Epidemiology and impact of methicillin-sensitive Staphylococcus aureus with β-lactam antibiotic inoculum effects in adults with cystic fibrosis

Staphylococcus aureus is the most prevalent cystic fibrosis (CF) pathogen. Several phenotypes are associated with worsened CF clinical outcomes including methicillin-resistance and small-colony-variants. The inoculum effect (IE) is characterized by reduced β-lactam susceptibility when assessed at high inoculum. The IE associates with worse outcomes in bacteremia and other high-density infections, and may therefore be relevant to CF. The prevalence of IE amongst a CF cohort (age ≥18 years), followed from 2013 to 2016, was investigated. Yearly methicillin-sensitive S. aureus (MSSA) isolates were screened at standard (5 × 105 CFU/mL) and high (5 × 107 CFU/mL) inoculum against narrow-spectrum anti-Staphylococcal β-lactams and those with anti-pseudomonal activity common to CF. A ≥ 4-fold increase in minimum inhibitory concentration between standard and high inoculum defined IE. Isolates underwent blaZ sequencing and genotyping and were compared against published genomes. Fifty-six percent (99/177) of individuals had MSSA infection. MSSA was observed at ≥105 CFU/mL in 44.8% of entry sputum samples. The prevalence of the IE was 25.0%-cefazolin; 13.5%-cloxacillin; 0%-meropenem; 1.0%-cefepime; 5.2%-ceftazidime; and 34.4%-piperacillin-tazobactam amongst baseline MSSA isolates assessed. blaZ A associated with cefazolin IE (P = 0.0011), whereas blaZ C associated with piperacillin-tazobactam IE (P < 0.0001). Baseline demographics did not reveal specific risk factors for IE-associated infections, nor were long-term outcomes different. Herein, we observed the IE in CF-derived MSSA disproportionally for cefazolin and piperacillin-tazobactam and this phenotype strongly associated with underlying blaZ genotype. The confirmation of CF being a high density infection, and the identification of high prevalence of MSSA with IE in CF supports the need for prospective pulmonary exacerbation treatment studies to understand the impact of this phenotype.

A two-ward acute care hospital outbreak of SARS-CoV-2 delta variant including a point-source outbreak associated with the use of a mobile vital signs cart and sub-optimal doffing of personal protective equipment

BACKGROUND

The arrival of the Delta variant of SARS-CoV-2 was associated with increased transmissibility and illness of greater severity. Reports of nosocomial outbreaks of Delta variant COVID-19 in acute care hospitals have been described but control measures varied widely.

AIM

Epidemiological investigation of a linked two-ward COVID-19 Delta variant outbreak was conducted to elucidate its source, risk factors, and control measures.

METHODS

Investigations included epidemiologic analysis, detailed case review serial SARS-CoV-2 reverse transcriptase-polymerase chain reaction (RT-PCR) testing of patients and healthcare workers (HCWs), viral culture, environmental swabbing, HCW-unaware personal protective equipment (PPE) audits, ventilation assessments, and the use of whole genome sequencing (WGS).

FINDINGS

This linked two-ward outbreak resulted in 17 patient and 12 HCW cases, despite an 83% vaccination rate. In this setting, suboptimal adherence and compliance to PPE protocols, suboptimal hand hygiene, multi-bedded rooms, and a contaminated vital signs cart with potential fomite or spread via the hands of HCWs were identified as significant risk factors for nosocomial COVID-19 infection. Sudden onset of symptoms, within 72 h, was observed in 79% of all Ward 2 patients, and 93% of all cases (patients and HCWs) on Ward 2 occurred within one incubation period, consistent with a point-source outbreak. RT-PCR assays showed low cycle threshold (C_T) values, indicating high viral load from environmental swabs including the vital signs cart. WGS results with ≤3 SNP differences between specimens were observed.

CONCLUSION

Outbreaks on both wards settled rapidly, within 3 weeks, using a `back-to-basics' approach without extraordinary measures or changes to standard PPE requirements. Strict adherence to recommended PPE, hand hygiene, education, co-operation from HCWs, including testing and interviews, and additional measures such as limiting movement of patients and staff temporarily were all deemed to have contributed to prompt resolution of the outbreak.

Rationale and development of a business case for antimicrobial stewardship programs in acute care hospital settings

Background

Antimicrobial stewardship programs (ASPs) have been shown to reduce inappropriate antimicrobial use and its consequences. However, these programs lack legislative requirements in many places and it can be difficult to determine what human resources are required for these programs and how to create a business case to present to hospital administrators for program funding. The objectives of the current paper were to review legislative requirements and outline human resource requirements for ASPs, and to create a base business case for ASPs.

Methods

A working group of antimicrobial stewardship experts from across Canada met to discuss the necessary components for creation of a business case for antimicrobial stewardship. A narrative review of the literature of the regulatory requirements and human resource recommendations for ASPs was conducted. Informed by the review and using a consensus decision-making process, the expert working group developed human resource recommendations based on a 1000 bed acute care health care facility in Canada. A spreadsheet based business case model for ASPs was also created.

Results

Legislative and /or regulatory requirements for ASPs were found in 2 countries and one state jurisdiction. The literature review and consensus development process recommended the following minimum human resources complement: 1 physician, 3 pharmacists, 0.5 program administrative and coordination support, and 0.4 data analyst support as full time equivalents (FTEs) per 1000 acute care beds. Necessary components for the business case model, including the human resource requirements, were determined to create a spreadsheet based model.

Conclusions

There is evidence to support the negative outcomes of inappropriate antimicrobial use as well as the benefits of ASPs. Legislative and /or regulatory requirements for ASPs are not common. The available evidence for human resource recommendations for ASPs using a narrative review process was examined and a base business case modelling scenario was created. As regulatory requirements for ASPs increase, it will be necessary to create accurate business cases for ASPs in order to obtain the necessary funding to render these programs successful.

Electronic supplementary material

The online version of this article (10.1186/s13756-018-0396-z) contains supplementary material, which is available to authorized users.

The development and application of a molecular community profiling strategy to identify polymicrobial bacterial DNA in the whole blood of septic patients

Background

The application of molecular based diagnostics in sepsis has had limited success to date. Molecular community profiling methods have indicated that polymicrobial infections are more common than suggested by standard clinical culture. A molecular profiling approach was developed to investigate the propensity for polymicrobial infections in patients predicted to have bacterial sepsis.

Results

Disruption of blood cells with saponin and hypotonic shock enabled the recovery of microbial cells with no significant changes in microbial growth when compared to CFU/ml values immediately prior to the addition of saponin. DNA extraction included a cell-wall digestion step with both lysozyme and mutanolysin, which increased the recovery of terminal restriction fragments by 2.4 fold from diverse organisms. Efficiencies of recovery and limits of detection using Illumina sequencing of the 16S rRNA V3 region were determined for both viable cells and DNA using mock bacterial communities inoculated into whole blood. Bacteria from pre-defined communities could be recovered following lysis and removal of host cells with > 97 % recovery of total DNA present. Applying the molecular profiling methodology to three septic patients in the intensive care unit revealed microbial DNA from blood had consistent alignment with cultured organisms from the primary infection site providing evidence for a bloodstream infection in the absence of a clinical lab positive blood culture result in two of the three cases. In addition, the molecular profiling indicated greater diversity was present in the primary infection sample when compared to clinical diagnostic culture.

Conclusions

A method for analyzing bacterial DNA from whole blood was developed in order to characterize the bacterial DNA profile of sepsis infections. Preliminary results indicated that sepsis infections were polymicrobial in nature with the bacterial DNA recovered suggesting a more complex etiology when compared to blood culture data.

Infection prevention and control measures for acute respiratory infections in healthcare settings: an update

Viruses account for the majority of the acute respiratory tract infections (ARIs) globally with a mortality exceeding 4 million deaths per year. The most commonly encountered viruses, in order of frequency, include influenza, respiratory syncytial virus, parainfluenza and adenovirus. Current evidence suggests that the major mode of transmission of ARls is through large droplets, but transmission through contact (including hand contamination with subsequent self-inoculation) and infectious respiratory aerosols of various sizes and at short range (coined as "opportunistic" airborne transmission) may also occur for some pathogens. Opportunistic airborne transmission may occur when conducting highrisk aerosol generating procedures and airborne precautions will be required in this setting. General infection control measures effective for all respiratory viral infections are reviewed and followed by discussion on some of the common viruses, including severe acute respiratory syndrome (SARS) coronavirus and the recently discovered novel coronavirus.

Treatment of infections caused by metallo-beta-lactamase-producing Pseudomonas aeruginosa in the Calgary Health Region

This study reviewed 56 patients with significant metallo-beta-lactamase (MBL)-producing Pseudomonas aeruginosa infections between May 2002 and March 2004 to identify features associated with mortality. Immunosuppression (p 0.002), bacteraemia (p 0.08) and inadequate antimicrobial therapy (p <0.001) were associated with death. Among those patients treated with adequate therapy, the use of multiple drug treatment regimens (two or three active agents) was associated with a non-significant two-fold increase in survival (p 0.45). Further prospective studies are warranted to determine the optimal treatment of MBL-producing P. aeruginosa infections.

Physical Plant Design and Engineering Controls to Reduce Hospital-acquired Infections

The importance of the environment as a reservoir for microorganisms implicated in disease transmission in the hospital setting has been increasingly recognized, especially with respect to dialysis units, ventilation in specialized areas, and the proper use of disinfectants (1). Inherent within the environmental setting is the importance of physical plant design. Several studies have underscored the importance of optimizing design standards to maximize patient and health care worker (HCW) safety, including the prevention of hospital-acquired infections in patients (2-6). Ulrich et al (7) recently completed an evidence-based review, entitled'The role of the physical environment in the hospital of the 21st century: A once-in-a-lifetime opportunity', for the Center for Health Design in California (USA), which was funded by the Robert Wood Johnson Foundation. Ulrich and colleagues identified over 600 studies that examined the hospital environment and its effects on staff effectiveness, patient safety, patient and family stress, quality and costs. They suggested that one of the important elements in improving patient safety is the reduction of the risk of hospital-acquired infections through improved facility design.

A comparison of multifaceted versus Clostridium difficile-focused VRE surveillance strategies in a low-prevalence setting

We compared our current screening strategy for vancomycin-resistant Enterococcus (VRE) with a focused strategy that screens all stool samples sent for Clostridium difficile toxin assay but limits rectal swab screening to wards with new VRE cases detected via C. difficile samples. The proposed strategy detects 72.7% of new VRE cases, with substantial cost savings.

Bioterrorism in 2001 - How ready are we?

On January 30, 2001, the federal Immigration Department's headquarters in Ottawa were evacuated and shut down following a bioterrorism scare, which turned out to be a hoax. The building reopened 48 h later, after it was determined that the substance found was not anthrax (1). In the same week, a similar hoax forced the evacuation of an Ontario provincial government building in Toronto (1).

Prospective randomized trial of 10% povidone-iodine versus 0.5% tincture of chlorhexidine as cutaneous antisepsis for prevention of central venous catheter infection

A multicenter prospective, randomized, controlled trial, with 0.5% tincture of chlorhexidene versus 10% povidone-iodine as cutaneous antisepsis for central venous catheter (CVC) insertion, was conducted for patients in intensive care units. Of 374 patients, 242 had a CVC inserted for >3 days and were used for the primary analysis. Outcomes included catheter-related bacteremia, significant catheter colonization (> or = 15 colony-forming units [cfu]), exit-site infection, serial quantitative exit-site culture (every 72 h), and molecular subtyping of all isolates. Patients in both study groups were comparable with respect to age, sex, underlying disease, length of hospitalization, reason for line insertion, and baseline APACHE II score. Documented catheter-related bacteremia rates were 4.6 cases per 1000 catheter-days in the chlorhexidine group (n=125) and 4.1 cases per 1000 catheter-days in the povidone-iodine group (n=117; not significant [NS]). Significant catheter-tip colonization occurred in 24 (27%) of 88 patients in the povidone-iodine group and in 31 (34%) of 92 patients in the chlorhexidine group (NS). A mean exit-site colony count of 5.9 x 10(5) cfu/mL per 25 cm(2) of the surface area of skin in the povidone-iodine group versus 3.1 x 10(5) cfu/mL per 25 cm(2) in the chlorhexidine group (NS) was found. There was a trend toward fewer exit-site infections in the chlorhexidine group (0 of 125 patients) versus those in the povidone-iodine group (4 of 117 patients; P=.053). Results of an intention-to-treat analysis were unchanged from the primary analysis. No difference was demonstrable between 0.5% tincture of chlorhexidine and 10% povidone-iodine when used for cutaneous antisepsis for CVC insertion in patients in the intensive care unit.

Lack of efficacy of oral bacitracin plus doxycycline for the eradication of stool colonization with vancomycin-resistant Enterococcus faecium

In a prospective observational cohort study designed to assess the role of oral bacitracin solution plus doxycycline in the eradication of intestinal carriage of vancomycin-resistant Enterococcus faecium (VREF) in patients on a renal ward, rectal swab specimens were obtained from 15 treated and 24 control patients. Cultures of the rectal swabs were negative for 15 (100%) of the antibiotic-treated vs. eight (33.3%) of the untreated patients (P < .001) on day 14. However, follow-up for a mean of 127 and 130 days revealed 9 of 15 (60%) and 15 of 24 (62.5%) in the treated and untreated cohorts (P = .86), respectively, carried VREF intermittently or persistently. Quantitative VREF stool cultures in the treated cohort revealed an initial 3.1-log10/g decrease, but there was an increase to pretreatment levels at 2-4 and 5-7 weeks post-treatment (7.8 and 7.4 log10/g). Oral bacitracin and doxycycline were not efficacious in reducing the carriage of VREF beyond the 2-week interval during which they were given.

Antibiotic prescribing for Canadian preschool children: evidence of overprescribing for viral respiratory infections

Antibiotic resistance is associated with prior receipt of antibiotics. An analysis of linked computerized databases for physician visits and antibiotic prescriptions was used to examine antibiotic prescribing for different respiratory infections in preschool children in Canada. In 1995, 64% of 61,165 children aged <5 years made 140,892 visits (mean, 3.6 visits per child) for respiratory infections; 74% of children who made visits received antibiotic prescriptions. Antibiotics were prescribed to 49% of children with upper respiratory tract infection, 18% with nasopharyngitis, 78% with pharyngitis or tonsillitis, 32% with serous otitis media, 80% with acute otitis media, 61% with sinusitis, 44% with acute laryngitis or tracheitis, and 24% with influenza. Acute otitis media accounted for 33% of all visits and 39% of all antibiotic prescriptions. The estimated Canadian-dollar cost of overprescribing was $423,693, or 49% of the total cost of antibiotics ($859,893) used in this group. This population-based study confirms antibiotic overprescribing in Canada.

Orally administered dextran sulfate is absorbed in HIV-positive individuals

Preliminary in vivo studies suggested that oral dextran sulfate was poorly absorbed, but investigations were limited by inadequate methods for measuring the drug in the body. To determine absorption in HIV-positive subjects, hydrogenated dextran sulfate, average molecular weight 8000 (Usherdex 8), was orally administered in a short-term (single dose, 4 g/day for 5 days, 7 subjects) and in a long-term study (1 g, 4 times per day for 29 to 335 days, 8 subjects), which was a continuation of the short-term study with the inclusion of an additional subject. When an agarose gel electrophoresis technique with toluidine blue staining was used, the drug was recovered from plasma (67%, peak 2.2 microg/mL) and circulating peripheral blood lymphocyte (PBL) samples (50%, peak 333 microg/L blood) obtained at 5 and 15 minutes and 1, 3, 6, and 24 hours after the first day's dose and from plasma (56%) and PBL samples (38%) obtained 5 minutes after administration on 4 subsequent days in the short-term study. In the long-term study, the drug was found in plasma (67%, peak 2.4 microg/mL) and PBL samples (25%, peak 126 microg/L blood) obtained at monthly visits within 4 hours of the last dose. The drug was found in all urine samples from all subjects in both studies (short-term study, 24-hour samples up to 4 days after the final dose; long-term study, monthly samples within 4 hours of the last dose). In the long-term study, bone marrow preparations from 3 subjects showed metachromatic inclusions present in reticular cells when the cells were stained with toluidine blue, indicating the presence of sulfated polyanions. A significant rise in activated partial thromboplastin time and a drop in platelet count (P < .025) were demonstrated, with thrombocytopenia developing in 3 patients. Mild-to-moderate gastrointestinal disturbances were experienced by 6 subjects in the short-term study and by all subjects in the long-term study. One subject experienced mild central nervous system symptoms in the short-term study. These results indicate that dextran sulfate is absorbed after oral administration; therefore, further studies on its efficacy, particularly in the early stages of the disease, along with additional observations on its toxicity, are warranted.

Multicenter randomized trial of fluconazole versus amphotericin B for treatment of candidemia in non-neutropenic patients. Canadian Candidemia Study Group

A randomized trial was conducted to compare the efficacy and safety of fluconazole versus that of amphotericin B in the treatment of candidemia in non-neutropenic adults. Enrollment was stratified by disease severity (APACHE II score). Patients were randomized (1:1) to receive amphotericin B 0.6 mg/kg/day (cumulative dose 8 mg/kg) or fluconazole 800 mg intravenous loading dose, then 400 mg daily for four weeks (intravenous for at least 10 days). Patients were monitored for six months. A total of 106 patients were enrolled. A protocol amendment implemented midway through the trial required patients to be removed from the study and treated with amphotericin B if species identification indicated candidemia due to Candida glabrata or Candida krusei. Baseline characteristics were similar for the two groups; 103 patients (fluconazole, 50; amphotericin B, 53) met the major enrollment criteria. The intention-to-treat analysis indicated successful therapy in 50% of fluconazole recipients compared to 58% of the amphotericin B group (p = 0.39; one-sided 95% CI, -8 to 24%). The efficacy analysis included 84 patients (fluconazole, 42; amphotericin B, 42); successful outcomes were observed in 57% and 62% of cases in the fluconazole and amphotericin B groups, respectively (p = 0.66: one-sided 95% CI, -12 to 22%). The mortality at day 14 for the fluconazole group was 26% and for the amphotericin B group 21% (p = 0.52; chi-square test) and remained similar throughout the course of follow-up, Drug-related adverse events were more frequent with amphotericin B than with fluconazole and prompted switching of therapy for two (4%) and zero cases, respectively. Fluconazole and amphotericin B were associated with similar clinical response rates and survival in the treatment of candidemia among non-neutropenic patients; however, drug-related adverse events were more frequent with amphotericin B.

Development of an intravenous-to-oral route conversion program for antimicrobial therapy at a Canadian tertiary care health facility

OBJECTIVE

To describe the effect of introducing a route conversion program on the prescribing of antimicrobials for the treatment of respiratory tract infections and skin/soft tissue infections in a sample population.

DESIGN

Concurrent, pre- and postintervention study.

SETTING

Four general internal medicine wards at The Toronto Hospital, a 1170-bed, tertiary care health center in Toronto, Ontario, Canada.

PARTICIPANTS

Patients receiving antimicrobial therapy for respiratory tract infections and skin/soft tissue infections.

INTERVENTION

Written guidelines and education sessions were presented to residents, interns, medical students, and pharmacists responsible for the care of patients admitted to four general internal medicine wards.

MAIN OUTCOME MEASURES

Clinical and laboratory parameters related to the status of the infection were monitored prospectively and compared with the course of drug therapy, with consideration of the patient's ability to meet the criteria established in the guidelines. The number of days of intravenous therapy prescribed despite appropriateness of oral therapy was tallied.

RESULTS

Twenty-seven patients (28 infections) were identified for inclusion in the 7-week preliminary audit, and 30 patients (32 infections) were included in the audit after the program, which continued for 5 weeks. Following implementation of the program, the number of days that intravenous therapy was continued despite the appropriateness of oral therapy was reduced from 41% to 26% of the total days of intravenous therapy prescribed.

CONCLUSIONS

The program had a positive influence on antimicrobial prescribing behavior in the population studied. Strategies to ensure continued benefit from the program have been developed.

Validating the integrity of one-way check valves for the delivery of contrast solution to multiple patients

The infusion of contrast solution into multiple patients from a single infusion bag is desired in clinics concerned with the high cost of the solution. Using one-way check valves in the infusion line is a protection method to reduce the risk of blood-borne cross-contamination. The suitability of this method is assessed through testing of the operating characteristics of the valves and infusion system and the high back pressure testing of the valves. The results indicate that the use of back-flow valves can ensure the prevention of flow from the patient to the injector. Results also indicate that the use of sprung valves, those which require a significant forward pressure to open them, are more appropriate for this application.

Molecular typing of Stenotrophomonas (Xanthomonas) maltophilia by DNA macrorestriction analysis and random amplified polymorphic DNA analysis

Stenotrophomonas (Xanthomonas) maltophilia is a multidrug-resistant, nosocomial pathogen for which optimal typing methods in epidemiologic investigations of nosocomial outbreaks have not been defined. We compared DNA macrorestriction analysis by pulsed-field gel electrophoresis (PFGE) with random amplified polymorphic DNA (RAPD) analysis by arbitrarily primed PCR for molecular typing of 109 multidrug-resistant strains of S. maltophilia from multiple outbreaks at our institution over a 10-month period in 1993. PFGE after digestion with restriction endonuclease DraI revealed 62 unique DNA restriction profiles among the 109 strains, with 23, 11, 6, 6, and 3 strains having concordant profiles in each of five types. There were four concordant profiles among 8 strains (2 strains with each profile), while unique profiles were present in each of the remaining 52 strains. Further RAPD analysis with a decanucleotide primer showed the same number of distinct strain types as PFGE but more subtype diversity within each clonal type. We concluded that DNA macrorestriction analysis and RAPD analysis are sufficiently discriminatory and useful for differentiation of S. maltophilia strains in epidemiologic investigations of nosocomial outbreaks. However, RAPD analysis by arbitrarily primed PCR is faster and less laborious method of molecular typing.

Retrospective analysis of the clinical and economic outcomes of twice-daily dosing of cefotaxime in a Canadian tertiary care institution

A retrospective analysis of the clinical and economic outcome of a regimen of cefotaxime 1 g given every 12 h was conducted following the introduction of an institutional policy recommending this new dosing strategy. Patients were identified from a log order entry in the pharmacy, and the medical records were reviewed using a standardized data collection form. Explicit criteria were applied for the indications for antimicrobial therapy, presence of infection, and outcome parameters. A total of 60 patients with a mean (+/- SD) age of 56.2 (+/- 17.8) years and a mean (+/- SD) length of stay of 20.75 (+/- 18.1) days were identified. Of these, 48 (80%) were found to have a clinically or microbiologically documented infection, and of the 42 patients who could be assessed accordingly to the criteria chosen, 37 (88%) had a favorable clinical response; 21 patients (35%) received cefotaxime alone. The costs for administration of cefotaxime have decreased by approximately 30% since the introduction of this new dosing regimen.

Pneumonia with pleural effusion due to Legionella pneumophila serogroup Lansing 3

We describe a case of pneumonia with pleural effusion due to Legionella pneumophila serogroup Lansing 3 in a human immunodeficiency virus-infected person. The 55-year-old man had been treated with immunosuppressive agents for hypersensitivity pneumonitis.

Comparison of single-dose cefotetan and multidose cefoxitin as intravenous prophylaxis in elective, open biliary tract surgery: a multicentre, double-blind, randomized study

OBJECTIVE

To compare the safety, tolerance and prophylactic effectiveness of a single 2-g dose of cefotetan with a standard prophylactic regimen of cefoxitin in reducing the incidence of postoperative infections after elective, open biliary tract surgery.

DESIGN

Multicentre, double-blind, randomized comparative study with a 4-week follow-up.

SETTING

Five Canadian university centres.

PARTICIPANTS

One hundred and eleven patients scheduled to undergo elective, open biliary tract surgery.

INTERVENTIONS

The patients were randomly assigned to receive either cefotetan or cefoxitin in a ratio of 2:1; 76 patients received cefotetan and 35 received cefoxitin.

MAIN OUTCOME MEASURES

Wound infection as defined by the Centers for Disease Control and Prevention and by clinical evaluation, adverse events and laboratory parameters.

RESULTS

Two incisional wound infections were reported by patients in the cefotetan group, for an overall infection rate of 1.8% (2 of 111). No significant differences were found in the failure rate or in any other indicator of efficacy. The incidence of adverse events for cefotetan (12.6%) was not statistically different from that for cefoxitin (10.4%), and none of the 16 adverse events in the cefotetan group and 5 in the cefoxitin group was serious or severe. Only one event (rash) was possibly related to the study drugs. Several hematologic and biochemical parameters were found to be normal preoperatively and abnormal postoperatively, but no relation was found between these variations and the study drugs. These changes were mainly attributable to the operation.

CONCLUSION

Cefotetan was found to be effective and comparable to cefoxitin, both in safety and in reducing the incidence of infection after elective, open biliary tract surgery.

The contribution of vitamin K2 (menaquinones) produced by the intestinal microflora to human nutritional requirements for vitamin K

BACKGROUND

Coagulopathy manifest by elevation of the prothrombin time (PT) in patients receiving broad spectrum antimicrobials indirectly suggests a role for intestinal microflora synthesized menaquinone (MK) in the maintenance of normal coagulation. Nonetheless, no direct evidence is available to support this contention.

OBJECTIVE

Our objective was therefore to provide evidence that bacterially produced MK may be absorbed by the distal small bowel of humans.

METHODS

Using a cell harvester, Staphylococcus aureus (ATCC 29213) was grown in 12-L batches, harvested, and extracted by high performance liquid chromatography (HPLC) to obtain 8 mg of pure MK. Four normal volunteers were placed on a diet severely restricted in vitamin K1 (median 32-40 U/day), and were given warfarin to maintain an International Normalized Ratio of approximately 2.0. On the 10th day of warfarin administration, naso-ileal intubation was performed and 1.5 mg of MK was delivered into the ileum. PT, factor VII, II and serum vitamin K1 levels were monitored throughout the study.

RESULTS

Mean serum vitamin K1 levels were reduced to 30% of the pre-diet value at the time of MK administration. Within 24 h of ileal MK administration, there was a significant (p < 0.05) increase in the factor VII level of 0.28 +/- 0.10 U/ml (mean +/- SEM) and a significant decrease of 2.5 (+/- 0.1) s in the PT, whereas in the control phase (during which no MK was administered), there were no significant changes in the PT or factor VII at corresponding time intervals.

CONCLUSION

These data provide direct evidence for the absorption of vitamin K2 from the distal small bowel, supporting a definite role for bacterially synthesized vitamin K2 in contributing to the human nutritional requirements of this vitamin.

Treatment of acute uncomplicated urinary tract infections with 3 days of lomefloxacin compared with treatment with 3 days of norfloxacin

The bacteriologic and clinical efficacies of 3 days of lomefloxacin therapy were compared with those of 3 days of norfloxacin therapy for the treatment of acute uncomplicated urinary tract infections in a prospective, randomized, double-blind study. One hundred sixty-four subjects were enrolled at five Canadian centers; 84 received lomefloxacin, and 80 received norfloxacin. Escherichia coli (84%) and Staphylococcus saprophyticus (11%) were the most common organisms isolated. Forty subjects (24%) had low quantitative counts in their pretherapy urine specimens. In the intent-to-treat analysis, 76 lomefloxacin subjects (91%) and 76 norfloxacin subjects (95%) were cured or improved at follow-up 5 to 9 days posttreatment and 73 (87%) and 71 (89%) subjects from the lomefloxacin and norfloxacin groups, respectively, were cured or improved at 4 to 6 weeks posttreatment. Bacteriologic eradication occurred in 61 of 63 lomefloxacin subjects (97%) with > or = 10(8) CFU/liter in their pretherapy specimens and 56 of 59 norfloxacin subjects (95%) at 5 to 9 days and 55 (87%) and 53 (90%) subjects from the lomefloxacin and norfloxacin groups, respectively, at 4 to 6 weeks. There were no statistically significant differences in outcome. Adverse effects which were potentially related to the study medications were reported by 26% of the subjects who received lomefloxacin and 25% of the subjects who received norfloxacin. There were no severe adverse events, and only one subject discontinued therapy. These data suggest that 3 days of therapy with either lomefloxacin or norfloxacin is effective in the treatment of acute uncomplicated urinary tract infections.

Contamination study of multiple-dose vials

OBJECTIVE

To document the number of opened, dated, and expired multiple-dose vials (MDVs) in patient-care areas and to determine what proportion of MDVs were contaminated with bacteria or cellular debris.

DESIGN

Every tenth opened MDV (69/656) identified on the wards was collected, ensuring representation from each nursing unit. Contents were examined for contamination.

SETTING

Medical-school-affiliated, tertiary care center.

MAIN OUTCOME MEASURES

(1) Visual inspection for debris, medication type, location, lot number, manufacturer's expiration date, and date of opening; (2) culture in solid and broth media for bacterial growth; and (3) staining and microscopic examination for cellular constituents.

RESULTS

No vials had been dated after opening and 4.6 percent were expired according to the manufacturer's expiration date. No bacterial contamination was evident; however, one vial was contaminated with red blood cells.

CONCLUSIONS

Transmission of infection via contaminated MDVs has been well documented and contamination with red blood cells raises concerns about potential for transmission of bloodborne pathogens. Recommendations include dating MDVs after opening, emphasizing the need for proper aseptic technique, and discarding MDVs on the manufacture's date of expiration.

The absorption and bioactivity of bacterially synthesized menaquinones

After optimizing conditions for maximal production of menaquinones (MK), S. aureus and B. vulgatus were grown in batches, harvested and extracted for qualitative and quantitative MK content utilizing HPLC (high performance liquid chromatography) until a total of 6 mg was available. Five normal healthy male volunteers were placed on a vitamin K1 deficient diet (< or = 25 micrograms/day) and were subsequently warfarinized to maintain a prothrombin time (PT) 1.5-2 times control. Following stabilization of daily warfarin dosage 1 mg doses of the extracted MK were orally administered. As a control, the same volunteers were later warfarinized but no MK was given. Within 24 h of MK administration the prothrombin time (PT) decreased (mean +/- SEM) 3.6 +/- 1.0 s (p < 0.005) and the Factor VII level increased 0.36 +/- 0.3 u/ml (p < 0.005) vs a PT increase of 1.0 +/- 1.0 s (p > 0.1) and a Factor VII level increase of 0.03 +/- 0.1 u/ml (p > 0.1) in the control phase. Within 48 h of MK administration the PT was normal in all subjects but remained > or = 1.5 times control in the control phase. These data demonstrate for the first time the absorption and bioactivity of bacterially synthesized vitamin K in humans.

The production of menaquinones (vitamin K2) by intestinal bacteria and their role in maintaining coagulation homeostasis

Vitamin K is an essential cofactor necessary for the production of clotting factors II, VII, IX, and X in humans and has recently been found to be an essential factor for many other proteins in the body. There are two sources of this essential vitamin, including vitamin K1, or phylloquinone which is primarily found in green leafy vegetables and vitamin K2 or menaquinone which is synthesized by certain intestinal bacteria. The precise contribution of the bacterially synthesized menaquinone to overall vitamin K requirements in man is unknown. This paper reviews the available literature regarding the production and liberation of menaquinones from bacteria, the animal experiments which have been done to examine the absorption of menaquinones and the indirect and direct evidence in humans regarding utilization of menaquinones. The preponderance of the evidence suggests that bacterially synthesized menaquinones, particularly in the ileum can and do play a significant role in contributing to vitamin K requirements in humans to prevent clinically significant coagulopathy, especially during periods of episodic dietary lack of the vitamin.

Quantitative and qualitative measurements of K vitamins in human intestinal contents

Little data are available with regard to the amount and types of bacterially synthesized menaquinones within the human intestinal tract. Quantitative reverse phase high performance liquid chromatographic (HPLC) analysis of the distal colonic contents of 10 male volunteers revealed the following: (mean +/- SEM) micrograms/g dry weight: MK-4 to MK-7 5.55 (+/- 0.27); MK-9,10 14.54 +/- 0.29; K1 1.31 (+/- 0.14). Similar analyses of the colostomy contents of subjects revealed a total menaquinone content of 8.85 micrograms/g dry weight. The total intestinal contents obtained from five subjects after isotonic saline purgation qualitatively revealed MK-4 to MK-11 with a mean (+/- SEM) content of MK-4 to MK-10 of 5.4 +/- 2.1 micrograms/g dry weight or a mean (+/- SEM) of 1.6 +/- 0.7 mg dry weight of the total contents (243 g). The quantitative mean growth for the major menaquinone producers Escherichia coli and Bacteroides species was 5.2 +/- 3.2 and 9.2 +/- 1.8 log10 CFU/g dry weight, respectively. These results indicate that menaquinones are present in significant concentration in the human intestinal tract, and a potentially large reservoir of vitamin K may be available to the host.

A multicenter, open comparative study of parenteral cefotaxime and ceftriaxone in the treatment of nosocomial lower respiratory tract infections

A multicenter Canadian study enrolled 74 persons to compare low-dose cefotaxime at 1 g every 8 hr to ceftriaxone 1 g every 12 hr in patients with nosocomial pneumonia. Of 57 evaluable patients (30 cefotaxime and 27 ceftriaxone) in this preliminary report, 93% responded to therapy in both groups. Ceftriaxone patients tended to have more side effects (14.2%). This study is continuing to accrue patients to achieve 100 evaluable patients. Interim data, however, support the continued use of low-dose cefotaxime as an appropriate alternative for clinically effective and cost-effective management of nosocomially acquired pneumonia.

Antibiotic-associated hypoprothrombinemia: a review of prospective studies, 1966-1988

Many antimicrobial agents have been associated with hypoprothrombinemia. The precise mechanisms are unknown, but alteration in vitamin K status or utilization is involved. The two postulated mechanisms implicate either direct inhibition of biosynthesis of the vitamin K-dependent clotting factors by the N-methylthiotetrazole (NMTT) moiety found in certain antimicrobial agents or eradication of vitamin K-producing intestinal microflora in patients with reduced oral intake of vitamin K. An English-language review of all prospective studies reported between 1966 and 1988 in which serial prothrombin times were monitored in adult patients revealed that the incidence of hypoprothrombinemia varied from 3.7% to 64% with NMTT-containing regimens and from 0% to 24% with non-NMTT-containing regimens. Detailed evaluation of these and other studies suggests that certain risk factors, including malnutrition, hepatic and renal dysfunction, older age, and severity of illness, may be the major determinants of hypoprothrombinemia. The hypothesis that the NMTT side chain is primarily responsible for hypoprothrombinemia may not be justified. We conclude that patients at high risk for coagulopathy should be carefully monitored and that serious consideration should be given to the use of prophylactic vitamin K in such cases.

Herpes labialis in parturients receiving epidural morphine following cesarean section

A significant association exists between the use of epidural morphine (EM), reactivation of herpes labialis (HL) commonly known as coldsores, and pruritus in the obstetric population. A randomized prospective study was designed to eliminate previously identified confounding variables. Immediately following delivery, parturients having undergone cesarean section with epidural anesthesia with carbonated lidocaine (Xylocaine CO2, Astra, Mississauga, Ontario, Canada) with 1:200,000 epinephrine were sequentially randomized to receive either EM or im opioids for postoperative analgesia. One blood sample was collected for viral serology and two mouthwashes (day 0 and 2) were collected to determine oral viral shedding. The patients were observed daily for 5 days. Coldsores were cultured for herpes simplex virus (HSV). Of 187 patients, 96 received EM and 91 im opioids; herpes labialis occurred in 14 of 96 (14.6%) of the former but in 0 of 91 of the latter (P = 0.0004). All 14 experienced facial pruritus. The two groups were at equal risk for reactivation (seropositivity 64.6% and 62.6%, respectively). Analysis of data for those with positive HSV serology reveals 14 of 62 (22.5%) had EM and herpes labialis compared with 0 of 57 in the im group (P less than 0.0001). The incidence of oral viral shedding was low. Surgical stress, the local anesthetic solution, and epinephrine addition to the local anesthetic were eliminated as confounders. Stepwise logistic regression analysis revealed that EM and a history of herpes labialis in these patients were predictive for reactivating oral HSV.

Handwashing practices in an intensive care unit: the effects of an educational program and its relationship to infection rates

Handwashing is the single most important procedure in the prevention of nosocomial infections and yet it remains the most violated of all infection control procedures. With a sequential intervention study in an intensive care unit we have demonstrated that poor handwashing practices are associated with a high nosocomial infection rate, whereas good handwashing practices are associated with a low nosocomial infection rate. An educational and enforcement program designed to improve handwashing procedures can significantly reduce endemic nosocomial infection rates.

Appropriateness of metronidazole use in a teaching hospital

The appropriateness of metronidazole use at a teaching hospital was determined by a retrospective audit. All orders for metronidazole received by the hospital pharmacy from December 26, 1986, to May 15, 1987, were identified, and the charts of the patients involved were reviewed to determine whether the drug's use was appropriate or inappropriate according to pre-established guidelines for indication, dose, dosage interval, and duration of therapy or prophylaxis. The oral route of administration was considered appropriate for patients who were taking other oral medications or who were on a diet of at least clear fluids. The acquisition cost of metronidazole from January to June 1987 was used to determine the potential cost avoidance that would result if (1) all types of inappropriate use were corrected, or (2) only the inappropriate route of administration were corrected. A total of 104 courses of therapy in 98 patients were evaluated, of which 76 were therapeutic and 28 were prophylactic. Of the 104 courses, 62% were found to be inappropriate by at least one of the criteria for appropriate use, excluding route of administration. Of the 893 doses of metronidazole administered by the i.v. route, 424 (47%) could have been given orally. A drug cost analysis revealed that $3954 (48% of the total hospital expenditure for metronidazole) could have been saved by substituting oral metronidazole for i.v. metronidazole when possible. If all criteria for appropriate use of metronidazole had been followed, $5977 could have been saved, which represents 71% of the current hospital expenditure for metronidazole.(ABSTRACT TRUNCATED AT 250 WORDS)

A prospective, randomized study comparing transparent and dry gauze dressings for central venous catheters

Patients having central venous catheters for three or more days were prospectively randomized to receive a transparent (n = 58) or gauze (n = 57) dressing to compare the incidence of insertion site colonization, local catheter-related infection, and catheter-related sepsis. Quantitative cultures of the catheter insertion site (25 cm2) revealed significantly greater colonization (P less than or equal to .009) after 48 h in the transparent versus the gauze dressing group. Local catheter-related infection occurred significantly more often (P = .002) in the transparent (62%) than in the gauze group (24%). Seven episodes of catheter-related bacteremia occurred in the transparent group (16.6%) and none in the gauze group (P = .015). Stepwise logistic regression analysis revealed that cutaneous colonization at the insertion site of greater than or equal to 10(3) cfu/mL (relative risk, 13.16) and difficulty of insertion (relative risk, 5.39) were significant factors for catheter-related infection. These data suggest that transparent dressings are associated with significantly increased rates of insertion site colonization, local catheter-related infection, and systemic catheter-related sepsis in patients with long-term central venous catheters.

Recurrent herpes simplex virus labialis and the use of epidural morphine in obstetric patients

A retrospective study of sequential obstetric patients delivering at University Hospital and receiving epidural anesthesia was conducted to determine if a suggested association exists between the recurrence of oral herpes simplex lesions and the use of epidural morphine. In a retrospective study of 291 patients, 13 of 134 (9.7%) receiving epidural morphine developed recurrent oral herpes lesions in contrast to 1 of 157 (0.6%) not receiving the drug (P less than 0.001). In a prospective hospital-based study of 729 consecutive obstetric patients, 146 patients received epidural opioids (morphine, fentanyl, or both) and 583 did not. Recurrent HSVL lesions occurred in 13 of 140 (9.3%) patients given epidural morphine but in only 6 of 583 (1.0%) not given epidural opioids (P less than 0.001). Three of the 13 patients with HSVL received both epidural morphine and fentanyl and 10 received only epidural morphine. Because of the small numbers of patients receiving only fentanyl, no relation between HSVL reactivation and epidural fentanyl could be established. In patients having caesarean sections, the association of recurrent HSVL and the use of epidural morphine was significant (P = 0.04), suggesting cesarean delivery was not a confounder. A hitherto undescribed triggering agent, epidural morphine, appears to be associated with reactivation of HSVL in obstetric patients in the postpartum period.

Recurrent herpes simplex virus labialis and the use of epidural morphine in obstetric patients

A retrospective study of sequential obstetric patients delivering at University Hospital and receiving epidural anesthesia was conducted to determine if a suggested association exists between the recurrence of oral herpes simplex lesions and the use of epidural morphine. In a retrospective study of 291 patients, 13 of 134 (9.7%) receiving epidural morphine developed recurrent oral herpes lesions in contrast to 1 of 157 (0.6%) not receiving the drug (P less than 0.001). In a prospective hospital-based study of 729 consecutive obstetric patients, 146 patients received epidural opioids (morphine, fentanyl, or both) and 583 did not. Recurrent HSVL lesions occurred in 13 of 140 (9.3%) patients given epidural morphine but in only 6 of 583 (1.0%) not given epidural opioids (P less than 0.001). Three of the 13 patients with HSVL received both epidural morphine and fentanyl and 10 received only epidural morphine. Because of the small numbers of patients receiving only fentanyl, no relation between HSVL reactivation and epidural fentanyl could be established. In patients having caesarean sections, the association of recurrent HSVL and the use of epidural morphine was significant (P = 0.04), suggesting cesarean delivery was not a confounder. A hitherto undescribed triggering agent, epidural morphine, appears to be associated with reactivation of HSVL in obstetric patients in the postpartum period.

Pseudomonas cepacia colonization and infection in intensive care units

Pseudomonas cepacia has become a prominent epidemic nosocomial pathogen over the past 15 years. Between December 1982 and September 1983 it was isolated from 29 patients in two intensive care units (ICUs) at one hospital. Twelve infections--five bacteremias, four pneumonias and three urinary tract infections--occurred. Most of the isolates (25/29) were from the respiratory tract, and most (23/29) had the same antibiogram as the only environmental isolate, which was cultured from a contaminated ventilator thermometer, a previously unrecognized source of nosocomial infection. The ventilator thermometers were calibrated in a bath whose water had not been changed for months and contained P. cepacia. Despite elimination of this reservoir, P. cepacia was eradicated from the ICUs only after intensive infection control efforts were instituted.

Antimicrobial cream susceptibility testing

Utilizing a recently described rapid needle extrusion method for determining the sensitivities of burn wound isolates, we have compiled data on the resistance patterns of over 250 isolates from our burn unit. Major isolate groups were Staphylococcus aureus, Pseudomonas aeruginosa, various Enterobacteriaceae and Enterococci. Excellent correlation was exhibited between the inhibitory zone sizes and the minimal inhibitory concentration for 120 organisms tested. Utilizing the needle extrusion sensitivities to facilitate the selection of the burn creams, a significant reduction in the microbiologic flora of the burn wound was noted. The utilization of this technique in the selection of burn creams deserves controlled trials to assess whether changes in topical therapy might alter clinical outcome.

Preservation of colonization resistance parameters during empiric therapy with aztreonam in the febrile neutropenic patient

The role of the anaerobic intestinal flora in maintaining colonization resistance was examined in a study of empiric therapy in febrile neutropenic patients who received aztreonam plus tobramycin, aztreonam plus cloxacillin, or moxalactam plus tobramycin, regimens with differential effects on the anaerobic intestinal flora. Surveillance cultures showed that all regimens eradicated fecal carriage of enteric gram-negative bacilli but that fecal acquisition of fungi occurred in 4 (27%) of 15 aztreonam/tobramycin, 6 (43%) of 14 aztreonam/cloxacillin, and 13 (81%) of 16 moxalactam/tobramycin recipients. Fungi were acquired at 11 (22%) of 49 sites in aztreonam/tobramycin, 15 (31%) of 48 sites in aztreonam/cloxacillin, and 28 (54%) of 52 sites in moxalactam/tobramycin recipients. Aztreonam/tobramycin reduced fecal anaerobe counts by less than 1 log10; aztreonam/cloxacillin, by a mean of 2.5 log10; and moxalactam/tobramycin, by 5.1 log10 colony-forming units (cfu)/g of feces by day 10 +/- 3 of therapy. Elimination of the anaerobes was reflected by a reduction in concentrations of short-chain fatty acids (SCFAs) in fecal supernatants. Fecal specimens containing greater than or equal to 10(6) cfu of Bacteroides fragilis group organisms/g (dry weight) contained significantly higher concentrations of succinic, propionic, and isobutyric acids. Flat SCFA chromatograms were observed in 90% of fecal samples from which no anaerobes were recovered. Preservation of the anaerobic flora appears critical in the prevention of fungal acquisition in neutropenic patients.

Production of menaquinones by intestinal anaerobes

Ninety intestinal organisms (71 isolates from fecal samples of neutropenic patients with cancer or from various sites in patients with intraabdominal infections and 19 control strains) were examined by reverse-phase thin-layer chromatography for their ability to produce menaquinones in vitro. Menaquinones were found in all of 24 organisms of the Bacteroides fragilis group. Two other Bacteroides species, Bacteroides disiens and Bacteroides bivius, also produced menaquinones. A single isolate of Bacteroides species lacked menaquinones. These constituents were found in all of five strains of Escherichia coli, all of four strains of Klebsiella pneumoniae, five of eight strains of Propionibacterium species, two of five strains of Eubacterium species, and the one strain each of Arachnia propionica and Veillonella parvula tested. No menaquinones were detected in organisms of the genera Fusobacterium, Clostridium, Bifidobacterium, Lactobacillus, Actinomyces, Peptococcus, or Peptostreptococcus. These findings suggest that E. coli, Bacteroides species, and some gram-positive, anaerobic, non-spore-forming bacilli produce menaquinones that may be a source of vitamin K in patients who are deprived of exogenous vitamin K1.