Estimated glomerular filtration rate as a tool for early identification of patients with insufficient exposure to beta-lactam antibiotics in intensive care units

BACKGROUND

Only about 50% of intensive care unit (ICU) patients reach a free trough concentration above MIC (100% fT > MIC) of beta-lactam antibiotics. Although dose adjustments based on therapeutic drug monitoring (TDM) could be beneficial, TDM is not widely available. We investigated serum creatinine-based estimated GFR (eGFR) as a rapid screening tool to identify ICU patients at risk of insufficient exposure.

METHOD

Ninety-three adult patients admitted to four ICUs in southeast Sweden treated with piperacillin/tazobactam, meropenem, or cefotaxime were included. Beta-lactam trough concentrations were measured. The concentration target was set to 100% fT > MICECOFF (2, 4, and 16 mg/L based on calculated free levels for meropenem, cefotaxime, and piperacillin, respectively). eGFR was primarily determined via Chronic Kidney Disease-Epidemiology Collaboration (CKD-EPI) and compared to three other eGFR equations. Data was analysed using logistic regression and receiver operative characteristic (ROC) curves.

RESULTS

With intermittent standard dosing, insufficient exposure was common in patients with a relative eGFR ≥48mL/min/1.73m2 [85%, (45/53)], particularly when treated with cefotaxime [96%, (24/25)]. This eGFR cut-off had a sensitivity of 92% and specificity of 82% (AUC 0.871, p < 0.001) in identifying insufficient exposure. In contrast, patients with eGFR <48mL/min/1.73m2 had high target attainment [90%, (36/40)] with a wide variability in drug exposure. There was no difference between the four eGFR equations (AUC 0.866-0.872, cut-offs 44-51 ml/min/1.73m2).

CONCLUSION

Serum creatinine-based eGFR is a simple and widely available surrogate marker with potential for early identification of ICU patients at risk of insufficient exposure to piperacillin, meropenem, and cefotaxime.

Influenza-associated invasive aspergillosis in patients admitted to the intensive care unit in Sweden: a prospective multicentre cohort study

BACKGROUND

The purpose of this study was to prospectively investigate the incidence of influenza-associated pulmonary aspergillosis (IAPA) in influenza patients admitted to intensive care units in Sweden.

METHODS

The study included consecutive adult patients with PCR-verified influenza A or B in 12 Swedish intensive care units (ICUs) over four influenza seasons (2019-2023). Patients were screened using serum galactomannan and β-d-glucan tests and fungal culture of a respiratory sample at inclusion and weekly during the ICU stay. Bronchoalveolar lavage was performed if clinically feasible. IAPA was classified according to recently proposed case definitions.

RESULTS

The cohort included 55 patients; 42% were female, and the median age was 59 (IQR 48-71) years. All patients had at least one galactomannan test, β-d-glucan test and respiratory culture performed. Bronchoalveolar lavage was performed in 24 (44%) of the patients. Five (9%, 95% CI 3.8% - 20.4%) patients were classified as probable IAPA, of which four lacked classical risk factors. The overall ICU mortality was significantly higher among IAPA patients than non-IAPA patients (60% vs 8%, p = 0.01).

CONCLUSIONS

The study represents the first prospective investigation of IAPA incidence. The 9% incidence of IAPA confirms the increased risk of invasive pulmonary aspergillosis among influenza patients admitted to the ICU. Therefore, it appears reasonable to implement a screening protocol for the early diagnosis and treatment of IAPA in influenza patients receiving intensive care.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04172610, registered November 21, 2019.

Fluoroquinolone-resistant Escherichia coli among the rectal flora is the predominant risk factor for severe infection after transrectal ultrasound-guided prostate biopsy: a prospective observational study

BACKGROUND

Infection of the prostate gland following biopsy, usually with Escherichia coli, is a common complication, despite the use of antimicrobial prophylaxis. A fluoroquinolone (FQ) is commonly prescribed as prophylaxis. Worryingly, the rate of fluoroquinolone-resistant (FQ-R) E. coli species has been shown to be increasing.

OBJECTIVE

This study aimed to identify risk factors associated with infection after transrectal ultrasound-guided prostate biopsy (TRUS-Bx).

METHODS

This was a prospective study on patients undergoing TRUS-Bx in southeast Sweden. Prebiopsy rectal and urine cultures were obtained, and antimicrobial susceptibility and risk-group stratification were determined. Multivariate analyses were performed to identify independent risk factors for post-biopsy urinary tract infection (UTI) and FQ-R E. coli in the rectal flora.

RESULTS

In all, 283 patients were included, of whom 18 (6.4%) developed post-TRUS-Bx UTIs. Of these, 10 (3.5%) had an UTI without systemic inflammatory response syndrome (SIRS) and 8 (2.8%) had a UTI with SIRS. Being in the medium- or high-risk groups of infectious complications was not an independent risk factor for UTI with SIRS after TRUS-Bx, but low-level FQ-resistance (minimum inhibitory concentration (MIC): 0.125-0.25 mg/L) or FQ-resistance (MIC > 0.5 mg/L) among E. coli in the faecal flora was. Risk for SIRS increased in parallel with increasing degrees of FQ-resistance. Significant risk factor for harbouring FQ-R E.coli was travelling outside Europe within the previous 12 months.

CONCLUSION

The predominant risk factor for UTI with SIRS after TRUS-Bx was FQ-R E. coli among the faecal flora. The difficulty in identifying this type of risk factor demonstrates a need for studies on the development of a general approach either with rectal swab culture for targeted prophylaxis, or prior rectal preparation with a bactericidal agent such as povidone-iodine before TRUS-Bx to reduce the risk of FQ-R E. coli-related infection.

Treatment With Reduced-Dose Trimethoprim-Sulfamethoxazole Is Effective in Mild to Moderate Pneumocystis jirovecii Pneumonia in Patients With Hematologic Malignancies

BACKGROUND

Recent studies have reported that reduced-dose trimethoprim-sulfamethoxazole (TMP-SMX) may be effective in the treatment of Pneumocystis jirovecii pneumonia (PJP), but data are lacking for patients with hematologic malignancies.

METHODS

This retrospective study included all adult hematologic patients with PJP between 2013 and 2017 at 6 Swedish university hospitals. Treatment with 7.5-15 mg TMP/kg/day (reduced dose) was compared with >15-20 mg TMP/kg/day (standard dose), after correction for renal function. The primary outcome was the change in respiratory function (Δpartial pressure of oxygen [PaO2]/fraction of inspired oxygen [FiO2]) between baseline and day 8. Secondary outcomes were clinical failure and/or death at day 8 and death at day 30.

RESULTS

Of a total of 113 included patients, 80 patients received reduced dose and 33 patients received standard dose. The overall 30-day mortality in the whole cohort was 14%. There were no clinically relevant differences in ΔPaO2/FiO2 at day 8 between the treatment groups, either before or after controlling for potential confounders in an adjusted regression model (-13.6 mm Hg [95% confidence interval {CI}, -56.7 to 29.5 mm Hg] and -9.4 mm Hg [95% CI, -50.5 to 31.7 mm Hg], respectively). Clinical failure and/or death at day 8 and 30-day mortality did not differ significantly between the groups (18% vs 21% and 14% vs 15%, respectively). Among patients with mild to moderate pneumonia, defined as PaO2/FiO2 >200 mm Hg, all 44 patients receiving the reduced dose were alive at day 30.

CONCLUSIONS

In this cohort of 113 patients with hematologic malignancies, reduced-dose TMP-SMX was effective and safe for treating mild to moderate PJP.

Simultaneous Measurement of 11 Antibiotics for Use in the Intensive Care Unit by Ultra-High Performance Liquid Chromatography-Tandem Mass Spectrometry

BACKGROUND

Recent studies indicate that a high proportion of patients in the intensive care unit fail to attain adequate antibiotic levels. Thus, there is a need to monitor the antibiotic concentration to ensure effective treatment. In this article, the authors aimed to develop an ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method for the simultaneous quantification of antimicrobials to assess individualized therapeutic drug monitoring.

METHODS

A UHPLC-MS/MS method with 11 antibiotics (ciprofloxacin, moxifloxacin, benzylpenicillin, levofloxacin, linezolid, rifampicin, meropenem, cloxacillin, cefotaxime, clindamycin, and piperacillin) was developed. Chromatographic separation was performed using a Kinetex Biphenyl reversed-phase column, with gradient elution using 0.1% formic acid and methanol with 0.1% formic acid. Sample preparation was performed using methanol protein precipitation. The total run time was 5 minutes.

RESULTS

For all analytes, the interassay inaccuracies for calibrators were ≤5%. The interday inaccuracies for the quality controls (QCs) were ≤5% for all analytes. The interassay precision for calibration standards ranged between 1.42% and 6.11%. The interassay imprecision for QCs of all antibiotics and concentrations ranged between 3.60% and 16.1%. Interassay inaccuracy and imprecision for the QCs and calibration standards were ≤15% for all drugs, except benzylpenicillin.

CONCLUSIONS

A rapid UHPLC-MS/MS method was developed for the simultaneous quantification of 11 different antibiotics. Minimal sample preparation was required to ensure a rapid turnaround time. The method was applied to clinical samples collected from 4 intensive care units.

Low incidence of antibiotic-resistant bacteria in south-east Sweden: An epidemiologic study on 9268 cases of bloodstream infection

Objectives

The aim of this study was to investigate the epidemiology of bloodstream infections (BSI) in a Swedish setting, with focus on risk factors for BSI-associated mortality.

Methods

A 9-year (2008–2016) retrospective cohort study from electronic records of episodes of bacteremia amongst hospitalized patients in the county of Östergötland, Sweden was conducted. Data on episodes of BSI including microorganisms, antibiotic susceptibility, gender, age, hospital admissions, comorbidity, mortality and aggregated antimicrobial consumption (DDD /1,000 inhabitants/day) were collected and analyzed. Multidrug resistance (MDR) was defined as resistance to at least three groups of antibiotics. MDR bacteria and MRSA, ESBL-producing Enterobacteriaceae, vancomycin-resistant enterococci not fulfilling the MDR criteria were all defined as antimicrobial-resistant (AMR) bacteria and included in the statistical analysis of risk factors for mortality

Results

In all, 9,268 cases of BSI were found. The overall 30-day all-cause mortality in the group of patients with BSI was 13%. The incidence of BSI and associated 30-day all-cause mortality per 100,000 hospital admissions increased by 66% and 17% respectively during the nine-year study period. The most common species were Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, Streptococcus pneumoniae and Enterococcus faecalis. Independent risk factors for 30-day mortality were age (RR: 1.02 (CI: 1.02–1.03)) and 1, 2 or ≥3 comorbidities RR: 2.06 (CI: 1.68–2.52), 2.79 (CI: 2.27–3.42) and 2.82 (CI: 2.31–3.45) respectively. Almost 3% (n = 245) of all BSIs were caused by AMR bacteria increasing from 12 to 47 per 100,000 hospital admissions 2008–2016 (p = 0.01), but this was not associated with a corresponding increase in mortality risk (RR: 0.89 (CI: 0.81–0.97)).

Conclusion

Comorbidity was the predominant risk factor for 30-day all-cause mortality associated with BSI in this study. The burden of AMR was low and not associated with increased mortality. Patients with BSIs caused by AMR bacteria (MDR, MRSA, ESBL and VRE) were younger, had fewer comorbidities, and the 30-day all-cause mortality was lower in this group.

Phenotypic screening for quinolone resistance in Escherichia coli

Recent studies show that rectal colonization with low-level ciprofloxacin-resistant Escherichia coli (ciprofloxacin minimal inhibitory concentration (MIC) above the epidemiological cutoff point, but below the clinical breakpoint for resistance), i.e., in the range > 0.06-0.5 mg/L is an independent risk factor for febrile urinary tract infection after transrectal ultrasound-guided biopsy (TRUS-B) of the prostate, adding to the other risk posed by established ciprofloxacin resistance in E. coli (MIC > 0.5 mg/L) as currently defined. We aimed to identify the quinolone that by disk diffusion best discriminates phenotypic wild-type isolates (ciprofloxacin MIC ≤ 0.06 mg/L) of E. coli from isolates with acquired resistance, and to determine the resistance genotype of each isolate. The susceptibility of 108 E. coli isolates was evaluated by ciprofloxacin, levofloxacin, moxifloxacin, nalidixic acid, and pefloxacin disk diffusion and correlated to ciprofloxacin MIC (broth microdilution) using EUCAST methodology. Genotypic resistance was identified by PCR and DNA sequencing. The specificity was 100% for all quinolone disks. Sensitivity varied substantially, as follows: ciprofloxacin 59%, levofloxacin 46%, moxifloxacin 59%, nalidixic acid 97%, and pefloxacin 97%. We suggest that in situations where low-level quinolone resistance might be of importance, such as when screening for quinolone resistance in fecal samples pre-TRUS-B, a pefloxacin (S ≥ 24 mm) or nalidixic acid (S ≥ 19 mm) disk, or a combination of the two, should be used. In a setting where plasmid-mediated resistance is prevalent, pefloxacin might perform better than nalidixic acid.

Long-term persistence of a multi-resistant methicillin-susceptible Staphylococcus aureus (MR-MSSA) clone at a university hospital in southeast Sweden, without further transmission within the region

The objective of this study was to characterise isolates of methicillin-susceptible Staphylococcus aureus (MSSA) with resistance to clindamycin and/or tobramycin in southeast Sweden, including the previously described ECT-R clone (t002) found in Östergötland County, focusing on clonal relatedness, virulence determinants and existence of staphylococcal cassette chromosome (SCC) mec remnants. MSSA isolates with resistance to clindamycin and/or tobramycin were collected from the three county councils in southeast Sweden and investigated with spa typing, polymerase chain reaction (PCR) targeting the SCCmec right extremity junction (MREJ) and DNA microarray technology. The 98 isolates were divided into 40 spa types, and by microarray clustered in 17 multi-locus sequence typing (MLST) clonal complexes (MLST-CCs). All isolates with combined resistance to clindamycin and tobramycin (n = 12) from Östergötland County and two additional isolates (clindamycin-R) were designated as spa type t002, MREJ type ii and were clustered in CC5, together with a representative isolate of the ECT-R clone, indicating the clone's persistence. These isolates also carried several genes encoding exotoxins, Q9XB68-dcs and qacC. Of the isolates in CC15, 83% (25/30) were tobramycin-resistant and were designated spa type t084. Of these, 68% (17/25) were isolated from new-borns in all three counties. The persistence of the ECT-R clone in Östergötland County, although not found in any other county in the region, carrying certain virulence factors that possibly enhance its survival in the hospital environment, highlights the fact that basic hygiene guidelines must be maintained even when MRSA prevalence is low.

Travel-associated faecal colonization with ESBL-producing Enterobacteriaceae: incidence and risk factors

OBJECTIVES

To study the acquisition of extended-spectrum β-lactamase-producing Enterobacteriaceae (ESBL-PE) among the faecal flora during travel, with a focus on risk factors, antibiotic susceptibility and ESBL-encoding genes.

METHODS

An observational prospective multicentre cohort study of individuals attending vaccination clinics in south-east Sweden was performed, in which the submission of faecal samples and questionnaires before and after travelling outside Scandinavia was requested. Faecal samples were screened for ESBL-PE by culturing on ChromID ESBL and an in-house method. ESBL-PE was confirmed by phenotypic and genotypic methods. Susceptibility testing was performed with the Etest. Individuals who acquired ESBL-PE during travel (travel-associated carriers) were compared with non-carriers regarding risk factors, and unadjusted and adjusted ORs after manual stepwise elimination were calculated using logistic regression.

RESULTS

Of 262 enrolled individuals, 2.4% were colonized before travel. Among 226 evaluable participants, ESBL-PE was detected in the post-travel samples from 68 (30%) travellers. The most important risk factor in the final model was the geographic area visited: Indian subcontinent (OR 24.8, P < 0.001), Asia (OR 8.63, P < 0.001) and Africa north of the equator (OR 4.94, P = 0.002). Age and gastrointestinal symptoms also affected the risk significantly. Multiresistance was seen in 77 (66%) of the ESBL-PE isolates, predominantly a combination of reduced susceptibility to third-generation cephalosporins, trimethoprim/sulfamethoxazole and aminoglycosides. The most common species and ESBL-encoding gene were Escherichia coli (90%) and CTX-M (73%), respectively.

CONCLUSION

Acquisition of multiresistant ESBL-PE among the faecal flora during international travel is common. The geographical area visited has the highest impact on ESBL-PE acquisition.

Detection and characterisation of SCCmec remnants in multiresistant methicillin-susceptible Staphylococcus aureus causing a clonal outbreak in a Swedish county

The purpose of this study was to investigate if multiresistant methicillin-susceptible Staphylococcus aureus (MR-MSSA) causing a clonal outbreak in Östergötland County, Sweden, were derived from methicillin-resistant S. aureus (MRSA) by carrying remnants of SCCmec, and, if so, to characterise this element. A total of 54 MSSA isolates with concomitant resistance to erythromycin, clindamycin and tobramycin from 49 patients (91% clonally related, spa type t002) were investigated with the BD GeneOhm MRSA assay and real-time polymerase chain reaction (PCR) targeting the SCCmec integration site/SCCmec right extremity junction. DNA sequencing of one isolate representing the MR-MSSA outbreak clone was performed by massive parallel 454 pyrosequencing. All isolates that were part of the clonal outbreak carried SCCmec remnants. The DNA sequencing revealed the carriage of a pseudo-SCC element 12 kb in size, with a genomic organisation identical to an SCCmec type ΙΙ element, except for a 41-kb gap. This study demonstrates the presence of a pseudo-SCC element resembling SCCmec type II among MR-MSSA, suggesting possible derivation from MRSA. The presence of SCCmec remnants should always be considered when SCCmec typing is used for MRSA detection, and may not be suitable in locations with a high prevalence of MR-MSSA, since this might give a high number of false-positive results.

Genetic Relatedness of Enterococcus Faecalis Isolates with High-level Gentamicin Resistance from Patients with Bacteraemia in the South East of Sweden 1994–2001

High-level gentamicin resistant (HLGR) enterococci (Enterococcus faecalis and Enterococcus faecium) have become a substantial nosocomial problem in many countries. In this study, we investigated the prevalence of HLGR enterococci and their genetic relatedness in blood culture isolates from patients with bacteraemia admitted to the 3 hospitals in Ostergötland, a county in the south east of Sweden, during 1994-2001. 36 of 250 E. faecalis (14%,) and 4 of 106 E. faecium isolates (4%) were shown by PCR to carry the aac(6')-Ie-aph(2")-Ia aminoglycoside modifying gene and these isolates were also classified as HLGR enterococci by the gentamicin antibiotic disk diffusion method. A majority of HLGR E. faecalis isolates (83%) belonged to the same cluster of genetically related isolates, according to the pulsed-field gel electrophoresis (PFGE) patterns, whereas all 4 HLGR E. faecium isolates had unique PFGE patterns. In conclusion, our study showed that in contrast to studies from many other countries, the presence of HLGR enterococci was more common in E. faecalis than in E. faecium and appeared the first time in 1996 and 1999, respectively. Bacteraemia with HLGR enterococci in Ostergötland was mainly due to the spread of a cluster of related E. faecalis strains.

Susceptibility of staphylococci and enterococci to antimicrobial agents at different ward levels in four north European countries

A multicentre susceptibility study was performed on staphylococci and enterococci isolated from patients at 3 different ward levels: primary care centres (PCCs), general hospital wards (GHWs) and intensive care units (ICUs), in Denmark, Finland, Norway and Sweden. There was a markedly higher incidence of resistance among CoNS in ICUs compared to GHWs and PCCs. Resistance rates were low among S. aureus isolates and no differences were found between the ward levels. Oxacillin resistance was found among 1.6% of S. aureus and 47% of CoNS isolates. 14% of CoNS and 0.9% of S. aureus isolates were glycopeptide intermediate. The prevalence of E. faecium isolates in this study differed significantly between the ward levels with the lowest prevalence found at PCCs. High level gentamicin resistant (HLGR) enterococci occurred in 11-25% of E. faecium and 6-20% of E. faecalis isolates. The HLGR rate was significantly higher among E. faecalis from hospitalized patients (GHWs and ICUs) compared to patients at PCCs. For enterococcal isolates, no other significant differences in antimicrobial resistance were found between the ward levels. All enterococci were teicoplanin susceptible, but decreased susceptibility to vancomycin was found among 2.0% and 0.6% of the E. faecium and E. faecalis isolates, respectively.

Molecular detection of aggregation substance, enterococcal surface protein, and cytolysin genes and in vitro adhesion to urinary catheters of Enterococcus faecalis and E. faecium of clinical origin

It has been hypothesized that nosocomial enterococci might have virulence factors that enhance their ability to colonise hospitalised patients. The objectives of this study were to investigate the prevalence of genes encoding 3 virulence factors: aggregation substance (asa1), enterococcal surface protein (esp), and 5 genes within the cytolysin operon (cylA, cylB, cylM, cylL(L), cylL(S)) and cytolysin production in 115 enterococcal clinical isolates (21 Enterococcus faecium and 94 E. faecalis). Adhesion to siliconized latex urinary catheters in relation to presence of esp was analysed in a subset of isolates. The isolates were previously characterised by pulsed-field gel electrophoresis (PFGE). esp was the only virulence gene found in E. faecium. It was found in 71% of the 21 E. faecium isolates. asa1, esp, and the cyl operon were found in 79%, 73% and 13% respectively, of the 94 E. faecalis isolates. There was a complete agreement between presence of the cyl operon and phenotypic cytolysin production. Isolates belonging to a cluster of genetically related isolates carried esp and asa1 more often when compared to unique isolates. No difference was found with respect to cyl genes. E. faecalis isolates adhered with higher bacterial densities than E. faecium. E. faecalis isolates within the same PFGE cluster adhered with similar bacterial densities, but there was no association between adhesion and the presence of esp when isolates within the same cluster were compared. In conclusion, E. faecalis isolates with high-level gentamicin resistance (HLGR) belonging to clusters of genetically related isolates widely distributed in Swedish hospitals, were likely to carry both esp and asa1. Adhesion was not affected by esp.

Phene Plate (PhP) biochemical fingerprinting. A screening method for epidemiological typing of enterococcal isolates

Pulsed-field gel electrophoresis (PFGE) is currently considered the gold standard for genotyping of enterococci. However, PFGE is both expensive and time-consuming. The purpose of this study was to investigate whether the PhP system can be used as a reliable clinical screening method for detection of genetically related isolates of enterococci. If so, it should be possible to minimize the number of isolates subjected to PFGE typing, which would save time and money. Ninety-nine clinical enterococcal isolates were analysed by PhP (similarity levels 0.90-0.975) and PFGE (similarity levels < or =3 and < or =6 bands) and all possible pairs of isolates were cross-classified as matched or mismatched. We found that the probability that a pair of isolates (A and B) belonging to the same type according to PhP also belong to the same cluster according to PFGE, i.e. p(A(PFGE)=B(PFGE) * A(PhP)=B(PhP)), and the probability that a pair of isolates of different types according to PhP also belong to different clusters according to PFGE, i.e. p(A(PFGE) not equalB(PFGE) * A(PhP) not equalB(PhP)), was relatively high for E. faecalis (0.86 and 0.96, respectively), but was lower for E. faecium (0.51 and 0.77, respectively). The concordance which shows the probability that PhP and PFGE agree on match or mismatch was 86%-93% for E. faecalis and 54%-66% for E. faecium, which indicates that the PhP method may be useful for epidemiological typing of E. faecalis in the current settings but not for E. faecium.

Rapid decrease of free vancomycin in dense staphylococcal cultures

Bacterial numbers in broth cultures were determined by bioluminescence assay of intracellular bacterial ATP. Broth MICs for strains of Staphylococcus epidermidis (ATCC 14990 and 35984) and Staphylococcus aureus (ATCC 25923, 29213 and 6538) were determined for cultures with different inocula (10(5)-10(8) bacteria/ml) after 24 h of incubation in supplemented Mueller-Hinton broth containing vancomycin. All of the tested strains except one were susceptible to methicillin, and all of the strains were susceptible to vancomycin. Free vancomycin concentrations in the broth cultures of all strains were determined with an agar well bioassay after 24 h of incubation. Free vancomycin concentrations and bacterial numbers of ATCC 35984 and ATCC 29213 were also determined after 0.5, 2, 4, and 8 h. In a low inoculum (10(5) bacteria/ml), the broth MICs were 1-4 microg/ml. In a high inoculum (approximately 10(8) bacteria/ml), the broth MICs increased two- to fourfold to 4-8 microg/ml. In dense inocula ( approximately 10(9)-10(10) bacteria/ml), the concentrations of free vancomycin in the broth were reduced, in most cases below the detection limit of the bioassay (</=0.5 microg/ml). This reduction of free vancomycin was fast, occurring in initially dense inocula in less than 30 min. No emergence of resistance was seen. These results show a rapid reduction of free vancomycin in the broth and a simultaneous increase in broth MICs in high inocula, without development of resistance. This indicates that the dosing regimen of vancomycin is of particular importance in staphylococcal infections with dense inocula, e.g. infective endocarditis.

Rectal colonization and frequency of enterococcal cross-transmission among prolonged-stay patients in two Swedish intensive care units

The aims of this study were to gain insight into the dynamics of the rectal flora during prolonged ICU stay, with a particular focus on colonization and cross-transmission with resistant pathogens, and to evaluate methods for the rapid isolation of relevant bacteria from rectal swabs. Patients admitted to a general intensive care unit (GICU) or a cardiothoracic ICU (TICU) at the University Hospital of Linköping, Sweden, between 1 November 2001 and January 2002 with a length of stay > 5 d were included (n = 20). Chromogenic UTI agar medium was used for discrimination of different species, and appropriate antibiotics were added to detect resistance. Direct plating was compared to enrichment broth for a subset of specimens. The study showed an early alteration in rectal flora, with a dramatic decrease in Gram-negative rods in favour of Gram-positive bacteria. An ampicillin- and high-level gentamicin resistant clone of Enterococcus faecium was found in 6 of 10 patients in the GICU and 2 of 11 patients in the TICU. Enrichment broth did not enhance the detection of Gram-negative bacteria compared to direct plating on Chromogenic UTI medium, but enrichment broths were needed for optimal detection of resistant Gram-positive bacteria.

Genetic relatedness among Enterococcus faecalis with transposon-mediated high-level gentamicin resistance in Swedish intensive care units

We studied 45 isolates of Enterococcus faecalis with high-level gentamicin resistance (HLGR), all but one concomitantly resistant to ciprofloxacin, and 25 ciprofloxacin-resistant isolates without HLGR for genetic relatedness using pulsed-field gel electrophoresis (PFGE). E. faecalis were isolated from patients admitted to intensive care units at eight hospitals in southern Sweden from December 1996 through December 1998. Genomic analysis by PFGE resulted in three clusters of genetically related isolates (designated clusters I, II and III) and 23 unique clones. Cluster I was found predominantly in the eastern and central parts of southern Sweden and clusters II and III in south-western Sweden. Among the 45 isolates with HLGR, 69% belonged to cluster I, 20% to cluster II, and 11% had unique PFGE patterns, which suggests that the majority of isolates with HLGR are closely related. Among the 25 ciprofloxacin-resistant isolates without HLGR, 68% had unique PFGE patterns, 12% belonged to cluster I and 20% to cluster III, which suggests the ciprofloxacin-resistant isolates are not related. All isolates with HLGR contained the aac(6')Ie-aph(2")Ia gene, which was carried on a Tn5281-like transposon in all isolates except one. We conclude that HLGR in E. faecalis was mainly due to dissemination of genetically related clones during the time studied, and that HLGR in these isolates was due to the presence of the aac(6')Ie-aph(2")Ia gene.

Modified pulsed-field gel electrophoresis protocol for typing of enterococci

Controlling the spread of vancomycin-resistant enterococci (VRE) is an important task in hospital epidemiology. Pulsed-field gel electrophoresis (PFGE) has become the golden standard for molecular epidemiological characterisation of enterococcal isolates. For separation of DNA fragments by PFGE, different electrophoresis conditions have been recommended, but none of these protocols allows a satisfactory separation of both small and large DNA fragments of enterococci simultaneously. In this study we have speeded up the preparation of chromosomal DNA and defined new electrophoresis conditions that enhance separation of small and large DNA fragments for subtyping of enterococci with a 24 h PFGE.

COX inhibition excites enteric nerves that affect motility, alkaline secretion, and permeability in rat duodenum

In anesthetized rats, the cyclooxygenase (COX) inhibitor indomethacin induces duodenal motility, increases duodenal mucosal alkaline secretion (DMAS), and evokes a transient increase in duodenal paracellular permeability (DPP). To examine whether enteric nerves influence these responses, the duodenum was perfused with lidocaine. Motility was assessed by measuring intraluminal pressure, and DPP was determined as blood-to-lumen clearance of (51)Cr-EDTA. DMAS was assessed by titration. In control animals, few contractions occurred during saline perfusion and lidocaine did not alter this condition. Perfusion with 0.03-0.1% lidocaine did not affect DMAS or DPP whereas 0.3-1% lidocaine reduced DMAS and increased DPP. Indomethacin induced motility and doubled DMAS. Application of 0.03% lidocaine on the duodenal serosa reduced motility and DMAS whereas 0.03% lidocaine applied luminally inhibited DMAS only. Higher concentrations of lidocaine abolished the increase in DMAS and changed the motility pattern to numerous low-amplitude contractions, the latter effect being blocked by iloprost. The lidocaine-induced increases in DPP were markedly higher than in controls. We conclude that indomethacin activates enteric nerves that induce motility, increase DMAS, and decrease DPP.

Antimicrobial susceptibility patterns of enterococci in intensive care units in Sweden evaluated by different MIC breakpoint systems

Three hundred and twenty-two (322) clinical isolates were collected from patients admitted to intensive care units (ICUs) at eight Swedish hospitals between December 1996 and December 1998. Of the isolates, 244 (76%) were Enterococcus faecalis, 74 (23%) were Enterococcus faecium and four (1%) were other Enterococcus spp. MICs of ampicillin, imipenem, meropenem, piperacillin/tazobactam, ciprofloxacin, trovafloxacin, clinafloxacin, gentamicin, streptomycin, vancomycin, teicoplanin, quinupristin/dalfopristin, linezolid and evernimicin were determined by Etest. Susceptible and resistant isolates were defined according to the species-related MIC breakpoints of the British Society for Antimicrobial Chemotherapy (BSAC), the National Committee for Clinical Laboratory Standards (NCCLS) and the Swedish Reference Group for Antibiotics (SRGA). Tentative breakpoints were applied for new/experimental antibiotics. Multidrug resistance among enterococci in ICUs is not uncommon in Sweden, particularly among E. faecium, and includes ampicillin resistance and concomitant resistance to fluoroquinolones. Almost 20% of E. faecalis isolates showed high-level resistance to gentamicin and concomitant resistance to fluoroquinolones. Vancomycin-resistant enterococci were only found sporadically. Among the new antimicrobial agents, linezolid and evernimicin showed the best activity against all enterococcal isolates. There was good concordance between the BSAC, NCCLS and SRGA breakpoints in detecting resistance. When applying the SRGA breakpoints for susceptibility, isolates were more frequently interpreted as intermediate. This might indicate earlier detection of emerging resistance using the SRGA breakpoint when the native population is considered susceptible, but with the risk that isolates belonging to the native susceptible population will be incorrectly interpreted as intermediate.

Adherent surface mucus gel restricts diffusion of macromolecules in rat duodenum in vivo

The aim of this study was to investigate the permeability of the adherent mucus gel layer in rat duodenum in vivo to macromolecules applied in the lumen. Rats were anesthetized with thiobarbiturate, and the duodenum was perfused with isotonic NaCl solution containing large-molecular-size secretagogues. Effects on mucosal HCO(-)(3) secretion and blood-to-lumen (51)chromium-labeled EDTA clearance were used as indexes that compounds had migrated across the mucus layer. Exposure to a low concentration of papain (10 U/100 ml) for 30 min removed the mucus layer without damage to the epithelium and induced or markedly enhanced HCO(-)(3) secretory responses to cholera toxin (molecular mass of 85 kDa) or glucagon (3.5 kDa). Water extracts from a VacA cytotoxin (89 kDa) producing Helicobacter pylori strain, but not from a toxin-negative isogenic mutant, caused a small increase in HCO(-)(3) secretion but only after the mucus layer had been removed by papain. The duodenal surface mucus gel thus significantly restricts migration of macromolecules to the duodenal surface. Release of bacterial toxins at the cell-mucus interface may enhance or be a prerequisite for their effects on the gastrointestinal mucosa.

Interaction between neurokinin A, VIP, prostanoids, and enteric nerves in regulation of duodenal function

Neurokinin A (NKA) induces duodenal motility and increases mucosal permeability and bicarbonate secretion in the in situ perfused duodenum in anesthetized rats. In the present study, the NKA-induced increase in mucosal permeability was potentiated by luminal perfusion with lidocaine and diminished by vasoactive intestinal peptide (VIP) but unaltered by elevated intraluminal pressure. Elevation of intraluminal pressure, however, potentiated the stimulatory effect of NKA on bicarbonate secretion. In contrast, the tachykinin decreased the rate of alkalinization in rats subjected to elevated intraluminal pressure and treated with indomethacin. Similarly, NKA partially inhibited the VIP-stimulated bicarbonate secretion. Luminal lidocaine did not affect the secretory response to NKA. The motility induced by NKA was unaffected by VIP or lidocaine but decreased by elevated intraluminal pressure. It is concluded that the NKA-induced increase in duodenal mucosal bicarbonate secretion is independent of neurons and possibly mediated by prostanoids. The increase in mucosal permeability in response to NKA may be suppressed by mucosal nerves, perhaps utilizing VIP as one of the transmitters.

Neurokinin A increases duodenal mucosal permeability, bicarbonate secretion, and fluid output in the rat

The aim of this study was to examine the integrative response to neurokinin A (NKA) on duodenal mucosal permeability, bicarbonate secretion, fluid flux, and motility in an in situ perfusion model in anesthetized rats. Intravenous infusion of NKA (100, 200, and 400 pmol.kg-1.min-1) induced duodenal motility. Furthermore, duodenal mucosal bicarbonate secretion, fluid output, and mucosal permeability increased in response to NKA. Pretreatment with the nicotinic antagonist hexamethonium did not change the response in any of the parameters investigated, whereas the NK2-receptor antagonist MEN 10,627 effectively inhibited all responses to NKA. Indomethacin induced duodenal motility and stimulated bicarbonate secretion. In indomethacin-treated rats, NKA further increased motility but decreased indomethacin-stimulated bicarbonate secretion by 70%. The NKA-induced increase in mucosal permeability was unaltered by indomethacin. It is concluded that NKA not only induces motility but also increases mucosal permeability and fluid output. Furthermore, the neuropeptide may have both stimulative and inhibitory effects on bicarbonate secretion. All responses to NKA are dependent on NK-2 receptor activation but are not mediated through nicotinic receptors.

Acid-induced increase in duodenal mucosal permeability is augmented by nitric oxide inhibition and vasopressin

The aim of the study was to determine if and by what mechanism(s) nitric oxide inhibition modulates the susceptibility of the duodenum to hydrochloric acid-induced disturbances of mucosal integrity. A second aim was to investigate whether basal permeability is a determinant of epithelial acid barrier function. Using an in situ duodenal perfusion model, mucosal permeability, alkaline secretion and morphology were investigated in anaesthetized rats. Luminal perfusion with 50 mM hydrochloric acid increased duodenal mucosal permeability in the control animals. In animals receiving the nitric oxide synthase inhibitor N-nitro-L-arginine methyl ester (L-NAME 3 mg kg(-1) and 1 mg kg(-1) h(-1)) and in those receiving vasopressin (1 IU kg(-1) h(-1)), however, the mean increase in permeability in response to acid was markedly higher. In rats treated with either hexamethonium (20 mg kg(-1)) or atropine (0.5 mg kg(-1)) L-NAME failed to augment the acid-induced increase in permeability. Perfusion with hypotonic saline (25 mM) increased basal permeability but did not influence the response to acid. Exposure of the duodenum to hydrochloric acid caused very subtle changes of duodenal morphology. It is concluded that both inhibition of endogenous nitric oxide synthesis and vasopressin treatment augment the acid-induced increase in mucosal permeability. The mechanisms involved may be related to changes of Starling forces in the microcirculatory bed. Endogenous nitric oxide may protect the duodenal mucosa by regulating vascular permeability and interstitial fluid pressure.

Interaction between prostanoids, NO, and VIP in modulation of duodenal alkaline secretion and motility

The relation between duodenal motility and duodenal mucosal alkaline secretion (DMAS) was examined in anesthetized rats. The duodenum was perfused with saline, and DMAS was determined by titration. Duodenal motility, assessed by intraluminal pressure measurements, was induced by indomethacin and/or N omega-nitro-L-arginine methyl ester (L-NAME) and inhibited by iloprost or vasoactive intestinal peptide (VIP). Six of 66 rats showed spontaneous duodenal contractions. Basal DMAS was higher in these rats than in those without contractions. Rats treated with indomethacin and L-NAME before abdominal operation exhibited duodenal motility postoperatively and had higher DMAS than in controls. Iloprost abolished both the duodenal motility increase and increase in DMAS induced by indomethacin. L-NAME-induced motility and increase in DMAS were antagonized by L-arginine. VIP increased DMAS without affecting motility. VIP abolished indomethacin-induced motility and augmented indomethacin-stimulated DMAS. VIP reduced L-NAME-induced motility and slightly increased L-NAME-stimulated DMAS. It is concluded that DMAS varies with duodenal motility. Prostaglandins and NO inhibit duodenal motility, thereby indirectly reducing DMAS. VIP may have dual effects on DMAS, an inhibitory action mediated via smooth muscle relaxation and a stimulatory action independent of motility.

Tachykinins increase vascular permeability in the gastrointestinal tract of the rat

The occurrence of inflammation as indicated by extravasation of Evans blue bound to plasma proteins was examined in various parts of the gastrointestinal tract in the rat, following administration of tachykinins, capsaicin and hydrochloric acid. Intravenous neurokinin A dose-dependently induced extravasation in stomach, duodenum, jejunum, caecum and colon, but had no effect in ileum. Neurokinin B equipotently induced extravasation in the stomach but had no effect in other parts of the gut and substance P had no effects on extravasation of Evans blue in any of the examined parts of the gastrointestinal tract. Capsaicin given intraperitoneally increased vascular permeability in stomach and duodenum only, while extravasation of Evans blue after capsaicin given intraluminally did not differ from the effect of the vehicle alone. As a comparison, HCl given intraluminally in the duodenum was found to induce a prominent extravasation of Evans blue of a greater magnitude than than of tachykinins. We suggest that tachykinins, and in particular neurokinin A, may be of importance for extravasation of plasma proteins as part of inflammatory reactions in the upper and lower gastrointestinal tract.

Effects of nitric oxide inhibition on duodenal function in rat: involvement of neural mechanisms

This study examines the integrative response of several duodenal functions to nitric oxide synthase inhibition. Effects of the nitric oxide synthase inhibitor N-nitro-L-arginine methyl ester (L-NAME) were studied in anesthetized rats, using in situ duodenal perfusion. L-NAME increased bicarbonate secretion, permeability, and fluid secretion and induced motility. Injection of L-arginine abolished L-NAME-induced motility and lowered the secretion of bicarbonate and fluid. Pretreatment with the nicotinic receptor antagonist hexamethonium prevented the rise in bicarbonate secretion and motility in response to L-NAME but did not affect the increase in mucosal permeability. Atropine diminished the L-NAME-induced increases in permeability, motility, and fluid secretion. The adrenolytic drug guanethidine did not alter the responses to the inhibitor. These results suggest that nitric oxide inhibits duodenal motility and bicarbonate secretion by suppressing a stimulatory, nicotinic receptor-dependent, neural mechanism. The L-NAME-induced contractions involve both a cholinergic, atropine-sensitive pathway and nonadrenergic, noncholinergic neural transmission. Muscarinic receptors also mediate part of the L-NAME-induced increases in mucosal permeability and fluid secretion.

Exposure of the duodenum to high concentrations of hydrochloric acid. Effects on mucosal permeability, alkaline secretion, and blood flow

Proximal duodenum was perfused with HCl for 5 min and the effects on blood-to-lumen clearance of 51Cr-EDTA (ED-Cl), morphology, luminal alkalinization, and blood flow determined in anesthetized rats. The rate of alkalinization was determined by back titration and blood flow assessed by laser Doppler flowmetry or by ultrasonic transit time flowmetry. Perfusion of duodenum with 30, 50 or 100 mM HCl for 5 min increased ED-Cl in a concentration-dependent manner and induced a small increase in alkalinization but had no effect on blood flow. At 55 min after cessation of perfusion with 100 mM HCl ED-Cl was 2.2-fold higher than control whereas the ED-Cl values in animals perfused with 30 or 50 mM HCl were not different from pre-acid control values. 100 mM HCl also induced an increase in 14C-mannitol and 14C-polyethylene glycol 4000 clearance, suggesting that HCl does indeed increase mucosal permeability. The 100 mM HCl-induced rise in mucosal permeability most probably reflects disturbance of mucosal integrity because three of five animals exhibited villous tip damage. The increases in ED-Cl in response to 100 mM HCl were the same in control rats as in rats with the renal pedicles ligated, indicating that the acid susceptibility is not affected by acute functional nephrectomy.

Duodenal mucosal alkaline secretion, permeability, and blood flow

The relationship between duodenal mucosal alkaline secretion, permeability, and blood flow was examined in anesthetized rats. Duodenum was perfused with saline, and rate of luminal alkalinization (LA), mucosal permeability (clearance of 51Cr-EDTA from blood to lumen), effluent volume, mean arterial blood pressure (MABP), and blood flow (laser-Doppler flowmetry) were determined. Infusion of vasoactive intestinal polypeptide (VIP, 13.5 micrograms.kg-1 x h-1 i.v.) increased LA and fluid secretion but decreased MABP and mucosal permeability. The concentration of base in the secreted fluid was 45 mM. Systemic infusion of VIP (2.5 micrograms.kg-1 x h-1) increased LA and fluid secretion; the HCO3- concentration in secreted fluid was 86 mM. The lower VIP dose affected neither blood flow nor mucosal permeability. Both intravenous (10 mg/kg + 3 mg.kg-1 x h-1) and intraluminal (3 x 10(-3) M) N omega-nitro-L-arginine (L-NNA) increased LA and effluent volume; the HCO3- concentration in the secreted fluid was 38 and 44 mM, respectively. Intravenous, but not intraluminal, L-NNA increased mucosal permeability and decreased blood flow. Reduction of arterial blood pressure by blood withdrawal or by injection of prazosin (50 micrograms/kg i.v.) or hexamethonium (20 mg/kg i.v.) decreased LA and mucosal permeability. Prazosin decreased blood flow, whereas hexamethonium slightly increased blood flow. We conclude that NO may be an inhibitory regulator of LA and that both L-NNA and VIP increase LA via stimulation of active HCO3- transport. VIP probably increases HCO3- and fluid secretion by two separate ion transport mechanisms. No causal relationship exists between LA and blood flow, between LA and mucosal permeability, or between mucosal permeability and blood flow. A positive linear correlation exists between MABP and mucosal permeability, suggesting that marked changes of MABP may influence permeation of small water-soluble solutes across duodenal mucosa.