Elizabeth L. Hohmann

Central nervous system infection with Listeria monocytogenes. 33 years' experience at a general hospital and review of 776 episodes from the literature.

We reviewed 776 previously reported and 44 new cases of CNS listeriosis outside of pregnancy and the neonatal period, and evaluated the epidemiologic, diagnostic, and therapeutic characteristics of this infection. Among patients with Listeria meningitis/meningoencephalitis, hematologic malignancy and kidney transplantation were the leading predisposing factors, but 36% of patients had no underlying diseases recognized. The infection occurred throughout life, with a higher incidence before the age of 3 and after the age of 45-50 years. Fever, altered sensorium, and headache were the most common symptoms, but 42% of patients had no meningeal signs on admission. Compared with patients with acute meningitis due to other bacterial pathogens, patients with Listeria infection had a significantly lower incidence of meningeal signs, and the CSF profile was significantly less likely to have a high WBC count or a high protein concentration. Gram stain of CSF was negative in two-thirds of cases of CNS listeriosis. One-third of patients had focal neurologic findings, and approximately one-fourth developed seizures over their course. Mortality was 26% overall, and was higher among patients with seizures and those older than 65 years of age. Relapse occurred in 7% of episodes. Ampicillin for a minimum of 15-21 days (with an aminoglycoside for at least the first 7-10 days) remains the treatment of choice. Cerebritis/abscess due to L. monocytogenes, without meningeal involvement, is less common but may be diagnosed by blood cultures and CNS imaging, or by stereotactic biopsy. Longer antibiotic therapy (at least 5-6 weeks) is needed in the presence of localized CNS involvement.

Oral, Capsulized, Frozen Fecal Microbiota Transplantation for Relapsing Clostridium difficile Infection

IMPORTANCE Fecal microbiota transplantation (FMT) has been shown to be effective in treating relapsing or refractory Clostridium difficile infection, but practical barriers and safety concerns have prevented its widespread use. OBJECTIVE To evaluate the safety and rate of resolution of diarrhea following administration of frozen FMT capsules from prescreened unrelated donors to patients with recurrent C. difficile infection. DESIGN, SETTING, AND PARTICIPANTS Open-label, single-group, preliminary feasibility study conducted from August 2013 through June 2014 at Massachusetts General Hospital, Boston. Twenty patients (median age, 64.5 years; range, 11-89 years) with at least 3 episodes of mild to moderate C. difficile infection and failure of a 6- to 8-week taper with vancomycin or at least 2 episodes of severe C. difficile infection requiring hospitalization were enrolled. INTERVENTIONS Healthy volunteers were screened as potential donors and FMT capsules were generated and stored at -80°C (-112°F). Patients received 15 capsules on 2 consecutive days and were followed up for symptom resolution and adverse events for up to 6 months. MAIN OUTCOMES AND MEASURES The primary end points were safety, assessed by adverse events of grade 2 or above, and clinical resolution of diarrhea with no relapse at 8 weeks. Secondary end points included improvement in subjective well-being per standardized questionnaires and daily number of bowel movements. RESULTS No serious adverse events attributed to FMT were observed. Resolution of diarrhea was achieved in 14 patients (70%; 95% CI, 47%-85%) after a single capsule-based FMT. All 6 nonresponders were re-treated; 4 had resolution of diarrhea, resulting in an overall 90% (95% CI, 68%-98%) rate of clinical resolution of diarrhea (18/20). Daily number of bowel movements decreased from a median of 5 (interquartile range [IQR], 3-6) the day prior to administration to 2 (IQR, 1-3) at day 3 (P = .001) and 1 (IQR, 1-2) at 8 weeks (P < .001). Self-ranked health scores improved significantly on a scale of 1 to 10 from a median of 5 (IQR, 5-7) for overall health and 4.5 (IQR, 3-7) for gastrointestinal-specific health on the day prior to FMT to 8 (IQR, 7-9) after FMT administration for both overall and gastrointestinal health (P = .001). Patients needing a second treatment to obtain resolution of diarrhea had lower pretreatment health scores (median, 6.5 [IQR, 5-7.3] vs 5 [IQR, 2.8-5]; P = .02). CONCLUSIONS AND RELEVANCE This preliminary study among patients with relapsing C. difficile infection provides data on adverse events and rates of resolution of diarrhea following administration of FMT using frozen encapsulated inoculum from unrelated donors. Larger studies are needed to confirm these results and to evaluate long-term safety and effectiveness. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT01914731.

Fecal Microbiota Transplant for Treatment of Clostridium difficile Infection in Immunocompromised Patients

OBJECTIVES:Patients who are immunocompromised (IC) are at increased risk of Clostridium difficile infection (CDI), which has increased to epidemic proportions over the past decade. Fecal microbiota transplantation (FMT) appears effective for the treatment of CDI, although there is concern that IC patients may be at increased risk of having adverse events (AEs) related to FMT. This study describes the multicenter experience of FMT in IC patients.METHODS:A multicenter retrospective series was performed on the use of FMT in IC patients with CDI that was recurrent, refractory, or severe. We aimed to describe rates of CDI cure after FMT as well as AEs experienced by IC patients after FMT. A 32-item questionnaire soliciting demographic and pre- and post-FMT data was completed for 99 patients at 16 centers, of whom 80 were eligible for inclusion. Outcomes included (i) rates of CDI cure after FMT, (ii) serious adverse events (SAEs) such as death or hospitalization within 12 weeks of FMT, (iii) infection within 12 weeks of FMT, and (iv) AEs (related and unrelated) to FMT.RESULTS:Cases included adult (75) and pediatric (5) patients treated with FMT for recurrent (55%), refractory (11%), and severe and/or overlap of recurrent/refractory and severe CDI (34%). In all, 79% were outpatients at the time of FMT. The mean follow-up period between FMT and data collection was 11 months (range 3–46 months). Reasons for IC included: HIV/AIDS (3), solid organ transplant (19), oncologic condition (7), immunosuppressive therapy for inflammatory bowel disease (IBD; 36), and other medical conditions/medications (15). The CDI cure rate after a single FMT was 78%, with 62 patients suffering no recurrence at least 12 weeks post FMT. Twelve patients underwent repeat FMT, of whom eight had no further CDI. Thus, the overall cure rate was 89%. Twelve (15%) had any SAE within 12 weeks post FMT, of which 10 were hospitalizations. Two deaths occurred within 12 weeks of FMT, one of which was the result of aspiration during sedation for FMT administered via colonoscopy; the other was unrelated to FMT. None suffered infections definitely related to FMT, but two patients developed unrelated infections and five had self-limited diarrheal illness in which no causal organism was identified. One patient had a superficial mucosal tear caused by the colonoscopy performed for the FMT, and three patients reported mild, self-limited abdominal discomfort post FMT. Five (14% of IBD patients) experienced disease flare post FMT. Three ulcerative colitis (UC) patients underwent colectomy related to course of UC >100 days after FMT.CONCLUSIONS:This series demonstrates the effective use of FMT for CDI in IC patients with few SAEs or related AEs. Importantly, there were no related infectious complications in these high-risk patients.

Fecal Microbiota Transplant for Relapsing Clostridium difficile Infection Using a Frozen Inoculum From Unrelated Donors: A Randomized, Open-Label, Controlled Pilot Study

BACKGROUND Recurrent Clostridium difficile infection (CDI) with poor response to standard antimicrobial therapy is a growing medical concern. We aimed to investigate the outcomes of fecal microbiota transplant (FMT) for relapsing CDI using a frozen suspension from unrelated donors, comparing colonoscopic and nasogastric tube (NGT) administration. METHODS Healthy volunteer donors were screened and a frozen fecal suspension was generated. Patients with relapsing/refractory CDI were randomized to receive an infusion of donor stools by colonoscopy or NGT. The primary endpoint was clinical resolution of diarrhea without relapse after 8 weeks. The secondary endpoint was self-reported health score using standardized questionnaires. RESULTS A total of 20 patients were enrolled, 10 in each treatment arm. Patients had a median of 4 (range, 2-16) relapses prior to study enrollment, with 5 (range, 3-15) antibiotic treatment failures. Resolution of diarrhea was achieved in 14 patients (70%) after a single FMT (8 of 10 in the colonoscopy group and 6 of 10 in the NGT group). Five patients were retreated, with 4 obtaining cure, resulting in an overall cure rate of 90%. Daily number of bowel movements changed from a median of 7 (interquartile range [IQR], 5-10) the day prior to FMT to 2 (IQR, 1-2) after the infusion. Self-ranked health score improved significantly, from a median of 4 (IQR, 2-6) before transplant to 8 (IQR, 5-9) after transplant. No serious or unexpected adverse events occurred. CONCLUSIONS In our initial feasibility study, FMT using a frozen inoculum from unrelated donors is effective in treating relapsing CDI. NGT administration appears to be as effective as colonoscopic administration. CLINICAL TRIALS REGISTRATION NCT01704937.

Safety and immunogenicity of phoP/phoQ-deleted Salmonella typhi expressing Helicobacter pylori urease in adult volunteers

Salmonella typhi Ty800, deleted for the Salmonella phoP/phoQ virulence regulon has been shown to be a safe and immunogenic single dose oral typhoid fever vaccine in volunteers. This promising vaccine strain was modified to constitutively express a heterologous protein of Gram negative bacterial origin, Helicobacter pylori urease subunits A and B, yielding S. typhi strain Ty1033. Seven volunteers received single oral doses of > or = 10(10) colony forming units of Ty1033; an eighth volunteer received two doses 3 months apart. Side effects were similar to those observed previously in volunteers who received the unmodified vector Ty800. All volunteers had strong mucosal immune responses to vaccination as measured by increases in IgA-secreting cells in peripheral blood directed against S. typhi antigens. Seven of eight volunteers had convincing seroconversion as measured by increases in serum IgG directed against S. typhi flagella and lipopolysaccharide antigens by ELISA. No volunteer had detectable mucosal or humoral immune responses to the urease antigen after immunization with single doses of Ty1033. A subset of three volunteers received an oral booster vaccination consisting of recombinant purified H. pylori urease A/B and E. coli heat labile toxin adjuvant 15 days after immunization with Ty1033. None of three had detectable humoral or mucosal immune responses to urease. Expression of a stable immunogenic protein in an appropriately attenuated S. typhi vector did not engender detectable mucosal or systemic antibody responses; additional work will be needed to define variables important for immunogenicity of heterologous antigens carried by live S. typhi vectors in humans.

Pilot Study of phoP/phoQ-Deleted Salmonella enterica Serovar Typhimurium Expressing Helicobacter pylori Urease in Adult Volunteers

ABSTRACT Attenuated Salmonella enterica serovar Typhi has been studied as an oral vaccine vector. Despite success with attenuatedS. enterica serovar Typhimurium vectors in animals, early clinical trials of S. enterica serovar Typhi expressing heterologous antigens have shown that few subjects have detectable immune responses to vectored antigens. A previous clinical study ofphoP/phoQ-deleted S. enterica serovar Typhi expressing Helicobacter pylori urease from a multicopy plasmid showed that none of eight subjects had detectable immune responses to the vectored antigen. In an attempt to further define the variables important for engendering immune responses to vectored antigens in humans, six volunteers were inoculated with 5 × 107 to 8 × 107 CFU ofphoP/phoQ-deleted S. enterica serovar Typhimurium expressing the same antigen. Two of the six volunteers had fever; none had diarrhea, bacteremia, or other serious side effects. The volunteers were more durably colonized than in previous studies ofphoP/phoQ-deleted S. enterica serovar Typhi. Five of the six volunteers seroconverted to S. entericaserovar Typhimurium antigens and had strong evidence of anti-Salmonella mucosal immune responses by enzyme-linked immunospot studies. Three of six (three of five who seroconverted toSalmonella) had immune responses in the most sensitive assay of urease-specific immunoglobulin production by blood mononuclear cells in vitro. One of these had a fourfold or greater increase in end-point immunoglobulin titer in serum versus urease. AttenuatedS. enterica serovar Typhimurium appears to be more effective than S. enterica serovar Typhi for engendering immune responses to urease. Data suggest that this may be related to a greater stability of antigen-expressing plasmid in S. enterica serovar Typhimurium and/or prolonged intestinal colonization. Specific factors unique to nontyphoidal salmonellae may also be important for stimulation of the gastrointestinal immune system.

Safety and Shedding of an Attenuated Strain of Listeria monocytogenes with a Deletion of actA/plcB in Adult Volunteers: a Dose Escalation Study of Oral Inoculation

ABSTRACT Listeria monocytogenes is an intracellular bacterial pathogen which causes bacteremia and has a tropism for the central nervous system and a propensity to cause maternofetal infection. L. monocytogenes has been shown to be an effective prophylactic and a therapeutic vaccine vector for viral and tumor antigens in animal models. L. monocytogenes mutants lacking the ActA protein, which is essential for intracellular movement, are attenuated but retain immunogenicity in mice. Given the pathogenic potential of L. monocytogenes, we created an attenuated mutant strain bearing double deletions in the actA and plcB virulence genes for an initial clinical safety study of a prototype L. monocytogenes vector in adults. Twenty healthy volunteers received single escalating oral doses (106 to 109 CFU, 4 volunteers per dose cohort) of this attenuated L. monocytogenes, designated LH1169. Volunteers were monitored in the hospital for 14 days with frequent clinical checks and daily blood and stool cultures, and they were monitored for six additional weeks as outpatients. There were no positive blood cultures and no fevers attributable to the investigational inoculation. Most volunteers shed vaccine bacteria for 4 days or less, without diarrhea. One volunteer had a late positive stool culture during outpatient follow-up. Three volunteers had abnormal liver function test results temporally associated with inoculation; one could be reasonably attributed to another cause. In the highest-dose cohort, humoral, mucosal, and cellular immune responses to the investigational organism were detected in individual volunteers. Attenuated L. monocytogenes can be studied in adult volunteers without serious long-term health sequelae.

Evaluation of a phoP/phoQ-deleted, aroA-deleted live oral Salmonella typhi vaccine strain in human volunteers

Improved live oral typhoid fever vaccines may be engineered by deletion of Salmonella-specific virulence genes in Salmonella typhi. Ty445, an aroA-deleted S. typhi Ty2 strain also deleted for the phoP/phoQ Salmonella typhimurium virulence regulatory locus, was tested in human volunteers. Volunteers received escalating single doses of the vaccine; subsequently 14 individuals received two doses of 10(10) c.f.u. without significant side-effects. Control vaccinees received four doses of the live oral typhoid vaccine Ty21a. Of controls, 5/8 seroconverted as measured by increases in serum IgG directed against S. typhi O antigen or whole bacterial antigens in ELISAs. Only 2/14 volunteers receiving the experimental vaccine Ty445 seroconverted. Although a delta aroA delta phoP/phoQ S. typhi strain is overattenuated for use as a typhoid fever vaccine, our data demonstrate that the deletion of the phoP/phoQ locus in S. typhi significantly attenuates this human pathogen.

Enteric Pathogens as Vaccine Vectors for Foreign Antigen Delivery

Live attenuated bacteria are attractive vaccine vectors that can elicit host immune responses to foreign antigens. Bacterial vectors may mimic natural infection and therefore interact with the mucosal, humoral, and cellular compartments of the immune system. A plethora of foreign (heterologous) antigens derived from bacterial, fungal, viral, or parasitic organisms have been expressed within bacterial vectors. Delivery of contraceptive and tumor antigens, cytokines, and adjuvants has also been explored. The result is a type of “vaccine factory” (29) in which the bacterial vector produces a foreign protein. Since bacterial vectors replicate within the host, it is hoped that they provide sustained exposure to the antigen, potentially augmenting the type and level of immune response. In addition, bacteria naturally possess immunostimulatory molecules such as lipopolysaccharide (LPS) and flagella that can stimulate immune responses (56). Internationally, there are three live bacterial vaccines commercially available and in clinical use: Salmonella enterica serovar Typhi Ty21a, Vibrio cholerae CVD 103-HgR, and Mycobacterium bovis BCG. These strains plus many other attenuated strains have been used as vectors to express heterologous antigens. Live bacterial vector vaccines have been evaluated in numerous animal and human studies, but there are currently no licensed live bacterial vector vaccines being used clinically. The most compelling rationales for the development of live bacterial vectors are the possibility of oral delivery and protection at mucosal surfaces. This review will cover attenuated bacterial enteric pathogens used as vectors to express foreign (heterologous) antigens, with emphasis on those that have reached clinical study, including Salmonella, Shigella, V. cholerae, and Listeria. This review will not cover bacterial vectors used to deliver DNA vaccines or subunit and conjugate vaccines.

Regulation of host immune responses by modification of Salmonella virulence genes

Modifying bacterial virulence genes to probe the nature of host immunity is mostly unexplored. Here we investigate whether host immune responses can be regulated by modification of bacterial virulence genes. In mice, attenuated Salmonella mutant strains with clinical relevance elicited differential host immune responses. Oral administration of a mutant strain with a PhoP-null phenotype promoted potent innate immune responses of macrophages that were sufficient for host defense. In contrast, administration of an Aro– mutant strain elicited stronger specific antibody and T-helper (Th)-cell responses, wherein Th1-type cells were required for clearance. Thus, genetic manipulation of bacteria may be used to broadly alter immune mechanisms that regulate attenuation within the host and to tailor host immunity to specific bacterial pathogens.