bluuebunny/crossref_metadata_2025_split huggingface dataset:
Variations inemmType among Group A Streptococcal Isolates Causing Invasive or Noninvasive Infections in a Nationwide Study
Authors: Ekelund Kim , Darenberg Jessica , Norrby-Teglund Anna , Hoffmann Steen , Bang Didi , Skinhøj Peter , Konradsen Helle Bossen 
Published: July 2005

ABSTRACTSince the late 1980s several studies have described the increased incidence and severity of invasive group A streptococcal (GAS) infections. However, most studies on GAS pathogenesis have focused on information obtained during outbreaks. We analyzed isolate distribution and host susceptibility as part of a nationwide prospective surveillance study performed between January 2001 and August 2002. GAS isolates collected from 201 patients with invasive infections, 335 patients with noninvasive infections, and 17 asymptomatic carriers were characterized with respect to theiremmtypes and superantigen genotypes. The superantigen-neutralizing capacity and levels of antibodies against streptolysin O and DNAse B were determined for isolates from the sera from 36 invasive cases and 91 noninvasive cases.emmtype 1 (emm-1) isolates were significantly more common among invasive cases, whereasemm-4,emm-6, andemm-12 dominated among the noninvasive cases. The distributions of the phage-associated superantigen genes (speA,speC,speH,speI,ssa) differed among invasive and noninvasive isolates, mainly due to their linkage to certainemmtypes. No significant differences in serum superantigen-neutralizing capacities were observed. The levels of anti-streptolysin O and anti-DNAse B antibodies were highest in the sera from invasive cases. Our study emphasizes the importance of obtaining data during years with stable incidences, which will enable evaluation of future outbreak data.
AmpC Disk Test for Detection of Plasmid-Mediated AmpC β-Lactamases in
Enterobacteriaceae
Lacking Chromosomal AmpC β-Lactamases
Authors: Black Jennifer A. , Moland Ellen Smith , Thomson Kenneth S. 
Published: July 2005

ABSTRACT

Although plasmid-mediated AmpC β-lactamases were first reported in the late 1980s, many infectious disease personnel remain unaware of their clinical importance. These enzymes are typically produced by isolates of
Escherichia coli
,
Klebsiella
spp.,
Proteus mirabilis
, and
Salmonella
spp. and are associated with multiple antibiotic resistance that leaves few therapeutic options. Plasmid-mediated AmpC β-lactamases have been associated with false in vitro susceptibility to cephalosporins. Many laboratories do not test for this resistance mechanism because current tests are inconvenient, subjective, lack sensitivity and/or specificity, or require reagents that are not readily available. In this study a new test, the AmpC disk test, based on filter paper disks impregnated with EDTA, was found to be a highly sensitive, specific, and convenient means of detection of plasmid-mediated AmpC β-lactamases in organisms lacking a chromosomally mediated AmpC β-lactamase. Using cefoxitin insusceptibility as a screen, the test accurately distinguished AmpC and extended-spectrum β-lactamase production and differentiated AmpCs from non-β-lactamase mechanisms of cefoxitin insusceptibility, such as reduced outer membrane permeability. The test is a potentially useful diagnostic tool. It can provide important infection control information and help to ensure that infected patients receive appropriate antibiotic therapy.
Drug Resistance Evolution of a
Mycobacterium tuberculosis
Strain from a Noncompliant Patient
Authors: Meacci Francesca , Orrù Germano , Iona Elisabetta , Giannoni Federico , Piersimoni Claudio , Pozzi Gianni , Fattorini Lanfranco , Oggioni Marco R. 
Published: July 2005

ABSTRACT

The emergence and spread of multidrug-resistant (MDR)
Mycobacterium tuberculosis
(MT) represents a worldwide health care problem because of the difficulty in treating these infections. Development of drug resistance in MT arises mainly by mutation of chromosomal genes. To investigate the evolution of a MT population during a long-lasting infection, the phenotypic and genotypic changes in the drug resistance of 10 sequential MT isolates from a noncompliant chronically infected patient were investigated. During more than 12 years of active disease, a MDR population developed; molecular typing showed one single parental strain that infected the patient and persisted throughout the disease. Molecular analysis of the drug resistance-related genes revealed that discrete subpopulations evolved over time from the parental strain by acquiring and accumulating resistance-conferring mutations to isoniazid, rifampin, and streptomycin. Overall, these observations indicate that during a chronic infection, several subpopulations may coexist in the same patient with different drug susceptibility profiles.
Genetic Relatedness between Pneumococcal Populations Originating from the Nasopharynx, Adenoid, and Tympanic Cavity of Children with Otitis Media
Authors: Tonnaer Edith L. , Rijkers Ger T. , Meis Jacques F. , Klaassen Corné H. , Bogaert Debby , Hermans Peter W. , Curfs Jo H. 
Published: July 2005

ABSTRACT

Previous studies have shown that
Streptococcus pneumoniae
exists in both middle ear effusions and the upper respiratory region from children with otitis media with effusion (OME), but it remains unclear whether these strains represent genetically identical clones. Therefore, it cannot be determined whether these bacteria originate from a common source. To determine the presence of pneumococci at different anatomical locations of OME patients, conventional culture and PCR techniques were used. To analyze the possible genetic relatedness between pneumococci from different anatomical sites, molecular typing by amplified fragment length polymorphism was utilized. The percentage of middle ear effusions of OME patients that are positive for pneumococci after PCR analysis (13%) was higher than after conventional culture (5%). Molecular fingerprints from pneumococci derived from two different anatomic sites within patients were very similar in 80% of OME patients and in 90% of acute otitis medium patients, indicating their genetic relatedness. Biofilm formation or pneumococcal L-forms probably play a role in OME, since culture-negative effusions prove to contain pneumococcal DNA. Bacteria involved in this process most likely originate from the nasopharynx since they show a close genetic relatedness with their nasopharyngeal counterparts.
Drug Susceptibility Testing of
Mycobacterium tuberculosis
by a Nitrate Reductase Assay Applied Directly on Microscopy-Positive Sputum Samples
Authors: Musa Humberto R. , Ambroggi Marta , Souto Alejandro , Ängeby K. A. Kristian 
Published: July 2005

ABSTRACT

Current methods for drug susceptibility testing of
Mycobacterium tuberculosis
are either costly or slow. As the prevalence of multidrug-resistant strains increases, the need for fast, reliable, and inexpensive methods that can also be applied in settings with scarce resources is obvious. We evaluated a rapid colorimetric nitrate reductase assay (NRA) for direct drug susceptibility testing of
M. tuberculosis
directly from clinical sputum samples with positive microscopy results for acid-fast bacilli with more than 10 acid-fast bacilli per high-power field. We have saved valuable time by omitting the preisolation step. The sensitivity (ability to detect true drug resistance) and specificity (ability to detect true drug susceptibility) of the direct NRA, using the direct proportion method as the reference, were 100 and 100%, 93 and 100%, 76 and 100%, and 55 and 99% for rifampin, isoniazid, streptomycin, and ethambutol, respectively, when tested on
M. tuberculosis
strains present in 121 samples. The results were in most cases available in 14 days. The direct NRA could be used as a rapid, inexpensive, and accurate method to determine rifampin and isoniazid susceptibility directly from sputum. The technique might become a valid alternative to traditional methods, especially in low-income countries.
Susceptibility of
Neisseria meningitidis
to 16 Antimicrobial Agents and Characterization of Resistance Mechanisms Affecting Some Agents
Authors: Jorgensen James H. , Crawford Sharon A. , Fiebelkorn Kristin R. 
Published: July 2005

ABSTRACT

Neisseria meningitidis
represents a pathogen of great public health importance in both developed and developing countries. Resistance to some antimicrobial agents used either for therapy of invasive infections or for prophylaxis of case contacts has long been recognized, although specific guidelines for susceptibility testing have not been fully developed. We have examined the susceptibilities of a collection of 442 meningococcal clinical isolates from 15 countries to 16 antimicrobial agents. These included isolates recovered between 1917 and 2004, with representatives of all major serogroups. All isolates were tested by the Clinical and Laboratory Standards Institute (formerly NCCLS) broth microdilution method using Mueller-Hinton lysed horse blood broth, while a subset of 102 isolates was tested by agar dilution using Mueller-Hinton sheep blood agar. Most isolates provided adequate growth for MIC determinations by both broth and agar methods. Growth in broth was enhanced by CO
2
incubation and was required for two strains (1.7%). MICs of the study drugs compared favorably between the broth and agar methods (79 to 100% essential agreement), and MICs also generally agreed closely (92 to 100% essential agreement, excluding azithromycin) between broth tests incubated in the two different atmospheres. Elevated penicillin and ampicillin MICs (≥0.12 μg/ml and ≥0.25 μg/ml, respectively) occurred in 14.3% and 8.6% of strains and were associated with polymorphisms of the
penA
gene encoding a modified penicillin-binding protein 2. None of the 442 isolates produced beta-lactamase. Elevated tetracycline and doxycycline (but not minocycline) MICs were associated with efflux-mediated resistance encoded by
tet
(B) in 13 strains. Resistance to sulfisoxazole in 21.7% of strains and to trimethoprim-sulfamethoxazole in 21.0% resulted from polymorphisms of
folP
encoding a modified dihydropteroate synthetase. Seven strains were resistant to rifampin due to mutations in the
rpoB
gene, and two strains were resistant to chloramphenicol due to production of chloramphenicol acetyltransferase mediated by
catP
. Two strains had reduced quinolone susceptibility due to mutations of
gyrA
. The determination of the susceptibilities of a large group of meningococcal strains (including strains with characterized resistance mechanisms) to 16 antimicrobial agents has served as the essential first step in defining susceptibility testing breakpoints specific for this organism.
Detection of
Balamuthia
Mitochondrial 16S rRNA Gene DNA in Clinical Specimens by PCR
Authors: Yagi Shigeo , Booton Gregory C. , Visvesvara Govinda S. , Schuster Frederick L. 
Published: July 2005

ABSTRACT

Balamuthia mandrillaris
is a free-living ameba that causes granulomatous amebic encephalitis in both immunocompromised and immunocompetent individuals. Because of a lack of pathognomonic symptoms and the difficulty in recognizing amebas in biopsied tissues, most cases are not diagnosed or effectively treated, leading to a >95% mortality. We report here on five cases of balamuthiasis that were diagnosed by indirect immunofluorescence (IIF) staining of serum for anti-
Balamuthia
antibodies (titer ≥ 1:128) and confirmed by IIF of unstained brain tissue sections and/or detection of amebas in hematoxylin-eosin-stained slides. Additionally, we have used the PCR for the detection of mitochondrial 16S rRNA gene DNA from the ameba in clinical specimens such as brain tissue and cerebrospinal fluid (CSF) from individuals with
Balamuthia
encephalitis.
Balamuthia
DNA was successfully detected by the PCR in clinical samples from all five individuals. It was detected in brain tissue from three cases, in CSF from three cases, and in one of two samples of lung tissue from two individuals, but not in two samples of kidney tissue tested. One sample of unfixed brain tissue was culture positive for
Balamuthia
. In order to test the sensitivity of the PCR for detection of
Balamuthia
DNA, CSF specimens from two individuals negative for amebic infection were spiked with
Balamuthia
amebas. We found that it was possible to detect
Balamuthia
DNA in the PCR mixtures containing mitochondrial DNA from 1 to as little as 0.2 ameba per reaction mixture. A single
Balamuthia
ameba contains multiple mitochondrial targets; thus, 0.2 ameba represents multiple targets for amplification and is not equivalent to 0.2 of an ameba as a target.
Frequent Carriage of Panton-Valentine Leucocidin Genes by
Staphylococcus aureus
Isolates from Surgically Drained Abscesses
Authors: Issartel Bertrand , Tristan Anne , Lechevallier Sylvain , Bruyère Franck , Lina Gerard , Garin Benoît , Lacassin Flore , Bes Michèle , Vandenesch François , Etienne Jerome 
Published: July 2005

ABSTRACT

Between 1 February and 15 April 2002, 95 patients were admitted to Gaston Bourret Territorial Hospital (New Caledonia, France) for drainage of community-acquired soft tissue abscesses.
Staphylococcus aureus
was detected in 68 cases (72%). Two-thirds of the patients with
S. aureus
infection had furuncles, which were located on the limbs in 82% of cases. The median interval between symptom onset and hospital admission was 5.7 days. Three-quarters of the patients were Melanesians living in tribes. Fifty-four
S. aureus
isolates were screened for toxin genes. Panton-Valentine leucocidin (PVL) genes were detected in 48 isolates (89%), the exfoliative toxin A gene was detected in 1 isolate, and no toxin genes were detected in 4 isolates.
S. aureus
nasal carriage was detected in 39.7% of patients with
S. aureus
infections. Two infecting
S. aureus
strains and two nasal carriage strains were resistant to methicillin. Comparative pulsed-field gel electrophoresis, performed in 16 cases, showed that five of six patients with PVL-positive nasal carriage strains were infected by the same strains. In contrast, 8 of 10 patients with PVL-negative nasal carriage strains were infected by PVL-positive strains. PVL genes thus appear to be a major virulence factor in both primary and secondary
S. aureus
skin infections.
Quantitative PCR Assay Using Sputum Samples for Rapid Diagnosis of Pneumococcal Pneumonia in Adult Emergency Department Patients
Authors: Yang Samuel , Lin Shin , Khalil Ambreen , Gaydos Charlotte , Nuemberger Eric , Juan George , Hardick Justin , Bartlett John G. , Auwaerter Paul G. , Rothman Richard E. 
Published: July 2005

ABSTRACT

Accurate diagnosis of pneumococcal pneumonia in the acute-care setting remains a challenge due to the inadequate sensitivity of conventional diagnostic tests. Sputum cultures, which are likely to have the highest diagnostic yields of all specimen types, have been considered unreliable, due to their inability to differentiate colonization from infection. Our objective was to evaluate the potential clinical utility of a rapid quantitative real-time PCR assay using sputum samples for
Streptococcus pneumoniae
in adult patients with community-acquired pneumonia (CAP). A prospective clinical observational study of consecutively enrolled emergency department patients with CAP was performed; only those patients with excess good-quality sputum samples were included for evaluation. Sputum samples were tested for the presence of
S. pneumoniae
by using a quantitative PCR that targets the pneumolysin gene. PCR findings were compared with those of a composite reference standard comprising Gram staining of sputum samples and sputum/blood cultures. The area under the curve (AUC) and a log-transformed threshold, which provides the maximal sensitivity and specificity, were calculated. Of 487 subjects enrolled, 129 were evaluable. Receiver operating characteristic curve analysis demonstrated an AUC of 0.87. Sensitivity and specificity were 90.0 percent and 80.0 percent, respectively; positive and negative predictive values were 58.7 percent and 96.2 percent, respectively. We have demonstrated that a quantitative rapid pneumolysin PCR assay has favorable accuracy for diagnosis of pneumococcal pneumonia in adult patients with CAP; this assay may be a useful diagnostic adjunct for clinicians, particularly those practicing in the acute-care setting, where rapid pathogen identification may assist in selection of the most appropriate antibiotics.
Comparative Analysis of Immunoglobulin M (IgM) Capture Enzyme-Linked Immunosorbent Assay Using Virus-Like Particles or Virus-Infected Mouse Brain Antigens To Detect IgM Antibody in Sera from Patients with Evident Flaviviral Infections
Authors: Holmes Derek A. , Purdy David E. , Chao Day-Yu , Noga Amanda J. , Chang Gwong-Jen J. 
Published: July 2005

ABSTRACT
The use of immunoglobulin M (IgM) antibody-capture enzyme-linked immunosorbent assay (MAC-ELISA) serves as a valuable tool for the diagnosis of acute flaviviral infections, since IgM antibody titers are detectable early, peak at about 2 weeks postinfection, and subsequently decline to lower levels over the next few months. Traditionally, virus-infected tissue culture or suckling mouse brain (SMB) has been the source of viral antigens used in the assay. In an effort to provide a reliable source of standardized viral antigens for serodiagnosis of the medically important flaviviruses, we have developed a eukaryotic plasmid vector to express the premembrane/membrane and envelope proteins which self-assemble into noninfectious virus-like particles (VLPs). In addition to the plasmids for Japanese encephalitis virus, West Nile virus (WNV), St. Louis encephalitis virus (SLEV), and dengue virus type 2 (DENV-2) reported earlier, we recently constructed the DENV-1, -3, and -4 VLP expression plasmids. Three blind-coded human serum panels were assembled from patients having recent DENV, SLEV, and WNV infections to assess the sensitivity and specificity of the MAC-ELISA using VLPs or SMB antigens. In addition, serum specimens from patients infected with either Powassan virus or La Crosse encephalitis virus were used to evaluate the cross-reactivity of seven mosquito-borne viral antigens. The results of the present studies showed higher sensitivity when using SLEV and WNV VLPs and higher specificity when using SLEV, WNV, and the mixture of DENV-1 to -4 VLPs in the MAC-ELISA than when using corresponding SMB antigens. Receiver operating characteristic (ROC) curve analysis, a plot of the sensitivity versus false positive rate (100 − specificity), was applied to discriminate the accuracy of tests comparing the use of VLPs and SMB antigen. The measurement of assay performance by the ROC analysis indicated that there were statistically significant differences in assay performance between DENV and WNV VLPs and the respective SMB antigens. Additionally, VLPs had a lower cutoff positive/negative ratio than corresponding SMB antigens when employed for the confirmation of current infections. The VLPs also performed better than SMB antigens in the MAC-ELISA, as indicated by a higher positive prediction value and positive likelihood ratio test. Cell lines continuously secreting these VLPs are therefore a significantly improved source of serodiagnostic antigens compared to the traditional sources of virus-infected tissue culture or suckling mouse brain.
Ceftriaxone Resistance of NontyphoidalSalmonella entericaIsolates in Northern Taiwan Attributable to Production of CTX-M-14 and CMY-2 β-Lactamases
Authors: Li Wen-Chen , Huang Fu-Yuan , Liu Chang-Pan , Weng Li-Chuan , Wang Nai-Yu , Chiu Nan-Chang , Chiang Chuen-Sheue 
Published: July 2005

ABSTRACTAmong 3,027 nontyphoidalSalmonella entericaisolates identified between January 1999 and December 2002 in a medical center in northern Taiwan, 31 were resistant to the extended-spectrum cephalosporin ceftriaxone (1.02% [31/3,027]), including 2 in 1999 (0.36% [2/549]), 13 in 2000 (1.49% [13/870]), 7 in 2001 (0.78% [7/893]), and 9 in 2002 (1.26% [9/715]). Sixteen of these isolates belonged toSalmonellaserogroup B, nine belonged to serogroup C, four belonged to serogroup D, and two belonged to serogroup E. The majority were from stool cultures. The mechanism of resistance was investigated for eight isolates, including threeS. entericaserovar Typhimurium, oneS. entericaserovar Wagenia, oneS. entericaserovar Senftenberg, oneS. entericaserovar Derby, oneS. entericaserovar Panama, and oneS. entericaserovar Duesseldorf isolate. All eight patients from whom these isolates were recovered had community-acquired infections. All eight isolates were resistant to ampicillin, ceftriaxone, and cefotaxime but susceptible to imipenem and ciprofloxacin. Ceftriaxone resistance was due to the production of the CMY-2 AmpC β-lactamase by seven isolates and the CTX-M-14 β-lactamase by the remaining isolate. Both β-lactamase genes were carried on conjugative plasmids. In a 2.5-kb region encompassing theblaCMY-2gene, at nucleotide 49 upstream of the start codon ofblaCMY-2, three of the sevenblaCMY-2-positive isolates had an A nucleotide and four had a G nucleotide. In conclusion, the ceftriaxone resistance of nontyphoidalSalmonellaisolates in our hospital was attributed to the CTX-M-14 and CMY-2 β-lactamases.
Development and Evaluation of Chlamylege, a New Commercial Test Allowing Simultaneous Detection and Identification of
Legionella
,
Chlamydophila pneumoniae
, and
Mycoplasma pneumoniae
in Clinical Respiratory Specimens by Multiplex PCR
Authors: Ginevra C. , Barranger C. , Ros A. , Mory O. , Stephan J.-L. , Freymuth F. , Joannès M. , Pozzetto B. , Grattard F. 
Published: July 2005

ABSTRACT

This study describes the development and evaluation of a new commercial test, Chlamylege (Argene Inc.), which allows the simultaneous detection in respiratory samples of
Chlamydophila pneumoniae
,
Mycoplasma pneumoniae
, and most
Legionella
species, as well as PCR inhibitors, by using a multiplex PCR and microplate hybridization. The sensitivities of Chlamylege were 1 × 10
−3
IFU, 5 × 10
−2
color-changing units, and 1 CFU per reaction tube for
C. pneumoniae
,
M. pneumoniae
, and
Legionella pneumophila
, respectively. A cohort of 154 clinical samples from patients with documented respiratory infections was analyzed by the kit, including 2 samples from patients with
C. pneumoniae
infection, 9 samples from patients with
M. pneumoniae
infection, 19 samples from patients with
Legionella
species infection, and 114 samples that tested negative for the three pathogens. All the positive specimens were correctly detected and identified by the Chlamylege kit, and no false-positive result was observed with the negative samples. The kit was then evaluated in a pediatric prospective study that included 220 endotracheal aspirates, and the results were compared with those obtained by three single in-house PCR assays. Four specimens were found to be positive for
C. pneumoniae
and six were found to be positive for
M. pneumoniae
by using both strategies. The Chlamylege kit detected two additional samples positive for
M. pneumoniae
and one additional sample positive for a
Legionella
species other than
L. pneumophila
; these three samples were shown to be true positive by other techniques. These overall results demonstrate that the Chlamylege assay is sensitive, specific, and convenient for the rapid detection and identification of atypical pathogens in clinical samples from patients with respiratory infections.