- Volume 61, Issue 11, 2012

Rosacea is a common dermatological condition that predominantly affects the central regions of the face. Rosacea affects up to 3 % of the world’s population and a number of subtypes are recognized. Rosacea can be treated with a variety of antibiotics (e.g. tetracycline or metronidazole) yet no role for bacteria or microbes in its aetiology has been conclusively established. The density of Demodex mites in the skin of rosacea patients is higher than in controls, suggesting a possible role for these mites in the induction of this condition. In addition, Bacillus oleronius, known to be sensitive to the antibiotics used to treat rosacea, has been isolated from a Demodex mite from a patient with papulopustular rosacea and a potential role for this bacterium in the induction of rosacea has been proposed. Staphylococcus epidermidis has been isolated predominantly from the pustules of rosacea patients but not from unaffected skin and may be transported around the face by Demodex mites. These findings raise the possibility that rosacea is fundamentally a bacterial disease resulting from the over‐proliferation of Demodex mites living in skin damaged as a result of adverse weathering, age or the production of sebum with an altered fatty acid content. This review surveys the literature relating to the role of Demodex mites and their associated bacteria in the induction and persistence of rosacea and highlights possible therapeutic options.

The characterization and tracking of pathogenic micro-organisms in the clinical laboratory and public health environment demand schemes that are easy to standardize and use, are automated and high-throughput, and provide portable data. A combined genomarkers approach for Salmonella enterica based on comparative sequence analysis by mass spectrometry has been developed. The scheme targets genes encoding synthesis and assembly of antigens, metabolic pathway enzymes, virulence factors and fluoroquinolone resistance, covering the essential sequences that distinguish between and identify variation within serotypes. This study demonstrated how this single method could replace the combination of methods currently required to determine serotypes, subtypes, antibiotic resistance profiles and the genomic relatedness of Salmonella isolates. The results revealed genomic variation within seven serotypes previously unreported. This variation can be detected by using nucleotide sequence differences in the Salmonella flagellin gene fliC as markers that are not detected by traditional serotyping methods.

Francisella tularensis is the aetiological agent of tularaemia, a zoonotic disease with worldwide prevalence. F. tularensis is a highly pathogenic organism and has been designated a category A biothreat agent by the Centers for Disease Control and Prevention. Tularaemia is endemic in much of the USA, Europe and parts of Asia. It is transmitted by numerous vectors and vehicles such as deer flies, ticks and rabbits. Currently, there are four recognized subspecies of F. tularensis: tularensis (type A), holarctica (type B), mediasiatica and novicida. Within the type A classification there are two subclassifications, type A.I and A.II, each with a specific geographical distribution across the USA. F. tularensis subsp. holartica (type B) is found in both the USA and Europe. Because of virulence differences among subtypes, it is important that health departments, hospitals and other government agencies are able to quickly identify each subtype. The purpose of this study was to develop a multiplex real-time PCR assay for the identification and discrimination of type A.I, type A.II, type B and novicida subspecies of F. tularensis. The assay was validated using 119 isolates of F. tularensis, three of its nearest neighbours and 14 other bacterial pathogens. This assay proved to be ~98 % successful at identifying the known subspecies of F. tularensis and could prove to be a useful tool in the characterization of this important pathogen.

A multiplex TaqMan real-time PCR to detect carbapenem-hydrolysing class D β-lactamases (bla OXA-23-like, bla OXA-24/40-like, bla OXA-51-like and bla OXA-58-like genes) was developed and evaluated for early detection of imipenem (IMP) resistance in clinically significant Acinetobacter baumannii isolates. Well-characterized strains of A. baumannii were used as positive controls and non-Acinetobacter strains were used to assess specificity. Analytical sensitivity was quantified by comparison with the number of bacterial c.f.u. Forty of 46 (87 %) clinically significant and IMP-resistant A. baumannii isolates were positive for the bla OXA-23-like gene, and one isolate (2 %) was positive for the bla OXA-58-like gene. The bla OXA-24/40-like gene was not detected in any of the 46 IMP-resistant strains and the bla OXA-51-like gene was identified in both IMP-resistant and non-resistant A. baumannii. All 11 non-Acinetobacter bacteria produced a negative result for each of the four bla OXA genes. This assay was able to detect as few as 10 c.f.u. per assay. This real-time PCR method demonstrated rapid detection of OXA-like carbapenem resistance in A. baumannii in comparison with phenotypic susceptibility testing methodology. This method could be adapted to a multiplexed single reaction for rapid detection of genes associated with carbapenem resistance in A. baumannii and potentially other clinically significant multidrug-resistant Gram-negative bacteria.

Our objective was to compare human papillomavirus (HPV) detection in paired self-collected vaginal samples transported by overnight mail in liquid specimen transport medium (STM) (wet) or in dry tubes (dry). Women aged 18–24 years were recruited online to self-collect vaginal swab samples at home for HPV testing and 159 women returned paired wet and dry samples. Dry samples were rehydrated with STM upon arrival at the laboratory. HPV was detected by the Roche Linear Array HPV genotyping test (37 genotypes) and Kappa and McNemar statistics were used to compare wet versus dry samples for detecting HPV. Of the subjects tested in this study, 51 % were HPV-positive (in either sample) and 40 % were positive for high-risk HPV. A total of 216 type-specific infections were detected among the 80 HPV-positive women. Almost perfect agreement was observed between paired samples for detecting any HPV (subject-level positive agreement: 91.9 %, κ: 0.85) or type-specific HPV (positive agreement across types: 90.1 %, κ: 0.90). Similar agreement between sample types was seen when testing for high-risk types and 81.9 % of all type-specific infections were detected in both samples. Among discordant pairs, wet samples were 3.3 times more likely to be positive for type-specific HPV than dry samples (P = 0.02). However, in 63.6 % of wet-positive/dry-negative discordant pairs analysed for viral load, type-specific HPV was either undetectable or detected at a low level (<100 copies) in the wet samples, suggesting that the majority of infections missed by using dry samples are less likely to be clinically relevant. Our results indicate that dry transport is a feasible option for transporting at-home self-collected vaginal samples for HPV DNA testing.

Two multiplex PCR screening capabilities (TaqMan Array Cards and FilmArray) were evaluated for their ability to detect Bacillus anthracis, Francisella tularensis and Yersinia pestis in blood samples obtained from respective murine infection models. Blood samples were obtained from infected mice at 24 h intervals after exposure. Multiplex PCR results were compared with standard blood culture and singleplex real-time PCR. Across all three models, 71 mice were tested in total, within which a subset of 43 samples was shown to contain an infecting agent by at least one of the detection technologies. Within this subset of positive samples, for each model studied, the detection rates of each technology were compared. The B. anthracis model blood culture (14 of 15 agent-containing samples tested) and FilmArray PCR (12 of 15) were shown to have equivalent detection rates, which were significantly higher (at the 95 % confidence level) than singleplex (five of 14) or Array Card (two of 14) PCRs. The F. tularensis model blood culture (12 of 12) was shown to have a significantly higher (at 95 % confidence level) detection rate than all PCR technologies, with FilmArray (seven of 11) and singleplex (seven of 12) PCRs shown to have significantly higher (at 95 % confidence level) detection rates than the Array Card PCR (two of 11). Within the Y. pestis model, there was no significant difference in detection rates between blood culture (10 of 16), singleplex PCR (14 of 16), Array Card PCR (10 of 16) and FilmArray PCR (10 of 13).

Rapid identification of the causative bacteria of sepsis in patients can contribute to the selection of appropriate antibiotics and improvement of patients’ prognosis. Genotypic identification is an emerging technology that may provide an alternative method to, or complement, established phenotypic identification procedures. We evaluated a rapid protocol for bacterial identification based on PCR and pyrosequencing of the V1 and V3 regions of the 16S rRNA gene using DNA extracted directly from positive blood culture samples. One hundred and two positive blood culture bottles from 68 patients were randomly selected and the bacteria were identified by phenotyping and pyrosequencing. The results of pyrosequencing identification displayed 84.3 and 64.7 % concordance with the results of phenotypic identification at the genus and species levels, respectively. In the monomicrobial samples, the concordance between the results of pyrosequencing and phenotypic identification at the genus level was 87.0 %. Pyrosequencing identified one isolate in 60 % of polymicrobial samples, which were confirmed by culture analysis. Of the samples identified by pyrosequencing, 55.7 % showed consistent results in V1 and V3 targeted sequencing; other samples were identified based on the results of V1 (12.5 %) or V3 (31.8 %) sequencing alone. One isolate was erroneously identified by pyrosequencing due to high sequence similarity with another isolate. Pyrosequencing identified one isolate that was not detected by phenotypic identification. The process of pyrosequencing identification can be completed within ~4 h. The information provided by DNA-pyrosequencing for the identification of micro-organisms in positive blood culture bottles is accurate and could prove to be a rapid and useful tool in standard laboratory practice.

Seventeen meticillin-resistant coagulase-negative staphylococci (MRCoNS), including ten Staphylococcus capitis, four Staphylococcus cohnii, two Staphylococcus haemolyticus and one Staphylococcus sciuri, and an Enterococcus faecium isolate with various levels of linezolid resistance were isolated from intensive care units in a Chinese hospital. PFGE indicated that the four S. cohnii isolates belonged to a clonal strain, and that nine of the S. capitis isolates were indistinguishable (clone A1) and the other one was closely related (clone A2). A G2576T mutation was identified in domain V of the 23S rRNA gene in the E. faecium isolate. Besides the G2576T mutation, a novel C2104T mutation was detected in the nine clone A1 S. capitis isolates. The cfr gene was detected in all the staphylococci except an S. sciuri isolate, whose 23S rRNA gene contained the G2576T mutation. There was a clonal dissemination of linezolid-resistant MRCoNS in intensive care units of our hospital, and this is the first report, to our knowledge, of linezolid-resistant staphylococci and enterococci in China.

Chlamydia pneumoniae, an intracellular bacterium, is associated with respiratory diseases, reinfectivity and chronic diseases such as cardiovascular disease, hypertension and stroke. The risk of infection is higher and infections are a serious clinical problem in patients with type 1 (insulin-dependent) diabetes mellitus (T1DM). Although diabetes mellitus and hyperglycaemia are considered possible risk factors for various types of aetiological agents, the epidemiological evidence concerning C. pneumoniae infection is scanty. The aim of the present study was to evaluate the impact of glycosylated haemoglobin (HbA1c) levels, an indicator of a hyperglycaemic state, on C. pneumoniae infection and disease chronicity; in addition we compared the duration of diabetes with the occurrence of C. pneumoniae infection. C. pneumoniae blood real time PCR and serology (IgG, IgA and IgM) assays by an ELISA method were performed. C. pneumoniae DNA was detected in 46.5 % [95 % confidence interval (CI) = 35.1–57.9 %] of the patients with T1DM; this prevalence is higher (P<0.05) than in non-diabetic paediatric controls, 10.5 % (95 % CI = 3.6–17.4 %). IgG/IgA C. pneumoniae antibody positivity was significantly (P≤0.05) more common in patients in poor metabolic control (HbA1c >9 %) versus patients in good metabolic control (HbA1c <7 %), suggesting that the metabolic control of the disease is compromised in the patients with T1DM. In conclusion, adolescents with T1DM were more likely to show signs of infection with C. pneumoniae compared with healthy adolescents and the results suggest an increased risk of progressing from an acute C. pneumoniae infection to a chronic form.

Necrotizing fasciitis, caused by Klebsiella pneumoniae, is a rare and life-threatening bacterial infection. Most documented cases have been reported from Asia, particularly associated with diabetes mellitus. The prevalence of this infection in the USA is rare, especially among persons of non-Asian descent and those without travel to Asia. We report a case of disseminated necrotizing fasciitis, caused by K. pneumoniae, in a Latin American male with diabetes mellitus. Given our review of the literature, this is the only case report, to our knowledge, of a Latin American patient with Klebsiella necrotizing fasciitis in the USA. This case may reflect the geographical spread and emergence of K. pneumoniae infection in the USA. Clinicians need to be aware of the possible relationship between this organism and necrotizing fasciitis in persons of Latin American descent with diabetes mellitus.

Due to the differences in the management of Mycobacterium kansasii disease and tuberculosis, an accurate diagnosis is required. This report, which describes what we believe to be the first documented case of M. kansasii infection in a patient suffering from anorexia nervosa, sheds light on the possible occurrence of a non-tuberculous mycobacterial infection that can mimic tuberculosis, on the risk of a misleading interpretation of interferon-gamma release assays, and on the temporal response to these tests.

Bacterial infection in patients who have undergone liver transplantation is a major complication of the procedure. Leuconostoc spp. are important pathogenic bacteria in individuals with poor immune function, especially transplant patients. In this report, we describe the case of a 45-year-old Asian male liver transplant recipient who was initially preliminarily diagnosed with infection with Leuconostoc pseudomesenteroides by using the microbial tests of the VITEK 2 system and the aesculin hydrolysis test, and with vancomycin-resistant Enterococcus. Subsequently, the Leuconostoc isolate was identified as Leuconostoc lactis by 16S rRNA gene partial sequencing. In this paper, we discuss our identification of L. lactis based on physiological characteristics and molecular methodology. Accurate identification of these infections is important for the outcome; use of 16S rRNA gene sequence analysis offers a rapid and precise diagnostic approach. Administration of the drug linezolid may be useful for the treatment of both Leuconostoc spp. and vancomycin-resistant Enterococcus infections. We suggest that clinical analysts should use molecular methods in addition to biochemical tests in order to identify Leuconostoc at the species level more accurately.