceptible to cefepime, imipenem, and cefquinome. No Salmonella producing extended-spectrum beta-lactamases was found in this study. Approximately 7% of the isolates displayed a typical multidrug-resistant (MDR)-AmpC phenotype, with resistance to ampicillin, chloramphenicol, streptomycin, sulfonamide, tetracycline, plus resistance to amoxicillin-clavulanic acid, cefoxitin, and ceftiofur and with decreased susceptibility to ceftriaxone (MIC ≥ 4 μg/ml). Pulsed-field gel electrophoresis results showed that several MDR clones were geographically dispersed in different types of meats throughout the five sampling years. Additionally, 50% of the isolates contained bla_CMY, 47% carried bla_TEM-1, and 2.6% carried both genes. Only 15% of the isolates harbored class I integrons carrying various combinations of aadA, aadB, and dfrA gene cassettes. The bla_CMY, bla_TEM, and class 1 integrons were transferable through conjugation and/or transformation. Our findings indicate that a varied spectrum of coresistance traits is present in Amp^r Salmonella strains in the meat supply of the United States, with a continued predominance of bla_CMY and bla_TEM genes in β-lactam-resistant isolates.Nontyphoid Salmonella enterica is one of the most important food-borne pathogens and represents a significant public health hazard worldwide. It is estimated that 1.4 million people in the United States are infected with non-Typhi Salmonella annually, resulting in 15,000 hospitalizations and more than 400 deaths (28). Salmonella infections in humans often result from the ingestion of contaminated foods, such as poultry, beef, pork, eggs, milk, seafood, and produce (10). Salmonellosis following direct contact with animals and dog treats has also been reported (3, 6, 7). Human salmonellosis usually results in a self-limiting diarrhea that does not require antimicrobial therapy. However, in severe cases of enteritis and systemic infections, fluoroquinolones and extended-spectrum cephalosporins such as ceftriaxone (AXO) are used as first-line therapeutics (12, 27).Multidrug-resistant (MDR) Salmonella strains have been detected in many serotypes, such as S. enterica serotype Typhimurium (9, 26), S. enterica serotype Agona, S. enterica serotype Anatum, S. enterica serotype Choleraesuis, S. enterica serotype Dublin, S. enterica serotype Heidelberg, S. enterica serotype Kentucky, S. enterica serotype Newport, S. enterica serotype Schwarzengrund, S. enterica serotype Senftenberg, and S. enterica serotype Uganda, among others (14, 33, 35) (http://internet-dev/cvm/2005NARMSExeRpt.htm). The most common MDR pattern, which first emerged in S. Typhimurium, has been a pattern of resistance to ampicillin (AMP), chloramphenicol (CHL), streptomycin (STR), sulfonamides, and tetracycline (TET) (ACSSuT). More recently, strains exhibiting the ACSSuT pattern also have acquired MDR plasmids carrying the bla_CMY gene and others (30) that can spread readily to different members of the Enterobacteriaceae. The strains demonstrate extensive resistances, which, in addition to the ACSSuT phenotype, may include resistance to amoxicillin-clavulanic acid (AUG), cefoxitin (FOX), and ceftiofur (TIO) and decreased susceptibility to AXO (MIC ≥ 4 μg/ml). TIO is a third-generation cephalosporin that was approved for use in animals in 1998. Tio^r Salmonella isolates often show resistance or decreased susceptibility to AXO (also a third-generation cephalosporin used to treat human infections). Some strains may also display resistance to gentamicin (GEN), kanamycin (KAN), and trimethoprim-sulfamethoxazole ([SMX] COT) as well as resistance to disinfectants and heavy metals. Resistance to third-generation cephalosporins in Salmonella strains is of interest because these are the drugs of choice for treating salmonellosis in children, where fluoroquinolones are contraindicated (13).To date, more than 340 beta-lactamases have been described (11). The most common genes, such as bla_TEM, bla_SHV, bla_CTX-M, bla_OXA, bla_PER, bla_PSE, and bla_CMY, have been detected in Salmonella, with the prevalence of these genes varying by region (32). Extended-spectrum beta-lactamases (ESBLs) are less prevalent in Salmonella strains than in other gram-negative bacteria such as Klebsiella, Escherichia coli, and Proteus. The ESBLs are β-lactamases capable of conferring bacterial resistance to the penicillins; to first-, second-, and third-generation cephalosporins; and to aztreonam (ATM) (but not to the cephamycins or carbapenems) by hydrolysis of these antibiotics, which are inhibited by β-lactamase inhibitors such as clavulanic acid (21). Most ESBL-carrying Salmonella strains have been reported in Latin America, the Western Pacific, and Europe (32), with only a few reports from North America. In the United States the first case was reported in 1994, when bla_CTX-5 was detected in an S. Typhimurium var. Copenhagen strain from an infant adopted from Russia (25). Additional ESBL Salmonella strains have been reported recently, one from a horse (bla_SHV-12) and another from a 3-month-old child (bla_CTX-M-5) (23, 25). Carbapenem resistance in Salmonella is also rare in the United States but has been detected in S. enterica serotype Cubana associated with a plasmid-mediated bla_KPC-2 gene (18). In contrast to the low prevalence of ESBL-carrying Salmonella strains in the United States, AmpC resistance mediated by bla_CMY has been emerging in both humans and food animals. The bla_CMY encodes a cephalomycinase that exhibits extended resistance to many beta-lactams, including first-, second-, and third-generation cephalosporins (36).The objectives of this study were to determine the genetic basis of beta-lactam resistance and to examine the extent of coresistance to other antimicrobials among 344 Amp^r Salmonella isolates obtained from retail meats. We screened for the presence of five beta-lactam resistance gene families (bla_CMY, bla_TEM, bla_SHV, bla_OXA, and bla_CTX-M) and the presence of class 1 integrons. The range of resistance phenotypes borne on plasmids was examined by filter mating and electroporation, and all isolates were characterized for genetic relatedness using pulsed-field gel electrophoresis (PFGE).