Biocide-Tolerant Listeria monocytogenes Isolates from German Food Production Plants Do Not Show Cross-Resistance to Clinically Relevant Antibiotics.

Contamination of food during processing is recognized as a main transmission route of Listeria monocytogenes To prevent microbial contamination, biocides are widely applied as disinfectants in food processing plants. However, there are concerns about the development of antimicrobial resistance in foodborne pathogens due to widespread biocide usage. In our study, 93 L. monocytogenes isolates from German food production facilities were (i) tested for biocide and antibiotic susceptibility using broth microdilution assays, (ii) analyzed for links between reduced biocide susceptibility and antibiotic resistance, and (iii) characterized by whole-genome sequencing, including the detection of genes coding for biocide tolerance, antibiotic resistance, and other virulence factors. Fifteen L. monocytogenes isolates were tolerant to benzalkonium chloride (BAC), and genes conferring BAC tolerance were found in 13 of them. Antibiotic resistance was not associated with biocide tolerance. BAC-tolerant isolates were assigned to 6 multilocus sequence type (MLST) clonal complexes, and most of them harbored internalin A pseudogenes with premature stop codons or deletions (n = 9). Our study demonstrated a high genetic diversity among the investigated isolates including genotypes that are frequently involved in human infections. Although in vitro adaptation studies to biocides have raised concerns about increasing cross-resistance to antibiotics, our results do not provide evidence for this phenomenon in field isolates.IMPORTANCE Foodborne pathogens such as L. monocytogenes can persist in food production environments for a long time, causing perennial outbreaks. Hence, bacterial pathogens are able to survive cleaning and disinfection procedures. Accordingly, they may be repeatedly exposed to sublethal concentrations of disinfectants, which might result in bacterial adaptation to these biocides. Furthermore, antibiotic coresistance and cross-resistance are known to evolve under biocide selection pressure in vitro Hence, antimicrobial tolerance seems to play a crucial role in the resilience and persistence of foodborne pathogens in the food chain and might reduce therapeutic options in infectious diseases.

Species differentiation within the Staphylococcus intermedius group using a refined MALDI-TOF MS database.

Among coagulase-positive staphylococci of animal origin, the members of the Staphylococcus intermedius-group (SIG: S. intermedius, Staphylococcus pseudintermedius and Staphylococcus delphini) are important opportunistic pathogens in different animal hosts and occasionally in humans. However, the unambiguous species diagnosis of SIG is often challenging. Therefore, matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) -based SIG-identification with Bruker Microflex LT in combination with Biotyper 3.0 software (Bruker Daltonics, Bremen, Germany) was evaluated using (i) the original database content and (ii) the database after extension with distinct hierarchical clustered reference spectra for 60 SIG. A convenience sample comprising 200 isolates was used to compare both database performances. As a result, 17 isolates initially diagnosed as S. intermedius with the current content of the Bruker database were identified as S. pseudintermedius by applying the in-house reference spectra extended version. Furthermore, a significant improvement (average rise of log score value: 0.24) of the SIG identification score values was achieved, emphasizing that further sequence-based refinement of the Bruker database content allows improvement of MALDI-TOF MS-based identification.

Molecular analysis of human and canine Staphylococcus aureus strains reveals distinct extended-host-spectrum genotypes independent of their methicillin resistance.

Staphylococcus aureus causes a wide range of infectious diseases in humans and various animal species. Although presumptive host-specific factors have been reported, certain genetic lineages seem to lack specific host tropism, infecting a broad range of hosts. Such Extended-Host-Spectrum Genotypes (EHSGs) have been described in canine infections, caused by common regional human methicillin-resistant S. aureus (MRSA) lineages. However, information is scarce about the occurrence of methicillin-susceptible S. aureus (MSSA) EHSGs. To gain deeper insight into EHSG MSSA and EHSG MRSA of human and canine origin, a comparative molecular study was carried out, including a convenience sample of 120 current S. aureus (70 MRSA and 50 MSSA) isolates obtained from infected dogs. spa typing revealed 48 different spa types belonging to 16 different multilocus sequence typing clonal complexes (MLST-CCs). Based on these results, we further compared a subset of canine (n = 48) and human (n = 14) strains, including isolates of clonal complexes CC5, CC22, CC8, CC398, CC15, CC45, and CC30 by macrorestriction (pulsed-field gel electrophoresis [PFGE]) and DNA-microarray analysis. None of the methods employed was able to differentiate between clusters of human and canine strains independently of their methicillin resistance. In contrast, DNA-microarray analysis revealed 79% of the 48 canine isolates as carriers of the bacteriophage-encoded human-specific immune evasion cluster (IEC). In conclusion, the high degree of similarity between human and canine S. aureus strains regardless of whether they are MRSA or MSSA envisions the existence of common genetic traits that enable these strains as EHSGs, challenging the concept of resistance-driven spillover of MRSA.

Desoxyribonuclease activity in the serum and spleen of rats with mycoplasma induced arthritis.

The endodesoxyribonuclease and exodesoxyribonuclease activities were measured in the spleen cytoplasma fraction and serum of rats with mycoplasma induced arthritis and adjuvant arthritis. A higher exonuclease activity was found in the spleen cytoplasma of adjuvant arthritis rats. During the regression of mycoplasma arthritis an increased activity of exonuclease was detected in the serum, but in the acute stage of inflammation the exonuclease activity was similar to the control values. A higher endonuclease activity was found in the spleen cytoplasma fraction of rats with mycoplasma arthritis. The possible origin of the endonuclease and its role in arthritis are discussed.