Bacteremic Isolates Research Articles

Microbiological Analysis of Nontyphoidal Salmonella Strains Causing Distinct Syndromes of Bacteremia or Enteritis in HIV/AIDS Patients in San Diego, California

Recurrent invasive nontyphoidal Salmonella (NTS) infection is an AIDS-defining illness that has become less common in the developed world in the era of highly active antiretroviral therapy (HAART), while it has emerged as a major public health problem in developing countries, particularly sub-Saharan Africa. We retrospectively analyzed Salmonella (NTS) infection in HIV/AIDS patients from June 2003 until December 2009 at the University of California, San Diego (UCSD), Medical Center. Bacterial isolates from all patients were tested for selected microbiological properties, including major Salmonella (NTS) virulence loci rpoS, sodCI, spvB, and sseI. Fourteen percent of all Salmonella (NTS) cases recorded at the UCSD Medical Center during this period occurred in known HIV/AIDS patients. The clinical presentations in HIV patients fell into two distinct groups, bacteremia and enteritis. There was little clinical overlap between these two syndromes. All strains were positive for the presence of the rpoS and sodCI virulence loci, and 75% of strains were positive for the presence of the spvB and sseI loci. Antibiotic susceptibility assay showed that all strains were susceptible to trimethoprim-sulfamethoxazole and ciprofloxacin. The clinical presentation did not have a clear relationship to the CD4(+) cell count. Of the bacteremic isolates, all but one isolate, drawn from a patient with substantial enteric comorbidities, had all of the virulence genes tested, but 66% of nonbacteremic, enteritis strains also contained all the tested virulence loci. In conclusion, neither patients' CD4(+) cell count nor bacterial strain properties necessarily predicted the clinical presentation of HIV/AIDS patients with Salmonella (NTS) infection, and AIDS patients can have episodes of Salmonella enteritis without dissemination.

Comparison of antimicrobial pharmacokinetic/pharmacodynamic breakpoints with EUCAST and CLSI clinical breakpoints for Gram-positive bacteria

This study compared the susceptibility breakpoints based on pharmacokinetic/pharmacodynamic (PK/PD) models and Monte Carlo simulation with those defined by the Clinical and Laboratory Standards Institute (CLSI) and the European Committee on Antimicrobial Susceptibility Testing (EUCAST) for antibiotics used for the treatment of infections caused by Gram-positive bacteria. A secondary objective was to evaluate the probability of achieving the PK/PD target associated with the success of antimicrobial therapy. A 10000-subject Monte Carlo simulation was executed to evaluate 13 antimicrobials (47 intravenous dosing regimens). Susceptibility data were extracted from the British Society for Antimicrobial Chemotherapy database for bacteraemia isolates. The probability of target attainment and the cumulative fraction of response (CFR) were calculated. No antibiotic was predicted to be effective (CFR≥90%) against all microorganisms. The PK/PD susceptibility breakpoints were also estimated and were compared with CLSI and EUCAST breakpoints. The percentages of strains affected by breakpoint discrepancies were calculated. In the case of β-lactams, breakpoint discrepancies affected <15% of strains. However, higher differences were detected for low doses of vancomycin, daptomycin and linezolid, with PK/PD breakpoints being lower than those defined by the CLSI and EUCAST. If this occurs, an isolate will be considered susceptible based on CLSI and EUCAST breakpoints although the PK/PD analysis predicts failure, which may explain treatment failures reported in the literature. This study reinforces the idea of considering not only the antimicrobial activity but also the dosing regimen to increase the probability of clinical success of an antimicrobial treatment.

Frequent detection of plasmid-mediated quinolone resistance (qnr) genes in multidrug-resistant Enterobacteriaceae blood isolates, Hong Kong

Plasmid-mediated quinolone resistance (qnr) genes confer low-level resistance but provide background for selection of highly-resistant strains. We investigated their prevalence and significance in clinical Enterobacteriaceae bacteremic isolates in Hong Kong. A prospective, hospital-based study was conducted (January 2008 to March 2009). Consecutive, non-duplicate blood isolates of extended-spectrum-β-lactamase (ESBL) and/or plasmid-mediated AmpC (PMAmpC) β-lactamase-producing Enterobacteriaceae were collected and subjected to qnr genes detection using multiplex PCR. Direct sequencing was performed to characterize the qnr and the co-existing bla genes. Clinical and microbiological variables, including antimicrobial resistance profiles, were compared between infections by 'qnr-positive' and 'qnr-negative' Enterobacteriaceae. Altogether 199 ESBL/PMAmpC-producing Enterobacteriaceae isolates were studied. qnr genes were detected in 20 % (qnrB, n = 24; qnrS, n = 16; qnrA, n = 0), of which 85% were Klebsiella spp. There was a strong association with PMAmpC genes (qnrB and DHA-1; p < 0.001). 'qnr-positive' isolates were more commonly hospital-acquired (60.0% vs 35.8%; adjusted OR 2.68, 95%CI 1.32-5.46) and multidrug-resistant (e.g. amoxicillin-clavulanate 90-100%, piperacillin-tazobactam 40-57%, ceftazidime 53-78%; sulfamethoxazole/trimethoprim 60-70%; ciprofloxacin 53-65%, levofloxacin 35-48%). Patients with 'qnr-positive' Enterobacteriaceae bacteremia had a higher 30-day mortality (45% vs 22%, p = 0.003). High Pitt bacteremia score, development of pneumonia, and failure to receive susceptible fluoroquinolone (adjusted HR 4.27; 95%CI 1.45-12.61) or carbapenem (adjusted HR 3.04; 95%CI 1.49-6.20) treatment were independent factors associated with death. A high proportion of ESBL/PMAmpC-producing Enterobacteriaceae (typically Klebsiella) bacteremic isolates carried qnr. These strains were multidrug-resistant, which was associated with inappropriate treatment and high fatality. Further dissemination of qnr and selection of fluoroquinolone/β-lactam-resistant strains should be closely monitored and controlled.

Antimicrobial resistance to benzylpenicillin in invasive pneumococcal disease in Belgium, 2003–2010: the effect of altering clinical breakpoints

The Belgian data (2003-2010) for the European Antimicrobial Resistance Surveillance Network (EARS-Net) showed a significant decreasing trend in the proportion of penicillin non-susceptible Streptococcus pneumoniae (9·4% to <1%) from blood and CSF isolates. We found that 75% of this decrease was explained by a change in Clinical and Laboratory Standards Institute (CLSI) breakpoints as the trend disappeared if only the new breakpoints were applied. Applying only European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints also resulted in a relatively stable proportion of penicillin non-susceptibility (average 5%), but this proportion was 7-13 times higher than with the new CLSI breakpoints. When the new CLSI breakpoints alone are used, fewer than 1% of bacteraemia isolates were penicillin non-susceptible during the entire period, but the proportion of non-susceptible meningitis isolates rose from 6·3% in 2003 to 15·9% between 2003 and 2010. Changing breakpoints should lead to retrospective analysis of historical data to minimize wrongly interpreting resistance trends.

Changing trends in antimicrobial susceptibility of Streptococcus pneumoniae isolates in Taiwan, 2006–2007

Multiple antibiotic-resistant clones of Streptococcus pneumoniae have spread throughout the world and continue to evolve under the selective pressure of antibiotics and vaccines. The aim of this study is to assess the susceptibility of S. pneumoniae isolates and to analyze the resistance trends in Taiwan. Antimicrobial susceptibility tests were performed on 152 nonmeningeal isolates of S. pneumoniae that were collected from 13 different hospitals around Taiwan from 2006-2007. Tests were performed using the broth microdilution method according to recommendations of the Clinical and Laboratory Standards Institute. The minimal inhibitory concentrations (MIC(50)/MIC(90)) of penicillin, cefotaxime, vancomycin, and moxifloxacin were 0.5/1.0, 0.25/1.0, 0.25/0.5, and 0.06/0.12 μg/mL, respectively. The susceptibility rates of penicillin, cefotaxime, vancomycin, and moxifloxacin were 99.3%, 99.3%, 100%, and 98.7%, respectively. However, if the meningitis breakpoints were applied to these nonmeningeal isolates, the susceptibility rates of penicillin and cefotaxime were reduced to 18.4% and 76.3%, respectively. Compared with the findings from previous studies in Taiwan, our results show that the percentage of S. pneumoniae isolates with a penicillin MIC of 0.12-1.0 μg/mL increased from 43.3% in 1996-1997 to 73.7% in 2006-2007 (p < 0.001). The percentage of S. pneumoniae isolates with a cefotaxime MIC of 1.0 μg/mL increased from 11.3% in 1996-1997 to 23.0% in 2006-2007 (p < 0.001). Regarding the serial MIC intervals of the four antimicrobial agents, there was no significant difference between bacteremic and nonbacteremic isolates. Although nonmeningeal S. pneumoniae isolates remained susceptible to penicillin, the proportion of isolates with a penicillin MIC of 0.12-1.0 μg/mL or cefotaxime MIC of 1.0 μg/mL increased during the past decade in Taiwan. The ever-increasing resistance of S. pneumoniae has a great impact on the treatment of meningitis.

Laboratory identification, risk factors, and clinical outcomes of patients with bacteremia due to Escherichia coli and Klebsiella pneumoniae Producing Extended-Spectrum and AmpC type β-Lactamases

Extended-spectrum β-lactamase (ESBL)-producing bacteria coexpressing AmpC type β-lactamase (ACBL) are associated with the laboratory issue of false susceptibility to third-generation cephalosporins. This study was to evaluate laboratory tests and clinical significance of bacteremic isolates of Escherichia coli and Klebsiella pneumoniae with both ESBL and ACBL [dual-type lactamases (DTL)]. From 2006 to 2009, 78 E coli and 12 pneumoniae bacteremic isolates with reduced susceptibility to cefotaxime (CTX) or ceftazidime (CAZ) were identified and relevant patients' data were collected for analysis. Phenotypic and genotypic characterizations of these selected isolates were determined by inhibitor-based assays and polymerase chain reaction-based genetic analyses, respectively. Among the 90 isolates, 47 had DTL production. There was an increasing annual prevalence from 29% in 2006 to 56% in 2009 (p=0.02). Phenotypic assays had a sensitivity and specificity of 57% (43/76) and 93% (13/14) for ESBL detection and 95% (58/61) and 34% (10/29) for ACBL, respectively. Among the DTL-producing isolates, phenotypic assays yielded a higher false negative rate of ESBL detection than that of ACBL detection (70% versus 6%), while all false negative ESBL results were associated with ESBL genes other than bla(CTx-M). The majority of the DTL-producing isolates were in the category of resistance to CTX (47/47, 100%) and CAZ (44/47, 94%) by the Clinical and Laboratory Standards Institute (CLSI) 2010 interpretive criteria, of which many were considered intermediate or fully susceptible to CTX (25/47, 53%) and CAZ (15/47, 32%) by the previous ones (CLSI-2009). The DTL-producing isolates exhibited a lower susceptibility rate to fluoroquinolones, aztreonam, and β-lactam/lactamase inhibitors than those with either ESBL or ACBL alone. The use of indwelling catheters or nasogastric tubes was associated with bacteremia due to the DTL isolates, but the mortality rates were not different among those due to isolates with ESBL, ACBL, or both. By multivariate analysis, Pittsburg bacteremia score and Charlson comorbidity index were the significant predictors for all-cause mortalities. Bacteremic episodes due to DTL-producing E coli and K pneumoniae became increasingly prevalent and were often associated with coresistance to antibiotics other than β-lactams, but they were not associated with a worse prognosis than those due to ESBL- or ACBL-producing bacteria.

Clinical outcomes of type III Pseudomonas aeruginosa bacteremia*

Pseudomonas aeruginosa bacteremia is a serious and life-threatening infection associated with high mortality. Among the multitude of virulence determinants possessed by P. aeruginosa, the type 3 secretion system has been implicated with more acute and invasive infection in respiratory diseases. However, the relationship between the type 3 secretion system and clinical outcomes in P. aeruginosa bacteremia has not been investigated. To determine the association between the type 3 secretion system virulence factor in P. aeruginosa bloodstream infection and 30-day mortality. Retrospective analysis of 85 cases of P. aeruginosa bacteremia. Tertiary care hospital. Bacterial isolates were assayed in vitro for secretion of type 3 exotoxins (ExoU, ExoT, and ExoS). Strain relatedness was analyzed using randomly amplified polymorphic DNA polymerase chain reaction genotyping. Antimicrobial susceptibilities were determined by means of the Kirby-Bauer disk-diffusion test. At least one of the type 3 secretion system proteins was detected in 37 out of the 85 isolates (44%). Septic shock was identified in 43% of bacteremic patients with type 3 secretion system+ isolates compared to 23% of patients with type 3 secretion system- isolates (p = .12). A high frequency of resistance in the type 3 secretion system+ isolates was observed to ciprofloxacin (59%), cefepime (35%), and gentamicin (38%). There was a significant difference in the 30-day cumulative probability of death after bacteremia between secretors and nonsecretors (p = .02). None of the type 3 secretion system+ patients who survived the first 30 days had a P. aeruginosa isolate which exhibited ExoU phenotype. The expression of type 3 secretion system exotoxins in bacteremic isolates of P. aeruginosa confers poor clinical outcomes independent of antibiotic susceptibility profile.

Carbapenem Therapy for Bacteremia Due to Extended-Spectrum-β-Lactamase-Producing Escherichia coli or Klebsiella pneumoniae: Implications of Ertapenem Susceptibility

A retrospective study was conducted at two medical centers in Taiwan to evaluate the clinical characteristics, outcomes, and risk factors for mortality among patients treated with a carbapenem for bacteremia caused by extended-spectrum-beta-lactamase (ESBL)-producing organisms. A total of 251 patients with bacteremia caused by ESBL-producing Escherichia coli and Klebsiella pneumoniae isolates treated by a carbapenem were identified. Among these ESBL-producing isolates, rates of susceptibility to ertapenem (MICs ≤ 0.25 μg/ml) were 83.8% and 76.4%, respectively; those to meropenem were 100% and 99.3%, respectively; and those to imipenem were 100% and 97.9%, respectively. There were no significant differences in the critical illness rate (P = 0.1) or sepsis-related mortality rate (P = 0.2) for patients with bacteremia caused by ESBL-producing K. pneumoniae (140 isolates, 55.8%) and E. coli (111 isolates, 44.2%). Multivariate analysis of variables related to sepsis-related mortality revealed that the presence of severe sepsis (odds ratio [OR], 15.9; 95% confidence interval [CI], 5.84 to 43.34; P < 0.001), hospital-onset bacteremia (OR, 4.65; 95% CI, 1.42 to 15.24; P = 0.01), and ertapenem-nonsusceptible isolates (OR, 5.12; 95% CI, 2.04 to 12.88; P = 0.001) were independent risk factors. The patients receiving inappropriate therapy had a higher sepsis-related mortality than those with appropriate therapy (P = 0.002), irrespective of ertapenem, imipenem, or meropenem therapy. Infections due to the ertapenem-susceptible isolates (MICs ≤ 0.25 μg/ml) were associated with a more favorable outcome than those due to ertapenem-nonsusceptible isolates (MICs > 0.25 μg/ml), if treated by a carbapenem. However, the mortality for patients with bacteremic episodes due to isolates with MICs of ≤ 0.5 μg/ml was similar to the mortality for those whose isolates had MICs of >0.5 μg/ml (P = 0.8). Such a finding supports the rationale of the current CLSI 2011 criteria for carbapenems for Enterobacteriaceae.

Rhodococcus Bacteremia in Cancer Patients Is Mostly Catheter Related and Associated with Biofilm Formation

Rhodococcus is an emerging cause of opportunistic infection in immunocompromised patients, most commonly causing cavitary pneumonia. It has rarely been reported as a cause of isolated bacteremia. However, the relationship between bacteremia and central venous catheter is unknown. Between 2002 and 2010, the characteristics and outcomes of seventeen cancer patients with Rhodococcus bacteremia and indwelling central venous catheters were evaluated. Rhodococcus bacteremias were for the most part (94%) central line-associated bloodstream infection (CLABSI). Most of the bacteremia isolates were Rhodococcus equi (82%). Rhodococcus isolates formed heavy microbial biofilm on the surface of polyurethane catheters, which was reduced completely or partially by antimicrobial lock solution. All CLABSI patients had successful response to catheter removal and antimicrobial therapy. Rhodococcus species should be added to the list of biofilm forming organisms in immunocompromised hosts and most of the Rhodococcus bacteremias in cancer patients are central line associated.

Distribution and phenotypic and genotypic detection of a metallo-β-lactamase, CphA, among bacteraemic Aeromonas isolates

The objectives of the study were to investigate the distribution of cphA-related genes (cphA) encoding a CphA metallo-β-lactamase (MBL) among 51 consecutive Aeromonas blood isolates and to compare different phenotypic methods for detecting CphA. The presence of cphA was detected by PCR. Four phenotypic methods, the imipenem-EDTA combined disc test, imipenem-EDTA MBL Etest, agar dilution test and modified Hodge test (MHT), were used to detect imipenem susceptibility and MBL production. The results showed that 35 (69%) blood isolates had cphA. All (100%) of 16 Aeromonas aquariorum isolates and 12 Aeromonas veronii isolates, and 4 (80%) of 5 Aeromonas hydrophila isolates, carried cphA, but none of 15 Aeromonas caviae isolates did. With the standard inocula, irrespective of the presence or absence of cphA, all but one (50, 98%) isolates were susceptible to imipenem tested by disc diffusion, Etest and agar dilution (10(4) c.f.u. spot inocula), and did not exhibit MBL production by the imipenem-EDTA combined disc test and MBL Etest. By the agar dilution test using large inocula (10(7) c.f.u.), 34 (97%) of 35 cphA(+) isolates had imipenem MICs of ≥16 µg ml(-1), higher than the susceptible breakpoint (4 µg ml(-1)), and demonstrated positive results for the MHT, while one cphA(+) and all 17 cphA(-) isolates had imipenem MICs of ≤4 µg ml(-1). In conclusion, the distribution of cphA among aeromonads is species-specific, found in A. aquariorum, A. veronii and A. hydrophila, and the MHT may be a phenotypic screening test for CphA production.

Analysis of positive bacteriology cultures at a regional microbiology in view of understanding local epidemiology and improving the quality of services

Aim Analysis of positive bacteriology specimens performed over one year to determine local epidemiology data and to improve methods and reporting procedure. Methods The study was performed at a regional microbiology laboratory servicing a large number of rural health facilities. All positive bacteriology cultures for 7467 organisms were extracted from the laboratory information system and analysed using Microsoft Excel. This included 354 positive blood cultures, 1696 wound swabs, 2293 urine cultures and 512 sputum samples. Susceptibility data were analysed for Staphylococcus aureus, Enterococci, ESCPPM and non-ESCPPM groups of Enterobacter-iaceae and Pseudmonas aeruginosa. Observations were made regarding current methodology and opportunities for improvements with ongoing support of supervising laboratory were identified. Results Direct susceptibility data for urine specimens for ampi-cillin, amoxycillin-clavulanate, cephalothin, gentamicin and tri-methoprim for non-ESCPPM organisms were 43%, 76%, 45%, 98% and 80%, respectively; the ESCPPM group of organisms showed susceptibilities of 93% for gentamicin and 78% for trimethoprim and 88% for norfloxacin. The single anti-Pseudomonal drug tested, gentamicin, showed 99% susceptibility. Eighty percent of Enterococci remained susceptible to ampicillin. Forty percent of urinary S. aureus were methicillin-resistant Staphylococcus aureus (MRSA) with the majority community (CMRSA). Susceptibilities for bacteraemic S. aureus isolates included 88% of methicillin-sensitive Staphylococcus aureus (MSSA), 10% of CMRSA and 2% of nosocomial MRSA. Non-ESCPPM organisms showed susceptibilities of 48%, 67%, 92%, 92% 98% and 100% for ampicillin, amoxycillin-clavulanate, gentamicin, cefotaxime, ciprofloxacin and meropenem, respectively. Susceptibilities of bacteraemic ESCAPPM isolates for gentamicin, ciprofloxacin and meropenem were 100%, 88% and 100%. Sixty-two percent of Enterococci remained susceptible to ampicillin. Conclusions A number of analytical and post-analytical factors were identified with potential improvements to be done in view of upgrading the quality of services. Analysis of positive bacteriology specimens performed over one year to determine local epidemiology data and to improve methods and reporting procedure. The study was performed at a regional microbiology laboratory servicing a large number of rural health facilities. All positive bacteriology cultures for 7467 organisms were extracted from the laboratory information system and analysed using Microsoft Excel. This included 354 positive blood cultures, 1696 wound swabs, 2293 urine cultures and 512 sputum samples. Susceptibility data were analysed for Staphylococcus aureus, Enterococci, ESCPPM and non-ESCPPM groups of Enterobacter-iaceae and Pseudmonas aeruginosa. Observations were made regarding current methodology and opportunities for improvements with ongoing support of supervising laboratory were identified. Direct susceptibility data for urine specimens for ampi-cillin, amoxycillin-clavulanate, cephalothin, gentamicin and tri-methoprim for non-ESCPPM organisms were 43%, 76%, 45%, 98% and 80%, respectively; the ESCPPM group of organisms showed susceptibilities of 93% for gentamicin and 78% for trimethoprim and 88% for norfloxacin. The single anti-Pseudomonal drug tested, gentamicin, showed 99% susceptibility. Eighty percent of Enterococci remained susceptible to ampicillin. Forty percent of urinary S. aureus were methicillin-resistant Staphylococcus aureus (MRSA) with the majority community (CMRSA). Susceptibilities for bacteraemic S. aureus isolates included 88% of methicillin-sensitive Staphylococcus aureus (MSSA), 10% of CMRSA and 2% of nosocomial MRSA. Non-ESCPPM organisms showed susceptibilities of 48%, 67%, 92%, 92% 98% and 100% for ampicillin, amoxycillin-clavulanate, gentamicin, cefotaxime, ciprofloxacin and meropenem, respectively. Susceptibilities of bacteraemic ESCAPPM isolates for gentamicin, ciprofloxacin and meropenem were 100%, 88% and 100%. Sixty-two percent of Enterococci remained susceptible to ampicillin. A number of analytical and post-analytical factors were identified with potential improvements to be done in view of upgrading the quality of services.

Erratum

Click to increase image sizeClick to decrease image sizeThis article refers to:Antimicrobial Susceptibility Patterns of Selected Bacteraemic Isolates from South African Public Sector Hospitals, 2010

Impact of inappropriate empirical antibiotic therapy on outcome of bacteremic adults visiting the ED

ObjectivesTo investigate the clinical impact of inappropriate empirical antibiotics on patient outcome and determine the risk factors for mortality in bacteremic adults who visited the emergency department (ED). MethodsBacteremic adults visiting the ED from January 2007 to June 2008 were identified retrospectively. Demographic characteristics, clinical conditions, bacteremic pathogens, antimicrobial agents, and outcomes were determined from chart records. ResultsThe total of 454 eligible bacteremic adults were included in the analysis; excluded from the study were another 261 patients with contaminated blood cultures and 64 patients with ED stays of less than 24 hours. Among the included individuals, the mean age was 64.6 years, with a small predominance of males (230 patients, 50.7%). Of a total 494 bacteremic isolates, Escherichia coli (206, 41.7%) and Klebsiella species (81, 16.4%) were the most frequently encountered microorganisms. A lower 28-day mortality rate was demonstrated in bacteremic patients treated with appropriate antibiotics than that in those with inappropriate antibiotics or that in those with no antibiotic therapy, as judged by Kaplan-Meier survival curves (P = .01). Moreover, the differences among these three groups achieved higher significance (P = .002) in critically ill patients (Pittsburgh bacteremia scores of ≥4 points). In multivariate analyses, inappropriate antibiotic therapy in the ED was associated independently with mortality at 28 days (odds ratio, 2.26; 95% confidence interval, 1.01-5.13; P = .04). ConclusionsFor bacteremic adults visiting the ED, their outcomes were favorable following appropriate antibiotics, compared to treatment with inappropriate antibiotics or no antibiotics.

Amino acid substitutions of quinolone resistance determining regions in GyrA and ParC associated with quinolone resistance in Acinetobacter baumannii and Acinetobacter genomic species 13TU

Amino acid substitutions in GyrA and ParC are associated with resistance to quinolones in Acinetobacter baumannii (A baumannii), but this association is rarely elucidated in Acinetobacter genomic species (AGS) 13TU. This study aims to compare the association of amino acid substitutions in GyrA and ParC with quinolone resistance in A baumannii and AGS 13TU in Taiwan. Eleven representative strains of A baumannii and 13 strains of AGS 13TU were selected from 402 bacteremic isolates. The sequences of quinolone resistance determining regions of gyrA and parC were determined. Minimal inhibitory concentrations (MICs) of nalidixic acid, ciprofloxacin, levofloxacin and moxifloxacin were determined by agar dilution method. Ser83Leu substitution in GyrA in A baumannii (one strain) was associated with resistance to all tested quinolones. This substitution plus a Ser80Leu or Ser80Tyr in ParC in A baumannii (four strains) and AGS 13TU (two strains) were associated with higher MICs of all quinolones. All but one quinolone MICs of A baumannii (one strain) and AGS 13TU (two strains) carrying a single substitution Ser56Asn in ParC remained in the susceptibility breakpoint. The Ser83Leu substitution in GyrA, even with additional Ser56Asn substitution in ParC, was associated with resistance to only nalidixic acid, but not other newer quinolones in AGS 13TU (two strains). A baumannii and AGS 13TU possessed similar quinolone resistance associated with amino acid substitutions in GyrA and ParC. Further study with more strains is needed to determine whether a single Ser83Leu substitution in GyrA was associated with a high level of quinolone MIC only in A baumannii, but not in AGS 13TU.

Streptococcus pyogenes bacteraemia, emm types and superantigen profiles

The aim of this study was to investigate the emm types and superantigen profiles of bacteraemic group A streptococcal (GAS; Streptococcus pyogenes) isolates and to detect possible associations between the molecular characteristics of isolates and the clinical presentations of disease. In this population-based study, 87 bacteraemic GAS isolates from adult patients in Pirkanmaa Health District (HD), Finland, during the period 1995-2004 were emm typed and genotyped for superantigen (SAg) profiles. The epidemiological and clinical data of the patients were analysed with the microbiological characterisation data. Among the 87 isolates, 18 different emm types were found. emm1, emm28 and emm81 were the three most common types, covering 52% of isolates. The prevalence of specific emm types showed high variability during the 10-year study period. We could not find any association between the emm type and clinical features of bacteraemic infection, such as underlying diseases, disease manifestations or case fatality. Of nine superantigen genes examined, speA and speC were identified in 20 and 30% of the strains, respectively. No association was found between disease manifestation and the presence of single superantigen genes. The 26-valent GAS vaccine would have covered only 62% of isolates causing invasive disease in Pirkanmaa HD during the study period.

Risk factors and outcome of Pseudomonas aeruginosa bacteremia among adults visiting the ED

ObjectivesThe aim of this study was to determine the clinical characteristics of, antibiotic therapy for, and clinical outcome of Pseudomonas aeruginosa infection among bacteremic adults who visit the emergency department (ED). MethodsBacteremic adults who visited the ED were identified retrospectively from January 2007 to December 2007. Demographic characteristics, underlying illnesses, severity, bacteremic pathogens, antimicrobial agents, and outcome were determined from chart records. ResultsThe records of 340 eligible bacteremic adults were analyzed; their mean age was 66.2 years, and major comorbidities included hypertension (175 patients, or 51.5%), diabetes mellitus (124, or 36.5%), and malignancy (87, or 25.6%). Among the 379 bacteremic isolates, Escherichia coli (139 isolates, or 6.6%) and Klebsiella pneumoniae (63, or 16.6%) were the major pathogens, whereas P aeruginosa (15, or 4.0%) was the third-leading gram-negative isolate. Of note, both 30-day mortality (33.3% vs 8.9%, P = .01) and the proportion of empirically inappropriate antibiotics (86.7% vs 31.4%, P < .001) were higher in bacteremia caused by P aeruginosa than in bacteremia not caused by P aeruginosa in univariate analysis. Moreover, multivariate analysis identified 3 independent factors related to P aeruginosa bacteremia: surgery during the 4 weeks before ED arrival (adjusted odds ratio [AOR], 12.7; 95% confidence interval [CI], 1.68-95.7; P = .01), malignancy (AOR, 4.57; 95% CI, 1.27-16.3; P = .02), and community onset (AOR, 0.14; 95% CI, 0.04-0.47; P = .002). ConclusionsFor bacteremic adults who visited the ED, P aeruginosa was associated with a high mortality rate and a high proportion of empirically inappropriate antibiotic therapy. Identification of clinical predictors of P aeruginosa bacteremia would improve the quality of care and the use of appropriate antibiotics in the ED.

Molecular analysis of community-acquired methicillin-susceptible and resistant Staphylococcus aureus isolates recovered from bacteraemic and osteomyelitis infections in children from Tunisia

Thirty-six children (27 boys, nine girls) that fulfilled CDC criteria for community-acquired infections were diagnosed with bacteraemia and/or osteomyelitis caused by Staphylococcus aureus during an 18-month period (2006–2008). Antibiotic susceptibility was determined by an agar dilution method. SCCmec type, carriage of pvl genes, agr type and spa-typing were determined using specific PCR protocols. Clonal relatedness was examined by pulsed field gel electrophoresis-SmaI and mutilocus sequence typing techniques. From the 36 isolates, eight (22%) corresponded to methicillin-resistant Staphylococcus aureus (MRSA) -t044/042-CC80/CC5-IVc-pvl+-agrIII/II. The highest genetic diversity was observed among the 28 community-acquired methicillin-susceptible S. aureus (CA-MSSA) isolates: 22 spa-variants that also grouped by multilocus sequence typing in CC1, CC5, CC6, CC8, CC30, CC80, CC97 and the singletons ST464, ST1467, ST1468 and ST1469. The pvl genes were detected in all eight CA-MRSA isolates and in eight CA-MSSA isolates (28%), being significantly more frequent among isolates causing osteoarticular infection (11 of 12, 92%) than in the bacteraemic isolates (six of 24, 25%). Based on patients’ age, three groups were considered: newborns, infants and children. Bacteraemia was diagnosed in all newborns and infants, whereas in 42% of the children group osteomyelitis was the unique presentation. In most cases, the portal of entry was either the skin or unknown. In general, favourable outcome was observed, except in four cases—three of whom had severe complications and one died. In summary, we analysed the epidemiological and genetic background of community-acquired staphylococcal strains causing bacteraemic and/or osteomyelitis infections in children from Tunisia, describing three new sequence types and one novel spa type.

Antimicrobial susceptibility of bacteremic isolates from cancer patients with or without neutropenia at a medical center in southern Taiwan

Few studies focus on comparison of antimicrobial susceptibility for bacteremic isolates in neutropenic and nonneutropenic cancer patients. The purpose of this study was to elucidate the antimicrobial susceptibility of bacteremic isolates from cancer patients. We collected bacterial isolates causing bloodstream infections in cancer patients at a tertiary care hospital from 2003 to 2005 and performed in vitro antimicrobial susceptibility of these pathogens by the disc diffusion method. A total of 588 bacterial isolates were identified from 476 episodes of bloodstream infections in cancer patients. Major pathogens were Escherichia coli (22.4%), Klebsiella pneumoniae (17.6%), and Pseudomonas aeruginosa (14.1%) in neutropenic patients and E coli (13.3%), K pneumoniae (10.1%), and Staphylococcus aureus (9.7%) in nonneutropenic patients. Of S aureus, 55.8% were resistant to methicillin, and of coagulase-negative Staphylococcus 87.0%. Cefepime, cefpirome, piperacillin/tazobactam, meropenem, or imipenem in combination with or without an aminoglycoside, were active against more than 85% of gram-negative bacilli (GNB). Ceftazidime, piperacillin, or ciprofloxacin plus an aminoglycoside were also active against more than 85% of GNB. The susceptibility rate of GNB or gram-positive cocci to any agent was not different between the isolates from neutropenic and nonneutropenic patients, but more GNB isolates from the former were susceptible to imipenem or meropenem plus an aminoglycoside. GNB remained dominant among bacteremic isolates in cancer patients. Antimicrobial agents, especially aminoglycoside-containing combination regimens, as recommended by Infectious Diseases Society of Taiwan for febrile neutropenia, were active against more than 85% of GNB isolates.

Antimicrobial Susceptibility Patterns of Selected Bacteraemic Isolates from South African Public Sector Hospitals, 2010

We report on antimicrobial susceptibility surveillance data for six key bloodstream pathogens (Escherichia coli, Klebsiella pneumoniae, Enterobacter spp., Pseudomonas aeruginosa, Acinetobacter baumannii and Staphylococcus aureus) identified in public sector hospitals in South Africa during 2010. Major findings include the accelerated emergence of carbapenem resistance among K. pneumoniae and Enterobacter species, with overall susceptibility rates of 98% and 96% for ertapenem, and above 99% for meropenem and imipenem. Levels of resistance among P. aeruginosa and A. baumannii remain high in all centres, with few changes since 2009. Large decreases in piperacillin-tazobactam susceptibility rates were noted at three institutions, probably related to methodological issues. S. aureus remains a major pathogen countrywide, with between 30-60% of isolates resistant to cloxacillin [methicillin-resistant S. aureus (MRSA)]. Ongoing surveillance for antimicrobial resistance is vital, and the use of a centralised data ...

Differences between methicillin-resistant Staphylococcus aureus bacteremic isolates harboring type IV and type V staphylococcal cassette chromosome mec genes based on prior patient healthcare exposure

This observational study enrolled adult patients with bacteremia due to methicillin-resistant Staphylococcus aureus (MRSA) who were treated at the emergency department of a teaching hospital from 2001 to 2007. MRSA isolates with type IV and type V staphylococcal cassette chromosome mec (SCCmec) genes (SCC IV/V-MRSA) were included in the final analysis. Healthcare-associated SCC IV/V-MRSA (HA-SCC IV/V-MRSA) and community-acquired SCC IV/V-MRSA (CA-SCC IV/V-MRSA) were defined as the identification of an SCC IV/V-MRSA isolate from a patient with and without healthcare-associated risk factors, respectively. Thirty-four cases of CA-SCC IV/V-MRSA (20 SCCmec type IV, 14 SCCmec type V) and 81 cases of HA-SCC IV/V-MRSA (59 SCCmec type IV, 22 SCCmec type V) bacteremia were identified. Vascular device-associated infections were a significant infection source in HA-SCC IV/V-MRSA bacteremia cases. SCCmec type IV HA-SCC IV/V-MRSA isolates (3.4%) were significantly less likely to carry the Panton-Valentine leukocidin (PVL) gene than SCCmec type IV CA-SCC IV/V-MRSA isolates (35.0%, p = 0.001). The 90-day cumulative probability of survival was 76% for patients with CA-SCC IV/V-MRSA bacteremia and 66% for patients with HA-SCC IV/V-MRSA bacteremia (p = 0.247, by the Wilcoxon rank-sum test). Significant differences in antimicrobial susceptibility were observed between bacterial isolates from patients with CA-SCC IV/V-MRSA bacteremia and HA-SCC IV/V-MRSA bacteremia.