Current perspectives on the diagnosis and epidemiology of Mycoplasma hyopneumoniae infection

Mycoplasma hyopneumoniae is the principal aetiological agent of enzootic pneumonia (EP), a chronic respiratory disease that affects mainly finishing pigs. Although major efforts to control M. hyopneumoniae infection and its detrimental effects have been made, significant economic losses in pig production worldwide due to EP continue. M. hyopneumoniae is typically introduced into pig herds by the purchase of subclinically infected animals or, less frequently, through airborne transmission over short distances. Once in the herd, M. hyopneumoniae may be transmitted by direct contact from infected sows to their offspring or between pen mates.The ‘gold standard’ technique used to diagnose M. hyopneumoniae infection, bacteriological culture, is laborious and is seldom used routinely. Enzyme-linked immunosorbent assay and polymerase chain reaction detection methods, in addition to post-mortem inspection in the form of abattoir surveillance or field necropsy, are the techniques most frequently used to investigate the potential involvement of M. hyopneumoniae in porcine respiratory disease. Such techniques have been used to monitor the incidence of M. hyopneumoniae infection in herds both clinically and subclinically affected by EP, in vaccinated and non-vaccinated herds and under different production and management conditions. Differences in the clinical course of EP at farm level and in the efficacy of M. hyopneumoniae vaccination suggest that the transmission and virulence characteristics of different field isolates of M. hyopneumoniae may vary. This paper reviews the current state of knowledge of the epidemiology of M. hyopneumoniae infection including its transmission, infection and seroconversion dynamics and also compares the various epidemiological tools used to monitor EP.     

Antibiotic resistance in potentially bacteriocinogenic probiotic bacteria in aquaculture environments

Bacteriocin‐producing bacteria in aquaculture may prevent spreading of potentially pathogenic microorganisms, and could be used as an alternative to the empirical use of antimicrobial drugs, especially for prophylaxis. Bacteriocinogenic bacteria inoculated as probiotics should not carry undesirable traits, such as antibiotic resistance. This study aimed to find potentially bacteriocinogenic bacteria in an aquaculture system and evaluate their antimicrobial susceptibility patterns. Selective cultures for enterobacteria, non‐fermenting Gram‐negative rods and Gram‐positive cocci were obtained from water samples before bacterial isolation and biochemical identification. Overall, 160 representative strains were recovered and for 57 antagonism was observed against selected strains such as Staphylococcus aureus, with antagonism being expressed better on Brain Heart Infusion medium. After exclusion of interfering factors, bacteriocin or bacteriocin‐like substances were suggested to be related to the antagonism observed. Higher drug‐resistant rates were observed among potentially bacteriocinogenic bacteria for different antimicrobials of clinical relevance. Although antibiotic resistance is a global health problem and bacteriocins are attractive alternatives to classical antibiotic even to multiresistant bacteria, the data obtained suggest that bacteriocin‐producing bacteria may harbour resistance genes available for transference in different environments. From the ecological and biotechnological perspective, antimicrobial susceptibility tests must be always performed when prospecting potentially bacteriocinogenic bacteria as probiotic candidates in the environment.     

The Effects of Stressful Broodstock Handling on Hormonal Profiles and Reproductive Performance of Rhamdia quelen (Quoy & Gaimard) Females

Abstract.— A stressful environment induces cortisol that might affect fish breeding and reproduction. In the present work, which aimed to mimic aquacultural conditions of the jundia (Rhamdia quelen) hatcheries in southern South America, females were submitted to normal or stressful handling and the effects of cortisol on serum levels of 17β‐estradiol (E2) and testosterone (T) were determined. In addition, the effect of stress on reproductive parameters such as eggs and swim‐up fry production was also measured. Eight females from a group submitted to stressful handling (SH) conditions and eight females from a group with normal handling (NH) conditions were captured for blood sampling at D 0 and at D 1, 10, 20, 30, and 40 of the experiment. A typical cortisol response was observed in the SH females group in that they presented higher cortisol level in contrast to the NH female group, in all days sampled, except at D 0. In the 10th and 20th d, the E2 levels were lower in SH females, but cortisol levels were higher, suggesting an effect of cortisol on E2 production and/or release. Stressful handling appeared to affect both the number and the quality of the gametes because a lower number of oocytes was stripped from SH females, and from SH fertilized eggs, a lower number of viable swim‐up fry was obtained to be transferred to earthen larviculture ponds. Taken together, the results indicated that stressful handling of broodstock impairs R. quelen reproduction.