Antibiotic resistant Escherichia coli in southeastern Australian pig herds and implications for surveillance.

To investigate public health implications of antibiotics to control post-weaning scours, we surveyed 22 commercial pig herds in southeastern Australia. Fifty faecal samples per herd were collected from pre- and post-weaned piglets. Presumptive Escherichia coli isolates were confirmed by MALDI-TOF MS. Isolates (n = 325) were screened for susceptibility to 19 veterinary antibiotics using MIC broth microdilution. All 325 E. coli isolates underwent further testing against 27 antibiotics used in human medicine and were screened for ETEC adhesin and enterotoxin genes (F4 (K88), F5 (K99), F6 (987P), F18, F41, STa, STb, Stx2e and LT) by multiplex PCR. Isolates identified as phenotypically resistant to third-generation cephalosporin (3GC) and aminoglycoside antibiotics were screened by multiplex PCR/reverse line blot to detect common ß-lactam and aminoglycosides resistance genes, confirmed by sequencing. Twenty (6.1%) of the E. coli isolates were resistant to 3GC antibiotics and 24 (7.4%) to the aminoglycoside antibiotic gentamicin. Genetic analysis revealed six different extended spectrum ß-lactamase (ESBL) genes (blaCTX-M-1, -14, -15, -27, blaSHV-12 and blaCMY-2-like genes), four of which have not been previously reported in Australian pigs. Critically, the prevalence of 3GC resistance was higher in non-pathogenic (non-ETEC) isolates and those from clinically normal (non-diarrhoeal) samples. This highlights the importance of non-ETECE. coli as reservoirs of antimicrobial resistance genes in piglet pens. Antimicrobial resistance surveillance in pig production focused on diagnostic specimens from clinically-affected animals might be potentially misleading. We recommend that surveillance for emerging antimicrobial resistance such as to 3GC antibiotics should include clinically healthy pigs.

A longitudinal study of the prevalence and super-shedding of Escherichia coli O157 in dairy heifers.

The fecal shedding and super-shedding of the human pathogen Escherichia coli O157 by cattle has been the focus of many previous studies with varied results observed. The heterogeneity of shedding is becoming more accepted, both in the numbers of animals shedding and the levels at which animals shed. To clarify patterns in shedding and super-shedding we undertook a longitudinal study to investigate shedding within a cohort of replacement dairy heifers. The cohort of 52 heifers was sampled 18 times at approximately weekly intervals with no significant changes in management during the sampling period. An overall prevalence of 44.3% (412/930 samples) was detected with prevalence ranging from 9.6 to 94.3% at individual sampling points. Each of the 52 heifers yielded at least one sample which was detected positive for E. coli O157. Super-shedding was detected at a sample level of 3.6% (32/893) and ranged between 0 and 9.6% at each sampling point. Of the 52 heifers, 24 (46.2%) were detected to be super-shedding at some point during the study, 19 of which were detected as super-shedding at only one point. From our findings we conclude that super-shedding is not associated with a small subset of animals that shed at high levels continually as had been proposed by earlier studies. We propose that the term 'super-shedding event' as opposed to 'super-shedding animal' better describes the nature of shedding.

Relative sensitivity of Escherichia coli O157 detection from bovine feces and rectoanal mucosal swabs.

The need to quantify the potential human health risk posed by the bovine reservoir of Escherichia coli O157 has led to a wealth of prevalence studies and improvements in detection methods over the last two decades. Rectoanal mucosal swabs have been used for the detection of E. coli O157 fecal shedding, colonized animals, and those predisposed to super shedding. We conducted a longitudinal study to compare the detection of E. coli O157 from feces and rectoanal mucosal swabs (RAMS) from a cohort of dairy heifers. We collected 820 samples that were tested by immunomagnetic separation of both feces and RAMS. Of these, 132 were detected as positive for E. coli O157 from both samples, 66 were detected as positive from RAMS only, and 117 were detected as positive from feces only. The difference in results between the two sample types was statistically significant (P < 0.001). The relative sensitivities of detection by immunomagnetic separation were 53% (confidence interval, 46.6 to 59.3) from RAMS and 67% (confidence interval, 59.6 to 73.1) from fecal samples. No association between long-term shedding (P = 0.685) or super shedding (P = 0.526) and detection by RAMS only was observed.

Application of a three-dimensional auditory display in a flight task.

The effectiveness of a three-dimensional (3D) auditory display in conveying directional information was investigated in a flight simulation experiment. While flying a simulated fighter aircraft, participants followed a target aircraft that suddenly disappeared and reemerged at an unknown position. The task was to locate and trail the target as quickly as possible. In all conditions the participants viewed a computer-generated outside image, on which they could spot the target only when it was at short range, and a three-dimensional (3D) tactical display indicating the target position at all distances within a limited field of view. Additional displays were a bird's-eye-view radar display, which also indicated whether the target was above or below the own plane, and a 3D auditory display, which generated a warning sound from the relative direction of the target. The auditory display used individualized head-related transfer functions to create a virtual sound source and a head-tracking device to decouple the position of the source from head movements. Results show that the radar and auditory displays caused about the same significant reduction in search time in comparison with the tactical display only. A further reduction was found when the two additional displays were presented simultaneously.