Search

The prevalence of aac(6')-Ib-cr and its associated genes and mobile elements was investigated in Serratia marcescens collected from 12 hospitals in Korea in 2005 and 2006. A total of 215 isolates (from 166 and 149 isolates collected in 2005 and 2006, respectively) were included in the study. Aac(6')-Ib-cr was detected in only two isolates collected in 2005 and in 12 isolates collected from three hospitals in 2006. All 12 isolates carried class 1 integron and coharbored bla(CTX-M) and armA. Bla(OXA-1) and ISCR1 were detected in 10 and 8 isolates, respectively. All 12 isolates carried IncL/M type plasmid and 6 of them also carried IncA/C type plasmid. Conjugal transfer was successful for 9 of 12 aac(6')-Ib-cr, all 12 bla(CTX-M), 8 of 12 armA, and 6 of 10 bla(OXA-1). Of the 12 transconjugants, IncL/M type plasmid, IntI1, ISEcp1, and ISCR1 were detected in 12, 9, 12, and 8, respectively. The transferability of aac(6')-Ib-cr, armA, and bla(OXA-1) was 100% for isolates harboring ISCR1, against 25%, 0%, and 0%, respectively, for isolates not harboring ISCR1. Both clonal and horizontal transfer were demonstrated by pulsed-field gel electrophoresis and plasmid profile analysis, respectively. Stringent infection control practices and further investigation of association between mobile elements and resistance genes are warranted.

Chemical investigation of the octocoral Sarcophyton ehrenbergi, collected at the Dongsha Islands, Taiwan, has led to the isolation of a known ceramide (1) and two new cerebrosides, sarcoehrenosides A (2) and B (4), along with three known cerebrosides (3, 5, and 6). The structures of the new compounds were established by spectroscopic and chemical methods. Sarcoehrenoside A (2) differs from previously known marine cerebrosides in that it possesses a rare alpha-glucose moiety. Compounds 1-6 were evaluated for antimicrobial activity against a small panel of bacteria and for anti-inflammatory activity using RAW 264.7 macrophages.

Objective: To investigate the hypothesis that reasonable levels of disinfection are achievable over relatively short exposure durations of microorganisms to multipurpose solutions, this study examined the stand-alone disinfection efficacy at 10, 20, and 30 min of five different multipurpose solutions products, each against five different pathogens eye care practitioners may encounter in their contact lens practice., Methods: ReNu MultiPlus, ReNu Multi-Purpose, AQuify, OptiFree Express, and OptiFree RepleniSH were evaluated for their microbiocidal efficacy using the stand-alone method at 10, 20, and 30 min of exposure to either Fusarium solani, Candida albicans, Staphylococcus aureus, Serratia marcescens, or Pseudomonas aeruginosa., Results: Solutions which showed significantly higher rates of disinfection at 30 min were ReNu MultiPlus against Fusarium solani and Candida albicans, and both ReNu MultiPlus and AQuify against Staphylococcus aureus and Serratia marcescens. There were no statistically significant differences at 30 min amongst solutions against Pseudomonas aeruginosa., Conclusions: The product attribute of rapid rate of disinfection may give a greater level of assurance to practitioners when patients are noncompliant and do not follow the recommended time period for lens disinfection. The results of this study, however, should not be interpreted as a recommendation to use any of the solutions tested for a disinfection period less than the recommended soak time. Patient compliance with recommended lens care regimens is essential in minimizing the risk of contamination of contact lenses and lens care accessories.

For production of protease by a new strain, Serratia marcescens SB08, optimization of the fermentation medium and environmental conditions, were carried out by applying factorial design and response surface methodology. The results of factorial design showed that pH, agitation, incubation time and yeast extract were the key factors affecting protease production. The optimal cultural conditions for protease production obtained with response surface methodology were pH 6.0, agitation 100 rpm, incubation time 51.0 h and yeast extract 3.0 g/l. This model was also validated by repeating the experiments under the optimized conditions, which resulted in the maximum protease production of 281.23 U/ml (Predicted response 275.66 U/ml), thus proving the validity of the model. Unexplored Serratia marcescens SB08 strain isolated from enteric gut of sulphur butterfly (Kricogonia lyside) was taken up for this study. This study demonstrates the ability of the new strain, Serratia marcescens SB08, for protease production and also that smaller and less time consuming statistical experimental designs are adequate for the optimization of fermentation processes for maximum protease production.

Serratia marcescens is a gram-negative environmental bacterium and opportunistic pathogen. S. marcescens expresses prodigiosin, a bright red and cell-associated pigment which has no known biological function for producing cells. We present here a kinetic model relating cell, ATP, and prodigiosin concentration changes for S. marcescens during cultivation in batch culture. Cells were grown in a variety of complex broth media at temperatures which either promoted or essentially prevented pigmentation. High growth rates were accompanied by large decreases in cellular prodigiosin concentration; low growth rates were associated with rapid pigmentation. Prodigiosin was induced most strongly during limited growth as the population transitioned to stationary phase, suggesting a negative effect of this pigment on biomass production. Mathematically, the combined rate of formation of biomass and bioenergy (as ATP) was shown to be equivalent to the rate of prodigiosin production. Studies with cyanide inhibition of both oxidative phosphorylation and pigment production indicated that rates of biomass and net ATP synthesis were actually higher in the presence of cyanide, further suggesting a negative regulatory role for prodigiosin in cell and energy production under aerobic growth conditions. Considered in the context of the literature, these results suggest that prodigiosin reduces ATP production by a process termed energy spilling. This process may protect the cell by limiting production of reactive oxygen compounds. Other possible functions for prodigiosin as a mediator of cell death at population stationary phase are discussed.

In a laboratory study, we demonstrated that 3 alcohol-based hand gels, commercially available in Brazil, were as effective as the traditional 70% ethyl alcohol (by weight) in removing clinical isolates of methicillin-resistant Staphylococcus aureus, Serratia marcescens, and Candida albicans from heavily contaminated hands of human volunteers.

Different bacterial species were isolated from different areas of the Kor River and growth pattern of these bacteria were evaluated. In this study the samples were collected from four stations throughout the Kor River in four seasons. Isolation of mercury resistant bacteria was performed using the primary enrichment method and directly plating on agar containing Hg(II). Growth kinetics of most mercury resistant and sensitive bacteria were studied in LB broth containing 20 mg L(-1) HgCl2 per liter. Pseudomonas sp., E. coli, Serratia morcescens, etc. was identified as mercury resistant bacteria. Isolated bacteria from the most mercury polluted stations showed high levels of resistance to this toxicant. Growth curve of mercury resistant bacteria was obtained the same as the standard growth curve of bacteria. Present results showed that enhancement of mercury levels in the environment will increase the levels of resistance to mercury among the bacterial communities residing in this contaminated sites.

Background and Purpose: Strains of extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae have spread widely in Taiwan hospitals. In this study, we evaluated the in vitro antimicrobial activity of tigecycline against ESBL-producing Enterobacteriaceae, including Klebsiella pneumoniae, Serratia marcescens and Enterobacter cloacae., Methods: 104 confirmed ESBL-producing bacteria were isolated from 4 hospitals in mid- and southern Taiwan between 2000 and 2006. The in vitro activity of tigecycline against these ESBL producers was tested by use of Etest strips., Results: The minimal tigecycline concentration at which 50% of isolates were inhibited and minimal concentration at which 90% of isolates were inhibited for ESBL-producing isolates ranged from 0.38 to 0.75 microg/mL and 0.5 to 1.5 microg/mL, respectively., Conclusions: Tigecycline, a new semisynthetic glycylcycline, may be considered an alternative drug of choice for patients infected with ESBL-producing bacteria.

Antimicrobial hand soaps provide a greater bacterial reduction than nonantimicrobial soaps. However, the link between greater bacterial reduction and a reduction of disease has not been definitively demonstrated. Confounding factors, such as compliance, soap volume, and wash time, may all influence the outcomes of studies. The aim of this work was to examine the effects of wash time and soap volume on the relative activities and the subsequent transfer of bacteria to inanimate objects for antimicrobial and nonantimicrobial soaps. Increasing the wash time from 15 to 30 seconds increased reduction of Shigella flexneri from 2.90 to 3.33 log(10) counts (P = 0.086) for the antimicrobial soap, while nonantimicrobial soap achieved reductions of 1.72 and 1.67 log(10) counts (P > 0.6). Increasing soap volume increased bacterial reductions for both the antimicrobial and the nonantimicrobial soaps. When the soap volume was normalized based on weight (approximately 3 g), nonantimicrobial soap reduced Serratia marcescens by 1.08 log(10) counts, compared to the 3.83-log(10) reduction caused by the antimicrobial soap (P < 0.001). The transfer of Escherichia coli to plastic balls following a 15-second hand wash with antimicrobial soap resulted in a bacterial recovery of 2.49 log(10) counts, compared to the 4.22-log(10) (P < 0.001) bacterial recovery on balls handled by hands washed with nonantimicrobial soap. This indicates that nonantimicrobial soap was less active and that the effectiveness of antimicrobial soaps can be improved with longer wash time and greater soap volume. The transfer of bacteria to objects was significantly reduced due to greater reduction in bacteria following the use of antimicrobial soap.

Twenty-one Serratia marcescens, ten Klebsiella pneumoniae, and one Escherichia coli isolate with carbapenem resistance or reduced carbapenem susceptibility were recovered from intensive care units (ICUs) in our hospital. Enterobacterial repetitive intergenic consensus-PCR and pulsed-field gel electrophoresis demonstrated that all the S. marcescens isolates belonged to a clonal strain and the 10 K. pneumoniae isolates were indistinguishable or closely related to each other. The MICs of imipenem, meropenem, and ertapenem for all isolates were 2 to 8 microg/ml, except for K. pneumoniae K10 (MICs of 128, 256, and >256 microg/ml). Isoelectric focusing, PCRs, and DNA sequencing indicated that all S. marcescens isolates produced KPC-2 and a beta-lactamase with a pI of 6.5. All K. pneumoniae isolates produced TEM-1, KPC-2, CTX-M-14, and a beta-lactamase with a pI of 7.3. The E. coli E1 isolate produced KPC-2, CTX-M-15, and a beta-lactamase with a pI of 7.3. Conjugation studies with E. coli (EC600) resulted in the transfer of reduced carbapenem susceptibility compared to that of the original isolates, and only the bla(KPC-2) gene was detected in E. coli transconjugants. Plasmid restriction analysis showed identical restriction patterns among all E. coli transconjugants. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and ompK35/36 gene sequence analysis of outer membrane proteins revealed that K. pneumoniae K10 failed to express OmpK36, because of insertional inactivation by an insertion sequence ISEcp1. All these results indicate that KPC-2-producing S. marcescens, K. pneumoniae, and E. coli isolates emerged in ICUs in our hospital. KPC-2 combined with porin deficiency results in high-level carbapenem resistance in K. pneumoniae. The same bla(KPC-2)-encoding plasmid was spread among the three different genera.

Objective: A four-fold increase in the incidence of Serratia marcescens occurred in a cardio-thoracic ICU within a 13-month period. Clinical, epidemiological and molecular characteristics were analysed to elucidate the outbreak's origin., Methods: Epidemiological data were analysed by mapping clustered cases; isolates were genotyped by AFLP analysis. A case-control study was performed to identify risk factors for the acquisition of S. marcescens. Data were obtained from files and electronic databases of the ICU and Department of Medical Microbiology. The adherence to hygiene protocols on the ICU was reviewed by a medical audit., Results: Genotyping showed 16 distinct S. marcescens strains. Twenty-one cases and 39 controls were enrolled in the case-control study. Significant differences found by univariate analysis included the duration of surgery, APACHE-II-score on ICU admission, length of ICU stay, duration of mechanical ventilation, tube feeding and the sum of the number of days per invasive device. In a multivariate logistic regression model, the length of ICU stay and tube feeding were independent risk factors. Outbreak strains were not more frequently resistant to gentamicin, ciprofloxacin, meropenem or trimethoprim-sulfamethoxazole as compared to a reference group. Hygiene protocols, including hand washing, were insufficiently practiced by the ICU's medical staff., Conclusions: The heterogeneity of the strains points to transmission from various sources. This outbreak of S. marcescens was most probably caused by reduced hand washing and other breaks in infection prevention protocols in combination with the presence of the identified risk factors, which act by affecting the number and intensity of potential transmission events.

Background: Alcohol-based hand antiseptics are often tested using 3 or 5 mL per application, but smaller volumes are likely to be applied in clinical practice. For that reason, we investigated the efficacy of 2 different volumes of 4 marketed hand rubs when applied to contaminated hands., Methods: Hands of 16 volunteers were contaminated with Serratia marcescens. Hand rub A (85% ethanol), hand rub B (60% ethanol), hand rub C (62% ethanol), and hand rub D (61% ethanol) were applied as blinded formulations, each in single applications of 2.4 or 3.6 mL. Hibiclens (4% chlorhexidine gluconate) served as the reference treatment. Each hand rub was rubbed into the hands until dry. Preintervention and postintervention bacterial populations were obtained by the glove juice method. Neutralization of residual activity was validated., Results: A 2.4-mL aliquot of a hand rub product was sufficient to cover both hands in 96.9% of the subjects. Applied in that volume, hand rubs produced a log(10)-reduction in bacterial populations of 2.79 for hand rub A, 2.26 for hand rub C, 1.96 for hand rub D, and 1.90 for hand rub B. Application of 3.6 mL was significantly more effective for hand rubs B, C, and D. The reference treatment reduced test bacteria by 2.39 log(10). Analysis of variance revealed that both the type of hand rub and the applied volume had a highly significant influence on the mean log(10) reduction on artificially contaminated hands (P < .001)., Conclusions: Hand rubs applied in amounts sufficient to cover both hands may not reduce the bacterial density by even 2 log(10) steps. Based on our findings, the general trend toward alcohol-based hand rubs should not overlook evidence of significant differences in efficacy that appear to be related primarily to a product's overall concentration of alcohol.

Serratia marcescens is an important nosocomial agent having high antibiotic resistance. A major mechanism for S. marcescens antibiotic resistance is active efflux. To ascertain the substrate specificity of the S. marcescens SdeCDE efflux pump, we constructed pump gene deletion mutants. sdeCDE knockout strains showed no change in antibiotic susceptibility in comparison with the parental strains for any of the substrates, with the exception of novobiocin. In addition, novobiocin was the only antibiotic to be accumulated by sdeCDE-deficient strains. Based on the substrates used in our study, we conclude that SdeCDE is a Resistance-Nodulation-Cell Division family pump with limited substrate specificity.

Background: Serratia marcescens causes healthcare-associated infections and significant morbidity and mortality in neonatal intensive care units (NICUs). We report the investigation and control of an outbreak of multidrug-resistant (MDR) S. marcescens infection at an NICU., Methods: An outbreak investigation and a case-control study were undertaken at a 36-bed NICU in a tertiary care hospital in Baltimore, Maryland, for the period from October 2004 through February 2005. The outbreak investigation included case identification, review of medical records, environmental cultures, patient surveillance cultures, personnel hand cultures, and pulsed-field gel electrophoresis (PFGE). The case-control study included case identification and review of medical records. Infection control measures were implemented. Eighteen NICU neonates had cultures that grew MDR S. marcescens during the study period. The case-control study included 16 patients with the outbreak strain or an unidentified strain of MDR S. marcescens and 32 control patients not infected and/or colonized with MDR S. marcescens, treated in the NICU for at least 48 hours during the study period., Results: PFGE analysis identified a single strain of MDR S. marcescens that infected or colonized 15 patients. Two patients had unique strains, and 1 patient's isolate could not be subtyped. An unrelated MDR S. marcescens isolate was recovered from a sink drain. Exposure to inhalational therapy was an independent risk factor for MDR S. marcescens acquisition after adjusting for birth weight. Extensive investigation failed to reveal a point source for the outbreak., Conclusion: A single epidemic strain of MDR S. marcescens spread rapidly and threatened to become endemic in this NICU. Transient carriage on the hands of healthcare personnel or on respiratory care equipment was the likely mode of transmission. Cohorting patients and staff, at the cost of bed closures and additional personnel, interrupted transmission and halted the outbreak.

Purpose: To examine the ability of contact lenses coated with fimbrolides, inhibitors of bacterial quorum sensing, to prevent microbial adhesion and their safety during short-term clinical assessment., Methods: A fimbrolide was covalently attached to commercially available high Dk contact lenses. Subsequently Pseudomonas aeruginosa, Staphylococcus aureus, Serratia marcescens, or Acanthamoeba sp. were added to the lenses and control uncoated contact lenses. Lenses plus microbes were incubated for 24 h, then washed thoroughly to remove non-adherent microbes. Lenses were macerated and resulting slurry plated onto agar plates. After appropriate incubation, the numbers of colony forming units of bacteria (or numbers of Acanthamoeba trophozoites measured using a hemocytometer) from fimbrolide-coated and uncoated lenses were examined. A Guinea Pig model of lens wear was used to assess the safety of lenses worn on a continuous basis for 1 month. In a separate study, 10 subjects wore fimbrolide-coated lenses for 24 h. The responses of the Guinea Pigs and human volunteers to the lenses were assessed by slit lamp examination., Results: The fimbrolides-coated lenses reduced the adhesion of all bacterial strains tested, with reductions occurring of between 67 and 92%. For Acanthamoeba a reduction of 70% was seen. There were no significant differences in ocular responses to fimbrolide-coated lenses compared with controls in either the 1 month animal model or overnight human trial., Conclusions: Fimbrolide-coated lenses show promise as an antibacterial and anti-acanthamoebal coating on contact lenses and appear to be safe when worn on the eye in an animal model.

A molybdate-reducing bacterium has been locally isolated. The bacterium reduces molybdate or Mo(6+) to molybdenum blue (molybdate oxidation states of between 5+ and 6+). Different carbon sources such as acetate, formate, glycerol, citric acid, lactose, fructose, glucose, mannitol, tartarate, maltose, sucrose, and starch were used at an initial concentration of 0.2% (w/v) in low phosphate media to study their effect on the molybdate reduction efficiency of bacterium. All of the carbon sources supported cellular growth, but only sucrose, maltose, glucose, and glycerol (in decreasing order) supported molybdate reduction after 24 h of incubation. Optimum concentration of sucrose for molybdate reduction is 1.0% (w/v) after 24 h of static incubation. Ammonium sulfate, ammonium chloride, valine, OH-proline, glutamic acid, and alanine (in the order of decreasing efficiency) supported molybdate reduction with ammonium sulfate giving the highest amount of molybdenum blue after 24 h of incubation at 0.3% (w/v). The optimum molybdate concentration that supports molybdate reduction is between 15 and 25 mM. Molybdate reduction is optimum at 35 degrees C. Phosphate at concentrations higher than 5 mM strongly inhibits molybdate reduction. The molybdenum blue produced from cellular reduction exhibits a unique absorption spectrum with a maximum peak at 865 nm and a shoulder at 700 nm. The isolate was tentatively identified as Serratia marcescens Strain Dr.Y6 based on carbon utilization profiles using Biolog GN plates and partial 16s rDNA molecular phylogeny.

By secretion and detection of a series of signaling molecules, bacteria are able to coordinate gene expression as a community, to regulate a variety of important phenotypes, from virulence factor production to biofilm formation to symbiosis related behaviours such as bioluminescence. This widespread signaling mechanism is called quorum sensing. There are several quorum sensing systems described in Serratia. Serratia marcescens AS-1, isolated from soil, had the LuxI/LuxR homologues called SpnI/SpnR. S. marcescens AS-1 produced two kinds of N-acyl-L-homoserine lactones, N-hexanoyl-L-homoserine lactone and N-(3-oxohexanoyl)-L-homoserine lactone as signal molecules, which involved in quorum sensing to control the gene expression in response to increased cell density. By gene replacement method, the spnR mutant was constructed, named S. marcescens AS-1R. SpnR acted as a negative regulator for the production of prodigiosin, swarming motility and biofilm formation, which were regulated by quorum sensing. Halogenated furanone, known as a natural inhibitor of quorum sensing, could effectively inhibit the quorum sensing of S. marcescens AS-1 but without interrupting AHL-SpnR interaction. All results will be helpful to understand the mechanisms of halogenated furanone inhibition on quorum sensing and the potential application of halogenated furanone in effectively preventing infection disease caused by Serratia strains.

The aim of this study was to characterize a novel extended-spectrum beta-lactamase that belongs to the TEM family, the TEM-149 enzyme, and that was isolated from the urine of two hospitalized patients from different hospitals in southern Italy. The peculiarity of this enzyme was the finding of a valine residue at position 240. The array of amino acid substitutions found in TEM-149 was as follows: E104K, R164S, M182T, and E240V. A reversion of a threonine residue at position 182 was also performed to create a new mutant, TEM-149 T182M, in order to assess the contribution of this substitution on the kinetic profile and the stability of TEM-149. The bla TEM-149 and bla TEM-149/T182M genes were cloned into pBC-SK, and the corresponding enzymes were purified from recombinant Escherichia coli HB101 by the same procedure. Both enzymes hydrolyzed all beta-lactams tested, with a preference for ceftazidime, which was found to be the best substrate. By comparison of the kinetic parameters of the TEM-149 and the TEM-149 T182M enzymes, a reduction of the catalytic efficiency for the TEM-149 T182M mutant was observed against all substrates tested except benzylpenicillin, cefotaxime, and aztreonam. Tazobactam, clavulanic acid, and sulbactam were good inhibitors of the TEM-149 beta-lactamase.

We cloned a gene responsible for multidrug resistance from chromosomal DNA of Serratia marcescens, and determined the nucleotide sequence. We designated the gene as ssmE. The deduced amino acid sequence of SsmE showed high similarity with the small multidrug resistance (SMR)-type multidrug efflux pumps. Cells of Escherichia coli KAM32, a drug hyper-susceptible mutant, transformed with a plasmid pESM437 carrying the ssmE gene showed elevated minimum inhibitory concentrations of structurally unrelated antimicrobial agents. E. coli KAM32/pESM437 showed elevated energy dependent efflux of ethidium. Reverse transcriptase polymerase chain reaction (RT-PCR) analysis revealed that ssmE was expressed in cells of S. marcescens.

The structural and spectroscopic properties of novel five-coordinated dimeric-Cu(II) system have been investigated. The biocidal activities of all eight compounds, ligands, cupric nitrate and standard drugs against six bacteria and three fungi were determined. The DNA interaction activity of complexes was studied using spectrophotometry and electrophoresis. The superoxide dismutase (SOD)-like activity of the complexes was compared with previously reported monomeric- and dimeric copper complexes. The results support the five-coordinated dimeric square pyramidal geometry for the quinolone-Cu(II) system.

Serratia marcescens possesses two functional TonB paralogs, TonB(Sm) and HasB, for energizing TonB-dependent transport receptors (TBDT). Previous work had shown that HasB is specific to heme uptake in the natural host and in Escherichia coli expressing the S. marcescens TBDT receptor HasR, whereas the S. marcescens TonB and E. coli TonB proteins function equally well with various TBDT receptors for heme and siderophores. This has raised the question of the target of this specificity. HasB could be specific either to heme TBDT receptors or only to HasR. To resolve this question, we have cloned in E. coli another S. marcescens heme receptor, HemR, and we show here that this receptor is TonB dependent and does not work with HasB. This demonstrates that HasB is not dedicated to heme TBDT receptors but rather forms a specific pair with HasR. This is the first reported case of a specific TonB protein working with only one TBDT receptor in one given species. We discuss the occurrence, possible molecular mechanisms, and selective advantages of such dedicated TonB paralogs.

Results are presented that demonstrate the successful use of live bacteria as mechanical actuators in microfabricated fluid systems. The flow deposition of bacteria is used to create a motile bacterial carpet that can generate local fluid motion inside a microfabricated system. By tracking the motion of tracer particles, we demonstrate that the bacterial cells that comprise the carpet self-organize, generating a collective fluid motion that can pump fluid autonomously through a microfabricated channel at speeds as high as 25 microm s(-1). The pumping performance of the system can also be augmented by changing the chemical environment. The addition of glucose to the working buffer raises the metabolic activity of the bacterial carpet, resulting in increased pumping performance. The performance of the bacterial pump is also shown to be strongly influenced by the global geometry of the pump, with narrower channels achieving a higher pumping velocity with a faster rise time.

Background: Some clinical isolates of Serratia marcescens showed high-level resistance to expanded-spectrum cephalosporins alone and in combination with beta-lactamase inhibitor, but the beta-lactamase extracted from these strains was sensitive to the inhibitors. This study examines the possible mechanisms responsible for the discrepancy., Methods and Results: Three clinical isolates of S. marcescens bore the bla(TEM) gene coded on a plasmid. This was confirmed by detection of the bla gene using PCR analysis and by transferring resistance determinants to Escherichia coli via conjugation and transformation. All of the E. coli transconjugants and transformants acquired a similar level of resistance to penicillins and narrow-spectrum cephalosporins, and showed the reduced susceptibility to expanded-spectrum cephalosporins alone and in combination with clavulanate. As a result of the highly constitutive expression of the TEM gene, up to 247-690 U of beta-lactamase were produced by 10(10) cells of wild-type S. marcescens and the transconjugants and transformants. In the presence of 0.24 U/ml of TEM enzyme, the minimum inhibition concentrations of cefotaxime against E. coli ATCC 25922 increased from 0.125 to 512 microg/ml. The TEM-type beta-lactamase extracted from these strains was sensitive to clavulanate, and 62.2-92.1% of its activity was inhibited after preincubation with 0.1 mM clavulanate., Conclusion: The TEM-type beta-lactamase plays a critical role in the resistance of S. marcescens to beta-lactams, and the hyperproduction of inhibitor-susceptible TEM beta-lactamase is responsible for the resistance to beta-lactam-beta-lactamase inhibitor combinations., ((c) 2007 S. Karger AG, Basel.)

Serratia marcescens is a frequent nosocomial isolate and is associated with a variety of clinical sources, including blood, urine and sputum, and can cause significant infection. Infections can be difficult to treat due to its resistance to a variety of antimicrobial agents. An investigation of a population of 30 clinical strains revealed the presence of a class 2 integron among nine of the isolates, which represents the first isolation of this integron in Serratia species. This integron contained the gene cassettes dfrA1, sat1 and aadA1, conferring resistance to trimethoprim, streptothricin and streptomycin/ spectinomycin, respectively. One of these isolates also carried a class 1 integron identified by sequence analysis as containing the open reading frames aacC1 (encoding gentamicin resistance), ORFX, ORFY and aadA1. Polymerase chain reaction analysis confirmed the presence of the qac epsilon delta1 and sul1 markers, which are common among class 1 integrons.

In Escherichia coli the process of spontaneous zygogenesis (Z-mating), i.e. complete genetic mixing in the absence of a conjugative plasmid, was investigated further. Spontaneous-zygogenesis-promoting (Szp+) cells displayed strong clustering with each other and with ordinary F* cells in the optimal cell density range for Z-mating. When induced to rounding by the drug mecillinam, they aggregated into large, dense, stainable syncytium-like cells leaving giant ghosts upon lysis. In Z-mating mixtures of mecillinam-treated cells, these giant cells co-purified with mating products as other cells died. Giant cells recovering from mecillinam treatment yielded monstrous, branching forms, whereas non-Szp+ coccal cells reverted to rods in one step, and some 29% of the colonies formed were identified as deriving from entities possessing two distinct genomes. Z-mating was examined between E. coli and a distantly related Serratia marcescens strain. In the presence of calcium, mecillinam-rounded cells of a stable non-complementing diploid hybrid with the E. coli phenotype segregated normally dividing cells of the Serratia form.

Serratia marcescens is a nosocomial agent with a natural resistance to a broad spectrum of antibiotics, making the treatment of its infections very challenging. This study examines the influence of salicylate, sucrose, temperature, and pH variability on membrane permeability and susceptibility of S. marcescens to norfloxacin (hydrophilic fluoroquinolone) and nalidixic acid (hydrophobic quinolone). Resistance of wild-type S. marcescens UOC-67 (ATCC 13880) to norfloxacin and nalidixic acid was assessed by minimal inhibitory concentration (MIC) assays after growth in the presence of various concentrations of sucrose and salicylate and different temperatures and pH values. Norfloxacin and nalidixic acid accumulation was determined in the absence and presence of (i) carbonyl cyanide m-chlorophenylhydrazone (CCCP), a proton-motive-force collapser, and (ii) Phe-Arg beta-naphthylamide (PAbetaN), an efflux pump inhibitor. Accumulation of norfloxacin decreased when S. marcescens was grown in high concentrations of salicylate (8 mmol/L) and sucrose (10% m/v), at high temperature (42 degrees C), and at pH 6, and it was restored in the presence of CCCP because of the collapse of proton-gradient-dependent efflux in S. marcescens. Although nalidixic acid accumulation was observed, it was not affected by salicylate, sucrose, pH, or temperature changes. In the absence of PAbetaN, and either in the presence or absence of CCCP, a plateau was reached in the nalidixic acid accumulation for all environmental conditions. With the addition of 20 mg/L PAbetaN nalidixic acid accumulation is restored for all environmental conditions, suggesting that this quinolone is recognized by a yet to be identified S. marcescens pump that does not use proton motive force as its energy source.

Serratia marcescens is an important agent in hospital infections. The aim of this paper was to compare the resistance patterns of S. marcescens strains isolated during 1 year from patients of various wards of the Institute of Transplantology. The mechanisms of beta-lactam antibiotic resistance were of especial interest. We investigated the 81 strains of S. marcescens, isolated during 2005 from patients on 3 wards and 1 clinic of the Transplantation Institute. An unusually high resistance to most antibiotics was observed among S. marcescens strains. Extended spectrum beta-lactamases (ESBLs) were probably produced by 63.2% to 84.6% of strains, depending on the ward. Additionally, about 30% of them were probably derepressed AmpC producers. The patterns of resistance indicated that at least 2 resistant clones of S. marcescens spread among the patients. One of the clones demonstrated both ESBL and derepressed AmpC production and was susceptible only to carbapenems. The second, producing ESBL, was susceptible to piperacillin/tazobactam and carbapenems. All investigated strains were resistant to nitrofurantoin. Strains of the second group were rarely susceptible to other antibiotics: aminoglycosides, ciprofloxacin, cotrimoxazole, or fosfomycin.

We investigated the molecular epidemiology of gentamicin-resistant, extended-spectrum beta-lactamase (ESBL)-producing Klebsiella pneumoniae and Serratia marcescens, and risk factors associated with their acquisition in a neonatal intensive care unit (NICU) of a university hospital in Italy. During the study period (April-November 2004), S. marcescens was responsible for six infections and 31 colonisations, while K. pneumoniae was responsible for six infections and 103 colonisations. Concurrent isolation of both organisms occurred in 24 neonates. Molecular typing identified one major pulsed-field gel electrophoresis pattern each for S. marcescens and K. pneumoniae strains isolated during the study period. An 80 kb plasmid containing bla(SHV-12), bla(TEM-1) and aac(6')-Ib genes, isolated from both S. marcescens and K. pneumoniae strains, and showing identical restriction profiles, transferred resistance to third-generation cephalosporins to a previously susceptible Escherichia coli host. Birthweight, gestational age and use of invasive devices were significantly associated with S. marcescens and K. pneumoniae acquisition on univariate analysis, while empiric antimicrobial treatment with ampicillin and gentamicin, and duration of hospital stay, proved to be the only independent risk factors. In conclusion, conjugal plasmid transfer and empiric antimicrobial therapy with ampicillin and gentamicin might have contributed to the selection and spread of gentamicin-resistant ESBL-producing Enterobacteriaceae in the NICU.

Quorum sensing is a regulatory system for controlling gene expression in response to increasing cell density. N-Acylhomoserine lactone (AHL) is produced by gram-negative bacteria, which use it as a quorum-sensing signal molecule. Serratia marcescens is a gram-negative opportunistic pathogen which is responsible for an increasing number of serious nosocomial infections. S. marcescens AS-1 produces N-hexanoyl homoserine lactone (C(6)-HSL) and N-(3-oxohexanoyl) homoserine lactone and regulates prodigiosin production, swarming motility, and biofilm formation by AHL-mediated quorum sensing. We synthesized a series of N-acyl cyclopentylamides with acyl chain lengths ranging from 4 to 12 and estimated their inhibitory effects on prodigiosin production in AS-1. One of these molecules, N-nonanoyl-cyclopentylamide (C(9)-CPA), had a strong inhibitory effect on prodigiosin production. C(9)-CPA also inhibited the swarming motility and biofilm formation of AS-1. A competition assay revealed that C(9)-CPA was able to inhibit quorum sensing at four times the concentration of exogenous C(6)-HSL and was more effective than the previously reported halogenated furanone. Our results demonstrated that C(9)-CPA was an effective quorum-sensing inhibitor for S. marcescens AS-1.

Purpose: The Antimicrobial Resistance Management Program (ARMP) was established in 1997 at the University of Florida as an ongoing project to document trends in antimicrobial susceptibility patterns in inpatient/outpatient isolates and track resistance that may occur with specific antibiotic use., Methods: Institutions are enrolled at no charge and provide a minimum of 3 years of antibiogram/sensitivity report data, which are reviewed to create a customized analysis of antimicrobial susceptibility trends benchmarked against national/regional comparators. The data, in a HIPAA-compliant non-identifying format, comprise a national aggregate database of 28.4 million isolates from 358 institutions. This database was interrogated to determine resistance rates for eleven hospitals in Puerto Rico from 1998-2003 and, as comparators, those in the database from the State of Florida and all U.S. institutions., Results: Between 1996-2003, data on 328,837 isolates collected from 11 hospitals throughout Puerto Rico, 5,388,897 isolates from 46 institutions in Florida, and 24,951,098 isolates from 358 U.S. institutions for the following organisms (number of antibiotics tested against) were reviewed for susceptibility: coagulase-negative staphylococci (14)/Staphylococcus epidermidis (18), Enterococcus faecalis (7), Enterococcus faecium (5), Enterococcus species (4), Escherichia coli (24), Klebsiella pneumoniae (24), Proteus mirabilis (22), Pseudomonas aeruginosa (14), Serratia marcescens (22), Staphylococcus aureus (23), and Streptococcus pneumoniae (9). Antimicrobial resistance in Puerto Rico varied organism to organism from that observed in Florida and nationally., Conclusions: This first broad analysis of antimicrobial resistance in Puerto Rico provides important baseline data, both for sentinel surveillance programs and for determining strategies for intervention.

The bla(TEM-1) beta-lactamase gene has become widespread due to the selective pressure of beta-lactam use and its stable maintenance on transferable DNA elements. In contrast, bla(SME-1) is rarely isolated and is confined to the chromosome of carbapenem-resistant Serratia marcescens strains. Dissemination of bla(SME-1) via transfer to a mobile DNA element could hinder the use of carbapenems. In this study, bla(SME-1) was determined to impart a fitness cost upon Escherichia coli in multiple genetic contexts and assays. Genetic screens and designed SME-1 mutants were utilized to identify the source of this fitness cost. These experiments established that the SME-1 protein was required for the fitness cost but also that the enzyme activity of SME-1 was not associated with the fitness cost. The genetic screens suggested that the SME-1 signal sequence was involved in the fitness cost. Consistent with these findings, exchange of the SME-1 signal sequence for the TEM-1 signal sequence alleviated the fitness cost while replacing the TEM-1 signal sequence with the SME-1 signal sequence imparted a fitness cost to TEM-1 beta-lactamase. Taken together, these results suggest that fitness costs associated with some beta-lactamases may limit their dissemination.

Purpose: To compare the bacterial susceptibility and corneal epithelial toxicity of levofloxacin and moxifloxacin in the human corneal epithelial cells (HCECs)., Methods: We used 2 types of strains, ie, American Type Culture Collection strains and resistant strains. The former included Staphylococcus aureus, coagulase-negative staphylococci, Pseudomonas aeruginosa, and Serratia marcescens, The latter were methicillin-resistant Staphylococcus aureus; methicillin-resistant, coagulase-negative Staphylococcus sp.; and ciprofloxacin-resistant P. aeruginosa. The HCECs were incubated with each bacterial population for 1 hour and exposed to both antibiotics for 1 hour. The colony-forming units of viable bacteria per well were expressed as base 10 logarithms. To determine corneal epithelial toxicity, we exposed the HCECs to each antibiotic agent, and the viable epithelial cells were quantified by the MTT assay. We also observed the wound healing rate of injured HCECs cultured in each antibiotic agent for 24 hours., Results: In bacterial susceptibility testing of antibiotics, levofloxacin was less effective for Serratia marcescens than moxifloxacin (P < 0.05). However, both moxifloxacin and levofloxacin showed the same efficacy against Gram-positive bacteria, P. aeruginosa, and resistant strains (P > 0.05). Moxifloxacin showed a higher toxicity than levofloxacin when the HCECs were exposed to the respective antibiotics for 2 and 24 hours (P < 0.05). The moxifloxacin inhibited the effect of wound healing in HCEC injury, but levofloxacin did not (P < 0.05)., Conclusions: There was no significant difference in antibiotic effects between moxifloxacin and levofloxacin on most bacterial strains, except for Serratia marcescens. On the other hand, levofloxacin seemed to be safer than moxifloxacin in HCECs.

Serratia marcescens is a nosocomial bacterium with natural resistance to a broad spectrum of antibiotics, making treatment challenging. One factor contributing to this natural antibiotic resistance is reduced outer membrane permeability, controlled in part by OmpF and OmpC porin proteins. To investigate the direct role of these porins in the diffusion of antibiotics across the outer membrane, we have created an ompF-ompC porin-deficient strain of S. marcescens. A considerable similarity between the S. marcescens porins and those from other members of Enterobacteriaceae was detected by sequence alignment, with the exception of a change in a conserved region of the third external loop (L3) of the S. marcescens OmpC protein. Serratia marcescens OmpC has aspartic acid instead of glycine in position 112, methionine instead of aspartic acid in position 114, and glutamine in position 124, while in S. marcescens OmpF this is a glycine at position 124. To investigate the role of amino acid positions 112, 114, and 124 and how the observed changes within OmpC porin may play a part in pore permeability, 2 OmpC sites were altered in the Enterobacteriaceae consensus (D112G and M114D) through site-directed mutagenesis. Also, Q124G in OmpC, G124Q in OmpF, and double mutants of these amino acid residues were constructed. Antibiotic accumulation assays and minimal inhibitory concentrations of the strains harboring the mutated porins were performed, while liposome swelling experiments were performed on purified porins. Our results demonstrate that the amino acid at position 114 is not responsible for either antibiotic size or ionic selection, the amino acid at position 112 is responsible for size selection only, and position 124 is involved in both size and ionic selection.

Purpose: Whereas gatifloxacin, a newer fluoroquinolone, was engineered to increase its Gram-positive potency, we assessed whether it still retained significant Gram-negative activity in vivo. Specifically, we compared the efficacy of Zymar (gatifloxacin 0.3%), Ciloxan (ciprofloxacin 0.3%), and fortified tobramycin (14 mg/mL) in the treatment of experimental Gram-negative bacterial infections of Serratia marcescens (SM) and Pseudomonas aeruginosa (PA) in the New Zealand White (NZW) rabbit keratitis model., Methods: A total of 30 NZW rabbits each were intrastromally inoculated in both eyes with approximately 1000 CFU of SM and PA. By E-test, the minimum inhibitory concentrations (MICs; microg/mL) for SM were gatifloxacin (0.125), ciprofloxacin (0.047), and tobramycin (1.5), and for PA were gatifloxacin (0.125), ciprofloxacin (0.19), and tobramycin (0.5). After 16 hours, the rabbits were divided into 4 treatment groups: (1) Zymar, (2) Ciloxan, (3) fortified tobramycin, and (4) saline control. One drop was instilled in both eyes every 15 minutes for 5 doses and then every 30 minutes for 14 doses. One hour after the final treatment, the animals were euthanized, and bacterial colony counts from the corneas were determined., Results: For SM, Zymar and Ciloxan significantly reduced (P < 0.001, ANOVA) the colony counts compared with tobramycin and saline control. Zymar was more effective than Ciloxan (P < 0.001, ANOVA). For PA, all antibiotics reduced equivalently the colony counts compared with the saline control (P = 0.005, ANOVA)., Conclusions: The enhanced Gram-positive activity of gatifloxacin is not associated with any decreased Gram-negative activity in vivo. Zymar may prove useful for SM and PA keratitis.

Purpose: To compare the susceptibilities of clinical isolates of Serratia marcescens and the standard ISO ATCC 13880 strain to five contact lens multipurpose disinfection solutions (MPDSs)., Methods: Five commercially available MPDSs, containing either a polymeric biguanide or polyquaternium, were tested using ISO/CD 14729 stand-alone test for contact lens care products against four ocular isolates of S. marcescens and the strain ATCC 13880. An average log reduction in bacterial numbers at the manufacturer's minimum recommended disinfection time was determined and compared with the criteria for stand-alone disinfection products for each MPDS against each bacterial strain., Results: All the MPDSs tested met the stand-alone criteria of 3-log reduction of viable bacteria against the ATCC strain of S. marcescens. However, there was more variability in their ability to meet disinfection criteria when tested against the clinical isolates. Two of the clinical isolates were significantly more resistant to disinfection than was the recommended ISO strain (p < or = 0.034). Two of the polyquaternium-1-based disinfection solutions (solutions D and E, p < or = 0.005) were less effective overall than the other MPDSs against S. marcescens., Conclusions: The importance of strain selection for the testing of MPDSs is indicated, and the use of a single laboratory strain may be insufficient to provide assurance that the disinfection solution will be effective against clinical isolates. Furthermore, clinical isolates of S. marcescens may show increased resistance to disinfection with polyquaternium.

Resistances to tetracycline and mercury were identified in an environmental strain of Serratia marcescens isolated from a stream highly contaminated with heavy metals. As a step toward addressing the mechanisms of coselection of heavy metal and antibiotic resistances, the tetracycline resistance determinant was cloned in Escherichia coli. Within the cloned 13-kb segment, the tetracycline resistance locus was localized by deletion analysis and transposon mutagenesis. DNA sequence analysis of an 8.0-kb region revealed a novel gene [tetA(41)] that was predicted to encode a tetracycline efflux pump. Phylogenetic analysis showed that the TetA(41) protein was most closely related to the Tet(39) efflux protein of Acinetobacter spp. yet had less than 80% amino acid identity with known tetracycline efflux pumps. Adjacent to the tetA(41) gene was a divergently transcribed gene [tetR(41)] predicted to encode a tetracycline-responsive repressor protein. The tetA(41)-tetR(41) intergenic region contained putative operators for TetR(41) binding. The tetA(41) and tetR(41) promoters were analyzed using lacZ fusions, which showed that the expression of both the tetA(41) and tetR(41) genes exhibited TetR(41)-dependent regulation by subinhibitory concentrations of tetracycline. The apparent lack of plasmids in this S. marcescens strain, as well as the presence of metabolic genes adjacent to the tetracycline resistance locus, suggested that the genes were located on the S. marcescens chromosome and may have been acquired by transduction. The cloned Tet 41 determinant did not confer mercury resistance to E. coli, confirming that Tet 41 is a tetracycline-specific efflux pump rather than a multidrug transporter.

Antimicrobial susceptibilities for fosfomycin (FOM), cephalexin, cefpodoxime, cefdinir, cefditren, ampicillin, sulbactam/ampicillin, imipenem (IPM), panipenem, meropenem (MEPM), biapenem, levofloxacin (LVFX), gatifloxacin, pazufloxacin, prulifloxacin and sulfamethoxazole/trimethoprim were determined by an agar dilution method using Mueller-Hinton agar (MHA) in Escherichia coli, Klebsiella spp., Serratia marcescens, Citrobacter spp., Enterobacter spp. and Proteus mirabilis, which were isolated from patients in 2003-2004. Those for FOM were determined by the agar dilution methods using MHA containing glucose-6-phosphate (G6P) under aerobic conditions, MHA under anaerobic conditions and nutrient agar under aerobic conditions. Those for FOM, LVFX, IPM and MEPM were also determined by an Etest method. The results by the agar dilution method showed that carbapenems had good antibacterial activities in all isolates, whereas MIC ranges for other antimicrobials were broad. Our results showed that the agar dilution method for FOM using MHA containing G6P under aerobic conditions provided reliable MICs in E. coli, which agreed with data previously reported. The results by the agar dilution method for LVFX, IPM and MEPM showed the high rate of agreement compared with those by the Etest method. In E. coli, the results for FOM by the agar dilution method using MHA containing G6P showed the high rate of agreement compared with the Etest results, although the rate was affected by bacterial species and culture conditions in various ways.

We cloned a gene smfY for multidrug efflux pump from chromosomal DNA of Serratia marcescens using drug-hypersensitive Escherichia coli KAM32 as the host, and characterized the pump. E. coli KAM32/pESM42 carrying the smfY showed significantly increased MICs of various drugs including DAPI, norfloxacin, benzalkonium chloride, acriflavine and ethidium bromide, compared with the control. We also detected energy-dependent ethidium and acriflavine efflux due to the SmfY. Sequence analysis revealed that the SmfY was a multidrug efflux pump of the MF (Major Facilitator) superfamily transporters. This is the first report of a multidrug efflux pump belonging to the MF superfamily in S. marcescens.

Three commercially available microbiology identification and susceptibility testing systems were compared with regard to their ability to detect extended-spectrum beta-lactamase (ESBL) production in Enterobacteriaceae, i.e., the Phoenix Automated Microbiology System (BD Diagnostic Systems, Sparks, MD), the VITEK 2 System (bioMérieux, Marcy l'Etoile, France), and the MicroScan WalkAway-96 System (Dade Behring, Inc., West Sacramento, CA), using routine testing panels. One hundred fifty putative ESBL producers were distributed blindly to three participating laboratories. Conventional phenotypic confirmatory tests such as the disk approximation method, the CLSI double-disk synergy test, and the Etest ESBL were also evaluated. Biochemical and molecular characterization of beta-lactamases performed at an independent laboratory was used as the reference method. One hundred forty-seven isolates of Escherichia coli, Klebsiella pneumoniae, Klebsiella oxytoca, Enterobacter cloacae, Enterobacter aerogenes, Citrobacter freundii, Serratia marcescens, Proteus mirabilis, Proteus vulgaris, and Morganella morganii were investigated. Of these isolates, 85 were identified as ESBL producers by the reference method. The remaining isolates were identified as non-ESBL producers; they were either hyperproducers of their chromosomal AmpC, Koxy, or SHV enzymes or lacked any detectable beta-lactamase activity. The system with the highest sensitivity for the detection of ESBLs was the Phoenix (99%), followed by the VITEK 2 (86%) and the MicroScan (84%); however, specificity was more variable, ranging from 52% (Phoenix) to 78% (VITEK 2). The performance of the semiautomated systems differed widely with the species investigated. The sensitivities of the conventional test methods ranged from 93 to 94%. The double-disk synergy test showed the highest specificity and positive predictive value among all test methods, i.e., 97% and 98%, respectively.

Background: Serratia marcescens is an opportunistic gram-negative rod which typically infects compromised hosts., Objectives: To identify risk factors, signs, and outcomes associated with non-epidemic S marcescens bacteremia in a neonatal intensive care unit (NICU)., Methods: The records of infants with S marcescens bacteremia while in the Yale-New Haven Hospital NICU from 1980-2004 were reviewed. A matched case-control study was performed by comparing each case of S marcescens to 2 uninfected controls and 2 cases of Escherichia coli bacteremia., Results: Twenty-five sporadic cases of S marcescens bacteremia were identified. Eleven available isolates were determined to be different strains by pulse field gel electrophoresis. Infants with S marcescens bacteremia had median gestational age and birth weight of 28 weeks and 1235 grams, respectively. Compared to matched, uninfected controls, infants with S marcescens bacteremia were more likely to have had a central vascular catheter (OR = 4.33; 95% CI (1.41 to 13.36)) and surgery (OR = 5.67; 95% CI (1.81 to 17.37)), and had a higher overall mortality (44% vs 2%; OR = 38.50; 95% CI (4.57 to 324.47)). Compared to E coli matched controls, infants with S marcescens bacteremia had later onset of infection (median of 33 days of life vs 10; p<0.001), prolonged intubation (OR = 5.76; 95% CI (1.80 to 18.42)), and a higher rate of CVC (OR = 7.77; 95% CI (2.48 to 24.31)) use at the time of infection. A higher rate of meningitis (24% vs 7%; OR = 3.98; 95% CI (1.09 to 14.50)) was observed with S marcescens bacteremia compared to E coli., Conclusions: S marcescens bacteremia occurs sporadically in the NICU, primarily in premature infants requiring support apparatus late in their hospital course. Associated meningitis is common and mortality high.

Studies were carried out on the effects of different carbohydrates on the lysis of Trypanosoma cruzi, Trypanosoma rangeli and erythocytes caused by the bacteria Serratia marcescens variants SM 365 and RPH. High concentrations of d-mannose were found to protect T. cruzi and T. rangeli markedly diminishing the lysis caused by S. marcescens. However, this carbohydrate is unable to interfere with the hemolysis induced by SM 365 and RPH variants. These results showed that the trypanolytic effect induced by S. marcescens SM 365 and RPH variants is dependent on d-mannose and distinct from the hemolytic activity, strongly suggesting that bacterial fimbriae are relevant to S. marcescens in lysis of parasites.

We found that a crude extract from Salvia officinalis (sage) reduced the minimum inhibitory concentrations (MICs) of aminoglycosides in vancomycin-resistant enterococci (VRE). We isolated the effective compound from the extract and identified it as carnosol, one of diterpenoids. Carnosol showed a weak antimicrobial activity, and greatly reduced the MICs of various aminoglycosides (potentiated the antimicrobial activity of aminoglycosides) and some other types of antimicrobial agents in VRE. Carnosic acid, a related compound, showed the similar activity. The effect of carnosol and carnosic acid with gentamicin was synergistic.

In Drosophila melanogaster, seminal fluid regulates the reproductive and immune responses of mated females. Some seminal fluid proteins may provide protective functions to mated females, such as antimicrobial activity and/or stimulation of antimicrobial gene expression levels, while others appear to have negative effects, contributing to a "cost of mating." To identify seminal proteins that could participate in these phenomena, we used a systemic ectopic expression screen to test the effects on unmated females of proteins normally produced by the male accessory gland (Acps). Of the 21 ectopically expressed Acps that we tested for ability to assist in the clearance of a bacterial infection with Serratia marcescens, 3 Acps significantly reduced the bacterial counts of infected females, suggesting a protective role. Of the 23 Acps that we tested for toxicity, 3 were toxic, including one that has been implicated in the cost of mating in another study. We also tested ectopic expression females for other Acp-induced effects, but found no additional Acps that affected egg laying or receptivity upon ectopic expression.

To evaluate the roles of blaIMP and blaTEM genes in the resistance of Serratia marcescens against beta-lactams and to find the spreading ways of these genes, 19 clinical isolates of imipenem-resistant Serratia marcescens were analyzed. Six strains bore blaIMP and blaTEM genes on a single plasmid, as confirmed by transferring resistance determinants via conjugation and transformation, and by detecting bla genes with PCR analysis. The six strains showed two different genomic patterns on pulsed-field gel electrophoresis. All the transconjugants and transformants gained high-level resistance to ampicillin, cephalexin, cefoxitin and cefotaxime, and showed a reduced susceptibility to imipenem, but maintained full susceptibility to aztreonam. In addition, the expressions of blaIMP and blaTEM genes were constitutive, either in Serratia marcescens clinical isolates or in their transconjugants and transformants. These findings may explain the rapid spread of the above resistance determinants among Enterobacteriaceae via transmissible plasmids in the clinical setting.

A large outbreak of infection and colonization with multiple genera of gram-negative bacilli carrying the metallo- beta -lactamase gene bla(IMP-4) occurred in a 36-bed intensive care unit at a tertiary hospital in Australia. The organisms emerged rapidly, caused severe infections, and contributed to mortality. Controlling the spread of these organisms remains a challenge for all staff involved.

Molecular mechanisms underlying inducible cobalt and nickel resistance of a bacterial strain isolated from a Cuban serpentine deposit were investigated. This strain C-1 was assigned to Serratia marcescens by 16S rDNA analysis and DNA/DNA hybridization. Genes involved in metal resistance were identified by transposon mutagenesis followed by selection for cobalt- and nickel-sensitive derivatives. The transposon insertion causing the highest decrease in metal resistance was located in the ncrABC determinant. The predicted NcrA product was a NreB ortholog of the major facilitator protein superfamily and central for cobalt/nickel resistance in S. marcescens strain C-1. NcrA also mediated metal resistance in Escherichia coli and caused decreased accumulation of Co(II) and Ni(II) in this heterologous host. NcrB may be a regulatory protein. NcrC was a protein of the nickel-cobalt transport (NiCoT) protein family and necessary for full metal resistance in E. coli, but only when NcrA was also present. Without NcrA, NcrC caused a slight decrease in metal resistance and mediated increased accumulation of Ni(II) and Co(II). Because the cytoplasmic metal concentration can be assumed to be the result of a flow equilibrium of uptake and efflux processes, this interplay between metal uptake system NcrC and metal efflux system NcrA may contribute to nickel and cobalt resistance in this bacterium.

Present investigation is focused on antibacterial potential of aqueous infusions and aqueous decoctions of Emblica officinalis (amla) and Coriandrum sativum (coriander) against 345 bacterial isolates belonging to 6 different genera of Gram negative bacterial population isolated from urine specimens by employing well diffusion technique. Aqueous infusion and decoction of Emblica officinalis exhibited potent antibacterial activity against Escherichia coli (270), Klebsiella pneumoniae (51), K. ozaenae (3), Proteus mirabilis (5), Pseudomonas aeruginosa (10), Salmonella typhi (1), S. paratyphi A (2), S. paratyphi B (1) and Serratia marcescens (2) but did not show any antibacterial activity against Gram negative urinary pathogens.