RESUMEN
Fosfomycin is a phosphonic acid derivative active against a wide spectrum of Gram-positive and Gram-negative pathogens. It is used for the treatment of uncomplicated urinary tract infections (uUTI) or severe infections by oral or intravenous (i.v.) administration. In order to improve its performance and robustness, the fosfomycin strip, an antibiotic gradient diffusion strip, was redeveloped and evaluated in the multicenter study summarized in this paper. ETEST fosfomycin (ETEST FO) clinical performance was evaluated by three study sites on 152 Enterococcus faecalis, 100 Staphylococcus spp. and 330 Enterobacterales in comparison with the CLSI and EUCAST agar dilution reference method. Referring to FDA performance criteria, the ETEST FO achieved 91.0% of essential (EA) and 99.0% of categorical agreement (CA) for Escherichia coli. In addition, 98.0% EA and 93.4% CA were achieved for E. faecalis, with no very major errors (VME) or major errors (ME). According to EUCAST breakpoints for intravenous fosfomycin use, Enterobacterales and Staphylococcus spp. also met ISO acceptance criteria for EA and CA (EA 91.5%, 94.0%, respectively, and CA 98.0% for both). A VME rate of 8.8% was observed for Enterobacterales but the MICs were within EA. A trend to predict lower MICs for Citrobacter spp., E. coli and Salmonella enterica and to predict higher MICs for Klebsiella pneumoniae MICs was observed, while ETEST FO should not be used for Enterobacter cloacae, because of low EA and a high VME rate. The study results support the efficiency of the novel ETEST FO, making it an easy-to-handle tool as a substitute to the classical agar dilution method.
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Fosfomicina , Agar , Antibacterianos/farmacología , Pruebas Antimicrobianas de Difusión por Disco , Enterococcus faecalis , Escherichia coli , Fosfomicina/farmacología , Humanos , Pruebas de Sensibilidad Microbiana , StaphylococcusRESUMEN
INTRODUCTION: Continuous ambulatory peritoneal dialysis (CAPD)-associated peritonitis remains a major complication in patients on CAPD leading to increased morbidity and mortality. Successful therapy of peritonitis is highly dependent on a positive microbiological culture because narrow spectrum antibiotics are essential to efficiently combat infection. Therefore, this study evaluated the performance of Tween 80 containing media at three different concentrations (0.1%, 1.0% and 2.0%) to increase the pathogen yield from peritoneal fluid in comparison with the standard culture media. MATERIALS AND METHODS: Peritoneal fluid samples (n=121) obtained from CAPD patients suspected of peritonitis at Hospital Kuala Lumpur were analysed macroscopically and microscopically prior to culture. All samples were cultured on seven different culture media, including sheep blood agar, MacConkey agar, Sabouraud dextrose agar, brain heart infusion agar and Tween 80 incorporated blood agar. All plates were incubated at an optimum temperature up to 48 hours. RESULTS AND CONCLUSION: Among all the culture media investigated, 0.1% to 2.0% Tween 80 incorporated blood agar yielded the highest positive culture (23/121) in comparison with all other standard media, thus lowering the negative culture rate among CAPD patients. Statistical analysis by Chi Square revealed significant differences (p <0.001) between the three concentrations of Tween 80 tested in this study. Among the three different concentrations of Tween 80 optimised in this study, blood agar containing 0.1% Tween 80 generated the best results, achieved by optimum growth of all Gram-positive organisms, Gram-negative organisms and yeast cells simultaneously. Using a small amount of detergent at low cost significantly increased the pathogen yield during CAPD-associated peritonitis.
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Diálisis Peritoneal Ambulatoria Continua , Agar , Líquido Ascítico , Medios de Cultivo , Hospitales , Humanos , Diálisis Peritoneal Ambulatoria Continua/efectos adversos , Peritonitis/etiología , Polisorbatos/efectos adversosRESUMEN
AIMS: In the previous work, following a pressure treatment with wild-type Staphylococcus aureus, we obtained piezotolerant isolates showing altered phenotypic characteristics. This work focuses on understanding the genetic background of their altered phenotype. METHODS AND RESULTS: AK23, a representative piezotolerant isolate was subjected to DNA microarrays, corroborated by PCR product sequencing and revealed 10-gene deletion. All other piezotolerant isolates possessed the mutation encompassing the region from SAR0665 to SAR0674 genes (9351 bp) which was most likely the result of recombination between two homologous loci (ATTGCGGGTG) present in both genes. RNA microarray transcriptomic analysis showed that due to partial deletion of the low-affinity phosphate transporter pitA, the high-affinity PhoU-PstABCS operon was upregulated in AK23 which could be the reason for piezotolerance. Furthermore, AK23 showed low levels of the virulence gene regulator rnaIII resulting in the downregulation of several agr system genes explaining the impaired virulence characteristics of the mutant. CONCLUSIONS: Naturally occurring mutations can result in piezotolerance which can be of a concern for high hydrostatic pressure-treated foods. SIGNIFICANCE AND IMPACT OF THE STUDY: A locus has been identified in piezotolerant S. aureus mutants providing insight into possible mechanisms associated with phenotypic characteristics of S. aureus. Further work should study each individual gene of the locus.
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Mutación , Presión , Staphylococcus aureus/fisiología , Estrés Fisiológico/genética , Proteínas Bacterianas/genética , Manipulación de Alimentos , Regulación Bacteriana de la Expresión Génica , Operón , ARN Bacteriano/genética , ARN Bacteriano/metabolismo , Staphylococcus aureus/genética , Staphylococcus aureus/patogenicidad , Virulencia/genéticaRESUMEN
Hospital-acquired infections (HAIs) are a cause of continuously increasing morbidity and mortality. Most of these infections are caused by a limited set of bacterial species, which share the capability to efficiently spread from patient to patient and to easily acquire antibiotic resistance determinants. This renders correct and rapid species identification and antibiotic susceptibility testing (AST) important and underscores the relevance of bacterial epidemiological typing. The latter is needed for the sensitive detection and exact tracing of nosocomial spread of these potentially multidrug-resistant microorganisms (MDRO). Many microbial typing technologies have been developed and put to some level of executive practice, but it seems that the continued evolution in methodology has currently reached an apex: there is likely to be scientific and practical consensus on the ultimate typing potential of bacterial whole-genome sequencing (WGS). The possibility to perform pan-genomic nucleotide-to-nucleotide comparisons between strains belonging to a single species and to detect even minute changes in nucleotide order will identify closely related organisms, while upon accumulation of such mutations, independent descend can be assumed. Calibration of difference levels [i.e. number of single nucleotide polymorphisms (SNPs)] into categories of inter-strain relatedness needs to be performed in order to generate robust, portable typing schemes. Here, we will briefly discuss the state of affairs regarding bacterial epidemiology based upon WGS, its relatedness with the nomenclature of former typing approaches and the continuing need for a global typing language.
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Infección Hospitalaria/epidemiología , Infección Hospitalaria/microbiología , Metagenoma , Metagenómica , Microbiota/genética , Bacterias/clasificación , Bacterias/genética , Técnicas de Tipificación Bacteriana/métodos , Infección Hospitalaria/prevención & control , Brotes de Enfermedades , Genoma Bacteriano , Humanos , Metagenómica/métodos , Epidemiología Molecular , Secuenciación Completa del GenomaRESUMEN
The humoral immune responses against 46 different staphylococcal antigens in 27 bacteremia patients infected by clonally related methicillin-resistant Staphylococcus aureus (MRSA) strains of a single sequence type (ST) 239 were investigated. A group of non-infected patients (n = 31) hospitalized for different reasons served as controls. All strains were confirmed as ST 239 by S. aureus and mecA-specific PCR, spa, and multi-locus sequence typing (MLST). In each bacteremia patient, a unique pattern of S. aureus antigen-specific immune responses after infection was observed. Antibody levels among bacteremia patients were significantly higher than controls for HlgB (P = 0.001), LukD (P = 0.009), LukF (P = 0.0001), SEA (P = 0.0001), SEB (P = 0.011), SEC (P = 0.010), SEQ (P = 0.049), IsaA (P = 0.043), IsdA (P = 0.038), IsdH (P = 0.01), SdrD (P = 0.001), SdrE (P = 0.046), EsxA (P = 0.0001), and SA0104 (P = 0.0001). On the other hand, the antibody levels were significantly higher among controls for SSL3 (P = 0.009), SSL9 (P = 0.002), and SSL10 (P = 0.007) when the IgG level on the day of infection was compared with that measured on the day of admission. Diversity was observed in the immune response against the antigens. However, a set of antigens (IsaA, IsdA, IsdH, SdrD, and HlgB) triggered a similar type of immune response in different individuals. We suggest that these antigens could be considered when developing a multi-component (passive) vaccine. SEA and/or its specific antibodies seem to play a critical role during ST239 MRSA bacteremia and SEA-targeted therapy may be a strategy to be considered.
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Anticuerpos Antibacterianos/sangre , Antígenos Bacterianos/inmunología , Bacteriemia/inmunología , Staphylococcus aureus Resistente a Meticilina/clasificación , Staphylococcus aureus Resistente a Meticilina/inmunología , Infecciones Estafilocócicas/inmunología , Adulto , Anciano , Anciano de 80 o más Años , Anticuerpos Antibacterianos/inmunología , Bacteriemia/microbiología , Proteínas Bacterianas/genética , Infección Hospitalaria/diagnóstico , Infección Hospitalaria/microbiología , Femenino , Hospitales , Humanos , Inmunidad Humoral/inmunología , Masculino , Staphylococcus aureus Resistente a Meticilina/genética , Staphylococcus aureus Resistente a Meticilina/patogenicidad , Persona de Mediana Edad , Epidemiología Molecular , Tipificación de Secuencias Multilocus , Proteínas de Unión a las Penicilinas/genética , Infecciones Estafilocócicas/microbiología , Factores de Virulencia/inmunología , Adulto JovenRESUMEN
Timely diagnosis of tuberculosis (TB), caused by Mycobacterium tuberculosis (MTB), is only achieved for ~58% cases. An improved, accurate, time- and cost-effective method for bacteriological confirmation of MTB is necessary. We evaluated Mycotube, a new variant of Lowenstein-Jensen (LJ) culture medium, by comparing it with Mycobacterium Growth Indicator Tube (MGIT) 960 (gold standard), local LJ, and bioMérieux LJ-T in terms of isolation rate and time-to-growth. Pulmonary and extra-pulmonary samples from treatment-naïve suspects (n = 207) were decontaminated by the N-acetyl-L-cysteine-sodium hydroxide method and used to inoculate the four media. Subjective and objective parameters were used for evaluation. Mycotube yielded 140 positive results, compared to 162, 69, and 141 from MGIT, local LJ, and LJ-T, respectively. Of these, 139 (67%) were true-positive results and 1 (0.5%) was false-positive. The mean time-to-growth detection was 17.4 days for Mycotube, compared to 14.5, 28.1, and 16.5 days for MGIT, local LJ, and LJ-T, respectively. The mean time-to-growth for local LJ significantly differed from that for MGIT, but not those for LJ-T and Mycotube. No contamination was observed. Mycotube had a sensitivity of 85.8% and a specificity of 97.8% as compared to MGIT. Mycotube offers good results, comparable with those observed for conventional LJ. It requires only basic laboratory infrastructure. The overall cost of the test should be nearly three times lower than that of MGIT. Mycotube helps with TB diagnosis and generates pure isolates for drug susceptibility testing.
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Técnicas Bacteriológicas/métodos , Medios de Cultivo/química , Mycobacterium tuberculosis/aislamiento & purificación , Tuberculosis/diagnóstico , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Niño , Preescolar , Errores Diagnósticos , Femenino , Humanos , Masculino , Persona de Mediana Edad , Sensibilidad y Especificidad , Factores de Tiempo , Adulto JovenRESUMEN
Clostridium difficile is the cause of the nosocomial C. difficile infection (CDI). The conventional antibiotics used in CDI therapy are often unsuccessful, and recurrent infections may occur. Biofilm formation by C. difficile is associated with chronic or recurrent infections; biofilms may contribute to virulence and impaired antimicrobial efficacy. Manuka honey, derived from the Manuka tree (Leptospermum scoparium), is known to exhibit antimicrobial properties that are associated with its significant content of methylglyoxal, a natural antibiotic. The aim of the present study was to determine the antimicrobial effect of Manuka honey on clinical C. difficile strains belonging to four prominent polymerase chain reaction (PCR) ribotypes (RTs) (RT017, RT023, RT027 and RT046) and on their biofilm formation in vitro. Minimal inhibitory and bactericidal concentrations (MICs and MBCs, respectively) were determined using the broth dilution method. The biomass of the biofilm and the clearance of C. difficile biofilms by Manuka honey were determined using the crystal violet staining method. The MIC and MBC of Manuka honey for C. difficile strains were equal at 6.25% (v/v). PCR RT027 strains produced more biofilm in vitro than the other examined strains. Manuka honey effectively inhibited biofilm formation by C. difficile strains of different PCR RTs.
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Antiinfecciosos/farmacología , Biopelículas/efectos de los fármacos , Clostridioides difficile/efectos de los fármacos , Clostridioides difficile/crecimiento & desarrollo , Miel , Clostridioides difficile/genética , Clostridioides difficile/aislamiento & purificación , Humanos , Pruebas de Sensibilidad Microbiana , Tipificación MolecularRESUMEN
Recently, plasmid-mediated and, therefore, transferable bacterial polymyxin resistance was discovered in strains from both humans and animals. Such a trait may widely spread geographically, while simultaneously crossing microbial species barriers. This may ultimately render the "last resort" polymyxin antibiotics therapeutically useless. Colistin is currently used to treat infections caused by Gram-negative carbapenemase producers and colistin resistance may lead to practical pan-antibiotic resistance. We here analyzed the medical and diagnostic consequences of (emerging) colistin resistance and propose pathways toward adequate diagnostics for timely detection of both asymptomatic carriage and infection. Culture-based testing using chromogenic and selective media for screening clinical (and veterinary) specimens may constitute key tools for that purpose. Relevant molecular tests are also discussed.
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Antibacterianos/farmacología , Colistina/farmacología , Farmacorresistencia Bacteriana , Bacterias Gramnegativas/efectos de los fármacos , Infecciones por Bacterias Gramnegativas/tratamiento farmacológico , Infecciones por Bacterias Gramnegativas/microbiología , Animales , Antibacterianos/uso terapéutico , Portador Sano/diagnóstico , Portador Sano/microbiología , Portador Sano/veterinaria , Colistina/uso terapéutico , Transferencia de Gen Horizontal , Bacterias Gramnegativas/aislamiento & purificación , Infecciones por Bacterias Gramnegativas/diagnóstico , Infecciones por Bacterias Gramnegativas/veterinaria , Humanos , PlásmidosRESUMEN
The humoral immune response against 43 staphylococcal antigens was compared among hospitalized patients where none of them had any staphylococcal infection on the day of admission with or without nasal Staphylococcus aureus carriage. Fifty-nine carriers and 59 matched non-carriers were studied. The carriers harbored S. aureus of 35 different spa types, including three t037/ST239 methicillin-resistant S. aureus (MRSA) (5.1%). Among the 118 patients, 31 acquired S. aureus during hospitalization. In colonized and non-colonized patients, unique patterns of S. aureus-specific immune responses were observed. The mean fluorescence indices (MFIs) of antibodies against 36/43 (83.7%) antigens were seen to be elevated among carriers. The MFI among carriers with acquisition was significantly higher for staphylococcal superantigen-like protein 5 (SSL5, p = 0.028) when compared to carriers without acquisition. High antibody levels against staphylococcal enterotoxin A (SEA) among carriers illustrate its role as a superantigen in both infection and colonization. We also report a dynamic immune response in S. aureus-carrying patients against the recently reported formyl peptide receptor-like inhibitory (FLIPr)-like protein. In the current study, the dynamics of antibodies against staphylococcal antigens among carrier patients seem quite similar to non-carrier patients. To better understand the dynamic immunogenicity during S. aureus infection and colonization, artificial colonization studies and investigation of the changes in the levels of antibodies against other staphylococcal antigens are recommended.
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Anticuerpos Antibacterianos/sangre , Portador Sano/inmunología , Inmunidad Humoral , Infecciones Estafilocócicas/inmunología , Staphylococcus aureus/inmunología , Staphylococcus aureus/aislamiento & purificación , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Antígenos Bacterianos/inmunología , Portador Sano/microbiología , Femenino , Humanos , Masculino , Persona de Mediana Edad , Mucosa Nasal/microbiología , Infecciones Estafilocócicas/microbiología , Adulto JovenRESUMEN
The capacity of absorbent beads in BacT/ALERT® FA Plus and BACTEC® Aerobic/F Plus blood culture bottles to bind and neutralize antibiotics was compared. Binding was established using reverse-phase HPLC, and inactivation was based on the recovery of susceptible test stains from simulated blood cultures. The FA Plus medium demonstrated more rapid and better overall binding kinetics for each drug tested, resulting in significantly better overall recovery rates. Differences in time to detection favored the FA Plus medium for three drug/organism combinations and Aerobic/F Plus for two.
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Adsorción , Antibacterianos/aislamiento & purificación , Cultivo de Sangre/métodos , Medios de Cultivo/química , Manejo de Especímenes/métodos , Antibacterianos/análisis , Cromatografía Líquida de Alta Presión , Humanos , Cinética , Factores de TiempoRESUMEN
Staphylococcus aureus might amplify symptoms in chronic inflammatory skin diseases. This study evaluates skin and mucosal colonization with S. aureus in patients with psoriasis, acne and rosacea. A systematic literature search was conducted. Both odds ratios (OR) for colonization in patients versus controls and the prevalence of colonization in patients are reported. Fifteen articles about psoriasis and 13 about acne (12 having a control group) were included. No study in rosacea met our inclusion criteria. For psoriasis, one study out of three controlled studies showed increased skin colonization (OR 18.86; 95 % confidence interval [CI] 2.20-161.99). Three out of the five studies that reported on nasal colonization showed significant ORs varying from 1.73 (95 % CI 1.16-2.58) to 14.64 (95 % CI 2.82-75.95). For acne one of the three studies that evaluated skin colonization reported a significant OR of 4.16 (95 % CI 1.74-9.94). A relation between nasal colonization and acne was not found. Limitations in study design and low sample sizes should be taken into consideration when interpreting the results. Colonisation with S. aureus seems to be increased in patients with psoriasis. This bacterial species, known for its potential to induce long-lasting inflammation, might be involved in psoriasis pathogenesis. Information on acne is limited. Prospective controlled studies should further investigate the role of S. aureus in chronic inflammatory skin diseases.
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Acné Vulgar/microbiología , Portador Sano , Psoriasis/microbiología , Rosácea/microbiología , Infecciones Estafilocócicas/microbiología , Staphylococcus aureus , Acné Vulgar/complicaciones , Estudios de Casos y Controles , Humanos , Membrana Mucosa/microbiología , Oportunidad Relativa , Psoriasis/complicaciones , Rosácea/complicaciones , Piel/microbiología , Infecciones Estafilocócicas/complicacionesRESUMEN
We cultured enterococci from urinary tract infections in Iranian hospitals. Seven different Enterococcus species (E. raffinosus, E. durans, E. hirae, E. avium, E. mundtii, E. faecium and E. faecalis) were found. Seven strains were vancomycin resistant, leading to an overall vancomycin resistance rate of 3.9%. The enterococcal infection rate was high and vancomycin-resistant enterococci incidence low. We report the first vanA-positive E. mundtii urinary tract infections.
RESUMEN
BACKGROUND: Staphylococcus aureus is increasingly implicated as a possible causal factor in the pathogenesis of atopic dermatitis (AD). However, the reported prevalence rates of skin and nasal colonization in the literature vary widely. OBJECTIVES: This study evaluates the prevalence and odds of skin and nasal colonization with S. aureus in patients with AD. METHODS: A systematic literature search was conducted. Odds ratios (ORs) for colonization in patients vs. controls and the prevalence of colonization in patients were pooled using the random-effects model. RESULTS: Overall, 95 observational studies were included, of which 30 had a control group. The Newcastle-Ottawa Scale was used to assess study quality, with the majority of studies being of fair to poor quality. Patients with AD were more likely to be colonized with S. aureus than healthy controls [OR 19·74, 95% confidence interval (CI) 10·88-35·81]. Differences were smaller in nonlesional skin (OR 7·77, 95% CI 3·82-15·82) and in the nose (OR 4·50, 95% CI 3·00-6·75). The pooled prevalence of S. aureus colonization among patients was 70% for lesional skin, 39% for nonlesional skin and 62% for the nose. In lesional skin, meta-regression showed that the prevalence of colonization increased with disease severity. Study heterogeneity should be taken into consideration when interpreting the results. CONCLUSIONS: These results demonstrate the importance of colonization with S. aureus in AD. Further evaluation of the mechanisms by which S. aureus influences inflammation is required in addition to the development of targeted strategies to decrease skin and nasal S. aureus load.
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Dermatitis Atópica/microbiología , Infecciones Cutáneas Estafilocócicas/epidemiología , Staphylococcus aureus , Dermatitis Atópica/epidemiología , Humanos , Enfermedades Nasales/epidemiología , Enfermedades Nasales/microbiología , Estudios Observacionales como Asunto , PrevalenciaRESUMEN
Development of new antibiotics is declining whereas antibiotic resistance is rising, heralding a post-antibiotic era. Antimicrobial peptides such as gramicidin S (GS), exclusively topically used due to its hemolytic side-effect, could still be interesting as therapeutic compounds. By modifying the amino-acid composition of GS, we synthesized GS analogues. We now show that derivative VK7 has a lower MIC (7.8-31.2 µg/ml, median 15.6 µg/ml) against strains of multi-drug resistant (MDR) Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa than GS has (3.9-62.5 µg/ml, median 31.3 µg/ml). Low MICs for both VK7 and GS were observed for Staphylococcus aureus and Enterococcus faecium. VK7 showed reduced haemolysis and less lactate dehydrogenase release. All compounds were fully bactericidal at MIC values. Modification of GS enables production of novel derivatives potentially useful for systemic treatment of human infections.
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Antibacterianos/química , Antibacterianos/farmacología , Gramicidina/química , Gramicidina/farmacología , Antibacterianos/toxicidad , Línea Celular Tumoral , Eritrocitos/efectos de los fármacos , Eritrocitos/metabolismo , Gramicidina/toxicidad , Hemólisis , Humanos , Lactato Deshidrogenasas/biosíntesis , Pruebas de Sensibilidad Microbiana , Estructura MolecularRESUMEN
Typing of bacterial isolates using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) potentially provides an efficient on-site method to monitor the spread of antibiotic-resistant bacteria and rapidly detect outbreaks. We compared MALDI-MS typing results to those of amplified fragment length polymorphism (AFLP) in a collection of 52 ESBL-producing Escherichia coli, isolated in a Dutch nursing home with an on-going outbreak of ST131 E. coli. Specific MALDI types were defined based on spectral data from four replicate colony samples of isolates grown on Columbia agar using multivariate statistical procedures. Type-specific superspectra were computed for four E .coli MALDI-types and tested for the potential of rapid and automated typing. The effect of different incubation conditions on typing performance was tested by analysing five isolates incubated for 24 h and 48 h on five different media. Types defined based on MALDI spectra were largely in agreement with the AFLP results, although some MALDI types comprised of more than one AFLP type. In particular, isolates belonging to ST131 showed distinct mass patterns. The proportion of isolates correctly assigned was substantially lower for isolates incubated on Sabouraud-dextrose and Drigalski agars for 24 h, and for those incubated for 48 h (all media). Our results show that the identification of type-specific peaks potentially allows direct typing of isolates belonging to specific clonal lineages. Both incubation time and media affected type assignment, suggesting that there is a need for a careful standardization of incubation time and culturing conditions when developing MALDI-typing schemes for E. coli.
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Análisis del Polimorfismo de Longitud de Fragmentos Amplificados , Escherichia coli/clasificación , Escherichia coli/genética , Espectrometría de Masa por Láser de Matriz Asistida de Ionización Desorción , beta-Lactamasas/genética , Análisis del Polimorfismo de Longitud de Fragmentos Amplificados/métodos , Análisis por Conglomerados , Infecciones por Escherichia coli/epidemiología , Infecciones por Escherichia coli/microbiología , Humanos , Reproducibilidad de los Resultados , Espectrometría de Masa por Láser de Matriz Asistida de Ionización Desorción/métodosRESUMEN
Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) has been introduced as an identification procedure for bacteria and fungi. The MALDI-TOF MS-based analysis of resistance to ß-lactam antibiotics has been applied to detect hydrolysis of carbapenems by different bacterial strains. However, the detection of enzymatic carbapenem degradation by MALDI-TOF MS lacks well-standardized protocols and several methods and models of interpretation using different calculations of ratio-of-peak intensities have been described in the literature. Here, we used faropenem and ertapenem hydrolysis as model compounds. In an attempt to propose a universal protocol, the hydrolysis was regularly monitored during 24 h using well-characterized bacterial strains producing different types of carbapenemases (KPC, IMP, NDM, VIM, and OXA-48). Variable responses and different timing for detectable hydrolysis, depending on the enzyme produced, were observed. KPC degrades its template antibiotics very quickly (15 min for some KPC producers) compared to other types of enzymes (more than 90 min for other enzymes). Prior bacterial lysis was shown to be of no interest in the modulation or optimization of the hydrolytic kinetics. The adequate detection of carbapenem hydrolysis would, therefore, require several MALDI-TOF MS readouts for the timely detection of rapid hydrolysis without missing slow hydrolysis. This enzymatic constraint limits the implementation of a standard protocol in routine microbiology laboratories.
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Antibacterianos/metabolismo , Proteínas Bacterianas/análisis , Espectrometría de Masa por Láser de Matriz Asistida de Ionización Desorción/métodos , beta-Lactamasas/análisis , Ertapenem , Hongos , Humanos , Hidrólisis , Cinética , Factores de Tiempo , beta-Lactamas/metabolismoRESUMEN
We performed a prospective observational study in a clinical setting to test the hypothesis that prior colonization by a Staphylococcus aureus strain would protect, by colonization interference or other processes, against de novo colonization and, hence, possible endo-infections by newly acquired S. aureus strains. Three hundred and six patients hospitalized for >7 days were enrolled. For every patient, four nasal swabs (days 1, 3, 5, and 7) were taken, and patients were identified as carriers when a positive nasal culture for S. aureus was obtained on day 1 of hospitalization. For all patients who acquired methicillin-resistant S. aureus (MRSA) or methicillin-susceptible S. aureus via colonization and/or infection during hospitalization, strains were collected. We note that our study may suffer from false-negative cultures, local problems with infection control and hospital hygiene, or staphylococcal carriage at alternative anatomical sites. Among all patients, 22% were prior carriers of S. aureus, including 1.9% whom carried MRSA upon admission. The overall nasal staphylococcal carriage rate among dermatology patients was significantly higher than that among neurosurgery patients (n = 25 (55.5%) vs. n = 42 (16.1%), p 0.005). This conclusion held when the carriage definition included individuals who were nasal culture positive on day 1 and day 3 of hospitalization (p 0.0001). All MRSA carriers were dermatology patients. There was significantly less S. aureus acquisition among non-carriers than among carriers during hospitalization (p 0.005). The mean number of days spent in the hospital before experiencing MRSA acquisition in nasal carriers was 5.1, which was significantly lower than the score among non-carriers (22 days, p 0.012). In conclusion, we found that nasal carriage of S. aureus predisposes to rather than protects against staphylococcal acquisition in the nose, thereby refuting our null hypothesis.
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Portador Sano/epidemiología , Portador Sano/microbiología , Mucosa Nasal/microbiología , Infecciones Estafilocócicas/epidemiología , Infecciones Estafilocócicas/microbiología , Staphylococcus aureus/clasificación , Staphylococcus aureus/aislamiento & purificación , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Femenino , Estudios de Seguimiento , Humanos , Masculino , Persona de Mediana Edad , Prevalencia , Estudios Prospectivos , Adulto JovenRESUMEN
The laboratory diagnosis of tuberculosis usually relies on culture-based isolation of the causative Mycobacterium tuberculosis bacteria. We developed and evaluated the performance of MOD9, a new blood-free derivative of the MOD4 solid medium on which we previously reported for the isolation and culture of mycobacteria. First, inoculation of Lowenstein-Jensen medium with 21 M. tuberculosis isolates at 10(5), 10(3), and 10 CFU yielded colonies in 5.7 ± 1.5 days, 7.6 ± 0.8 days, and 10.8 ± 1.7 days versus 1.5 ± 0.4 days, 3.5 ± 0.6 days, and 4.9 ± 1 days in MOD9 (P < 0.05, Student's t test). Further, the time to detectable growth of M. tuberculosis was measured on MOD9 and Lowenstein-Jensen media after duplicate inoculation of 250 clinical specimens decontaminated with 0.7% chlorhexidine. The contamination rate was 1.6% (4/250) on MOD9 versus 4.4% (11/250) on Lowenstein-Jensen medium (P = 0.11, Fisher's exact test). Chlorhexidine-MOD9 yielded 38/250 (15.2%) isolates versus 32/250 (12.8%) isolates for the chlorhexidine-LJ (P = 0.5195, Fisher's exact test). All together, eight M. tuberculosis isolates were cultured solely from chlorhexidine-MOD9, and two M. tuberculosis isolates were cultured solely from chlorhexidine-LJ. The time to detection was 9.8 ± 3.9 (range, 5 to 18) days for chlorhexidine-MOD9 versus 17.4 ± 5.9 (range, 10 to 35) days for chlorhexidine-LJ (P < 0.05, Student's t test). These data indicate the superiority of the MOD9 medium over the standard LJ medium following chlorhexidine decontamination for the recovery of M. tuberculosis.
Asunto(s)
Técnicas Bacteriológicas/métodos , Medios de Cultivo/química , Mycobacterium tuberculosis/crecimiento & desarrollo , Mycobacterium tuberculosis/aislamiento & purificación , Tuberculosis/diagnóstico , Humanos , Sensibilidad y Especificidad , Factores de TiempoRESUMEN
Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-ToF MS) has been introduced in clinical routine microbiology laboratories. For the rapid diagnosis of urinary tract infections, culture-independent methods prior MALDI-mediated identification have been described. Here, we describe a comparison of three of these methods based on their performance of bacterial identification and their potential as a routine tool for microbiology labs : (i) differential centrifugation, (ii) urine filtration and (iii) a 5-h bacterial cultivation on solid culture media. For 19 urine samples, all methods were directly compared and correct bacterial species identification by MALDI was used as performance indicator. A higher percentage of correct MALDI identification was obtained after filtration (78.9 %) and the growth-based method (84.2 %) as compared to differential centrifugation (68.4 %). Additional testing of 76 mono-microbial specimens (bacteriuria > 10(5) CFU/mL) confirmed the good performance of short growth with a 90.8 % correct MALDI score, with a potentially better fit to the routine workflow of microbiology labs.