Phenotypic Stability of Staphylococcus Aureus Small Colony Variants (SCV) Isolates from Cystic Fibrosis (CF) Patients.

One of the most interesting features of Staphylococcus aureus is its ability to switch to a small colony variant (SCV). This switch allows the pathogen to survive periods of antibiotic treatment or pressure from the immune system of the host and further enables it to start the infection once again after the environmental stress declines. However, so far only little is known about this reversion back to the more virulent wild type phenotype. Therefore, this study aimed to analyze the frequency of reversion to the wild type phenotype of thymidine auxotroph S. aureus SCV isolates (TD-SCVs) obtained from patients with cystic fibrosis (CF). With the use of single cell starting cultures, the occurrence of the thymidine prototroph revertants was monitored. The underlying mutational cause of the SCVs and subsequent revertants were analyzed by sequencing the gene coding for thymidylate synthase (ThyA), whose mutations are known to produce thymidine auxotroph S. aureus SCV. In our study, the underlying mutational cause for the switch to the TD-SCV phenotype was primarily point mutations. Out of twelve isolates, seven isolates showed an occurrence of revertants with a frequency ranging from 90.06% to 0.16%. This high variability in the frequency of reversion to the wild type was not expected. However, this variability in the frequency of reversion may also be the key to successful re-infection of the host. Sometimes quick reversion to the wild type proves necessary for survival, whereas other times, staying hidden for a bit longer leads to success in re-colonization of the host.

Proteus mirabilis harboring carbapenemase NDM-5 and ESBL VEB-6 detected in Austria.

We describe a case of carbapenemase-harboring Proteus mirabilis together with detection of NDM-5 in Austria accompanied by other bacterial strains with a wide range of beta-lactamases including OXA-181 and VEB-6. Isolates were obtained from a subphrenic abscess from one patient who was previously treated with broad-spectrum antibiotics in Bangladesh.

Analysis and Characterization of Staphylococcus aureus Small Colony Variants Isolated From Cystic Fibrosis Patients in Austria.

Cystic fibrosis (CF) is the most common hereditary lung disease in the Caucasian population, characterized by viscous bronchial secretion, consecutive defective mucociliary clearance, and unavoidable colonization with microorganisms. Besides Pseudomonas aeruginosa, Staphylococcus aureus is the most common bacterial species colonizing the CF respiratory tract. Under antibiotic pressure S. aureus is able to switch to small colony variants (SCV). These small colony variants can invade epithelial cells, overcome antibiotic therapy inside the cells and can be the starting point for extracellular recolonization. The aim of the present study was the isolation and characterization of S. aureus small colony variants from Austrian cystic fibrosis patients. Samples collected from 147 patients were screened for the presence of S. aureus wild-type and small colony variants. Antibiotic susceptibility testing and determination of the small colony variants causing auxotrophism were performed. Wild-type isolates were assigned to corresponding small colony variants with spa typing. In total, 17 different small colony variant isolates and 12 corresponding wild-type isolates were obtained. 13 isolates were determined thymidine auxotroph, 2 isolates were auxotroph for hemin, and none of the tested isolates was auxotroph for both, respectively. The presence of SCVs is directly related to a poor clinical outcome, therefore a monitoring of SCV prevalence is recommended. This study revealed rather low SCV ratios in CF patients compared to other countries.

Prevalence of emm types and antimicrobial susceptibility of Streptococcus dysgalactiae subsp. equisimilis in Austria.

OBJECTIVES: An increase of severe infections caused by Streptococcus dysgalactiae subsp. equisimilis (SDSE) similar to infections caused by Streptococcus pyogenes has been reported over the last years. Little is known about infections with SDSE in Austria. Therefore, we investigated a collection of 113 SDSE invasive and non-invasive isolates from different infection sites and type of infections as well as patients' characteristics. METHODS: The isolates were phenotypically identified and emm typed using the enlarged emm database from the Centers for Disease Control and Prevention. Additionally, 13 antimicrobial agents were tested using EUCAST guidelines and virulence genes were investigated. RESULTS: Severe SDSE infections were most common in elderly men with underlying diseases especially diabetes mellitus. With VitekMS identification of SDSE isolates was successful to the species level only. Emm typing revealed 24 different emm types, one new type and one new subtype. StG485, stG6, stC74a, stG643, and stG480 were the predominant types in this study, stC74a and stG652 in invasive infections and stG643, stC74a and stG485 in non-invasive infections. Resistance was observed to tetracycline (62%), macrolides (13%) with one M phenotype, and clindamycin (12%) presenting 6 constitutive MLS(B) phenotypes and 8 inducible MLS(B) phenotypes. Levofloxacin resistance was detected only in one isolate. All isolates tested for virulence genes were positive for scpA, ska, saga and slo. Superantigenic genes were negative except speG(dys) (positive 17/34; 50%). CONCLUSION: This paper presents the first report of SDSE infections in Austria. Severe SDSE infections were found mainly in elderly men with underlying diseases. SDSE isolates demonstrated substantial emm type diversity without association with infections site or invasiveness. Analysis of virulence genes showed no significant difference between invasive and non-invasive infections.

Genetic and Phenotypic Characteristics of Staphylococcus aureus Isolates from Cystic Fibrosis Patients in Austria.

BACKGROUND: Cystic fibrosis (CF) is the most common life-limiting inherited disease in Caucasian populations. While pathological changes can be seen in various organs, morbidity and mortality are mainly related to the respiratory tract, with patients suffering from chronic bronchopulmonary infections with characteristic pathogens including Staphylococcus aureus. OBJECTIVES: To date, there is only very limited data on the genetic and phenotypic characteristics of S. aureus in CF patients. Therefore, in our study, we characterized 58 S. aureus isolates collected from CF patients in Austria by spa typing, DNA microarray profiling, as well as antimicrobial susceptibility testing in order to determine common genomic and antimicrobial resistance features. The tested strain collection exhibited high genomic diversity. RESULTS: The 58 isolates were assigned to 16 clonal complexes and 48 spa types and differed greatly regarding their virulence and resistance gene profiles. The predominant clonal complexes were MLST CC30 (22%), CC15 (16%), CC45 (14%), and CC5 (12%), complexes that are highly prevalent worldwide among S. aureus strains isolated from humans colonized or infected with S. aureus. DNA microarray profiles showed a wide variety of genes encoding antimicrobial resistance and virulence factors such as various leukocidins, haemolysins, enterotoxins, exfoliative toxins, toxic shock syndrome toxin, as well as genes involved in adhesion and immune evasion. CONCLUSIONS: While a large number of strains exhibited resistance to one or several antimicrobial agents, methicillin-resistant S. aureus was found at a low prevalence of 3% (n = 2) only. The two methicillin-resistant S. aureus isolates were assigned to CC152/t355 (SCCmecV) and CC5/t001 (SCCmecI). This is the first study to genetically characterize S. aureus isolates in CF patients in Austria.

Modified culture method detects a high diversity of fungal species in cystic fibrosis patients.

Cystic fibrosis (CF) is one of the most common genetic lung diseases worldwide. The production of sticky viscous mucus leads to enhanced bacterial colonization and infection, but yeasts and filamentous fungi are also found abundantly in the mucus of patients suffering from CF. The role of fungi in the airways of CF patients is still not understood completely. Furthermore, recent investigations have shown that the spectrum of fungi isolated from the airways of CF patients depends strongly on the methods used. In this study, different mycological culture methods were compared: culture with a native inoculum, culture with homogenization of CF sputum, and culture after homogenization and serial dilutions of CF sputum. Altogether, 934 sputum samples from 113 patients were examined from July 2009 through December 2011. A total of 1,744 fungal isolates was recovered; 20 different yeasts and 14 filamentous fungal species were identified. Candida albicans, C. dubliniensis, and C. parapsilosis were the most common species of yeast. For the filamentous fungi, Aspergillus fumigatus was the most common, followed by Scedosporium apiospermum/Pseudallescheria boydii group and A. terreus. Many fungal, species such as Exophiala dermatitidis, Rasamsonia (Geosmithia) argillacea, and others, were isolated only from homogenized sputum samples. The longitudinal data also show that fungal colonization of CF patients is quite stable, even when treated with itraconazole. In conclusion, we recommend homogenizing CF sputa with a mucolyticum, to prepare serial dilutions, and to use appropriate fungal culture media with added antibiotics.

Fecal carriage and intrafamilial spread of extended-spectrum ß-lactamase-producing enterobacteriaceae following colonization at the neonatal ICU.

OBJECTIVE: Fecal carriage of extended-spectrum ß-lactamase-producing enterobacteriaceae may contribute to the spread of extended-spectrum ß-lactamase-producing enterobacteriaceae into the community. The objective of this study was to assess the duration of fecal carriage after discharge and the occurrence of intrafamilial transmission. DESIGN: Case series. SETTING: Quaternary care children's hospital. PATIENTS: Patients colonized with extended-spectrum ß-lactamase-producing enterobacteriaceae at the neonatal ICU and the respective household members. INTERVENTIONS: Screening for intestinal extended-spectrum ß-lactamase-producing enterobacteriaceae colonization was done at 1, 2, 4, 6, 9, and 12 months after discharge. Genetic relatedness of isolated extended-spectrum ß-lactamase-producing enterobacteriaceae strains was determined using automated rep-PCR. RESULTS: Twenty-five neonates (case-patients) colonized with extended-spectrum ß-lactamase-producing enterobacteriaceae (one extended-spectrum ß-lactamase-Escherichia coli; six extended-spectrum ß-lactamase-Klebsiella pneumoniae; 11 extended-spectrum ß-lactamase-Klebsiella oxytoca; and seven extended-spectrum ß-lactamase-Serratia marcescens) were included. Duration of fecal carriage was longer (up to 1 yr) in case-patients colonized with Klebsiella species than in case-patients colonized with Serratia marcescens (<4 months). During follow-up, strains and species of extended-spectrum ß-lactamase-producing enterobacteriaceae different from the primary strain were found in four and three case-patients, respectively. In nine of 49 (18.4%) included household members, extended-spectrum ß-lactamase-producing enterobacteriaceae were found during the follow-up period. In two of nine colonized household members, the isolated extended-spectrum ß-lactamase-producing enterobacteriaceae was identical to the primary strains of the respective case-patients. CONCLUSIONS: After intestinal colonization with extended-spectrum ß-lactamase-producing enterobacteriaceae at the neonatal ICU, infants potentially remain carriers during the first year after discharge. Intrafamilial spread has been proven.

Molecular epidemiology of Pseudomonas aeruginosa in cystic fibrosis patients from Southeast Austria.

Pseudomonas aeruginosa is the major pathogen in the cystic fibrosis (CF) lung, the predominant source of its acquisition, however, is under discussion. In order to study the molecular epidemiology, we evaluated 86 P. aeruginosa isolates from 43 CF patients from southeast Austria. The DiversiLab system was used to identify genetic relationships among the isolates. Antibiotic susceptibilities were tested with a broth microdilution method (Micronaut Merlin). A total of 39 unrelated P. aeruginosa genotypes were found of which 34 were unique to a single patient and one was unique to a sibling pair. We found low rates of resistance for ß-lactams with resistance to piperacillin/tazobactam and ceftazidime ranging from 4 to 6%. Resistance rates for meropenem and ciprofloxacin were 11% and 15%, respectively. The prevalence of multidrug-resistant isolates was 2%. We conclude that the majority of P. aeruginosa isolates from CF patients originate from environmental sources and patient-to-patient spread is very uncommon in our centre.