Nationwide prevalence of human papillomavirus infection and viral genotype distribution in 37 cities in China.

BACKGROUND: Type-specific high-risk HPV (hrHPV) infection is related to cervical carcinogenesis. The prevalence of hrHPV infection varies geographically, which might reflect the epidemiological characteristics of cervical cancer among different populations. To establish a foundation for HPV-based screening and vaccination programs in China, we investigated the most recent HPV prevalence and genotypic distributions in different female age groups and geographical regions in China. METHODS: In 2012, a total of 120,772 liquid-based cytological samples from women enrolled for population- or employee-based cervical screening in 37 Chinese cities were obtained by the Laboratory of Molecular Infectious Diseases of Guangzhou KingMed. A total of 111,131 samples were tested by Hybrid Capture II and the other 9,641 were genotyped using the Tellgenplex™ HPV DNA Assay. RESULTS: The total positive rate for hrHPV was 21.07 %, which ranged from 18.42 % (Nanchang) to 31.94 % (Haikou) and varied by region. The regions of Nanchang, Changsha, Hangzhou, Chengdu, Fuzhou, Guangdong, and Guiyang could be considered the low prevalence regions. Age-specific prevalence showed a "two-peak" pattern, with the youngest age group (15-19 years) presenting the highest hrHPV infection rate (30.55 %), followed by a second peak for the 50-60-year-old group. Overall, the most prevalent genotypes were HPV16 (4.82 %) and HPV52 (4.52 %), followed by HPV58 (2.74 %). Two genotypes HPV6 (4.01 %) and HPV11 (2.29 %) were predominant in the low-risk HPV (lrHPV) type, while the mixed genotypes HPV16 + 52 and HPV52 + 58 were most common in women with multiple infections. CONCLUSIONS: This study shows that HPV infection in China has increased to the level of an "HPV-heavy-burden" zone in certain regions, with prevalence varying significantly among different ages and regions. Data from this study represent the most current survey of the nationwide prevalence of HPV infection in China, and can serve as valuable reference to guide nationwide cervical cancer screening and HPV vaccination programs.

Probiotics improve survival of septic rats by suppressing conditioned pathogens in ascites.

AIM: To investigate the benefits of probiotics treatment in septic rats. METHODS: The septic rats were induced by cecal ligation and puncture. The animals of control, septic model and probiotics treated groups were treated with vehicle and mixed probiotics, respectively. The mixture of probiotics included Bifidobacterium longum, Lactobacillus bulgaricus and Streptococcus thermophilus. We observed the survival of septic rats using different amounts of mixed probiotics. We also detected the bacterial population in ascites and blood of experimental sepsis using cultivation and real-time polymerase chain reaction. The severity of mucosal inflammation in colonic tissues was determined. RESULTS: Probiotics treatment improved survival of the rats significantly and this effect was dose dependent. The survival rate was 30% for vehicle-treated septic model group. However, 1 and 1/4 doses of probiotics treatment increased survival rate significantly compared with septic model group (80% and 55% vs 30%, P < 0.05). The total viable counts of bacteria in ascites decreased significantly in probiotics treated group compared with septic model group (5.20 ± 0.57 vs 9.81 ± 0.67, P < 0.05). The total positive rate of hemoculture decreased significantly in probiotics treated group compared with septic model group (33.3% vs 100.0%, P < 0.05). The population of Escherichia coli and Staphylococcus aureus in ascites of probiotics treated group were decreased significantly compared with that of septic model group (3.93 ± 0.73 vs 8.80 ± 0.83, P < 0.05; 2.80 ± 1.04 vs 5.39 ± 1.21, P < 0.05). With probiotics treatment, there was a decrease in the scores of inflammatory cell infiltration into the intestinal mucosa in septic animals (1.50 ± 0.25 vs 2.88 ± 0.14, P < 0.01). CONCLUSION: Escherichia coli and Staphylococcus aureus may be primary pathogens in septic rats. Probiotics improve survival of septic rats by suppressing these conditioned pathogens.

Penicillin-binding proteins and cell wall composition in beta-lactam-sensitive and -resistant strains of Staphylococcus sciuri.

A close homologue of the acquired Staphylococcus aureus mecA gene is present as a native gene in Staphylococcus sciuri. We determined the patterns of penicillin-binding proteins (PBPs) and the peptidoglycan compositions of several S. sciuri strains to explore the functions of this mecA homologue, named pbpD, in its native S. sciuri environment. The protein product of pbpD was identified as PBP4 with a molecular mass of 84 kDa, one of the six PBPs present in representatives of each of three subspecies of S. sciuri examined. PBP4 had a low affinity for nafcillin, reacted with a monoclonal antibody raised against S. aureus PBP2A, and was greatly overproduced in oxacillin-resistant clinical isolate S. sciuri SS37 and to a lesser extent in resistant laboratory mutant K1M200. An additional PBP inducible by oxacillin and corresponding to S. aureus PBP2A was identified in another oxacillin-resistant clinical isolate, S. sciuri K3, which harbors an S. aureus copy of mecA. Oxacillin resistance depended on the overtranscribed S. sciuri pbpD gene in strains SS37 and K1M200, while the resistance of strain K3 depended on the S. aureus copy of mecA. Our data provide evidence that both S. aureus mecA and S. sciuri pbpD can function as resistance determinants in either an S. aureus or an S. sciuri background and that the protein products of these genes, S. aureus PBP2A and S. sciuri PBP4, can participate in the biosynthesis of peptidoglycan, the muropeptide composition of which depends on the bacterium "hosting" the resistance gene.

Tracking the in vivo evolution of multidrug resistance in Staphylococcus aureus by whole-genome sequencing.

The spread of multidrug-resistant Staphylococcus aureus (MRSA) strains in the clinical environment has begun to pose serious limits to treatment options. Yet virtually nothing is known about how resistance traits are acquired in vivo. Here, we apply the power of whole-genome sequencing to identify steps in the evolution of multidrug resistance in isogenic S. aureus isolates recovered periodically from the bloodstream of a patient undergoing chemotherapy with vancomycin and other antibiotics. After extensive therapy, the bacterium developed resistance, and treatment failed. Sequencing the first vancomycin susceptible isolate and the last vancomycin nonsusceptible isolate identified genome wide only 35 point mutations in 31 loci. These mutations appeared in a sequential order in isolates that were recovered at intermittent times during chemotherapy in parallel with increasing levels of resistance. The vancomycin nonsusceptible isolates also showed a 100-fold decrease in susceptibility to daptomycin, although this antibiotic was not used in the therapy. One of the mutated loci associated with decreasing vancomycin susceptibility (the vraR operon) was found to also carry mutations in six additional vancomycin nonsusceptible S. aureus isolates belonging to different genetic backgrounds and recovered from different geographic sites. As costs drop, whole-genome sequencing will become a useful tool in elucidating complex pathways of in vivo evolution in bacterial pathogens.

Overexpression of genes of the cell wall stimulon in clinical isolates of Staphylococcus aureus exhibiting vancomycin-intermediate- S. aureus-type resistance to vancomycin.

Custom-designed gene chips (Affymetrix) were used to determine genetic relatedness and gene expression profiles in Staphylococcus aureus isolates with increasing MICs of vancomycin that were recovered over a period of several weeks from the blood and heart valve of a patient undergoing extensive vancomycin therapy. The isolates were found to be isogenic as determined by the GeneChip based genotyping approach and thus represented a unique opportunity to study changes in gene expression that may contribute to the vancomycin resistance phenotype. No differences in gene expression were detected between the parent strain, JH1, and JH15, isolated from the nares of a patient contact. Few expression changes were observed between blood and heart valve isolates with identical vancomycin MICs. A large number of genes had altered expression in the late stage JH9 isolate (MIC = 8 microg/ml) compared to JH1 (MIC = 1 microg/ml). Most genes with altered expression were involved in housekeeping functions or cell wall biosynthesis and regulation. The sortase-encoding genes, srtA and srtB, as well as several surface protein-encoding genes were downregulated in JH9. Two hypothetical protein-encoding genes, SAS016 and SA2343, were dramatically overexpressed in JH9. Interestingly, 27 of the genes with altered expression in JH9 grown in drug-free medium were found to be also overexpressed when the parental strain JH1 was briefly exposed to inhibitory concentrations of vancomycin, and more than half (17 of 27) of the genes with altered expression belonged to determinants that were proposed to form part of a general cell wall stress stimulon (S. Utaida et al., Microbiology 149:2719-2732, 2003).

Expression of high-level methicillin resistance in Staphylococcus aureus from the Staphylococcus sciuri mec A homologue: role of mutation(s) in the genetic background and in the coding region of mec A.

A close homologue of the mec A gene, the primary drug resistance determinant in methicillin resistant Staphylococcus aureus (MRSA), is ubiquitous in the animal commensal species Staphylococcus sciuri, yet most isolates of this staphylococcal species are susceptible to beta-lactam antibiotics including methicillin. Recently, we showed that in a methicillin-resistant mutant of S. sciuri prepared in the laboratory, the mec A homologue is converted to an antibiotic resistance gene by a point mutation introduced into the -10 consensus of the promoter and such promoter-up mutants of the S. sciuri mec A can express a significant degree of methicillin resistance when introduced into an antibiotic-susceptible strain of S. aureus. We now demonstrate that in this system further increase of the drug resistance phenotype may be achieved under antibiotic pressure by at least two different mechanisms. The first one of these involves the introduction of a point mutation at nucleotide Nt 1889 in the coding region of the S. sciuri-derived mec A determinant, resulting in the replacement of an asparagine with a threonine residue downstream of the conserved SXXK motif which causes extensive reduction in the beta-lactam antibiotic binding capacity (affinity) of the penicillin binding protein (PBP) encoded by the S. sciuri mec A homologue. A second, distinct, mechanism causing increased methicillin resistance is associated with mutation(s) of unknown nature in the genetic background of the S. aureus host.

High-level (beta)-lactam resistance and cell wall synthesis catalyzed by the mecA homologue of Staphylococcus sciuri introduced into Staphylococcus aureus.

A close homologue of mecA, the determinant of broad-spectrum beta-lactam resistance in Staphylococcus aureus was recently identified as a native gene in the animal commensal species Staphylococcus sciuri. Introduction of the mecA homologue from a methicillin-resistant strain of S. sciuri into a susceptible strain of S. aureus caused an increase in drug resistance and allowed continued growth and cell wall synthesis of the bacteria in the presence of high concentrations of antibiotic. We determined the muropeptide composition of the S. sciuri cell wall by using a combination of high-performance liquid chromatography, mass spectrometric analysis, and Edman degradation. Several major differences between the cell walls of S. aureus and S. sciuri were noted. The pentapeptide branches in S. sciuri were composed of one alanine and four glycine residues in contrast to the pentaglycine units in S. aureus. The S. sciuri wall but not the wall of S. aureus contained tri- and tetrapeptide units, suggesting the presence of dd- and ld-carboxypeptidase activity. Most interestingly, S. aureus carrying the S. sciuri mecA and growing in methicillin-containing medium produced a cell wall typical of S. aureus and not S. sciuri, in spite of the fact that wall synthesis under these conditions had an absolute dependence on the heterologous S. sciuri gene product. The protein product of the S. sciuri mecA can efficiently participate in cell wall biosynthesis and build a cell wall using the cell wall precursors characteristic of the S. aureus host.

Penicillin-binding protein 2 is essential for expression of high-level vancomycin resistance and cell wall synthesis in vancomycin-resistant Staphylococcus aureus carrying the enterococcal vanA gene complex.

A combination of biochemical and genetic experiments were performed in order to better understand the mechanism of expression of high-level vancomycin resistance in Staphylococcus aureus. The transcription of pbp2 of the highly vancomycin- and oxacillin-resistant strain COLVA200 and its mutant derivative with inactivated mecA were put under the control of an inducible promoter, and the dependence of oxacillin and vancomycin resistance and cell wall composition on the concentration of the isopropyl-beta-D-thiogalactopyranoside inducer was determined. The results indicate that mecA--the genetic determinant of oxacillin resistance--while essential for oxacillin resistance, is not involved with the expression of vancomycin resistance. Penicillin binding protein 2A, the protein product of mecA, appears to be unable to utilize the depsipeptide cell wall precursor produced in the vancomycin-resistant cells for transpeptidation. The key penicillin binding protein essential for vancomycin resistance and for the synthesis of the abnormally structured cell walls characteristic of vancomycin-resistant S. aureus (A. Severin, K. Tabei, F. Tenover, M. Chung, N. Clarke, and A. Tomasz, J. Biol. Chem. 279:3398-3407, 2004) is penicillin binding protein 2.

Expression, purification and crystallization of an extended-spectrum beta-lactamase from Klebsiella oxytoca.

OXY-1a is an extended-spectrum beta-lactamase from the conditional pathogenic bacterium Klebsiella oxytoca. OXY-1a is responsible for the antibiotic resistance of this pathogen. A soluble form of OXY-1a with a His tag at its C-terminus was overexpressed in Escherichia coli. The recombinant protein was purified and crystallized at room temperature using PEG 4000 as the main precipitant. Two crystal forms were obtained from the same growth conditions. One was orthorhombic, with crystals that diffracted to better than 1.9 A, while the other was tetragonal, with crystals that only diffracted to about 3.0 A. Complete data sets were collected from both crystal forms. The orthorhombic crystal belongs to space group P2(1)2(1)2(1), with unit-cell parameters a = 46.54, b = 73.43, c = 84.56 A, while the tetragonal crystal has unit-cell parameters a = b = 73.72, c = 96.81 A. The asymmetric unit of the orthorhombic crystal is estimated to contain one OXY-1a molecule, giving a crystal volume per protein weight (V(M)) of 2.25 A(3) Da(-1) and a solvent content of 45%.

Development of methicillin resistance in clinical isolates of Staphylococcus sciuri by transcriptional activation of the mecA homologue native to s.

The beta-lactam resistance gene mecA was acquired by Staphylococcus aureus from an extraspecies source. The search for the possible origin of this gene has led to the identification of a close structural homologue of mecA as a native gene in the animal species Staphylococcus sciuri. Surprisingly, the overwhelming majority of S. sciuri isolates were fully susceptible to beta-lactam antibiotics in spite of the ubiquitous presence of the mecA homologue in the bacteria. We now describe two unusual S. sciuri strains isolated from humans-SS-37 and SS-41-that showed resistance to methicillin associated with high rates of transcription of the mecA homologue and production of a protein resembling penicillin binding protein 2a, the gene product of S. aureus mecA. In strain SS-37 increased transcription of the mecA homologue was related to insertion of an IS256 element upstream of the structural gene, and strain SS-41 had single nucleotide alterations in the promoter region of the mecA homologue which appear to be related to up-regulation of the rate of transcription. A third methicillin-resistant human isolate of S. sciuri that carries both the native mecA homologue and a methicillin-resistant S. aureus (MRSA) type mecA, strain K3, was now shown to be unstable in the absence of drug selection, causing the segregation of antibiotic-susceptible cells accompanied by the loss of the MRSA type mecA. These observations illustrate the remarkable variety of strategies available to bacteria for acquiring mechanisms of drug resistance in the in vivo environment.