Lincoral-S® - A Unique Combination For The Treatment Of Mixed Enteric Infections And Post-Weaning Diarrhoea

Ulrich Klein

Mixed enteric infections are recognised as a significant problem in pigs worldwide. Findings from diarrhoea outbreaks in weaners and growers in commercial herds have identified that Escherichia coliLawsonia intracellularisBrachyspira pilosicoli and Brachyspira hyodysenteriae pathogens often occur concurrently in batches of affected pigs (Pedersen et al., 2015; Thomson, 2006). 

Prevalence figures of porcine enteric infection outbreaks collected from 531 pig units in the United Kingdom between 1992 and 2005 (Table 1) indicate that L. intracellularis was often identified as part of mixed infections (10 - 15% of the units). The prevalence of L. intracellularis in mixed infections was consistent over time. B. hyodysenteriae and B. pilosicoli were most often found in mixed enteric infections. This was also the case for porcine Salmonella species.

 

Table 1. Prevalence of bacterial pathogens associated with enteric outbreaks in the ileum and colon of pigs over 14 consecutive years (Thomson, 2006)

 

The increasing occurrence of mixed enteric infections has implications for selecting treatment strategies in affected pig herds. Consequently, diagnostic examination and susceptibility testing of every batch of pigs is the only appropriate way to confirm whether antibiotics should be used for enteric treatment purposes, and if so, which one.

 

Categorisation of antibiotics for use in animals

Lincomycin (Category C) and spectinomycin (Category D) are appropriate options for the first line treatment of mixed enteric infections in swine. Lincoral-S® contains a combination of lincomycin and spectinomycin (in the ratio 1:2). 

 

Lincoral-S in the era of responsible antibiotic use

The presence of bacteria that cause enteric diseases must be established before Lincoral-S is used in a herd. The molecular action of lincomycin and spectinomycin in animals is different. Lincomycin binds at the 50S ribosomal subunit and inhibits protein formation while spectinomycin binds at the 30S ribosomal subunit of the bacteria. Both antibiotics interfere with protein production of bacterial cells at different ribosomal units which provides a better understanding of the complementary activity of lincomycin and spectinomycin. 

Minimum inhibitory concentration (MIC) data indicate that the combined use of lincomycin and spectinomycin can enhance the activity of both components against L. intracellularis (Wattanaphansak et al., 2019). 

 

Table 2. Intracellular and extracellular MICs of lincomycin, spectinomycin and the combination against three Thai L. intracellularis isolates (Wattanaphansak et al., 2019)

 

Pan-European susceptibility testing of Salmonella spp. and Escherichia coli isolates indicate differences in their sensitivity pattern against lincomycin and spectinomycin (Hawser, 2022). 

 

Table 3. Lincomycin and spectinomycin MIC data of Salmonella spp. isolates (n=90; collected from BE, DE, DK, ES, NL, PL and UK)

 

Table 4. Lincomycin and spectinomycin MIC data of E. coli isolates (n=238; collected from BE, DE, DK, NL, PL and UK)

 

In the case of B. hyodysenteriae, only lincomycin was MIC tested during the Pan-European susceptibility testing (Hawser, 2022). 

 

Table 5. Lincomycin MIC data of B. hyodysenteriae isolates (n=38; collected from DE and UK)

 

In cases where E. coli, L. intracellularisB. hyodysenteriae and Salmonella spp. are present, using a combination of lincomycin and spectinomycin is useful because: 

  • there is often more than one enteric pathogen present in enteric disease situations
  • the combination of two actives provides a broad spectrum of activity
  • the different molecular actions increase the inhibition of protein formation in bacterial pathogens

 

Efficacy studies of lincomycin with spectinomycin

Studies were conducted in six farrow-to-finish pig farms (one in England, one in Spain, two in France, and two in Denmark) where diagnosis of ileitis single infection was confirmed through clinical signs, postmortem examinations and bacteria isolations from affected pigs (McOrist et al., 2000). 

In the study, pens with diarrhoeic pigs were either left unmedicated (Group 1) or medicated with lincomycin/spectinomycin in drinking water for 7 days (Group 2) or for 14 days (Group 3). Medication started on day 0 in Groups 2 and 3. The curative potential of the lincomycin/spectinomycin combination in the case of ileitis infections is shown in Figure 1.

 

Figure 1. Percentage of pigs with a normal faecal score between day 0 and day 21

 

On day 0, the percentage of pigs with a normal faecal score was 44.3% in Group 1, 51.6% in Group 2 and 51.5% in Group 3.

By day 7 (the last day of treatment for Group 2), the percentage of pigs with a normal faecal score decreased in the non-medicated group to 38.2%, whereas it increased in Group 2 (76.6%) and Group 3 (70.2%).

By day 14 (the last day of treatment for Group 3), the percentage of pigs with a normal faecal score was 44.1% in Group 1 versus 63.4% and 73.8% in Groups 2 and 3, respectively.

At the end of the study (day 21), the percentage of pigs with a normal faecal score was much higher in Group 2 (68.1%) and Group 3 (72.7%) compared to the non-medicated group (48.2%).

Treatment of pigs with lincomycin/spectinomycin resulted in clinical improvement and improvements in faecal consistency and weight gain (Table 6).

 

Table 6. Daily weight gain of pigs that were unmedicated, or medicated for 7 or 14 days

 

In the context of EU Guidelines on prudent use and the EMA categorisation of antibiotics, lincomycin/spectinomycin is the most appropriate option for the treatment of complex mixed infections post weaning.

 

References are available on request.