Saline Environments as a Source of Potential Quorum Sensing Disruptors to Control Bacterial Infections: A Review.

Saline environments, such as marine and hypersaline habitats, are widely distributed around the world. They include sea waters, saline lakes, solar salterns, or hypersaline soils. The bacteria that live in these habitats produce and develop unique bioactive molecules and physiological pathways to cope with the stress conditions generated by these environments. They have been described to produce compounds with properties that differ from those found in non-saline habitats. In the last decades, the ability to disrupt quorum-sensing (QS) intercellular communication systems has been identified in many marine organisms, including bacteria. The two main mechanisms of QS interference, i.e., quorum sensing inhibition (QSI) and quorum quenching (QQ), appear to be a more frequent phenomenon in marine aquatic environments than in soils. However, data concerning bacteria from hypersaline habitats is scarce. Salt-tolerant QSI compounds and QQ enzymes may be of interest to interfere with QS-regulated bacterial functions, including virulence, in sectors such as aquaculture or agriculture where salinity is a serious environmental issue. This review provides a global overview of the main works related to QS interruption in saline environments as well as the derived biotechnological applications.

Non-oral gram-negative facultative rods in chronic periodontitis microbiota.

OBJECTIVE: The subgingival prevalence of gram-negative facultative rods not usually inhabiting or indigenous to the oral cavity (non-oral GNFR), as well as selected periodontal bacterial pathogens, were evaluated by culture in untreated and treated chronic periodontitis patients. METHODS: Subgingival biofilm specimens from 102 untreated and 101 recently treated adults with chronic periodontitis in the Netherlands were plated onto MacConkey III and Dentaid selective media with air-5% CO2 incubation for isolation of non-oral GNFR, and onto enriched Oxoid blood agar with anaerobic incubation for recovery of selected periodontal bacterial pathogens. Suspected non-oral GNFR clinical isolates were identified to a species level with the VITEK 2 automated system. RESULTS: A total of 87 (42.9%) out of 203 patients yielded subgingival non-oral GNFR. Patients recently treated with periodontal mechanical debridement therapy demonstrated a greater prevalence of non-oral GNFR (57.4% vs 28.4%, P < 0.0001), and a greater number of different non-oral GNFR species (23 vs 14 different species), than untreated patients. Sphingomonas paucimobilis was the most frequently isolated subgingival non-oral GNFR species. Several GNFR species normally found in animals and human zoonotic infections, and not previously detected in human subgingival biofilms, were recovered from some patients, including Bordetella bronchispetica, Pasteurella canis, Pasteurella pneumotropica and Neisseria zoodegmatis. Porphyromonas gingivalis and Tannerella forsythia were significantly associated with the presence of subgingival non-oral GNFR. CONCLUSIONS: A surprisingly high proportion of Dutch chronic periodontitis patients yielded cultivable non-oral GNFR in periodontal pockets, particularly among those recently treated with periodontal mechanical debridement therapy. Since non-oral GNFR species may resist mechanical debridement from periodontal pockets, and are often not susceptible to many antibiotics frequently used in periodontal practice, their subgingival presence may complicate periodontal treatment in species-positive patients and increase risk of potentially dangerous GNFR infections developing at other body sites.

Presence and antimicrobial profile of gram-negative facultative anaerobe rods in patients with chronic periodontitis and gingivitis.

Chronic periodontitis is a multifactorial infectious disease associated with Gram-negative anaerobes which are part of the subgingival microflora. In recent years, studies have been conducted to assess the presence of Gram-negative facultative anaerobes (Enterobacteriaceae) and their participation in the development and progression of chronic periodontitis. The aim of this study was to determine the presence of Enterobacteriaceae in patients with chronic periodontitis and gingivitis and to assess antimicrobial susceptibility of clinical isolates. A descriptive, observational study was performed including 64 patients with chronic periodontitis and 22 patients with gingivitis. Microbiological samples were taken from the gingival sulcus using paper points, which then were placed in thioglycollate broth. Samples were incubated for 4 hours at 37 degrees C and finally replated on MacConkey agar Bacteria were identified using the API-20E system (Biomerieux, France) and antimicrobial susceptibility was determined using the disk diffusion method. The evaluation of samples showed presence of 29 enterobacterial species distributed as follows: 7 in the group with gingivitis and 22 in the group with chronic periodontitis. In the chronic periodontitis group the most common species were: K. oxytoca n = 5, S. liquefaciens n = 4 and K. pneumoniae and E. coli with n = 3. The gingivitis group had the highest frequency of Erwinia sp. (n = 2). Clinical isolates showed very low sensitivity levels to beta-lactam ampicillin and amoxicillin/ clavulanic acid, 17.2% and 27.6% respectively, and higher sensitivity levels to ciprofloxacin (96.6%), amikacin (79.3%), gentamicin (68.9%) and ceftazidime, ceftriaxone, kanamycin and trimethoprimsulfa (65.5%). In conclusion, the existence of a high frequency of enterobacteria in patients with chronic periodontitis and gingivitis shows that periodontologists should pay greater attention to prevention protocols, and develop mechanical and antimicrobial therapies in which antimicrobial susceptibility profile reports should be considered as part of periodontal treatment.

Evaluation of direct inoculation of the BD PHOENIX system from positive BACTEC blood cultures for both Gram-positive cocci and Gram-negative rods.

BACKGROUND: Rapid identification (ID) and antibiotic susceptibility testing (AST) of the causative micro-organism of bloodstream infections result in earlier targeting of antibiotic therapy.In order to obtain results of ID and AST up to 24 hours earlier, we evaluated the accuracy of direct inoculation of the Phoenix system from positive blood cultures (BACTEC) by using Serum Separator Tubes to harvest bacteria from positive blood cultures. Results were compared to those of standard Phoenix procedure. Discrepancies between the two methods were resolved by using the API system, E-test or microbroth dilution. RESULTS: ID with the direct method was correct for 95.2% of all tested Enterobacteriaceae (n = 42) and 71.4% of Pseudomonas aeruginosa strains (n = 7).AST with the direct method showed a categorical agreement for Gram-negative rods (GNR) of 99.0%, with 0.7% minor errors, 0.3% very major errors and no major errors. All antibiotics showed an agreement of >95%.The direct method for AST of Staphylococcus (n = 81) and Enterococcus (n = 3) species showed a categorical agreement of 95.4%, with a minor error rate of 1.1%, a major error rate of 3.1% and a very major error rate of 0.4%. All antibiotics showed an agreement of >90%, except for trimethoprim-sulfamethoxazole and erythromycin. CONCLUSIONS: Inoculation of Phoenix panels directly from positive blood cultures can be used to report reliable results of AST of GNR a day earlier, as well as ID-results of Enterobacteriaceae. For Staphylococcus and Enterococcus species, results of AST can also be reported a day earlier for all antibiotics, except for erythromycin and trimethoprim-sulfamethoxazole.

Antimicrobial activity of Gynostemma pentaphyllum extracts against fungi producing aflatoxin and fumonisin and bacteria causing diarrheal disease.

Gynostemma pentaphyllum was investigated to determine its antimicrobial activities against human.and animal pathogens that produce aflatoxin, fumonisin, and diarrheal disease. The fungi were Aspergillusflavus, Aspergillus parasiticus and Fusarium verticillioides. The bacteria were Vibrio, Salmonella, Shigella, Escherichia coli and Staphylococcus aureus. G. pentaphyllum was extracted by five different methods. The obtained extracts were designated Extracts A, B, C, D and E. The results of the antifungal assay against A.flavus andA. parasiticus showed Extracts A and B at 10,000 ppm inhibited growth at 8-28%. Extracts A and B at 10,000 ppm also showed activity against F. verticillioides at 41-43%. Extract A, B and C were able to inhibit the tested strains better than the Extracts D and E. The MIC values of the extracts against gram-negative bacteria ranged from

Bacterial pathogens associated with bloody diarrhea in Uruguayan children.

Diarrheal disease continues to be a serious health problem, especially in developing countries. Bloody diarrhea represents approximately 20-30% of all cases and has higher morbidity and mortality. Treatment with antibiotics is beneficial in cases of Shigella, Campylobacter, Yersinia and Salmonella infection, principally in those children with a higher risk of invasive disease. The aims of this study were to detect the bacterial agents associated with bloody diarrhea in children and to determine their antimicrobial susceptibility patterns. Between June 2001 and January 2008, 249 children with bloody diarrhea were studied. Shigella and Shiga toxin-producing Escherichia coli (STEC) were recovered from 48 (19.3%) and 3 (1.2%) of the total of cases, respectively. In 49 out of 249 children, in whom other enteropathogens were investigated, we recovered Campylobacter jejuni from 7 children (14.3%), Salmonella spp. from 2 (4.1%) and Aeromonas spp. from 1 (2%) in addition to Shigella from 7 children (14.3%). Thirty-four (70%) Shigella isolates showed resistance to ampicillin and 13 (27%) to trimethoprim-sulfamethoxazole. All Shigella isolates were susceptible to nalidixic acid, ciprofloxacin and ceftriaxone. Salmonella and STEC isolates were susceptible to all antibiotics assayed. Thus, the use of trimethoprim-sulfamethoxazole or ampicillin would not be appropriate for the empirical treatment of Shigella - associated diarrhea.

[Recent trend and research issues related to antimicrobial-resistant bacteria].

The discovery of penicillin in 1928 was followed by the discovery and synthesis of various kinds of antimicrobial agents such as quinolone, aminogycoside, macrolide, tetracyclone, and oxazolidinone. These discoveries dramatically decreased the mortality rate due to infectious diseases. However, bacteria have also acquired antimicrobial-resistance genes or changed their own genes to oppose these antimicrobial agents, and now drug-resistant bacteria are becoming a serious clinical concern. Today, contagious diseases must be treated with the limited number of effective antimicrobial agents available. Infection control measures are required to prevent the spread of resistant bacteria in the clinical environment, and we must also increase our understanding of the drug-resistant mechanisms of bacteria. In this issue we wish to introduce the recent worldwide trend in antimicrobial-resistant bacteria, especially multidrug-resistant bacteria, such as methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus, and multidrug-resistant Pseudomonas aeruginosa, along with recently-discovered antimicrobial-resistant systems.

Short- and long-term predictors of spontaneous bacterial peritonitis in Singapore.

INTRODUCTION: Spontaneous bacterial peritonitis (SBP) is the commonest complication of liver cirrhosis. Timely and appropriate treatment of SBP is crucial, particularly with the rising worldwide prevalence of multidrug-resistant organisms (MDROs). We aimed to investigate the clinical outcomes of SBP in Singapore. METHODS: All cirrhotic patients with SBP diagnosed between January 2014 and December 2017 were included. Nosocomial SBP (N-SBP) was defined as SBP diagnosed more than 48 hours after hospitalisation. Clinical outcomes were analysed as categorical outcomes using univariate and multivariate analysis. RESULTS: There were 33 patients with 39 episodes of SBP. Their mean age was 64.5 years and 69.7% were male. The commonest aetiology of cirrhosis was hepatitis B (27.3%). The Median Model for End-stage Liver Disease (MELD) score was 17; 33.3% had acute-on-chronic liver failure and 60.6% had septic shock at presentation. N-SBP occurred in 25.6% of SBP cases. N-SBP was more commonly associated with MDROs, previous antibiotic use in the past three months (p = 0.014) and longer length of stay (p = 0.011). The 30-day and 90-day mortality among SBP patients was 30.8% and 51.3%, respectively. MELD score > 20 was a predictor for 30-day mortality. N-SBP and MELD score > 20 were predictors for 90-day mortality. CONCLUSION: N-SBP was significantly associated with recent antibiotic use, longer hospitalisation, more resistant organisms and poorer survival among patients with SBP. N-SBP and MELD score predict higher mortality in SBP. Judicious use of antibiotics may reduce N-SBP and improve survival among cirrhotic patients.

Incidence of Bacterial Enteropathogens among Diarrhea Patients from Tribal Areas of Odisha.

Infectious diarrheal diseases remain a leading cause of morbidity and mortality in developing and underdeveloped countries. The present study documented the etiology of bacterial enteropathogens in three tribal districts of Odisha from July 2010 to September 2013. A total of 1427 rectal swabs were collected and bacteriologically analyzed by following standard procedure. Among the 930 (65.2%) culture positive samples, Escherichia coli (E. coli) constituted 636 (44.6%); Vibrio cholerae (V. cholerae) O1, 146 (10.2%); Salmonella species (spp.), 10 (0.7%); Shigella spp., 79 (5.5%); and Aeromonas spp., 59 (4.1%). Of the 729 environmental water samples taken from river, open well, Nala (a small stream), and Chua (a shallow pit on a river bed), 14 (1.9%) contained non-O1/non-O139 V. cholerae and 13 (1.8%) had V. cholerae O1 strains. An analysis of the demographics showed that people in the 14 to 40-year age group were highly susceptible to diarrhea caused by V. cholerae which occurred mainly during the rainy and post-rainy seasons. All enteropathogens were multidrug-resistant and found throughout the study period. The V. cholerae strains isolated were El Tor variants carrying the classical, El Tor, and Haitian cholera toxin subunit B (ctxB) genes. The classical ctxB was the dominant allele, and the prevalence of the Haitian ctxB allele increased during the test period. These findings indicate that active surveillance is needed to monitor the changing antibiotic resistance patterns of V. cholerae serogroups and biotypes present in this region.

Antimicrobial-resistant pathogens associated with adult healthcare-associated infections: Summary of data reported to the National Healthcare Safety Network, 2015-2017.

OBJECTIVE: Describe common pathogens and antimicrobial resistance patterns for healthcare-associated infections (HAIs) that occurred during 2015-2017 and were reported to the Centers for Disease Control and Prevention's (CDC's) National Healthcare Safety Network (NHSN). METHODS: Data from central line-associated bloodstream infections (CLABSIs), catheter-associated urinary tract infections (CAUTIs), ventilator-associated events (VAEs), and surgical site infections (SSIs) were reported from acute-care hospitals, long-term acute-care hospitals, and inpatient rehabilitation facilities. This analysis included device-associated HAIs reported from adult location types, and SSIs among patients ≥18 years old. Percentages of pathogens with nonsusceptibility (%NS) to selected antimicrobials were calculated for each HAI type, location type, surgical category, and surgical wound closure technique. RESULTS: Overall, 5,626 facilities performed adult HAI surveillance during this period, most of which were general acute-care hospitals with <200 beds. Escherichia coli (18%), Staphylococcus aureus (12%), and Klebsiella spp (9%) were the 3 most frequently reported pathogens. Pathogens varied by HAI and location type, with oncology units having a distinct pathogen distribution compared to other settings. The %NS for most pathogens was significantly higher among device-associated HAIs than SSIs. In addition, pathogens from long-term acute-care hospitals had a significantly higher %NS than those from general hospital wards. CONCLUSIONS: This report provides an updated national summary of pathogen distributions and antimicrobial resistance among select HAIs and pathogens, stratified by several factors. These data underscore the importance of tracking antimicrobial resistance, particularly in vulnerable populations such as long-term acute-care hospitals and intensive care units.

In vitro susceptibilities of aerobic and facultatively anaerobic gram-negative bacilli isolated from patients with intra-abdominal infections worldwide: 2005 results from Study for Monitoring Antimicrobial Resistance Trends (SMART).

BACKGROUND: The Study for Monitoring Antimicrobial Resistance Trends (SMART) is examining aerobic and facultatively anaerobic gram-negative bacilli (GNB) isolated from intra-abdominal infections. This report summarizes the 2005 annual data. METHODS: During 2005, 76 medical centers in 31 countries in five regions collected intra-abdominal GNB for antimicrobial susceptibility testing using broth microdilution according to the Clinical and Laboratory Standards Institute guidelines. RESULTS: A total of 5,476 unique aerobic and facultatively anaerobic GNB were isolated. Enterobacteriaceae accounted for 86% (4,711) of the total isolates. Among the 12 antimicrobial agents tested, the carbapenems and amikacin were the most reliably active against the Enterobacteriaceae, whereas ampicillin/sulbactam most often was the least active. Escherichia coli was the species most commonly isolated, at 48% (2,654). Extended-spectrum beta-lactamases (ESBLs) were detected phenotypically in 12% (325/2,329) of E. coli and 18% (151/856) of Klebsiella spp. In general, ESBL producers demonstrated lower susceptibility to the majority of the antibiotics than the non-producers; however, ESBL producers usually were susceptible to the carbapenems tested. CONCLUSIONS: In 2005, antibiotic resistance continued to be a problem among GNB isolated from intra-abdominal infections, with the highest resistance rates observed in the Asia/Pacific region. Imipenem-cilastatin, ertapenem, and amikacin were the agents most consistently active in vitro against the Enterobacteriaceae isolated.

Triclosan-lysozyme complex as novel antimicrobial macromolecule: a new potential of lysozyme as phenolic drug-targeting molecule.

A novel anti-infection strategy to alleviate antibiotic-resistance problem and non-specific toxicity associated with chemotherapy is explored in this study. It is based on utilizing a bacteriolytic enzyme (lysozyme) as a carrier to allow specific targeting of a potential phenolic antimicrobial drug (triclosan) to microbial cells. Lysozyme (LZ) was complexed, via electrostatic and hydrophobic condensation at alkaline pH, to various degrees with triclosan (TCS), a negatively charged phenolic antimicrobial that inhibits bacterial fatty acid synthesis. Fluorescence and absorbance spectra analysis revealed non-covalent association of TCS with the aromatic residues at the interior of LZ molecule. The conjugation greatly promoted the lytic activity of LZ as the degree of TCS derivatization increased. The complexation with LZ turned TCS into completely soluble in aqueous solution. TCS-LZ complexes showed significantly enhanced bactericidal activity against several strains of Gram-positive and Gram-negative bacteria compared to the activity of TCS or LZ alone when tested at the same molar basis. Strikingly, TCS-LZ complex, but not LZ or TCS alone, exhibited unique specificity to scavenge superoxide radicals, generated by the natural xanthine/xanthine oxidase coupling system, without affecting the catalytic function of oxidase. This finding is the first to describe that the membrane disrupting function of lysozyme can be utilized to specifically target antimicrobial drug(s) to pathogen cells and heralding a fascinating opportunity for the potential candidacy of TCS-LZ as novel antimicrobial strategy for human therapy.

Comparison of direct disk diffusion and standard microtitre broth dilution susceptibility testing of blood culture isolates.

Bloodstream infections are life-threatening conditions which require timely initiation of appropriate antimicrobial therapy. The accuracy of direct disk diffusion susceptibility testing of positive blood cultures was investigated, including for the first time beta-lactam/beta-lactam-inhibitor combination antibiotics. Results of direct testing, following the guidelines of the Clinical and Laboratory Standards Institute, were compared to standard microtitre broth dilution susceptibility testing of the subcultured isolate on the Merlin MICRONAUT system. Altogether, 758 isolates and 4930 organism/antibiotic combinations from 590 patients were evaluated. With regard to Gram-positive cocci (n=532), agreement between both methods was found in 93.9% of cases, with 1.6% very major, 1.1% major and 2.6% minor errors. For Gram-negative rods (n=226), agreement was found in 91.9% of cases, with 1.2% very major, 0.7% major and 6.3% minor errors. When applying the breakpoints of the Deutsches Institut für Normung for interpretation of MICRONAUT tests, agreement of direct disk diffusion with standard testing decreased to 82.4% in Gram-negative rods, with 3.6% very major, 0.5% major and 13.4% minor errors. A high rate of disagreement was observed with oxacillin and gentamicin in Gram-positive cocci, and with cefuroxime, amoxycillin/clavulanate and piperacillin/tazobactam in Gram-negative rods. In conclusion, the limitations of direct disk diffusion testing of positive blood cultures must be kept in mind by the clinical microbiologist and should, where necessary, be communicated to the clinician to ensure adequate treatment of severely ill patients.

[Gramnegative opportunistic microflora as etiological factor of secondary infection in patients with pulmonary tuberculosis].

The results of the laboratory diagnoses of respiratory tract secondary infections in patients with pulmonary tuberculosis within a period of 12 months in a tuberculosis clinic were generalized. The species composition of the causative agents of lower respiratory tract secondary infection and the frequency of their detection in various clinical speciments (sputum, bronchial washings) were determined. The data on resistance of the opportunistic gramnegative bacilli (enterobacteria, pseudomonads, Acinetobacter spp.) isolated from the patients with pulmonary tuberculosis to various groups of antibacterials are presented.

Antimicrobial-Resistant Pathogens Associated With Healthcare-Associated Infections: Summary of Data Reported to the National Healthcare Safety Network at the Centers for Disease Control and Prevention, 2011-2014.

OBJECTIVE To describe antimicrobial resistance patterns for healthcare-associated infections (HAIs) that occurred in 2011-2014 and were reported to the Centers for Disease Control and Prevention's National Healthcare Safety Network. METHODS Data from central line-associated bloodstream infections, catheter-associated urinary tract infections, ventilator-associated pneumonias, and surgical site infections were analyzed. These HAIs were reported from acute care hospitals, long-term acute care hospitals, and inpatient rehabilitation facilities. Pooled mean proportions of pathogens that tested resistant (or nonsusceptible) to selected antimicrobials were calculated by year and HAI type. RESULTS Overall, 4,515 hospitals reported that at least 1 HAI occurred in 2011-2014. There were 408,151 pathogens from 365,490 HAIs reported to the National Healthcare Safety Network, most of which were reported from acute care hospitals with greater than 200 beds. Fifteen pathogen groups accounted for 87% of reported pathogens; the most common included Escherichia coli (15%), Staphylococcus aureus (12%), Klebsiella species (8%), and coagulase-negative staphylococci (8%). In general, the proportion of isolates with common resistance phenotypes was higher among device-associated HAIs compared with surgical site infections. Although the percent resistance for most phenotypes was similar to earlier reports, an increase in the magnitude of the resistance percentages among E. coli pathogens was noted, especially related to fluoroquinolone resistance. CONCLUSION This report represents a national summary of antimicrobial resistance among select HAIs and phenotypes. The distribution of frequent pathogens and some resistance patterns appear to have changed from 2009-2010, highlighting the need for continual, careful monitoring of these data across the spectrum of HAI types. Infect Control Hosp Epidemiol 2016;1-14.

Hospital-acquired pneumonia: epidemiology, etiology, and treatment.

Despite improvements in diagnosis, treatment, and prevention, hospital-acquired pneumonia (HAP) remains the number one cause of nosocomial mortality. This article reviews the current knowledge regarding the incidence, epidemiology, and causes of HAP, with the appreciation that the available information is incomplete and that controversies are common, and thus the authors provide a rational approach to the initial management of HAP in immunocompetent adults. A discussion of therapy and what to do with patients who do not respond to the empiric therapy are included. The American Thoracic Society (ATS) statement on HAP has served as a foundation for this review but has been supplemented by newer literature that was not available when the ATS statement was developed.

Resistance issues and treatment implications: pneumococcus, Staphylococcus aureus, and gram-negative rods.

During the last decade there has been an unexpectedly rapid evolution of antimicrobial resistance in the respiratory pathogens for community- and hospital-acquired pneumonia. In order to choose the most optimal therapy for their patients, it is essential that physicians be aware of the prevalence and mechanisms of resistance and their implications on the effectiveness of the various antimicrobials.

Antimicrobial activity and spectrum investigation of eight broad-spectrum beta-lactam drugs: a 1997 surveillance trial in 102 medical centers in the United States. Cefepime Study Group.

Because antimicrobial agents become less effective after the emergence of resistance mechanisms in clinically prevalent pathogens, physicians must utilize local, regional, and national antimicrobial susceptibility surveillance data to assist in choices of appropriate agents. An investigation of the spectrum and potency of eight broad-spectrum beta-lactam drugs (cefepime, cefotaxime, ceftazidime, ceftriaxone, imipenem, piperacillin with or without tazobactam, and ticarcillin/clavulanic acid) was performed using a common protocol and method (Etest; AB BIODISK, Solna, Sweden) in 102 clinical microbiology laboratories in the United States. A total of 9777 strains of Gram-negative bacilli were tested from late 1996 through April 1997. Quality assurance measures using three control strains observed quality control failures in 13 laboratories (usually ticarcillin/clavulanic acid or piperacillin), but only 2% of results required deletion. A total of 33.4% of Enterobacter spp. (1977 strains) were either resistant or intermediately susceptible to ceftazidime. Only imipenem (99.6% susceptible) and cefepime (99.1%) remained highly active against strains of Enterobacter, as well as Citrobacter freundii, indole-positive Proteae, and Serratia spp. Ceftazidime-resistant Escherichia coli and Klebsiella pneumoniae were detected at rates of 10.3% and 23.8%, respectively. Although these were participant-selected strains, only imipenem and cefepime had broad-spectrum coverage (> or = 97.1%) against these extended-spectrum beta-lactamase phenotypes. A dominant number of these extended-spectrum beta-lactamase phenotypes were reported from medical centers in the Northeast, but a nationwide distribution was observed. Among the nonenteric Gram-negative bacilli (4057 strains), the rank order of susceptibility (percent inhibited at published breakpoint concentrations) was: imipenem (86.1%) > piperacillin/tazobactam (80.1%) > cefepime (77.1%) > ceftazidime = piperacillin (74.9%) > ticarcillin/clavulanic acid (61.6%) > cefotaxime (18.2%) > ceftriaxone (12.9%). The cephalosporins, cefepime and ceftazidime, had rates of resistance for the 3005 Pseudomonas aeruginosa isolates of 10.1% and 14.4%, respectively. For all Gram-negative strains tested, only two contemporary beta-lactam antimicrobials exhibited > 90% inhibition of strains, imipenem at 93.6% and cefepime at 90.2%. These drugs were superior to the other tested compounds (48.8-84.3%). Ticarcillin/clavulanic acid had the narrowest spectrum of activity (48.8% of isolates susceptible). These results indicate that carbapenems and a new fourth-generation cephalosporin, cefepime, possess usable in vitro potencies against current clinical strains of Gram-negative bacilli, many of which harbored resistance to other antimicrobial agents.

Effect of modified atmosphere packaging on the TVB/TMA-producing microflora of cod fillets.

Cod fillets (Gadus morhua) were packed under modified atmospheres, with four different gas compositions (60% CO2-10% O2-30% N2, 60% CO2-20% O2-20% N2, 60% CO2-30% O2-10% N2, 60% CO2-40% O2), and stored at 6 degrees C. Plate counts were carried out after 3, 4, 5, 6 and 7 days, to follow the growth of aerobic and anaerobic bacteria, lactic acid bacteria, H2S-producing bacteria and Enterobacteriaceae. The production of total volatile bases (TVB) and trimethylamine (TMA), and the changes in pH of the fillets were measured. Modified atmosphere packaging (MAP) had in general an inhibitory effect on the growth of the microflora but limited inhibition of the production of TVB and TMA. Despite the fact that increased oxygen proportions in the atmosphere contributed in a slightly lower production of TMA, all the samples had a TVB and TMA content high enough to be considered as spoiled after 4 days' storage at 6 degrees C. A total aerobic plate count at 25 degrees C of a 10(6) cfu/g, combined with the presence of only a 10(3) cfu/g of H2S-producing bacteria, which are normally considered as TMAO-reducing organisms in fish, cannot explain the strong increase in TMA. A high cell concentration of more than 10(8) cfu/g of Shewanella putrefaciens is required for production of a TMA level normally found in spoiled fish. This suggests that there could be another type of bacterium in fish, not involved in the spoilage of unpacked fish, which is resistant to 60% CO2, is not H2S-producing, and shows a high TMAO-reducing capacity. This bacterium could be Photobacterium phosphoreum.