A glycosylation mutant of Trypanosoma brucei links social motility defects in vitro to impaired colonisation of tsetse in vivo

Transmission of African trypanosomes by tsetse flies requires that the parasites migrate out of the midgut lumen and colonise the ectoperitrophic space. Early procyclic culture forms correspond to trypanosomes in the lumen; on agarose plates they exhibit social motility, migrating en masse as radial projections from an inoculation site. We show that an Rft1-/- mutant needs to reach a greater threshold number before migration begins, and that it forms fewer projections than its wild-type parent. The mutant is also up to 4 times less efficient at establishing midgut infections. Ectopic expression of Rft1 rescues social motility defects and restores the ability to colonise the fly. These results are consistent with social motility reflecting movement to the ectoperitrophic space, implicate N-glycans in the signalling cascades for migration in vivo and in vitro, and provide the first evidence that parasite-parasite interactions determine the success of transmission by the insect host.

Longitudinal study on the colonisation and transmission of methicillin-resistant Staphylococcus aureus in pig farms.

Knowledge about the dynamics of methicillin-resistant Staphylococcus aureus (MRSA) in pigs lacks detail at the level of individual animal. The aim of our study was therefore to determine the colonisation status of MRSA in individual pigs from birth to slaughter in order to gain a better understanding of substantial factors involved in transmission. Two farrow-to-finish and two grow-to-finish herds were included in the study. A total of 1728 nasal swabs from 390 pigs and 592 environmental wipes were collected at 11 different time points. Intermittent colonisation throughout the entire production cycle was conspicuous in the tracking of MRSA in individual pigs. Almost all pigs from a MRSA-positive herd changed MRSA status several times, which implies that pigs are transiently rather than permanently colonised. We highly recommend the definition of MRSA status at herd level rather that at the level of the individual pig when considering prevention measures against MRSA. Therefore, to avoid the further spread of MRSA in countries with moderate prevalence, such as in Switzerland, defining farms as MRSA positive or MRSA negative and allowing the trade of pigs only within herds of the same status seems feasible. This will also be important for combating the further dissemination of livestock-associated (LA)-MRSA into healthcare facilities and the community via humans who have close contact with animals.

Quantitative PCR to diagnose Pneumocystis pneumonia in immunocompromised non-HIV patients

The utility of quantitative Pneumocystis jirovecii PCR in clinical routine for diagnosing Pneumocystis pneumonia (PCP) in immunocompromised non-HIV patients is unknown. We analysed bronchoalveolar lavage fluid with real-time quantitative P. jirovecii PCR in 71 cases with definitive PCP defined by positive immunofluorescence (IF) tests and in 171 randomly selected patients with acute lung disease. In those patients, possible PCP cases were identified by using a novel standardised PCP probability algorithm and chart review. PCR performance was compared with IF testing, clinical judgment and the PCP probability algorithm. Quantitative P. jirovecii PCR values >1,450 pathogens·mL(-1) had a positive predictive value of 98.0% (95% CI 89.6-100.0%) for diagnosing definitive PCP. PCR values of between 1 and 1,450 pathogens·mL(-1) were associated with both colonisation and infection; thus, a cut-off between the two conditions could not be identified and diagnosis of PCP in this setting relied on IF and clinical assessment. Clinical PCP could be ruled out in 99.3% of 153 patients with negative PCR results. Quantitative PCR is useful for diagnosing PCP and is complementary to IF. PCR values of >1,450 pathogens·mL(-1) allow reliable diagnosis, whereas negative PCR results virtually exclude PCP. Intermediate values require additional clinical assessment and IF testing. On the basis of our data and for economic and logistical limitations, we propose a clinical algorithm in which IF remains the preferred first test in most cases, followed by PCR in those patients with a negative IF and strong clinical suspicion for PCP.

Biofilm-related infections of cerebrospinal fluid shunts

Cerebrospinal fluid (CSF) shunts carry a high risk of complications. Infections represent a major cause of shunt failure. Diagnosis and therapy of such infections are complicated by the formation of bacterial biofilms attached to shunt surfaces. This study correlated the pathophysiology and clinical course of biofilm infections with microscopical findings on the respective shunts. Surface irregularities, an important risk-factor for shunt colonisation with bacteria, were found to increase over time because of silicone degradation. Scanning electron-microscopy (SEM) documented residual biological material (dead biofilm), which can further promote extant bacterial adhesion, on newly manufactured shunts. Clinical course and SEM both documented bacterial dissemination against CSF flow and the monodirectional valve. In all cases, biofilms grew on both the inner and outer surfaces of the shunts. Microscopy and conventional culture detected all bacterial shunt infections. Analyses of 16S rDNA sequences using conserved primers identified bacteria in only one of three cases, probably because of previous formalin fixation of the samples.

The prevalence of penicillin-non-susceptible Streptococcus pneumoniae among children aged < 5 years correlates with the biannual epidemic activity of respiratory syncytial virus

This study investigated whether the epidemiology of penicillin-non-susceptible pneumococci (PNSP) colonising small children correlated with the biannual epidemic activity of respiratory syncytial virus (RSV). Colonisation rates and the prevalence of PNSP among paediatric outpatients aged < 5 years was analysed between January 1998 and September 2003 using an established national surveillance network. Resistance trends were investigated using time-series analysis to assess the correlation with the biannual pattern of RSV infections and national sales of oral paediatric formulations of antibiotics and antibiotic prescriptions to children aged < 5 years for acute respiratory tract infections. PNSP rates exhibited a biannual cycle in phase with the biannual seasonal RSV epidemics (p < 0.05). Resistance rates were higher during the winter seasons of 1998-1999 (20.1%), 2000-2001 (16.0%) and 2002-2003 (19.1%), compared with the winter seasons of 1997-1998 (8.2%), 1999-2000 (11.6%) and 2001-2002 (9.5%). Antibiotic sales and prescriptions showed regular peaks during each winter, with no significant correlation with the biannual pattern of RSV activity and seasonal trends of PNSP. RSV is an important determinant of the spread of PNSP and must be considered in strategies aimed at antimicrobial resistance control.

Nitazoxanide, a broad-spectrum thiazolide anti-infective agent for the treatment of gastrointestinal infections

Colonisation of the gastrointestinal tract by anaerobic bacteria, protozoa, trematodes, cestodes and/or nematodes and other infectious pathogens, including viruses, represents a major cause of morbidity and mortality in Africa, South America and southeast Asia, as well as other parts of the world. Nitazoxanide is a member of the thiazolide class of drugs with a documented broad spectrum of activity against parasites and anaerobic bacteria. Moreover, the drug has recently been reported to have a profound activity against hepatitis C virus infection. In addition, nitazoxanide exhibits anti-inflammatory properties, which have prompted clinical investigations for its use in Crohn's disease. Studies with nitazoxanide derivatives have determined that there must be significantly different mechanisms of action acting on intracellular versus extracellular pathogens. An impressive number of clinical studies have shown that the drug has an excellent bioavailability in the gastrointestinal tract, is fast acting and highly effective against gastrointestinal bacteria, protozoa and helminthes. A recent Phase II study has demonstrated viral response (hepatitis C) to monotherapy, with a low toxicity and an excellent safety profile over 24 weeks of treatment. Pre-clinical studies have indicated that there is a potential for application of this drug against other diseases, not primarily affecting the liver or the gastrointestinal tract.