Phenotypic and genetic characterisation of methicillin-resistant Staphylococcus aureus strains isolated from the university hospitals of Debrecen

Genomic Evidence for Direct Transmission of mecC-MRSA between a Horse and Its Veterinarian

Methicillin-resistant Staphylococcus aureus bearing the mecC gene (mecC-MRSA) has been reported from animals and humans in recent years. This study describes the first mecC-MRSA isolates of human and equine origin in Hungary (two isolates from horses and one from a veterinarian, who treated one of the infected horses, but was asymptomatic). MRSA isolates were identified by cultivation and PCR detection of the species-specific spa gene and mecA/mecC methicillin resistance genes. The isolates were characterized by antibiotic susceptibility testing, MLST, spa, SCCmec typing, PFGE and whole genome sequencing (WGS). All three isolates belonged to the ST130-t843-SCCmec XI genotype, and carried the mecC and blaZ genes. Apart from beta-lactam drugs, they were sensitive to all tested antibiotics. The isolates of the infected horse and its veterinarian had the same PFGE pulsotype and showed only slight differences with WGS. Hence, this is the first description of direct transmission of a mecC-carrying MRSA between a horse and its veterinarian. The emergence of mecC in the country highlights the importance of the appropriate diagnostics in MRSA identification.

Phenotypic and Molecular Detection of Biofilm Formation in Methicillin-Resistant Staphylococcus Aureus Isolated from Different Clinical Sources in Erbil City

Background

Staphylococcus aureus is an important causative pathogen. The production of biofilms is an important factor and makes these bacteria resistant to antimicrobial therapy.

Objectives

the current study aimed to assess the prevalence of resistance to antibacterial agents and to evaluate the phenotypic and genotypic characterization of biofilm formation among S. aureus strains.

Methods

This study included 50 isolates of Methicillin-resistant S. aureus (MRSA) and Methicillin-Susceptible S. aureus (MSSA). S. aureus was identified by molecular and conventional methods, and antimicrobial resistance was tested with a disc diffusion method. The biofilm formation was performed through the Microtiter plate method. Strains were subjected to PCR to determine the presence of nuc, mecA, icaA, icaB, icaC, and icaD genes.

Results

Of the 50 S. aureus isolates, 32(64%) and 18(36%) were MRSA and MSSA, respectively. A large number of MRSA and MSSA isolates showed resistance to Penicillin and Azithromycin, and a lower number of MRSA and MSSA isolates showed resistance to Amikacin Gentamicin. None of the isolates was resistant to Vancomycin. The MRSA strains had significantly higher resistance against antibiotics than MSSA strains (P = 0.0154). All isolates (MRSA and MSSA) were able to produce biofilm with levels ranging from strong (31.25 %), (16.6%) to moderate (53.12%), (50%) to weak (15.6%), (33.3%) respectively. The MRSA strains had a significantly higher biofilm formation ability than the MSSA strains (P = 0.0079). The biofilm-encoding genes were detected among isolates with different frequencies. The majority of S. aureus isolates, 42 (84%), were positive for the icaA. The prevalence rates of the icaB, icaC and icaD genes were found to be 37 (74%), 40 (80%) and 41 (82%), respectively.

Conclusions

The prevalence of biofilm encoding genes associated with multidrug resistance in S. aureus strains is high. Therefore, identifying epidemiology, molecular characteristics, and biofilm management of S. aureus infection would be helpful.

Prevalence of Staphylococcus aureus in wild hedgehogs (Erinaceus europaeus) and first report of mecC-MRSA in Hungary

In 2011 mecC, a new mecA gene homologue, was described in a bovine isolate in the UK. Since then, mecC-positive methicillin-resistant Staphylococcus aureus (mecC-MRSA) has also been found in wild animals. An especially high prevalence of mecC-MRSA has been reported among hedgehogs in Sweden (64%) and Denmark (61%). Based on these findings we aimed to survey the hedgehog population for mecC-MRSA in Hungary. Altogether 200 hedgehogs were screened for Staphylococcus aureus using a culture-based method. The antibiotic susceptibility of the isolates to nine drugs was determined, their genetic relatedness was established by PFGE and spa-typing, and virulence genes were identified by PCR. Whole genome sequencing was performed for the single mecC-MRSA isolate found. Of the 200 animals, 13 were carriers of S. aureus (6.5%). Among these, one isolate was mecA positive and one was mecC positive. The isolates were susceptible to non-beta-lactam antibiotics. Toxin genes were not found, but the majority carried genes responsible for adhesion and biofilm production. The mecC-MRSA isolate was a single-locus variant of ST130, had a new spa type (t19701) and belonged to SCCmec type XI. It carried a recently described, novel exfoliative toxin (etE). This is the first report of mecC-MRSA in Hungary and the first survey of staphylococcus carriage among wild animals in the country. The mecC prevalence was much lower than in Northern European countries and rather similar to other countries in our region. MecC-MRSA could potentially emerge as a novel human pathogen, especially where close contact occurs between humans and animals.

Whole genome sequencing of coagulase positive staphylococci from a dog-and-owner screening survey

BACKGROUND

Staphylococcus aureus and S. pseudintermedius are the two most common coagulase positive staphylococci (CPS). S. aureus is more prevalent among humans, whereas S. pseudintermedius is more commonly isolated from dogs, however, both can cause various community and hospital acquired diseases in humans.

METHODS

In the current study we screened 102 dogs and 84 owners in Hungary. We tested the antibiotic susceptibility of the strains and in order to get a better picture of the clonal relationship of the strains, we used pulsed-field gel electrophoresis. In addition, three pairs of isolates with identical PFGE patterns were whole genome sequenced, MLST and spa types were established.

RESULTS

Carriage rate of S. aureus was 23.8% in humans and 4.9% in dogs and two cases of co-carriage were found among dogs and owners. S. pseudintermedius carriage rate was 2.4% and 34.3%, respectively, with only one co-carriage. The isolates were generally rather susceptible to the tested antibiotics, but high tetracycline resistance of S. pseudintermedius strains was noted. The co-carried isolates shared almost the same resistance genes (including tet(K), bla(Z), norA, mepR, lmrS, fosB) and virulence gene pattern. Apart from the common staphylococcal enzymes and cytotoxins, we found enterotoxins and exfoliative toxins as well. The two S. aureus pairs belonged to ST45-t630, ST45-t671 and ST15-t084, ST15-t084, respectively. The co-carried S. pseudintermedius isolates shared the same housekeeping gene alleles determining a novel sequence type ST1685.

CONCLUSIONS

Based on the genomic data, dog-owner co-carried strains displayed only insignificant differences therefore provided evidence for potential human-to-dog and dog-to-human transmission.

Characterization of methicillin-resistant Staphylococcus aureus through genomics approach

In the present study, a total of 35 S. aureus isolates collected from two different geographical locations viz., Germany and Hungary were tested for their methicillin-resistant phenotype which revealed a high incidence of methicillin-resistant S. aureus. The quantitative test for biofilm production revealed that 73.3% of isolates were biofilm producers. The isolates were further characterized using a set of biochemical and genotypic methods such as amplification and analysis of S. aureus species-specific sequence and mecA gene. The 33 mecA positive isolates were then characterized by the amplification of SCCmec and pvl toxin genes. Further, based on the biofilm-forming phenotype, 15 isolates were selected and characterized through PCR–RFLP of coa gene, polymorphism of spa gene and amplification of biofilm-associated genes. The dendrogram prepared from the results of both biochemical and genotypic analyses of the 15 isolates showed that except for the isolates SA G5 and SA H29, the rest of the isolates grouped themselves according to their locations. Thus, the two isolates were selected for further characterization through whole-genome sequencing. Comparative genome analysis revealed that SA G5 and SA H29 have 97.20% ANI values with 2344 gene clusters (core-genome) of which 16 genes were related to antibiotic resistance genes and 57 genes encode virulence factors. The highest numbers of singleton genes were found in SA H29 that encodes proteins for virulence, resistance, mobile elements, and lanthionine biosynthesis. The high-resolution phylogenetic trees generated based on shared proteins and SNPs revealed a clear difference between the two strains and can be useful in distinguishing closely related genomes. The present study demonstrated that the whole-genome sequence analysis technique is required to get a better insight into the MRSA strains which would be helpful in improving diagnostic investigations in real-time to improve patient care.

Co-carriage of Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis among three different age categories of children in Hungary

Background

The nasopharynx can from time to time accommodate otherwise pathogenic bacteria. This phenomenon is called asymptomatic carriage. However, in case of decreased immunity, viral infection or any other enhancing factors, severe disease can develop. Our aim in this study was to survey the nasal carriage rates of four important respiratory pathogens in three different age groups of children attending nurseries, day-care centres and primary schools. This is the first study from Hungary about the asymptomatic carriage of H. influenzae and M. catarrhalis.

Methods

Altogether 580 asymptomatic children were screened in three Hungarian cities. Samples were collected from both nostrils with cotton swabs. The identification was based on both colony morphology and species-specific PCRs. Serotyping was performed for S. pneumoniae, H. influenzae and M. catarrhalis. Antibiotic susceptibility was determined with agar dilution, according to the EUCAST guidelines. Clonality was examined by PFGE.

Results and conclusions

Whereas the carriage rates of S. pneumoniae, H. influenzae and M. catarrhalis clearly decreased with age, that of S. aureus showed an opposite tendency. Multiple carriage was least prevalent if S. aureus was one of the participants. The negative association between this bacterium and the others was statistically significant. For pneumococcus, the overall carriage rate was lower compared to earlier years, and PCV13 serotypes were present in only 6.2% of the children. The majority of H. influenzae isolates was non-typeable and no type b was detected; serotype A was dominant among M. catarrhalis. All four bacteria were more sensitive to antibiotics compared to clinical isolates. No MRSAs were detected, but we found three mupirocin resistant strains. The positive effect of Hib- and PCV-vaccination is undoubted. Continued surveillance of these pathogens is required.

Phagocytosis and intracellular killing of heterogeneous vancomycin-intermediate Staphylococcus aureus strains

Risk factors for invasive infections by heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA) may involve resistance to opsonophagocytosis and bacterial killing. hVISA strains typically have a thickened cell wall with altered peptidoglycan cross-linking. To determine whether hVISA may be endowed with an increased resistance to phagocytosis, this study assessed the characteristics of uptake and killing by granulocytes of three hVISA strains. All isolates were analysed by multilocus sequence typing and staphylococcal chromosome cassette mec typing. One of the strains belonged to the Hungarian meticillin-resistant S. aureus (MRSA) clone ST239-MRSA-III and the other two to the New York/Japan MRSA clone ST5-MRSA-II. In the presence of 10 % normal serum, the extent of phagocytosis and killing by blood granulocytes was equivalent for hVISA, MRSA and meticillin-sensitive S. aureus (MSSA) strains. Using granulocytes and serum from one patient who survived hVISA infection, the rate of phagocytosis and killing was also found to be comparable to that by control cells in the presence of 10 % serum. However, phagocytosis and killing of hVISA and MRSA (ATCC 25923) strains by normal granulocytes was markedly decreased in the presence of low concentrations (1 and 2.5 %) of serum from the patient who survived hVISA infection compared with that found with normal human serum. These data suggest that hVISA and MRSA isolates may be more resistant to opsonophagocytosis and bacterial killing than MSSA isolates, at least in some cases.

Prevalence of vanC vancomycin-resistant enterococci in the teaching hospitals of the University of Debrecen, Hungary

Vancomycin-resistant enterococci (VRE) are common nosocomial pathogens; however, until now they have been rarely encountered in Hungary. In the present study, we investigated the prevalence of VRE in the teaching hospitals of the University of Debrecen. Of 7,271 Enterococcus-containing clinical samples collected between 2004 and 2009, we identified 16 VRE. Species-specific polymerase chain reaction was used to detect Enterococcus faecalis, Enterococcus faecium, Enterococcus casseliflavus, and Enterococcus gallinarum. Multiplex polymerase chain reaction was performed to identify the vancomycin resistance genes: vanA, vanB, vanC1/C2, vanD, vanE, and vanG. Restriction digestion with SalI and HindIII was introduced to differentiate the vanC1 and vanC2 genes from each other. Genetic relationships between the strains were investigated by pulsed-field gel electrophoresis. Overall, we identified the vanC1 resistance gene in 14 E. gallinarum and the vanC2 resistance gene in two E. casseliflavus strains. Except for two samples, the isolates had different pulsed-field gel electrophoresis types, suggesting sporadic emergence of the resistant bacteria. In addition, antibiotic resistance profile was determined by E-test. Three E. gallinarum strains proved to be resistant to gentamicin because of the presence of the aacA-aphD gene. Although the prevalence of VRE in Debrecen is rather low, the appearance of multiple resistances is of concern.

Detection of Staphylococcus aureus nasal carriage in healthy young adults from a Hungarian University

Asymptomatic carriage of Staphylococcus aureus in healthy individuals has a high prevalence, especially in children and young adults. Nasal colonisation is a well-known risk factor for subsequent severe infection, or can be the source of transmission of this bacterium to other susceptible persons. In this study, we have surveyed the nasal carriage rate of students of the Semmelweis University, by screening 300 volunteers. We have determined the antibiotic sensitivity of the isolates by Etest, and their genetic relatedness by pulsed-fieled gel electrophoresis. The nasal carriage rate of S. aureus was found to be 29.3%, and that of MRSA only 0.67% (2/300). The isolates were generally sensitive to antibiotics, except for macrolides. We could observe a noticeably great genetic diversity, even among strains deriving from students of the same university group.