Antimicrobial Susceptibility Of Strains Research Articles

Application of MALDI-TOF MS to Identify and Detect Antimicrobial-Resistant Streptococcus uberis Associated with Bovine Mastitis.

Streptococcus uberis is a common bovine mastitis pathogen in dairy cattle. The rapid identification and characterization of antimicrobial resistance (AMR) in S. uberis plays an important role in its diagnosis, treatment, and prevention. In this study, matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) was used to identify S. uberis and screen for potential AMR biomarkers. Streptococcus uberis strains (n = 220) associated with bovine mastitis in northern Thailand were identified using the conventional microbiological methods and compared with the results obtained from MALDI-TOF MS. Streptococcus uberis isolates were also examined for antimicrobial susceptibility using a microdilution method. Principal component analysis (PCA) and the Mann-Whitney U test were used to analyze the MALDI-TOF mass spectrum of S. uberis and determine the difference between antimicrobial-resistant and -susceptible strains. Using MALDI-TOF MS, 73.18% (161/220) of the sampled isolates were identified as S. uberis, which conformed to the identifications obtained using conventional microbiological methods and PCR. Using PCR, antimicrobial-resistant strains could not be distinguished from antimicrobial-susceptible strains for all three antimicrobial agents, i.e., tetracycline, ceftiofur, and erythromycin. The detection of spectral peaks at 7531.20 m/z and 6804.74 m/z was statistically different between tetracycline- and erythromycin-resistant and susceptible strains, respectively. This study demonstrates a proteomic approach for the diagnosis of bovine mastitis and potentially for the surveillance of AMR among bovine mastitis pathogens.

Characterisation of Yersinia Enterocolitica Strains Isolated from Wildlife in the Northwestern Italian Alps.

IntroductionYersiniosis is a zoonosis causing gastroenteritis, diarrhoea, and occasionally reactive arthritis and septicaemia. Cases are often linked to meat consumption and the most common aetiological agent is the Gram-negative bacilliform Yersinia enterocolitica bacterium. The occurrence of Yersinia spp. among wild animals has mostly been studied in wild boar, but it has seldom been in other species.Material and MethodsA total of 1,868 faecal samples from animals found dead or hunted were collected between 2015 and 2018 in the Valle d’Aosta region of the northwestern Italian Alps. Alpine ibex faecal samples were collected during a health monitoring program in 2018. Bacteria were isolated via PCR and confirmed as Y. enterocolitica biochemically. Strain antimicrobial susceptibility was tested by Kirby–Bauer disc diffusion, and the presence of virulence factors and antimicrobial resistance genes was investigated using whole-genome sequencing.ResultsYersinia enterocolitica strains of biotype 1A were detected in six faecal samples from red deer (0.93%), roe deer (0.49%) and red foxes (0.7%). Strains found in beech martens (3.57%) and Alpine ibex (2.77%) belonged to biotypes 1B and 5, respectively and harboured the pYPTS01 plasmid that had only been detected in Y. pseudotuberculosis PB1/+. All the isolates were resistant to ampicillin and erythromycin.ConclusionThe biovar 1A strains exhibited different virulence factors and behaved like non-pathogenic commensals. The strain from an Alpine ibex also harboured the self-transmissible pYE854 plasmid that can mobilise itself and the pYPTS01 plasmid to other strains. The beech marten could be considered a sentinel animal for Y. enterocolitica. Phenotypic resistance may account for the ability of all the strains to resist β-lactams.

Virulome and genome analyses identify associations between antimicrobial resistance genes and virulence factors in highly drug-resistant Escherichia coli isolated from veal calves.

Food animals are known reservoirs of multidrug-resistant (MDR) Escherichia coli, but information regarding the factors influencing colonization by these organisms is lacking. Here we report the genomic analysis of 66 MDR E. coli isolates from non-redundant veal calf fecal samples. Genes conferring resistance to aminoglycosides, β-lactams, sulfonamides, and tetracyclines were the most frequent antimicrobial resistance genes (ARGs) detected and included those that confer resistance to clinically significant antibiotics (blaCMY-2, blaCTX-M, mph(A), erm(B), aac(6’)Ib-cr, and qnrS1). Co-occurrence analyses indicated that multiple ARGs significantly co-occurred with each other, and with metal and biocide resistance genes (MRGs and BRGs). Genomic analysis also indicated that the MDR E. coli isolated from veal calves were highly diverse. The most frequently detected genotype was phylogroup A-ST Cplx 10. A high percentage of isolates (50%) were identified as sequence types that are the causative agents of extra-intestinal infections (ExPECs), such as ST69, ST410, ST117, ST88, ST617, ST648, ST10, ST58, and ST167, and an appreciable number of these isolates encoded virulence factors involved in the colonization and infection of the human urinary tract. There was a significant difference in the presence of multiple accessory virulence factors (VFs) between MDR and susceptible strains. VFs associated with enterohemorrhagic infections, such as stx, tir, and eae, were more likely to be harbored by antimicrobial-susceptible strains, while factors associated with extraintestinal infections such as the sit system, aerobactin, and pap fimbriae genes were more likely to be encoded in resistant strains. A comparative analysis of SNPs between strains indicated that several closely related strains were recovered from animals on different farms indicating the potential for resistant strains to circulate among farms. These results indicate that veal calves are a reservoir for a diverse group of MDR E. coli that harbor various resistance genes and virulence factors associated with human infections. Evidence of co-occurrence of ARGs with MRGs, BRGs, and iron-scavenging genes (sit and aerobactin) may lead to management strategies for reducing colonization of resistant bacteria in the calf gut.

Comparison of in Vitro Antimicrobial Efficacy of Ceftolozane-Tazobactam and Ceftazidime-Avibactam Combination Against Carbapenem-Resistant Enterobacteriaceae Species Isolated from Various Clinical Specimens

Objective: The increase in resistant Gram-negative bacteria is a major concern and has led to difficulties in the treatment of infections. The aim of this study was to compare the in vitro efficacy of CLZ-TAZ and CAZ-AVB combinations against carbapenem-resistant Enterobacteriaceae strains.
 
 Methods: 80 carbapenem-resistant Enterobacteriaceae species isolated from various samples sent to our laboratory were included in the study. Identification and antimicrobial susceptibility of strains were performed using automated systems. The presence of carbapenemases in all isolates was tested using the CarbaNP test and the carbapenem inactivation method. The presence of carbapenemase genes was tested by multiplex PCR.
 
 Results: The presence of carbapenemases was detected in 60 % E. coli isolates and in 78.5% K. pneumoniae isolates via phenotypic tests. OXA-48 enzyme was found in 73.7% of isolates containing carbapenemase. The second most common enzyme was NDM.The assessment of the efficacy of the β-lactam/β-lactamase inhibitor combinations against CRE isolates revealed that the activity of CAZ-AVB (77%) was higher than CLZ-TAZ (48%).
 
 Conclusion: Our findings suggest that CAZ-AVB and CLZ-TAZ may be promising in the treatment of infections caused by CRE strains. Sensitivity rates were higher with ceftazidime-avibactam than with ceftolozane-tazobactam. The data obtained in this study will contribute to the clinical use of these agents in our country.

Proteomic Signatures of Antimicrobial Resistance in Yersinia pestis and Francisella tularensis.

Antimicrobial resistance (AMR) is a well-recognized, widespread, and growing issue of concern. With increasing incidence of AMR, the ability to respond quickly to infection with or exposure to an AMR pathogen is critical. Approaches that could accurately and more quickly identify whether a pathogen is AMR also are needed to more rapidly respond to existing and emerging biological threats. We examined proteins associated with paired AMR and antimicrobial susceptible (AMS) strains of Yersinia pestis and Francisella tularensis, causative agents of the diseases plague and tularemia, respectively, to identify whether potential existed to use proteins as signatures of AMR. We found that protein expression was significantly impacted by AMR status. Antimicrobial resistance-conferring proteins were expressed even in the absence of antibiotics in growth media, and the abundance of 10–20% of cellular proteins beyond those that directly confer AMR also were significantly changed in both Y. pestis and F. tularensis. Most strikingly, the abundance of proteins involved in specific metabolic pathways and biological functions was altered in all AMR strains examined, independent of species, resistance mechanism, and affected cellular antimicrobial target. We have identified features that distinguish between AMR and AMS strains, including a subset of features shared across species with different resistance mechanisms, which suggest shared biological signatures of resistance. These features could form the basis of novel approaches to identify AMR phenotypes in unknown strains.

Trends in antimicrobial susceptibility of salmonella recovered from cattle diagnostic samples in Ohio

Salmonella enterica is an important cause of illness and death in humans. There has been a great deal of efforts to reduce its impact; yet Salmonella infections continue to burden the health of U.S. consumers more than any other foodborne pathogen. Salmonellosis is also an important cause of disease in cattle, causing diarrhea, dehydration, depression, fever, decreased milk production, and anorexia. Surveillance for antimicrobial resistance within healthy food animal populations captures predominantly susceptible Salmonella serovars that are infrequent causes of human illness; however, data from cattle diagnostic submissions can be used to capture trends in antimicrobial susceptibility of strains with a higher public health relevance. Our objective was to evaluate trends in antimicrobial susceptibility of Salmonella recovered from diagnostic samples from clinically ill cattle submitted to the Ohio Department of Agriculture between 2006 and 2017.

Reduced susceptibility in leptospiral strains of bovine origin might impair antibiotic therapy.

Leptospirosis is a worldwide zoonotic disease determined by pathogenic spirochetes of the genus Leptospira. The control of bovine leptospirosis involves several measures including antibiotic treatment of carriers. Despite its importance, few studies regarding antimicrobial susceptibility of strains from bovine origin have been conducted. The aim of this study was to determine the in vitro susceptibility of Leptospira strains obtained from cattle in Rio de Janeiro, Brazil, against the main antibiotics used in bovine veterinary practice. A total of 23 Leptospira spp. strains were investigated for minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) using broth macrodilution. At the species level, there were not differences in MIC susceptibility except for tetracycline (P < 0.05). Nevertheless, at the serogroup level, differences in MIC were observed among Sejroe strains, mainly for ceftiofur, doxycycline and in MBC for streptomycin (P < 0.05). One strain presented MBC values above maximum plasmatic concentration described for streptomycin and was classified as presenting reduced susceptibility. Efficacy of antimicrobial therapy on bovine leptospirosis could be compromised due to occurrence of infection by Leptospira strains presenting reduced susceptibility.

Antimicrobial resistance and outcomes of community-onset bacterial bloodstream infections in patients with type 2 diabetes.

Antimicrobial resistance of bacterial pathogens in the diabetic population with infection is seldom investigated. This study evaluated the antimicrobial resistance and outcomes of community-onset bloodstream infections (CO-BSIs) in patients with diabetes. From 2007-2014, 1271 monomicrobial CO-BSIs and 178 polymicrobial CO-BSIs were identified in patients with type 2 diabetes from three teaching hospitals in Taiwan. Antimicrobial-resistant strains of the ten most prevalent bacterial pathogens in monomicrobial CO-BSIs were recorded and were defined according to individual drug resistance. The 30-day mortality rate and factors associated with outcome were analysed. Antimicrobial-resistant strains were found in 33.7% (379/1125) of monomicrobial CO-BSIs involving the 10 most prevalent pathogens. The leading pathogens in these monomicrobial CO-BSIs were Staphylococcus spp. (33.8%; 430/1271), Escherichia coli (20.9%; 266/1271) and Klebsiella spp. (9.6%; 122/1271); antimicrobial-resistant strains accounted for 61.9%, 18.4% and 10.7% of each, respectively. A higher overall 30-day mortality rate was observed for patients infected by antimicrobial-resistant strains compared with antimicrobial-susceptible strains (9.5% vs. 5.5%; P=0.011, log-rank test). A lower serum albumin level was a predictor of mortality after adjusting for antimicrobial-resistant strains and C-reactive protein level. Antimicrobial-resistant bacterial pathogens pose a serious threat to diabetic patients with CO-BSIs owing to a higher risk of mortality.

Vancomycin and high-level aminoglycoside resistance in Enterococcus species

The aim of the study was to investigate vancomycin and high-level aminoglycoside resistance (HLAR) in &lt;em&gt;Enterococcus&lt;/em&gt; species by phenotypic and genotypic methods. A hundred &lt;em&gt;Enterococcus&lt;/em&gt; strains were included in the study. Antimicrobial susceptibilities of strains were investigated by automated system, betalactamase production was investigated by nitrocefin disks, vancomycin resistance and HLAR were investigated by gradient diffusion method (GDM) and disk diffusion method, respectively. For detection of vancomycin and high-level gentamicin resistance (HLGR) genes, polymerase chain reaction was used. Teicoplanin linezolid, vancomycin, ampicillin, penicillin are the most susceptible antibiotics and strains were detected not to produce beta lactamase. Vancomycin resistance was detected in ten isolates by automated system and in only five isolates by GDM. Five isolates carrying &lt;em&gt;VanA&lt;/em&gt; gene were determined. The ratio of HLGR and high-level streptomycin resistance was found 40 and 63% respectively. &lt;em&gt;aac (6’)-1eaph (2’’)-1a&lt;/em&gt; gene was detected in 58% of strains. &lt;em&gt;E. faecium&lt;/em&gt; strains were found more resistant to the antibiotics than the other species. Beta lactamase was detected in none of strains. The automated system detected vancomycin resistance in more strains than GDM. Therefore it is concluded that strains, which were detected to be resistant to vancomycin, should be confirmed by GDM. The ratio of &lt;em&gt;VanA&lt;/em&gt; gene in strains is consistent with other studies. The HLAR ratio was found in about half of strains. The ratio of&lt;em&gt; aac(6’)-1e-aph(2’’)-1a&lt;/em&gt; gene, which is the most reported gene in our country and other countries and one of the HLGR genes investigated in our study, was detected 58%.

Methicillin-resistant Staphylococcus aureus in Stockholm, Sweden: Molecular epidemiology and antimicrobial susceptibilities to ceftaroline, linezolid, mupirocin and vancomycin in 2014

Methicillin-resistant Staphylococcus aureus (MRSA) is a public health problem worldwide. The aim of the present study was to investigate the molecular epidemiology and antimicrobial susceptibilities of MRSA strains in Stockholm, Sweden in 2014. Pulsed-field gel electrophoresis (PFGE) was used to characterise the strains. Antimicrobial susceptibilities to ceftaroline, linezolid and mupirocin were determined by the disc diffusion method. Etest was used to determine vancomycin susceptibility and to confirm resistance to ceftaroline, mupirocin and linezolid in non-susceptible strains. High-level ceftaroline-resistant strains [minimum inhibitory concentration (MIC)≥4mg/L] were confirmed by the broth microdilution method. spa typing was carried out on strains that were non-susceptible to the antibiotics tested. In total, 743 consecutive non-duplicate MRSA strains recovered in Stockholm in 2014 were investigated. PFGE analysis of the isolates revealed a population with 271 different PFGE patterns and three non-typeable strains. No PFGE type accounted for >10% of all strains. The most common PFGE types were MRSA-00-02 (6.9%) and MRSA-05-02 (4.6%). MRSA-05-02 is a USA300-like strain. The antimicrobial susceptibilities of the strains were as follows: ceftaroline, 98.5%; linezolid, 100%; mupirocin, 99.3%; and vancomycin, 100%. Two strains with spa t001 displayed ceftaroline MICs of 4mg/L. Three strains with spa types t002, t064 and t437 showed high-level mupirocin resistance (MIC>1024mg/L). In conclusion, there was a diverse genetic population among the MRSA isolates and no predominant genotype was found. This study identified a few strains with high-level ceftaroline resistance, high-level mupirocin resistance and high-risk genotypes.

Characterization of Antimicrobial Susceptibility and Its Association with Virulence Genes Related to Adherence, Invasion, and Cytotoxicity in Campylobacter jejuni and Campylobacter coli Isolates from Animals, Meat, and Humans.

The aim of this research was to statistically analyze the association between antimicrobial susceptibility/resistance to erythromycine, gentamicin, ciprofloxacin, and tetracycline and 11 virulence genes associated with adherence, invasion, and cytotoxicity in 528 isolates of Campylobacter coli and Campylobacter jejuni obtained from retail meat and fecal samples from food-producing animals and human patients. A high percentage of Campylobacter strains were resistant to antimicrobials, specifically ciprofloxacin and tetracycline. Moreover, we observed a wide distribution of virulence genes within the analyzed strains. C. jejuni strains were more susceptible to antimicrobials, and showed greater number of virulence genes than C. coli strains. Genes related to invasion capability, such as racR, ciaB, and pldA, were associated with antimicrobial-susceptible strains in both species. The genes cdtA and dnaJ, a citotoxin unit and an adherence-related gene, respectively, were associated with antimicrobial-resistant strains in both species. In conclusion, Campylobacter strains show a statistically significant association between antimicrobial susceptibility and the presence of virulence genes.

Risk factors for hospital-acquired antimicrobial-resistant infection caused by Acinetobacter baumannii.

BackgroundAcinetobacter baumannii can cause serious healthcare-associated infections (HAIs) and the incidence is increasing, with many strains now resistant to multiple antibiotic classes. The aims of this study were to examine factors associated with HAIs caused by antimicrobial-resistant as compared with antimicrobial-susceptible strains of A. baumannii and to investigate trends in the incidence of resistance over time. Electronic data from two U.S. hospitals in a large urban healthcare system in over the years 2006–2012 were used for the analysis. Multiple logistic regression was used to explore risk factors for infection with A. baumannii resistant to ampicillin or ampicillin/sulbactam in the bloodstream, urinary tract, and respiratory tract. The Cochran-Armitage trend test was used to explore resistance trends over time.FindingsA total of 671 adults with first-time A. baumannii infection were included in the analysis; 302 isolates (45 %) were resistant to ampicillin or ampicillin/sulbactam and 369 (55 %) were susceptible. In the multivariable analysis, significant risk factors included longer length of stay prior to infection (Odds Ratio [OR] = 1.03; 95 % Confidence Interval [CI]: 1.01, 1.04), hospital A versus B (OR = 0.35; 95 % CI: 0.13, 0.93), and antibiotic use prior to infection (OR = 2.88; 95 % CI: 1.02, 8.13). Resistance was more common in respiratory infections (OR = 2.96; 95 % CI: 1.04, 8.44). No trend was found between year of infection and resistance.ConclusionsThe risk factors we identified are consistent with previous findings, but we found no evidence in this population that resistance to ampicillin or ampicillin/sulbactam was increasing over time.

P05.11 Antimicrobial susceptibility ofneisseria gonorrhoeaestrains from male urethritis in japan: surveillance at 2012–2013

Introduction Neisseria gonorrhoeae is one of the most important pathogens causing sexually transmitted infection. Resistant N. gonorrhoeae trains against several antimicrobials are increasing worldwide. In this study, the trends of antimicrobial susceptibilities among N. gonorrhoeae strains isolated from male patients with urethritis were investigated as the second Japanese national surveillance, which was conducted by a Japanese surveillance committee. Methods The targets were male patients older than 16 years with urethral discharge and symptoms of urethritis. Urethral discharge was collected from patients at 26 medical facilities from March 2012 to January 2013 and the antimicrobial susceptibility of strains were tested. Results From 151 patients (median age 32 years), 103 N. gonorrhoeae strains were tested for susceptibility to 20 antimicrobial agents. None was susceptible to penicillin G (MIC: ≤0.06 μg/mL). The prevalence of penicillinase producing N. gonorrhoeae or chromosomally mediated resistant N. gonorrhoeae was 1.9% or 20.8%, respectively. The susceptible rate for fluoroquinolone such as ciprofloxacin or levofloxacin was 20.3%. The susceptible rate for cefixime was 89.3%, that decreased from 98.8% at 2009. No ceftriaxone-resistant strains founded. The prevalence of less susceptible strain to ceftriaxone (MIC: 0.125 μg/mL) was 10.7%. No azithromycin high-resistant strain found and 5 strains (4.9%) had MIC ≥0.5 μg/mL. Among all strains, 83 strains (80.6%) were resistant to more than 2 kinds of antimicrobials and 42 strains (40.1%) was included to the criteria as multi-drug resistant N. gonorrhoeae . Conclusion The antimicrobial susceptibility of N. gonorrhoeae was not different between 2009 and 2012–2013, in Japan. Disclosure of interest statement Nothing to declare.

The sub-species characterization and antimicrobial resistance of Listeria monocytogenes isolated from domestic and imported food products from 2004 to 2011

Thirty-five Listeria monocytogenes strains isolated from domestic and imported food products including seafood, vegetables, and dairy foods were characterized by serotyping, molecular sub-typing, and antimicrobial susceptibility. L. monocytogenes serovars 1/2a and 1/2b strains were dominant as compared to other two serovars 4b and 1/2c strains. The dendrogram of AscI or ApaI-digested PFGE profiles of L. monocytogenes strains was classified into 23 (with 8 groups) or 3 (with 2 groups) different PFGE types, respectively. The AscI-digested groups consisted of the same serovar or food-source. Antimicrobials such as ampicillin, gentamicin, and trimethoprim-sulfamethoxazole are widely used in the treatment of listeriosis. Of the isolates used in this study, NCTR_LM14 and NCTR_LM57 were resistant to several classes of antimicrobials including aminoglycosides, penicillin, tetracycline, glycopeptide and fluoroquinolones. The multi-antimicrobial resistant isolates also showed higher efflux pump activity as compared to the antimicrobial sensitive strains NCTR_LM06 and L. monocytogenes EGD-e. This study demonstrates that L. monocytogenes isolates from various food products are genetically diverse with some isolates being resistant to more than 3 different antibiotic classes. This study also indicates that the efflux pump activity of the antibiotic resistant strains was higher than antimicrobial susceptible strains. Therefore, we propose that the antibiotic resistance observed in these strains may be conferred by the results of a highly active efflux pump system.

BmeRABC5 Is a Multidrug Efflux System That Can Confer Metronidazole Resistance inBacteroides fragilis

The RND-family efflux pump gene bmeB5 was previously shown to be overexpressed in metronidazole-resistant laboratory mutants of Bacteroides fragilis. In the present study, we characterized the bmeABC5 genes and an upstream putative TetR-family regulator gene (bmeR5). bmeR5 (645 bp) was located 51 bp upstream of bmeA5 and encoded a 24.9-kDa protein. Deletant strains lacking bmeB5 or bmeR5 were constructed from a wild-type B. fragilis strain ADB77. Strain antimicrobial susceptibility was determined and gene expression was quantified. bmeR5 was overexpressed in Escherichia coli using a 6x-His tag system; BmeR5-His6 was isolated from inclusion bodies and its binding to bmeABC5 promoter regions was determined. BmeR5-His6 bound specifically to the bmeR5-bmeC5 intergenic region (IT1). Deletion of bmeR5 (ADB77DeltabmeR5) resulted in a significant (p < 0.05) increase in expression of bmeA5, bmeB5, and bmeC5, and > two-fold increase in minimum inhibitory concentrations (MICs) of ampicillin, cefoxitin, cefoperazone, ciprofloxacin, imipenem, metronidazole, ethidium bromide, and sodium dodecyl sulfate (SDS). MICs were reduced by the efflux pump inhibitor carbonyl cyanide m-chlorophenyl hydrazone (CCCP). The MICs of ampicillin, cefoperazone, metronidazole, and SDS were reduced by approximately two-fold in ADB77DeltabmeB5. A multidrug (metronidazole)-resistant, nim-negative B. fragilis clinical isolate overexpressed bmeABC5 genes, had a G-->T point mutation in IT1, and significantly reduced binding to BmeR5-His6. These data demonstrate that BmeR5 is a local repressor of bmeABC5 expression and that mutations in IT1 can lead to a derepression and resistance to multiple antimicrobial agents, including metronidazole.

Streptococcus pneumoniae: estudo das cepas isoladas de liquor

OBJETIVO: Determinar a freqüência dos sorotipos capsulares e a susceptibilidade antimicrobiana de cepas de Streptococcus pneumoniae, assim como dar suporte à indicação de vacinas disponíveis e ao uso de antimicrobianos. MÉTODOS: Neste estudo retrospectivo, foram adotadas metodologias padronizadas para identificar, sorotipar e determinar a susceptibilidade à penicilina, cefotaxima e vancomicina. O estudo foi realizado com cepas de pneumococo isoladas de liquor em pacientes atendidos nos hospitais públicos e em três hospitais particulares do Distrito Federal no período de janeiro de 1995 a dezembro de 2004. A identificação e a determinação de susceptibilidade a antimicrobianos foi realizada no Laboratório Central de Saúde Pública no Distrito Federal. A sorotipagem foi realizada no Instituto Adolfo Lutz. RESULTADOS: Foram isoladas 232 cepas de pneumococo, compreendendo 126 cepas (54,31%) de pacientes do sexo masculino. A idade dos pacientes variou de 0 a 62 anos, sendo agrupados em faixas etárias de 0 a 5, 6 a 17, 18 a 50 e acima de 50 anos. Identificaram-se 36 sorotipos distintos. Desses destacaram-se oito: 14, 6B, 18C, 5, 19F, 23F, 9V e 6A. O teste de oxacilina caracterizou 67 cepas resistentes à penicilina; dessas, 47 foram confirmadas pelo E teste com resistência de nível intermediário. Nenhuma cepa apresentou resistência de alto nível. CONCLUSÃO: A resistência do pneumococo à penicilina apresentou um aumento gradativo nos últimos 10 anos no Distrito Federal. Os sorotipos mais isolados na faixa etária de 0 a 5 anos foram também os mais envolvidos na resistência à penicilina, e estão incluídos na vacina 7-valente.

Antimicrobial Drug Resistance Genes Do Not Convey a Secondary Fitness Advantage to Calf-Adapted Escherichia coli

Maintenance of antimicrobial drug resistance in bacteria can be influenced by factors unrelated to direct selection pressure such as close linkage to other selectively advantageous genes and secondary advantage conveyed by antimicrobial resistance genes in the absence of drug selection. Our previous trials at a dairy showed that the maintenance of the antimicrobial resistance genes is not influenced by specific antimicrobial selection and that the most prevalent antimicrobial resistance phenotype of Escherichia coli is specifically selected for in young calves. In this paper we examine the role of secondary advantages conveyed by antimicrobial resistance genes. We tested antimicrobial-susceptible null mutant strains for their ability to compete with their progenitor strains in vitro and in vivo. The null mutant strains were generated by selection for spontaneous loss of resistance genes in broth supplemented with fusaric acid or nickel chloride. On average, the null mutant strains were as competitive as the progenitor strains in vitro and in newborn calves (in vivo). Inoculation of newborn calves at the dairy with antimicrobial-susceptible strains of E. coli did not impact the prevalence of antimicrobial-resistant E. coli. Our results demonstrate that the antimicrobial resistance genes are not responsible for the greater fitness advantage of antimicrobial-resistant E. coli in calves, but the farm environment and the diet clearly exert critical selective pressures responsible for the maintenance of antimicrobial resistance genes. Our current hypothesis is that the antimicrobial resistance genes are linked to other genes responsible for differential fitness in dairy calves.

Nosocomial Outbreak of Pediatric Gastroenteritis Caused by CTX-M-14-Type Extended-Spectrum β-Lactamase-Producing Strains of Salmonella enterica Serovar London

CTX-M-14-type extended-spectrum beta-lactamase was first detected in Salmonella enterica serovar London strains which were isolated from three hospitalized pediatric patients with gastroenteritis. The isolates had pulsed-field gel electrophoresis patterns identical to those of the previously isolated antimicrobial-susceptible strains from community-acquired gastroenteritis, suggesting the susceptible clone acquired the resistance.

A1.7 Bacteriology and antimicrobial susceptibility of strains isolated from recreational swimming pools of two provinces of central Venezuela, 2003

A1.7 Bacteriology and antimicrobial susceptibility of strains isolated from recreational swimming pools of two provinces of central Venezuela, 2003

Comparative Analysis of Acid Resistance between Susceptible and Multi-Antimicrobial-Resistant Salmonella Strains Cultured under Stationary-Phase Acid Tolerance–Inducing and Noninducing Conditions

This study compared acid resistance levels among five antimicrobial-susceptible strains of Salmonella and five strains that were simultaneously resistant to a minimum of six antimicrobial agents. The induction of a stationary-phase acid tolerance response (ATR) was attempted by both transient low-pH acid shock and acid adaptation. For acid shock induction, strains were grown for 18 h in minimal E medium containing 0.4% glucose (EG medium) and exposed to sublethal acid stress (pH 4.3) for 2 h, and subsequently, both shocked and nonshocked cultures were acid challenged (pH 3.0) for 4 h. Acid adaptation was achieved by growing strains for 18 h in tryptic soy broth containing 1.0% glucose (TSB+G), while nonadapted cultures were grown for 18 h in glucose-free tryptic soy broth (TSB−G). Acid-adapted and nonadapted inocula were acid challenged (pH 2.3) for 4 h. Initial (0 h) mean populations of nonchallenged Salmonella were 8.5 to 8.7, 8.4 to 8.8, and 8.2 to 8.3 log CFU/ml for strains grown in EG medium, TSB−G, and TSB+G, respectively. After 4 h of acid challenge, mean populations were 3.0 to 4.8 and 2.5 to 3.7 log CFU/ml for previously acid-shocked susceptible and resistant strains, respectively, while corresponding counts for nonshocked strains were 4.3 to 5.5 log CFU/ml and 3.9 to 4.9 log CFU/ml. Following 4 h of acid exposure, acid-adapted cultures of susceptible and resistant strains had mean populations of 6.1 to 6.4 log CFU/ml and 6.4 to 6.6 log CFU/ml, respectively, while corresponding counts for nonadapted cultures were 1.9 to 2.1 log CFU/ml and 1.8 to 2.0 log CFU/ml, respectively. A low-pH–inducible ATR was not achieved through transient acid shock, while an ATR was evident following acid adaptation, as adapted populations were 4.2 to 4.8 log units larger than nonadapted populations following acid exposure. Although some strain-dependent variations in acid resistance were observed, results from this study suggest no association between susceptibility to antimicrobial agents and the ability of the Salmonella strains evaluated to survive low-pH stress.