J. Elliot Carter

Colonization and Inflammation Deficiencies in Mongolian Gerbils Infected by Helicobacter pylori Chemotaxis Mutants

ABSTRACT Helicobacter pylori causes disease in the human stomach and in mouse and gerbil stomach models. Previous results have shown that motility is critical for H. pylori to colonize mice, gerbils, and other animal models. The role of chemotaxis, however, in colonization and disease is less well understood. Two genes in the H. pylori chemotaxis pathway, cheY and tlpB, which encode the chemotaxis response regulator and a methyl-accepting chemoreceptor, respectively, were disrupted. The cheY mutation was complemented with a wild-type copy of cheY inserted into the chromosomal rdxA gene. The cheY mutant lost chemotaxis but retained motility, while all other strains were motile and chemotactic in vitro. These strains were inoculated into gerbils either alone or in combination with the wild-type strain, and colonization and inflammation were assessed. While the cheY mutant completely failed to colonize gerbil stomachs, the tlpB mutant colonized at levels similar to those of the wild type. With the tlpB mutant, there was a substantial decrease in inflammation in the gerbil stomach compared to that with the wild type. Furthermore, there were differences in the numbers of each immune cell in the tlpB-mutant-infected stomach: the ratio of lymphocytes to neutrophils was about 8 to 1 in the wild type but only about 1 to 1 in the mutant. These results suggest that the TlpB chemoreceptor plays an important role in the inflammatory response while the CheY chemotaxis regulator plays a critical role in initial colonization. Chemotaxis mutants may provide new insights into the steps involved in H. pylori pathogenesis.

Helicobacter pylori Chemotaxis Modulates Inflammation and Bacterium-Gastric Epithelium Interactions in Infected Mice

ABSTRACT The ulcer-causing pathogen Helicobacter pylori uses directed motility, or chemotaxis, to both colonize the stomach and promote disease development. Previous work showed that mutants lacking the TlpB chemoreceptor, one of the receptors predicted to drive chemotaxis, led to less inflammation in the gerbil stomach than did the wild type. Here we expanded these findings and examined the effects on inflammation of completely nonchemotactic mutants and mutants lacking each chemoreceptor. Of note, all mutants colonized mice to the same levels as did wild-type H. pylori. Infection by completely nonchemotactic mutants (cheW or cheY) resulted in significantly less inflammation after both 3 and 6 months of infection. Mutants lacking either the TlpA or TlpB H. pylori chemotaxis receptors also had alterations in inflammation severity, while mutants lacking either of the other two chemoreceptors (TlpC and HylB) behaved like the wild type. Fully nonchemotactic and chemoreceptor mutants adhered to cultured gastric epithelial cells and caused cellular release of the chemokine interleukin-8 in vitro similar to the release caused by the wild type. The situation appeared to be different in the stomach. Using silver-stained histological sections, we found that nonchemotactic cheY or cheW mutants were less likely than the wild type to be intimately associated with the cells of the gastric mucosa, although there was not a strict correlation between intimate association and inflammation. Because others have shown that in vivo adherence promotes inflammation, we propose a model in which H. pylori uses chemotaxis to guide it to a productive interaction with the stomach epithelium.

Gastrointestinal Stromal Tumors A Review of the Literature

Gastrointestinal stromal tumors are mesenchymal neoplasms with a spectrum of histologic appearances and biologic activity. The morphologic classification of these lesions has evolved over time, and molecular analysis has led to a better understanding of their nature. The histologic differential diagnosis for these lesions is broad and includes many spindle cell lesions of the gastrointestinal tract, including neoplasms of true smooth muscle and neural origin, proliferating fibrous lesions, metastatic neoplasms, and primary sarcomas of vascular and adipose origin. Immunohistochemical studies that include CD117 have become invaluable in the classification of mesenchymal lesions arising in the gastrointestinal tract. Treatment of gastrointestinal stromal tumors has historically been involved surgery, but the use of the chemotherapeutic agent imatinib mesylate for advanced disease has made accurate classification even more important. The molecular features have not only allowed us to understand the pathogenesis of these tumors but also have proven to be associated with response to kinase inhibitors.

The Degree of Helicobacter pylori-Triggered Inflammation Is Manipulated by Preinfection Host Microbiota

ABSTRACT Helicobacter pylori infects over 3 billion people worldwide and is the primary risk factor for gastric cancer. Most individuals infected with H. pylori develop only asymptomatic gastritis; however, some develop ulcers or gastric adenocarcinoma. We demonstrate that one previously unappreciated parameter influencing H. pylori disease outcome is variation in the preinfection host microbiota. Utilizing a mouse model, we altered the microbiota by antibiotic treatment and found that these alterations resulted in significantly lowered H. pylori-triggered inflammation. Specifically, antibiotic pretreatment reduced CD4+ T-helper cells and Ifnγ transcript levels in gastric tissue after H. pylori infection. The bacterial communities in mice with a reduced response to H. pylori displayed many differences from those in untreated mice, including significantly more cluster IV and XIVa Clostridium spp., bacteria known to influence inflammation via regulatory T cell populations. Our findings suggest that microbiota composition, perhaps Clostridium spp., contributes to the variable disease outcome of H. pylori infection by altering the recruitment of CD4+ T cells to the gastric compartment. Our results suggest that gastric microbiota could be used as a diagnostic tool to determine which patients are at risk for developing severe disease.

Association of Cervical Cytology and HPV DNA Status During Pregnancy With Placental Abnormalities and Preterm Birth

The clinical implications of abnormal cervical cytology during pregnancy are unclear. Therefore, we performed the present study to determine the role of cervical cytologic screening during pregnancy in association with placental abnormalities and preterm birth. A review of 2,480 cases during 11 years revealed significant correlation of reactive, infectious, atypical, and dysplastic cytologic changes during pregnancy with abnormal placental findings. Also, all but dysplastic cytologic changes were significantly associated with preterm birth. Furthermore, we observed significant association of the presence of high-risk human papillomavirus (HPV) DNA with preterm birth and placental abnormalities. These findings indicate that cervical infection of HPV is a risk factor for preterm birth and that cervical cytology is an effective tool for screening women for infection and inflammation during pregnancy and predicting pregnancy outcome.

Helicobacter pylori Requires TlpD-Driven Chemotaxis To Proliferate in the Antrum

ABSTRACT Different disease outcomes of Helicobacter pylori infection correlate with distinct inflammation patterns. These different inflammatory distributions may be initiated by differences in bacterial localization. One H. pylori property known to affect murine stomach localization is chemotaxis, the ability to move in response to chemical cues. In this report, we used nonchemotactic mutants (Che−) to analyze whether chemotaxis is required for initial colonization of particular stomach regions or for subsequent growth therein. We found that H. pylori behaves differently in the corpus, antrum, and corpus-antrum transition zone subregions of the stomach. This outcome suggests that these regions contain unique chemotactic signals. In the corpus, H. pylori utilizes chemotaxis for initial localization but not for subsequent growth. In contrast, in the antrum and the corpus-antrum transition zone, chemotaxis does not help initial colonization but does promote subsequent proliferation. To determine which chemoreceptor is responsible for the corpus-antrum phenotypes, we infected mice with strains lacking each chemoreceptor. Strains lacking TlpA, TlpB, or TlpC displayed only modest deviations from the wild-type phenotype, while strains lacking TlpD resembled the Che− mutant in their antral colonization defect and fared even worse than the Che− mutant in the corpus. Additional analysis showed that inflammation is worse in the antrum than in the corpus in both wild-type and Che− mutant infections. These results suggest that chemotaxis, specifically, that controlled by TlpD, is necessary for H. pylori to survive or grow in the environment of increased inflammation in the antrum.

Bacterial chemotaxis modulates host cell apoptosis to establish a T-helper cell, type 17 (Th17)-dominant immune response in Helicobacter pylori infection

The host inflammatory response to chronic bacterial infections often dictates the disease outcome. In the case of the gastric pathogen Helicobacter pylori, host inflammatory responses result in outcomes that range from moderate and asymptomatic to more severe with concomitant ulcer or cancers. It was found recently that H. pylori chemotaxis mutants (Che−), which lack directed motility but colonize to nearly wild-type levels, trigger less host inflammation. We used these mutants to observe host immune responses that resulted in reduced disease states. Here we report that these mutants are defective for early gastric recruitment of CD4+ T cells compared with wild-type infection. Furthermore, Che− mutant infections lack the T-helper cell, type 17 (Th17) component of the immune response, as measured by cytokine mRNA levels in gastric tissue via intracellular cytokine staining and immunofluorescence. We additionally find that a Che− mutant infection results in significantly less host cell apoptosis than does wild-type infection, in accordance with previous observations that T-helper cell, type 17 responses in Citrobacter rodentium infections are driven by concomitant bacterial and apoptotic cell signals. We propose that bacterial chemotaxis allows H. pylori to access a particular host niche that allows the bacteria to express or deliver proapoptotic host cell factors. This report indicates that chemotaxis plays a role in enhancing apoptosis, suggesting bacterial chemotaxis systems might serve as therapeutic targets for infections whose symptoms arise from host cell apoptosis and tissue damage.

Empyema Necessitatis Due to Methicillin-Resistant Staphylococcus aureus: Case Report and Review of the Literature

ABSTRACT Empyema necessitatis is a rare complication of empyema in which the pleural infection spreads outside of the pleural space to involve the soft tissues of the chest wall. Most cases of empyema necessitatis are related to Mycobacterium tuberculosis and, less commonly, to Actinomyces spp. and Streptococcus spp. Staphylococcus aureus has rarely been reported as the causative agent of empyema necessitatis, with the majority of S. aureus isolates being methicillin sensitive. Only two cases of empyema necessitatis due to methicillin-resistant S. aureus (MRSA) have been reported in the medical literature. We report the case of a 59-year-old Caucasian male who presented to our institution with complaints of pain in and swelling of his left upper chest of 2-months duration. A computed tomography scan of the chest showed an 8.1- by 6.5-cm lesion which extended from the left upper lobe of the lung into the extrathoracic soft tissues beneath the left upper pectoralis muscle. A wedge resection of the left upper lung lobe revealed lung tissue with an organized pneumonia-like pattern associated with marked acute pleuritis. Blood and urine cultures and cultures of the left chest soft tissue mass grew MRSA. The patient was successfully treated with vancomycin followed by a 10-day outpatient course of ciprofloxacin and trimethoprim-sulfamethoxazole. This case represents an extremely rare manifestation of an increasingly dangerous bacterial pathogen.

Clinically Significant Kluyvera Infections

To determine the clinical significance of Kluyvera isolates at our institution, we retrospectively analyzed clinical microbiology data from January 1999 to September 2003. We identified 11 isolates classified as Kluyvera ascorbata, 7 of which were considered clinically significant pathogens: 3 cases represented urinary tract infections; 2, bacteremia; 1, a soft tissue infection of the finger; and 1, acute appendicitis with a subsequent intra-abdominal abscess. The age distribution of patients was wide, ranging from 2 months to 73 years. Antimicrobial susceptibility studies of the clinically significant and non–clinically significant Kluyvera isolates showed susceptibility patterns similar to those reported in the medical literature, namely trends of resistance to ampicillin and first- and second-generation cephalosporins. Of the 4 non–clinically significant isolates in our study, 1 was resistant to ciprofloxacin, a finding reported in only 1 other isolate of Kluyvera in the medical literature. Patient outcome after treatment with third-generation cephalosporins and aminoglycosides in the 7 clinically significant cases was good, with no long-term sequelae. The potential virulence of K ascorbata highlights the need for heightened scrutiny of its antimicrobial susceptibility patterns for adequate clinical treatment.

Neonatal Candida parapsilosis meningitis and empyema related to epidural migration of a central venous catheter

Candida parapsilosis is an extremely rare cause of meningitis. We report the case of a neonate born at 26+4 weeks of gestation who was admitted to the neonatal intensive care unit at our institution due to respiratory immaturity. During the course of a 3-month hospitalization, the neonate developed fever and lethargy. A lumbar puncture revealed milky-white, turbid cerebrospinal fluid which contained many nucleated cells, mostly neutrophils. Microscopic examination of the cerebrospinal fluid revealed marked acute inflammation and fungal yeast forms, and cultures of the cerebrospinal fluid and peripheral blood yielded C. parapsilosis. Imaging studies subsequently revealed a subdural empyema related to epidural migration of a central venous catheter (CVL). The neonate received extended therapy with amphotericin B and fluconazole. He responded favorably to therapy and was discharged 3 months after birth. This case underscores the clinical importance of the recognition and treatment of a potentially lethal fungal pathogen of the central nervous system and the need for awareness of complications resulting from CVL malposition.