In vitro capsule or biofilm formation of Streptococcus uberis and bacteriological cure of bovine mastitis

Dedication

We dedicate this article to Prof. Dr. Kerstin Müller and would like to thank her for her cooperation with our working group.

Abstract

Objective The relationship between the in vitro detected virulence factors biofilm and capsule formation of Streptococcus (S.) uberis isolates of clinical mastitis in dairy cows and the bacteriological cure rate after antibiotic therapy was investigated in order to better understand the importance of these virulence factors for the bacteriological cure rate.

Material and methods A total of 111 clinical mastitis (CM) cases were collected, in which S. uberis was bacteriologically detected. All mastitis cases were treated in accordance with the approval conditions of the antibiotic udder tubes used. Individual cow information including age, number of lactations, current lactation mastitis and antimicrobial treatment received was recorded. The microtiter plate test was used to detect biofilm formation and Anthony capsule staining was used to detect capsular capacity. Statistical analyses were performed to characterize the correlation between in vitro virulence factors and bacteriological cure (BC) rate.

Results 30.5% (n=29) of the S. uberis isolates of bacteriologically cured cases and 34.5% (n=10) of the isolates of bacteriologically non-cured mastitis cases were found to have the ability to produce capsules in vitro. 70.7% (n=58) of the S. uberis isolates from bacteriologically cured mastitis cases had the ability to produce biofilm in vitro, whereas 58.6% (n=17) of the isolates of non-cured mastitis cases showed ability in producing biofilm. No correlation was found between the in vitro ability of S. uberis to form capsules and biofilms and the BC rate after antibiotic treatment of bovine mastitis.

Conclusion(s) The present work has shown that the investigated in vitro virulence factors are not associated with the BC after antibiotic therapy. Further studies on the role of S. uberis virulence factors are needed to complete the missing knowledge on the difficulties in curing S. uberis mastitis.

Clinical relevance This study is of great clinical relevance since it enhances the understanding of the occurrence of BC in S. uberis mastitis cases. The investigated virulence factors are often addressed as possible reasons for therapy failure, although respective scientific studies are missing.

Zusammenfassung

Gegenstand und Ziel Der Zusammenhang zwischen den in vitro nachgewiesenen Virulenzfaktoren Biofilm- und Kapselbildung von Streptococcus (S.) uberis-Isolaten klinischer Mastitiden bei Milchkühen und der bakteriologischen Heilungsrate nach Antibiotikatherapie wurde untersucht, um die Bedeutung dieser Virulenzfaktoren für die bakteriologische Heilungschance besser zu verstehen.

Material und Methoden Einhundertelf S. uberis-Isolate klinischer Mastitiden wurden untersucht. Die Mastitisfälle wurden gemäß den Zulassungsbedingungen für die verwendeten antibiotischen Eutertuben behandelt. Daten der Einzeltiere bezüglich Alter, Anzahl der Laktationen, Mastitisfälle in der aktuellen Laktation und erhaltene antimikrobielle Behandlungen wurden erfasst. Mittels Mikrotiterplatten-Test wurde Biofilmbildung nachgewiesen und zum Nachweis der Kapselbildung der Isolate wurde die Anthony-Kapselfärbung verwendet. In der statistischen Auswertung wurde die Korrelation zwischen in vitro-Virulenzfaktoren und der bakteriologischen Heilungsrate ausgewertet.

Ergebnisse 30,5% (n=29) der S. uberis Isolate aus geheilten Mastitisfällen und 34,5% (n=10) der S. uberis-Isolate, deren Infektionen nicht bakteriologisch geheilt werden konnten, waren in der Lage, in vitro Kapseln zu produzieren. Eine in vitro Biofilmbildung zeigten 70,7% (n=58) der Isolate aus den geheilten Fällen und 58,6% (n=17) der Isolate aus den nicht geheilten Fällen. Weder die untersuchten in vitro-Virulenzfaktoren von S. uberis noch die bekannten Einflussfaktoren auf die bakteriologische Heilung waren in dieser Untersuchung signifikant mit der bakteriologischen Heilung assoziiert.

Schlussfolgerung(en) Da die in vitro untersuchten Virulenzfaktoren nicht mit der bakteriologischen Heilung nach einer Antibiotikatherapie assoziiert sind, sind weitere Studien, die erregerspezifische und tierindividuelle Charakteristika der bakteriologischen Heilung von Mastitiden gegenüberstellen, erforderlich, um die Mechanismen der bakteriologischen Heilung besser zu verstehen. Die pauschale Benennung von Virulenzfaktoren als Ursachen von unzureichenden bakteriologischen Heilungsraten sollte vorsichtiger gehandhabt werden.

Klinische Relevanz Der Zusammenhang zwischen den untersuchten Virulenzfaktoren von S. uberis und unzureichendem Therapieerfolg klinischer Mastitiden konnte in der vorliegenden Studie nicht bestätigt werden.

Keywords

Virulence factors - clinical mastitis - antibiotic therapy - capsule staining

Schüsselwörter

Virulenzfaktoren - klinische Mastitis - antibiotische Therapie - Kapselfärbung

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