Carriage of antibiotic-resistant enteric bacteria varies among sites in Galapagos reptiles

Increased overlap between humans and wildlife populations has increased the risk for novel disease emergence. Detecting contacts with a high risk for transmission of pathogens requires the identification of dependable measures of microbial exchange. We evaluated antibiotic resistance as a molecular marker for the intensity of human-wildlife microbial connectivity in the Galápagos Islands. We isolated Escherichia coli and Salmonella enterica from the feces of land iguanas (Conolophus sp.), marine iguanas (Amblyrhynchus cristatus), giant tortoises (Geochelone nigra), and seawater, and tested these bacteria with the use of the disk diffusion method for resistance to 10 antibiotics. Antibiotic-resistant bacteria were found in reptile feces from two tourism sites (Isla Plaza Sur and La Galapaguera on Isla San Cristóbal) and from seawater close to a public use beach near Puerto Baquerizo Moreno on Isla San Cristóbal. No resistance was detected at two protected beaches on more isolated islands (El Miedo on Isla Santa Fe and Cape Douglas on Isla Fernandina) and at a coastal tourism site (La Lobería on Isla San Cristóbal). Eighteen E. coli isolates from three locations, all sites relatively proximate to a port town, were resistant to ampicillin, doxycycline, tetracycline, and trimethoprin/sulfamethoxazole. In contrast, only five S. enterica isolates showed a mild decrease in susceptibility to doxycycline and tetracycline from these same sites (i.e., an intermediate resistance phenotype), but no clinical resistance was detected in this bacterial species. These findings suggest that reptiles living in closer proximity to humans potentially have higher exposure to bacteria of human origin; however, it is not clear from this study to what extent this potential exposure translates to ongoing exchange of bacterial strains or genetic traits. Resistance patterns and bacterial exchange in this system warrant further investigation to understand better how human associations influence disease risk in endemic Galápagos wildlife.     

Color discrimination in wild boars

Two experiments were carried out in order to clarify the color perception of Japanese wild boarsSus scrofa leucomystax. Two females were trained using an operant conditioning technique to press a switch under a positive stimulus color card in order to receive food as a reward. In Exp. 1, they were tested for discrimination between 3 colors (red, green and blue) and gray. The luminosity of all colors was the same. The wild boars succeeded in discrimination tests between blue and gray, but failed to discriminate red from gray. They also did not discriminate green from gray so clearly as blue from gray. In Exp. 2, the same wild boars were tested to discriminate between 8 kinds of color, which were created by gradating green yellow into red purple except for the 3 colors used in Exp. 1, and gray. They could clearly discriminate blue, purple blue and a part of purple from gray. In these experiments, wild boars were capable of recognizing bluish colors. However, for colors approaching green or yellow, they failed the test by degrees.     

Trichinella nativa in sylvatic wild boars.

Of 17 Trichinella isolates from domestic pigs and wild boars (Sus scrofa) in regions where Trichinella nativa is widespread among sylvatic animals, two wild boars from Estonia were found to be naturally infected with this Trichinella species. The other 15 animals were infected with Trichinella spiralis. Trichinella nativa is tolerant to freezing when in the muscles of carnivores. The biological characteristics and temperature tolerance of this species in swine need to be further investigated if pork is certified for consumption following freezing.     

Occurrence of yersiniosis and listeriosis in wild boars in Japan

From December 1994 to February 1995, 131 wild boars (Sus scrofa leucomysta) living in a mountainous area in Japan were examined for yersiniosis and listeriosis. Of 131 wild boars, 76 (58%) were males and 55 (42%) were females. Four Yersinia spp. including Y. pseudotuberculosis, Y. enterocolitica, Y. frederiksenii, and Y. aldovei, were isolated from 49 (37%) of 131 wild boars. Yersinia pseudotuberculosis was isolated from five (4%) of 131 wild boars. All Y. pseudotuberculosis isolates were serotype 4b and harbored virulence plasmids. Yersinia pseudotuberculosis was isolated only from boars under 2-yr-old. No human pathogenic Y. enterocolitica was isolated. Listeria monocytogenes was isolated from two (1%) of the wild boars and both isolates were serotype 4b. These findings indicated that wild boar could be a reservoir of Y. pseudotuberculosis and L. monocytogenes in Japan.     

Raman-activated sorting of antibiotic-resistant bacteria in human gut microbiota

The antibiotic-resistant bacteria (ARB) and antibiotic-resistant genes (ARGs) in human gut microbiota have significant impact on human health. While high throughput metagenomic sequencing reveals genotypes of microbial communities, the functionality, phenotype and heterogeneity of human gut microbiota are still elusive. In this study, we applied Raman microscopy and deuterium isotope probing (Raman–DIP) to detect metabolic active ARB (MA-ARB) in situ at the single-cell level in human gut microbiota from two healthy adults. We analysed the relative abundances of MA-ARB under different concentrations of amoxicillin, cephalexin, tetracycline, florfenicol and vancomycin. To establish the link between phenotypes and genotypes of the MA-ARB, Raman-activated cell sorting (RACS) was used to sort MA-ARB from human gut microbiota, and mini-metagenomic DNA of the sorted bacteria was amplified, sequenced and analysed. The sorted MA-ARB and their associated ARGs were identified. Our results suggest a strong relation between ARB in human gut microbiota and personal medical history. This study demonstrates that the toolkit of Raman–DIP, RACS and DNA sequencing can be useful to unravel both phenotypes and genotypes of ARB in human gut microbiota at the single-cell level.     

Modeling the role of altruism of antibiotic-resistant bacteria

Based on the new findings in a recent experimental study (Lee et al., Nature 467, 82–86, 2010) that antibiotic resistant mutants of bacteria produce indoles to protect the wild strain bacteria, we propose a mathematical model to describe the evolution of the wild strain, resistant strain and indoles with limited nutrient. We distinguish two cases: (i) mutation is negligible and a resistant strain preexists; (ii) mutation is not negligible. For (i), we establish conditions for co-persistence of both strains, which indicate that the wild strain can survive with the help from the altruistic resistant strain, whereas it dies out in the absence of such a benefit. This consolidates the experimental findings in Lee et al. (Nature 467:82–86 2010). Further analysis and simulations also reveal some new phenomena not reported in Lee et al. (Nature 467:82–86 2010), that is, periodic oscillations of the populations may occur within certain range of the parameters, and there exists bistability in the sense that a stable positive periodic solution coexists with a stable positive equilibrium.     

Assessment of microbial carcass contamination of hunted wild boars

To investigate the microbiological conditions of hunted wild boar carcasses and factors that contribute to the microbial carcass contamination, skin and carcass meat swab samples from 210 hunted wild boars were collected from freshly shot animals. The mean aerobic colony counts (ACCs) and Enterobacteriaceae counts on the skin were 5.2 and 3.6 log₁₀ CFU/cm², with 1.4% of animals’ skin tested positive for Salmonella spp. Slightly higher mean ACC and Enterobacteriaceae counts of 5.4 and 3.8 log₁₀ CFU/cm² were obtained from carcass meat with Salmonella spp. prevalence of 1.9%. Inadequate hygiene practices in handling and dressing wild boar carcasses, such as evisceration in the laying position on the ground and practice of skin and interior carcass surface washing after evisceration, were found to have the most significant influence on the microbiological conditions of final carcasses. Therefore, these findings indicate the need for the implementation and strict adherence to good hygiene practice in hunting estates and game handling establishments.     

A serological study on brucellosis in wild boars in Germany

A recent outbreak of brucellosis in an outdoor pig herd, where wild boars were identified as the most probable source of infection, prompted us to conduct a serological study on wild boars from five federal states of Germany. A total of 885 sera were examined using a combination of screening and confirmatory testing, i.e. indirect enzyme-linked immunosorbent assay (ELISA) followed by complement fixation and slow agglutination tests. Seroprevalences of Brucella suis antibodies in the various regions were between 0 and 28.5% in the ELISA. After confirmatory testing, the amount of positive sera was lower and reached only up to 12.1%, dependent on the method. Although wild boars usually harbour B. suis biovar 2, which is less virulent for humans, a zoonotic risk for persons dealing with these animals and their carcasses cannot be ruled out.     

Prevalence of Streptococcus suis genotypes in wild boars of Northwestern Germany

Invasive serotype 2 (cps2+) strains of Streptococcus suis cause meningitis in pigs and humans. Four case reports of S. suis meningitis in hunters suggest transmission of S. suis through the butchering of wild boars. Therefore, the objective of this study was to investigate the prevalence of potentially human-pathogenic S. suis strains in wild boars. S. suis was isolated from 92% of all tested tonsils (n=200) from wild boars. A total of 244 S. suis isolates were genotyped using PCR assays for the detection of serotype-specific genes, the hemolysin gene sly, and the virulence-associated genes mrp and epf. The prevalence of the cps2+ genotype among strains from wild boars was comparable to that of control strains from domestic pig carriers. Ninety-five percent of the cps2+ wild boar strains were positive for mrp, sly, and epf*, the large variant of epf. Interestingly, epf* was significantly more frequently detected in cps2+ strains from wild boars than in those from domestic pigs; epf* is also typically found in European S. suis isolates from humans, including a meningitis isolate from a German hunter. These results suggest that at least 10% of wild boars in Northwestern Germany carry S. suis strains that are potentially virulent in humans. Additional amplified fragment length polymorphism analysis supported this hypothesis, since homogeneous clustering of the epf* mrp+ sly+ cps2+ strains from wild boars with invasive human and porcine strains was observed.     

Population genetic structure of wild boars in the West Balkan region

We investigated the population genetic structure of wild boars from Vojvodina (Serbia), Slavonija (Croatia) and Bosnia using four microsatellite markers. All loci presented a high degree of polymorphism and a total of 76 alleles (mean 19 alleles per locus) were detected. Average observed heterozygosity (H _o) value was 0.60. Deviation from Hardy-Weinberg equilibrium was found due to significant heterozygote deficiency detected for three of the four analyzed loci and for all populations. F _IS value over all loci and all populations was 0.29, and the effective number of migrants based on private alleles was 1.64. Sufficient levels of gene flow were found between all populations and the spatial structure showed slightly closer nuclear gene pool affinity of Vojvodina and Slavonija populations in relation of Bosnia population.     

Prevalence of antibody to six Leptospira servovars in Swedish wild boars

Zoonotic Leptospira bacteria are pathogens that may increase in importance with climate change. We investigated the prevalence of antibody to six Leptospira serovars (sv) in the Swedish wild boar (Sus scrofa) population, which is increasing in number and geographic distribution. The serovars we selected cause disease in pigs or may be of use as sentinel serovars to measure the potential spread in Swedish fauna. In total, 386 serum samples from wild boars collected between 2005 and 2007 were investigated using a microscopic agglutination test for Leptospira interrogans sv Bratislava strain Jez Bratislava, sv Icterohaemorrhagiae strain Kantorowicz, sv Pomona strain Pomona, Leptospira kirschneri sv Grippotyphosa strain Duyster, and Leptospira borgpetersenii sv Tarassovi strain Perepelitsin, and a domestic strain closely related to sv Sejroe. Twelve (3.1%) of the analyzed samples were antibody-positive. Of those, nine (2.3%) were positive for sv Bratislava and 0.8% for sv Icterohaemorrhagiae. All antibody-positive samples originated from areas where wild boars are reported to be common. We conclude that Leptospira infection is less common in Swedish wild boar than in continental Europe. However, we recommend continuous surveillance to follow the effects of climate change and an increasing wild boar population.     

Nitrogen cycling processes and soil characteristics in an urban versus rural forest

Different soils of an urban forest in New York City showed relatively low, yet similar rates of N mineralization and nitrification in laboratory potential measurements. This consistent pattern occurred even though a number of factors known to influence these processes (including overstory vegetation, soil type, and heavy metal levels) differed between the urban samples. Net N mineralization rates in forest floor and A horizon samples from a hemlock stand within the urban forest were 81% and 53% lower than respective samples from a comparable rural stand. In addition, all forest floor and A horizon samples from the urban forest were extremely hydrophobic. The low mineralization rates and hydrophobic nature of the urban samples suggested that factors associated with the urban grime hydrocarbons may be limiting the activity of soil microbes and invertebrates. Trampling and high concentrations of heavy metals may have synergistic effects that would act to reduce net N mineralization and nitrification within the urban forest.     

Magnetic alignment in warthogs Phacochoerus africanus and wild boars Sus scrofa

Magnetic alignment (MA) results from the preference of animals to align themselves along the field lines of the geomagnetic field, a behavioural expression of a magnetic sense. MA is well documented for ruminants and might demonstrate a general magnetic sensory ability among artiodactyls. We measured body‐axis alignment in 1614 foraging or resting wild boars Sus scrofa, 1849 wild boar beds, and 1347 warthogs Phacochoerus africanus, and found a highly significant north–south preference. The magnetic field was the only common denominator of all observations. Thus, we provide the first data suggesting a magnetic sense in the Suidae.     

小兴安岭南坡野猪家域分析

采用笼式活捕野猪,利用无线电遥测技术、R2V、Arcview 和SPSS 软件技术,于2004 年7 月15 日至2006年1 月19 日,对小兴安岭南坡野猪家域进行测定、计算和分析,以了解该地区野猪的家域变化规律。研究结果表明:季节变化影响野猪家域面积,在春、秋季,野猪的家域面积显著大于冬季,而春、夏季间无显著差异;不同性别及年龄野猪家域大小也不同,成体雄性秋季发情期和亚成体春季分窝期家域面积显著增加;在冬、春季家族群野猪的家域面积显著大于独体野猪家域面积,说明家族群对家域面积有影响;亚成体家域大小主要受家族群家域的影响,家族群野猪面积大,相应地家族野猪中亚成体家域面积也大。     

A field test of the audibility of urban versus rural songs in mountain chickadees

Anthropogenic noise can mask avian vocalizations, and several urban‐dwelling species adjust frequency or amplitude of vocalizations in ways that appear to compensate for increased noise levels. Playback studies have investigated whether receivers differentiate between signals produced by rural and urban males, but it is difficult to determine whether differential response to stimulus reflects differences in audibility versus perceived differences in male signals/condition that result from urban settlement. Here, we performed paired‐playback trials to determine whether mountain chickadees (Poecile gambeli) differentiate urban versus rural songs when both stimuli were broadcast within noise. For each playback, stimuli were played in short bouts starting at a low signal‐to‐noise ratio and increasing in relative amplitude with each successive bout. If the primary function of adjusted urban songs is propagation in noise, we hypothesized that focal males would respond sooner to urban versus rural playbacks (detect at lower signal‐to‐noise ratios). If urban songs solely encode information about the male's condition (such as increased aggression), then we predicted only a differential aggressive response to playbacks once detected. If urban songs both increase propagation and embed information on male condition, we predicted a combination of both response types. We found no difference in latency to first response in urban versus rural songs, but some evidence for differential aggression to playback dependent on both stimulus type (urban vs. rural) and local ambient noise levels; focal males in noisy (urban) sites responded aggressively to both stimulus types, whereas focal males in quiet (rural) sites responded more aggressively to urban than to rural stimuli. This context‐dependent discrimination may be the result of increased aggression in urban habitats, improved communication in noisy habitats by urban signallers and receivers, or some combination of the two.     

Intestinal protozoa in wild boars (Sus scrofa) in western Iran

A total of 12 gastrointestinal tracts of wild boars (Sus scrofa) from western Iran (Luristan) were examined for protozoan infection between September 2000 and November 2001. Of 12 boars examined, 67% harbored one or more species of the following protozoa: Balantidium coli (25%), Tritrichomonas suis (25%), Blastocystis sp. (25%), Entamoeba polecki (17%), Entamoeba suis (8%), Iodamoeba butschlii (17%), and Chilomastix mesnili (8%). Four of these protozoan species also are reported in humans, and persons living in rural areas where wild boars are abundant should take precaution to avoid infection.