Validation of a real-time polymerase chain reaction assay for the detection of Salmonella in crops of broiler chickens.

Salmonella is one of the frequent causes of bacterial foodborne diseases with major public health impact in industrialized countries. Food-producing animals, in particular poultry, are major sources of human salmonellosis. Salmonella is normally found in the gastrointestinal tract of animals and can contaminate the carcass during the slaughtering process. In poultry, crops are also colonized by this pathogen. Crops are more likely to get ruptured during evisceration and contaminate the carcass and therefore present a health risk to consumers. Reducing Salmonella colonization in crops could decrease carcass contamination and is considered a potential preharvest critical control point in poultry production. Furthermore, rapid and reliable diagnostic methods to detect Salmonella are needed to monitor crop colonization to help ensure food safety. However, detection of Salmonella by bacteriological methods is time consuming and labor intensive and is not suitable for routine screening of a large number of samples. Therefore, this study was undertaken to validate a real-time PCR (RPCR) assay for the detection of Salmonella spp. in crop samples of broiler chickens. In total, 997 crop samples (35 spiked, 962 field) were processed by both RPCR and culture. The RPCR correctly identified all spiked crop samples. Out of 962 field crop samples, 100 tested positive by RPCR and 88 tested positive by culture for Salmonella, giving a sample level prevalence of 10.4 % (95% CI: 8.54 to 12.50%) and 9.1% (95% CI: 7.40 to 11.15%), respectively. The agreement beyond chance between RPCR and culture was 92% (P < 0.001) and 100% (P < 0.001) for field and spiked samples, respectively. Compared with culture, the sensitivity and specificity of RPCR were 98.86 and 98.51% for field samples and 100 and 100% for spiked samples, respectively. Where bacterial speciation is required, only the positive samples would be cultured. Therefore, RPCR can be used as a good screening tool for Salmonella spp. in crops by eliminating the time-consuming and labor-intensive culture of negative samples.

A real-time PCR assay for the detection of Salmonella in a wide variety of food and food-animal matricest.

Conventional culture methods have traditionally been considered the "gold standards" for the isolation and identification of foodborne pathogens. However, culture methods are labor-intensive and time-consuming. We have developed a real-time PCR assay for the detection of Salmonella in a variety of food and food-animal matrices. The real-time PCR assay incorporates both primers and hybridization probes based on the sequence of the Salmonella invA gene and uses fluorescent resonance energy transfer technology to ensure highly sensitive and specific results. This method correctly classified 51 laboratory isolates of Salmonella and 28 non-Salmonella strains. The method was also validated with a large number of field samples that consisted of porcine feces and cecal contents, pork carcasses, bovine feces and beef carcasses, poultry cecal contents and carcasses, equine feces, animal feeds, and various food products. The samples (3388) were preenriched in buffered peptone water and then selectively enriched in tetrathionate and Rappaport-Vassiliadis broths. Aliquots of the selective enrichment broths were combined for DNA extraction and analysis by the real-time PCR assay. When compared with the culture method, the diagnostic sensitivity of the PCR assay for the various matrices ranged from 97.1 to 100.0%, and the diagnostic specificity ranged from 91.3 to 100.0%. Kappa values ranged from 0.87 to 1.00, indicating excellent agreement of the real-time PCR assay to the culture method. The reduction in time and labor makes this highly sensitive and specific real-time PCR assay an excellent alternative to conventional culture methods for surveillance and research studies to improve food safety.

Plasma norepinephrine kinetics in patients with posttraumatic stress disorder.

To determine whether basal sympathetic nervous system (SNS) function is increased in patients with posttraumatic stress disorder (PTSD), we used a radioisotope dilution technique to assess basal arterialized plasma norepinephrine (NE) kinetics in 12 men who were Viet Nam combat veterans with PTSD and six normal controls. In addition to determining the rates of appearance of NE into, and clearance of NE from, plasma, we measured basal arterialized plasma levels of epinephrine (EPI), and also vital signs, in both groups. Patients with PTSD actually manifested lower arterialized plasma levels of NE, and had lower rates of appearance of NE into plasma, than did controls. The rate of NE clearance from plasma was unaltered in PTSD patients. Patients with PTSD also showed a trend toward lower arterialized EPI levels than controls, but manifested a trend toward higher diastolic blood pressure. Our data indicate that basal SNS activity is not increased in patients with PTSD and that previous reports of increased resting SNS activity in this population may instead reflect SNS reactivity.

Basal sympathoadrenal function in posttraumatic distress disorder.

Research has consistently shown that patients with posttraumatic stress disorder (PTSD) manifest greater changes in heart rate, blood pressure, and plasma epinephrine than controls when exposed to trauma-related laboratory stressors. However, findings are equivocal as to whether PTSD subjects differ from controls on basal, or tonic, measures of autonomic activity. In this study, PTSD patients (n = 11) and asymptomatic controls (n = 11) were compared on measures of basal sympathoadrenal function, including plasma norepinephrine and epinephrine as well as heart rate and blood pressure. Results showed that PTSD patients were not significantly different from control subjects on any measure. Although phasic alterations in autonomic function in PTSD have been consistently found in previous research, this study suggests that tonic sympathetic nervous system activity in PTSD patients may not differ from that of healthy controls.

Autonomic responses to stress in Vietnam combat veterans with posttraumatic stress disorder.

This study tested the hypothesis that combat veterans with posttraumatic stress disorder (PTSD) experience sympathetic nervous system activation in response to war-related laboratory stimuli. Circulating plasma catecholamines, vital signs, and affect ratings were measured in 10 Vietnam combat veterans with PTSD and 11 control subjects, during and after viewing combat and noncombat stress films. PTSD subjects responded more strongly than controls to the combat film, with greater increases in plasma epinephrine, pulse, blood pressure, and subjective distress. The increases in autonomic activity of PTSD subjects was more pronounced and long lasting in response to the combat film than to the noncombat film, but type of film had no systematic effect on control subjects' responses. These findings are consistent with biological models that posit sympathoadrenal activation in response to memory-evoking cues of traumatic events in PTSD.

Glucocorticoid feedback sensitivity and adrenocortical responsiveness in posttraumatic stress disorder.

BACKGROUND: Decreased basal cortisol levels have been reported in individuals with posttraumatic stress disorder (PTSD). There is evidence for enhanced negative feedback sensitivity of the hypothalamic-pituitary-adrenal (HPA) axis in PTSD, which could account for this, but other possible mechanisms have not been ruled out. We examined the HPA axis employing a metyrapone-cortisol infusion protocol designed to study negative feedback sensitivity. METHODS: Vietnam combat trauma-exposed subjects met DSM-IV criteria for PTSD. Exclusion criteria included substance abuse and most medications. Endogenous feedback inhibition was removed by blocking cortisol synthesis with oral metyrapone and reintroduced by intravenous infusion of cortisol. In a placebo condition, subjects received oral placebo and normal saline infusion. Serial blood samples drawn over 4 hours were assayed for adrenocorticotrophic hormone (ACTH), cortisol, and 11-deoxycortisol. Selected samples were assayed for cortisol binding globulin (CBG) and dehydroepiandrosterone (DHEA). RESULTS: Basal plasma cortisol was significantly decreased in PTSD subjects (n = 13) compared with control subjects (n = 16). No significant difference in the ACTH response to cortisol infusion following metyrapone was observed; however 11-deoxycortisol was significantly decreased in PTSD subjects. In addition, CBG was significantly increased in PTSD subjects, and DHEA was significantly decreased in both PTSD and combat-exposed control subjects. CONCLUSIONS: These observations suggest decreased adrenocortical responsiveness may be an additional or alternative mechanism accounting for low cortisol in PTSD.

Convergent validity of measures of PTSD in Vietnam combat veterans.

The authors evaluated the convergent validity of several widely used psychometric tests of posttraumatic stress disorder (PTSD) symptoms against DSM-III-R criteria for PTSD in 130 Vietnam combat veterans. Significant positive correlations were found between these instruments and the number of DSM-III-R symptoms endorsed, supporting the validity of psychometric instruments as continuous measures of PTSD symptom severity. The various psychometric measures also correlated moderately with one another, suggesting that they assess related but somewhat separate PTSD phenomena. Finally, predicted relationships between stressors and symptoms were supported by significant correlations between degree of traumatic combat exposure and DSM-III-R and psychometric indexes of PTSD.

Behavioral and neuroendocrine responses to sodium lactate infusion in subjects with posttraumatic stress disorder.

OBJECTIVE: Sodium lactate infusion has induced flashbacks accompanied by panic attacks in male combat veterans with posttraumatic stress disorder (PTSD) and concurrent panic disorder. This study addressed whether sodium lactate induces flashbacks or other intrusive PTSD symptoms in PTSD patients free of concurrent panic disorder. METHOD: Behavioral, cardiovascular, catecholamine, and cortisol responses to infusion of 0.5 M sodium lactate were compared among seven subjects with PTSD without panic disorder, seven subjects with panic disorder only, and seven healthy subjects. RESULTS: Six of the seven PTSD subjects but no panic disorder or healthy subjects reported flashbacks or other intrusive PTSD symptoms during lactate infusion. Flashbacks were accompanied by substantial anxiety symptoms. Cortisol levels were low in the PTSD subjects. CONCLUSIONS: Sodium lactate induces flashbacks in persons with PTSD without comorbid panic disorder. The relationship between anxiety responses accompanying a PTSD flashback and those in a panic attack remains unclear.

Trauma, symptoms of posttraumatic stress disorder, and associated problems among incarcerated veterans.

OBJECTIVE: To help improve treatment for incarcerated veterans, the study examined exposure to trauma, symptoms of posttraumatic stress disorder (PTSD), functional status, and treatment history in a group of incarcerated veterans. METHODS: A convenience sample of 129 jailed veterans who agreed to receive outreach contact completed the Life Event History Questionnaire, the PTSD Checklist-Civilian Version (PCL-C), and the Addiction Severity Index. Participants who had scores of 50 or above on the PCL-C, designated as screening positive for PTSD, were compared with those whose scores were below 50, designated as screening negative for PTSD. RESULTS: Some 112 veterans (87 percent) reported traumatic experiences. A total of 51 veterans (39 percent) screened positive for PTSD, and 78 veterans (60 percent) screened negative. Compared with veterans who screened negative for PTSD, those who screened positive reported a greater variety of traumas; more serious current legal problems; a higher lifetime use of alcohol, cocaine, and heroin; higher recent expenditures on drugs; more psychiatric symptoms; and worse general health despite more previous psychiatric and medical treatment as well as treatment for substance abuse. CONCLUSIONS: The findings encourage the development of an improved treatment model to keep jailed veterans with PTSD from repeated incarceration.

Combat-related posttraumatic stress disorder and severity of substance abuse in Vietnam veterans.

This study examined the effects of Vietnam war-zone duty and combat-related posttraumatic stress disorder (PTSD) on severity of drug- and alcohol-abuse disorders among veterans seeking treatment for substance dependence. Combat-exposed Vietnam-theater veterans (N = 108) were compared with Vietnam-era veterans without war-zone duty (N = 151) on psychometric measures of drug and alcohol abuse. There were no differences between theater and era veterans on these measures. However, Vietnam-theater veterans with PTSD experienced more severe drug- and alcohol-abuse problems than did theater veterans without PTSD and were at greater risk for having both forms of substance abuse. Further analyses showed that PTSD was significantly related to some dimensions of drug- and alcohol-abuse problems but not to other dimensions. These findings indicate that PTSD, rather than combat stress per se, is linked to severity of substance abuse. Finally, reexperiencing and avoidance/numbing components of PTSD were more strongly associated with drug abuse than alcohol abuse, but physiological arousal symptoms of PTSD were more highly correlated with alcohol abuse.

Application of a social skills training program in the modification of interpersonal deficits among retarded adults: a clinical replication.

Six mentally retarded adults, equally divided into two treatment groups, were provided with individualized social skills training programs. Treatment, evaluated via a multiple-baseline design strategy, was sequentially and cumulatively applied across target behaviors over a four-week intervention period. Behavioral observation probes and social validation measures served as the primary dependent variables. Results indicated that (a) treatment was effective for virtually all behaviors across all subjects, (b) improvements occurred for both training and generalization scenes, and (c) behavioral performance was maintained one month following the termination of treatment.

Frequency of symptoms and concurrent psychiatric disorder in Vietnam veterans with chronic PTSD.

The frequency of symptoms of posttraumatic stress disorder within each of three categories--reexperiencing, avoidance or numbing, and physiological arousal--was examined in 116 Vietnam combat veterans with a diagnosis of PTSD. The prevalence of all PTSD symptoms was greater than 50 percent except for flashbacks, psychogenic amnesia, and sense of foreshortened future. Comorbidity in a subgroup of 48 patients was assessed using operational criteria for DSM-III-R mental disorders. Mood disorders, psychoactive substance abuse disorders, and other anxiety disorders frequently co-occurred with PTSD, but psychotic disorders were uncommon. These findings provide empirical validation of the DSM-III-R diagnostic criteria for PTSD.

Combat-related PTSD and psychosocial adjustment problems among substance abusing veterans.

The purpose of this study were the following: a) to determine the prevalence of combat-related posttraumatic stress disorder (PTSD) symptoms among veterans seeking assistance at a Veterans Administration medical center substance abuse treatment facility, b) to examine the relative contribution of Vietnam war zone variables to PTSD symptom development, and c) to study psychosocial adjustment problems associated with Vietnam combat exposure and with PTSD symptoms among help-seeking substance abusing men. Of 489 male veterans presenting for treatment, 10.7% had significant Vietnam combat-related PTSD symptoms as measured by the Mississippi Scale for Combat-Related PTSD. Clinically significant PTSD symptoms occurred among 46% of the subsample of combat-exposed Vietnam veterans with substance abuse problems. Degree of combat exposure was the most important military stressor that distinguished Vietnam veterans with PTSD from those without PTSD, but the groups also differed on age of war zone duty, duration of war zone duty, and whether they were wounded. Veterans who served in Vietnam did not differ from veterans who had no war zone duty on various parameters of psychosocial adjustment. However, the subgroup of Vietnam veterans with PTSD symptoms reported significantly greater psychosocial adjustment problems than their counterparts who did not have PTSD. The deleterious effects associated with combat-related PTSD appeared to be confined to adjunctive psychiatric difficulties and unemployment and did not increase risk of arrests for antisocial conduct beyond that found for veterans without PTSD. Methodological and clinical implications of these findings are discussed.

Multidimensional assessment of anger in Vietnam veterans with posttraumatic stress disorder.

This study examined the effects of combat exposure and posttraumatic stress disorder (PTSD) on dimensions of anger in Vietnam veterans. Vietnam combat veterans were compared with Vietnam era veterans without war zone duty on the Multidimensional Anger Inventory (MAI). Combat veterans were not significantly more angry than their veteran peers who did not serve in Southeast Asia. Additionally, various parameters of war zone duty were not highly associated with anger scores. However, combat veterans with PTSD scored significantly higher than veterans without PTSD on measures of anger arousal, range of anger-eliciting situations, hostile attitudinal outlook, and tendency to hold anger in. These results suggest that PTSD, rather than war zone duty, is associated with various dimensions of angry affect.

Differences between psychotic and nonpsychotic patients on content dimensions of the MMPI Sc scale.

This study examined elevated MMPI Sc scores among psychotic and nonpsychotic patients to determine whether homogeneous item-content dimensions could clarify the precise meaning of elevations on scale Sc. A total of 45 psychotic patients were compared with 56 nonpsychotic psychiatric patients on the Harris and Lingoes subscales of the Sc scale. All subjects had T-score elevations on scale Sc greater than or equal to 70. The two criterion groups did not differ on overall scale Sc scores, but a distinctive pattern of subscale scores emerged that discriminated the samples. Psychotic patients obtained significantly higher scores on subscales measuring bizarre thinking and perceived loss of control over impulses and emotions. Conversely, nonpsychotics endorsed significantly more items on subscales concerned with symptoms of depression, anxiety, and thinking difficulties. These data suggest that homogeneous item-content dimensions of the Sc scale provide a means for distinguishing between psychotic and nonpsychotic patients who otherwise appear similar on overall scale Sc.

Posttraumatic stress disorder symptoms and precombat sexual and physical abuse in Desert Storm veterans.

The purpose of this research was to study the association between precombat sexual and physical abuse and combat-related posttraumatic stress disorder (PTSD) symptoms in a clinical sample of male and female Desert Storm veterans. Two hundred ninety-seven veterans provided data on precombat sexual and physical abuse, precombat psychiatric problems, sociodemographics, Desert Storm combat exposure, and PTSD symptomatology using the Mississippi Scale. Men reported significantly higher levels of combat exposure, and women described significantly more frequent precombat abuse. Precombat-abused veterans reported more frequent precombat psychiatric histories. Analysis of covariance revealed that gender significantly modified the impact of precombat abuse on combat-related and other PTSD symptomatology after adjusting for precombat psychiatric history and level of combat exposure. Specifically, females describing precombat abuse reported much greater PTSD symptomatology than did females denying precombat abuse. These results in conjunction with previous research suggest that a relationship between precombat abuse and combat-related PTSD may exist. Prospective, longitudinal studies of both men and women are needed.