The nature of the establishment barrier for Trypanosoma brucei in the gut of Glossina pallidipes

The low survival rate of Trypanosoma brucei in tsetse flies is interpreted as in part at least the result of an establishment barrier. This barrier appears to be less active in young flies than in older flies. The growth rate of the peritrophic membrane is 1 mm./hour during the first 30 hours after emergence, and also after feeding.The distribution of the blood meal in relation to the growth of the peritrophic membrane makes it appear unlikely that the membrane itself is the barrier mechanism. A postulated adjustment period for trypanosomes in the crop of young flies (with an incomplete peritrophic membrane) is supported by cytochemical evidence concerning an enzymic transformation within 1 hour of feeding. This phenomenon implies a double transformation for successful host transfer: one (well established) in the vertebrate host sometime before transfer, a second (new) in the fly, immediately after transfer.The destruction of non-transformed trypanosomes in the mid-gut (after leaving the crop) of mature tsetse flies is considered to be the main establishment barrier.     

PSC-IBD: a unique form of inflammatory bowel disease associated with primary sclerosing cholangitis

BACKGROUND: Inflammatory bowel disease associated with primary sclerosing cholangitis (PSC-IBD) may have a high prevalence of rectal sparing, backwash ileitis, and colorectal neoplasia. AIMS: To describe the clinical features and outcomes of PSC-IBD and compare these to a group of chronic ulcerative colitis (CUC) patients. METHODS: The medical records of all patients with PSC-IBD evaluated at the Mayo Clinic Rochester between 1987 and 1992 were abstracted for information on endoscopic and histological features, colorectal neoplasia, surgery, and other clinical outcomes. Patients referred for colorectal neoplasia and those who did not undergo colonoscopy with biopsies were excluded. A control group of CUC patients matched for sex, duration of IBD at first clinic visit, and calendar year of first clinic visit was identified, and similar information was abstracted. RESULTS: Seventy one PSC-IBD patients and 142 CUC patients without PSC were identified. Rectal sparing and backwash ileitis were more common in the PSC-IBD group (52% and 51%, respectively) than in controls (6% and 7%, respectively). Overall, colorectal neoplasia developed in 18 cases and 15 controls, including 11 cancers (seven cases and four controls). An increased risk of colorectal neoplasia or death was not detected in a matched analysis. Although the cumulative incidence of colorectal neoplasia was higher in cases (33%) than in controls (13%) at five years, this was of borderline statistical significance (p=0.054, unmatched log rank test). Overall survival from first clinic visit was significantly worse among cases (79% v 97%) at five years (p<0.001, unmatched log rank test). CONCLUSION: PSC-IBD is frequently characterised by rectal sparing and backwash ileitis. Colorectal neoplasia develops in a substantial fraction and overall survival is worse. PSC-IBD may represent a distinct IBD phenotype.     

Virus-like particle-induced protection against MRSA pneumonia is dependent on IL-13 and enhancement of phagocyte function

The importance of the priming of the lung environment by past infections is being increasingly recognized. Exposure to any given antigen can either improve or worsen the outcome of subsequent lung infections, depending on the immunological history of the host. Thus, an ability to impart transient alterations in the lung environment in anticipation of future insult could provide an important novel therapy for emerging infectious diseases. In this study, we show that nasal administration of virus-like particles (VLPs) before, or immediately after, lethal challenge with methicillin-resistant Staphylococcus aureus (MRSA) of mice i) ensures complete recovery from lung infection and near absolute clearance of bacteria within 12 hours of challenge, ii) reduces host response-induced lung tissue damage, iii) promotes recruitment and efficient bacterial clearance by neutrophils and CD11c(+) cells, and iv) protects macrophages from MRSA-induced necrosis. VLP-mediated protection against MRSA relied on innate immunity. Complete recovery occurred in VLP-dosed mice with severe combined immunodeficiency, but not in wild-type mice depleted of either Ly6G(+) or CD11c(+) cells. Early IL-13 production associated with VLP-induced CD11c(+) cells was essential for VLP-induced protection. These results indicate that VLP-induced alteration of the lung environment protects the host from lethal MRSA pneumonia by enhancing phagocyte recruitment and killing and by reducing inflammation-induced tissue damage via IL-13-dependent mechanisms.     

Surgical Approach and Oncologic Outcomes Following Multidisciplinary Management of Retrorectal Sarcomas

Background

Retrorectal sarcomas are rare, and limited data are available on oncologic outcomes following surgery. Our aim was to evaluate outcomes in this patient population at our institution.

Materials and Methods

All patients who underwent surgical resection of a malignant retrorectal/presacral sarcoma between 1985 and 2005 were identified. Data analyzed included demographics, histopathologic diagnosis, surgical morbidity and mortality, use of adjuvant therapy, local and distant recurrence, and survival.

Results

A total of 37 patients were identified (20 males) with a median age of 49 years (range, 22–81 years). The most common histopathologic diagnosis was malignant peripheral nerve sheath tumor (n = 8). Also, 22 tumors were high grade and 15 were low grade. Surgical margin status was R0 in 31 patients and R1 in 6. Adjuvant therapy was given to 26 patients. Postoperative morbidity and mortality was 57% and 3%, respectively. Median length of follow-up in 16 patients alive at last contact was 4.7 years. The 5-year survival free of local (LDFS), distant (DDFS), and local or distant recurrence (DFS) was 51, 58, and 39%, respectively. Patient survival at 2, 5, and 10 years was 75, 55, and 47%, respectively. Disease-free survival was not significantly associated with gender (P = .16), primary vs secondary (P = .94), R0 vs R1 resection (P = .26), low vs high tumor grade (P = .17), or the use of surgery with or without adjuvant therapy (P = .33).

Conclusions

Retrorectal sarcomas are often high grade and locally advanced. Most tumors are resectable with free margins, and long-term survival may be possible in up to one-half of patients following an aggressive surgical approach.     

Comparison of Traditional Phenotypic Identification Methods with Partial 5′ 16S rRNA Gene Sequencing for Species-Level Identification of Nonfermenting Gram-Negative Bacilli

Correct identification of nonfermenting Gram-negative bacilli (NFB) is crucial for patient management. We compared phenotypic identifications of 96 clinical NFB isolates with identifications obtained by 5′ 16S rRNA gene sequencing. Sequencing identified 88 isolates (91.7%) with >99% similarity to a sequence from the assigned species; 61.5% of sequencing results were concordant with phenotypic results, indicating the usability of sequencing to identify NFB.Nonfermenting Gram-negative bacilli (NFB) are ubiquitous in the environment and may cause opportunistic infections in immunocompromised patients and individuals with cystic fibrosis (2, 9). Accurate diagnosis and appropriate treatment require species-specific identification of clinically significant NFB isolates. Conventional phenotypic identification may involve a number of methods, including observation of growth and colony morphology on various media, analysis of manual biochemical reactions, and the use of automated and nonautomated commercially available biochemical panels. Unfortunately, commercial phenotypic databases are often outdated and lack current taxonomy (15). Moreover, phenotypic systems often cannot account for the variable characteristics observed among members of the same species, resulting in poor precision upon repeat testing (3).Identification of NFB by partial 5′ 16S rRNA gene sequencing using the MicroSeq 500 system (Applied BioSystems, Foster City, CA) is more accurate than conventional phenotypic methods and other commercial systems involving fatty acid and carbon utilization profiles (16). As for any identification method, limitations for 16S rRNA gene sequencing exist (11). Bacterial taxonomy and nomenclature continue to change as the genotypic features of organisms are analyzed in greater detail. Furthermore, these analyses have identified unique strains with distinct biochemical and genetic profiles that make definitive identification difficult until the strains are accepted as new species (8, 17). Even with a relatively complete sequence database, 16S rRNA gene sequences from different strains are often identical or closely matched (i.e., >99.5% similar), making expert judgment a requirement for identification (11).When 16S rRNA gene sequencing is used to identify bacteria, the availability and completeness of databases will affect the accuracy of identification. Previous studies have shown that the MicroSeq 500 16S rRNA gene sequence library is incomplete and outdated for the identification of clinical isolates of Mycobacterium species (4) and Nocardia species (5, 14). As sequencing technology has become more affordable (6), clinical laboratories are now utilizing sequencing methods in conjunction with freely accessible public databases for organism identification. GenBank (http://blast.ncbi.nlm.nih.gov/Blast.cgi) is one such database that has been evaluated and found to contain sequence errors, especially in sequences submitted prior to 1995 (10, 11). The use of commercial databases increases the cost of sequence-based identification, and these databases are often outdated (4, 14). Finally, no criteria for reporting sequence identities exist, likely due to high levels of phylogenetic variation among species (11).In the present study, implementation of 5′ 16S rRNA gene sequencing using the first 500 to 527 bp for the identification of clinical NFB isolates was assessed. PCR and sequencing methods were performed as described previously (13, 14). Sequence similarity analysis was accomplished using the MicroSeq 500 library (version 500-0125) in conjunction with a new sequence library used previously to assess NFB identification by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) (13). Identifications of 96 clinical isolates by sequencing were compared to identifications established by conventional phenotypic and commercial methods (using the Vitek or API 20NE system [bioMérieux, Durham, NC] or the MicroScan sysem [Siemens Healthcare Diagnostics Inc., Newark, DE]) with the latest version of software available at the time of testing. Isolates were recovered from clinician-requested specimens from patients with suspected infection at four different institutions. Each of the institutions performed phenotypic identifications according to their protocols, which were not necessarily the same among the institutions. While this approach presented a potential limitation for the study, all institutions regularly participated in proficiency surveys and were accredited according to the Clinical Laboratory Improvement Amendments (CLIA). Reporting criteria for identifications based on similarity of sequences were established as follows: excellent species identification, 99.8 to 100% similarity to a database sequence from the assigned species; good species identification, 99.1 to 99.7% similarity; and unlikely species identification, 96.7 to 99.0% similarity. These criteria are consistent with the recommendations reported by Janda and Abbott (11). Of the 96 clinical isolates examined, 64 (66.7%) yielded excellent species identification, 24 (25.0%) yielded good identification, and 8 (8.3%) could be identified confidently only to the genus level by sequencing (Table ​(Table1).1). Fifteen isolates with discrepant identifications by sequencing and phenotypic methods exhibited sequence identity scores between 99.8 and 100%, in support of the sequencing results (Table ​(Table11).

TABLE 1.

Phenotypic identifications of NFB isolated from clinical samples compared with identifications obtained using partial 16S rRNA gene sequencing

Persistence and responsiveness of immunologic memory in the absence of secondary lymphoid organs

Secondary lymphoid organs (SLOs) promote primary immune responses by recruiting naive lymphocytes and activated APCs. However, their role in the persistence or responsiveness of memory lymphocytes is unclear. We tested whether memory cells were maintained and could respond to challenge in the absence of SLOs. We found that influenza-specific CD8 cells in the lung acquired a memory phenotype, underwent homeostatic proliferation, recirculated through nonlymphoid tissues, and responded to and cleared a challenge infection in the complete absence of SLOs. Similarly, influenza-specific virus-neutralizing antibody was generated and maintained in the absence of SLOs. Inducible bronchus-associated lymphoid tissue (iBALT) was also formed in the lungs of previously infected mice and may provide a niche for the maintenance of memory cells at the local level. These data show that SLOs are dispensable for the maintenance of immunologic memory and directly demonstrate the utility of local tissues, such as iBALT, in secondary immune responses.