Racial Disparities Among Clinical High-Risk and First-Episode Psychosis Multisite Research Participants: A Systematic Review.

OBJECTIVE: The NIH has mandated equal representation of Black, Indigenous, and people of color (BIPOC) individuals in clinical research, but it is unclear whether such inclusion has been achieved in multisite research studies of individuals at clinical high risk for psychosis or with first-episode psychosis (FEP). An assessment of inclusion rates is important for understanding the social determinants of psychosis and psychosis risk that specifically affect BIPOC individuals. METHODS: The authors conducted a systematic review of the literature published between 1993 and 2022 of multisite research studies of clinical high risk for psychosis and FEP in North America to determine ethnoracial inclusion rates. Using an online systematic review tool, the authors checked 2,278 studies for eligibility. Twelve studies met all inclusion criteria. Data were extracted, and demographic characteristics, socioeconomic status, study design, and recruitment strategies used by each study were analyzed. RESULTS: Most (62%) of the participants in studies of clinical high risk for psychosis were White. Compared with national data, the demographic characteristics of individuals with clinical high risk were representative across most ethnoracial groups. Black participants (43%) made up the largest ethnoracial group in FEP studies and were overrepresented compared with their representation in the U.S. population. FEP studies were more likely to recruit participants from community mental health centers than were the studies of clinical high risk. CONCLUSIONS: Although these results suggest high representation of BIPOC individuals in psychosis research, opportunities exist for an improved focus on ethnoracial representation. The authors offer recommendations for practices that may increase ethnoracial diversity in future psychosis study samples.

Low Dose Lithium Treatment of Behavioral Complications in Alzheimer's Disease: Lit-AD Randomized Clinical Trial.

BACKGROUND: A case series suggested efficacy for lithium to treat agitation in dementia, but no placebo-controlled trials have been conducted. OBJECTIVES: To evaluate low-dose lithium treatment of agitation in Alzheimer's disease (AD). METHOD: In a four-site trial, patients with AD and agitation/aggression score ≥4 on the Neuropsychiatric Inventory (NPI) were randomized, double-blind, to lithium carbonate 150-600 mg daily or placebo for 12 weeks. Primary efficacy outcome was change in NPI agitation/aggression; secondary efficacy outcome was treatment response (30% reduction in NPI score for agitation/aggression plus psychosis and a Clinical Global Impression (CGI) score of much or very much improved). Safety profile of lithium was assessed. RESULTS: Fifty-eight of 77 patients (75.3%) completed the trial. In linear mixed effects model analyses, lithium was not significantly superior to placebo for agitation/aggression. Proportion of responders was 31.6% on lithium and 17.9% on placebo (χ2=1.26, p = 0.26). Moderate or marked improvement (CGI) was greater on lithium (10/38=36.8%) than placebo (0/39=0%, Fisher's exact test p <0.001). In exploratory analyses, improvement on lithium was greater than placebo on NPI delusions and irritability/lability (p's<0.05). Lithium showed greater reduction than placebo in patients with high Young Mania Rating Scale scores (ß=5.06; 95%CI,1.18 to 8.94, p = 0.01). Oral dose and serum levels demonstrated similar associations with efficacy outcomes. Lithium did not differ significantly from placebo on safety outcomes. CONCLUSIONS: Low-dose lithium was not efficacious in treating agitation but was associated with global clinical improvement and excellent safety. A larger trial may be warranted of likely lithium-responsive behavioral symptoms that overlap with mania.

Modulation of p75NTR on Mesenchymal Stem Cells Increases Their Vascular Protection in Retinal Ischemia-Reperfusion Mouse Model.

Mesenchymal stem cells (MSCs) are a promising therapy to improve vascular repair, yet their role in ischemic retinopathy is not fully understood. The aim of this study is to investigate the impact of modulating the neurotrophin receptor; p75NTR on the vascular protection of MSCs in an acute model of retinal ischemia/reperfusion (I/R). Wild type (WT) and p75NTR-/- mice were subjected to I/R injury by increasing intra-ocular pressure to 120 mmHg for 45 min, followed by perfusion. Murine GFP-labeled MSCs (100,000 cells/eye) were injected intravitreally 2 days post-I/R and vascular homing was assessed 1 week later. Acellular capillaries were counted using trypsin digest 10-days post-I/R. In vitro, MSC-p75NTR was modulated either genetically using siRNA or pharmacologically using the p75NTR modulator; LM11A-31, and conditioned media were co-cultured with human retinal endothelial cells (HREs) to examine the angiogenic response. Finally, visual function in mice undergoing retinal I/R and receiving LM11A-31 was assessed by visual-clue water-maze test. I/R significantly increased the number of acellular capillaries (3.2-Fold) in WT retinas, which was partially ameliorated in p75NTR-/- retinas. GFP-MSCs were successfully incorporated and engrafted into retinal vasculature 1 week post injection and normalized the number of acellular capillaries in p75NTR-/- retinas, yet ischemic WT retinas maintained a 2-Fold increase. Silencing p75NTR on GFP-MSCs coincided with a higher number of cells homing to the ischemic WT retinal vasculature and normalized the number of acellular capillaries when compared to ischemic WT retinas receiving scrambled-GFP-MSCs. In vitro, silencing p75NTR-MSCs enhanced their secretome, as evidenced by significant increases in SDF-1, VEGF and NGF release in MSCs conditioned medium; improved paracrine angiogenic response in HREs, where HREs showed enhanced migration (1.4-Fold) and tube formation (2-Fold) compared to controls. In parallel, modulating MSCs-p75NTR using LM11A-31 resulted in a similar improvement in MSCs secretome and the enhanced paracrine angiogenic potential of HREs. Further, intervention with LM11A-31 significantly mitigated the decline in visual acuity post retinal I/R injury. In conclusion, p75NTR modulation can potentiate the therapeutic potential of MSCs to harness vascular repair in ischemic retinopathy diseases.

C-MYC Amplification in Chronic Lymphocytic Leukemia: A Case Report and Review of the Literature.

OBJECTIVES: Chronic lymphocytic leukemia (CLL) is among the most common forms of leukemia diagnosed in the United States. It is associated with a variety of clinically significant genetic abnormalities, including cytogenetic abnormalities that are assessed routinely. Herein, we present a case of CLL for which molecular cytogenetic analysis revealed concomitant deletion of TP53 (17p13.1) in 87% of cells analyzed and amplification (3-20 signals) of C-MYC (8q24.1) in 47% of cells analyzed. Although rearrangements involving C-MYC are common in CLL, amplification is a rarer phenomenon that has not been investigated as thoroughly and may be overlooked during routine analysis. We review this case in the context of available literature on the plethora of genetic abnormalities involving C-MYC in CLL and their relevance to the pathogenesis of the disease. All in all, this case highlights the role of comprehensive, multidisciplinary genetic testing in the management of CLL.

Cognitive training and neuroplasticity in mild cognitive impairment (COG-IT): protocol for a two-site, blinded, randomised, controlled treatment trial.

INTRODUCTION: Mild cognitive impairment (MCI) is common in older adults and represents a high-risk group for progression to Alzheimer's disease (AD). Medication trials in MCI have generally failed, but new discoveries with brain plasticity in ageing have led to the study of cognitive training as a potential treatment to improve cognitive abilities. Computerised cognitive training (CCT) involves computerised cognitive exercises that target specific cognitive abilities and neural networks to potentially improve cognitive functioning through neuroplasticity. METHODS AND ANALYSIS: In a two-site study (New York State Psychiatric Institute/Columbia University Medical Center and Duke University Medical Center), we will randomise 100 patients with MCI (Wechsler Memory Scale-III Logical Memory II score 0-11; Folstein Mini Mental State Examination ≥23) to home-based CCT (suite of exercises: memory, matching, spatial recognition, processing speed) or a home-based active control condition (computerised crossword puzzle training (CPT)) with 12 weeks of intensive training followed by regular booster sessions up to 78 weeks. All patients will receive standard neuropsychological and functional assessments in clinic as well as structural/functional brain MRI scans at study entry and endpoint. We will test if CCT, versus CPT, leads to improved cognitive functioning, transfers to functional ability and tasks of everyday life and impacts hippocampal volume changes and changes in the default mode network of the brain measured by resting-state functional MRI. ETHICS AND DISSEMINATION: The study will be conducted following ethics approval and written informed consent will be obtained from all subjects. Study results will be disseminated via publication, clinicaltrials.gov, media and conference presentations. This will be the first controlled long-term trial to evaluate the effects of home-based CCT versus computerised CPT on cognitive abilities and functional measures and neural outcomes as determined by MRI indices in patients with MCI. Positive results from trial may support further development of home-based CCT. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov identifier (NCT03205709).

Development of a replication-competent lentivirus assay for dendritic cell-targeting lentiviral vectors.

It is a current regulatory requirement to demonstrate absence of detectable replication-competent lentivirus (RCL) in lentiviral vector products prior to use in clinical trials. Immune Design previously described an HIV-1-based integration-deficient lentiviral vector for use in cancer immunotherapy (VP02). VP02 is enveloped with E1001, a modified Sindbis virus glycoprotein which targets dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin (DC-SIGN) expressed on dendritic cells in vivo. Vector enveloped with E1001 does not transduce T-cell lines used in standard HIV-1-based RCL assays, making current RCL testing formats unsuitable for testing VP02. We therefore developed a novel assay to test for RCL in clinical lots of VP02. This assay, which utilizes a murine leukemia positive control virus and a 293F cell line expressing the E1001 receptor DC-SIGN, meets a series of evaluation criteria defined in collaboration with US regulatory authorities and demonstrates the ability of the assay format to amplify and detect a hypothetical RCL derived from VP02 vector components. This assay was qualified and used to test six independent GMP production lots of VP02, in which no RCL was detected. We propose that the evaluation criteria used to rationally design this novel method should be considered when developing an RCL assay for any lentiviral vector.

Combined evaluation of commonly used techniques, including PCR, for diagnosis of mouse fur mites.

Our study evaluated and compared the false-negative rates (FNR) of a wide array of fur-mite diagnostic tests, including 2 postmortem tests (pelt exam and sticky paper) and 3 antemortem tests (adhesive tape, fur pluck, and PCR). Past publications examining fur-mite diagnostic techniques primarily used paired comparisons, evaluating tests by their level of agreement with only one other test. However, different combinations or pairs of diagnostics are used in the different studies, making the results of these comparisons difficult to interpret across all available diagnostics. In the current study, mice from a conventionally maintained colony endemic for Myobia musculi were identified as positive based on at least one positive diagnostic test. From this pool of positive animals, the FNR of all tests were quantified. The PCR assay and the pelt exam performed the best, with 0% and 2% FNR respectively, whereas tape, fur-pluck, and sticky-paper tests showed 24%, 26%, and 36% FNR, respectively. Our study shows that for mice in a colony naturally infested with Myobia musculi, PCR testing can be used for reliable antemortem detection, and pelt exam performed by experienced examiners is reliable for postmortem detection.

Effects of body orientation on maximum voluntary arm torques.

INTRODUCTION: Increased reliance on bulbospinal motor systems has been implicated in individuals with chronic stroke during maximum voluntary arm joint torque generation. METHODS: Maximum isometric single-joint and multi-joint arm strength was observed in two body orientations (sitting and supine) while maintaining identical head/neck/trunk/extremity joint configurations in order to identify bulbospinal contributions to maximum joint torque generation in 11 individuals with stroke and 10 individuals without stroke. RESULTS: During sitting, shoulder flexion was greater for both groups, whereas shoulder extension and elbow flexion, part of the "flexion synergy," were greater only in individuals with stroke. CONCLUSIONS: Body orientation influenced isometric arm strength, notably the constituents of flexion synergy in individuals with stroke, suggesting bulbospinal motor pathway involvement. From a practical perspective, clinical evaluation of single joint strength in the supine position may underestimate strength available during activities of daily living that are performed in an upright orientation.

The use-dependent, nicotinic antagonist BTMPS reduces the adverse consequences of morphine self-administration in rats in an abstinence model of drug seeking.

In this study, the use-dependent, nicotinic receptor antagonist bis (2,2,6,6-tetramethyl-4-piperidinyl) sebacate (BTMPS) was evaluated for its ability to attenuate the adverse consequences associated with morphine in rats in all three phases of an abstinence model of drug seeking: self-administration, acute withdrawal, and delayed test of drug seeking. Rats were allowed to self-administer morphine (FR1 schedule) with an active response lever, on a 24 h basis inside operant chambers, for 14 days. Each rat was subsequently evaluated for stereotypical behaviors associated with spontaneous morphine withdrawal. Rats were then placed in standard housing cages for a six week period of protracted abstinence from morphine. After this period, each rat was placed back into its respective operant chamber for a 14 day assessment of unrewarded drug seeking responses. BTMPS was administered to the animals in all three clinically relevant phases in three separate sets of experiments. BTMPS treatment during the self-administration phase resulted in up to a 34% reduction of lever responses to morphine when compared to vehicle treated control animals, as well as a 32% reduction in the dose of morphine self-administered. When given during self-administration and acute withdrawal, BTMPS treatment decreased acute withdrawal symptoms (up to 64%) of morphine use and reduced (up to 45%) drug seeking responses after six weeks of protracted withdrawal compared to control animals. BTMPS treatment after six weeks of abstinence from morphine had no effect. These results offer insight into the role of central cholinergic receptors in the onset and maintenance of drug addiction.

Effect of the use-dependent, nicotinic receptor antagonist BTMPS in the forced swim test and elevated plus maze after cocaine discontinuation in rats.

Withdrawal from cocaine use often is associated with anxiety and depressive states. In this study the use-dependent, nicotinic acetylcholine receptor antagonist bis-(2,2,6,6-tetramethyl-4-piperidinyl) sebacate (BTMPS) was studied for its ability to reduce these symptoms in two rat models of anxiety and depression. Rats were administered saline vehicle, or two escalating doses of cocaine, for a period of 5 days and they were evaluated during the period after cocaine discontinuation in the elevated plus maze (anxiety) and the forced swim test (affect). BTMPS (0.25, 0.5, or 0.75mg/kg) was co-administered with saline or cocaine in the dependence phase. Withdrawal from cocaine administration alone resulted in reductions in both the time spent in the open arms of the elevated plus maze test, as well as entries into, and out of, the open arms of the maze. Withdrawal from cocaine also resulted in a reduction of escape behaviors, and the time to first immobility, in the forced swim test. Treatment with BTMPS produced a reversal of cocaine-induced anxiety-like behaviors in the elevated plus maze, including an increase (up to 68%) in time spent in the open arms of the maze and an increase in the number of crossings between open and enclosed arms. BTMPS also reduced depressive-like behaviors associated with the forced swim test, including up to a 62% increase in the time to first immobility and a 50% increase in escape behavior. These results provide proof of concept for the development and use of cholinergic compounds in the treatment of substance abuse.

Effect of administration of the nicotinic acetylcholine receptor antagonist BTMPS, during nicotine self-administration, on lever responding induced by context long after withdrawal.

The use-dependent, nicotinic acetylcholine receptor antagonist bis-(2,2,6,6-tetramethyl-4-piperidinyl) sebacate (BTMPS) was studied for its potential to reduce the self-administration of nicotine in rats, as well as to reduce context-induced recidivistic-like behavior after a six-week period of cessation. Rats were allowed to self-administer nicotine (FR1 schedule) inside an operant chamber with a response lever active on a 24 h basis for 14 days. After the self-administration phase, the rats were returned to standard maintenance cages for a period of six weeks. At the end of six weeks the rats were returned to the operant chambers for 7 days and lever responses were recorded under conditions identical to the original self-administration phase, except that lever responses were not rewarded. Daily administration (s.c.) of BTMPS produced a dose-dependent decrease in the self-administration of nicotine 55-80% compared to control animals, and significantly decreased context-induced lever responding initiated six weeks after cessation (35-78% reduction vs. controls). Decreasing the BTMPS regimen to administration once every 3 days was not effective in reducing nicotine self-administration, but lever responding induced during the return to the operant chambers 6 weeks later was significantly decreased (40% reduction vs. controls). Therefore BTMPS can selectively reduce both self-administration of nicotine and long-term recidivistic-like behavior depending upon the dose regimen. Since BTMPS does not evoke anti-nicotinic effects under normal physiological conditions, these data support a proof of concept for the safe use of such compounds in the treatment of tobacco abuse.

Social capital and childhood psychiatric disorders: a cross-sectional study.

The aim of this research was to determine whether social capital is associated with either the type or severity of psychiatric disorders of childhood, specifically, disorders of emotion and behaviour. Ninety parents of children between the ages of 4 and 18 years with an emotional disorder or behavioural disorder participated in the study. They completed two questionnaires: the Child Behaviour Checklist (to assess severity of disorder) and a questionnaire measuring social capital. There was no statistically significant association between total social capital score and either diagnosis or severity of illness. However, two components of social capital showed significant associations: ;perceptions of the local area' was significantly associated with severity of illness and ;social networks' with diagnosis. The findings of this study suggest that some components of social capital may be more important in relation to mental health than others.

A rapid flow cytometric technique for the detection of platelet-monocyte complexes, activated platelets and platelet-derived microparticles.

Platelet activation occurs in a variety of clinical situations in which it directly contributes to the pathology. This study reports a simple flow cytometric assay for platelet activation which measures platelet-derived microparticles, activated platelets and platelet-monocyte complexes. Pre- and post analytical conditions were investigated and optimized and a normal range established on 20 healthy controls. Twenty patients pre- and post percutaneous coronary intervention (PCI) were tested with the technique. Soluble activation markers sCD40 ligand and sP-selectin and plasma phospholipid levels were measured in both groups. There was a significant increase in activated platelets and platelet-monocyte complexes between normal and pre-PCI (P = 0.005 and 0.0275, respectively) suggesting an activated state. There was a significant fall in activated platelets post-PCI (P = 0.0027) which was mirrored by a fall in soluble CD40 ligand, soluble P-selectin and plasma phospholipid levels (P = 0.0066, <0.0001 and 0.0032, respectively) consistent with antiplatelet therapy administered during the process. This is a reliable and rapid method for the assessment of ex vivo platelet activation which may be an aid in diagnosis and help guide therapy for patients with thrombotic disease.

A pilot study to predict success with guided imagery for cancer pain.

Guided imagery, as other nonpharmacologic strategies, has been demonstrated to be useful for some patients. However, no tested method exists to identify which patients are likely to benefit from this pain management strategy. This pilot study tested a model to predict success with guided imagery. Major concepts tested included imaging ability, outcome expectancy, history of imagery use, match with preferred coping style, and perceived credibility of the imagery provider. A one-group pretest-posttest design was used. A sample of 62 hospitalized cancer patients currently experiencing pain rated >/=3 on a 0 to 10 scale completed questionnaires and used an audiotaped imagery intervention. Pain outcomes examined included mean pain intensity and distress, positive and negative affect, and perceived control over pain. A path analysis was conducted using multiple regression to evaluate relationships proposed in the model. Previous history with imagery predicted outcome expectancy. Imaging ability predicted mean pain intensity, positive affect, and perceived control over pain. Outcome expectancy was not a significant predictor of any pain outcomes. Baseline status and concurrent symptoms, measured as covariates, also played a significant role in predicting outcomes. Variance explained in pain outcomes ranged from 10% to 52% (adjusted R(2) = 3% to 48%). Further exploration of model variables is warranted. Findings suggest that after considering current symptom experience, imaging ability may be a useful variable to assess in order to determine whether guided imagery is an appropriate intervention for individual patients.

Effect of Gender and Menopausal Status on the Pharmacokinetics of Tirilazad Mesylate in Healthy Subjects.

The pharmacokinetics of tirilazad were assessed in men ages 40--60 years, women <40 years of age, premenopausal women ages 40--60, and postmenopausal ages 40--60. Eight subjects in each group received single 3.0 mg kg(minus sign1) intravenous infusions of tirilazad mesylate over 10 min. Plasma concentrations of tirilazad and U-89678, an active metabolite, were measured by high-performance liquid chromatography. Tirilazad administration was well tolerated in all groups. Mean tirilazad clearance was 59.6% higher in young women compared to the middle-aged men (35.6 plus minus 8.04 L h(minus sign1) vs. 22.3 plus minus 8.40 L h(minus sign1)). Mean tirilazad clearance in middle-aged women was 30.7% higher than in middle-aged men. Mean clearance in postmenopausal women (26.1 plus minus 4.21 L h(minus sign1)) was not significantly different than that in middle-aged men, but clearance corrected for body weight was significantly different between the men and postmenopausal women. Clearance in premenopausal middle-aged women (32.2 plus minus 7.60 L h(minus sign1)) was not significantly different from that in young women and was 44% greater than that in middle-aged men. Mean AUC(0minus signinfty infinity) and C(max) values for U-89678 were significantly higher in men than in all of the female groups. Among the women, values for U-89678 AUC(0minus signinfty infinity) were lowest in young women (467 plus minus 345 ng h ml(minus sign1), 8.8% of male value) and highest in postmenopausal women (1565 plus minus 1382 ng h ml(minus sign1), 29.4% of male value). The absolute values for U-89678 AUC(0minus signinfty infinity) must be interpreted with caution, as limited assay sensitivity and low plasma concentrations in the latter portion of the concentration-time profile in women precluded accurate determination of the terminal half-life and AUC(0minus signinfty infinity). Regardless, these results show that women, particularly premenopausal women, have lower concentrations of U-89678, an active metabolite of tirilazad, than are achieved in men. The gender differences in tirilazad and U-89678 pharmacokinetics are of sufficient magnitude that they may impact the clinical response of male and female patients to tirilazad treatment.

Caffeine and Theobromine.

Two components of cocoa powder, caffeine (1,3,7-trimethylxanthine) and theobromine (3,7-dimethylxanthine), were evaluated for their effect on growth of L. monocytogenes strain V7. Caffeine (0.5%) and theobromine (2.5%) were added singly or in combination to skim milk or a modified tryptose phosphate broth (MTPB), which were sterilized, inoculated to contain ca. 1 × 103 CFU L. monocytogenes /ml, and incubated at 30°C. Both compounds allowed some growth of the pathogen; however, longer lag phases occurred in samples with (6 to 9 h) rather than without (<3 h) caffeine. Generation times at 30°C ranged from 1.10 h (2.5% theobromine in broth) to 2.28 h (2.5% theobromine plus 0.5% caffeine in milk). Generation times were significantly (p<0.05) lengthened in the presence (2.17 h) rather than in the absence (1.2 h) of caffeine. Populations in samples without caffeine were more than ten times greater (8.57 log10 CFU/ml) than in samples with caffeine (7.21 log10 CFU/ml). Theobromine concentration (0 or 2.5%) and substrate (MTPB or skim milk) had only limited effects on growth of the pathogen. The change in pH of the medium was a function of the extent of growth of L. monocytogenes and the buffering capacity of the substrate. A smaller pH change (0.09 unit) occurred in the milk medium than in broth (0.48 unit) because of the minimal buffering capacity of the 0.2% tryptose solution. Samples with caffeine had a small decrease in pH (0.07 unit) because growth of L. monocytogenes was inhibited and thus acid production was minimal.

Inhibition of Listeria monocytogenes by Cocoa in a Broth Medium and Neutralization of this Effect by Casein.

Dutch-processed cocoa (0.75 to 10.0%, w/v), when added to a broth medium, inhibited/inactivated Listeria monocytogenes strain V7. With agitated incubation at 30°C, samples with 5.0, 7.5, and 10.0% cocoa were free of detectable viable cells (<1/ml) 15 to 24 h after inoculation to contain ca. 1 × 105 L. monocytogenes strain V7/ml. Without agitation at 30°C, presence of 0.75 to 10.0% cocoa lengthened (1.02 to 1.12 h) the generation time of the pathogen when compared to samples without cocoa (0.94 h). However, the pathogen, in samples containing cocoa, eventually reached a higher (9.05 to 9.18 log10 CFU/ml) population than in samples without cocoa (8.81 log10 CFU/ml). The lag phase of L. monocytogenes was longer with (8.15 h) rather than without (4.41 h) agitation, at a lower (ca 1×103 CFU/ml) (6.92 h) rather than a higher (ca. 1 × 105 CFU/ml) (5.65 h) inoculum level, and in the presence of 0.75% (10.52 h) rather than 0% (2.04 h) cocoa. Higher maximum populations (9.18 log10 CFU/ml) developed in samples that were agitated rather than incubated quiescently (8.39 log10 CFU/ml), and in samples with (9.23 log10 CFU/ml) rather than without (8.88 log10 CFU/ml) cocoa. Casein (1.5 or 3.0%) relieved the inhibition when incubation was quiescent and inactivation of L. monocytogenes by cocoa when incubation was with agitation. Without agitation, the lag phase of the pathogen was extended in the presence of cocoa (4.01 h) compared to samples with cocoa and casein (1.77 to 2.74 h). Casein did not significantly (p>0.05) affect the maximum population attained by the pathogen, but presence of cocoa increased the maximum population (8.86 and 9.25 log10 CFU/ml for 0 and 5.0% cocoa). With agitation, presence of 5.0% cocoa completely inactivated the pathogen; however, addition of 2.5% casein to these samples allowed growth of L. monocytogenes to a population of 9.47 log10 CFU/ml (compared to 8.90 log10 CFU/ml in broth).

Behavior of Listeria monocytogenes in the Presence of Cocoa, Carrageenan, and Sugar in a Milk Medium Incubated With and Without Agitation.

Enhanced growth of Listeria monocytogenes strain V7 in chocolate milk rather than skim milk was further investigated by testing various concentrations of cocoa powder (two types of Dutch-process, designated A and B), cane sugar, and sodium carrageenan in skim milk at 13 and 30°C with and without agitated incubation. Increasing sugar concentrations (0, 6.5, and 12.0%) were marginally significant (p = 0.06) in shortening generation times (5.17, 5.07, and 5.05 h, respectively) of the pathogen. Maximum populations attained by the pathogen were greater when cocoa (0.75% type A or B) and sugar (6.5 or 12.0%) were present. Sugar concentration affected growth of L. monocytogenes in an approximately linear relationship (8.41, 8.67, 8.82 log10 CFU/ml for 0, 6.5, and 12.0% sugar, respectively) except in samples containing only carrageenan. In this instance, presence of 6.5 and 12.0% sugar resulted in equivalent maximum populations (8.54 and 8.52 log10 CFU/ml). Three factors enhanced growth of the pathogen at 30°C: addition of cocoa, addition of sugar, and agitated rather than quiescent incubation. Without cocoa, generation times of L. monocytogenes were longer (1.04 h) compared to presence of type A (0.87 h) or B (0.90 h) cocoa. L. monocytogenes in agitated samples had shorter (0.82 h) generation times than in quiescent cultures (0.95 h). Highest populations were attained in agitated samples containing sugar and type A (9.21 log10 CFU/ml) or type B (9.22 log10 CFU/ml) cocoa compared to lowest populations in quiescent samples of skim milk (8.56 log10 CFU/ml).