Phenotypic and genotypic antimicrobial resistance of Listeria spp. in Spain

Listeriosis is a zoonotic disease caused by Listeria monocytogenes and Listeria ivanovii. The genus Listeria currently includes 27 recognized species and is found throughout the environment. The number of systematic studies on antimicrobial resistance in L. monocytogenes isolates from domestic farms using antimicrobial substances is limited. Importantly, dairy ruminant farms are reservoir of hypervirulent lineage I L. monocytogenes isolates, previously associated with human clinical cases. Considering that the classes of antibiotics used in food-producing domestic animals are frequently the same or closely related to those used in human medicine, studies about the impact of antibiotic use on the acquisition of antibiotic resistance in Listeria spp. in domestic animal farms are, therefore, of high importance. Here, susceptibility to 25 antibiotics was determined. Eighty-one animal-related, 35 food and 21 human pathogenic Listeria spp. isolates and 114 animal-related non-pathogenic Listeria spp. isolates were tested. Whole genome sequencing data was used for molecular characterization. Regarding L. monocytogenes, 2 strains from the clinical-associated linage I showed resistance to erythromycin, both related to dairy ruminants. Acquired resistance to one antibiotic was exhibited in 1.5% of L. monocytogenes isolates compared with 14% of non-pathogenic Listeria spp. isolates. Resistance to tetracycline (7.9%), doxycycline (7.9%), penicillin (4.4%), and ampicillin (4.4%) were the most frequently observed in non-pathogenic Listeria spp. While resistance to two or more antibiotics (5.6%) was most common in Listeria spp., isolates, resistance to one antibiotic was also observed (1.6%). The present results show that non-pathogenic Listeria spp. harbour antimicrobial resistance genes.

Kinetic and proteomic studies in milk show distinct patterns among major Listeria monocytogenes clones

Listeria monocytogenes, a contaminant of raw milk, includes hypervirulent clonal complexes (CC) like CC1, CC4, and CC6, highly overrepresented in dairy products when compared to other food types. Whether their higher prevalence in dairy products is the consequence of a growth advantage in this food remains unknown. We examined growth kinetics of five L. monocytogenes isolates (CC1, CC4, CC6, CC9, and CC121) at 37 and 4 °C in ultra-high temperature (UHT) milk and raw milk. At 4 °C, hypovirulent CC9 and CC121 isolates exhibit better growth parameters in UHT milk compared to the hypervirulent CC1, CC4, and CC6 isolates. CC9 isolate in raw milk at 4 °C exhibited the fastest growth and the highest final concentrations. In contrast, hypervirulent isolates (CC1, CC4, and CC6) displayed better growth rates in UHT milk at 37 °C, the mammalian host temperature. Proteomic analysis of representative hyper- (CC1) and hypovirulent (CC9) isolates showed that they respond to milk cues differently with CC-specific traits. Proteins related to metabolism (such as LysA or different phosphotransferase systems), and stress response were upregulated in both isolates during growth in UHT milk. Our results show that there is a Listeria CC-specific and a Listeria CC-common response to the milk environment. These findings shed light on the overrepresentation of hypervirulent L. monocytogenes isolates in dairy products, suggesting that CC1 and CC4 overrepresentation in dairy products made of raw milk may arise from contamination during or after milking at the farm and discard an advantage of hypervirulent isolates in milk products when stored at refrigeration temperatures.

Description of the vaginal microbiota in nulliparous ewes during natural mating and pregnancy: preliminary signs of the male preputial microbiota modulation

The vaginal microbiota plays a key role in animals' health. Understanding its diversity and composition and associated changes occurring through the reproductive cycle represents valuable knowledge to disclose the mechanisms leading to dysbiosis and eventually to infection. Even if the human vaginal microbiota has been thoroughly studied, scarce research has been conducted on the vaginal microbiota of livestock. In this study, 16S rRNA gene-based sequencing was performed on vaginal samples of ten nulliparous ewes at three different sampling points: before the estrus synchronization protocol (T0), at the time of estrus before mating (Testrus), and the day of the pregnancy diagnosis (Tpreg). Preputial samples from the three males collected pre and post-mating were also analyzed. Firmicutes, Proteobacteria, Bacteroidetes, and Actinobacteria were the most abundant phyla in vaginal samples. The most abundant genera were Porphyromonas, Anaerococcus, and Peptinophilius. Vaginal microbiota biodiversity decreased during pregnancy. Tenericutes (Ureaplasma spp.) increased significantly at Tpreg in both pregnant and non-pregnant ewes. Differences were observed between pregnant and non-pregnant ewes at Tpreg where pregnant ewes had a significantly higher abundance of Actinobacillus spp. and Ureaplasma spp. Ewes that were diagnosed with pregnancy at Tpreg showed a decreased abundance of gram-negative bacteria such as Bacteroidales, Campylobacterales, and Enterobacteriales. In addition, a significant decrease in the relative abundances of genera within Firmicutes, such as Alloicoccus (Lactobacillales), Atopostipes (Lactobacillales), and an uncultured bacteria W5053 from Family XI (Firmicutes, Clostridiales) was observed in non-pregnant ewes at Tpreg. The four most abundant phyla in the rams' prepuce were the same as in the ewes' vagina. The most abundant genus was Corynebacterium. No major differences were observed in the ram's preputial microbiota between pre and post-mating samples. Nevertheless, the differences in the taxonomic composition of ewes' vaginal microbiota between Testrus and Tpreg could be explained by the exposure to the preputial microbiota. This study offers new insights into the effects of several key steps of the ewe's reproductive cycle such as estrus-synchronization protocol, mating, and pregnancy on ovine vaginal microbiota. The knowledge of the microbiota dynamics during the reproductive cycle can help improve the reproductive outcomes of dams by identifying biomarkers and putative probiotics.

Clinical and genomic features of Listeria monocytogenes-associated mesenteric lymphadenitis in a cat

BACKGROUND

Listeriosis is a severe foodborne infection caused by Listeria monocytogenes, an important foodborne pathogen of animals and humans. Listeriosis is a rare disease in cats.

OBJECTIVE

To describe the clinical, diagnostic imaging, histological, and microbiological features of L. monocytogenes-associated mesenteric lymphadenitis in a cat.

ANIMALS

Listeria monocytogenes-associated mesenteric lymphadenitis was confirmed in a cat by histology and microbiology.

RESULTS

Two distinct isolates of L. monocytogenes were cultured from the affected mesenteric lymph node and whole genome sequencing was performed.

CONCLUSION AND CLINICAL IMPORTANCE

This report should alert veterinary clinicians and microbiologists to the syndrome, which may have implications for health and food safety in animals and humans.

Genomic characterization of Listeria spp. isolated from tonsils, udder and feces of domestic dairy ruminants in Spain

Two species of Listeria are pathogenic, Listeria monocytogenes and Listeria ivanovii. Although studies have shown that dairy ruminants shed Listeria spp. in feces, there is little information about ruminants that do not shed Listeria spp. in their feces but asymptomatically carry them in organs. We evidence that ruminants can asymptomatically carry L. ivanovii in udders and L. monocytogenes and L. ivanovii in tonsils without fecal shedding. Whole-genome sequence of L. monocytogenes and L. ivanovii contained known core genes involved in virulence and antibiotic resistance. This work highlights tonsils and udders as a Listeria intra-host site of colonization.

Search of antimicrobial lactic acid bacteria from Salmonella-negative dogs

Background

Salmonellosis is one of the most important food-borne zoonotic disease affecting both animals and humans. The objective of the present study was to identify gastrointestinal (GI) lactic acid bacteria (LAB) of canine-origin from Salmonella-negative dogs’ faeces able to inhibit monophasic Salmonella Typhimurium previously isolated from dogs’ faeces, in order to be used as a potential probiotic in pet nutrition.

Results

Accordingly, 37 LAB were isolated from Salmonella-negative dogs’ faeces and tested against monophasic S. Typhimurium using the spot on lawn method out of which 7 strains showed an inhibition halo higher than 2.5 cm. These 7 strains were also tested with the co-culture method and one showed the greatest inhibition value (p < 0.05). Subsequently, the isolate was identified through 16S rRNA sequencing and sequence homology and designated as Ligilactobacillus salivarius (L. salivarius). LAB from Salmonella-positive dogs were also identified and none was the selected strain. Finally, to identify the mechanism of inhibition of L. salivarius, the supernatant was analyzed, and a dose response effect was observed.

Conclusions

It is concluded that the canine-origin L. salivarius, could possess some in vitro functional attributes of a candidate probiotic and could prevent monophasic S. Typhimurium colonization or inhibit its activity if the infection occurs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-021-03070-x.

Ruminant-associated Listeria monocytogenes isolates belong preferentially to dairy-associated hypervirulent clones: a longitudinal study in 19 farms

Studies have shown that ruminants constitute reservoirs of Listeria monocytogenes, but little is known about the epidemiology and genetic diversity of this pathogen within farms. Here we conducted a large-scale longitudinal study to monitor Listeria spp. in 19 dairy farms during three consecutive seasons (N = 3251 samples). L. innocua was the most prevalent species, followed by L. monocytogenes. Listeria monocytogenes was detected in 52.6% of farms and more frequently in cattle (4.1%) and sheep (4.5%) than in goat farms (0.2%). Lineage I accounted for 69% of L. monocytogenes isolates. Among animal samples, the most prevalent sublineages (SL) and clonal complexes (CC) were SL1/CC1, SL219/CC4, SL26/CC26 and SL87/CC87, whereas SL666/CC666 was most prevalent in environmental samples. Sixty-one different L. monocytogenes cgMLST types were found, 28% common to different animals and/or surfaces within the same farm and 21% previously reported elsewhere in the context of food and human surveillance. Listeria monocytogenes prevalence was not affected by farm hygiene but by season: higher prevalence was observed during winter in cattle, and during winter and spring in sheep farms. Cows in their second lactation had a higher probability of L. monocytogenes faecal shedding. This study highlights dairy farms as a reservoir for hypervirulent L. monocytogenes.

Pathogenicity and virulence of Listeria monocytogenes: A trip from environmental to medical microbiology

Listeria monocytogenes is a saprophytic gram-positive bacterium, and an opportunistic foodborne pathogen that can produce listeriosis in humans and animals. It has evolved an exceptional ability to adapt to stress conditions encountered in different environments, resulting in a ubiquitous distribution. Because some food preservation methods and disinfection protocols in food-processing environments cannot efficiently prevent contaminations, L. monocytogenes constitutes a threat to human health and a challenge to food safety. In the host, Listeria colonizes the gastrointestinal tract, crosses the intestinal barrier, and disseminates through the blood to target organs. In immunocompromised individuals, the elderly, and pregnant women, the pathogen can cross the blood-brain and placental barriers, leading to neurolisteriosis and materno-fetal listeriosis. Molecular and cell biology studies of infection have proven L. monocytogenes to be a versatile pathogen that deploys unique strategies to invade different cell types, survive and move inside the eukaryotic host cell, and spread from cell to cell. Here, we present the multifaceted Listeria life cycle from a comprehensive perspective. We discuss genetic features of pathogenic Listeria species, analyze factors involved in food contamination, and review bacterial strategies to tolerate stresses encountered both during food processing and along the host's gastrointestinal tract. Then we dissect host-pathogen interactions underlying listerial pathogenesis in mammals from a cell biology and systemic point of view. Finally, we summarize the epidemiology, pathophysiology, and clinical features of listeriosis in humans and animals. This work aims to gather information from different fields crucial for a comprehensive understanding of the pathogenesis of L. monocytogenes.

Ruminant-associated Listeria monocytogenes isolates belong preferentially to dairy-associated hypervirulent clones: a longitudinal study in 19 farms

Studies have shown that ruminants constitute reservoirs of Listeria monocytogenes, but little is known about the epidemiology and genetic diversity of this pathogen within farms. Here we conducted a large-scale longitudinal study to monitor Listeria spp. in 19 dairy farms during three consecutive seasons (N = 3251 samples). L. innocua was the most prevalent species, followed by L. monocytogenes. Listeria monocytogenes was detected in 52.6% of farms and more frequently in cattle (4.1%) and sheep (4.5%) than in goat farms (0.2%). Lineage I accounted for 69% of L. monocytogenes isolates. Among animal samples, the most prevalent sublineages (SL) and clonal complexes (CC) were SL1/CC1, SL219/CC4, SL26/CC26 and SL87/CC87, whereas SL666/CC666 was most prevalent in environmental samples. Sixty-one different L. monocytogenes cgMLST types were found, 28% common to different animals and/or surfaces within the same farm and 21% previously reported elsewhere in the context of food and human surveillance. Listeria monocytogenes prevalence was not affected by farm hygiene but by season: higher prevalence was observed during winter in cattle, and during winter and spring in sheep farms. Cows in their second lactation had a higher probability of L. monocytogenes faecal shedding. This study highlights dairy farms as a reservoir for hypervirulent L. monocytogenes.

Listeria valentina sp. nov., isolated from a water trough and the faeces of healthy sheep

In the context of a study on the occurrence of Listeria species in an animal farm environment in Valencia, Spain, six Listeria-like isolates could not be assigned to any known species. Phylogenetic analysis based on the 16S rRNA gene and on 231 Listeria core genes grouped these isolates in a monophyletic clade within the genus Listeria, with highest similarity to Listeria thailandensis. Whole-genome sequence analyses based on in silico DNA-DNA hybridization, the average nucleotide blast and the pairwise amino acid identities against all currently known Listeria species confirmed that these isolates constituted a new taxon within the genus Listeria. Phenotypically, these isolates differed from other Listeria species mainly by the production of acid from inositol, the absence of acidification in presence of methyl α-d-glucoside, and the absence of α-mannosidase and nitrate reductase activities. The name Listeria valentina sp. nov. is proposed for this novel species, and the type strain is CLIP 2019/00642^T (=CIP 111799^T=DSM 110544^T).

Virulence potential of Listeria monocytogenes strains recovered from pigs in Spain

BACKGROUND

Listeria monocytogenes is a foodborne bacterial pathogen that causes listeriosis, an infectious disease in animals and people, with pigs acting as asymptomatic reservoirs. In August 2019 an outbreak associated with the consumption of pork meat caused 222 human cases of listeriosis in Spain. Determining the diversity as well as the virulence potential of strains from pigs is important to public health.

METHODS

The behaviour of 23 L monocytogenes strains recovered from pig tonsils, meat and skin was compared by studying (1) internalin A, internalin B, listeriolysin O, actin assembly-inducing protein and PrfA expression levels, and (2) their invasion and intracellular growth in eukaryotic cells.

RESULTS

Marked differences were found in the expression of the selected virulence factors and the invasion and intracellular replication phenotypes of L monocytogenes strains. Strains obtained from meat samples and belonging to serotype 1/2a did not have internalin A anchored to the peptidoglycan. Some strains expressed higher levels of the studied virulence factors and invaded and replicated intracellularly more efficiently than an epidemic L monocytogenes reference strain (F2365).

CONCLUSION

This study demonstrates the presence of virulent L monocytogenes strains with virulent potential in pigs, with valuable implications in veterinary medicine and food safety.

The addition of Lactobacillus spp. negatively affects Mycoplasma bovis viability in bovine cervical mucus

BACKGROUND

Mycoplasma bovis is an important pathogen for the cattle industry worldwide causing significant economic losses. Several transmission routes, including those related to reproduction, have been described. Indeed, the pathogen can colonize the female reproductive tract after artificial insemination (AI) with contaminated semen. Lactobacillus spp.-based probiotics have been used for vaginal dysbiosis treatment in women and cows although their role in controlling cervico-vaginal infections due to M. bovis is unknown. The objective of the present work is to assess the viability of M. bovis (PG45, NCTC 10131) in experimentally contaminated cervical mucus after the addition of Lactobacillus spp. at different concentrations as a competing agent and pH acidifier.

RESULTS

The addition of probiotic at a concentration higher than 10⁸ colony forming units (CFU/mL had a detrimental effect (P < 0.05) on mycoplasma viability in cervical mucus. This coincided with a significant LAB growth and an important decrease in pH from 8.4 to 5.6 (P < 0.05). However, after the addition of less concentrated probiotic, M. bovis survival was not affected and there was no significant LAB growth despite the drop of pH from 8.4 to 6.73 (P < 0.05).

CONCLUSION

The addition of concentrations higher than 10⁸ CFU/mL of Lactobacillus spp. negatively affects M. bovis viability in bovine cervical mucus under in vitro conditions. Although the effect observed on the pathogen viability seems to be related to the pH decrease after LAB proliferation in cervical mucus, further studies are necessary to elucidate if other factors are implicated. Nevertheless, the administration of Lactobacillus spp.-based probiotics might be used in the future to control M. bovis proliferation in the cervico-vaginal tract of cows.

Vaginal Microbiota Changes During Estrous Cycle in Dairy Heifers

The vaginal microbiota plays an important role in the health of dairy cattle, and it could be manipulated for the prevention and treatment of reproduction-related infections. The present study profiles and compares the vaginal microbiota of healthy dairy heifers during the estrous cycle focusing the results in follicular (estrus) and luteal (diestrus) phases using 16S rRNA sequencing of the V3–V4 hypervariable region. Twenty 13–16-months-old virgin dairy heifers from a single farm were included in this study. Vaginal swabs and blood samples were obtained during estrus (6–8 h before artificial insemination) and diestrus (14 days after insemination). Estrus was evaluated by an activity monitoring system and confirmed with plasma progesterone immunoassay. Results showed that the taxonomic composition of the vaginal microbiota was different during the follicular and luteal phases. At the phylum level, the most abundant bacterial phyla were Tenericutes, Firmicutes, and Bacteroidetes which comprised more than 75% of the vaginal microbiota composition. The next more abundant phyla, in order of decreasing abundance, were Proteobacteria, Actinobacteria, Fusobacteria, Epsilonbacteraeota, and Patescibacteria. Together with Tenericutes, Firmicutes, and Bacteroidetes represented more than 96% of the bacterial composition. Ureaplasma, Histophilus, f_Corynebacteriaceae, Porphyromonas, Mycoplasma, Ruminococcaceae UCG-005, were the most abundant genera or families. The results also showed that the vaginal microbiota of dairy heifers was non-lactobacillus dominant. The genus Lactobacillus was always found at a low relative abundance during the estrous cycle being more abundant in the follicular than in the luteal phase. Despite more research is needed to explore the potential use of native vaginal microbiota members as probiotics in dairy heifers, this study represents an important step forward. Understanding how the microbiota behaves in healthy heifers will help to identify vaginal dysbiosis related to disease.

A role for Taok2 in Listeria monocytogenes vacuolar escape

The bacterial pathogen Listeria monocytogenes invades host cells, ruptures the internalization vacuole, and reaches the cytosol for replication. A high-content small interfering RNA (siRNA) microscopy screen allowed us to identify epithelial cell factors involved in L. monocytogenes vacuolar rupture, including the serine/threonine kinase Taok2. Kinase activity inhibition using a specific drug validated a role for Taok2 in favoring L. monocytogenes cytoplasmic access. Furthermore, we showed that Taok2 recruitment to L. monocytogenes vacuoles requires the presence of pore-forming toxin listeriolysin O. Overall, our study identified the first set of host factors modulating L. monocytogenes vacuolar rupture and cytoplasmic access in epithelial cells.

Use of Probiotics in Intravaginal Sponges in Sheep: A Pilot Study

Simple Summary

The use of intravaginal devices may generate retention of vaginal secretions and abnormal discharges at device withdrawal, which may create changes in the normal vaginal bacterial microbiota. These changes in vaginal microbiota could allow the growth of opportunistic pathogenic bacteria which can require antibiotic treatment. The addition of antibiotics on sponges poses a risk of milk contamination. In dairy cows, it has been observed that the use of lactic acid bacteria (LAB) confers a health benefit to the reproductive tract against bacterial infections. However, LAB use in intravaginal sponges in sheep has not been reported. The aims of this study were to describe the dynamics of the ewes’s vaginal cultivable microbiota during a classic long-term estrous synchronization protocol and to develop a model of probiotic infusion in vaginal sponges in order to study their influence in ewe’s vaginal microbiota, general health status, fertility and prolificity. The present results suggest that LAB infusion in the ewe’s vagina do not affect general health status and did not reduce fertility during natural mating.

Abstract

Sheep estrous synchronization is mainly based on progestagen-impregnated sponges which could cause vaginitis. Several species of Lactobacillus used as probiotics are commonly used in the treatment or prevention of urogenital infections in humans. However, no studies have been performed to analyze the potential use of probiotics to prevent urogenital infections in sheep. A randomized controlled clinical trial was conducted with 21 one-year-old ewes to develop a model of probiotic infusion in vaginal sponges in order to study their influence in ewe’s vaginal microbiota, general health status, fertility and prolificity. Synchronization of estrus was based on intravaginal sponges for 14 days. Bacterial communities (Enterobacteriaceae and lactic acid bacteria) were highly fluctuating over time and between animals. The safety of probiotic infusion (mix of Lactobacillus spp. 60% L. crispatus, 20% L. brevis and 20% L. gasseri) in the vagina of healthy ewes was firstly confirmed. Neutrophils were observed in 80% (8/10) of the control ewes compared to 36% (4/11) of the ewes in the probiotic group 2 days after sponge removal (p = 0.056). Fertility in the control and probiotic groups was 60% (6/10) and 91% (10/11), respectively p = 0.097. These results suggest that Lactobacillus spp. infusion in the ewe’s vagina does not affect general health status or fertility.

Listeriolysin O-dependent host surfaceome remodeling modulates Listeria monocytogenes invasion

Listeria monocytogenes is a pathogenic bacterium that invades epithelial cells by activating host signaling cascades, which promote bacterial engulfment within a phagosome. The pore-forming toxin listeriolysin O (LLO), which is required for bacteria phagosomal escape, has also been associated with the activation of several signaling pathways when secreted by extracellular bacteria, including Ca2+ influx and promotion of L. monocytogenes entry. Quantitative host surfaceome analysis revealed significant quantitative remodeling of a defined set of cell surface glycoproteins upon LLO treatment, including a subset previously identified to play a role in the L. monocytogenes infection process. Our data further shows that the lysosomal-associated membrane proteins LAMP-1 and LAMP-2 are translocated to the cellular surface and those LLO-induced Ca2+ fluxes are required to trigger the surface relocalization of LAMP-1. Finally, we identify late endosomes/lysosomes as the major donor compartments of LAMP-1 upon LLO treatment and by perturbing their function, we suggest that these organelles participate in L. monocytogenes invasion.

Reassessing the role of internalin B in Listeria monocytogenes virulence using the epidemic strain F2365

OBJECTIVES

To investigate the contribution to virulence of the surface protein internalin B (InlB) in the Listeria monocytogenes lineage I strain F2365, which caused a deadly listeriosis outbreak in California in 1985.

METHODS

The F2365 strain displays a point mutation that hampers expression of InlB. We rescued the expression of InlB in the L. monocytogenes lineage I strain F2365 by introducing a point mutation in the codon 34 (TAA to CAA). We investigated its importance for bacterial virulence using in vitro cell infection systems and a murine intravenous infection model.

RESULTS

In HeLa and JEG-3 cells, the F2365 InlB⁺ strain expressing InlB was ≈9-fold and ≈1.5-fold more invasive than F2365, respectively. In livers and spleens of infected mice at 72 hours after infection, bacterial counts for F2365 InlB⁺ were significantly higher compared to the F2365 strain (≈1 log more), and histopathologic assessment showed that the F2365 strain displayed a reduced number of necrotic foci compared to the F2365 InlB⁺ strain (Mann-Whitney test).

CONCLUSIONS

InlB plays a critical role during infection of nonpregnant animals by a L. monocytogenes strain from lineage I. A spontaneous mutation in InlB could have prevented more severe human morbidity and mortality during the 1985 California listeriosis outbreak.

Attitude Toward Organ Donation and Transplantation in Veterinary Students: A Multicenter and Stratified Study in Spain

BACKGROUND

Veterinarians often hold decision-making positions in the public health care system and can therefore influence public opinion about organ donation and transplantation (ODT). The aim of this work was to analyze the attitude of Spanish veterinary students toward ODT, because they may influence public opinion in the future, and to determine the factors that condition it.

METHODS

This was a sociologic, interdisciplinary, multicenter, observational study in Spain. The study population was students studying for a veterinary degree in Spain (n = 9000), and a sample of 2815 students (confidence of 99% and precision of ±1%) was stratified by geographic area and academic year. A validated questionnaire of attitude toward ODT (PCID-DTO-Ríos) was self-administered and anonymous.

RESULTS

Of the 2815 selected students (2790 plus the 0.9% per type of sample), 2650 completed the questionnaire (response rate, 94.14%): 83% (n = 2207) of the respondents were in favor of donation and 17% against. The following main variables were related to a favorable attitude: being female (odds ratio [OR], 0.752; P = .034); knowing a donor (OR, 1.834; P = .003); having discussed the matter with one's family (OR, 1.587; P = .002); having spoken about the subject in social circles with friends (OR, 1.633; P < .001), and being in favor of donating a deceased family member's organs (OR, 2.403; P < .001).

CONCLUSIONS

Seventeen percent of Spanish veterinary students were not in favor of ODT. It is important to know the factors that determine their attitude, because this will make it possible to optimize the resources invested in campaigns to promote ODT and to take more specific action.

Regulating Bacterial Virulence with RNA

Noncoding RNAs (ncRNAs) regulating virulence have been identified in most pathogens. This review discusses RNA-mediated mechanisms exploited by bacterial pathogens to successfully infect and colonize their hosts. It discusses the most representative RNA-mediated regulatory mechanisms employed by two intracellular [Listeria monocytogenes and Salmonella enterica serovar Typhimurium (S. Typhimurium)] and two extracellular (Vibrio cholerae and Staphylococcus aureus) bacterial pathogens. We review the RNA-mediated regulators (e.g., thermosensors, riboswitches, cis- and trans-encoded RNAs) used for adaptation to the specific niches colonized by these bacteria (intestine, blood, or the intracellular environment, for example) in the framework of the specific pathophysiological aspects of the diseases caused by these microorganisms. A critical discussion of the newest findings in the field of bacterial ncRNAs shows how examples in model pathogens could pave the way for the discovery of new mechanisms in other medically important bacterial pathogens.

Veterinary Students' Attitude Toward Living Kidney Donation: A Multicenter Stratified Study From Spain

Living kidney related donations (LKRD) should be promoted because of the current deficit of organs for transplantation. The objective of the study was to analyze the attitude of Spanish veterinary students toward LKRD, because they may influence public opinion in the future, and to determine the factors that condition it.

METHODS

A sociological, interdisciplinary, multicenter, and observational study was carried out in the veterinary students enrolled in Spain (n = 9000) in the university academic year 2010-2011. A sample of 2815 students was stratified by geographical area and academic year. The students' attitude toward LKRD was assessed using a psychosocial validated questionnaire (PCID-DVR Rios), was self-administered, and was completed anonymously. Veterinary schools were randomly selected. The questionnaire was applied to each academic year at compulsory sessions. Statistical analysis was preformed using t test, χ² test, and logistic regression analysis.

RESULTS

The completion rate was 95% (n = 2683); 93% (n = 2504) were in favor of LKRD and 36% (n = 945) supported unrelated living kidney donation. The following variables were associated with having a more favorable attitude: (1) sex (P < .001), (2) being a student of southern universities (P = .03), (3) attitude toward deceased donation (P < .001), (4) having a father (P < .001) or a mother (P < .001) in favor of organ donation, and (5) having discussed the subject with friends (P = .03) or family (P = .02). However, only 60% would accept a kidney from a relative.

CONCLUSION

Spanish veterinary students have a favorable attitude toward LKRD. However, only 60% would accept a kidney from a relative.

Role in virulence of phospholipases, listeriolysin O and listeriolysin S from epidemic Listeria monocytogenes using the chicken embryo infection model

Most human listeriosis outbreaks are caused by Listeria monocytogenes evolutionary lineage I strains which possess four exotoxins: a phosphatidylinositol-specific phospholipase C (PlcA), a broad-range phospholipase C (PlcB), listeriolysin O (LLO) and listeriolysin S (LLS). The simultaneous contribution of these molecules to virulence has never been explored. Here, the importance of these four exotoxins of an epidemic lineage I L. monocytogenes strain (F2365) in virulence was assessed in chicken embryos infected in the allantoic cavity. We show that LLS does not play a role in virulence while LLO is required to infect and kill chicken embryos both in wild type transcriptional regulator of virulence PrfA (PrfA^WT) and constitutively active PrfA (PrfA*) backgrounds. We demonstrate that PlcA, a toxin previously considered as a minor virulence factor, played a major role in virulence in a PrfA* background. Interestingly, GFP transcriptional fusions show that the plcA promoter is less active than the hly promoter in vitro, explaining why the contribution of PlcA to virulence could be observed more importantly in a PrfA* background. Together, our results suggest that PlcA might play a more important role in the infectious lifecycle of L. monocytogenes than previously thought, explaining why all the strains of L. monocytogenes have conserved an intact copy of plcA in their genomes.

Listeriolysin S: A bacteriocin from epidemic Listeria monocytogenes strains that targets the gut microbiota

Listeria monocytogenes is a Gram-positive food-borne pathogen that in humans may traverse the intestinal, placental and blood/brain barriers, causing gastroenteritis, abortions and meningitis. Crossing of these barriers is dependent on the bacterial ability to enter host cells, and several L. monocytogenes surface and secreted virulence factors are known to facilitate entry and the intracellular lifecycle. The study of L. monocytogenes strains associated to human listeriosis epidemics has revealed the presence of novel virulence factors. One such factor is Listeriolysin S, a thiazole/oxazole modified microcin that displays bactericidal activity and modifies the host microbiota during infection. Our recent results therefore highlight the interaction of L. monocytogenes with gut microbes as a crucial step in epidemic listeriosis. In this article, we will discuss novel implications for this family of toxins in the pathogenesis of diverse medically relevant microorganisms.

Assessing Vacuolar Escape of Listeria Monocytogenes

Listeria monocytogenes is a bacterial pathogen which invades and multiplies within non-professional phagocytes. Signaling cascades involved in cellular entry have been extensively analyzed, but the events leading to vacuolar escape remain less clear. In this chapter, we detail a microscopy FRET-based assay which allows quantitatively measuring L. monocytogenes infection and escape from its internalization vacuole, as well as a correlative light/electron microscopy method to investigate the morphological features of the vacuolar compartments containing L. monocytogenes.

Listeria monocytogenes remodels the cell surface in the blood-stage

After crossing the intestinal barrier, the bacterial pathogen Listeria monocytogenes disseminates via the blood to the liver, spleen, brain and placenta. Transcriptomic studies have shown that L. monocytogenes changes expression of many genes during this blood-stage. However, no comparable data at the protein level are known. As main interactors with the environment, we focused in surface proteins produced by L. monocytogenes in an ex vivo bovine blood model. Bacteria exposed to blood alter selectively the amount of several surface proteins compared with bacteria grown in laboratory media. Increased levels were detected for Lmo0514 and Internalin A, two surface proteins covalently bound to peptidoglycan, and the moonlighting protein alcohol-acetaldehyde dehydrogenase, also known as Lap for 'Listeria adhesion protein'. Lmo0514, induced by L. monocytogenes inside epithelial cells, is required for survival in plasma and for virulence in mice at early infection stages. Lmo0514 is also important to cope with low pH stress. By contrast, L. monocytogenes down-regulates other surface proteins following exposure to blood and plasma such as Internalin I. These data provide evidence for remodelling of the L. monocytogenes cell surface during the blood-stage, which it could facilitate pathogen dissemination to deep organs.

Validation of a quantitative polymerase chain reaction method for human Alu gene detection in microchimeric pigs used as donors for xenotransplantation

This work was undertaken to evaluate whether a real-time quantitative polymerase chain reaction (qPCR) is as an adequate method for detection and quantification of human-specific DNA elements (Alu gene) in tissues and blood samples of pigs in which human stem cells were engrafted. Real-time qPCR quantification was performed with the use of previously described primers. The human DNA was mixed with different quantities of porcine DNA. The primer concentration and specificity, the qPCR efficiency, the quantification variations due to different porcine DNA concentrations, and the dissociation curve produced by the assay were evaluated. The qPCR proved to be specific, robust, with a reproducible and specific bimodal melting curve. High porcine DNA concentration produced subquantification, especially with low human DNA quantity. However, the assay proved to be useful for the detection of chimeric piglets produced by human cells injected in utero, because the effect caused by the porcine DNA interference was corrected in quantification of human DNA from piglets.

ISG15 counteracts Listeria monocytogenes infection

ISG15 is an interferon-stimulated, linear di-ubiquitin-like protein, with anti-viral activity. The role of ISG15 during bacterial infection remains elusive. We show that ISG15 expression in nonphagocytic cells is dramatically induced upon Listeria infection. Surprisingly this induction can be type I interferon independent and depends on the cytosolic surveillance pathway, which senses bacterial DNA and signals through STING, TBK1, IRF3 and IRF7. Most importantly, we observed that ISG15 expression restricts Listeria infection in vitro and in vivo. We made use of stable isotope labeling in tissue culture (SILAC) to identify ISGylated proteins that could be responsible for the protective effect. Strikingly, infection or overexpression of ISG15 leads to ISGylation of ER and Golgi proteins, which correlates with increased secretion of cytokines known to counteract infection. Together, our data reveal a previously uncharacterized ISG15-dependent restriction of Listeria infection, reinforcing the view that ISG15 is a key component of the innate immune response.

DOI:http://dx.doi.org/10.7554/eLife.06848.001

Listeria monocytogenes is a bacterium that can cause serious food poisoning in humans. Infections with this bacterium can be particularly dangerous to young children, pregnant women, the elderly, and individuals with weakened immune systems because they are more susceptible to developing serious complications that can sometimes lead to death.

The bacteria infect cells in the lining of the human gut. Cells that detect the bacteria respond by producing proteins called interferons and other signaling proteins that activate the body's immune system to fight the infection. One of the genes that the interferons activate encodes a protein called ISG15, which helps to defend the body against viruses. However, it is not clear what role ISG15 plays in fighting bacterial infections.

Here, Radoshevich et al. studied the role of ISG15 in human cells exposed to L. monocytogenes. The experiments show that ISG15 levels increase in the cells, but that the initial increase does not depend on Interferon proteins. Instead, ISG15 production is triggered by an alternative pathway called the cytosolic surveillance pathway, which is activated by the presence of bacterial DNA inside the cell.

Further experiments found that ISG15 can counteract the infections of L. monocytogenes both in cells grown in cultures and in living mice. ISG15 modifies other proteins in the cell to promote the release of proteins called cytokines that help the body to eliminate the bacteria. Radoshevich et al.'s findings reveal a new role for ISG15 in fighting bacterial infections. A future challenge will be to understand the molecular details of how ISG15 triggers the release of cytokines.

DOI:http://dx.doi.org/10.7554/eLife.06848.002

Comparative analysis of cytokine transcript profiles within mediastinal lymph node compartments of pigs after infection with porcine reproductive and respiratory syndrome genotype 1 strains differing in pathogenicity

Porcine reproductive and respiratory syndrome virus (PRRSV) induces a weak immune response enabling it to persist in different organs of infected pigs. This has been attributed to the ability of PRRSV to influence the induction of cytokine responses. In this study, we investigated the cytokine transcriptional profiles in different compartments of the mediastinal lymph node of pigs infected with three genotype 1 PRRSV strains of differing pathogenicity: the low virulence prototype Lelystad virus (LV), and UK field strain 215–06 and the highly virulent subtype 3 SU1-Bel isolate from Belarus. We have used a combination of laser capture micro-dissection (LCM) followed by real time quantitative PCR (RT-qPCR) and immunohistochemical (IHC) detection of immune cell markers (CD3, CD79a and MAC387) and RT-qPCR quantification of PRRSV and cytokine transcripts. Compared to mock infected pigs, we found a significant downregulation of TNF-α and IFN-α in follicular and interfollicular areas of the mediastinal lymph node from 3 days post-infection (dpi) in animals infected with all three strains. This was accompanied by a transient B cell depletion and T cell and macrophage infiltration in the follicles together with T cell depletion in the interfollicular areas. A delayed upregulation of IFN-γ and IL-23p19 was observed mainly in the follicles. The PRRSV load was higher in all areas and time-points studied in the animals infected with the SU1-Bel strain. This paper describes the first application of LCM to study the cytokine transcript profiles and virus distribution in different compartments of the lymph node of pigs.

Non-coding RNA regulation in pathogenic bacteria located inside eukaryotic cells

Intracellular bacterial pathogens have evolved distinct lifestyles inside eukaryotic cells. Some pathogens coexist with the infected cell in an obligate intracellular state, whereas others transit between the extracellular and intracellular environment. Adaptation to these intracellular lifestyles is regulated in both space and time. Non-coding small RNAs (sRNAs) are post-transcriptional regulatory molecules that fine-tune important processes in bacterial physiology including cell envelope architecture, intermediate metabolism, bacterial communication, biofilm formation, and virulence. Recent studies have shown production of defined sRNA species by intracellular bacteria located inside eukaryotic cells. The molecules targeted by these sRNAs and their expression dynamics along the intracellular infection cycle remain, however, poorly characterized. Technical difficulties linked to the isolation of “intact” intracellular bacteria from infected host cells might explain why sRNA regulation in these specialized pathogens is still a largely unexplored field. Transition from the extracellular to the intracellular lifestyle provides an ideal scenario in which regulatory sRNAs are intended to participate; so much work must be done in this direction. This review focuses on sRNAs expressed by intracellular bacterial pathogens during the infection of eukaryotic cells, strategies used with these pathogens to identify sRNAs required for virulence, and the experimental technical challenges associated to this type of studies. We also discuss varied techniques for their potential application to study RNA regulation in intracellular bacterial infections.

The Listeria Small RNA Rli27 Regulates a Cell Wall Protein inside Eukaryotic Cells by Targeting a Long 5'-UTR Variant

Listeria monocytogenes is a bacterial pathogen whose genome encodes many cell wall proteins that bind covalently to peptidoglycan. Some members of this protein family have a key role in virulence, and recent studies show that some of these, such as Lmo0514, are upregulated in bacteria that colonize eukaryotic cells. The regulatory mechanisms that lead to these changes in cell wall proteins remain poorly characterized. Here we studied the regulation responsible for increased Lmo0514 protein levels in intracellular bacteria. The amount of this protein increased markedly in intracellular bacteria (>200-fold), which greatly exceeded the increase in lmo0514 transcript levels (∼6-fold). Rapid amplification of 5'-cDNA ends (RACE) assays identified two lmo0514 transcripts with 5'-untranslated regions (5'-UTR) of 28 and 234 nucleotides. The transcript containing the long 5'-UTR is upregulated by intracellular bacteria. The 234-nucleotide 5'-UTR is also the target of a small RNA (sRNA) denoted Rli27, which we identified by bioinformatics analysis as having extensive base pairing potential with the long 5'-UTR. The interaction is predicted to increase accessibility of the Shine-Dalgarno sequence occluded in the long 5'-UTR and thus to promote Lmo0514 protein production inside the eukaryotic cell. Real-time quantitative PCR showed that Rli27 is upregulated in intracellular bacteria. In vivo experiments indicated a decrease in Lmo0514 protein levels in intracellular bacteria that lacked Rli27. Wild-type Lmo0514 levels were restored by expressing the wild-type Rli27 molecule but not a mutated version unable to interact with the lmo0514 long 5'-UTR. These findings emphasize how 5'-UTR length affects regulation by defined sRNA. In addition, they demonstrate how alterations in the relative abundance of two transcripts with distinct 5'-UTR confine the action of an sRNA for a specific target to bacteria that occupy the intracellular eukaryotic niche.

Optimization of cytotoxicity assay by real-time, impedance-based cell analysis

This paper presents an optimized procedure for assessing an immune-mediated cytotoxicity, produced after the addition of human and baboon serum to transgenic porcine fibroblasts. This procedure is performed with the xCELLigence Real-Time Cell Analyzer (RTCA). The xCELLigence system measures the impedance variations in the culture media of a 96-well microelectronic plate, and shows the changes in cell number and morphology in a real-time plot. However, different factors need to be optimized before developing an RTCA assay. Thus, we studied the influence of several variables, such as the number of cells seeded, the time the cells were allowed to grow before the tests, the serum concentration and the addition of rabbit complement. The findings were confirmed by the WST-1 classical cytotoxicity test. The results showed that 7.5 × 10(3) cells seeded per well produced the adequate CI in 10 h. The area under the curve and the CImin versus concentration values showed a very high correlation index (r(2) = 0.966 and r(2) = 0.92 for the first 50 h after challenge, respectively), proving that CI variations are directly proportional to the quantity of serum added. The addition of complement resulted in lower CImin values. Therefore, both the cytolysis level with and without exogenous complement addition had to be assessed. There was a high correlation between the relative cytotoxicity assessed by WST-1 and the CI obtained by RTCA when exogenous complement was not added (r(2) = 0.827; p < 0.001). The correlation was average when rabbit complement was added (r(2) = 0.523; p = 0.046). In conclusion, culture conditions have an important influence on RTCA cytotoxicity assays.

The Listeria monocytogenes LPXTG surface protein Lmo1413 is an invasin with capacity to bind mucin

Many Gram-positive bacterial pathogens use surface proteins covalently anchored to the peptidoglycan to cause disease. Bacteria of the genus Listeria have the largest number of surface proteins of this family. Every Listeria genome sequenced to date contains more than forty genes encoding surface proteins bearing anchoring-domains with an LPXTG motif that is recognized for covalent linkage to the peptidoglycan. About one-third of these proteins are present exclusively in pathogenic Listeria species, with some of them acting as adhesins or invasins that promote bacterial entry into eukaryotic cells. Here, we investigated two LPXTG surface proteins of the pathogen L. monocytogenes, Lmo1413 and Lmo2085, of unknown function and absent in non-pathogenic Listeria species. Lack of these two proteins does not affect bacterial adhesion or invasion of host cells using in vitro infection models. However, expression of Lmo1413 promotes entry of the non-invasive species L. innocua into non-phagocytic host cells, an effect not observed with Lmo2085. Moreover, overproduction of Lmo1413, but not Lmo2085, increases the invasion rate in non-phagocytic eukaryotic cells of an L. monocytogenes mutant deficient in the acting-binding protein ActA. Unexpectedly, production of full-length Lmo1413 and InlA exhibited opposite trends in a high percentage of L. monocytogenes isolates obtained from different sources. The idea of Lmo1413 playing a role as a new auxiliary invasin was also sustained by assays revealing that purified Lmo1413 binds to mucin via its MucBP domains. Taken together, these data indicate that Lmo1413, which we rename LmiA, for Listeria-mucin-binding invasin-A, may promote interaction of bacteria with adhesive host protective components and, in this manner, facilitate bacterial entry.

Occurrence of mutations impairing sigma factor B (SigB) function upon inactivation of Listeria monocytogenes genes encoding surface proteins

Bacteria of the genus Listeria contain the largest family of LPXTG surface proteins covalently anchored to the peptidoglycan. The extent to which these proteins may function or be regulated cooperatively is at present unknown. Because of their unique cellular location, we reasoned that distinct LPXTG proteins could act as elements contributing to cell wall homeostasis or influencing the stability of other surface proteins bound to peptidoglycan. To test this hypothesis, we used proteomics to analyse mutants of the intracellular pathogen Listeria monocytogenes lacking distinct LPXTG proteins implicated in pathogen-host interactions, such as InlA, InlF, InlG, InlH, InlJ, LapB and Vip. Changes in the cell wall proteome were found in inlG and vip mutants, which exhibited reduced levels of the LPXTG proteins InlH, Lmo0610, Lmo0880 and Lmo2085, all regulated by the stress-related sigma factor SigB. The ultimate basis of this alteration was uncovered by genome sequencing, which revealed that these inlG and vip mutants carried loss-of-function mutations in the rsbS, rsbU and rsbV genes encoding regulatory proteins that control SigB activity. Attempts to recapitulate this negative selection of SigB in a large series of new inlG or vip mutants constructed for this purpose were, however, unsuccessful. These results indicate that inadvertent secondary mutations affecting SigB functionality can randomly arise in L. monocytogenes when using common genetic procedures or during subculturing. Testing of SigB activity could be therefore valuable when manipulating genetically L. monocytogenes prior to any subsequent phenotypic analysis. This test may be even more justified when generating deletions affecting cell envelope components.

Non-ABO blood group systems phenotyping in non-human primates for blood banking laboratory and xenotransplantation

Some biomedical research procedures, such as organ xenotransplantation, usually require intensive hemotherapy. Knowledge of the whole phenotype of blood donor and graft could be useful in the field of xenotransplantation. Human and simian-type categories of blood groups have been established and they can be tested by standard methods used for human blood grouping. The aim of this work was to study the incidence of non-ABO blood group systems in different species of non-human primates, which are employed in biomedical research. The phenotype of Rh, Lewis, Kidd, Kell, MNSs, Lutheran, P and Duffy antigens was investigated in olive baboon (n = 48), chacma baboon (n = 9), Guinea baboon (n = 14), Rhesus macaque (n = 38) and squirrel monkey (n = 30) by using commercial microtyping cards. Kell, Lutheran, Kidd and Duffy antigens have been detected in all species, Rh in squirrel monkey, MNSs in rhesus macaque and squirrel monkey, and Lewis in baboon and rhesus macaque. There were differences in frequency and haemagglutination scores between species regardless of their gender and age. The main differences were found in squirrel monkey when compared with baboons and macaques. This typing system provides a tool to assess the presence of antigens in animals used for experimental procedures, such as xenotransplantation and xenotransfusion.

Assessment of in vitro heparin complement regulation capacity during real-time cell analyzer antibody-mediated cytolysis assay: compatibility studies for pig-to-baboon xenotransplantation

OBJECTIVE

To assess the effect of sodium heparin concentrations on antibody- and complement-mediated cytolysis by means of a real-time cell analyzer system (RTCA) investigating the complement regulation ability of heparin to reduce or prevent hyperacute in an in vitro model of pig-to-baboon xenotransplantation.

MATERIALS AND METHODS

Fibroblasts isolated from the skin of two transgenic pigs were cultured in microelectronic 96-well plates for 9 hours. Then, we added 20 μL of normal sera from two healthy adult olive baboons (Papio anubis) or two volunteer healthy humans. Simultaneous cultures had added heparin at 3.5, 5, 7.5, 15, and 30 IU. Moreover, rabbit complement was added for the exogenous complement group (ExC) versus the other group only with the complement present in the sera as an endogenous complement group (EnC). Cellular cultures were monitored over 150 hours after challenge. With cellular index (CI) data recorded by the xCELLigence software system, we calculate area under the curve versus concentration (AUC) and minimum CI (CImin) versus concentration.

RESULTS

All cultures showed decreased CI after challenge with human or baboon sera. There was a high correlation for AUC (r(2) > 0.90) and CImin versus concentration (r(2) > 0.970) during the first 40 hours postchallenge among the EnC group, regardless of human or baboon sera. However, there was no correlation for AUC and CImin for the ExC group. There was a reduction of CImin related to increased heparin concentrations.

CONCLUSIONS

The addition of heparin did not reduce antibody- and complement-mediated cytolysis assessed in vitro by RTCA in pig-to-baboon compatibility assays.

Generation of human-to-pig chimerism to induce tolerance through transcutaneous in utero injection of cord blood-derived mononuclear cells or human bone marrow mesenchymals cells in a preclinical program of liver xenotransplantation: preliminary results

OBJECTIVE

Using a percutaneous ecoguided injection system to obtain chimeric piglets through a less invasive and traumatic technique than previously reported.

MATERIALS AND METHODS

The two types of human cells included umbilical cord blood mononuclear elements and mesenchymal stem cells cultured from bone marrow. Four sows at gestational day 50 were anesthetized. A needle was inserted through the skin and uterine wall to reach the peritoneal cavity of the fetuses under continuous ultrasound guidance. Fourteen piglets were injected with various cell concentrations.

RESULTS

All sows carried pregnancies to term yielding 69 piglets, among which 67 were alive and two mummified. Two piglets died during the first 48 hours of life. Chimerism was detected using flow cytometry and by quantitative polymerase chain reaction (q-PCR) to detect Alu gene in blood or tissues samples. The analysis detected blood chimerism in 13 piglets (21%) by flow cytometry and the presence of the human Alu gene in 33 (51%) by q-PCR. The results suggest cell trafficking between littermates after in utero injection.

CONCLUSIONS

Transcutaneous echo-guided injection succeeded to produce chimeric piglets without disadvantages to the sow or the fetuses and avoiding abortions or fetal death.

Contribution of sortase A to the regulation of Listeria monocytogenes LPXTG surface proteins

Gram-positive bacteria of the genus Listeria contain many surface proteins covalently bound to the peptidoglycan. In the pathogenic species Listeria monocytogenes, some of these surface proteins mediate adhesion and entry into host cells. Specialized enzymes called sortases anchor these proteins to the cell wall by a mechanism involving processing and covalent linkage to the peptidoglycan. How bacteria coordinate the production of sortases and their respective protein substrates is currently unknown. The present work investigated whether the functional status of the sortase influences the level at which its cognate substrates are produced. The relative amounts of surface proteins containing an LPXTG sorting motif recognized by sortase A (StrA) were determined in isogenic wild-type and ΔsrtA strains of L. monocytogenes. The possibility of regulation at the transcriptional level was also examined. The results showed that the absence of SrtA did not affect the expression of any of the genes encoding LPXTG proteins. However, marked differences were found at the protein level for some substrates depending on the presence/absence of SrtA. In addition to the known "mis-sorting" of some LPXTG proteins caused by the absence of SrtA, the total amount of certain LPXTG protein species was lower in the ΔsrtA mutant. These data suggested that the rate of synthesis and/or the stability of a subset of LPXTG proteins could be regulated post-transcriptionally depending on the functionality of SrtA. For some LPXTG proteins, the absence of SrtA resulted in only a partial loss of the protein that remained bound to the peptidoglycan, thus providing support for additional modes of cell-wall association in some members of the LPXTG surface protein family.

Characterization of tuberculous lesions in naturally infected African buffalo (Syncerus caffer)

Tuberculosis pathology was studied on 19 African buffalo (Syncerus caffer) from a herd in the Hluhluwe-iMfolozi Park in South Africa. The animals tested positive with the comparative intradermal tuberculin test and were euthanized during a test-and-cull operation to decrease prevalence of bovine tuberculosis (bTB) in the park. The lymph nodes and lungs were examined grossly for presence of tuberculous lesions, which were scored on a 0-5 scale for macroscopic changes. The gross lesions were examined histologically and classified into grade I, II, III, or IV according to a grading system used for bTB lesions in domestic cattle. Macroscopic lesions were limited to the retropharyngeal, bronchial, and mediastinal lymph nodes and the lungs. The most frequently affected lymph nodes were the bronchial (in 16 animals) and mediastinal (in 11 animals). All four grades of microscopic lesions were observed, grade II lesions were the most frequent. Mycobacterium bovis was detected by PCR in 8 out of 19 animals, and acid-fast bacilli were seen in 7 out of 19 animals, together both techniques identified mycobacteria in 5 out of 19 animals. Lesions were paucibacillary, as acid-fast bacilli were only rarely observed. The absence of lesions in the mesenteric lymph nodes and the high frequency of lesions in respiratory tract associated lymph nodes suggest that the main route of M. bovis infection in African buffalo is by inhalation.

Porcine endogenous retrovirus copy number in different pig breeds is not related to genetic diversity

The risk of zoonoses is a major obstacle to xenotransplantation. Porcine endogenous retrovirus (PERV) poses a potential risk of zoonotic infection, and its control is a prerequisite for the development of clinical xenotransplantation. The copy number of PERV varies among different breeds, and it has been suggested that the PERV integrations number is increased by inbreeding. The purpose of this study was (i) to examine the copy number of PERV in different Spanish pig breeds, Spanish wild boar and commercial cross-bred pigs from five different farms and genetic background (CCP1-CCP5) and (ii) to investigate the correlation between PERV copy number and the genetic background of the pigs in order to improve the selection of pigs for xenotransplantation. PERV copy number was determined by quantitative, real-time polymerase chain reactions. Thirty-four microsatellite markers were genotyped to describe the genetic diversity within populations (observed and expected heterozygosities, Ho and He, respectively) and the inbreeding coefficient (F). Pearson's correlation coefficient was used to determine the relationship between PERV copy number and Ho, He and F. The copy number of PERV among different pig breeds was estimated to range between three (CCP1) and 43 copies (Iberian Pig). Statistical differences were found among the studied populations concerning PERV copy number. No correlation was found between the PERV copy number and the heterozygosity (calculated at an individual level or at a population level) or the inbreeding coefficient of each population. Our data suggest that pigs inbreeding does not increase PERV copy number and support the idea that careful selection of pigs for organ donation with reduced PERV copy number will minimize the risk of retrovirus transmission to the human receptor.

Acute phase proteins as a tool for differential diagnosis of wasting diseases in growing pigs

The concentrations of haptoglobin (Hp), C-reactive protein (CRP) and serum amyloid A (SAA) were measured in wasted pigs, first to evaluate their usefulness in the diagnosis of infectious, wasting diseases in pigs, and second, to evaluate whether their concentrations can distinguish the lymphoid depletion score in the lymph tissues of wasted affected pigs. Fifty-three wasted pigs and seven specific pathogen free (SPF) pigs were postmortem examined. Gross lesions were evaluated and samples for histopathological, immunohistochemical, molecular biology and microbiological analysis were taken. Thirty-one pigs were diagnosed as postweaning multisystemic wasting syndrome (PMWS) and 22 as porcine respiratory disease complex (PRDC). Lymphoid depletion degree in lymph tissues of PMWS and PRDC affected pigs was determined. Serum Hp was significantly higher in pigs with PRDC in comparison with the PMWS affected pigs. Serum CRP concentration was significantly lower in pigs with PRDC than in PMWS affected pigs (P<0.001). CRP and SAA levels increased with the lymphoid depletion score, presenting statistical differences between pigs with no depletion and pigs with low, moderate or severe lymphoid depletion (P<0.05, P<0.05 and P<0.001 for CRP and P<0.01, P<0.01 and P<0.01 for SAA, respectively). Hp was higher in pigs with no or low depletion compared with the pigs suffering severe lymphoid depletion (P<0.001 and P<0.05, respectively).

Validation of xCELLigence real-time cell analyzer to assess compatibility in xenotransplantation with pig-to-baboon model

OBJECTIVE

To validate the use of a microelectronic real-time cell analyzer system (RTCA) we developed a complement-mediated antibody cytotoxicity assay to investigate the compatibility of a graft and a recipient in pig-to-baboon xenotransplantation.

MATERIALS AND METHODS

Fibroblasts isolated from the skin of five hCD55, hCD59, and hCD46 transgenic pigs (TP) were cultured in 96 microelectronic well plates for 17 hours. Then, we added to each microwell 20 μL of normal sera from nine healthy adult olive baboons (Papio anubis)-three males and six females. The evolution of the cell culture was assessed every 3 minutes during the pretreatment period, at 11 hours postaddition, and every 30 minutes from 12 to 96 hours. Simultaneously, we performed a 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Fibroblasts from wild-type (WT) pigs were used as positive controls and microwells without serum addition from each TP as negative controls. The RTCA results were expressed as a normalized cellular index (NCI).

RESULTS

Differences were observed between the five TP fibroblasts and the WT fibroblasts, with greater cytotoxicity on WT cells. Among TP, a higher cytolytic level was observed in males than females. The MTT results correlated with NCI at different times, with the minimum NCI and with the time to for NCI recovery before serum addition. The correlation was lower than that previously reported in environmental toxicity assays.

CONCLUSIONS

RTCA allows a long-term assessment of the immunocytotoxic effect of baboon sera on pig cells, providing a suitable tool to perform compatibility tests for xenotransplantation.

Use of Real-Time and Classic Polymerase Chain Reaction Assays for the Diagnosis of Porcine Tuberculosis in Formalin-Fixed, Paraffin-Embedded Tissues

The current study was carried out to set up a fast and specific technique for porcine tuberculosis diagnosis in formalin-fixed, paraffin-embedded tissues. A retrospective study was carried out using 54 samples fixed in 10% neutral buffered formalin from 29 slaughtered Iberian pigs. Most of the pigs showed tissue samples positive to immunohistochemical staining (70.4%), and mycobacteria were detected within or near the necrotic cores of the lesions. However, diagnosis by this technique was time-consuming and tedious because of the paucibacillar nature of porcine tuberculous lesions. Classic polymerase chain reaction (PCR) was unsuccessful in mycobacteria genome amplification in all of the examined samples; however, real-time PCR amplified the mycobacteria genome in 23 of 29 examined pigs, identifying the Mycobacterium tuberculosis complex in all but one, which amplified Mycobacterium avium complex. Moreover, when reamplification of the DNA was performed, classic PCR amplified the mycobacteria genome in all the examined pigs (29/29), identifying the M. tuberculosis complex in 28 of 29 studied pigs and M. avium complex in only 1 pig. Results of the current study point out that both real-time and classic PCR assays, with genome reamplification, represent sensitive, fast, and specific diagnostic tools for porcine tuberculosis in formalin-fixed, paraffin-embedded tissues.

Clinical, histologic, and immunohistochemical features of an undifferentiated renal tubular carcinoma in a juvenile olive baboon (Papio anubis)

An undifferentiated renal tubular carcinoma was diagnosed in a juvenile male olive baboon (Papio anubis). The animal suddenly appeared depressed and refused to eat. During physical examination, a firm, palpable mass in the left abdominal area and flank pain were detected. Clinical pathology findings included mild anemia, hypoalbuminemia, hyponatremia, and mildly increased serum creatinine and urea concentrations. Radiographs revealed a large mass in the left abdominal area. Exploratory laparotomy disclosed a 10 cmx15 cm multilobulated mass involving the left kidney and adjacent organs. Because of a poor prognosis, the animal was humanely euthanized, and necropsy was performed. Tissue samples of the neoplasm were taken for histopathological examination. Immunohistochemical staining was done using vimentin, cytokeratin, S-100 protein, Ki-67, alpha-actin, and desmin-specific primary antibodies. Microscopically, elongated and irregular tubules were lined by 2 or more layers of atypical epithelial cells. Anisocytosis, anisokaryosis, and frequent mitotic figures were also observed. Following immunohistochemical staining, the cytoplasm of neoplastic cells was positive for cytokeratin, vimentin, and S-100 protein and negative for alpha-actin and desmin. Positive nuclear staining for Ki-67 was observed. The neoplasm was diagnosed as an undifferentiated renal tubular carcinoma.