Nasal Iodophor Antiseptic vs Nasal Mupirocin Antibiotic in the Setting of Chlorhexidine Bathing to Prevent Infections in Adult ICUs: A Randomized Clinical Trial

Importance

Universal nasal mupirocin plus chlorhexidine gluconate (CHG) bathing in intensive care units (ICUs) prevents methicillin-resistant Staphylococcus aureus (MRSA) infections and all-cause bloodstream infections. Antibiotic resistance to mupirocin has raised questions about whether an antiseptic could be advantageous for ICU decolonization.

Objective

To compare the effectiveness of iodophor vs mupirocin for universal ICU nasal decolonization in combination with CHG bathing.

Design, Setting, and Participants

Two-group noninferiority, pragmatic, cluster-randomized trial conducted in US community hospitals, all of which used mupirocin-CHG for universal decolonization in ICUs at baseline. Adult ICU patients in 137 randomized hospitals during baseline (May 1, 2015-April 30, 2017) and intervention (November 1, 2017-April 30, 2019) were included.

Intervention

Universal decolonization involving switching to iodophor-CHG (intervention) or continuing mupirocin-CHG (baseline).

Main Outcomes and Measures

ICU-attributable S aureus clinical cultures (primary outcome), MRSA clinical cultures, and all-cause bloodstream infections were evaluated using proportional hazard models to assess differences from baseline to intervention periods between the strategies. Results were also compared with a 2009-2011 trial of mupirocin-CHG vs no decolonization in the same hospital network. The prespecified noninferiority margin for the primary outcome was 10%.

Results

Among the 801 668 admissions in 233 ICUs, the participants' mean (SD) age was 63.4 (17.2) years, 46.3% were female, and the mean (SD) ICU length of stay was 4.8 (4.7) days. Hazard ratios (HRs) for S aureus clinical isolates in the intervention vs baseline periods were 1.17 for iodophor-CHG (raw rate: 5.0 vs 4.3/1000 ICU-attributable days) and 0.99 for mupirocin-CHG (raw rate: 4.1 vs 4.0/1000 ICU-attributable days) (HR difference in differences significantly lower by 18.4% [95% CI, 10.7%-26.6%] for mupirocin-CHG, P < .001). For MRSA clinical cultures, HRs were 1.13 for iodophor-CHG (raw rate: 2.3 vs 2.1/1000 ICU-attributable days) and 0.99 for mupirocin-CHG (raw rate: 2.0 vs 2.0/1000 ICU-attributable days) (HR difference in differences significantly lower by 14.1% [95% CI, 3.7%-25.5%] for mupirocin-CHG, P = .007). For all-pathogen bloodstream infections, HRs were 1.00 (2.7 vs 2.7/1000) for iodophor-CHG and 1.01 (2.6 vs 2.6/1000) for mupirocin-CHG (nonsignificant HR difference in differences, -0.9% [95% CI, -9.0% to 8.0%]; P = .84). Compared with the 2009-2011 trial, the 30-day relative reduction in hazards in the mupirocin-CHG group relative to no decolonization (2009-2011 trial) were as follows: S aureus clinical cultures (current trial: 48.1% [95% CI, 35.6%-60.1%]; 2009-2011 trial: 58.8% [95% CI, 47.5%-70.7%]) and bloodstream infection rates (current trial: 70.4% [95% CI, 62.9%-77.8%]; 2009-2011 trial: 60.1% [95% CI, 49.1%-70.7%]).

Conclusions and Relevance

Nasal iodophor antiseptic did not meet criteria to be considered noninferior to nasal mupirocin antibiotic for the outcome of S aureus clinical cultures in adult ICU patients in the context of daily CHG bathing. In addition, the results were consistent with nasal iodophor being inferior to nasal mupirocin.

Trial Registration

ClinicalTrials.gov Identifier: NCT03140423.

Complications following completion lymphadenectomy versus therapeutic lymphadenectomy for melanoma - A systematic review of the literature

PURPOSE

Completion lymph node dissection (CLND) following a positive sentinel lymph node biopsy (SLNB) has been reported to be less morbid than lymphadenectomy for palpable disease (therapeutic lymph node dissection; TLND). The reporting of morbidity data can be heterogeneous, and hence no 'average' surgical complication rates of these procedures has been reported. This review aims to determine complications rates to inform patients undergoing surgery for metastatic melanoma.

METHODS

A systematic review of English-language literature from 2000 to 2017, reporting morbidity information about CLND and TLND for melanoma, was performed. The methodological quality of the included studies was performed using the methodological index for non-randomised studies (MINORS) instrument and Detsky score. Pooled proportions of post-operative complications were constructed using a random effects statistical model.

RESULTS

After application of inclusion and exclusion criteria, 18 articles progressed to the final analysis. In relation to TLND (1627 patients), the overall incidence of surgical complications was 39.3% (95% CI 32.6-46.2); including wound infection/breakdown 25.4% (95% CI: 20.9-30.3); lymphoedema 20.9% (95% CI: 13.8-29.1); and seroma 20.4% (95% CI: 15.9-25.2). For CLND (1929 patients), the overall incidence of surgical complications was 37.2% (95% CI 27.6-47.4); including wound infection/breakdown 21.6% (95% CI: 13.8-30.6); lymphoedema 18% (95% CI: 12.5-24.2); and seroma 17.9% (95% CI: 10.3-27). The complication rate was marginally lower for CLND but not to statistical significance.

DISCUSSION

This study provides information about the incidence of complications after CLND and TLND. It can be used to counsel patients about the procedures and it sets a benchmark against which surgeons can audit their practice.

A bundled approach to reduce methicillin-resistant Staphylococcus aureus infections in a system of community hospitals

Methicillin-resistant Staphylococcus aureus (MRSA) infections pose a significant challenge to U.S. healthcare facilities, but there has been limited study of initiatives to reduce infection and increase patient safety in community hospitals. To address this need, a multifaceted program for MRSA infection prevention was developed for implementation in 159 acute care facilities. This program featured five distinct tools-active MRSA surveillance of high-risk patients, enhanced barrier precautions, compulsive hand hygiene, disinfection and cleaning, and executive champions and patient empowerment-and was implemented during 1Q-2Q 2007. Postintervention (3Q 2007-2Q 2008), 10.2% of patients with high-risk for infection or complications due to MRSA had nasal colonization. Volume of disposable gown and alcohol-based hand sanitizer use increased substantially following program implementation. Self-reported rates, based on NHSN definitions, of healthcare-associated central line-associated bloodstream infections and ventilator-associated pneumonia due to MRSA decreased 39% (p < .001) and 54% (p < .001), respectively. Infection rates continued to decrease during the follow-up period (1Q-4Q 2009). This sustained improvement demonstrates that reducing healthcare-associated MRSA infections in a large number of diverse facilities is possible and that a "bundled" approach that translates science into clinical and executive performance expectations may aid in overcoming traditional barriers to implementation.

Holmium laser enucleation for prostate adenoma greater than 100 gm.: comparison to open prostatectomy

PURPOSE

Options for treatment of large (greater than 100 gm.) prostatic adenomas have until now been limited to open surgery or transurethral resection by skilled resectionists. Considerable blood loss, morbidity, extended hospital stay and prolonged recovery occur with open surgery for large prostatic adenomas. Endoscopic surgery for benign prostatic hyperplasia has evolved during the last decade to offer the patient and surgeon significant advantages of transurethral removal of prostatic adenomas. Holmium laser enucleation of the prostate with transurethral tissue morcellation provides significant reductions in morbidity, bleeding and hospital stay for patients with large prostate adenomas.

MATERIALS AND METHODS

A retrospective review of data on 10 cases of holmium laser enucleation and 10 open prostatectomies for greater than 100 gm. prostatic adenomas was performed from 1998 to 1999 at our institution. Patient demographics, indication for surgery, preoperative and postoperative American Urological Association (AUA) symptom scores, operating time, serum hemoglobin, resected prostatic weight, pathological diagnosis, length of stay and complications were compared.

RESULTS

Patient age, indications for surgery (retention, failed medical therapy, high post-void residual, bladder calculi, bladder diverticula and azotemia) and preoperative AUA symptom scores were similar in both groups. Postoperative AUA symptom scores were significantly decreased (p <0.004) in both groups. Operating times were not significantly different. Serum sodium was unchanged by holmium laser enucleation (not significant), and postoperative hemoglobin was not significantly reduced in the holmium laser enucleation group but decreased significantly in the open prostatectomy group (mean decrease 2.9 +/- 0.7 gm., p = 0.0003). Resected weight was greater in the holmium laser enucleation group (151 versus 106 gm., p = 0.07). Length of stay was significantly shorter in the holmium laser enucleation group (2.1 versus 6.1 days, p <0.001). Complications in the holmium laser enucleation group included stress urinary incontinence in 4 cases, prostatic perforation in 1 and urinary retention in 1. No patient treated with holmium laser enucleation was discharged home with an indwelling catheter. Complications in the open prostatectomy group included bladder neck contractures in 2 cases, stress incontinence in 1 and urge incontinence in 1. All patients treated with open prostatectomy were discharged home with an indwelling catheter.

CONCLUSIONS

Holmium laser enucleation is an effective, safe procedure for large prostatic adenomas with significantly lower morbidity, catheterization duration and length of stay. Performing holmium laser enucleation for large adenomas requires experience. Stress incontinence was seen frequently with laser but was short-term and self-limited. Holmium laser enucleation is a new procedure, and as experience and expertise increase, it may become an attractive alternative to open prostatectomy for patients with large prostate adenomas.

Fournier's gangrene in a modern surgical setting: improved survival with aggressive management

OBJECTIVE

To examine the outcome of 23 consecutive patients with Fournier's gangrene.

PATIENTS AND METHODS

Patients' charts were reviewed retrospectively from all those treated for Fournier's gangrene between July 1994 and July 1997 at the UCLA affiliated hospitals.

RESULTS

Twenty-three patients were identified (mean age 51.7 years, range 13-71). The aetiologies included perirectal abscess (43%), urethral stricture (30%), scrotal abscess (21%) and unknown (4%). Predisposing factors included diabetes mellitus (43%), steroids or chemotherapy (21%), alcohol abuse (43%), malignancy (26%) and radiation therapy (9%). All 23 patients initially received wide debridement and placement of a percutaneous suprapubic tube. At the time of the first surgery, total scrotectomy was required in all, colostomy in 17% and penectomy in 4%. An additional 35% required eventual colostomy and an additional 9% required a penectomy. Patients underwent repeat debridement a mean of 2.5 times; the overall survival was 96%.

CONCLUSION

Survival can be improved in patients with Fournier's gangrene by combining aggressive surgical and medical management. The keys to successful outcome included a high index of suspicion, prompt fluid resuscitation, rapid initiation of broad-spectrum antibiotics, a multidisciplinary approach, early surgical intervention with radical debridement, haemodynamic support in an intensive care setting, and frequent repeat operative debridement.

Effects of long-term oral administration of L-arginine on the rat erectile response

PURPOSE

Nitric oxide (NO), the neurotransmitter responsible for mediating penile erection in the rat, is synthesized from L arginine by nitric oxide synthase (NOS) in a reaction blocked by L-NAME (N-omega-nitro-L-arginine methyl ester). To determine whether dietary supplementation of L-arginine can stimulate penile erection and whether ancillary pathways for penile erection may exist, a series of experiments were conducted in the Fischer 344 rat.

MATERIALS AND METHODS

Adult male (5 month old) and aged (20 month old) rats were fed L-arginine (2.25%) and L-NAME (0.7%) dissolved in tap water for 8 weeks. Animals (n = 6) underwent electrical field stimulation (EFS) of the cavernosal nerve to induce erection and both maximal intracavernosal pressure (MIP) and mean arterial pressure (MAP, mm. Hg +/- SEM) were measured. Tissue and serum levels of L-arginine were measured by an automated amino acid analyzer. Penile eNOS (endothelial) and nNOS (neuronal) content were measured by western blot densitometry. Total penile NOS enzyme activity was measured by the L-arginine to L-citrulline conversion assay.

RESULTS

The L-arginine fed animals demonstrated a significant increase in EFS-induced MIP when compared to the controls in both the adult (104 +/- 4 vs. 86 +/- 6, p = 0.04) and aged (87 +/- 5 vs. 66 +/- 4, p = 0.02) animals, without changes in MAP. L-NAME virtually abolished the MIP in adult rats (8 +/- 3, p < 0.0001), while increasing the MAP (186 +/- 8, p < 0.0001). Serum and penile tissue levels of L-arginine were increased by 64-148% in all groups compared to control animals. Penile eNOS and nNOS content remained unchanged in control and treated animals. Penile NOS activity was increased nearly 100% in the L-arginine treated groups vs. controls.

CONCLUSIONS

Long-term oral administration of supra-physiologic doses of L-arginine improves the erectile response in the aging rat. We postulate that L-arginine in the penis may be a substrate-limiting factor for NOS activity and that L-arginine may up-regulate penile NOS activity but not its expression. The blockade of penile erection by EFS with L NAME suggests that if ancillary corporeal vasodilator mechanisms develop, a basal level of NO synthesis is still required for activation and relaxation of the corporeal smooth muscle. These data support the possible use of dietary supplements for treatment of erectile dysfunction.

Effect of aerobic and anaerobic environments on antistaphylococcal activities of five fluoroquinolones

A previously established in vitro pharmacodynamic system was used to evaluate the antistaphylococcal activities of five fluoroquinolones under both aerobic and anaerobic conditions. Staphylococcus aureus ATCC 29213 was exposed to a 5-micrograms/ml concentration of each of the following fluoroquinolones: ciprofloxacin, ofloxacin, temafloxacin, sparfloxacin, and clinafloxacin. Terminal elimination half-lives of 4, 6, 8, 8, and 13 h were simulated for the respective drugs. Each fluoroquinolone was bactericidal under both aerobic and anaerobic conditions. However, the bactericidal activity of each fluoroquinolone was delayed by anaerobiosis. This difference in fluoroquinolone activity under aerobic and anaerobic conditions could not be attributed to any particular parameter or physiochemical property but was most likely caused by a combination of factors (e.g., variations in hydrophobicity, intracellular pH, antibiotic concentration, and structure-activity relationships). Fluoroquinolone uptake studies were also performed to investigate the possibility of active, energy-dependent transport mechanisms in S. aureus ATCC 29213. Uptake studies indicated that active efflux does occur in S. aureus ATCC 29213.

Bactericidal action of gentamicin against enterococci that are sensitive, or exhibit low- or high-level resistance to gentamicin

Treatment of serious enterococcal infection involves the use of penicillin-aminoglycoside combination therapy if the aminoglycoside minimum inhibitory concentration (MIC) is < or = 2000 micrograms/ml, and the organism is susceptible to penicillin or ampicillin. We evaluated killing of 15 enterococci that differ in their susceptibility to gentamicin using time-kill studies at different gentamicin concentrations. Sensitive strains had a uniform population killed by gentamicin concentrations equal to or above the MIC. Low-level resistant strains (MIC > or = 8 but < or = 2000 micrograms/ml of gentamicin) had a diverse population with large numbers of cells killed at one-half the MIC, while the highly resistant strains (MIC > 2000 micrograms/ml) showed no killing by any concentration of gentamicin.

Evaluation of activity of temafloxacin against Bacteroides fragilis by an in vitro pharmacodynamic system

An in vitro pharmacodynamic system has been successfully adapted to simulate in vivo antimicrobial pharmacokinetics under anaerobic conditions. This system was used to perform time-kill kinetic studies which were designed to compare the activity of temafloxacin to ciprofloxacin and cefotetan against two strains of Bacteroides fragilis (ATCC 25285 and ATCC 23745). All experiments were performed as single-dose, 24-h, duplicate runs. Starting bacterial inocula of 10(7) CFU/ml were exposed to starting antimicrobial concentrations of 5 micrograms of temafloxacin per ml, 5 micrograms of ciprofloxacin per ml, and 100 micrograms of cefotetan per ml. Terminal half-lives of 8, 4, and 4 h were simulated for each antimicrobial agent. Temafloxacin was rapidly bactericidal against B. fragilis. Ciprofloxacin was not bactericidal (< 3 log10 unit decline in bacterial numbers) to either strain of B. fragilis. Cefotetan was bactericidal (> or = 3 log10 unit decline in bacterial numbers) to each strain but killed at a slower rate than temafloxacin. Times to 3 log10 unit declines of strain ATCC 25285 were 2, 4, and > 24 h, whereas those of strain ATCC 23745 were 4, 4, and > 24 h for temafloxacin, cefotetan, and ciprofloxacin, respectively. Total logarithmic declines of strain ATCC 25285 were > 4.5, > 4.5, and 2.9 log10 CFU/ml, whereas those of strain ATCC 23745 were 4.1, > 4.5, and 1.2 log10 CFU/ml for each drug, respectively. These and other studies demonstrated that temafloxacin showed potential as an agent that could have been further developed for use in the treatment of anaerobic infections. However, the drug was removed from the market by its manufacturer because of toxicity issues. Although the release of newer fluoroquinolones that possess significant activity against anaerobic bacteria does not appear imminent, the time-kill studies performed in this study demonstrate that further research is warranted in the development of fluoroquinolones which possess significant antianaerobic activity.

Clostridium difficile colonization in residents of long-term care facilities: prevalence and risk factors

OBJECTIVE

To determine the period prevalence of Clostridium difficile disease and asymptomatic carriage in the residents of long-term care facilities (LTCF) and to characterize the risk factors for colonization or associated disease.

DESIGN

Period prevalence survey.

SETTING

Two long-term care facilities in St. Paul, MN.

PARTICIPANTS

Specimens were collected from 225 LTCF residents.

MEASUREMENTS

The dependent variable was the culture result for C. difficile, which was isolated and identified using selective culture media and a commercial anaerobe identification kit. Tissue culture assay was used to detect the ability of each C. difficile isolate to produce toxin. Independent variables (including gender, age, race, current medical diagnoses, severity of underlying disease, case mix, current clinical symptoms, current medications, antibiotic use within 4 weeks prior to specimen procurement, and other pertinent history) were obtained from the current medical record of each participant.

RESULTS

Of 225 stool cultures that were obtained, 16 (7.1%) were positive for C. difficile. None of the residents with a positive culture was symptomatic. History of nosocomial infection and the use of antibiotics in general, cephalosporins, trimethoprim/sulfamethoxazole (TMP/SMX), and histamine-2 blockers were significantly associated with positive C. difficile culture (P < or = 0.05) by univariate analyses. Trends towards significance (0.05 < 0.10) were noted for narcotic use, previous hospitalization, LTCF, and non-insulin-dependent diabetes mellitus. Logistic regression analysis revealed significant, independent predictors of positive culture: antibiotic use in general (P = 0.028; relative risk = 3.31), histamine-2 antagonist use (P = 0.038; relative risk = 3.27), cephalosporin use (P = 0.038; relative risk = 4.66), and TMP/SMX use (P = 0.007; relative risk = 8.45).

CONCLUSIONS

The use of antibiotics, particularly cephalosporins and TMP/SMX, is a significant risk factor for asymptomatic carriage of C. difficile in long-term care facilities. The use of H-2 blockers was also a significant risk factor for carriage; however, this finding has not been reported previously and should be confirmed by independent studies. These medications should be used judiciously in the LTCF population. When diarrheal diseases are encountered in LTCF residents, a high index of suspicion for C. difficile infection should be maintained and the appropriate diagnostic and therapeutic measures taken.

Effect of yogurt on clindamycin-induced Clostridium difficile colitis in hamsters

Yogurt exhibits in vitro bactericidal activity against a variety of pathogenic microorganisms, including Clostridium difficile. In the present studies, we tested whether yogurt ingestion could prevent or ameliorate antibiotic associated colitis in the clindamycin-treated hamster model. Male golden Syrian hamsters were given 5 mg/kg clindamycin subcutaneously 24 hr before and 6 hr following inoculation with 0.5 ml of less than 10, 10(3), 10(5), or 10(6) CFU/ml of C. difficile. Hamsters in the control group ingested chow and water ad libitum, whereas the experimental group ingested chow and a 1:1 (v/v) mixture of yogurt and water ad libitum, beginning 24 hr before the first injection of clindamycin and continuing throughout the course of the study. Animals were monitored for colonization with C. difficile, pathological evidence of colitis, and death. Mortality was 100% in yogurt-treated animals, and all animals showed histological changes of severe colitis. Fecal and intestinal segment cultures were positive for C. difficile in all animals. Thus, in the hamster model, we found no evidence to support the possible efficacy of yogurt in the prevention of C. difficile colitis.

Human infections associated with Bordetella bronchiseptica

This study examines the potential of Bordetella bronchiseptica to act as a human pathogen. After encountering two patients from whom B. bronchiseptica was isolated, we searched the literature and found 23 reports in which a human infection was reported in association with B. bronchiseptica. As a basis for evaluating these cases, we summarize the literature about the current microbiological status of B. bronchiseptica, the pathology and pathogenic mechanisms associated with the microorganism, and the likelihood of it acting as a commensal or colonizer. From this review we conclude that B. bronchiseptica has been rarely isolated from humans despite their considerable exposure to animal sources. Evidence suggests that B. bronchiseptica may be rarely encountered as a commensal or colonizer of the respiratory tract of humans and rarely in association with infection. When found as a probable pathogen, most infections have been respiratory tract in origin and have occurred in severely compromised hosts.

A general ampC active site oligonucleotide probe for gram-negative rods

We have developed a 33 mer probe that hybridizes to the serine active site of the chromosomal ampC beta-lactamase gene of Pseudomonas aeruginosa and the Enterobacteriaceae. We tested this probe against a variety of Enterobacteriaceae, and a series of 23 P. aeruginosa by dot-blots and selected Southern blots. This probe is an alternative or supplement to enzyme studies for characterizing the class of a Gram-negative rod's beta-lactamase and is a useful tool for studies of Pseudomonas beta-lactamase regulation.

Antibacterial activity of cefoperazone and cefoperazone plus sulbactam in a neutropenic site model

Efficacy of cefoperazone versus cefoperazone plus sulbactam was studied in a rabbit neutropenic site infection model against a broad range of clinical isolates including six isolates each of staphylococci, enterococci, pneumococci, Enterobacteriaceae, and Pseudomonas aeruginosa. Therapy of cefoperazone plus sulbactam demonstrated enhanced efficacy against the staphylococci, pseudomonads, and Enterobacteriaceae. The activity of cefoperazone against enterococci and pneumococci was not enhanced or inhibited by the addition of sulbactam. Increased concentrations of cefoperazone found at the infection sites when sulbactam was added to the therapeutic regimen indicates that sulbactam provided a protection to cefoperazone from beta-lactamases produced by staphylococci and Enterobacteriaceae. The combination improved the efficacy of cefoperazone in this animal model.

Treatment evaluation of experimental staphylococcal infections: comparison of beta-lactam, lipopeptide, and glycopeptide antimicrobial therapy

LY 146032, teicoplanin, vancomycin, oxacillin, cephalothin, cefamandole, ampicillin plus sulbactam, and cefoperazone plus sulbactam were studied against six isolates of staphylococci (including both Staphylococcus aureus and coagulase negative staphylococci) using in vivo and in vitro methods. In vitro susceptibility measurements demonstrated that all six isolates were sensitive to LY 146032 and vancomycin and that five of six isolates were sensitive to tiecoplanin, cefamandole, ampicillin plus sulbactam, and cefoperazone plus sulbactam. Comparison of antimicrobial therapy in an in vivo rabbit model demonstrated that cefoperazone plus sulbactam was active against the greatest number of isolates (five of six) based on a reduction of greater than or equal to 5.0 log10 colony forming units per milliliter (CFU/ml) from growth control at the end of the animal treatment study. Vancomycin and oxacillin were equal in achieving reductions of greater than or equal to 5.0 log10 CFU/ml in four of the six isolates. Comparing each isolate's in vivo outcome to in vitro data shows that in vitro susceptibility tests overpredict the sensitivity of these six isolates to LY 146032 and vancomycin, are variable for teicoplanin, cefamandole, ampicillin plus sulbactam, and cefoperazone plus sulbactam, and underpredict for oxacillin.

In vitro activity of LY 264826 compared with that of vancomycin against 100 clinical isolates each of methicillin-resistant Staphylococcus aureus and Clostridium difficile

The in vitro activity of LY 264826, a new glycopeptide antibiotic, was compared with that of vancomycin against 100 strains each of methicillin-resistant Staphylococcus aureus and Clostridium difficile. LY 264826 was more active, by weight, than vancomycin against the isolates tested. The human serum protein binding of LY 264826 was 15.3% (range, 9.8 to 21.8%).

In vitro antibacterial effect of yogurt on Escherichia coli

We investigated the bactericidal and bacteriostatic effects of yogurt on three strains of Escherichia coli: human toxigenic (078:H11), rabbit pathogenic (RDEC-1) and rabbit nonpathogenic [015:K14(L):H4]. Approximately 10(6) organisms were incubated in yogurt, milk, broth, and modifications of these materials. Aliquots were removed at various intervals and plated on MacConkey's agar for enumeration of E. coli. Yogurt was bactericidal (at least 5 log10 reduction in bacterial counts) to all three strains of E. coli with less than 10 CFU/ml remaining by 9 hr. In contrast, all three strains replicated rapidly in milk and broth, reaching maximum concentrations by 9 hr. The E. coli strains survived and multiplied in milk acidified to the same pH as the yogurt. Yogurt (native pH 4.1-4.4) in which the pH was brought up to and maintained at pH 5.5 or pH 7 for 8 hr was not bactericidal to E. coli. Heat-treated yogurt and the filtered supernatant of centrifuged yogurt (both containing no yogurt bacteria) were only bacteriostatic. We conclude that both live yogurt bacteria and a pH near 4.5 are necessary for the bactericidal activity of yogurt. The possibility that yogurt ingestion could protect against infection via other foods contaminated with pathogenic E. coli merits further in vivo investigation.

Comparative efficacy of cefoperazone, cefoperazone plus sulbactam, ciprofloxacin, clindamycin, metronidazole, and penicillin G against anaerobic bacteria in an animal model

Treatment efficacy of various antimicrobial regimens against anaerobes was studied in semipermeable chambers simulating a closed-space, locally neutropenic infection site in rabbits. Bacteroides fragilis, Bacteroides melaninogenicus, Clostridium perfringens, and Peptostreptococcus anaerobius were inoculated (at a mean of 5.3 log10 CFU/ml in prereduced pooled rabbit serum) into the chambers (one isolate per chamber) in triplicate. Antimicrobial therapy consisted of cefoperazone, cefoperazone plus sulbactam, ciprofloxacin, clindamycin, metronidazole (against the gram-negative anaerobes), or penicillin G (against the gram-positive anaerobes), beginning 4 hours after organism inoculation and continuing every 6 hours for 16 doses. With the use of anaerobic techniques for specimen acquisition, transport, and culture, quantitative bacterial findings were measured at the start of therapy and at various time points thereafter. Antibiotic concentrations were measured in blood and chamber fluid by liquid chromatography or bioassay methods. At the end of the study in vivo organisms were reduced by at least 3 log10 CFU/ml from drug-free growth control chambers by all the antimicrobial regimens tested except for cefoperazone against B. fragilis and ciprofloxacin against the three isolates tested. The addition of sulbactam to cefoperazone inhibited B. fragilis beta-lactamase activity and eradicated B. fragilis in vivo. In vivo results with this model confirmed in vitro susceptibilities of all tested antimicrobials except ciprofloxacin and should provide useful indications of the potential clinical efficacy of other new agents against anaerobes.

Influence of protein binding on therapeutic efficacy of cefoperazone

The effect of protein binding of cefoperazone (89.3% bound to rabbit serum) on antibacterial activity in serum was tested in a model that simulated a closed-space infection in a neutropenic host. Four gram-negative bacilli were tested in the model with cefoperazone doses of 20 and 200 mg/kg administered intramuscularly every 6 h for 16 doses. Cefoperazone efficacy was measured at 92 h by determining the log10 decrease in bacterial count from that of the control for five paired studies with three isolates. A significantly better response was demonstrated when the free (non-protein-bound) drug concentration exceeded the MICs and MBCs for the infecting microorganisms at the infection site at all times (P less than 0.005). This supports the concept that free (unbound) drug is the active component in treating bacterial infections.

Cervical spinal cord injury--a public catastrophe

Cervical spine cord injuries continue to be a major cause of death and disability for trauma victims. Motor vehicle trauma results in 500 to 650 quadriplegic patients per year. Most of the patients are cared for at Level I trauma centers which may not have a dedicated rehabilitation facility. Long-term rehabilitation, nursing care, and financial support remain difficult areas in the overall management of these injuries. Seventy-one cervical spine fracture patients were admitted to this medical center over a 2-year period. Twenty-two patients had a neurologic injury, 15 quadriplegic patients, and seven with incomplete deficits. Vehicular trauma was the etiology in 14 injuries; gunshot wounds in five; falls in three. Twelve of these 22 patients had associated injuries, including chest and abdominal trauma. Prolonged stays in the intensive care unit were common (avg. = 13.5 days). Bronchoscopy (8/22 patients) and aggressive pulmonary care were constantly needed. Six patients died in the intensive care unit. The average hospital stay of the survivors was 45 days. Three of the 16 surviving patients were ventilator dependent at the time of discharge. Ten patients were discharged to a rehabilitation center, one to a nursing home, and five went home (one on a ventilator). The total hospital charges were $1,250,000. No financial resources were available for five of the 16 surviving patients. Four patients had resources which covered less than 50% of the total charges. Average hospital charges for survivors were $50,370. Maximum reimbursement using all outlier days under DRG 5 would be $12,385. The financial support of initial hospitalization, rehabilitation, and nursing care for these quadriplegic patients is a serious national health care issue.

In vivo and in vitro activity of ciprofloxacin plus azlocillin against 12 streptococcal isolates in a neutropenic site model

Closed-space neutropenic infection sites were simulated in rabbits by subcutaneous semipermeable chambers that were inoculated with 5 X 10(4) CFU/ml of various strains of Streptococcus pneumoniae, Streptococcus faecalis, and Streptococcus avium. Four hours after inoculation, treatment was begun with ciprofloxacin, 10 or 30 mg/kg, azlocillin, 100 mg/kg, amikacin, 15 mg/kg, procaine penicillin G, 300 U/dose, or gentamicin, 2 mg/kg, alone and in two-drug combinations. Antimicrobials were given intramuscularly every 6 hr for 16 doses. Extravascular chambers were sampled throughout the treatment course for bacterial counts and antimicrobial concentration. In vivo results were compared to in vitro tests of inhibition, killing, and synergism. Ciprofloxacin alone had little effect on the animal infection sites. Azlocillin alone reduced, in vivo, eight of 12 isolates greater than or equal to 5 log10 CFU/ml by 92 hr as compared to control. Azlocillin plus ciprofloxacin reduced all 12 isolates greater than or equal to 5 log10 CFU/ml by 92 hr, whereas amikacin plus azlocillin reduced only three and penicillin plus gentamicin only one of the six group D streptococcal isolates greater than or equal to 5 log10 CFU/ml.

Evaluation of ciprofloxacin's synergism with other agents by multiple in vitro methods

The efficacies of ciprofloxacin, ceftizoxime, azlocillin, mezlocillin, and amikacin (minimal inhibitory concentration and minimal bactericidal concentration) against six Pseudomonas aeruginosa, six Enterobacteriaceae, and six group D streptococcal strains were evaluated using both agar and broth susceptibility methods, two inoculum sizes (5.7 log10 colony-forming units (cfu)/ml and 7.7 log10 cfu/ml), and aerobic and anaerobic incubation conditions. The results showed agreement between broth and agar methods of susceptibility determination; inoculum effects with beta-lactam antimicrobials; and decreased susceptibility to amikacin under anaerobiasis. Ciprofloxacin combined with azlocillin, ceftizoxime, or aminoglycosides in broth microdilution checkerboards against 100 gram-negative bacilli and gram-positive cocci demonstrated that ciprofloxacin combined with azlocillin or ceftizoxime was synergistic against at least 50 percent of P. aeruginosa and Serratia marcescens isolates and that ciprofloxacin combined with amikacin was synergistic against at least 50 percent of S. marcescens and Staphylococcus aureus isolates. Ciprofloxacin and azlocillin in combination were evaluated by microdilution checkerboard, agar dilution, and broth macrodilution time-kill methods at two inoculum sizes to assess antibacterial activity. Comparison between in vitro combination methods showed the following: the presence or absence of checkerboard synergism (as defined by the fractional inhibitory concentration index and the fractional bactericidal concentration index) with ciprofloxacin and azlocillin did not correlate with time-kill results; and good agreement between methods when comparing broth macrodilution time-kill (3 log10 cfu/ml or more decrease) with antimicrobial combinations at a single concentration in both agar and microdilution broth for ciprofloxacin and azlocillin. Rabbit studies using subcutaneous dialysis membrane chambers inoculated with six P. aeruginosa, six Enterobacteriaceae, and six group D streptococcal strains were performed using ciprofloxacin, azlocillin, ceftizoxime, and amikacin alone and in combination as therapy. In vitro testing of antibiotic combinations that provided the best prediction of in vivo outcome were combination antibacterial activity (3 log10 cfu/ml or more decrease) at 24 hours using either broth macrodilution time-kill or antimicrobial combinations at a single concentration in either agar or broth (microdilution). For the most efficacious in vivo combination, ciprofloxacin plus azlocillin, there was in vitro correlation with in vivo outcome for 17 of 18 isolates.

Ceftazidime and amikacin alone and in combination against Pseudomonas aeruginosa and Enterobacteriaceae

The efficacy of ceftazidime alone and combined with amikacin was studied in a rabbit model simulating closed-space infections at locally neutropenic sites. Six strains of Pseudomonas aeruginosa, and six Enterobacteriaceae (two strains each of Klebsiella pneumoniae and Serratia marcescens and one strain each of Escherichia coli and Citrobacter freundii) in pooled rabbit serum were each inoculated into separate subcutaneous semipermeable chambers. Intramuscular antibiotic therapy was begun 4 hr later with ceftazidime (50 mg/kg) alone and combined with amikacin (15 mg/kg) for Enterobacteriaceae or ceftazidime (100 mg/kg) alone and combined with amikacin (15 mg/kg) for pseudomonads every 6 hr for 16 doses. Amikacin alone was ineffective for all 12 strains. Ceftazidime alone was successful (greater than or equal to 5.5 log10 colony forming units (CFU)/ml decrease from drug-free control) in eliminating five of six Enterobacteriaceae but was not successful against any of the pseudomonads. Ceftazidime plus amikacin was successful against the same five of six Enterobacteriaceae and five of six pseudomonads. The best in vitro tests for the prediction of in vivo outcome were high inoculum (greater than or equal to 7 log10 CFU/ml) susceptibility, checkerboard synergism testing, and conventional inoculum time-kill rates at concentrations of antimicrobials simulating extravascular levels obtained in vivo.

Ciprofloxacin, azlocillin, ceftizoxime and amikacin alone and in combination against gram-negative bacilli in an infected chamber model

Ciprofloxacin, azlocillin, ceftizoxime, and amikacin were studied alone and in combination against six Enterobacteriaceae and six strains of Pseudomonas aeruginosa in an infected chamber model in rabbits simulating a closed space infection. In-vivo results were compared with in-vitro tests of inhibition, killing and synergy. Ciprofloxacin was the most effective single agent, with efficacy against five of the six Enterobacteriaceae when used in low doses, and two of the six pseudomonads when used in high doses. The development of in-vitro resistance to ciprofloxacin was observed during therapy in strains which failed to be eradicated. Ciprofloxacin and azlocillin together was the most effective regimen, with efficacy against eleven of the twelve strains. Synergy, as determined by chequerboard testing, did not correlate with in-vivo outcome. Unlike mezlocillin, azlocillin, ceftizoxime or amikacin, MIC testing of ciprofloxacin was predictive of in-vivo success.

In vitro activity of ciprofloxacin combined with azlocillin

A ciprofloxacin plus azlocillin broth microdilution checkerboard was evaluated against 125 aerobic gram-negative and gram-positive bacteria. Synergism (sigma FIC less than or equal to 0.5) occurred among 56% of Pseudomonas aeruginosa, 30% of Acinetobacter species, and 40% of Staphylococcus aureus studied. Antagonism (sigma FIC greater than or equal to 2) was present in less than 1% of the organisms.

Mezlocillin, ceftizoxime, and amikacin alone and in combination against six Enterobacteriaceae in a neutropenic site in rabbits

Closed-space, locally neutropaenic infection sites were simulated in rabbits by implanting subcutaneous semipermeable chambers inoculated with 5 X 10(4) cfu/ml of Escherichia coli (one strain), Citrobacter diversus (one strain), Klebsiella pneumoniae (two strains) or Serratia marcescens (two strains). Four hours after inoculation, treatment was begun with amikacin (15 mg/kg), mezlocillin (100 mg/kg), or ceftizoxime (50 mg/kg) alone or in two-drug combinations. Antibiotics were given intramuscularly every 6 h for 16 doses. Chambers were sampled for bacterial counts at the start of therapy, and 20, 44, and 92 h thereafter. Blood and chamber antibiotic levels were determined during the treatment course. In-vivo results were compared to in-vitro tests of inhibition, killing and synergism. Ceftizoxime alone was successful in vivo (greater than 6 log reduction in count) against the three strains of klebsiella and citrobacter, mezlocillin against one serratia strain, and amikacin alone against none of the strains. The best in-vitro correlation was with the minimum inhibitory concentration (MIC) at a high (10(8] inoculum for the beta-lactams and with the anaerobic MIC for amikacin. Among combinations, amikacin plus mezlocillin alone was successful against the three strains of klebsiella and serratia, but neither amikacin nor mezlocillin added to ceftizoxime were more successful than ceftizoxime alone. In-vitro chequerboard synergism was not predictive of in-vivo success. Mezlocillin alone was inactivated in vivo by all the strains except Ser. marcescens, and the E. coli strain inactivated both mezlocillin and ceftizoxime alone and in combination.

Evaluation of new blood culture processing systems

The Antimicrobial Removal Device (ARD; Marion Scientific) was evaluated in vitro with simulated blood culture samples in fresh blood and clinically with samples from potentially septic patients to test its ability to remove antimicrobial agents and recover bacteria from blood culture specimens containing these drugs. In simulated specimens, the ARD was evaluated for adverse affects on microorganisms as well as compared with lysis-centrifugation (Isolator; Du Pont Co.), biphasic brain heart infusion bottles, and tryptic soy broth bottles for antimicrobial inactivation and organism recovery. There was no adverse effect of the ARD on organisms during a 4-h test period. The ARD was the only system to actually inactivate antimicrobial agents and removed greater than 99.2% of all antimicrobial agents tested from spiked and clinical specimens. Overall, with simulated blood culture specimens, the ARD recovered 90% of bacteria spiked into fresh blood containing antimicrobial agents, Isolator recovered 73%, biphasic brain heart infusion bottles recovered 31%, and tryptic soy broth bottles recovered 24%. In the clinical study, 43 of 86 clinically significant isolates were recovered only by ARD-assisted processing, 6 were recovered only by conventional processing, and 37 were recovered by both methods (the advantage of ARD processing over conventional processing in the clinical study was significant at P less than 0.001). Both clinical and simulated specimens demonstrated the ARD-associated blood culture processing to be the most efficient method for the isolation of microorganisms from specimens containing antimicrobial agents.

MBCs for Staphylococcus aureus as determined by macrodilution and microdilution techniques

MBC testing of clindamycin, methicillin, cephalothin, gentamicin, and vancomycin with 67 clinical isolates of Staphylococcus aureus was examined by both standard macrodilution tubes and commercial microdilution trays. Standard macrodilution failed to give reproducible (99.9% killing) MBC results, even when a strictly defined protocol was followed. Continuous shaking during incubation resulted in regrowth of more colonies than did stationary incubation. Vortexing of incubated tubes before subculture resulted in regrowth of more colonies than did careful transfer of the contents to sterile tubes before vortexing and subculture. No significant difference in MBCs was demonstrated by the use of log-phase versus stationary-phase inocula. Use of the multiprong inoculator for subculture from commercial microdilution trays was unsatisfactory because, although antibiotics evaluated were inactivated by subculture to a pH 5.5 agar plate coated with a beta-lactamase solution, the volume of broth transferred by the prongs was small and inconsistent, ranging from 0 to 3 microliter. Subcultures of commercial microdilution panels with a 1-microliter loop, 10-microliter pipette, and 100-microliter pipette were also evaluated. Results of MBC testing were most reproducible when the entire 100-microliter volume was aspirated from commercial microdilution wells after stirring and the contents of each well were spread over a separate sheep blood agar plate.

In vitro activities of ureidopenicillins alone and in combination with amikacin and three cephalosporin antibiotics

The MIC and MBC activity of mezlocillin alone and in combination with two concentrations of ceftizoxime, moxalactam, and amikacin and a single concentration of cefoxitin was studied in a broth microdilution partial checkerboard against 472 strains of aerobic gram-negative and gram-positive bacteria. Azlocillin was tested alone and in the same combinations against Pseudomonas aeruginosa. Of the gram-negative bacilli tested, 38% were gentamicin resistant. Antagonism (less than or equal to a fourfold ureidopenicillin MIC increase) was observed frequently with combinations of ureidopenicillins plus cefoxitin and sporadically with ureidopenicillins plus ceftizoxime or moxalactam. Partial synergism (less than or equal to a fourfold ureidopenicillin MIC decrease) was evident with both combinations of ureidopenicillins plus amikacin and ureidopenicillins plus ceftizoxime or moxalactam, the percentage being dependent upon the individual species and combinations.

In vitro activities of amphotericin B in combination with four antifungal agents and rifampin against Aspergillus spp

Strains of Aspergillus fumigatus, Aspergillus flavus, and Aspergillus niger were tested for in vitro susceptibility with a microtiter plate system in buffered yeast-nitrogen base and in buffered minimal essential medium. Isolates were tested against amphotericin B, flucytosine, rifampin, ketoconazole, ICI 153,066, and Bay n 7133 and against combinations of amphotericin B with each of the other five drugs. Combinations of amphotericin B and rifampin were the most active against all three species of Aspergillus. Flucytosine combined with amphotericin B produced little or no reduction of the MICs at which 90% of the strains were inhibited compared with amphotericin B alone. With one exception, the addition of ketoconazole, ICI 153,066, or Bay n 7133 to amphotericin B did not consistently alter the MICs. The addition of ICI 153,066 markedly increased the MICs of amphotericin B against the A. flavus isolates in both media. When the azoles were tested alone, Bay n 7133 was the most active against A. fumigatus, but was two- to fivefold less active against A. flavus. Ketoconazole was the most active azole against A. flavus.

Comparison of azlocillin, ceftizoxime, cefoxitin, and amikacin alone and in combination against Pseudomonas aeruginosa in a neutropenic-site rabbit model

The efficacy of beta-lactam antibiotics and amikacin alone and in various combinations against Pseudomonas aeruginosa was studied in a rabbit model simulating a closed-space infection in a locally neutropenic site. Six strains of P. aeruginosa were studied in semipermeable chambers placed subcutaneously in rabbits. Therapy was begun 4 h after inoculation of 5 X 10(4) CFU of bacteria per ml of pooled rabbit serum into the chambers. Antibiotics were administered intramuscularly every 6 h for 16 doses. Quantitative bacteriology was measured at the start of therapy and at 20, 44, and 92 h thereafter. Antibiotic concentrations were measured in blood and chamber fluid. Results were compared with in vitro tests of susceptibility and synergy. No single-agent therapy eradicated any of the six test organisms. Azlocillin (100 mg/kg per dose) plus amikacin (20 mg/kg per dose) eliminated five of six organisms by 92 h, and ceftizoxime (100 mg/kg per dose) plus amikacin (20 mg/kg per dose) eliminated three of six test strains. Azlocillin plus ceftizoxime (each 100 mg/kg per dose) failed to eliminate any of the six strains. To eliminate P. aeruginosa in this model, two drugs were required, with one being an aminoglycoside. In vitro susceptibility tests of synergy were predictive of successful therapy whenever the antibiotic concentrations (free and total) at the infection site exceeded the MBC for both the aminoglycoside alone and the beta-lactam when tested in combination with amikacin.