In vitro activity of cefiderocol and other newly approved antimicrobials against multi-drug resistant Gram-negative pathogens recovered in intensive care units in Spain and Portugal

OBJECTIVE

The antimicrobial resistance is a significant public health threat, particularly for healthcare-associated infections caused by carbapenem-resistant Gram-negative pathogens which are increasingly reported worldwide. The aim of this study was to provide data on the in vitro antimicrobial activity of cefiderocol and that of commercially available comparator antibiotics against a defined collection of recent clinical multi-drug resistant (MDR) microorganisms, including carbapenem resistant Gram-negative bacteria collected from different regions in Spain and Portugal.

METHODS

A total of 477 clinical isolates of Enterobacterales, Pseudomonas aeruginosa, Acinetobacter baumannii and Stenotrophomonas maltophilia were prospectively (n=265) and retrospectively (n=212) included (2016-2019). Susceptibility testing was performed using standard broad microdilution and results were interpreted using CLSI-2021 and EUCAST-2021 criteria.

RESULTS

Overall, cefiderocol showed a good activity against Enterobacterales isolates, being 99.5% susceptible by CLSI and 94.5% by EUCAST criteria. It also demonstrated excellent activity against P. aeruginosa and S. maltophilia isolates, all being susceptible to this compound considering CLSI breakpoints. Regarding A. baumannii (n=64), only one isolate was resistant to cefiderocol.

CONCLUSIONS

Our results are in agreement with other studies performed outside Spain and Portugal highlighting its excellent activity against MDR gram-negative bacteria. Cefiderocol is a therapeutic alternative to those available for the treatment of infections caused by these MDR bacteria.

Diagnostic tool for surveillance, detection and monitoring of the high-risk clone K. pneumoniae ST15

BACKGROUND

The global spread of Klebsiella pneumoniae ST15, causing multi-continental outbreaks, contributes to the movement of resistance genes between clones increasing the antimicrobial resistance crisis. The genomic traits providing it with the ability to outcompete other bacteria and cause epidemics remain unclear.

AIM

To identify the specific genomic traits of K. pneumoniae ST15 to develop a diagnostic test.

METHODS

An outbreak caused by K. pneumoniae occurred in Hospital A Coruña, Spain. Antimicrobial susceptibility analysis and molecular typing (PGFE and MLST) were performed. One isolate of each sequence type was selected for whole-genome sequencing analysis. Comparative analysis of genomes was performed using RAST. BLASTn was used to evaluate the presence of the fhaC and kpiD genes. Two hundred and ninety-four K. pneumoniae from a Spanish nationwide collection were analysed by PCR.

FINDINGS

Genotyping showed that 87.5% of the isolates tested belonged to a clone with a unique PFGE pattern which corresponded to ST15. Comparative genomic analysis of the different STs enabled us to determine the specific genomic traits of K. pneumoniae ST15. Two adherence-related systems (Kpi and KpFhaB/FhaC) were specific markers of this clone. Multiplex-PCR analysis with kpiD and fhaC oligonucleotides revealed that K. pneumoniae ST15 is specifically detected with a sensitivity of 100% and a specificity of 97.76%. The PCR results showed 100% concordance with the MLST and whole-genome sequencing data.

CONCLUSION

K. pneumoniae ST15 possesses specific genomic traits that could favour its dissemination. They could be used as targets to detect K. pneumoniae ST15 with high sensitivity and specificity.

Clinical management of cUTI, cIAI, and HABP/VABP attributable to carbapenem-resistant Gram-negative infections in Spain

Introduction. Carbapenem-resistant Gram-negative (CRGN) infections are a major public health problem in Spain, often implicated in complicated, healthcare-associated infections that require the use of potentially toxic antibacterial agents of last resort. The objective of this study was to assess the clinical management of complicated infections caused by CRGN bacteria in Spanish hospitals. Methods. The study included: 1) a survey assessing the GN infection and antibacterial susceptibility profile in five participating Spanish hospitals and 2) a non-interventional, retrospective single cohort chart review of 100 patients with complicated urinary tract infection (cUTI), complicated intra-abdominal infection (cIAI), or hospital-acquired bacterial pneumonia/ventilator-associated bacterial pneumonia (HABP/VABP) attributable to CRGN pathogens. Results. In the participating hospitals CRGN prevalence was 9.3% amongst complicated infections. In the retrospective cohort, 92% of infections were healthcare-associated, and Klebsiella pneumoniae and Pseudomonas aeruginosa were the most common pathogens. OXA was the most frequently detected carbapenemase type (71.4%). We found that carbapenems were frequently used to treat cUTI, cIAI, HABP/VABP caused by CRGN pathogens. Carbapenem use, particularly in combination with other agents, persisted after confirmation of carbapenem resistance. Clinical cure was 66.0%, mortality during hospitalization 35.0%, mortality at the time of chart review 62.0%, and 6-months-post-discharge readmission 47.7%. Conclusion. Our results reflect the high burden and unmet needs associated with the management of complicated infections attributable to CRGN pathogens in Spain and highlight the urgent need for enhanced clinical management of these difficult-to-treat infections.

Bioinformatics approaches to the study of antimicrobial resistance

Detection and monitoring of antimicrobial resistance are two pillars on which clinical microbiology will be based in the coming decades. The implementation of certain technologies such as whole genome sequencing (WGS) or mass spectrometry and the creation of national and international databases that include and gather data on antimicrobial resistance from around the world has allowed the application of bioinformatics in the study of antimicrobial resistance in microorganisms involved in human pathology.

Predictors of outcome in patients with severe sepsis or septic shock due to extended-spectrum β-lactamase-producing Enterobacteriaceae

PURPOSE

There are few data in the literature regarding sepsis or septic shock due to extended-spectrum β-lactamases (ESBL)-producing Enterobacteriaceae (E). The aim of this study was to assess predictors of outcome in septic patients with bloodstream infection (BSI) caused by ESBL-E.

METHODS

Patients with severe sepsis or septic shock and BSI due to ESBL-E were selected from the INCREMENT database. The primary endpoint of the study was the evaluation of predictors of outcome after 30 days from development of severe sepsis or septic shock due to ESBL-E infection. Three cohorts were created for analysis: global, empirical-therapy and targeted-therapy cohorts.

RESULTS

367 septic patients were analysed. Overall mortality was 43.9% at 30 days. Escherichia coli (62.4%) and Klebsiella pneumoniae (27.2%) were the most frequent isolates. β-lactam/β-lactamase inhibitor (BLBLI) combinations were the most empirically used drug (43.6%), followed by carbapenems (29.4%). Empirical therapy was active in vitro in 249 (67.8%) patients, and escalation of antibiotic therapy was reported in 287 (78.2%) patients. Cox regression analysis showed that age, Charlson Comorbidity Index, McCabe classification, Pitt bacteremia score, abdominal source of infection and escalation of antibiotic therapy were independently associated with 30-day mortality. No differences in survival were reported in patients treated with BLBLI combinations or carbapenems in empirical or definitive therapy.

CONCLUSIONS

BSI due to ESBL-E in patients who developed severe sepsis or septic shock was associated with high 30-day mortality. Comorbidities, severity scores, source of infection and antibiotic therapy escalation were important determinants of unfavorable outcome.

How to: identify non-tuberculous Mycobacterium species using MALDI-TOF mass spectrometry

BACKGROUND

The implementation of MALDI-TOF MS for microorganism identification has changed the routine of the microbiology laboratories as we knew it. Most microorganisms can now be reliably identified within minutes using this inexpensive, user-friendly methodology. However, its application in the identification of mycobacteria isolates has been hampered by the structure of their cell wall. Improvements in the sample processing method and in the available database have proved key factors for the rapid and reliable identification of non-tuberculous mycobacteria isolates using MALDI-TOF MS.

AIMS

The main objective is to provide information about the proceedings for the identification of non-tuberculous isolates using MALDI-TOF MS and to review different sample processing methods, available databases, and the interpretation of the results.

SOURCES

Results from relevant studies on the use of the available MALDI-TOF MS instruments, the implementation of innovative sample processing methods, or the implementation of improved databases are discussed.

CONTENT

Insight about the methodology required for reliable identification of non-tuberculous mycobacteria and its implementation in the microbiology laboratory routine is provided.

IMPLICATIONS

Microbiology laboratories where MALDI-TOF MS is available can benefit from its capacity to identify most clinically interesting non-tuberculous mycobacteria in a rapid, reliable, and inexpensive manner.

Direct identification of clinical pathogens from liquid culture media by MALDI-TOF MS analysis

OBJECTIVES

We propose using MALDI-TOF MS as a tool for identifying microorganisms directly from liquid cultures after enrichment of the clinical sample in the media, to obtain a rapid microbiological diagnosis and an adequate administration of the antibiotic therapy in a clinical setting.

METHODS

To evaluate this approach, a series of quality control isolates were grown in thioglycollate (TG) broth and brain heart infusion (BHI) broth and extracted under four different protocols before finally being identified by MALDI-TOF MS. After establishing the best extraction protocol, we validated the method in a total of 300 liquid cultures (150 in TG broth and 150 in BHI broth) of different types of clinical samples obtained from two tertiary Spanish hospitals.

RESULTS

The initial evaluation showed that the extraction protocol including a 5 minute sonication step yielded 100% valid identifications, with an average score value of 2.305. In the clinical validation of the procedure, 98% of the microorganisms identified from the TG broth were correctly identified relative to 97% of those identified from the BHI broth. In 24% of the samples analysed, growth by direct sowing was only successful in the liquid medium, and no growth was observed in the direct solid agar cultures.

CONCLUSIONS

Use of MALDI-TOF MS plus the sonication-based extraction method enabled direct and accurate identification of microorganisms in liquid culture media in 15 minutes, in contrast to the 24 hours of subculture required for conventional identification, allowing the administration of a targeted antimicrobial therapy.

The FhaB/FhaC two-partner secretion system is involved in adhesion of Acinetobacter baumannii AbH12O-A2 strain

Acinetobacter baumannii is a hospital-acquired pathogen that shows an extraordinary capacity to stay in the hospital environment. Adherence of the bacteria to eukaryotic cells or to abiotic surfaces is the first step for establishing an infection. The A. baumannii strain AbH12O-A2 showed an exceptional ability to adhere to A549 epithelial cells. The AbFhaB/FhaC 2-partner secretion (TPS) system involved in adhesion was discovered after the screening of the recently determined A. baumannii AbH12O-A2 strain genome (CP009534.1). The AbFhaB is a large exoprotein which transport to the bacterial surface is mediated by the AbFhaC protein. In the present study, the role of this TPS system in the AbH12O-A2 adherence phenotype was investigated. The functional inactivation of this 2-partner secretion system was addressed by analyzing the outer membrane vesicles (OMV) proteomic profile from the wild-type strain and its derivative mutant AbH12O-A2ΔfhaC demonstrating that AbFhaB is no longer detected in the absence of AbFhaC. Scanning electron microscopy (SEM) and adhesion experiments demonstrated that inactivation of the AbFhaB/FhaC system significantly decreases bacterial attachment to A549 alveolar epithelial cells. Moreover, it has been demonstrated that this 2-partner secretion system is involved in fibronectin-mediated adherence of the A. baumannii AbH12O-A2 isolate. Finally, we report that the AbFhaB/FhaC system is involved in virulence when tested using invertebrate and vertebrate hosts. These data suggest the potential role that this AbFhaB/FhaC secretion system could play in the pathobiology of A. baumannii.

Assessment of antivirulence activity of several d-amino acids against Acinetobacter baumannii and Pseudomonas aeruginosa

OBJECTIVES

Biofilm formation and bacterial adherence are important requirements for persistence, multidrug resistance and infection. The d-amino acids play a role as modulators of bacterial growth and persistence, though their ability to inhibit biofilms is much debated. In this study, we analysed the effects of 18 different d-amino acids on the pathogens Acinetobacter baumannii and Pseudomonas aeruginosa.

METHODS

In vitro assays were carried out to analyse the effect of d-amino acids on bacterial growth, biofilm formation/disassembly, capacity to attach to eukaryotic cells and cellular death. In addition, in vivo assays were performed in mice, using experimental models of sepsis and pneumonia.

RESULTS

Biofilm formation was inhibited in A. baumannii by d-His, d-Cys and d-Trp (35%-86%) at 2 mM and in P. aeruginosa by d-Cys, d-Trp and d-Tyr (10%-30%) at 4 mM. Attachment to the A549 human alveolar cells was reduced in A. baumannii by d-Cys, d-His, d-Met, d-Val and d-Ser, and in P. aeruginosa by d-Arg and d-Trp. Growth was inhibited in A. baumannii by d-Cys and d-Trp, and in P. aeruginosa by d-Trp. In virulence assays, incubation of alveolar cells infected with P. aeruginosa with d-Cys, d-Trp and d-Arg reduced cell death (56%-45%). However, no significant effect of d-amino acids was observed in vivo.

CONCLUSIONS

Some d-amino acids can inhibit bacterial growth, biofilm formation and adherence to eukaryotic cells in A. baumannii and P. aeruginosa, and showed a protective effect against infection of alveolar cells with P. aeruginosa. Despite the fact that some considerable protection was observed in mice, survival differences between treated and control groups were not statistically significant.

Optimisation of the Caenorhabditis elegans model for studying the pathogenesis of opportunistic Acinetobacter baumannii

This study aimed to increase the sensitivity of Caenorhabditis elegans as an infection model for detection of minor differences in virulence or fitness between different Acinetobacter baumannii strains with known resistance and virulence mechanisms. Selected A. baumannii strains and mutants, comprising wild-type strains (ATCC 17978 and 19606), colistin-resistant strains (ATCC 19606 ΔlpxA and ATCC 19606 ΔlpxC), a clinical encapsulated isolate (AB307-0294), an imipenem-resistant strain (ATCC 17978 Δomp33-36) and an sRNA knock-out strain (ATCC 17978 Δ13573), were employed in developing killing and fertility assays in a C. elegans infection model. Because virulence levels of the strains were known, they could be used to assess assays in the nematode model for their ability to discriminate between degrees of virulence. The model was validated by microscopic analysis and in a murine sepsis infection model. The fertility assay, specifically utilising nematode growth medium, was able to detect virulence differences between the wild-type strains, ATCC 19606 ΔlpxA and isolate AB307-0294. Moreover, modification of an alternative culture medium by incremental changes in osmolarity facilitated detection of subtle virulence differences between isogenic mutants (ATCC 17978 Δomp33-36 and 17978 Δ13573). The success of the proposed fertility model depends on establishing a balance between optimal C. elegans reproduction and environmental stress leading to maximum pathogen-induced damage. This invertebrate model may reduce the need for mammalian in vivo studies of A. baumannii resistance and pathogenicity and may additionally be validated for the study of other low-virulence bacterial pathogens.

Evaluation of MALDI-TOF mass spectrometry for identification of anaerobic bacteria

In this study MALDI-TOF MS was evaluated in the identification of anaerobic bacteria comparing it with Rapid ID 32A system. Discrepancies were solved by 16S r-RNA gene sequencing. At the species level MALDI-TOF MS identified 94.82% and Rapid ID 32A 86.67%, showing the superiority of MALDI-TOF MS to conventional methods.

Monotherapy versus combination therapy for sepsis due to multidrug-resistant Acinetobacter baumannii: analysis of a multicentre prospective cohort

BACKGROUND

Treatment of multidrug-resistant Acinetobacter baumannii (MDRAB) infection presents a challenge because of the scarcity of available options. Even though combination therapy (CT) is frequently used in clinical practice, data are needed to support its use instead of monotherapy (MT).

METHODS

A prospective observational study was conducted in 28 Spanish hospitals. Patients with sepsis caused by MDRAB, defined according to strict criteria, and who received active antibiotic treatment (according to in vitro susceptibility testing) for at least 48 h, were included. The main outcome variable was all-cause 30 day mortality after initiation of targeted therapy. Multivariate analysis, including a propensity score (for receiving CT), was performed by Cox regression.

RESULTS

One hundred and one patients were included in the analysis; 68 (67.3%) received MT and 33 (32.7%) received CT. Pneumonia was the most common infection (50.5%), 68.6% of cases being associated with mechanical ventilation. Colistin (67.6%) and carbapenems (14.7%) were the most common drugs used in MT; colistin plus tigecycline (27.3%) and carbapenem plus tigecycline (12.1%) were the most frequent combinations. Crude 30 day mortality was 23.5% and 24.2% for the MT and CT groups, respectively (RR = 1.03; 95% CI 0.49-2.16; P = 0.94). Multivariate analysis of 30 day survival showed no trend towards reduced 30 day mortality with CT (HR = 1.35; 95% CI 0.53-3.44; P = 0.53). Subgroup analysis showed similar results.

CONCLUSIONS

Our data do not support an association of CT with reduced mortality in MDRAB infections. More data for specific types of infection and combinations are needed.

Prevention strategies for cytomegalovirus disease and long-term outcomes in the high-risk transplant patient (D+/R-): experience from the RESITRA-REIPI cohort

BACKGROUND

Cytomegalovirus (CMV)-negative recipients of a graft from a CMV-positive donor (D+/R-) are at high risk of CMV disease. Current preventive strategies include universal prophylaxis (UP) and preemptive therapy (PT). However, the best strategy to prevent CMV disease and achieve better long-term outcomes remains a matter of debate.

METHODS

We analyzed the incidence of CMV disease and long-term outcomes including graft dysfunction and patient mortality at 5 years after transplantation with both preventive strategies. High-risk (D+/R-) kidney and liver transplant recipients from the RESITRA cohort were included.

RESULTS

Of 2410 kidney or liver transplant patients, 195 (8.3%) were D+/R-. The final cohort included 58 liver and 102 kidney recipients. UP was given in 92 patients and 68 received PT; 10.9% and 36.8% developed CMV disease, respectively (P < 0.01). The independent risk factors for CMV disease were PT strategy (hazard ratio [HR], 3.30; 95% confidence interval [CI], 1.6-6.9), kidney transplantation (HR, 3.8; 95% CI, 1.4-9.9), and cyclosporine immunosuppression (HR, 2.4; 95% CI, 1.2-4.7). PT strategy was also a risk factor for CMV disease in both liver transplantation (HR, 11.0; 95% CI, 1.2-98.7) and kidney transplantation (HR, 2.7; 95% CI, 1.3-6.0), independently. The development of CMV replication during the first 2 years after transplantation was a risk factor for graft dysfunction at 5 years after transplantation (odds ratio, 3.4; 95% CI, 1.3-9.0). Nevertheless, no significant differences were seen in either graft dysfunction or mortality between the 2 strategies.

CONCLUSIONS

The study supports the benefit of the UP strategy to prevent CMV disease in D+/R- liver or kidney transplant patients. The development of CMV replication during the first 2 years after transplantation was associated with graft dysfunction at 5 years after transplantation.

Prevalence and molecular epidemiology of acquired AmpC β-lactamases and carbapenemases in Enterobacteriaceae isolates from 35 hospitals in Spain

The purpose of this investigation was to determine the prevalence of plasmid-mediated AmpC (pAmpC) and carbapenemases in Enterobacteriaceae collected from 35 hospitals in Spain and to establish their epidemiological relationships. We conducted a prospective multi-centre study on pAmpC- or carbapenemase-producing Enterobacteriaceae isolates from clinical samples collected from February to July 2009. The strains suspected to carry pAmpC were resistant or showed intermediate susceptibility to co-amoxiclav and second- or third-generation cephalosporins. Strains suspected to carry a carbapenemase were selected because they showed a minimum inhibitory concentration (MIC) to imipenem >1 mg/L. Polymerase chain reaction (PCR) and a sequencing strategy were used to characterise the enzymes. The clonal relationships between isolates was analysed by pulsed field gel electrophoresis (PFGE). Among 100,132 Enterobacteriaceae isolates collected, 1,654 were compatible with the production of pAmpC or carbapenemases. We found a prevalence of 0.64 % of pAmpC (n = 635) and 0.04 % of carbapenemases (n = 43). The most prevalent pAmpC enzymes were CMY-type (78.3 %), DHA-type (19.5 %), ACC-type (1.6 %) and FOX-type (0.6 %). The CMY-type was the most frequent in Escherichia coli and Proteus mirabilis species, whereas the DHA-type was mainly found in Klebsiella spp. The enzymes involved in carbapenem resistance were VIM-1, IMP-22 and the new IMP-28. Nine new bla genes were described: bla (CMY-54), bla (CMY-55), bla (CMY-56), bla (CMY-57), bla (CMY-96), bla (DHA-6), bla (DHA-7), bla (FOX-8) and bla (IMP-28). The prevalence of pAmpC or carbapenemases found is not negligible. The CMY-types were the predominant pAmpC, whereas the VIM or IMP enzymes were the predominant carbapenemases. Furthermore, we observed a great genetic diversity among pAmpC-producing strains and a close clonal relationship between carbapenemase-producing strains.

Bacterial urinary tract infection after solid organ transplantation in the RESITRA cohort

BACKGROUND

Urinary tract infection (UTI) is the most common infection in renal transplant patients, but it is necessary to determine the risk factors for bacterial UTI in recipients of other solid organ transplants (SOTs), as well as changes in etiology, clinical presentation, and prognosis.

METHODS

In total, 4388 SOT recipients were monitored in 16 transplant centers belonging to the Spanish Network for Research on Infection in Transplantation (RESITRA). The frequency and characteristics of bacterial UTI in transplant patients were obtained prospectively from the cohort (September 2003 to February 2005).

RESULTS

A total of 192 patients (4.4%) presented 249 episodes of bacterial UTI (0.23 episodes per 1000 transplantation days); 156 patients were kidney or kidney-pancreas transplant recipients, and 36 patients were liver, heart, and lung transplant recipients. The highest frequency was observed in renal transplants (7.3%). High frequency of cystitis versus pyelonephritis without related mortality was observed in both groups. The most frequent etiology was Escherichia coli (57.8%), with 25.7% producing extended-spectrum β-lactamase (ESBL). In all transplants but renal, most cases occurred in the first month after transplantation. Cases were uniformly distributed during the first 6 months after transplantation in renal recipients. Age (odds ratio [OR] per decade 1.1, 95% confidence interval [CI] 1.02-1.17), female gender (OR 1.74, 95% CI 1.42-2.13), and the need for immediate post-transplant dialysis (OR 1.63, 95% CI 1.29-2.05) were independent variables associated with bacterial UTI in renal and kidney-pancreas recipients. The independent risk factors identified in non-renal transplants were age (OR per decade 1.79, 95% CI 1.09-3.48), female gender (OR 1.7, 95% CI 1.43-2.49), and diabetes (OR 1.02, 95% CI 1.001-1.040).

CONCLUSIONS

UTI was frequent in renal transplants, but also not unusual in non-renal transplants. Because E. coli continues to be the most frequent etiology, the emergence of ESBL-producing strains has been identified as a new problem. In both populations, most cases were cystitis without related mortality. Although the first month after transplantation was a risk period in all transplants, cases were uniformly distributed during the first 6 months in renal transplants. Age and female gender were identified as risk factors for UTI in both populations. Other particular risk factors were the need for immediate post-transplant dialysis in renal transplants and diabetes in non-renal transplants.

Donor infection and transmission to the recipient of a solid allograft

Transmission of infection from donor to recipient is a potential complication of transplantation. More data on this issue are needed to expand the insufficient donor pool. This study evaluates the incidence of donor nonviral infection, transmission from infected donors and the effect of donor infection on 30-day recipient survival. Data from 211 infected donors contributing to 292 (8.8%) of 3322 consecutive transplant procedures within RESITRA (Spanish Research Network for the Study of Infection in Transplantation) were prospectively compiled and analyzed. Lung was the most likely transplanted organ carried out with an infected donor and Staphylococcus aureus was the most commonly isolated microorganism. In more than a half of donors, the lung was the site of infection. Donor-to-host transmission was documented in 5 patients out of 292 (1.71%), 2 of whom died of the acquired infection (40%). Nonetheless, there was no difference in 30-day patient survival when comparing transplant procedures performed with organs from infected or uninfected donors. In conclusion, donor infection is not an infrequent event, but transmission to the recipient is quite low. Hence, with careful microbiological surveillance and treatment, the number of organs available for transplantation may be increased.

False extended-spectrum beta-lactamase detection in Acinetobacter spp. due to intrinsic susceptibility to clavulanic acid

BACKGROUND

There are some reports showing the susceptibility of some strains of Acinetobacter baumannii to the beta-lactamase inhibitor clavulanic acid. To address this issue, we determined the MIC of clavulanic acid for a broad collection of Acinetobacter spp. isolates collected in a multicentre study. In addition, we showed the consequences of this susceptibility to yield false extended-spectrum beta-lactamase (ESBL) detection in this genus.

METHODS

The strains used were 244 isolates of Acinetobacter (226 A. baumannii, 15 Acinetobacter genomic species 3 and 3 unidentified Acinetobacter spp.) and several A. baumannii as positive controls. The isolates were subjected to molecular typing. One isolate of each genotype was subjected to clavulanic acid MIC analysis. As no breakpoints for clavulanic acid are available, we arbitrarily established three categories of susceptibility: < or = 16, 32-128 and > or = 256 mg/L. The presence of ESBL in Acinetobacter spp. was analysed by using microdilution, double disc diffusion, combined discs, Etest and isoelectric focusing.

RESULTS

A total of 100 different genotypes were detected. Among them, 44, 26 and 30 genotypes were inhibited by < or = 16, 32-128 and > or = 256 mg/L clavulanic acid, respectively. Representative isolates of each group were tested for ESBL production. Only those with the lower clavulanic acid MICs yielded a false-positive ESBL test with all methods tested with the exception of the double disc diffusion assay.

CONCLUSIONS

Forty-four per cent of the genotypes tested were inhibited by < or = 16 mg/L clavulanic acid and these Acinetobacter isolates yielded a false ESBL-positive test. These results may have implications for susceptibility testing in routine microbiology laboratories.

Pneumonia after lung transplantation in the RESITRA Cohort: a multicenter prospective study

The aim of the present study is to evaluate the epidemiology, etiology and prognosis of pneumonia in lung transplant (LT) recipients. This is a prospective, multicenter study of a consecutive cohort of LT recipients in Spain. From September 2003 to November 2005, 85 episodes of pneumonia in 236 LT recipients were included (incidence 72 episodes per 100 LT/year). Bacterial pneumonia (82.7%) was more frequent than fungal (14%) and viral pneumonia (10.4%). The most frequent microorganisms in each etiological group were Pseudomonas aeruginosa (n = 14, 24.6%), CMV (n = 6, 10.4%) and Aspergillus spp. (n = 5, 8.8%). Incidence of Aspergillus spp. and CMV pneumonia is lower than previously reported, probably due to the spread of universal prophylaxis. Pneumonia caused by viruses appeared significantly later than pneumonia due to gram-negative bacilli, fungi and those without known etiology (p < 0.01, p = 0.03 and p = 0.02, respectively). The routine use of ganciclovir has changed the natural history of CMV infection, so that pneumonia appears later, once prophylaxis is suspended. The probability of survival during the first year of follow-up was significantly higher in the multivariate analysis in LT recipients who did not have a pneumonia episode compared with those that had at least one episode (p < 0.01).

Characterisation of the first CTX-M-10-producing isolate of Salmonella enterica serotype Virchow

Microbiological analysis of a urine sample from an outpatient with symptoms of urinary infection detected >10(5) CFU/mL urine of Salmonella enterica serotype Virchow with resistance to cefotaxime. Molecular analysis demonstrated the presence of the gene encoding CTX-M-10 beta-lactamase in this clinical isolate. This is the first report of this enzyme in Salmonella spp.

Risk-factors for the acquisition of imipenem-resistant Acinetobacter baumannii in Spain: a nationwide study

Potential risk-factors for the acquisition of imipenem-resistant Acinetobacter baumannii were investigated in a cohort study in 25 Spanish hospitals. The clonal relationship among isolates was determined by pulsed-field gel electrophoresis (PFGE). In total, A. baumannii was isolated from 203 patients, with imipenem-resistant (MIC(90) 128 mg/L) isolates being obtained from 88 patients (43%), and imipenem-susceptible isolates from 115 patients (57%). A wide clonal distribution was observed among the imipenem-resistant isolates, but spread of the same clone among centres was not demonstrated. The results indicated that imipenem-resistant A. baumannii is a widely distributed nosocomial pathogen in Spain and reaches an alarming frequency in some centres. Independent risk-factors for the acquisition of imipenem-resistant A. baumannii were a hospital size of >500 beds (multivariate OR, 6.5; 95% CI, 1.8--23), previous antimicrobial treatment (multivariate OR, 4.3; 95% CI, 1.6--11), a urinary catheter (multivariate OR, 2.7; 95% CI, 1.1--6.7) and surgery (multivariate OR, 2; 95% CI, 1.07--3.8).

Evaluation of Group B Streptococcus Differential Agar for detection and isolation of Streptococcus agalactiae

In total, 320 vaginal or rectal swabs were cultured on Granada medium (GM) or Group B Streptococcus Differential Agar (GBSDA), and were also inoculated into LIM broth (Todd-Hewitt broth supplemented with selective antibiotics), for detection of group B Streptococcus (GBS). Overall, GBS isolates were detected on 53 of the 320 swabs; 47 of these isolates grew on both GM and GBSDA, five only on GBSDA, and one only following subculture from LIM broth. GBSDA appears to be a valid alternative to GM for the growth of GBS isolates from pregnant women.

Hospital outbreak caused by a carbapenem-resistant strain of Acinetobacter baumannii: patient prognosis and risk-factors for colonisation and infection

Between October 2001 and August 2002, 30 hospital patients became infected or colonised by a multiresistant (including to carbapenems) epidemic strain of Acinetobacter baumannii (AbMR) in a hospital outbreak. This study analysed the risk-factors associated with acquisition of this epidemic strain and investigated the prognosis of patients infected by AbMR, with the aim of elucidating factors which lead to mortality. A case-control study of the acquisition of AbMR in patients infected or colonised in the hospital outbreak was performed. Independent risk-factors leading to death were studied by logistic regression analysis. Multivariate analysis of the risk-factors for colonisation/infection with AbMR revealed an independent association with the presence of an arterial catheter (OR, 1.13; 95% CI, 1.03-1.25) and administration of imipenem as monotherapy (OR, 11.12; 95% CI, 2.33-53.09). Multivariate analysis of the prognostic features leading to mortality revealed a significant association with hypotension or shock (OR, 24.63; 95% CI, 1.56-387.56) at the time of bacterial isolation.

Prevalence of genotypic resistance in untreated HIV-infected patients

The aims of this retrospective study are to assess the prevalence of primary resistances to antiretroviral drugs, both reverse transcriptase and protease inhibitors in untreated patients from Spain, and to determine their possible association with several epidemiological variables. A total of 148 samples belonging to 145 patients were processed using the genotypic technique VERSANT HIV 1 (LiPA) in order to study the presence of mutations at codons 41, 69, 70, 74, 75, 103, 106, 151, 181, 184 and 215 of the reverse transcriptase gene (VERSANT HIV 1 RT) and at codons 30, 46, 48, 50, 54, 82, 84 and 90 of the protease gene (VERSANT HIV 1 Protease). The patients' epidemiological variables which could be relevant to HIV infection were also analyzed. The successful amplification rate was 77.70% for LiPA RT and 91.21% for LiPA P. In the case of LiPA RT, statistical significance (p < 0.05) was observed when successful amplification was related to viral load level (p < 0.001). Global prevalence of resistance was 20.27%. Mutations in the reverse transcriptase gene were found in eight samples (5.40%). Using LiPA P, mutations were detected in 16.21% of cases, with V82A being the most frequently detected mutation (15/24, 62.50%) in nine samples. The V82A mutation was found alone (66.6%) and it was found together with the I84V mutation in five samples (20.83%). I84V was the second most frequently detected mutation (13/24, 54.16%). No statistical significance was found for any of the epidemiological variables. Due to the problems encountered in a high percentage of samples, the authors concluded that the amplification technique should be improved. The prevalence of resistance detected was around the mean of that found by other authors.

Antimicrobial susceptibility and mechanisms of resistance to quinolones and beta-lactams in Acinetobacter genospecies 3

Antimicrobial susceptibility was determined in 15 epidemiologically unrelated clinical isolates of Acinetobacter genospecies 3. Moreover, the mechanisms of resistance to some beta-lactam antibiotics may be associated with the presence of a chromosomal cephalosporinase, AmpC, and the resistance to quinolones related to mutations in the gyrA and parC genes.

Factors associated with the evolution of the viral load in individuals with HIV infection

The temporal evolution of the viral load (VL) in a group of patients under clinical care and the identification of individual variables that determined this evolution was studied using a retrospective descriptive study of the VL determinations on 1336 patients between September 1996 and June 2000. During follow-up, patients' VLs increasingly fell below the detection threshold. Those patients who had received antiretroviral treatment prior to the monitoring of the viraemia presented lower VLs at the start of their follow-up. Those patients who had been cared for on the same unit throughout their follow-up maintained lower VLs. Female patients uniformly presented lower VL results than the males. The immunological status at the beginning of follow-up and the basal VL determined the initial evolution of the patients' VL, although it did not do so in the final stages of follow-up. The immunological and virological state at the onset of the follow-up determines the evolution of the patients' VL.

Diagnostic value of polymerase chain reaction in blood and aqueous humor in immunocompetent patients with ocular toxoplasmosis

PURPOSE

To evaluate the diagnostic value of polymerase chain reaction (PCR) in blood and aqueous humor samples from immunocompetent patients with reactivated ocular toxoplasmosis.

METHODS

Group 1 was composed of seven patients with a clinical diagnosis of reactivated ocular toxoplasmosis. Group 2 consisted of 33 controls. In each subject, blood and aqueous humor samples were obtained for detection of Toxoplasma gondii DNA by means of simple PCR, seminested PCR, and Southern blot hybridization.

RESULTS

Group 1: Simple PCR was positive in 3 of 7 blood samples (42%) and in 2 of 7 (28%) aqueous humor samples. Seminested PCR was positive in 4 of 7 (57%) blood samples and in 3 of 7 (42%) aqueous humor samples. Group 2: Simple and seminested PCR were positive in both samples in 2 of 33 (6%) and 4 of 33 (12%), respectively. Sensitivity 57% (18.41-90.10), specificity 87% (71.80-96.60); positive and negative likelihood ratio 4.38 and 0.49, respectively.

CONCLUSIONS

Polymerase chain reaction can be useful for confirming the diagnosis of ocular toxoplasmosis, especially in those eyes where fundus examination does not yield conclusive results. The detection of T. gondii DNA in blood suggests that reactivation of ocular toxoplasmosis cannot be considered a local event.

Chemokine-receptor activation by env determines the mechanism of death in HIV-infected and uninfected T lymphocytes

There is considerable confusion concerning the mechanism of lymphocyte death during HIV infection. During the course of HIV infection, M-tropic viruses (R5) that use CCR5 chemokine coreceptors frequently evolve to T-tropic viruses (X4) that use CXCR4 receptors. In this study we show that activation of the CD4 or CCR5 receptor by R5 HIVenv causes a caspase 8-dependent death of both uninfected and infected CD4 T cells. In contrast, CXCR4 activation by X4 HIVenv induces a caspase-independent death of both uninfected CD4 and CD8 T cells and infected CD4 cells. These results suggest that activation of the chemokine receptor by HIVenv determines the mechanism of death for both infected and uninfected T lymphocytes.

PCR-based DNA fingerprinting (REP-PCR, AP-PCR) and pulsed-field gel electrophoresis characterization of a nosocomial outbreak caused by imipenem- and meropenem-resistant Acinetobacter baumannii

OBJECTIVE

To demonstrate the usefulness of REP-PCR and AP-PCR on molecular typing of A. baumannii isolates.

METHOD

From February to November 1997, 29 inpatients at Ramón y Cajal Hospital, Madrid-23 in five intensive care units (ICUs) and six at two different medical departments-were either colonized or infected with imipenem- and meropenem-resistant Acinetobacter baumannii (IMRAB) strains (MICs of 64-256 mg/L). A wide antibiotic multiresistance profile was observed with IMRAB strains, and only tobramycin, sulbactam and colistin displayed valuable activity. For typing IMRAB isolates, repetitive extragenic palindromic sequence-based polymerase chain reaction (REP-PCR) and arbitrary primer sequence-based polymerase chain reaction (AP-PCR) methods were used and compared with pulsed-field gel electrophoresis (PFGE) as reference technique. For comparative purposes, 30 imipenem- and meropenem-susceptible A. baumannii (IMSAB) strains isolated before, during and after the outbreak were included in this study.

RESULTS

The molecular typing results showed that the outbreak was caused by a single IMRAB strain (genotype 1). On the other hand, seven different genotypes were observed in the pre-, at- and post-outbreak strains tested by REP-PCR. Regarding AP-PCR, three of four at-outbreak IMSAB strains were indistinguishable from the IMRAB profile. Thus, with AP-PCR, only six genotypes were obtained, apart from the IMRAB genotype.

CONCLUSION

Under our experimental conditions, REP-PCR had a higher discriminatory power than AP-PCR, with PFGE as reference technique. The REP-PCR technique is a useful and expeditious method for the epidemiologic characterization of A. baumannii nosocomial outbreaks, the results being comparable to those obtained with the PFGE technique.

Characterization of a nosocomial outbreak caused by a multiresistant Acinetobacter baumannii strain with a carbapenem-hydrolyzing enzyme: high-level carbapenem resistance in A. baumannii is not due solely to the presence of beta-lactamases

From February to November 1997, 29 inpatients at Ramón y Cajal Hospital, Madrid, Spain, were determined to be either colonized or infected with imipenem- and meropenem-resistant Acinetobacter baumannii (IMRAB) strains (MICs, 128 to 256 microg/ml). A wide antibiotic multiresistance profile was observed with IMRAB strains. For typing IMRAB isolates, pulsed-field gel electrophoresis was used. For comparative purposes, 30 imipenem- and meropenem-susceptible A. baumannii (IMSAB) strains isolated before, during, and after the outbreak were included in this study. The molecular-typing results showed that the outbreak was caused by a single IMRAB strain (genotype A). By cloning experiments we identified a class D beta-lactamase (OXA-24) encoded in the chromosomal DNA of this IMRAB strain which showed carbapenem hydrolysis. Moreover, the outer membrane profile of the IMRAB strain showed a reduction in the expression of two porins at 22 and 33 kDa when compared with genetically related IMSAB isolates. In addition no efflux mechanisms were identified in the IMRAB strains. In summary, we report here the molecular characterization of a nosocomial outbreak caused by one multiresistant A. baumannii epidemic strain that harbors a carbapenem-hydrolyzing enzyme. Although alterations in the penicillin-binding proteins cannot be ruled out, the reduction in the expression of two porins and the presence of this OXA-derived beta-lactamase are involved in the carbapenem resistance of the epidemic nosocomial IMRAB strain.

Molecular characterization of FOX-4, a new AmpC-type plasmid-mediated beta-lactamase from an Escherichia coli strain isolated in Spain

A clinical strain of Escherichia coli (Ec GCE) displayed resistance to cefoxitin, cefotetan, cefotaxime, and ceftazidime. Susceptibility was not restored by the addition of clavulanic acid. Two beta-lactamases with apparent pIs of 5.4 and 6.4 were identified; the beta-lactamase with a pI of 6.4 was transferred by conjugation and associated with a 40-kb plasmid. Analysis of the nucleotide sequence showed a new ampC beta-lactamase gene that is closely related to those encoding the FOX-3, FOX-2, and FOX-1 beta-lactamases but whose product has four novel amino acid mutations, at positions 11 (M-->T), 43 (A-->E), 233 (V-->A), and 280 (Y-->H). This first cephamycinase from Spain was named FOX-4.

OXA-24, a novel class D beta-lactamase with carbapenemase activity in an Acinetobacter baumannii clinical strain

Acinetobacter baumannii RYC 52763/97, a clinical isolate involved in a prolonged nosocomial outbreak at our hospital, was resistant to all beta-lactams tested, including imipenem and meropenem, which had MICs of 128 and 256 microg/ml, respectively. This strain synthesized three beta-lactamases: a plasmid-mediated TEM-1 beta-lactamase (pI 5.4), an AmpC-type chromosomal cephalosporinase (pI 9.4), and a novel, presumptively chromosomally mediated OXA-related enzyme (pI 9.0) named OXA-24. After cloning and sequencing, the deduced amino acid sequence of the OXA-24 beta-lactamase showed 40% homology with the OXA-10 (PSE-2) and OXA-7 beta-lactamases, 39% homology with the OXA-11 and OXA-5 enzymes, and 33% homology with the LCR-1 beta-lactamase. The amino acid sequence of the OXA-24 beta-lactamase contained the STFK motif found in serine beta-lactamases, but the typical class D triad KTG was replaced by KSG and the motif YGN was replaced by FGN. The OXA-24 beta-lactamase hydrolyzed benzylpenicillin and cephaloridine but lacked activity against oxacillin, cloxacillin, and methicillin. The enzymatic activity was inhibited by chloride ions and by tazobactam (50% inhibitory concentration [IC(50)], 0.5 microM), sulbactam (IC(50), 40 microM), and clavulanic acid (IC(50), 50 microM). Carbapenem MICs for an Escherichia coli transformant (pBMB-1) expressing the cloned OXA-24 enzyme had a fourfold increase. Relative V(max)/K(m) values of 13 and 6 were obtained with imipenem and meropenem, respectively, and a positive microbiological assay result with imipenem was obtained with a purified enzymatic extract of this transformant strain. Therefore, we consider this new beta-lactamase to be involved in the carbapenem resistance of A. baumannii RYC 52763/97.

Ribosomal stalk protein phosphorylating activities in Saccharomyces cerevisiae

With ribosomal P protein as a substrate, five peaks of protein kinase activity are eluted after chromatography of a Saccharomyces cerevisiae cellular extract on DEAE-cellulose. Two of them correspond to CK-II and the other three have been called RAP-1, RAP-II, and RAP-III. RAP-I was previously characterized. RAP-III is present in a very small amount, which hindered its purification. RAP-II was further purified on phosphocellulose, heparin-Sepharose, and P protein-Sepharose, studied in detail, and compared with other acidic protein kinases, including RAP-I, CK-II, and PK60. RAP-II is shown by SDS-PAGE and centrifugation on glycerol linear density gradients to have a molecular mass of around 62 kDa and it is immunologically different from RAP-I and PK60. RAP-II phosphorylates the P proteins in the last serine residue at the highly conserved carboxyl terminal domain as other P-protein kinases. The ribosome-bound stalk P proteins are not equally phosphorylated by the different kinases. Thus, RAP-II and PK60 mainly phosphorylate P1beta and P2alpha whereas RAP-I and CK-II modify all of them. A comparative study of the K(m) and V(max) of the phosphorylation reaction by the different kinases using individual purified acidic proteins suggests changes in the substrate susceptibility upon binding to the ribosome. All the data available reveal clear differences in the characteristics of the various P protein kinases and suggest that the cell may use them to differentially modify the stalk depending, perhaps, on metabolic requirements.

Cloning, nucleotide sequencing, and analysis of the gene encoding an AmpC beta-lactamase in Acinetobacter baumannii

A clinical strain of Acinetobacter baumannii (strain Ab RYC 52763/97) that was isolated during an outbreak in our hospital and that was resistant to all beta-lactam antibiotics tested produced three beta-lactamases: a TEM-1-type (pI, 5.4) plasmid-mediated beta-lactamase, a chromosomally mediated OXA-derived (pI, 9.0) beta-lactamase, and a presumptive chromosomal cephalosporinase (pI, 9.4). The nucleotide sequence of the chromosomal cephalosporinase gene shows for the first time the gene encoding an AmpC beta-lactamase in A. baumannii. In addition, we report here the biochemical properties of this A. baumannii AmpC beta-lactamase.

Structure and function of the stalk, a putative regulatory element of the yeast ribosome. Role of stalk protein phosphorylation

The ribosomal stalk is involved directly in the interaction of the elongation factors with the ribosome during protein synthesis. The stalk is formed by a complex of five proteins, four small acidic polypeptides and a larger protein which directly interacts with the rRNA at the GTPase center. In eukaryotes, the acidic components correspond to the 12 kDa P1 and P2 proteins, and the RNA binding component is protein P0. All these proteins are found to be phosphorylated in eukaryotic organisms. Previous in vitro data suggested this modification was involved in the activity of this structure. To confirm this possibility a mutational study has shown that phosphorylation takes place at a serine residue close to the carboxyl end of proteins P1, P2 and P0. This serine is part of a consensus casein kinase II phosphorylation site. However, by using a yeast strain carrying a temperature sensitive mutant, it has been shown that CKII is probably not the only enzyme responsible for this modification. Three new protein kinases, RAPI, RAPII and RAPIII, have been purified and compared with CKII and PK60, a previously reported enzyme that phosphorylates the stalk proteins. Differences among the five enzymes have been studied. It has also been found that some typical effectors of the PKC kinase stimulate the in vitro phosphorylation of the stalk proteins. All the data available suggest that phosphorylation, although it is not involved in the interaction of the acidic proteins with the ribosome, affects ribosome activity and might participate in some ribosome regulatory mechanism.

Value of PCR for detection of Toxoplasma gondii in aqueous humor and blood samples from immunocompetent patients with ocular toxoplasmosis

Toxoplasma gondii infection is an important cause of chorioretinitis in the United States and Europe. Most cases of Toxoplasma chorioretinitis result from congenital infection. Patients are often asymptomatic during life, with a peak incidence of symptomatic illness in the second and third decades of life. Diagnosis is mainly supported by ophthalmological examination and a good response to installed therapy. However, establishment of a diagnosis by ophthalmological examination alone can be difficult in some cases. To determine the diagnostic value of PCR for the detection of T. gondii, 56 blood and 56 aqueous humor samples from 56 immunocompetent patients were examined. Fifteen patients with a diagnosis of ocular toxoplasmosis had increased serum anti-T. gondii immunoglobulin G levels but were negative for anti-T. gondii immunoglobulin M (group 1), and 41 patients were used as controls (group 2). Samples were taken before antiparasitic therapy was initiated, and only one blood sample and one aqueous humor sample were obtained for each patient. Single nested PCRs and Southern blot hybridization were performed with DNA extracted from these samples. The results obtained showed sensitivity and specificity values of 53. 3 and 83%, respectively. Interestingly, among all patients with ocular toxoplasmosis, a positive PCR result with the aqueous humor sample was accompanied by a positive PCR result with the blood sample. This result suggests that ocular toxoplasmosis should not be considered a local event, as PCR testing of blood samples from patients with ocular toxoplasmosis yielded the same result as PCR testing of aqueous humor samples. PCR testing may be useful for discriminating between ocular toxoplasmosis and other ocular diseases, and also can avoid the problems associated with ocular puncture.

Phosphorylation of the yeast ribosomal stalk. Functional effects and enzymes involved in the process

The ribosomal stalk is directly involved in the interaction of the elongation factors with the ribosome during protein synthesis. The stalk is formed by a complex of five proteins, four small acidic polypeptides and a larger protein which directly interacts with the rRNA at the GTPase center. In eukaryotes the acidic components correspond to the 12-kDa P1 and P2 proteins, and the RNA binding component is the P0 protein. All these proteins are found phosphorylated in eukaryotic organisms, and previous in vitro data suggested this modification was involved in the activity of this structure. Results from mutational studies have shown that phosphorylation takes place at a serine residue close to the carboxy end of the P proteins. Modification of this serine residue does not affect the formation of the stalk and the activity of the ribosome in standard conditions but induces an osmoregulation-related phenotype at 37 degrees C. The phosphorylatable serine is part of a consensus casein kinase II phosphorylation site. However, although CKII seems to be responsible for part of the stalk phosphorylation in vivo, it is probably not the only enzyme in the cell able to perform this modification. Five protein kinases, RAPI, RAPII and RAPIII, in addition to the previously reported CKII and PK60 kinases, are able to phosphorylate the stalk proteins. A comparison of the five enzymes shows differences among them that suggest some specificity regarding the phosphorylation of the four yeast acidic proteins. It has been found that some typical effectors of the PKC kinase stimulate the in vitro phosphorylation of the stalk proteins. All the data suggest that although phosphorylation is not involved in the interaction of the acidic P proteins with the ribosome, it can affect the ribosome activity and might participate in a possible ribosome regulatory mechanism.