Anteneh Addisu

B-Type Natriuretic Peptide Decreases Gastric Emptying and Absorption

Natriuretic peptides have been shown to decrease contractility of isolated gastric smooth muscle cells. However there is a paucity of research showing whether this effect has functional significance in the whole animal. The objective of this study was to test whether intravenously administered B-type Natriuretic Peptide (BNP) has an effect on gastric emptying and/or absorption in a whole animal mouse model. C57BL/6-Wild-type (WT) and Natriuretic Peptide Receptor type A (NPR-A) knockout (KO) mice were used in these studies. Gastric contractility was examined in anesthetized mice before and after BNP vs. vehicle injection. Gastric emptying of gavage fed 70 Kilo Dalton (kDa) FITC-dextran and absorption of 4 kDa FITC-dextran were compared in BNP vs. vehicle treated conscious WT and KO mice. BNP decreased gastric contractility (measured in change in intragastric pressure) from 2.26 ± 0.29 to 1.44 ± 0.11 mmHg (P < 0.05), pressure returned to 2.08 ± 0.17 after 5 BNP half-lives (P < 0.05). There was no significant change in the vehicle or KO. BNP also decreased gastric emptying in WT mice compared to vehicle, 87.8 ± 0.8% vs. 97.3 ± 1.04% (P < 0.05) and this effect showed a dose-response relationship. In KO mice emptying was 95.8 ± 0.5% (BNP) vs. 91.7 ± 0.7% (Vehicle) (P > 0.05). The absorption in WT mice was 28.2 ± 7.8 (relative fluorescence units) for BNP vs. 91 ± 25.9 for vehicle (P < 0.05). For KO mice absorption was 64.3 ± 14.9 for BNP vs. 60.6 ± 17.4 for vehicle (P > 0.05). The results show that BNP decreases intragastric pressure, emptying and absorption by acting via the NPR-A receptor. We postulate that this effect is aimed at decreasing preload through decreased water and electrolyte absorption from the GI tract and may also be responsible for the symptoms of impaired gastrointestinal function observed in heart failure patients.

Bartonella Species, an Emerging Cause of Blood-Culture-Negative Endocarditis

SUMMARY Since the reclassification of the genus Bartonella in 1993, the number of species has grown from 1 to 45 currently designated members. Likewise, the association of different Bartonella species with human disease continues to grow, as does the range of clinical presentations associated with these bacteria. Among these, blood-culture-negative endocarditis stands out as a common, often undiagnosed, clinical presentation of infection with several different Bartonella species. The limitations of laboratory tests resulting in this underdiagnosis of Bartonella endocarditis are discussed. The varied clinical picture of Bartonella infection and a review of clinical aspects of endocarditis caused by Bartonella are presented. We also summarize the current knowledge of the molecular basis of Bartonella pathogenesis, focusing on surface adhesins in the two Bartonella species that most commonly cause endocarditis, B. henselae and B. quintana. We discuss evidence that surface adhesins are important factors for autoaggregation and biofilm formation by Bartonella species. Finally, we propose that biofilm formation is a critical step in the formation of vegetative masses during Bartonella-mediated endocarditis and represents a potential reservoir for persistence by these bacteria.

Heart failure mice exhibit decreased gastric emptying and intestinal absorption

Our recent study showed that intravenously administered B-type natriuretic peptide (BNP) decreases gastric emptying and intestinal absorption in mice. We aimed to test whether acute myocardial injury and heart failure have similar effects. Wild-type (WT) and natriuretic peptide receptor type A (NPR-A) knockout (KO) mice underwent cryoinfarction (myocardial infarction [MI]) of the left ventricle (LV) versus sham. LV dysfunction was confirmed by echocardiography. Percent gastric emptying and intestinal absorption were measured and analyzed one and two weeks after infarction, by gavage feeding the mice with fluorescein-isothiocyanate-dextran. Ejection fraction was 48 ± 3% versus 64 ± 2% (P < 0.05) and fractional shortening was 24 ± 2% versus 35 ± 2% (P < 0.01), MI versus sham, respectively. BNP levels (pg/mL) were 4292 ± 276 one week after MI versus 105 ± 11 in sham (n = 5, P < 0.05) and 1964 ± 755 two weeks after MI (n = 5, P < 0.05). Gastric emptying was significantly decreased, 68 ± 6% in MI versus 89 ± 3% in sham (n = 5, P < 0.05) one week after MI and 82 ± 0.5% versus 98 ± 0.4%, MI versus sham (n = 5, P < 0.05), two weeks post-MI. Absorption, measured in relative plasma fluorescence units in WT mice, was 350 ± 79 in MI versus 632 ± 121 in sham (n = 6, P < 0.05). KO mice did not show a significant difference in emptying or absorption compared with sham. These findings suggest that MI and LV dysfunction decrease gastric emptying and absorption in mice through a mechanism that involves NPR-A.

Antibiotic Resistance and Toxin Production of Clostridium difficile Isolates from the Hospitalized Patients in a Large Hospital in Florida

Clostridium difficile is an important cause of nosocomial acquired antibiotic-associated diarrhea causing an estimated 453,000 cases with 29,000 deaths yearly in the U.S. Both antibiotic resistance and toxin expression of C. difficile correlate with the severity of C. difficile infection (CDI). In this report, a total of 139 C. difficile isolates from patients diagnosed with CDI in Tampa General Hospital (Florida) in 2016 were studied for antibiotic resistance profiles of 12 types of antibiotics and toxin production. Antibiotic resistance determined by broth microdilution method showed that strains resistant to multi-antibiotics are common. Six strains (4.32%) showed resistance to six types of antibiotics. Twenty strains (14.39%) showed resistance to five types of antibiotics. Seventeen strains (12.24%) showed resistance to four types of antibiotics. Thirty-nine strains (28.06%) showed resistance to three types of antibiotic. Thirty-four strains (24.46%) showed resistance to two types of antibiotics. While, all isolates were susceptible to metronidazole, and rifaximin, we found that one isolate (0.72%) displayed resistance to vancomycin (MIC ≥ 8 μg/ml), and another one was resistant to fidaxomicin (MIC >1 μg/ml). The percentage of isolates resistant to cefoxitin, ceftriaxone, chloramphenicol, ampicillin, clindamycin, erythromycin, gatifloxacin, and moxifloxacin was 75.54, 10.79, 5.76, 67.63, 82.70, 45.32, 28.06, and 28.78%, respectively. Toxin profiling by PCR showed the isolates include 101 (72.66%) A+B+CDT-strains, 23 (16.55%) A+B+CDT+ strains, 3 (2.16%) A-B+CDT+ strains, 1 (0.72%) A-B+CDT-strains, and 11 (7.91%) A-B-CDT-strains. Toxin production determined by ELISA using supernatants of bacterial culture harvested at 12, 24, 48, and 72 h of post inoculation (hpi) showed that the toxins were mainly produced between 48 and 72 hpi, and toxin B (TcdB) was produced faster than toxin A (TcdA) during the experimental time (72 hpi). In addition, the binary-positive strains were likely to yield more toxins compared to the binary-negative strains. This work contributes to the current understanding of the antibiotic resistance and virulence of C. difficile clinical strains.

Nontuberculous Mycobacteria Isolates at a Cancer Center: A 5-year Experience at H. Lee Moffitt Cancer Center in Tampa, Florida

Abstract Background Nontuberculous Mycobacteriae (NTM) are widely distributed in natural environments and are known to cause human diseases distinct from tuberculous mycobacteria. NTM caused diseases may lead to significant morbidity and mortality, particularly in immunocompromised hosts such as cancer patients. We present here a 5-year experience of NTM isolates at the Moffitt Cancer Center and research institute in Tampa, Florida. Methods We conducted a single center, retrospective study of patients with NTM from January 2011 to February 2016. Records were searched to identify patients with NTM. Specimens included bronchial lavage, swabs, blood, body fluids and biopsy or excised surgical specimens. Basic demographics of patients, clinical attributes, presentation and sites from which the NTM were isolated and associated neoplastic pathologies were evaluated for each NTM type and compared. Results There were a total of 208 isolates of NTM during the 5-year study period. 86/208 (41%) of the isolates were Mycobacterium avium complex (MAC). Mycobacterium abscessus, gordonae and fortuitum accounted for 26%, 11% and 6% of the top four isolates respectively. There was no significant difference in types of NTM isolated based on the type of underlying neoplasm. Over half of the cases were from the respiratory tract, majority with lung nodule referred to rule out cancer. Skin/wound isolates accounted for 13% (majority from breast lesions) and blood/serologic diagnosis accounted for 7 % of the isolates. Average age of patients was 68 ± 11 years, 92% were US born and over 70% had smoking history. Conclusion NTM isolated in a referral cancer center setting are likely to be from the work up of PET positive pulmonary nodules and the majority isolates were MAC, followed closely by M. abscessus. With high level of resistance and few therapeutic options, the rise of M. abscessus pulmonary diseases is cause for concern. Even though the respiratory tract was the most common site of NTM isolation, we did’nt find association between types of NTM and a given neoplasm. Our finding may have been confounded by referral pattern to our center and the retrospective design. Future studies that lead to improved testing and scoring algorithms for NTM could reduce the rate of surgical excision of pulmonary nodules. Disclosures All authors: No reported disclosures.

Neurosyphilis and HIV Infection

Syphilis and HIV are both diseases of major public health importance globally, affecting tens of millions of people and leading to millions of deaths every year. There is a complex demographic, epidemiologic, and biologic interaction between the HIV virus and Treponema pallidum, the causative agent of syphilis. These interactions lead not only to higher rates of coinfection but also are believed to affect pathogenic mechanisms that result in early central nervous system syphilis among HIV-coinfected patients. Acute syphilitic meningitis and neuro-ophthalmologic syphilitic involvement are also believed to occur at a higher rate and early in the course of syphilis among HIV-coinfected individuals. There needs to be a higher index of suspicion for syphilitic involvement of the CNS among HIV patients especially those with ophthalmological and/or ontological complaints. While there may need to be subtle differences, current recommendations for diagnostic workup for neurosyphilis in HIV-coinfected patients are similar to that of non-HIV patients. Intravenous penicillin remains the treatment of choice for neurosyphilis.

Gene Therapy Blueprints for NeuroAIDS

Since the start of the HIV/AIDS pandemic, 37 years ago, early work produced evidence for CNS involvement and that HIV-1B infection could penetrate the brain. Since then, a plethora of studies further identified many host proteins, RNAs, and genes implicated in brain involvement consequent to HIV-1B infection. This chapter summarizes the various types of gene therapy platforms available in recent years for neuroAIDS. This is both important and complex and should be validated meticulously to reduce the risk of malfunction of genes and network pathways other than those under the specific molecular treatments intended. Consequently, we describe several of the genes known to be involved in neuroAIDS for potential application for various techniques of gene therapy. With more than 179,962 publications using gene therapy, as of February 27, 2017, where are all the clinically appropriate products applying all this knowledge? Ethical considerations of gene modification are discussed as well.

Neuronal Apoptotic Pathways in HIV-Associated Dementia, Alzheimer’s Disease, Parkinson’s Disease, and Huntington’s Disease

Dementia is one of the most devastating healthcare problems in the twenty-first century and involves cognitive impairment with persistent increased dependency and expense of care. Under the panoply of NeuroAIDS, the dementia resulting from human immunodeficiency virus (HIV) infection is termed HIV-associated dementia (HAD). Alzheimer’s disease (AD) is associated with the elderly population over 55 years old, and its prevalence increases with age. Parkinson’s disease (PD) also affects people in old age, and its pathological hallmark involves eosinophilic cytoplasmic inclusions, Lewy bodies. Huntington’s disease (HD) is an autosomal dominant genetic disorder caused by HD gene dysfunction and results in cortical thinning and ventricular enlargement. This chapter reviews the literature on the apoptotic pathways involved in the pathogenesis of these four dementias. Topics include intra-, inter-, and extracellular reactions, biochemical pathway changes, and signaling affecting neurons. Despite clinical differences among the four dementias, related molecular pathways and signaling patterns emerge. Individual-focused, evidence-based, translational healthcare brings this perspective into the twenty-first century.