Draft Genome Sequences of Three Porcine Streptococcus suis Isolates Which Differ in Their Susceptibility to Penicillin.

The draft genome sequences of three Streptococcus suis isolates, IMT40343, IMT40201, and IMT40738, are presented here. These isolates were obtained from bronchoalveolar lavage fluid of healthy and diseased weaners from different German piglet-producing farms and differed in their susceptibility to penicillin.

Plasmid-located dfrA14 gene in Pasteurella multocida isolates from three different pig-producing farms in Germany.

Pasteurella multocida is an important respiratory tract pathogen in intensive livestock farming, especially in pigs. Antimicrobial agents are frequently used to combat infections caused by this pathogen. In a study on antimicrobial resistance among respiratory tract pathogens of pigs from 30 German pig-producing farms, P. multocida isolates (n = 9) with high minimal inhibitory concentration (MIC) values of 16/304 mg/L (n = 2), 32/608 mg/L (n = 3) or ≥64/1216 mg/L (n = 4) for trimethoprim/sulfamethoxazole (1:19) and of ≥512 mg/L (n = 9) for trimethoprim (TMP) were detected in three of these farms. The genetic relatedness of the isolates was investigated via capsule-specific PCR and macrorestriction analyses with ApaI and SmaI. Pulsed-field gel electrophoresis revealed indistinguishable restriction patterns per farm, with slight differences between the three farms. All isolates represented capsular type A. Four representative isolates, that were subjected to whole genome sequencing, shared the multi-locus sequence type (ST) 3. Their plasmids were transformed into E. coli TOP10 with subsequent selection on TMP-containing agar plates. Antimicrobial susceptibility testing and plasmid analysis of the transformants confirmed that they were resistant to sulfonamides and trimethoprim and carried only a single small plasmid. This plasmid was completely sequenced and revealed a size of 6050 bp. Sequence analyses identified the presence of a resistance gene cluster comprising the genes sul2-ΔstrA-dfrA14-ΔstrA-ΔstrB. Further analysis identified a dfrA14 gene cassette being integrated into the strA reading frame. Neither the gene dfrA14 nor this gene cluster have been detected before in P. multocida.

Antimicrobial susceptibility and genetic relatedness of respiratory tract pathogens in weaner pigs over a 12-month period.

The collaboration project VASIB aims at reducing the antibiotic consumption in pig production by integrating information from consulting expertise in clinical inspection, hygiene, epidemiology, microbiology and pharmacology. In this VASIB subproject, we investigated the antimicrobial susceptibility and relatedness of porcine respiratory tract pathogens. Bordetella bronchiseptica (n = 47), Pasteurella multocida (n = 18) and Streptococcus suis (n = 58) were obtained from weaner pigs at two farms. Antimicrobial susceptibility testing was performed by broth microdilution according to CLSI standards. Resistance genes were detected via specific PCR assays. Macrorestriction analysis was conducted to determine the relatedness of the isolates and to identify clones. The B. bronchiseptica isolates showed indistinguishable (farm 1) or two closely related XbaI-patterns (farm 2). Different SmaI-PFGE patterns of P. multocida isolates were obtained at three different time points. In contrast, PFGE analysis of S. suis indicated more than one fragment pattern per pig and time point. Isolates exhibiting indistinguishable PFGE patterns were considered to represent the same clone. This study showed that only two closely related B. bronchiseptica clones were present in both farms, which had low MICs to all antimicrobials, except to ß-lactams. Different P. multocida clones were present at the three time points. They showed overall low MIC values, with two clones being resistant and one intermediate to tetracycline. S. suis clones were resistant to tetracycline (n = 19) and/or erythromycin/clindamycin (n = 16). They harboured the tetracycline resistance genes tet(O), tet(M) or tet(L) and/or the macrolide/lincosamide/streptogramin B resistance gene erm(B). Five penicillin-resistant S. suis clones were also detected.