Multiyear Regional Evaluation of Foliar Fungicide Applications for Cotton Target Spot Management in the Southeastern United States.

Fungicide programs for managing target spot of cotton caused by Corynespora cassiicola were evaluated over 15 site-years in the southeastern United States between 2014 and 2016. Two cultivars, hypothesized to vary in target spot susceptibility, PhytoGen 499WRF (PHY499) and Deltapine 1137B2RF (DPL1137), and four fungicides (azoxystrobin, flutriafol, pyraclostrobin, pyraclostrobin + fluxapyroxad) plus nontreated control, were compared. Fungicide programs consisted of 1) a single application at first flower or disease onset and 2) the first application followed by a second 14 days later. Treatments were applied in a factorial, randomized complete block design. Target spot onset and severity varied among site-years. Except when severity was low, target spot-associated defoliation was greater on PHY499 than on DP1137. Fungicides delayed disease development and defoliation, but application number had little impact. Based on a meta-analysis of 15 site-years, pyraclostrobin-based applications resulted in a 4 to 6% yield preservation, and yield preservation was greater at site-years with early disease onset and >40% target spot associated defoliation. Results suggest a single well-timed application of a pyraclostrobin-based fungicide reduces defoliation and protects cotton yield at locations with high target spot severity. Additional research is needed to identify risk factors for target spot-associated yield losses in cotton production systems.

Pyriproxyfen resistance of Bemisia tabaci (Homoptera: Aleyrodidae) biotype B: metabolic mechanism.

Juvenile hormone (JH) analog insecticides are relatively nontoxic to vertebrates and provide efficient control of key arthropod pests. One JH analog, pyriproxyfen, has provided over a decade of exceptional management of whiteflies in cotton of the southwestern United States. Thwarting resistance to pyriproxyfen in Bemisia tabaci (Gannadius) (a.k.a. Bemisia argentifolii Bellows and Perring) has been the focus of an integrated resistance management program because this insecticide was first registered for use in Arizona cotton in 1996. Resistance levels have increased slowly in field populations in recent years but have not demonstrably affected field performance of pyriproxyfen. Resistant strains have been isolated and studied in the laboratory to determine the mechanism of resistance and identify optimal strategies for controlling resistant whiteflies. Synergism bioassays showed that resistance in a laboratory-selected strain QC02-R, was partially suppressible with piperonyl butoxid (PBO) and diethyl maleate (DEM) but not with S, S, S-tributyl phosphorotrithioate (DEF). Consistent with the synergism bioassay results, enzymatic assays revealed that the enzyme activities of cytochrome P450 monooxygenases (P450) and glutathione S-transferases (GST) but not esterases were significantly higher in the pyriproxyfen-resistant QC02-R strain than in the susceptible strain. These results indicate that both P450 and GST are involved in whitefly resistance to pyriproxyfen.

Fusarium verticillioides (Saccardo) Nirenberg associated with hardlock of cotton.

Boll rots of cotton (Gossypium hirsutum L.) are common in the humid areas of the Southeastern US. One type of boll damage that may be differentiated from others is hardlock, with symptoms that include compression of the fibers within individual locules of mature, open cotton bolls without further obvious disintegration of the lint or damage to the carpel wall. The principal economic effect is that the boll's lint is unharvestable by mechanical cotton pickers. This disease is endemic to the Southeast and can cause severe yield losses up to 70% in some fields. Scanning electron microscopy images of fibers from hardlocked bolls showed flattened and twisted tissue compared to fibers from healthy bolls. Fusarium verticillioides (Saccardo) Nirenberg was the fungus most commonly isolated from seeds of developing cotton bolls. Flowers inoculated with F. verticillioides on the day of bloom by spraying a spore suspension onto the flowers developed significantly (P < 0.05) more hardlock symptoms compared to untreated controls. The infection process was analyzed using a F. verticillioides isolate tagged with green fluorescent protein (GFP). When it was applied to cotton flowers on the day of bloom, the GFP-tagged F. verticillioides strain was detected in the stigma and style by 2 days after bloom (DAB) and in developing seeds at 4, 6, 8, 10, 16, 20, 40, and 60 (open bolls) DAB. By 8 DAB, the GFP F. verticillioides was isolated from over 80% of developing seeds.

Inheritance of Resistance to Meloidoygne incognita in Primitive Cotton Accessions from Mexico.

Few sources of resistance to root-knot nematodes (Meloidogyne incognita) in upland cotton (Gossypium hirsutum) have been utilized to develop resistant cultivars, making this resistance vulnerable to virulence in the pathogen population. The objectives of this study were to determine the inheritance of resistance in five primitive accessions of G. hirsutum (TX1174, TX1440, TX2076, TX2079, and TX2107) and to determine allelic relations with the genes for resistance in the genotypes Clevewilt-6 (CW) and Wild Mexico Jack Jones (WMJJ). A half-diallel experimental design was used to create 28 populations from crosses among these seven sources of resistance and the susceptible cultivar DeltaPine 90 (DP90). Resistance to M. incognita was measured as eggs per g roots in the parents, F(1) and F(2) generations of each cross. The resistance in CW and WMJJ was inherited as recessive traits, as reported previously for CW, whereas the resistance in the TX accessions was inherited as a dominant trait. Chi square analysis of segregation of resistance in the F(2) was used to estimate the numbers of genes that conditioned resistance. Resistance in CW and WMJJ appeared to be a multigenic trait whereas the resistance in the TX accessions best fit either a one or two gene model. The TX accessions were screened with nine SSR markers linked to resistance loci in other cotton genotypes. The TX accessions lacked the allele amplified by SSR marker CR316 and linked to resistance in CW and other resistant genotypes derived from this source. Four of five TX genotypes lacked the amplification products from the marker BNL1231 that is also associated with the resistant allele on Chromosome 11 in WMJJ, CW, NemX, M120 RNR and Auburn 634 RNR. However, all five TX genotypes produced the same amplification products from three SSR markers linked to the resistant allele on Chromosome 14 in M120 RNR and M240 RNR. The TX accessions have unique resistance genes that are likely to be useful in efforts to develop resistant cotton cultivars with increased durability.

The future of nematode management in cotton.

The importance of plant-parasitic nematodes as yield-limiting pathogens of cotton has received increased recognition and attention in the United States in the recent past. This paper summarizes the remarks made during a symposium of the same title that was held in July 2007 at the joint meeting of the Society of Nematologists and the American Phytopathological Society in San Diego, California. Although several cultural practices, including crop rotation, can be effective in suppressing the populations of the important nematode pathogens of cotton, the economic realities of cotton production limit their use. The use of nematicides is also limited by issues of efficacy and economics. There is a need for development of chemistries that will address these limitations. Also needed are systems that would enable precise nematicide application in terms of rate and placement only in areas where nematode population densities warrant application. Substantial progress is being made in the identification, characterization and mapping of loci for resistance to Meloidogyne incognita and Rotylenchulus reniformis. These data will lead to efficient marker-assisted selection systems that will likely result in development and release of nematode-resistant cotton cultivars with superior yield potential and high fiber quality.

Clinical presentations of soft-tissue infections and surgical site infections.

Skin and soft-tissue infections that usually follow minor traumatic events or surgical procedures are caused by a wide spectrum of bacteria. Less frequently, the infections occur spontaneously, which often is clinically confusing and leads to delays in diagnosis. Most of the infections are self-limited and easily treated with local measures and/or antibiotics. Others are life-threatening, requiring prompt diagnosis and aggressive surgical debridement in addition to the wise choice of antibiotic agents to limit tissue loss and preserve life. Many survivors experience critical tissue losses that may require changes in lifestyle as well as major reconstructive cosmetic surgery. Involvement of antibiotic-resistant gram-positive microorganisms in these infections only increases the difficulty of their treatment and may have a significant influence on the ultimate outcome.

Cell wall biosynthesis: glycan containing oligomers in developing cotton fibers, cotton fabric, wood and paper.

A series of oligomeric glycans can be extracted from the cell walls of developing cotton fibers with weak acid. Glycans that produce similar profiles on high pH anion chromatography with pulsed amperometric detection (HPAEC-PAD) are also found in a protein complex extracted from developing fibers and in amorphous aggregates found in association with immature fibers in developing, but not in mature cotton bolls. The quantity and composition of the glycans recovered from the carbohydrate-protein complex varies significantly with the time of day when the bolls are harvested. This diurnal variation is consistent with the hypothesis that secondary cell walls are deposited primarily at night. Incubation of re-hydrated cotton fibers in the presence of exogenous oligosaccharides, myo-inositol and glycerol substantially alters the apparent quantity of the oligomers extracted from the fibers. The same and similar glycans have also been extracted from cotton fabric, marine algae, various paper products and wood. While many of the oligomers isolated from the various cellulose sources display the same peaks by HPAEC-PAD, the specific number of oligomers and their relative quantities appear unique for each source of cellulosic material. Oligomeric glycans, as described in the preceding, are present in all cellulose sources that have been investigated. Their relative abundance changes in response to source, stage of development and other physiological variables. We hypothesize that the glycans are intermediates in the biological assembly of cellulose, and that their incorporation in cellulose is mediated by physicochemical and enzymatic mechanisms.

Preventing surgical site infections: a surgeon's perspective.

Wound site infections are a major source of postoperative illness, accounting for approximately a quarter of all nosocomial infections. National studies have defined the patients at highest risk for infection in general and in many specific operative procedures. Advances in risk assessment comparison may involve use of the standardized infection ratio, procedure-specific risk factor collection, and logistic regression models. Adherence to recommendations in the 1999 Centers for Disease Control and Prevention guidelines should reduce the incidence of infection in surgical patients.

Response of Acala cotton to nitrogen rates in the San Joaquin Valley of California.

The responses of Acala cotton (Gossypium hirsutum L.) in California to a range of applied nitrogen (N) treatments were investigated in a 5-year, multisite experiment. The experiment's goals were to identify crop growth and yield responses to applied N and provide information to better assess the utility of soil residual N estimates in improving fertilizer management. Baseline fertilizer application rates for the lowest applied N treatments were based on residual soil nitrate-N (NO3-N) levels determined on soil samples from the upper 0.6 m of the soil collected prior to spring N fertilization and within 1 week postplanting each year. Results have shown positive cotton lint yield responses to increases in applied N across the 56 to 224 kg N/ha range in only 41% (16 out of 39) of test sites. Soil NO3-N monitoring to a depth of 2.4 m in the spring (after planting) and fall (postharvest) indicate most changes in soil NO3- occur within the upper 1.2 m of soil. However, some sites (those most prone to leaching losses of soluble nutrients) also exhibited net increases in soil NO3-N in the 1.2- to 2.4-m depth zone when comparing planting time vs. postharvest data. The lack of yield responses and soil NO3-N accumulations at some sites indicate that more efforts should be put into identifying the amount of plant N requirements that can be met from residual soil N, rather than solely from fertilizer N applications.

The role of quinolones in abdominal surgery.

The quinolone antibiotics have been a major advance for the treatment of various types of infections. These agents have generally good safety profiles, broad-spectrum activity, and favorable pharmacokinetics. In addition, several of these antibiotics are available in both intravenous and oral formulations, which allows for sequential therapy resulting in potential cost savings. However, patients can develop serious central nervous system side effects (seizures) and phototoxicity. In addition, the bioavailability of agents in this class can be reduced by coadministration with cations, such as magnesium, aluminum, calcium, and iron, which may make bioavailability unpredictable in patients. Although older quinolones such as ciprofloxacin were effective as prophylactic agents for biliary procedures and colorectal surgery and for the treatment of intra-abdominal infections, the use of these older quinolones was limited by the development of resistant organisms. In addition, because these agents had poor activity against anaerobes such as Bacteroides fragilis, the agents had to be combined with an antianaerobic agent, such as metronidazole, when anaerobic coverage was required. Recently, a new quinolone, trovafloxacin, has become available. Trovafloxacin has demonstrated increased activity against anaerobes in animal and human studies. However, the clinical profile of trovafloxacin for abdominal infections has not been fully demonstrated, and there is some concern that its activity against aerobic gram-negative bacilli, especially Pseudomonas aeruginosa, may not equal that of ciprofloxacin. Moreover, the safety profile of trovafloxacin is disadvantageous owing to reports of severe hepatic toxicity.

Optimal treatment of complicated skin and skin structure infections.

Gram-positive bacteria (e.g. Staphylococcus aureus and Streptococcus pyogenes) are the main cause of skin and skin structure infections (SSSI). Treatment presents a clinical challenge to the physician, particularly with the increase in multidrug-resistant strains and widespread cross-resistance to antibiotic treatment. Initial treatment of SSSI involves the use of fluoroquinolones or penicillinase-resistant penicillins. If infection is caused by methicillin-resistant staphylococci, therapy with glycopeptides is warranted. However, in the last few years several cases of infection caused by strains of S. aureus with reduced susceptibility to glycopeptides have been reported. Quinupristin/dalfopristin is a new streptogramin that has shown efficacy in the management of multidrug-resistant gram-positive infections. Two major studies suggest that in the treatment of complicated SSSI, the clinical efficacy of quinupristin/dalfopristin is equivalent to that of vancomycin and/or oxacillin and vancomycin and/or cefazolin.

Treatment of hospitalized patients with complicated gram-positive skin and skin structure infections: two randomized, multicentre studies of quinupristin/dalfopristin versus cefazolin, oxacillin or vancomycin. Synercid Skin and Skin Structure Infection Group.

Quinupristin/dalfopristin (Synercid), the first injectable streptogramin antibiotic available for the treatment of complicated gram-positive skin and skin structure infections, was compared with standard comparators (cefazolin, oxacillin or vancomycin) in one USA and one international trial. These two randomized, open-label trials of virtually identical design enrolled a total of 893 patients (450 quinupristin/dalfopristin, 443 comparator). The majority of patients had erysipelas, traumatic wound infection or clean surgical wound infection. Staphylococcus aureus was the most frequently isolated pathogen in both treatment groups and polymicrobial infection was more common in the quinupristin/dalfopristin group than in the comparator group. The clinical success rate (cure plus improvement) in the clinically evaluable population was equivalent between the two treatment groups (68.2% quinupristin/dalfopristin, 70.7% comparator; 95% CI, -10.1, 5.1) despite a shorter mean duration of treatment for quinupristin/dalfopristin patients. In the bacteriologically evaluable population, by-patient and by-pathogen bacteriological eradication rates were somewhat lower for quinupristin/dalfopristin (65.8% and 66.6%, respectively) than for the comparator regimens (72.7% and 77.7%, respectively). The lower bacteriological response rates in the quinupristin/dalfopristin group were, in part, due to a higher rate of polymicrobial infections and a higher incidence of patients classified as clinical failure, a category which included premature discontinuation of treatment because of local venous adverse events. The bacteriological eradication rate for quinupristin/dalfopristin was higher in monomicrobial infections than in polymicrobial infections (72.6% versus 63.3%, respectively), whereas the corresponding rate for the comparator regimens was lower for monomicrobial infections than polymicrobial infections (70.8% versus 83.1%). This finding was not unexpected, since the spectrum of quinupristin/dalfopristin is focused on gram-positive pathogens and additional antibiotics to treat gram-negative bacteria were not required per protocol. The systemic tolerability of both treatment regimens was qualitatively similar. A higher rate of drug-related venous adverse events was reported for quinupristin/dalfopristin (66.2%) than for the comparator regimen (28.4%). Premature discontinuation of study drug was primarily due to adverse clinical events for quinupristin/dalfopristin (19.1%), whereas the most common reason for discontinuation among those receiving the comparator regimens was treatment failure (11.5%). Quinupristin/dalfopristin is an effective alternative for the treatment of hospitalized patients with complicated skin and skin structure infections due to quinupristin/ dalfopristin-susceptible gram-positive organisms, including methicillin- and erythromycin-resistant S. aureus.

Management of bacterial complications in critically ill patients: surgical wound and catheter-related infections.

The occurrence of surgical wound infections and/or bacteremia associated with central venous catheter use are of growing concern to all physicians who treat critically ill patients. The physician must be aware that some patients have an even greater risk for infection, such as those with multiple risk factors, those who are on central lines, or those patients who undergo multiple invasive diagnostic or therapeutic procedures. The emergence of resistant pathogens, particularly Gram-positive pathogens, is an important factor in the morbidity and mortality of hospitalized patients. In the face of this growing resistance among target organisms, the selection of the correct antimicrobial and nonpharmacologic interventions, based on correct identification and susceptibility test data, has become increasingly challenging. Methicillin-resistant Staphylococcus aureus and, more recently, glycopeptide-resistant enterococci and staphylococci represent a significant danger to the patient. As a consequence, earlier and more precise identification of the pathogens most frequently associated with infection is essential. The role of exacting surgical technique, infection control measures, and the appropriate use of prophylactic and therapeutic antibiotics cannot be overestimated in helping to reduce potential morbidity and mortality associated with severe surgical infection. The development of new antibiotics may help treat the difficult cases attributable to resistant Gram-positive bacteria.

Postoperative infections in the age of drug-resistant gram-positive bacteria.

Postoperative infection is a significant cause of surgical morbidity and mortality. The risk of infection after surgery depends on a number of factors, including the type and length of the surgical procedure; the age, underlying conditions, and previous history of the patient; the skill of the surgeon; the diligence with which infection control procedures are applied; and the type and timing of preoperative antibiotic prophylaxis. Methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci, now implicated in many postoperative infections, have been joined most recently by strains of S. aureus that show intermediate levels of resistance to vancomycin. Postoperative infections caused by drug-resistant pathogens are more difficult to treat and are associated with a higher morbidity and mortality. New antibiotics that are effective against drug-resistant pathogens are urgently needed, as is renewed dedication to the prevention of postoperative infection and to the use of the principles of infection control.

Evaluation of the protective value of hospital gowns against blood strike-through and methicillin-resistant Staphylococcus aureus penetration.

BACKGROUND: Hospital gowns protect patients and health care workers from exposure to blood and other infectious materials. Previous studies have shown that certain gowns do allow blood strike-through. Because of worldwide increases in the incidence of Staphylococcus aureus infections, especially with methicillin-resistant strains, there is now increased concern regarding bacterial transmission through gowns. METHODS: This study evaluated six gown types used in hospitals (one disposable cover or isolation gown, three disposable operating room gowns, and new and washed reusable operating room gowns). Gowns were evaluated for dry spore and S. aureus filtration efficiencies and were subjected to 20 time-pressure combinations with methicillin-resistant S. aureus-spiked blood (10(4)/ml) to evaluate blood strike-through and passage of methicillin-resistant S. aureus. RESULTS: Blood strike-through was lowest with disposable operating room gowns 1 and 2 (polypropylene). Disposable operating room gown 3 (polyester-wood pulp) showed the greatest strike-through and overall passage of methicillin-resistant S. aureus. Operating room gowns 1 and 2 showed minimal bacterial passage, whereas the disposable cover (polypropylene) only allowed passage at pressures greater than 1 psi. Bacterial filtration efficiency testing showed operating room gowns 1 and 2 to be the most protective; operating room gown 3 and both reusable (cotton) gowns were the least protective. Dry spore passage was greatest for reusable gowns. CONCLUSION: Different hospital gowns offer varying degrees of protection against fluid strike-through or bacterial passage. Gowns therefore should be chosen according to the task performed and conditions encountered.

Multicenter, randomized study comparing levofloxacin and ciprofloxacin for uncomplicated skin and skin structure infections.

BACKGROUND: The fluoroquinolone, levofloxacin, is active against most common pathogens in skin and skin structure infections. METHODS: The efficacy, tolerability, and safety of levofloxacin and ciprofloxacin were compared in a randomized, open-label, multicenter trial of patients with uncomplicated skin and skin structure infections. Of 469 patients treated, 231 received levofloxacin (500 mg qd) and 238 were given ciprofloxacin (500 mg bid). RESULTS: Overall clinical success rates (cured plus improved) for levofloxacin and ciprofloxacin were 98% and 94%, respectively (95% confidence interval [CI], -7.7, 0.7). Overall microbiologic eradication rates by patient were 98% in the levofloxacin group and 89% in the ciprofloxacin group (95% CI, -14.5, -2.7), whereas eradication rates by pathogen were 98% and 90%, respectively (95% CI, -12.6, -3.7). The eradication rate for Staphylococcus aureus was 100% in the levofloxacin group and 87% in the ciprofloxacin group (95% CI, -20.2, -5.1). Treatment-emergent adverse events were comparable, with drug-related adverse events reported in 6% of levofloxacin patients and 5% of ciprofloxacin patients. CONCLUSIONS: Levofloxacin is as effective and safe as ciprofloxacin in the treatment of uncomplicated skin and skin structure infections.