Barbara C Kahl

Publications of Barbara C Kahl

• Comparative in vitro activity of finafloxacin against staphylococci displaying normal and small colony variant phenotypes.

  Authors: Evgeny A Idelevich, André Kriegeskorte, William Stubbings, Barbara C Kahl, Georg Peters, Karsten Becker

  The Journal of antimicrobial chemotherapy. 09/2011; 66(12):2809-13.

  Staphylococcal small colony variants (SCVs) are associated with chronic and relapsing infections and their intracellular location may shield them from host defences and antibiotics. Finafloxacin is aStaphylococcal small colony variants (SCVs) are associated with chronic and relapsing infections and their intracellular location may shield them from host defences and antibiotics. Finafloxacin is a novel fluoroquinolone that exhibits optimal activity at slightly acidic conditions where the activity of other marketed fluoroquinolones decreases. Here, the in vitro activity of finafloxacin against clinical strain pairs consisting of an SCV and its clonally identical parental strain displaying the normal phenotype (NP) was compared with those of other fluoroquinolones at standard and low pH. In vitro activities of finafloxacin, ciprofloxacin, levofloxacin and moxifloxacin were tested against 28 methicillin-susceptible Staphylococcus aureus (MSSA) and three methicillin-resistant S. aureus (MRSA) SCV-NP strain pairs. Additionally, two S. aureus mutants (ΔhemB and ΔthyA) displaying the SCV phenotype and their wild-type strains as well as four SCV-NP pairs of coagulase-negative staphylococcal (CoNS) strains were included. MIC(50,) MIC(90) and MIC ranges were calculated based on MIC determination by Etest(®) at pH 5.8 and pH 7.2. Under acidic conditions, finafloxacin demonstrated superior activity against MSSA, MRSA and CoNS regardless of the phenotype. At neutral conditions, the activity against MSSA was as follows: moxifloxacin > finafloxacin > levofloxacin > ciprofloxacin. In comparison with methicillin-susceptible NP isolates, ciprofloxacin was less active against their corresponding SCVs. For other fluoroquinolones, there was no marked difference in activity against SCVs compared with NPs. Particularly in acidic body compartments, finafloxacin appears to be a promising new antibiotic for the treatment of persistent staphylococcal infections, including those caused by SCVs.

• Impact of Staphylococcus aureus on the pathogenesis of chronic cystic fibrosis lung disease.

  Authors: Barbara C Kahl

  International journal of medical microbiology : IJMM. 12/2010; 300(8):514-9.

  One of the first pathogens which can be isolated from the airways of cystic fibrosis (CF) patients is Staphylococcus aureus, which often persists in this hostile environment for many months or evenOne of the first pathogens which can be isolated from the airways of cystic fibrosis (CF) patients is Staphylococcus aureus, which often persists in this hostile environment for many months or even years. The increase in infections due to the methicillin-resistant S. aureus (MRSA) worldwide and even more the emergence of community-acquired MRSA, which differ from nosocomial MRSA by lack of multiresistance and carriage of a phage-encoded toxin, Panton-Valentine leukocidin, attracts new attention to the epidemiology, pathogenesis, and impact of S. aureus in the background of CF. In this review, recent data and studies will be reported and discussed to give an overview of the latest research.

• Staphylococcus aureus panton-valentine leukocidin is a very potent cytotoxic factor for human neutrophils.

  Authors: Bettina Löffler, Muzaffar Hussain, Matthias Grundmeier, Michaela Brück, Dirk Holzinger, Georg Varga, Johannes Roth, Barbara C Kahl, Richard A Proctor, Georg Peters

  PLoS pathogens. 01/2010; 6(1):e1000715.

  The role of the pore-forming Staphylococcus aureus toxin Panton-Valentine leukocidin (PVL) in severe necrotizing diseases is debated due to conflicting data from epidemiological studies ofThe role of the pore-forming Staphylococcus aureus toxin Panton-Valentine leukocidin (PVL) in severe necrotizing diseases is debated due to conflicting data from epidemiological studies of community-associated methicillin-resistant S. aureus (CA-MRSA) infections and various murine disease-models. In this study, we used neutrophils isolated from different species to evaluate the cytotoxic effect of PVL in comparison to other staphylococcal cytolytic components. Furthermore, to study the impact of PVL we expressed it heterologously in a non-virulent staphylococcal species and examined pvl-positive and pvl-negative clinical isolates as well as the strain USA300 and its pvl-negative mutant. We demonstrate that PVL induces rapid activation and cell death in human and rabbit neutrophils, but not in murine or simian cells. By contrast, the phenol-soluble modulins (PSMs), a newly identified group of cytolytic staphylococcal components, lack species-specificity. In general, after phagocytosis of bacteria different pvl-positive and pvl-negative staphylococcal strains, expressing a variety of other virulence factors (such as surface proteins), induced cell death in neutrophils, which is most likely associated with the physiological clearing function of these cells. However, the release of PVL by staphylococcal strains caused rapid and premature cell death, which is different from the physiological (and programmed) cell death of neutrophils following phagocytosis and degradation of virulent bacteria. Taken together, our results question the value of infection-models in mice and non-human primates to elucidate the impact of PVL. Our data clearly demonstrate that PVL acts differentially on neutrophils of various species and suggests that PVL has an important cytotoxic role in human neutrophils, which has major implications for the pathogenesis of CA-MRSA infections.

• Non-spa typable clinical Staphylococcus aureus strains are natural occuring protein A mutants.

  Authors: Cathrin Baum, Bettina Haslinger-Löffler, Henrik Westh, Kit Boye, Georg Peters, Claudia Neumann, Barbara C Kahl

  Journal of clinical microbiology. 09/2009;

  Staphylococcus aureus is a major human pathogen responsible for increasing community and hospital acquired infections. Protein A (SpA) is a key virulence factor of S. aureus, which is highlyStaphylococcus aureus is a major human pathogen responsible for increasing community and hospital acquired infections. Protein A (SpA) is a key virulence factor of S. aureus, which is highly conserved. Sequencing of the VNTR region of SpA, spa typing, provides a rapid and reliable method for epidemiological studies. Rarely, non-spa typable S. aureus strains are encountered. The reason for this is not known. In this study, we characterized eight non-spa typable bacteremia isolates. Sequencing of the entire spa locus was successful for five strains and revealed various mutations of spa, all of which included a deletion of the IgG binding domain C, in which the upper primer for spa typing is located, while two strains were truly spa-negative. This is the first report which demonstrates that non typability of S. aureus by spa sequencing is due to either mutation or true deficiency of spa.

• Characterization of clinical Enterococcus faecalis Small Colony Variants.

  Authors: Nele Wellinghausen, Indranil Chatterjee, Anja Berger, Andrea Niederfuehr, Richard A Proctor, Barbara C Kahl

  Journal of clinical microbiology. 08/2009;

  In this report, we present a clinical case of a chronic aortic valve endocarditis caused by Enterococcus faecalis small colony variants (SCVs) with ensuing characterization of the SCV phenotype inIn this report, we present a clinical case of a chronic aortic valve endocarditis caused by Enterococcus faecalis small colony variants (SCVs) with ensuing characterization of the SCV phenotype in comparison to the clonally related normal phenotype with respect to alterations in microscopic and ultrastructural morphology, growth behaviour, and metabolic pathways. In contrast to the normal phenotype, light and electron microscopy of the Enterococcus SCVs demonstrated the presence of heterogeneous cells of different sizes with aberrant shapes. Furthermore, SCVs showed an excessive production of an intercellular substance and alterations in cell division displayed by a thick, coarse cell wall and incomplete, branched and multiple cross walls without obvious cell separation. In addition, empty "ghost" cells were visible. In growth experiments, SCVs displayed an extended lag phase with delayed entrance into the stationary phase. Interestingly, SCV cells growing under aerobic conditions did not attain the growth and viability of the normal phenotype nor of the SCVs growing under microaerobic conditions, suggesting impaired growth behaviour and enhanced susceptibility in the presence of oxygen. By metabolite analysis, SCVs failed to produce significant amounts of acetate or lactate under aerobic growth conditions but were able to produce lactate under microaerobic growth conditions, implicating the induction of a fermentative metabolism. In conclusion, the observed structural alterations and changes in the cellular growth and metabolic pathways facilitated the survival of Enterococcus SCVs under microaerobic conditions in vitro and thus presumably in vivo during endocarditis.

• The thymidine-dependent small-colony-variant phenotype is associated with hypermutability and antibiotic resistance in clinical Staphylococcus aureus isolates.

  Authors: Silke Besier, Johannes Zander, Barbara C Kahl, Peter Kraiczy, Volker Brade, Thomas A Wichelhaus

  Antimicrobial agents and chemotherapy. 07/2008; 52(6):2183-9.

  Thymidine-dependent small-colony variants (TD-SCVs) of Staphylococcus aureus can be isolated from the airway secretions of patients suffering from cystic fibrosis (CF) and are implicated inThymidine-dependent small-colony variants (TD-SCVs) of Staphylococcus aureus can be isolated from the airway secretions of patients suffering from cystic fibrosis (CF) and are implicated in persistent and treatment-resistant infections. These characteristics, as well as the variety of mutations in the thymidylate synthase-encoding thyA gene which are responsible for thymidine dependency, suggest that these morphological variants are hypermutable. To prove this hypothesis, we analyzed the mutator phenotype of different S. aureus phenotypes, in particular CF-derived TD-SCVs, CF-derived isolates with a normal phenotype (NCVs), and non-CF NCVs. The comparative analysis revealed that the CF isolates had significantly higher mutation rates than the non-CF isolates. The TD-SCVs, in turn, harbored significantly more strong hypermutators (mutation rate > or = 10(-7)) than the CF and non-CF NCVs. In addition, antimicrobial resistance to non-beta-lactam antibiotics, including gentamicin, ciprofloxacin, erythromycin, fosfomycin, and rifampin, was significantly more prevalent in TD-SCVs than in CF and non-CF NCVs. Interestingly, macrolide resistance, which is usually mediated by mobile genetic elements, was conferred in half of the macrolide-resistant TD-SCVs by the point mutation A2058G or A2058T in the genes encoding the 23S rRNA. Sequence analysis of mutS and mutL, which are involved in DNA mismatch repair in gram-positive bacteria, revealed that in hypermutable CF isolates and especially in TD-SCVs, mutL was often truncated due to frameshift mutations. In conclusion, these data provide direct evidence that TD-SCVs are hypermutators. This hypermutability apparently favors the acquisition of antibiotic resistance and facilitates bacterial adaptation during long-term persistence.

• In vivo mutations of thymidylate synthase (encoded by thyA) are responsible for thymidine dependency in clinical small-colony variants of Staphylococcus aureus.

  Authors: Indranil Chatterjee, Andre Kriegeskorte, Andreas Fischer, Susanne Deiwick, Nadine Theimann, Richard A Proctor, Georg Peters, Mathias Herrmann, Barbara C Kahl

  Journal of bacteriology. 03/2008; 190(3):834-42.

  Trimethoprim-sulfamethoxazole (SXT)-resistant Staphylococcus aureus thymidine-dependent small-colony variants (TD-SCVs) are frequently isolated from the airways of cystic fibrosis (CF) patients,Trimethoprim-sulfamethoxazole (SXT)-resistant Staphylococcus aureus thymidine-dependent small-colony variants (TD-SCVs) are frequently isolated from the airways of cystic fibrosis (CF) patients, often in combination with isogenic normal strains if patients were treated with SXT for extended periods. As SXT inhibits the synthesis of tetrahydrofolic acid, which acts as a cofactor for thymidylate synthase (thyA), the survival of TD-SCVs depends exclusively on the availability of external thymidine. Since the underlying mechanism for thymidine dependency is unknown, we investigated if alterations in the thyA nucleotide sequences were responsible for this phenomenon. Sequence analysis of several clinical TD-SCVs and their isogenic normal strains with reference to previously published S. aureus thyA nucleotide sequences was performed. Three clinical TD-SCVs were complemented by transforming TD-SCVs with the vector pCX19 expressing ThyA from S. aureus 8325-4. Transcriptional analysis of metabolic and virulence genes and regulators (agr, hla, spa, citB, thyA, and nupC) was performed by quantitative reverse transcription-PCR. The previously published sequences of thyA and two normal clinical strains were highly conserved, while thyA of four normal strains and four SCVs had nonsynonymous point mutations. In 8/10 SCVs, deletions occurred, resulting in stop codons which were located in 4/10 SCVs close to or within the active site of the protein (dUMP binding). Complementation of TD-SCVs with thyA almost fully reversed the phenotype, growth characteristics, and transcription patterns. In conclusion, we demonstrated that mutations of the thyA gene were responsible for the phenotype of TD-SCVs. Complementation of TD-SCVs with thyA revealed that a functional ThyA protein is necessary and sufficient to change the SCV phenotype and behavior back to normal.

• High phenotypic diversity in infecting but not in colonizing Staphylococcus aureus populations.

  Authors: Christiane Goerke, Matthias Gressinger, Kathrin Endler, Claudia Breitkopf, Katrin Wardecki, Martin Stern, Christiane Wolz, Barbara C Kahl

  Environmental microbiology. 01/2008; 9(12):3134-42.

  In hostile environments diversity within a bacterial population may be beneficial for the fitness of the microbial community as a whole. Here we analysed the population diversity of StaphylococcusIn hostile environments diversity within a bacterial population may be beneficial for the fitness of the microbial community as a whole. Here we analysed the population diversity of Staphylococcus aureus in infecting and colonizing situations. In the study, performed independently in two German centres, the heterogeneity of the S. aureus population was determined by quantifying the occurrence of phenotypic variants (differences in haemolysis, pigmentation, colony morphology) in primary cultures from nose, oropharyngeal and sputum specimens from cystic fibrosis (CF) patients and in nose swabs from healthy S. aureus carriers. The proportion of heterogeneous samples, the number of clearly distinguishable isolates per sample and the qualitative differences between phenotypes was significantly higher in CF sputum specimens than in the other samples. The heterogeneity of the S. aureus population could be correlated with high bacterial densities in the sputum samples. In patients co-infected with Pseudomonas aeruginosa lower S. aureus bacterial loads and less heterogeneity in the S. aureus population were observed. Typing of all S. aureus isolates from heterogeneous samples by pulsed-field gel electrophoresis or spa typing revealed that the bacteria were polyclonal in 30%, monoclonal with minor genetic alterations in 25% or not distinguishable in 69% of the specimens. Some specimens harboured monoclonal and polyclonal variants simultaneously. Importantly, differences in antibiotic susceptibility were detected in phenotypic S. aureus variants within a single specimen. Diversification of a S. aureus population is highly favoured during chronic CF lung infection, supporting the general hypothesis that maintenance of intrahost diversity can be of adaptive value, increasing the fitness of the bacterial community.

• Nasal Staphylococcus aureus carriage is not a risk factor for lower-airway infection in young cystic fibrosis patients.

  Authors: Sabine Ridder-Schaphorn, Felix Ratjen, Angelika Dübbers, Johannes Häberle, Sabine Falk, Peter Küster, Antje Schuster, Uwe Mellies, Brigitte Löwe, Ralf Reintjes, Georg Peters, Barbara C Kahl

  Journal of clinical microbiology. 10/2007; 45(9):2979-84.

  Staphylococcus aureus is one of the first pathogens which often persistently infect the airways of cystic fibrosis (CF) patients. Nasal S. aureus carriage is a risk factor for S. aureus infections inStaphylococcus aureus is one of the first pathogens which often persistently infect the airways of cystic fibrosis (CF) patients. Nasal S. aureus carriage is a risk factor for S. aureus infections in non-CF patients. Topical treatment strategies successfully eradicate nasal S. aureus carriage, thereby decreasing S. aureus infection. A prospective longitudinal multicenter study was conducted to assess whether nasal carriage represents a risk factor for S. aureus colonization of the oropharynx in young CF patients. Cross-sectional analysis revealed a significantly higher prevalence of S. aureus-positive nasal (28/80 [35%] versus 20/109 [18%]; P < 0.01) and oropharyngeal (35/80 [44%] versus 20/109 [18%]; P < 0.001) cultures in children with CF compared to a control group. The first site of S. aureus detection was the nose in 6 patients and the oropharynx in 14 patients, respectively. Longitudinal analysis demonstrated a significantly higher S. aureus prevalence (61/62 [98%] versus 47/62 [76%]; P < 0.001) and persistence (46/62 [74%] versus 31/62 [50%]; P < 0.01) in the oropharynx than in the nose. In CF patients, the oropharynx, and not the nose, was the predominant site of S. aureus infection and persistence. Hence, it is unlikely that CF patients will benefit from topical treatment strategies to eradicate nasal carriage.

• Enhanced post-stationary-phase survival of a clinical thymidine-dependent small-colony variant of Staphylococcus aureus results from lack of a functional tricarboxylic acid cycle.

  Authors: Indranil Chatterjee, Mathias Herrmann, Richard A Proctor, Georg Peters, Barbara C Kahl

  Journal of bacteriology. 05/2007; 189(7):2936-40.

  The mechanisms underlying the persistence of the Staphylococcus aureus small-colony variant (SCV) are not fully elucidated. In this study, clinical thymidine-dependent SCVs displayed alteredThe mechanisms underlying the persistence of the Staphylococcus aureus small-colony variant (SCV) are not fully elucidated. In this study, clinical thymidine-dependent SCVs displayed altered expression of citB, clpC, and arcA genes, reduced acetate catabolization, and enhanced survival. These results implicate the importance of changes in tricarboxylic acid cycle and acetic acid metabolism in SCV survival and persistence.

• Microbiology. Mayhem in the lung.

  Authors: Barbara C Kahl, Georg Peters

  Science (New York, N.Y.). 03/2007; 315(5815):1082-3.

• Small colony variants: a pathogenic form of bacteria that facilitates persistent and recurrent infections.

  Authors: Richard A Proctor, Christof von Eiff, Barbara C Kahl, Karsten Becker, Peter McNamara, Mathias Herrmann, Georg Peters

  Nature reviews. Microbiology. 05/2006; 4(4):295-305.

  Small colony variants constitute a slow-growing subpopulation of bacteria with distinctive phenotypic and pathogenic traits. Phenotypically, small colony variants have a slow growth rate, atypicalSmall colony variants constitute a slow-growing subpopulation of bacteria with distinctive phenotypic and pathogenic traits. Phenotypically, small colony variants have a slow growth rate, atypical colony morphology and unusual biochemical characteristics, making them a challenge for clinical microbiologists to identify. Clinically, small colony variants are better able to persist in mammalian cells and are less susceptible to antibiotics than their wild-type counterparts, and can cause latent or recurrent infections on emergence from the protective environment of the host cell. This Review covers the phenotypic, genetic and clinical picture associated with small colony variants, with an emphasis on staphylococci, for which the greatest amount of information is available.

• Staphylococcus aureus small colony variants are resistant to the antimicrobial peptide lactoferricin B.

  Authors: Orjan Samuelsen, Hanne Husom Haukland, Barbara C Kahl, Christof von Eiff, Richard A Proctor, Hilde Ulvatne, Kjersti Sandvik, Lars H Vorland

  The Journal of antimicrobial chemotherapy. 12/2005; 56(6):1126-9.

  OBJECTIVES: To determine whether Staphylococcus aureus small colony variants (SCVs) are resistant to the antimicrobial peptide lactoferricin B. To assess if deficiency in transmembrane potential, aOBJECTIVES: To determine whether Staphylococcus aureus small colony variants (SCVs) are resistant to the antimicrobial peptide lactoferricin B. To assess if deficiency in transmembrane potential, a common characteristic of SCVs that are haemin- or menadione-auxotrophs, affects the uptake of the peptide into the bacterial cytoplasm. METHODS: A broth microdilution technique was used for susceptibility testing to determine the MIC of lactoferricin B for SCVs with three different auxotrophisms (haemin, menadione or thymidine) and their isogenic parent strains. Both clinical isolates and genetically defined mutants were used. The internalization of lactoferricin B in a hemB mutant and the respective parent strain was studied using transmission electron microscopy and immunogold labelling. RESULTS: All SCVs showed reduced susceptibility to lactoferricin B irrespective of their auxotrophy compared with their isogenic parent strains. The MIC for all SCVs was >256 mg/L, whereas the MICs for the parent strains ranged from 16-256 mg/L. Surprisingly, the hemB mutant contained significantly more lactoferricin B intracellularly than the respective parent strain. CONCLUSIONS: The resistance mechanism of SCVs towards the antimicrobial peptide lactoferricin B is presumably caused by the metabolic changes present in SCVs rather than by a changed transmembrane potential of SCVs or reduced uptake of the peptide.

• Multiple virulence factors are required for Staphylococcus aureus-induced apoptosis in endothelial cells.

  Authors: Bettina Haslinger-Löffler, Barbara C Kahl, Matthias Grundmeier, Katrin Strangfeld, Britta Wagner, Ute Fischer, Ambrose L Cheung, Georg Peters, Klaus Schulze-Osthoff, Bhanu Sinha

  Cellular microbiology. 09/2005; 7(8):1087-97.

  Staphylococcus aureus infections can result in sepsis and septic shock associated with vascular damage and multiple organ failure. Apoptosis appears to play a key role during sepsis, and the abilityStaphylococcus aureus infections can result in sepsis and septic shock associated with vascular damage and multiple organ failure. Apoptosis appears to play a key role during sepsis, and the ability of S. aureus to induce apoptosis in endothelial cells might contribute to metastatic infection. In contrast to leukocytes, in human umbilical vein endothelial cells and two endothelial cell lines neither purified alpha-toxin nor staphylococcal supernatants were sufficient to induce apoptosis. Apoptosis induction instead required staphylococcal invasion as well as signals from metabolically active intracellular staphylococci. Only strongly haemolytic and invasive staphylococci, but not non-invasive strains induced apoptosis that was caspase-dependent but Fas-independent. However, only a subgroup of clinical isolates with an invasive and haemolytic phenotype induced apoptosis. Expression of alpha-toxin in a non-haemolytic strain partially restored apoptosis induction, suggesting a role of alpha-toxin as a trigger of apoptosis. Furthermore, infection of endothelial cells with isogenic mutants of various regulator genes revealed that apoptosis induction was dependent on the global regulator agr and the alternative sigma factor sigB, but not influenced by sarA. Together, our results indicate that the ability of S. aureus to induce apoptosis in endothelial cells is determined by multiple virulence factors.

• Thymidine-dependent Staphylococcus aureus small-colony variants are associated with extensive alterations in regulator and virulence gene expression profiles.

  Authors: Barbara C Kahl, Gunnar Belling, Petra Becker, Indranil Chatterjee, Katrin Wardecki, Karin Hilgert, Ambrose L Cheung, Georg Peters, Mathias Herrmann

  Infection and immunity. 08/2005; 73(7):4119-26.

  Chronic airway infection is a hallmark of cystic fibrosis (CF) and many CF patients are infected persistently by Staphylococcus aureus. Thymidine-dependent trimethoprim-sulfamethoxazoleChronic airway infection is a hallmark of cystic fibrosis (CF) and many CF patients are infected persistently by Staphylococcus aureus. Thymidine-dependent trimethoprim-sulfamethoxazole (SXT)-resistant S. aureus small-colony variants (SCVs), often in combination with isogenic normal S. aureus phenotypes, are highly prevalent and persistent in airway secretions of CF patients due to long-term SXT therapy (B. Kahl, M. Herrmann, A. S. Everding, H. G. Koch, K. Becker, E. Harms, R. A. Proctor, and G. Peters, J. Infect. Dis. 177:1023-1029, 1998). In this report, SCVs were compared to normal S. aureus by transcription analysis of important regulator (sigB, sarA, and agr) and virulence (alpha-hemolysin, hla, and protein A, spa) genes. Growth curve analyses revealed longer doubling times and lower final densities for SCVs than for normal strains. sigB activity was measured by transcription analysis of the sigB target gene asp23. For nearly all SCVs, expression of all regulators was decreased as assessed by asp23 reverse transcription-PCR for sigB and Northern analysis for sarA and agr. These results are in agreement with diminished hla signals in all SCVs and increased spa signals in 5 of 10 SCVs compared to the isogenic normal S. aureus. Both supplementation of SCVs with thymidine and activation of the agr quorum-sensing system by the supernatant of the isogenic normal strain reversed transcription to almost normal levels. In conclusion, multiple changes in growth characteristics and in regulator and virulence gene expression render SCVs less virulent and allow them to survive in the hostile environment present in the airways of CF patients, thereby illustrating adaptation of the bacteria during long-term persistence.

• Evaluation of two chromogenic agar media for recovery and identification of Staphylococcus aureus small-colony variants.

  Authors: Frank Kipp, Barbara C Kahl, Karsten Becker, Ellen J Baron, Richard A Proctor, Georg Peters, Christof von Eiff

  Journal of clinical microbiology. 05/2005; 43(4):1956-9.

  To identify the most rapid and reliable technique for recovery and identification of Staphylococcus aureus small-colony variants (SCVs), the colonial appearance of 106 isolates representing SCVs andTo identify the most rapid and reliable technique for recovery and identification of Staphylococcus aureus small-colony variants (SCVs), the colonial appearance of 106 isolates representing SCVs and the normal phenotype were evaluated on two newly described chromogenic agar media. Although almost all of the SCVs grew on the chromogenic agar media, they did not exhibit a change of color. In comparison with conventional media, S. aureus ID agar (SAID; bioMerieux, La Balme Les Grottes, France) showed the most reliable results, with 49 of 53 SCVs tested growing either as an SCV colony or with a normal phenotype after only 24 h of incubation. Growth of SCVs was often not detected before 72 h of incubation on some of the media tested. In conclusion, the most accurate and rapid method to detect both the species S. aureus and the SCV phenotype is to inoculate specimens onto both Columbia blood agar and SAID.

• Variation of the polymorphic region X of the protein A gene during persistent airway infection of cystic fibrosis patients reflects two independent mechanisms of genetic change in Staphylococcus aureus.

  Authors: Barbara C Kahl, Alexander Mellmann, Susanne Deiwick, Georg Peters, Dag Harmsen

  Journal of clinical microbiology. 02/2005; 43(1):502-5.

  Variation of the polymorphic region of the protein A gene (spa) was observed during long-term persistence of Staphylococcus aureus in the airways of 10 cystic fibrosis patients and occurred at a rateVariation of the polymorphic region of the protein A gene (spa) was observed during long-term persistence of Staphylococcus aureus in the airways of 10 cystic fibrosis patients and occurred at a rate of one genetic change every 70 months. Independent mutational events were observed eight times in 142 isolates: four deletions, two duplications of repeats, and two point mutations.

• Increased frequency of genomic alterations in Staphylococcus aureus during chronic infection is in part due to phage mobilization.

  Authors: Christiane Goerke, Saskia Matias y Papenberg, Simone Dasbach, Klaus Dietz, Rita Ziebach, Barbara C Kahl, Christiane Wolz

  The Journal of infectious diseases. 03/2004; 189(4):724-34.

  We assessed the nature and frequency of genome alterations in Staphylococcus aureus during chronic lung infection in patients with cystic fibrosis (CF) and during colonization of the nares in healthyWe assessed the nature and frequency of genome alterations in Staphylococcus aureus during chronic lung infection in patients with cystic fibrosis (CF) and during colonization of the nares in healthy individuals. Only individuals harboring the same S. aureus clone on consecutive samplings were included in the present study. Clone definition was based on pulsed-field gel electrophoresis (PFGE) analysis. Minor fragment variations in consecutive clones were interpreted as genome alterations. The frequency of genome alterations was significantly higher in S. aureus derived from patients with CF (mean time, 1.03 years) than in isolates derived from healthy individuals (mean time, 13.4 years). In total, 19 S. aureus strain pairs showing genome alterations were available for molecular analysis to clarify the nature of recombinational events in the host environment. In 8 cases, genome alteration could be linked to phage mobilization. Phage conversion of beta-toxin production was evident in 7 pairs. In 1 strain pair, changes in the PFGE pattern were accompanied by deletion of a phage similar to ETA. Obviously, phage mobilization plays an important role in vivo. During long-term lung infection in patients with CF, the specific host response and/or the regular exposure to antibiotics exercises strong selective pressure on the pathogen. Genome plasticity may facilitate the adaptation to various host conditions.

• agr-dependent bacterial interference has no impact on long-term colonization of Staphylococcus aureus during persistent airway infection of cystic fibrosis patients.

  Authors: Barbara C Kahl, Karsten Becker, Alexander W Friedrich, Julia Clasen, Bhanu Sinha, Christof von Eiff, Georg Peters

  Journal of clinical microbiology. 12/2003; 41(11):5199-201.

  The agr specificity group distribution of persistent Staphylococcus aureus clones recovered from the airways of cystic fibrosis (CF) patients did not differ from that of isolates recovered fromThe agr specificity group distribution of persistent Staphylococcus aureus clones recovered from the airways of cystic fibrosis (CF) patients did not differ from that of isolates recovered from various clinical infections and healthy nasal carriers. The success of CF clones in terms of cocolonization and/or infection with S. aureus, prevalence of clones, or persistence appeared to be independent of agr group specificity.

• Population dynamics of persistent Staphylococcus aureus isolated from the airways of cystic fibrosis patients during a 6-year prospective study.

  Authors: Barbara C Kahl, Angelika Duebbers, Gabriele Lubritz, Johannes Haeberle, Hans G Koch, Barbara Ritzerfeld, Marion Reilly, Erik Harms, Richard A Proctor, Mathias Herrmann, Georg Peters

  Journal of clinical microbiology. 10/2003; 41(9):4424-7.

  Molecular typing of normal (n = 456) and small-colony-variant (SCV; n = 239) Staphylococcus aureus isolates cultured from the airways of 52 of 72 cystic fibrosis (CF) patients (72.2%) during a 6-yearMolecular typing of normal (n = 456) and small-colony-variant (SCV; n = 239) Staphylococcus aureus isolates cultured from the airways of 52 of 72 cystic fibrosis (CF) patients (72.2%) during a 6-year prospective study revealed a median long-term persistence of 37 months (range, 6 to 70). SCV persisted longer in the airways than the normal S. aureus (statistically not significant). Pulsed-field gel electrophoresis identified six prevalent clonal lineages, which were cultured from more than one patient (3 to 12 patients), and 39 individual clones, which were isolated only from single patients. The SCV phenotype was not restricted to a distinct clonal lineage but occurred in many different clones. Most patients (33 of 52, 63.46%) harbored single clones. This study provides a basis for improved understanding of S. aureus colonization and infection dynamics in CF patients.