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Francisella tularensis is a Gram-negative bacterium, the causative agent of the zoonotic disease tularaemia. The bacterium has developed several extracellular and intracellular strategies to evade the hosts’ innate and adaptive immune responses. The aims of the study were to examine complement sensitivity of wild and attenuated F. tularensis ssp. holarctica strains in animal hosts of distinct sensitivity to the bacterium, to compare the complement-evading ability of wild strains of different phylogeographic background, and to examine the role of factor H in the host–pathogen interactions. Complement sensitivity assays were carried out on various F. tularensis ssp. holarctica wild strains and on the attenuated live vaccine strain (LVS) with sera of the highly sensitive house mouse (Mus musculus), the moderately sensitive European brown hare (Lepus europaeus) and the relatively resistant cattle (Bos taurus). Specific binding of complement regulator factor H to bacterial membrane proteins was examined by Western blot assays. All wild strains interacted with the hosts’ complement system and showed no significant differences in their survivability. The attenuated LVS was resistant to serum killing in mouse, but was lysed in the sera of hare and cattle. Direct binding of factor H to F. tularensis membrane proteins was not detected.

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Acta Veterinaria Hungarica
Authors:
Zsuzsa Kreizinger
,
Kinga Mária Sulyok
,
László Makrai
,
Zsuzsanna Rónai
,
László Fodor
,
Szilárd Jánosi
, and
Miklós Gyuranecz

The susceptibility of 29 Bacillus anthracis strains, collected in Hungary between 1933 and 2014, was tested to 10 antibiotics with commercially available minimum inhibitory concentration (MIC) test strips. All strains were susceptible to amoxicillin, ciprofloxacin, clindamycin, doxycycline, gentamicin, penicillin, rifampicin, and vancomycin. Intermediate susceptibility to erythromycin and cefotaxime was detected in 17.2% (5/29) and 58.6% (17/29) of the strains, respectively. Correlations were not observed between the isolation date, location, host species, genotype, and antibiotic susceptibility profile of strains.

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Abstract

Several Mycoplasma species can form biofilm, facilitating their survival in the environment, and shielding them from therapeutic agents. The aim of this study was to examine the biofilm-forming ability and its potential effects on environmental survival and antibiotic resistance in Mycoplasma anserisalpingitidis, the clinically and economically most important waterfowl Mycoplasma species. The biofilm-forming ability of 32 M. anserisalpingitidis strains was examined by crystal violet assay. Biofilms and planktonic cultures of the selected strains were exposed to a temperature of 50 °C (20 and 30 min), to desiccation at room temperature (16 and 24 h), or to various concentrations of eight different antibiotics. Crystal violet staining revealed great diversity in the biofilm-forming ability of the 32 tested M. anserisalpingitidis strains, with positive staining in more than half of them. Biofilms were found to be more resistant to heat and desiccation than planktonic cultures, while no correlation was shown between biofilm formation and antibiotic susceptibility. Our results indicate that M. anserisalpingitidis biofilms may contribute to the persistence of the organisms in the environment, which should be taken into account for proper management. Antibiotic susceptibility was not affected by biofilm formation; however, it is important to note that correlations were examined only in vitro.

Open access
Acta Veterinaria Hungarica
Authors:
Dorottya Földi
,
Zsuzsa Kreizinger
,
Katinka Bekő
,
Nikolett Belecz
,
Krisztián Bányai
,
Krisztián Kiss
,
Imre Biksi
, and
Miklós Gyuranecz

Abstract

The control of Mycoplasma hyorhinis infection relies mainly on antimicrobial therapy. However, the antibiotic susceptibility testing of the bacteria is usually not performed before applying the treatment, and thus therapeutic failures are not uncommon. In the case of M. hyorhinis, several antibiotic-resistance-related single nucleotide polymorphisms (SNPs) are known but assays for their detection have not been described yet. The aims of the present study were to investigate macrolide- and lincomycin-resistance-related SNPs in Hungarian M. hyorhinis isolates and to develop mismatch amplification mutation assays (MAMA) to detect the identified resistance markers. Minimal inhibitory concentrations (MIC) of different drugs and whole genome sequences of 37 M. hyorhinis isolates were used to find the resistance-related mutations. One MAMA assay was designed to detect the mutation of the 23S rRNA gene at nucleotide position 2058 (Escherichia coli numbering). For further evaluation, the assay was challenged with 17 additional isolates with available MIC data and 15 DNA samples from clinical specimens. The genotypes of the samples were in line with the MIC test results. The developed assay supports the practice of targeted antibiotic usage; hence it may indirectly reduce some bacterial resistance-related public health concerns.

Open access