Detection of blaCTX-M-15 in an integrative and conjugative element in four extensively drug-resistant Haemophilus parainfluenzae strains causing urethritis

Haemophilus parainfluenzae is a commensal organism with rising numbers of multidrug-resistant (MDR) strains. This pathogen is of increasing clinical relevance in urogenital infection. The aim of this work was to identify and characterise the molecular mechanisms of resistance associated with four cephalosporin-resistant H. parainfluenzae strains collected from patients with urethritis. Antimicrobial resistance was determined by microdilution following European Committee on Antimicrobial Susceptibility Testing criteria. Strains were then analysed by whole-genome sequencing to determine clonal relationship and the molecular basis of antimicrobial resistance. Finally, a phylogenetic analysis was performed on all urogenital MDR strains of H. parainfluenzae previously isolated in our hospital. All strains were resistant to β-lactams, macrolides, tetracycline, fluoroquinolones, chloramphenicol, cotrimoxazole, and aminoglycosides. The resistance profile was compatible with the presence of an extended-spectrum β-lactamase (ESBL). Whole-genome sequencing detected blaCTX-M-15 that conferred high minimum inhibitory concentrations to cephalosporins in two novel integrative and conjugative elements (ICEHpaHUB6 and ICEHpaHUB7) that also harboured a blaTEM-1 β-lactamase. This study shows a novel blaCTX-M-15 ESBL carried in an integrative conjugative element in four extensively drug-resistant H. parainfluenzae strains. This resistance determinant could be transmitted to other sexually transmitted pathogens and this is a cause for concern.

Activity of imipenem/relebactam against Enterobacterales and Pseudomonas aeruginosa in Spain. SMART 2016-2020

OBJECTIVE

To determine susceptibility to the novel β-lactam/β-lactamase inhibitor combination imipenem/relebactam in clinical isolates recovered from intra-abdominal (IAI), urinary (UTI), respiratory (RTI) and bloodstream (BSI) infections in the SMART (Study for Monitoring Antimicrobial Resistance Trends) study in SPAIN during 2016 - 2020.

METHODS

Broth microdilution MICs for imipenem/relebactam and comparators were determined by a central laboratory against isolates of Enterobacterales and Pseudomonas aeruginosa. MICs were interpreted using EUCAST-2021 breakpoints.

RESULTS

In total, 5,210 Enterobacterales and 1,418 P. aeruginosa clinical isolates were analyzed. Imipenem/relebactam inhibited 98.8% of Enterobacterales. Distinguishing by source of infection susceptibility was 99.1% in BSI, 99.2% in IAI, 97.9% in RTI, and 99.2% in UTI. Of intensive care unit isolates (ICU) 97.4% were susceptible and of non-ICU isolates 99.2% were susceptible. In Enterobacterales, activity against Class A, Class B and Class D carbapenemases was 96.2%, 15.4% and 73.2%, respectively. In P. aeruginosa, imipenem/relebactam was active in 92.2% of isolates. By source of infection it was 94.8% in BSI, 92.9% in IAI, 91.7% in RTI, and 93.1% in UTI. An 88.7% of ICU isolates and 93.6% of non-ICU isolates were susceptible to imipenem/relebactam. Imipenem/relebactam remained active against P. aeruginosa ceftazidime-resistant (76.3%), cefepime-resistant (73.6%), imipenem-resistant (71.5%) and piperacillin-resistant (78.7%) isolates. Of all multidrug-resistant or difficult-to-treat resistance P. aeruginosa isolates, 75.1% and 46.2%, respectively, were susceptible to imipenem/relebactam.

CONCLUSIONS

Imipenem/relebactam showed high rates of susceptibility in Enterobacterales and P. aeruginosa isolates from different sources of infection as well as depending on patients' location (ICU or non-ICU scenarios).

Antimicrobial activity of ceftolozane-tazobactam against Enterobacterales and Pseudomonas aeruginosa recovered during the Study for Monitoring Antimicrobial Resistance Trends (SMART) program in Spain (2016-2018)

OBJECTIVE

To analyse the susceptibility to ceftolozane-tazobactam and comparators in Enterobacterales and Pseudomonas aeruginosa isolates recovered from intraabdominal (IAI), urinary (UTI), respiratory (RTI) and bloodstream infection (BSI) in the SMART (Study for Monitoring Antimicrobial Resistance Trends) study.

METHODS

The susceptibility of 5,351 isolates collected in 11 Spanish hospitals (2016-2018) were analysed (EUCAST-2020 criteria) by broth microdilution and were phenotypically studied for the presence of extended-spectrum beta-lactamases (ESBL). Ceftolozane-tazobactam and/or carbapenem resistant isolates were genetically characterized for ESBL and carbapenemases.

RESULTS

Escherichia coli was the most frequent pathogen (49.3% IAI, 54.9% UTI, 16.7% RTI and 50% BSI), followed by Klebsiella pneumoniae (11.9%, 19.1%, 13.1% and 15.4%, respectively). P. aeruginosa was isolated in 9.3%, 5.6%, 32% and 9%, respectively. The frequency of isolates with ESBLs (2016-2017) was: 30.5% K. pneumoniae, 8.6% E. coli, 2.3% Klebsiella oxytoca and 0.7% Proteus mirabilis. Ceftolozane-tazobactam was very active against non-ESBL-(99.3% susceptible) and ESBL-(95.2%) producing E. coli being less active against K. pneumoniae (98% and 43.1%, respectively) isolates. CTX-M-15 was the most prevalent ESBL in E. coli (27.5%) and K. pneumoniae (51.9%) frequently associated with OXA-48-like carbapenemase. Overall, 93% of P. aeruginosa isolates were susceptible to ceftolozane-tazobactam, preserving this activity (>75%) in isolates resistant to other beta-lactams except in those resistant to meropenen or ceftazidime-avibactam. GES-5, PER-1, VIM-1/2 were the most prevalent enzymes in isolates resistant to ceftolozane-tazobactam.

CONCLUSIONS

Ceftolozane-tazobactam showed high activity rates against isolates recovered in the SMART study although it was affected in K. pneumoniae and P. aeruginosa isolates with ESBL and/or carbapenemases.

Efficacy of extended infusion of β-lactam antibiotics for the treatment of febrile neutropenia in haematologic patients: protocol for a randomised, multicentre, open-label, superiority clinical trial (BEATLE)

Background

Febrile neutropaenia (FN) is a very common complication in patients with haematological malignancies and is associated with considerable morbidity and mortality. Broad-spectrum antipseudomonal β-lactam antibiotics (BLA) are routinely used for the treatment of cancer patients with FN. However, the clinical efficacy of BLA may be diminished in these patients because they present with pathophysiological variations that compromise the pharmacokinetic (PK) parameters of these antibiotics. Optimised administration of BLA in prolonged infusions has demonstrated better clinical outcomes in critically ill patients. However, there is a paucity of data on the usefulness of this strategy in patients with FN.

The aim of this study is to test the hypothesis that the administration of BLA would be clinically more effective by extended infusion (EI) than by intermittent infusion (II) in haematological patients with FN.

Methods

A randomised, multicentre, open-label, superiority clinical trial will be performed. Patients with haematological malignancies undergoing chemotherapy or haematopoietic stem-cell transplant and who have FN and receive empirical antibiotic therapy with cefepime, piperacillin-tazobactam or meropenem will be randomised (1:1) to receive the antibiotic by EI (during half the time of the dosing interval) in the study group, or by II (30 min) in the control group.

The primary endpoint will be clinical efficacy, defined as defervescence without modifying the antibiotic treatment administered within the first 5 days of therapy. The primary endpoint will be analysed in the intention-to-treat population. The secondary endpoints will be pharmacokinetic/pharmacodynamic (PK/PD) target achievement, bacteraemia clearance, decrease in C-reactive protein, overall (30-day) case-fatality rate, adverse events and development of a population PK model of the BLA studied.

Discussion

Data on the usefulness of BLA administration in patients with FN are scant. Only three clinical studies addressing this issue have been published thus far, with contradictory results. Moreover, these studies had some methodological flaws that limit the interpretation of their findings. If this randomised, multicentre, phase IV, open-label, superiority clinical trial validates the hypothesis that the administration of BLA is clinically more effective by EI than by II in haematological patients with FN, then the daily routine management of these high-risk patients could be changed to improve their outcomes.

Trial registration

European Clinical Trials Database: EudraCT 2018–001476-37.

ClinicalTrials.gov, ID: NCT04233996.

Assessment of trimethoprim-sulfamethoxazole susceptibility testing methods for fastidious Haemophilus spp

OBJECTIVES

To compare the determinants of trimethoprim-sulfamethoxazole resistance with established susceptibility values for fastidious Haemophilus spp., to provide recommendations for optimal trimethoprim-sulfamethoxazole measurement.

METHODS

We collected 50 strains each of Haemophilus influenzae and Haemophilus parainfluenzae at Bellvitge University Hospital. Trimethoprim-sulfamethoxazole susceptibility was tested by microdilution, E-test and disc diffusion using both Mueller-Hinton fastidious (MH-F) medium and Haemophilus test medium (HTM) following EUCAST and CLSI criteria, respectively. Mutations in folA, folP and additional determinants of resistance were identified in whole-genome-sequenced isolates.

RESULTS

Strains presented generally higher rates of trimethoprim-sulfamethoxazole resistance when grown on HTM than on MH-F, independent of the methodology used (average MIC 2.6-fold higher in H. influenzae and 1.2-fold higher in H. parainfluenzae). The main resistance-related determinants were as follows: I95L and F154S/V in folA; 3- and 15-bp insertions and substitutions in folP; acquisition of sul genes; and FolA overproduction potentially linked to mutations in -35 and -10 promoter motifs. Of note, 2 of 19 H. influenzae strains (10.5%) and 9 of 33 H. parainfluenzae strains (27.3%) with mutations and assigned as resistant by microdilution were inaccurately considered susceptible by disc diffusion. This misinterpretation was resolved by raising the clinical resistance breakpoint of the EUCAST guidelines to ≤30 mm.

CONCLUSIONS

Given the routine use of disc diffusion, a significant number of strains could potentially be miscategorized as susceptible to trimethoprim-sulfamethoxazole despite having resistance-related mutations. A simple modification to the current clinical resistance breakpoint given by the EUCAST guideline for MH-F ensures correct interpretation and correlation with the reference standard method of microdilution.

Control of endemic multidrug-resistant Gram-negative bacteria after removal of sinks and implementing a new water-safe policy in an intensive care unit

BACKGROUND

Contaminated handwashing sinks have been identified as reservoirs that can facilitate colonization/infection of patients with multidrug-resistant (MDR) Gram-negative bacteria (GNB) in intensive care units (ICUs).

AIM

To assess the impact of removing patients' sinks and implementing other water-safe strategies on the annual rates of ICU-acquired MDR-GNB.

METHODS

This six-year quasi-experimental study was conducted from January 2011 to December 2016. The intervention was carried out in August 2014 in two adult ICU wards with 12 rooms each. To assess the changes in annual MDR-GNB rates before and after the intervention, we used segmented regression analysis of an interrupted time-series. Crude relative risk (RR) rates were also calculated.

FINDINGS

The incidence rates of MDR-GNB were 9.15 and 2.20 per 1000 patient-days in the pre- and post-intervention periods, respectively. This yielded a crude RR of acquiring MDR-GNB of 0.24 (95% confidence interval: 0.17-0.34). A significant change in level was observed between the MDR-GNB rate at the first point of the post-intervention period and the rate predicted by the pre-intervention time trend.

CONCLUSION

The implementation of a new water-safe policy, which included the removal of sinks from all patient rooms, successfully improved the control of MDR-GNB spread in an ICU with endemic infection. Our results support the contribution of sink use with the incidence of MDR-GNB in endemic environments.

Mortality risk factors among non-ICU patients with nosocomial vascular catheter-related bloodstream infections: a prospective cohort study

BACKGROUND

Vascular catheter-related bloodstream infections (CRBSIs) are highly preventable hospital-acquired infections and a major threat to patient safety. While there is significant information regarding CRBSI outcome among intensive care unit (ICU) patients, data regarding non-ICU patients are scarce.

AIM

To determine the risk factors associated with 30-day mortality among non-ICU patients with nosocomial CRBSIs.

METHODS

Prospective cohort study of non-ICU patients with nosocomial CRBSIs in a tertiary care centre between January 2004 and December 2014. The primary outcome was 30-day mortality, defined as death from any cause within 30 days of CRBSI. Follow-up was performed 30 days after CRBSI onset. Time until death was the dependent variable in Cox regression analysis.

FINDINGS

In total, 546 cases of CRBSI were identified. The mean age of patients was 64.5 years [interquartile range (IQR) 55-75 years], 66% were male, and the mean Charlson score was 3.59 (IQR 2-5). Of the 546 cases, 58.4% resulted from central venous catheters and 41.6% from peripheral venous catheters. The causative agents were Gram-positive cocci (70.1% of cases), Gram-negative bacilli (31.1%) and Candida spp. (1%). Mortality within 30 days was 13.9%, with no significant changes over the study period. Independent risk factors for 30-day mortality were Charlson score ≥4 [hazard ratio (HR) 1.80, 95% confidence interval (CI) 1.19-2.73], Staphylococcus aureus infection (HR 2.67, 95% CI 1.61-4.43) and Candida spp. infection (HR 6.1, 95% CI 2.08-18.04). Age; area of admission; type, use and site of vascular catheter; and administration of appropriate empirical antibiotic treatment were not independent risk factors for 30-day mortality.

CONCLUSION

Nosocomial CRBSIs outside ICUs are associated with high risk of mortality, particularly among patients with a higher Charlson score and bloodstream infections caused by Staphylococcus aureus and Candida spp.

Characteristics, aetiology, antimicrobial resistance and outcomes of bacteraemic cholangitis in patients with solid tumours: A prospective cohort study

OBJECTIVES

To asses the clinical features, aetiology, antimicrobial resistance and outcomes of bacteraemic cholangitis in patients with solid tumours (ST).

METHODS

All consecutive episodes of bacteraemia in hospitalized patients were prospectively analysed (2006-2015).

RESULTS

Of 1852 episodes of bacteraemia, 750 involved patients with ST. Among them, 173 episodes (23%) were due to cholangitis. The most frequent neoplasms were hepato-biliary-pancreatic tumours (68.2%) and gastrointestinal cancer (18.5%); 57.2% of patients had a biliary stent in place. The most frequent causative agents were Escherichia coli (39.3%) followed by Klebsiella pneumoniae (15.1%) and Enterococcus faecium (7.8%). Forty-one episodes (18.7%) were caused by multidrug-resistant (MDR) microorganisms. Patients with a second episode of cholangitis were more likely to have an MDR isolate and to had received inadequate empirical antibiotic therapy. 7-day and 30-day case-fatality rates were 7.6% and 26%, respectively. The only risk factors independently associated with 30-day case-fatality rate were corticosteroids and malignancy-related complications.

CONCLUSIONS

Bacteraemic cholangitis is frequent in patients with ST, and is mainly caused by Enterobacteriaceae and E. faecium. The emergence of MDR is of special concern, particularly in patients with a second episode of bacteraemia. Case-fatality rates are high, especially among patients receiving corticosteroids and presenting malignancy-related complications.

Hypervirulent Klebsiella pneumoniae clones causing bacteraemia in adults in a teaching hospital in Barcelona, Spain (2007-2013)

Virulent hypermucoviscous Klebsiella pneumoniae strains associated with the magA and rmpA genes have mainly emerged in Asia. We analysed the frequency and the clinical and molecular epidemiology of K. pneumoniae bacteraemia isolates obtained over a 7-year period (2007-2013). Fifty-three of 878 K. pneumoniae invasive isolates (5.4%) showed a hypermucoviscous phenotype (by the string test). Of these, 16 (30.2%) were magA(+)/rmpA(+), 12 (22.6%) were magA(-)/rmpA(+), and the remaining 25 (47.2%) were magA(-)/rmpA(-). After multilocus sequence typing and wzi sequencing, all magA(+)/rmpA(+) isolates were serotype K1 and sequence type (ST)23. Of the 12 magA(-)/rmpA(+) isolates, nine were K2 (ST380, ST86, ST65, ST25 and ST493), and three magA(-)/rmpA(+) isolates had the new wzi allele 122, an unknown serotype, and the new ST1013. The remaining isolates, which were magA(-)/rmpA(-), showed different serotypes and STs. Patients with magA(+)/rmpA(+) or magA(-)/rmpA(+)K. pneumoniae bacteraemia more frequently had pyogenic liver abscesses (PLAs) and pneumonia than patients with magA(-)/rmpA(-)K. pneumoniae bacteraemia (respectively: 21.4% vs. 8%, p 0.26; and 17.9% vs. 0%, p 0.05). In fact, magA(-)/rmpA(-) isolates were similar to the those termed 'classic' K. pneumoniae isolates causing bacteraemia, the urinary and biliary tracts being the main foci of infection. In conclusion, hypervirulent clones (CC23K1, CC86K2, CC65K2, and CC380K2) were infrequent among K. pneumoniae isolates causing bacteraemia in our geographical area. A hypermucoviscous phenotype as determined with the string test is not enough to recognize these clones; additional molecular studies are needed. Patients with magA(+) and/or rmpA(+)K. pneumoniae bacteraemia more frequently had PLAs and pneumonia than patients without hypermucoviscosity genes.

Experimental study of cerebrospinal fluid tumor necrosis factor-alpha release in penicillin- and cephalosporin-resistant pneumococcal meningitis treated with different antibiotic schedules

BACKGROUND/PURPOSE

To measure the inflammatory response in terms of tumor necrosis factor-alpha (TNF-α) levels in cerebrospinal fluid (CSF), using bacteriolytic versus nonbacteriolytic antibiotic therapy and adjunctive treatment with dexamethasone in an experimental rabbit model of pneumococcal meningitis.

METHODS

In a rabbit model of pneumococcal meningitis, we tested CSF TNF-α levels in several samples from rabbits infected with the HUB 2349 strain and treated with ceftriaxone 100 mg/kg/d, ceftriaxone plus vancomycin 30 mg/kg/d, or daptomycin at 15 mg/kg or 25 mg/kg. Daptomycin schedules were compared with the same doses in combination with dexamethasone at 0.125 mg/kg every 12 hours over a 26-hour period.

RESULTS

The ceftriaxone group had the highest levels of TNF-α. TNF-α levels were significantly higher after ceftriaxone administration than in both daptomycin groups. The high-dose daptomycin group presented the lowest inflammatory levels in CSF samples. Adjunctive treatment with dexamethasone in this group modulated the inflammatory response, bringing down CSF TNF-α levels.

CONCLUSION

CSF TNF-α levels were significantly lower in rabbits treated with daptomycin than in rabbits treated with ceftriaxone. Daptomycin avoided the inflammatory peak after administration observed in ceftriaxone-treated rabbits. The use of daptomycin plus dexamethasone achieved a significantly larger reduction in CSF TNF-α levels.

Effect of dexamethasone on the efficacy of daptomycin in the therapy of experimental pneumococcal meningitis

This study aimed to determine the effect of dexamethasone in combination with low-dose or high-dose daptomycin for the treatment of penicillin- and cephalosporin-resistant pneumococcal meningitis. Efficacy (ΔCFU/mL) and cerebrospinal fluid (CSF) levels of daptomycin at 15mg/kg and 25mg/kg were studied in a rabbit model of pneumococcal meningitis, comparing them with the same doses in combination with dexamethasone at 0.125mg/kg every 12h over a 26-h period against two different Streptococcus pneumoniae strains, HUB 2349 and ATCC 51916 with daptomycin minimum inhibitory concentrations (MICs) of 0.09mg/L and 0.19mg/L, respectively. Daptomycin levels in CSF were lower when dexamethasone was given concurrently. Against strain HUB 2349, therapeutic failure occurred with daptomycin 15mg/kg+dexamethasone; daptomycin 25mg/kg+dexamethasone was better at reducing bacterial counts than the lower dose throughout treatment. Against the highly cephalosporin-resistant ATCC 51916 strain, daptomycin 15mg/kg+dexamethasone achieved a lower bacterial decrease than daptomycin 15mg/kg alone, and therapeutic failure at 24h occurred in the daptomycin 15mg/kg+dexamethasone group. Addition of dexamethasone to a 25mg/kg daptomycin dose did not affect the efficacy of daptomycin: it remained bactericidal throughout treatment. In conclusion, against the studied strains, low-dose (15mg/kg/day) daptomycin is affected by concomitant use of dexamethasone: CSF levels are reduced and its bacterial efficacy is affected. At a higher daptomycin dose (25mg/kg/day), however, the use of dexamethasone does not alter efficacy; the combination appears to be a good choice for the treatment of pneumococcal meningitis.

Impact of multidrug resistance on Pseudomonas aeruginosa ventilator-associated pneumonia outcome: predictors of early and crude mortality

The prevalence of multidrug-resistant (MDR) Pseudomonas aeruginosa has increased over the past decade and a significant rise in these isolates in ventilator-associated pneumonia (VAP) has been observed. However, the impact of MDR on VAP outcome has not been analysed in depth. We investigated the risk factors for early and crude mortality in a retrospective study of microbiologically and clinically documented VAP. Ninety-one VAP episodes in 83 patients were included, 31 caused by susceptible P. aeruginosa and 60 by MDR strains, of which 42 (70 %) were extensively drug-resistant (XDR) P. aeruginosa. Thirteen episodes concomitantly presented P. aeruginosa bacteraemia, in seven of which the origin was the respiratory tract. Whereas susceptible P. aeruginosa episodes were more likely than MDR episodes to receive adequate empirical (68 % vs. 30 %; p < 0.001) and definitive antimicrobial therapy (96 % vs. 50 %; p < 0.001), susceptible P. aeruginosa VAP presented a trend towards early mortality (29 % vs. 15 %; p = 0.06). A logistic regression model with early mortality as the dependent variable identified multiorgan dysfunction syndrome (MODS) [odds ratio (OR) 10.4; 95 % confidence interval (CI) 1.7-63.5; p = 0.01] and inadequate antibiotic therapy (OR 4.27; 95 % CI 0.98-18.4; p = 0.052) as independent risk factors for early mortality. A similar analysis identified MODS (OR 4.31; 95 % CI 1.14-16.2; p = 0.03) as the only independent predictor of crude mortality. The severity of acute illness clinical presentation was the main predictor of mortality. Despite adequate antibiotic therapy, susceptible P. aeruginosa seems to cause major early mortality. Although adequate therapy is essential to treat VAP, the severity of acute illness is a more important factor than drug resistance.

Changing aetiology, clinical features, antimicrobial resistance, and outcomes of bloodstream infection in neutropenic cancer patients

Recent changes in the management of patients with haematological malignancies might have influenced the aetiology, characteristics, antimicrobial resistance and outcomes of bloodstream infection (BSI) during neutropenia. We compared 272 episodes of BSI in adult neutropenic patients with cancer prospectively collected from January 1991 to December 1996 (first period), when quinolone prophylaxis was used, with 283 episodes recorded from January 2006 to March 2010 (second period), when antibacterial prophylaxis was stopped. Patients in the second period were significantly older and were more likely to have graft-versus-host disease and a urinary catheter in place, whereas the presence of a central venous catheter, parenteral nutrition, corticosteroids and antifungal and quinolone prophylaxis, were more frequent in the first period. More patients in the first period had mucositis and soft-tissue infection as the origin of BSI, but an endogenous source was more common during the second. Gram-positive BSI was more frequent in the first period (64% versus 41%; p <0.001), mainly due to coagulase-negative staphylococci and viridans group streptococci. In the second period gram-negative BSI increased (28% versus 49%; p <0.001), quinolone susceptibilities were recovered, but multidrug-resistant gram-negative BSI also increased (1% versus 6%; p <0.001). Although patients in the second period were more likely to need admission to the intensive-care unit, overall case-fatality rate was similar in the two periods (19% versus 15%). The aetiology of BSI in neutropenic patients with cancer has shifted from gram-positive to gram-negative organisms. Multidrug resistance among gram-negative bacilli is emerging as a therapeutic challenge. Overall case-fatality rate remains high.

Efficacy of fosfomycin and its combination with linezolid, vancomycin and imipenem in an experimental peritonitis model caused by a Staphylococcus aureus strain with reduced susceptibility to vancomycin

The objective of this study was to evaluate the in vitro and in vivo efficacies of therapies including fosfomycin against clinical Staphylococcus aureus isolates with reduced susceptibility to vancomycin (hGISA). Time-kill curves were performed over 24 h. Peritonitis in C57BL/6 mice was induced by intraperitoneal inoculation of 10(8) CFU/ml. Four hours later (0 h), therapy was started and the treatment groups were: control (not treated), fosfomycin (100 mg/kg/5 h), vancomycin (60 mg/kg/5 h), imipenem (30 mg/kg/5 h), fosfomycin plus linezolid, fosfomycin plus vancomycin and fosfomycin plus imipenem, receiving subcutaneous therapy over 25 h. Bacterial counts in peritoneal fluid, bacteraemia and mortality rates were determined. In vitro, fosfomycin showed a synergistic effect when combined with the other antimicrobials tested. In the animal model, fosfomycin combinations were effective and significantly reduced the bacteraemia rates achieved in the control, imipenem and vancomycin groups (p < 0.05). The best combination in vivo was fosfomycin plus imipenem. Also, fosfomycin plus linezolid was significantly better than vancomycin alone, reducing the bacterial concentration in the peritoneal fluid. In conclusion, in vitro and in vivo, fosfomycin in combination with linezolid, vancomycin or imipenem exerted a good activity. Fosfomycin plus imipenem was the most active combination, decreasing 3 log CFU/ml, and appears to be a promising combination for clinical practice.

Infections due to Escherichia coli producing extended-spectrum beta-lactamase among hospitalised patients: factors influencing mortality

We performed a retrospective matched-cohort study to determine the risk factors for mortality among patients with Escherichia coli infections. From January 1996 to December 2003, 100 hospitalised patients with extended-spectrum beta-lactamase (ESBL)-producing E. coli infections were compared with patients not infected with ESBL-producing E. coli. These patients were selected according to the same site of infection and the closest date of admission. Comparison of the two groups showed that empirical antibiotic therapy was more often inadequate in patients infected with ESBL-producing E. coli (44% vs 15%; P<0.01), and that early mortality (16% vs 6%; P=0.02) and overall mortality (25% vs 11%; P=0.01) were also significantly higher in patients with ESBL-producing E. coli infections. A multivariate model identified the urinary tract focus as the only independent risk factor influencing early mortality for E. coli infections [odds ratio (OR): 0.1; 95% confidence interval (CI): 0.03-0.7; P=0.01]. All 12 patients with ESBL-producing E. coli urinary tract infections treated initially with an oxyimino-beta-lactam survived. Subsequent analysis of the factors influencing early mortality in the cohort of 130 patients with a non-urinary E. coli infection found inadequate empirical antibiotic therapy as an independent risk factor for mortality only for non-urinary E. coli infections (adjusted OR: 3.0; 95% CI: 1.0-8.6; P=0.03). The study showed that hospitalised patients with ESBL-producing E. coli infections more often receive inadequate empiric antibiotic therapy and have a higher mortality rate than those infected with non-ESBL-producing strains. The site of infection strongly influences mortality. The administration of inadequate empirical antibiotic therapy is independently associated with higher mortality only among patients with non-urinary tract infections.

Nosocomial spread of Pseudomonas aeruginosa producing the metallo-β-lactamase VIM-2 in a Spanish hospital: clinical and epidemiological implications

Thirty-four isolates of pan-resistant Pseudomonas aeruginosa producing VIM-2 metallo-beta-lactamase (MBL) were detected at a university hospital in Spain (July 2004-September 2006). Eleven (32%) patients had clinically significant infections, and three (27%) of these patients died. A single clone of MBL-producing P. aeruginosa was identified by pulsed-field gel electrophoresis. A cluster of isolates associated with the vascular surgery ward involved ten patients and appeared as a series of low-grade, sustained and misdiagnosed endemic infections in the hospital. The identification of MBL-positive P. aeruginosa should be considered mandatory in the surveillance of pan-resistant P. aeruginosa and requires a high index of suspicion in the context of endemic infections with a low attack rate.

Effects of carbapenem exposure on the risk for digestive tract carriage of intensive care unit-endemic carbapenem-resistant Pseudomonas aeruginosa strains in critically ill patients

To determine the epidemiology and risk factors for carbapenem-resistant Pseudomonas aeruginosa (CR-PA) digestive tract colonization, weekly rectal and pharyngeal swabs were obtained in two serial incidence surveys (266 patients). Forty-two (16%) patients were CR-PA colonized (12 [29%] on admission and 30 [71%] in intensive care units). Pulsed-field gel electrophoresis showed extensive clonal diversity, although one specific clone (type B) was isolated from 11 patients. The presence of similar genotypes of CR-PA colonizing 30% of the CR-PA-colonized patients suggests the occurrence of cross-colonization; in addition, 10 pairs of carbapenem-susceptible P. aeruginosa (CS-PA) and subsequent CR-PA strains isolated from the same patients were found to be clonally identical and were considered to have been endogenously acquired (33%). All endogenously acquired CR-PA strains were isolated after exposure to a carbapenem, and 80% showed a phenotype of imipenem resistance (IR pattern) alone, while 67% of the CR-PA strains acquired by cross-transmission exhibited a multiresistant (MR) phenotype, with previous carbapenem exposure in 44%. Logistic regression analysis identified severity of acute illness (odds ratio [OR], 1.0; 95% confidence interval [CI], 1.0 to 1.1), prior carbapenem use (OR, 7.8; 95% CI, 1.7 to 35.3), and prior use of fluoroquinolones (OR, 11.0; 95% CI, 1.7 to 67.9) as independent risk factors for CR-PA digestive tract colonization. Overall, the local epidemiology of CR-PA digestive tract colonization was characterized by polyclonal endemicity with phenotype patterns of IR and MR divided evenly between patients. Restricting the use of particular agents, such as carbapenems and fluoroquinolones, should be considered advisable to minimize the problem of this antibiotic resistance. However, the possible risk for development of collateral unexpected bacterial resistance patterns should be accurately monitored.

Efficacy of high doses of levofloxacin in experimental foreign-body infection by methicillin-susceptible Staphylococcus aureus

Antimicrobial efficacy in orthopedic device infections is diminished because of bacterial biofilms which express tolerance to antibiotics. Recently, the use of high doses of levofloxacin with rifampin has been recommended for staphylococcal infections. In the present study, we evaluated the efficacy of levofloxacin at doses of 50 mg/kg/day and 100 mg/kg/day (mimicking the usual and high human doses of 500 mg/day and 750 to 1,000 mg/day, respectively) and compared it to that of to linezolid, cloxacillin, vancomycin, and rifampin in a rat tissue cage model of experimental foreign-body infection by Staphylococcus aureus. The antimicrobial efficacy in vitro (by MIC, minimum bactericidal concentration, and kill curves) for logarithmic- and stationary-phase bacteria was compared with the in vivo efficacy. In vitro bactericidal activity at clinically relevant concentrations was reached by all drugs except rifampin and linezolid in the log-phase studies but only by levofloxacin in the stationary-phase studies. The bacterial count decreases from in vivo tissue cage fluids (means) for levofloxacin at 50 and 100 mg/kg/day, rifampin, cloxacillin, vancomycin, linezolid, and controls, respectively, were: -1.24, -2.26, -2.1, -1.56, -1.47, -1.15, and 0.33 (all groups versus controls, P < 0.05). Levofloxacin at 100 mg/kg/day (area under the concentration-time curve/MIC ratio, 234) was the most active therapy (P = 0.03 versus linezolid). Overall, in vivo efficacy was better predicted by stationary-phase studies, in which it reached a high correlation coefficient even if the rifampin group was excluded (r = 0.96; P < 0.05). Our results, including in vitro studies with nongrowing bacteria, pharmacodynamic parameters, and antimicrobial efficacy in experimental infection, provide good evidence to support the use of levofloxacin at high doses (750 to 1,000 mg/day), as recently recommended for treating patients with orthopedic prosthesis infections.

Effect of prior pneumococcal vaccination on clinical outcome of hospitalized adults with community-acquired pneumococcal pneumonia

The aim of this study was to evaluate the effect of prior pneumococcal vaccination on the clinical outcome of 554 consecutive hospitalized adults with community-acquired pneumococcal pneumonia from 1995 to 2004, 61 of whom had been vaccinated in the 5 years before admission. Outcome variables that were compared in vaccinated and unvaccinated adults included the occurrence of bacteremia, the time to resolution of pneumonia symptoms, the length of hospital stay, and mortality. Prior pneumococcal vaccination was associated with a lower risk of bacteremia (odds ratio 0.46, 95% CI 0.22-0.98). Compared with unvaccinated patients, vaccine recipients had better clinical outcomes, which included a faster resolution of pneumonia symptoms. The median length of hospital stay was shorter in vaccinated patients (8.0 vs. 9.0 days; p=0.032). Overall case-fatality rates did not differ significantly between groups (1.6% vs. 6.2%; p=0.233). In conclusion, prior pneumococcal vaccination appears to be associated with a lower risk of bacteremia, a faster time to resolution of symptoms, and a shorter hospital stay in adults with pneumococcal pneumonia. The findings presented here provide additional support to the current vaccine recommendations and should encourage healthcare providers to increase pneumococcal vaccine coverage among targeted adult populations.

Risk-factors for acquisition of extended-spectrum β-lactamase-producing Escherichia coli among hospitalised patients

Between 1996 and 2002, 103 hospitalised patients yielding one or more clinical isolates of extended-spectrum beta-lactamase-producing Escherichia coli (ESBL-EC) were identified. A significant increase was observed in the incidence of ESBL-EC colonisation or infection during the study period (1.65 episodes/100 000 patient-days in 1996 to 12.6 episodes/100 000 patient-days in 2002; p 0.01). Infection developed in 70 (68%) patients (75 episodes), with surgical site (44%) and urinary tract (17%) infections being the most frequent. Pulsed-field gel electrophoresis showed extensive clonal diversity among the isolates. A case-control study and multivariate analysis identified female gender (OR 2.1; p 0.01), use of a nasogastric tube (OR 3.5; p 0.001) and previous antibiotic therapy (OR 3.9; p < 0.001) as independent variables associated with acquisition of ESBL-EC. The study demonstrated a progressive increase in the number of ESBL-EC isolates in a non-epidemic setting. Most cases of ESBL-EC colonisation or infection occurred in hospitalised patients exposed to invasive procedures and antibiotic pressure.

Gammagrafía con 99mTc-ceftizoxima en ratas normales y en ratas con absceso inducido

This study aimed to investigate the biodistribution of the 99mTc-ceftizoxime in normal rats and in rats bearing septic and sterile induced abscess.

MATERIAL AND METHODS

Three groups of rats were studied. a) Six normal rats b) 15 rats with E. coli induced abscess and c) 15 rats with sterile zymosan induced abscess. Septic abscess was induced with 2 x 10(8) colony forming units of E. coli and sterile one with 0.1 mL of 5% sterile Zymosan. 24 h after the abscess induction, 12 MBq of 99mTc-CFT were injected iv. and whole body images were collected at 30 min, 1, 2, 4 and 6 h p.i. Areas of interest were drawn and lesion/background index was calculated. The 6 normal rats were scanned at the same times, killed at 6 h p.i and kidney, liver, spleen, lung, heart and muscle activity were measured. Each organ was weighed, cut and its activity measured. Parallelly, the biological activity of the labeled antibiotic and its binding to the E. coli and S. aureus bacteria were analyzed.

RESULTS

High biliary excretion was seen in all rats. Organ measurement showed the maximal uptake in kidney and very low uptake in muscles. Mean +/- s.d abscess/background ratio at 30 min, 1, 2, 4 and 6 h were 2.60 +/- 0.36, 2.67 +/- 0.66, 2.6 0 +/- 0.58, 2.78 +/- 0.84, 3.24 +/- 1.00 for septic abscess and 2.37 +/- 0.39, 2.10 +/- 0.38, 1.97 +/- 0.34, 1.82 +/- 0.25, 1.65 +/- 0.23 for aseptic abscess. The 99mTc-CFT uptake was significantly higher in the septic abscess than in sterile one (p < 0.05). The 99mTc-CFT uptake in the septic abscess remains stable or increases until along the 6 h. The 99mTc-CFT uptake in the aseptic abscess decreases along the time.

CONCLUSIONS

The scintigraphy with 99mTc-CFT seems able to differentiate sterile inflammation from infection. High biliary excretion limits its application in abdomen. Main application could be diagnosis of osteoarticular infection.

Experimental study of teicoplanin, alone and in combination, in the therapy of cephalosporin-resistant pneumococcal meningitis

OBJECTIVES

The aim of the study was to determine the efficacy of teicoplanin, alone and in combination with ceftriaxone, in a rabbit model of cephalosporin-resistant pneumococcal meningitis, and to assess the effect of concomitant therapy with dexamethasone.

METHODS

In vitro killing curves of teicoplanin, with and without ceftriaxone, were performed. Groups of eight animals per treatment were inoculated with a cephalosporin-resistant pneumococcal strain (penicillin MIC, 4 mg/L; ceftriaxone MIC, 2 mg/L; teicoplanin MIC, 0.03 mg/L) and treated over a 26 h period. Teicoplanin was administered at a dose of 15 mg/kg, alone and in combination with ceftriaxone at 100 mg/kg with or without dexamethasone at 0.25 mg/kg. CSF samples were collected at different time-points, and bacterial titres, white blood cell counts, lactate and protein concentrations and bacteriostatic/bactericidal titres were determined. Blood and CSF teicoplanin pharmacokinetic and pharmacodynamic parameters were determined.

RESULTS

Teicoplanin alone promoted a decrease in bacterial counts at 6 h of -2.66 log cfu/mL and was bactericidal at 24 h, without therapeutic failures. Similar good results were obtained when dexamethasone was used simultaneously, in spite of the penetration of teicoplanin into the CSF being significantly reduced, from 2.31% to 0.71%. Teicoplanin and ceftriaxone combinations were synergic in vitro, but not in the meningitis model.

CONCLUSIONS

Teicoplanin alone was very effective in this model of cephalosporin-resistant pneumococcal meningitis. The use of concomitant dexamethasone resulted in lower CSF teicoplanin levels, but not in therapeutic failures. The combination of teicoplanin plus ceftriaxone and dexamethasone might be a good alternative for the empirical therapy of pneumococcal meningitis. Additional data should confirm our experiments, in advance of clinical trials to assess efficacy in humans.

Experimental Study of Clinafloxacin Alone and in Combination in the Treatment of Ciprofloxacin-Susceptible and -Resistant Pneumococcal Meningitis

The increasing incidence of ciprofloxacin resistance in Streptococcus pneumoniae may limit the efficacy of the new quinolones in difficult-to-treat infections such as meningitis. The aim of the present study was to determine the efficacy of clinafloxacin alone and in combination with teicoplanin and rifampin in the therapy of ciprofloxacin-susceptible and ciprofloxacin-resistant pneumococcal meningitis in rabbits. When used against a penicillin-resistant ciprofloxacin-susceptible strain (Clinafloxacin MIC 0.12 microg/ml), clinafloxacin at a dose of 20 mg/kg per day b.i.d. decreased bacterial concentration by -5.10 log cfu/ml at 24 hr. Combinations did not improve activity. The same clinafloxacin schedule against a penicillin- and ciprofloxacin-resistant strain (Clinafloxacin MIC 0.5 microg/ml) was totally ineffective. Our data suggest that a moderate decrease in quinolone susceptibility, as indicated by the detection of any degree of ciprofloxacin resistance, may render these antibiotics unsuitable for the management of pneumococcal meningitis.

Efficacy and safety of sequential amoxicillin-clavulanate in the treatment of anaerobic lung infections

In order to assess the efficacy and safety of amoxicillin-clavulanate for the treatment of anaerobic lung infection, 40 patients with lung abscess or necrotizing pneumonia were given sequential amoxicillin-clavulanate therapy. All patients received intravenous amoxicillin-clavulanate (2 g/200 mg/8 h), which was switched to oral form (1 g/125 mg/8 h) after clinical improvement. Mean duration of antibiotic therapy was 43.5 days. Microbiological documentation was obtained in 53% of cases. All but 1 of the 48 microorganisms isolated were susceptible to amoxicillin-clavulanate. The drug was well tolerated by the patients and no severe adverse effects were observed. At the end of treatment all patients were considered cured. The 35 patients assessed at long-term follow-up visit remained disease-free.

Efficacy of colistin versus beta-lactams, aminoglycosides, and rifampin as monotherapy in a mouse model of pneumonia caused by multiresistant Acinetobacter baumannii

The treatment of life-threatening infections due to carbapenem-resistant Acinetobacter baumannii has become a serious challenge for physicians worldwide. Often, only colistin shows in general good in vitro activity against these carbapenem-resistant strains, but its antibacterial efficacy in comparison with the antibiotics most used in clinical practice is not well known. We studied the efficacy of colistin versus those of imipenem, sulbactam, tobramycin, and rifampin in an experimental pneumonia model with immunocompetent mice. We used three strains of A. baumannii corresponding to the main clones (A, D, and E) involved in the outbreaks of our hospital, with different grades of resistance to imipenem (imipenem MICs of 1, 8, and 512 microg/ml, respectively) and to the other antibiotics. The MIC of colistin was 0.5 microg/ml for the three strains. Reduction of log(10) CFU/g in lung bacterial counts, clearance of bacteremia, and survival versus results with controls were used as parameters of efficacy. Imipenem and sulbactam (Deltalung counts: -5.38 and -4.64 log(10) CFU/ml) showed the highest level of bactericidal efficacy in infections by susceptible and even intermediate strains. Tobramycin and rifampin (-4.16 and -5.15 log(10) CFU/ml) provided good results against intermediate or moderately resistant strains, in agreement with killing curves and pharmacodynamics. On the contrary, colistin showed the weakest antibacterial effect among the antibiotics tested, both in killing curves and in the in vivo model (-2.39 log(10) CFU/ml; P < 0.05). We conclude that colistin did not appear as a good option for treatment of patients with pneumonia due to carbapenem-resistant A. baumannii strains. Other alternatives, including combinations with rifampin, may offer better therapeutic profiles and thus should be studied.

Experimental study of the efficacy of vancomycin, rifampicin and dexamethasone in the therapy of pneumococcal meningitis

The object of the study was to assess the efficacy of rifampicin and the combination of rifampicin plus vancomycin in a rabbit model of experimental penicillin-resistant pneumococcal meningitis. We also studied the effect of concomitant dexamethasone on the CSF antibiotic levels and inflammatory parameters. The rabbit model of pneumococcal meningitis was used. Groups of eight rabbits were inoculated with 106 cfu/mL of a cephalosporin-resistant pneumococcal strain (MIC of cefotaxime/ceftriaxone 2 mg/L). Eighteen hours later they were treated with rifampicin 15 mg/kg/day, vancomycin 30 mg/kg/day or both plus minus dexamethasone (0.25 mg/kg/day) for 48 h. Serial CSF samples were withdrawn to carry out bacterial counts, antibiotic concentration and inflammatory parameters. Rifampicin and vancomycin promoted a reduction of >3 log cfu/mL at 6 and 24 h, and cfu were below the level of detection at 48 h. Combination therapy with vancomycin plus rifampicin was not synergic but it had similar efficacy to either antibiotic alone and it was able to reduce bacterial concentration below the level of detection at 48 h. Concomitant use of dexamethasone decreased vancomycin levels when it was used alone (P< 0.05), but not when it was used in combination with rifampicin. Rifampicin alone at 15 mg/kg/day produced a rapid bactericidal effect in this model of penicillin-resistant pneumococcal meningitis. The combination of vancomycin and rifampicin, although not synergic, proved to be equally effective. Using this combination in the clinical setting may allow rifampicin administration without emergence of resistance, and possibly concomitant dexamethasone administration without significant interference with CSF vancomycin levels.

Relationship between penicillin and cephalosporin resistance of Streptococcus pneumoniae strains and its inflammatory activity in the experimental model of meningitis

Using a rabbit model of meningitis, we sought to compare the inflammatory activity induced by three pneumococcal strains with different susceptibilities to penicillin and cephalosporins, belonging to the serotypes 3, 6B and 23F at different inoculum sizes. These serotypes are prevalent in Western Europe and are believed to produce a moderate-to-severe cerebrospinal fluid (CSF) inflammatory response. Only minor differences were observed in the inflammatory activity evoked by the three strains in the subarachnoid space, and most were probably related to differences in bacterial counts. Infection by serotype 23F caused secondary bacteremia in all challenged animals. Our findings reinforce the concept that resistant pneumococci are not more virulent, a fact that should be taken into account when evaluating the efficacy of different anti-pneumococcal therapies. However, the frequent induction of secondary bacteremia by the resistant serotype 23F requires further study.

Usefulness of betalactam therapy for community-acquired pneumonia in the era of drug-resistant Streptococcus pneumoniae: a randomized study of amoxicillin-clavulanate and ceftriaxone

Empirical antibiotic therapy of community-acquired pneumonia (CAP) has been complicated by the worldwide emergence of penicillin resistance among Streptococcus pneumoniae. The impact of this resistance on the outcome of patients hospitalized for CAP, empirically treated with betalactams, has not been evaluated in a randomized study. We conducted a prospective, randomized trial to assess the efficacy of amoxicillin-clavulanate (2 g/200 mg/8 hr) and ceftriaxone (1 g/24 hr) in a cohort of patients hospitalized for moderate-to-severe CAP. Three-hundred seventy-eight patients were randomized to receive amoxicillin-clavulanate (184 patients) or ceftriaxone (194 patients). Efficacy was assessed on Day 2, after completion of therapy and at long term follow-up. There were no significant differences in outcomes between treatment groups, both in intention-to-treat and per-protocol analysis. Overall mortality was 10.3% for amoxicillin-clavulanate and 8.8% for ceftriaxone (NS). There were 116 evaluable patients with proven pneumococcal pneumonia. Rates of high-level penicillin resistance (MIC of penicillin > or = 2 microg/mL) were similar in the two groups (8.2 and 10.2%). Clinical efficacy at the end of therapy was 90.6% for amoxicillin-clavulanate and 88.9% for ceftriaxone (95% C.I. of the difference: -9.3 to +12.7%). No differences in outcomes were attributable to differences in penicillin susceptibility of pneumococcal strains. Sequential i.v./oral amoxicillin-clavulanate and parenteral ceftriaxone were equally safe and effective for the empirical treatment of acute bacterial pneumonia, including penicillin and cephalosporin-resistant pneumococcal pneumonia. The use of appropriate betalactams in patients with penumococcal pneumonia and in the overall CAP population, is reliable at the current level of resistance.

Pneumococcal peritonitis in adult patients: report of 64 cases with special reference to emergence of antibiotic resistance

BACKGROUND

Few data are available regarding pneumococcal peritonitis. We studied the clinical characteristics of intra-abdominal infections caused by Streptococcus pneumoniae and its prognosis in relation to antibiotic resistance.

METHODS

We reviewed all cases of culture-proved pneumococcal peritonitis. Patients with liver cirrhosis and primary pneumococcal peritonitis were compared with patients with Escherichia coli peritonitis.

RESULTS

Between January 1, 1979, and December 31, 1998, we identified 45 cases of primary pneumococcal peritonitis in patients with cirrhosis and 19 cases of secondary (or tertiary) pneumococcal peritonitis. Patients with cirrhosis and primary pneumococcal peritonitis vs those with primary E coli peritonitis had more frequent community-acquired infection, 73% vs 47%; pneumonia, 36% vs 2%; and bacteremia, 76% vs 33%; and higher attributable mortality (early mortality), 27% vs 9% (P<.05 for all). Secondary (or tertiary) pneumococcal peritonitis was associated with upper or lower gastrointestinal tract diseases; in most cases, the infection appeared after surgery. A hematogenous spread of S pneumoniae from a respiratory tract infection might be the most important origin of peritonitis; also, S pneumoniae might directly reach the gastrointestinal tract favored by endoscopic procedures or hypochlorhydria. There was an increased prevalence of penicillin and cephalosporin resistance up to 30.7% and 17.0%, respectively, although it was not associated with increased mortality rates.

CONCLUSIONS

Primary pneumococcal peritonitis in patients with cirrhosis more often spread hematogenously from the respiratory tract and was associated with early mortality. In secondary (and tertiary) pneumococcal peritonitis, a transient gastrointestinal tract colonization and inoculation during surgery might be the most important mechanisms. Current levels of resistance were not associated with increased mortality rates.

In vitro activity of linezolid and 11 other antimicrobials against 566 clinical isolates and comparison between NCCLS microdilution and Etest methods

The in vitro activity of linezolid and 11 other antimicrobials was determined for 566 clinical isolates of Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus spp., Streptococcus pyogenes, Streptococcus agalactiae, Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis, some of them resistant to several antibiotics, using a broth microdilution method and the Etest method. All Gram-positive organisms tested were inhibited by a concentration of <or=4 mg/L of linezolid, including methicillin-resistant staphylococci, vancomycin- and ampicillin-resistant enterococci, and penicillin-intermediate and -resistant pneumococci. MICs of linezolid by the Etest method were usually one to two dilution values lower than those obtained by microdilution.

[Labelling of ceftizoxime with 99mTc]

AIM OF THE STUDY

A new method to label antibiotics with 99mTc, using a third generation, wide spectrum cephalosporine (ceftizoxime), is presented.

MATERIAL AND METHODS

2.5 mg of ceftizoxime, 6.25 mg sodium dithionite in sodium bicarbonate buffer (pH=11.4) as a reductor agent, and 300 MBq of 99mTc were used. The final pH was adjusted to 8.4 with NaOH 0.1N. Radiochemical purity was assessed using ITLC-SG/MEK, ITLC-SG/0.9% NaCl and reverse phase HPLC. Biologic activity was assessed with the agar diffusion technique soaked with E. Coli in disks containing 10.5 microg labelled and non-labelled antibiotic. The maintenance of antibiotic activity was assessed by the diameter of the inhibition halos measured after 24 hours of incubation at 37 degrees C.

RESULTS

The labelling efficiency was 94.9 +/- 2.4% (n = 20) and the complex was stable up to 6 h post-labelling. The HPLC chromatography showed five peaks: two of them at 1.7-2.0 min, which corresponds to the ceftizoxime derived product (82%-83% of the absorbance and about 90% of the radioactivity) and a third one at 4.7 min which corresponds to the intact ceftizoxime (6% of absorbance). The remaining two peaks appeared at 3.8 and 6.7 min and represented about 7%-8% of the absorbance. The antibiotic activity of the ceftizoxime-derived compound (CDC) was 83% of the unlabelled one.

CONCLUSIONS

1) The labelling method of ceftizoxime described causes a modification in its structure. 2) The 99mTc binds to the newly formed compound with high labelling efficiency and an acceptable shelf life stability. 3) The 99mTc-CDC maintains 83% of the original antibiotic activity and could be used for the detection of in vivo infection.

Evaluation of combined ceftriaxone and dexamethasone therapy in experimental cephalosporin-resistant pneumococcal meningitis

The treatment of meningitis caused by strains of Streptococcus pneumoniae with decreased susceptibility to third-generation cephalosporins is an increasingly frequent and difficult problem. In this study a rabbit model of meningitis was used to determine the efficacy of ceftriaxone at different dosages, and to establish the effect of the addition of dexamethasone to the chemotherapeutic regimen. Groups of eight rabbits were inoculated with 10(6) cfu/mL of a cephalosporin- resistant strain of S. pneumoniae (MIC of cefotaxime/ceftriaxone 2 mg/L). Eighteen hours after inoculation, ceftriaxone (50 or 100 mg/kg/day) with or without dexamethasone (0. 25 mg/kg/ day) was administered for a period of 48 h. The ceftriaxone dose of 50 mg/kg/day was not fully effective in this model (therapeutic failure rate 28%). With a dose of 100 mg/kg/day there were no therapeutic failures and all CSF cultures were below the level of detection at 48 h. CSF ceftriaxone concentrations, area under the time-concentration curve and time above the MIC were not significantly different with or without dexamethasone. However, concomitant use of dexamethasone resulted in higher CSF bacterial counts and a higher number of therapeutic failures (57% with the 50 mg/kg/day dose and 28% with the 100 mg/kg/day dose). Increasing doses of ceftriaxone might be an effective mode of therapy for meningitis caused by S. pneumoniae with MIC </= 2 mg/L. However, in contrast to cephalosporin-sensitive cases, in cases caused by ceftriaxone-resistant strains, concomitant use of dexamethasone was associated with a higher failure rate even when a higher dosage of ceftriaxone was used.

Efficacy of sulbactam alone and in combination with ampicillin in nosocomial infections caused by multiresistant Acinetobacter baumannii

From March 1995 to March 1997, sulbactam was prospectively evaluated in patients with non-life-threatening multiresistant Acinetobacter baumannii infections. During this period, 47 patients were treated with sulbactam; of them, five were excluded because they had received < or =48 h of sulbactam therapy. A total of 42 patients, 27 males and 15 females with a mean age of 60+/-15 years, were finally evaluated. Infections were as follows: surgical wound, 19; tracheobronchitis, 12; urinary tract, 7; catheter-related bacteraemia, 2; and pneumonia, 2. Eighteen patients received intravenous sulbactam alone (1 g every 8 h) and 24 patients received intravenous sulbactam/ampicillin (1 g:2 g every 8 h) with no major adverse effects. Of the 42 patients, 39 improved or were cured and showed A. baumannii eradication and one patient had persistence of wound infection after 8 days of sulbactam/ampicillin requiring surgical debridement. Two patients died after 3 days of therapy (one of the deaths was attributable to A. baumannii infection). The in-vitro activity of the sulbactam/ampicillin combination was by virtue of the antimicrobial activity exhibited by sulbactam. Killing curves showed that sulbactam was bacteriostatic; no synergy was observed between ampicillin and sulbactam. Our results indicate that sulbactam may prove effective for non-life-threatening A. baumannii infections. Its role in the treatment of severe infections is unknown. However, the current formulation of sulbactam alone may allow its use at higher doses and provide new potential synergic combinations, particularly for those infections by A. baumannii resistant to imipenem.

Current usefulness of procaine penicillin in the treatment of pneumococcal pneumonia

The aim of this study was to determine whether procaine penicillin could be used in the treatment of suspected pneumococcal pneumonia of mild to moderate severity in an area with a high prevalence of penicillin resistance. Forty-nine patients were treated with 1.2 x 10(6) U of i.m. procaine penicillin every 12 h. By intent-to-treat analysis, 40 of 49 patients were cured and no patient died. Streptococcus pneumoniae could be demonstrated in 17 patients; 5 of 17 isolates were resistant to penicillin (MICs 0.25-4 microg/ml). Fifteen of 17 patients were cured with procaine penicillin, one presented allergy, and one was a therapeutic failure. Mean penicillin serum levels were 2.39 +/- 1.16 microg/ml (peak) and 0.61 +/- 0.38 microg/ml (trough). The results suggest that procaine penicillin may still be useful in the empirical therapy of suspected pneumococcal pneumonia.

[Endocarditis caused by group B streptococci in adults]

OBJECTIVE

To evaluate clinical characteristics, treatment and outcome of group B streptococcal endocarditis in nonpregnant adults.

METHODS

We included all cases of Streptococcus agalactiae endocarditis diagnosed according to the Duke criteria between 1980 and 1994 in a 1000-bed university hospital, where a prospective surveillance of all cases of bacteremia is regularly performed.

RESULTS

There were 9 episodes of S. agalactiae endocarditis, that account for the 10.5% of 85 bacteremia caused by this organism and 2.6% of 336 infectious endocarditis (in non-drug abusers) during the study period. They occurred in 6 males and 3 females with an average age of 60 years (44-86 years). Three patients had underlying disease and three had been previously diagnosed of having valvulopathy. There were no cases of prosthetic valve endocarditis. The valves most frequently involved were the aortic and mitral valves. Only one patient had large vessel embolization. All isolates were penicillin-susceptible (MIC < 0.12 microgram/ml). Most of the patients were treated with penicillin plus an aminoglycoside and 6 patients also underwent surgery combined with the medical therapy after an average of 40 days (13-60 days). The overall mortality was 11%.

CONCLUSIONS

S. agalactiae is a rare cause of infectious endocarditis. Combination of surgery with the antibiotic therapy might decrease mortality rates of this infection.

[In vitro bactericide activity of different antibiotic combinations to Streptococcus pneumoniae resistant to penicillin and cefotaxime]

BACKGROUND

To determinate the bactericidal activity of vancomycin, rifampicin, cefotaxime, ceftriaxone and their double and triple combinations against penicillin and third generation cephalosporin-resistant. Streptococcus pneumoniae strain.

METHODS

A study of the bactericidal activity of antibiotics alone and in combination was performed by killing-curves with fixed concentration of 2 micrograms/ml, equivalent to 1 < MIC for cefotaxime and ceftriaxone, to 8 x MIC for vancomycin and to 32 < MIC for rifampin.

RESULTS

Vancomycin was the only antibiotic with bactericidal effect at 6 hours. Cefotaxime had bactericidal effect at 12 hours. Rifampin had no bactericidal effect. The association of vancomycin plus third generation cephalosporins (cefotaxime and ceftriaxone) showed indifferent effect. Rifampin decreased the bactericidal activity of vancomycin at 12 hours, when both were studied in combination, and it demonstrated antagonistic effect in the double and triple combination in which rifampicin was included.

CONCLUSIONS

All associations of vancomycin plus third generation cephalosporins were bactericidal effects, but they did no show synergistic effects against penicillin- and third generation cephalosporin S. pneumoniae strain 2349. All combinations with rifampin showed decreased bactericidal activity or antagonistic effects. However, these results may be interpreted with caution because the in vivo experience of an experimental meningitis model in rabbits showed that the associations of vancomycin plus rifampin and vancomycin plus cefotaxime and rifampin were effective combinations. More in vivo and in vitro comparative studies are needed to demonstrate the reliability of in vitro results.