Clinical resistance and decreased susceptibility in Streptococcus suis isolates from clinically healthy fattening pigs

Streptococcus suis (S. suis) has often been reported as an important swine pathogen and is considered as a new emerging zoonotic agent. Consequently, it is important to be informed on its susceptibility to antimicrobial agents. In the current study, the Minimum Inhibitory Concentration (MIC) population distribution of nine antimicrobial agents has been determined for nasal S. suis strains, isolated from healthy pigs at the end of the fattening period from 50 closed or semiclosed pig herds. The aim of the study was to report resistance based on both clinical breakpoints (clinical resistance percentage) and epidemiological cutoff values (non-wild-type percentage). Non-wild-type percentages were high for tetracycline (98%), lincomycin (92%), tilmicosin (72%), erythromycin (70%), tylosin (66%), and low for florfenicol (0%) and enrofloxacin (0.3%). Clinical resistance percentages were high for tetracycline (95%), erythromycin (66%), tylosin (66%), and low for florfenicol (0.3%) and enrofloxacin (0.3%). For tiamulin, for which no clinical breakpoint is available, 57% of the isolates did not belong to the wild-type population. Clinical resistance and non-wild-type percentages differed substantially for penicillin. Only 1% of the tested S. suis strains was considered as clinically resistant, whereas 47% of the strains showed acquired resistance when epidemiological cutoff values were used. In conclusion, MIC values for penicillin are gradually increasing, compared to previous reports, although pigs infected with strains showing higher MICs may still respond to treatment with penicillin. The high rate of acquired resistance against tiamulin has not been reported before. Results from this study clearly demonstrate that the use of different interpretive criteria contributes to the extent of differences in reported antimicrobial resistance results. The early detection of small changes in the MIC population distribution of isolates, while clinical failure may not yet be observed, provides the opportunity to implement appropriate risk management steps

Moisture source and diet affect development and reproduction of Orius thripoborus and Orius naivashae, two predatory anthocorids from southern Africa

The effect of moisture source and diet on the development and reproduction of the pirate bugs, Orius thripoborus (Hesse) and Orius naivashae (Poppius) (Hemiptera: Anthocoridae) was examined in the laboratory. Both species had been collected in and around sugarcane fields in South Africa. Supplementing eggs of the flour moth Ephestia kuehniella (Zeller) (Lepidoptera: Pyralidae) with a green bean pod as a moisture source yielded better nymphal survival and faster development, as compared with free water encapsulated in Parafilm, suggesting that the predators may extract extra nutrients from the bean pod. The impact of two factitious foods and moist honey bee pollen on developmental and reproductive parameters of both predators was also investigated. The overall performance of both Orius species on E. kuehniella eggs and cysts of brine shrimp, Artemia franciscana Kellogg (Crustacea: Artemiidae) was better than on pollen. Nonetheless, a pollen diet alone allowed 66 and 78% of the nymphs of O. thripoborus and O. naivashae, respectively, to reach adulthood. Overall, developmental and reproductive performance of O. thripoborus on the tested diets was superior to that of O. naivashae. The implications of these findings for the mass production of these predators and their potential role in biological control programs in southern Africa are discussed

Occurrence, ecology and potential impact of the New Zealand wheat bug Nysius huttoni White (Hemiptera: Lygaeidae) in Belgium

In 2002 the New Zealand wheat bug Nysius huttoni White was observed for the first time in the Netherlands and Belgium. The introduction of N. huttoni to our regions presumably occurred via overseas transport of apple and kiwi fruits from New Zealand. Laboratory experiments showed that both eggs and adults of N. huttoni were capable of surviving cold conditions similar to those in overseas transportation. Specimens were sampled in Belgium and the Netherlands, and a DNA sequence analysis indicated a 100% similarity with N. huttoni material collected in Christchurch, New Zealand. The distribution of the lygaeid in Belgium in 2008 was studied based on a systematic sampling at 105 locations. The bug had been able to spread over most of the Belgian territory, with the exception of the most southern and eastern provinces. Given the poor flight capacity of Belgian N. huttoni populations, other methods of dispersal may be involved. N. huttoni occurred primarily in ruderal habitats, and its weedy host plants belong to very common plant families. Several observations support N. huttoni not being a threat for agricultural crops in Belgium under the present conditions of climate and soil usage

Gevoeligheid van belgische Mycoplasma Hyopneumoniae isolaten voor antimicrobiële middelen

To control Mycoplasma hyopneumoniae infections, the use of antibiotics in feed or water is a common practice. Unfortunately, information concerning the susceptibility of M. hyopneumoniae to different antimicrobials is very scarce. The in vitro susceptibility of 21 M hyopneumoniae field isolates was determined in this study using a broth microdilution technique. Acquired resistance to spectinomycin, oxytetracycline, doxycycline, gentamicin, florfenicol and tiamulin was not observed. One isolate showed acquired resistance to lincomycin, tilmicosin and tylosin, but was susceptible to all other antibiotics tested. For 5 isolates, the MIC-values of flumequine were > 16 mu g/ml, while the MIC50-value was 2 mu g/ml. The MIC-values of enrofloxacin for these 5 isolates were >= 0.5 mu g/ml, the MIC50 being 0.06 mu g/ml. This is the first report showing acquired resistance against macrolides, lincosamides and fluoroquinolones in M hyopneumoniae field isolates