Antibacterial activity of lemongrass (Cymbopogon citratus) oil against some selected pathogenic bacterias

ObjectiveTo find the effectiveness of essential oil of lemongrass for the treatment of pathogenic organisms.MethodsLemongrass oil was investigated for activity against Staphylococcus aureus (S. aureus), Bacillus cereus (B. cereus), Bacillus subtilis (B. subtilis), Escherichia coli (E. coli), Klebsiella pneumoniae (K. pneumoniae) and Pseudomonas aeruginosa (P. aeruginosa), using Agar Diffusion Method and Broth Dilution Method. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined by the Broth Dilution Method. The antibiotic susceptibility test against the test organisms was performed by Disc Diffusion Method.ResultsLemongrass was found effective against all the test organisms except P. aeruginosa. Gram positive organisms were found more sensitive to lemon grass oil as compared to gram negative organisms. The test organisms were found inhibited by Lemon grass oil at lower concentrations in Broth Dilution Method as compared to Agar Diffusion Method.ConclusionsThe tested organisms, particularly gram-negative organisms had shown high resistance towards different antibiotics whereas they were found to be inhibited by lemongrass oil even at lower concentration. Thus lemongrass oil is effective against drug resistant organisms. It can be suggested that use of lemongrass oil would be helpful in the treatment of infections caused by multidrug resistant organisms.     

Preliminary study on the antibacterial activity of some medicinal plants of Khuzestan (Iran)

ObjectiveTo search for antimicrobial agents among natural products.MethodsEthanolic extracts of 4 plant species, including Beta vulgaris L. (Chenopodiaceae), Amaranthus graecizans (A. graecizans) L. (Amaranthaceae), Rumex obtusifolius (R. obtusifolius) L. and Polygonum patulum (P. patulum) M.B. (Polygonaceae), were evaluated for antibacterial activity using agar disc diffusion method against some gram-positive and gram-negative bacteria [Pseudomonas aeruginosa (P. aeruginosa), Listeria monocytogenes (L. monocytogenes), Staphylococcus epidermidis (S. epidermidis), Staphylococcus aureus (S. aureus), Klebsiella pneumoniae (K. pneumoniae), Salmonella typhi (S. typhi), Bacillus cereus (B. cereus), Bacillus anthracis (B. anthracis), Escherichia coli (E. coli) and Streptococcus pyogenes (Str. pyogenes)]. These extracts were obtained from aerial parts of the used plants.ResultsThe majority of these extracts had inhibitory effect at different concentrations (0.05 g/mL, 0.10 g/mL, 0.20 g/mL and 0.40 g/mL) against above mentioned bacteria. E. coli was the most resistant strain. The highest inhibitory zone was showed by ethanolic extract of P. patulum against Str. pyogenes (28 mm) and followed by ethanolic extract of B. vulgaris against S. epidermidis (23 mm). The extract of A. graecizans didn't show inhibitory activity except at 0.40 g/mL against B. cereus. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of R. obtusifolius extract that was measured against Str. pyogenes were equal (MIC=MBC=5.00mg/mL).ConclusionThe findings of this study could also be as new source for antibiotics discovery and infection treatment.     

Multidrug resistant Psudomonas aeruginosa infections complicating surgical wounds and the potential challenges in managing post–operative wound infections: University of Calabar Teaching Hospital experience

ObjectiveTo ascertain the antimicrobial susceptibility profile of Pseudomonas aeruginosa (P. aeruginosa) recovered from surgical site infections (SSIs).MethodsThe study was retrospective in nature and was compiled for a period of five years (1st February, 2004–31st January, 2009). Data were generated from the culture of post-operative wound swab specimens by the microbiology laboratory of University of Calabar Teaching Hospital. Relevant information from the patients' records was compiled, such as age, gender, type of surgical procedure, microorganisms recovered and their antibiotic sensitivity patterns. Obtained data was analysed by using Epi Info 6 statistical software.ResultsOf the 4 533 wound swab specimens processed, 673 were culture positive and P. aeruginosa was recovered from 13.1% of the culture positive specimens with its rate of recovery decreasing with age progression (P< 0.05) but with no gender difference (P> 0.05). Most of the P. aeruginosa isolates were from general surgery wards and least from orthopaedic wards. Ofloxacin, ceftriaxone and augmentin were the most active antibiotics while ampicillin, tetracycline and cotrimoxazole were the least active antibiotics, with no antibiotic having a 100% activity against the organism.ConclusionsIn view of the high resistance displayed by P. aeruginosa recovered from SSIs, adequate antiseptic procedures should be entrenched to avoid colonization of surgical wounds by this microorganism as well as others with similar sensitivity profile. Ofloxacin, ceftriaxone and augmentin may be considered for prevention of P.aeruginosa infection.     

Detection and sequencing of plasmid encoded tetracycline resistance determinants (tetA and tetB) from food-borne Bacillus cereus isolates

ObjectiveTo investigate the detection and sequencing of plasmid encoded tetracycline resistance genes (tetA and tetB) from food-borne and standard strains of Bacillus cereus (B. cereus).MethodsA PCR was carried out to detect the tetracycline resistance genes (tetA and tetB) in food-borne B. cereus strains and the amplified products were sequenced.ResultsThe phenotypic resistance against tetracycline was observed in 39 of the 118 food-borne isolates and two reference strains (MTCC 430 and MTCC 1307) of B. cereus. Among the phenotypically resistant isolates, tetA was detected in 36 food-borne isolates and two reference strains (MTCC 430 and MTCC 1307), whereas, tetB was detected in 12 food-borne isolates and MTCC 1307 strain.ConclusionsA close association was therefore found between phenotypic resistance against tetracycline and presence of tetracycline resistance genes. The tetA and tetB gene fragments were amplified, purified and sequenced. The gene sequences of the isolates studied herein were found similar to tetA and tetB gene sequences of other bacteria available in NCBI. The occurrence of tetA and tetB genes in B. cereus indicate the horizontal transfer of antibiotic resistance determinants from other bacteria into B. cereus. The transfer of these resistant determinants to other potentially pathogenic bacteria may be a matter of great concern.     

Antibacterial activity of honey against clinical isolates of Escherichia coli,Pseudomonas aeruginosa and Salmonella enterica serovar Typhi

ObjectiveTo ascertain the potential antibacterial activity of honey against clinical isolates of Escherichia coli (E. coli), Pseudomonas aeruginosa (P. aeruginosa) and Salmonella enterica serovar Typhi (S. enterica serovar Typhi) by in vitro methods.MethodsThe partial inhibitory concentration (PIC), minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of the autoclaved honey (extracted from Apis indica hive by indigenous method) were determined for S. enterica serovar Typhi (n=8; from blood cultute), E. coli (n=5; from urine culture) and P. aeruginosa (n=5; from pus culture) isolates by in vitro methods.ResultsThe PICs of the honey tested for the isolates ranged 0.50%-1.25 % (v/v) for S. enterica serovar Typhi, 0.75%-1.50% (v/v) for E. coli and 1.00%-1.25 % (v/v) for P. aeruginosa, while the MICs ranged 1.75%–3.00% (v/v), 3.00%-3.50% (v/v) and 3.50% (v/v), respectively. The P. aeruginosa and E. coli isolates had MBC value of 4.00% (v/v); the S. enterica serovar Typhi showed MBCs in between 3.00% and 3.50% (v/v). The bactericidal activity of honey was achieved at concentration 3.00% (v/v) for S. enterica serovar Typhi and E. coli, and at 3.50% (v/v) for P. aeruginosa.ConclusionsThe excellent antibacterial activity of honey against clinical bacterial isolates indicates the usefulness of honey in clinical practice against bacterial infection.     

The effect of leaves extracts of Clitoria ternatea Linn against the fish pathogens

ObjectiveTo investigate the antimicrobial activity of Clitoria ternatea(C. ternatea) against the fish pathogens viz., Pseudomonas aeruginosa(P. aeruginosa), Escherichia coli(E. coli), Klebsiella pneumonia(K. pneumonia), Bacillus subtilis(B. subtilis), Aeromonas formican(A. formicans)s, Aeromonas hydrophila(A. hydrophila) and Streptococcus agalactiae(S. agalactiae) isolated from diseased Tilapia (Oreochromis niloticus).MethodsThe extracts of C. ternatea was tested against P. aeruginosa, E. coli, K. pneumonia, B. subtilis, A. formicans, A. hydrophila and S. agalactiae by the agar well diffusion method.ResultsDifferent extracts of C. ternatea showed inhibitory effects against P. aeruginosa, E. coli, K. pneumonia, B. subtilis, A. formicans, A. hydrophila and S. agalactiae. Ethyl acetate extracts of C. ternatea showed maximum of zone of inhibition against A. formicans (18 mm), A. hydrophilia (19 mm), B. subtilis (19 mm) and P. aeruginosa (21 mm) next to that ethanol extract of C. ternatea showed A. formicans (18 mm) and E. coli (14 mm) followed by Acetone extract showed maximum zone of inhibition S. agalactiae (19 mm) and K. pneumonia (17 mm).ConclusionsThe antimicrobial activities of all the four plant extracts are comparable and their potential as alternative in the treatment of infectious by these microorganisms was present in the fish. Susceptibility testing is conducted on isolates using drugs selected on the basis of their importance to human medicine and use in fish production.     

Antimicrobial activity and essential oils of Curcuma aeruginosa, Curcuma mangga, and Zingiber cassumunar from Malaysia

ObjectiveTo analyze the chemical composition of the essential oils of Curcuma aeruginosa (C. aeruginosa), Curcuma mangga (C. mangga), and Zingiber cassumunar (Z. cassumunar), and study their antimicrobial activity.MethodsEssential oils obtained by steam distillation were analyzed by gas chromatography-mass spectrometry (GC-MS). The antimicrobial activity of the essential oils was evaluated against four bacteria: Bacillus cereus (B. cereus), Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), and Pseudomonas aeruginosa (P. aeruginosa); and two fungi: Candida albicans (C. albicans) and Cyptococcus neoformans (C. neoformans), using disc-diffusion and broth microdilution methods.ResultsCycloisolongifolene, 8,9-dehydro formyl (35.29%) and dihydrocostunolide (22.51%) were the major compounds in C. aeruginosa oil; whereas caryophyllene oxide (18.71%) and caryophyllene (12.69%) were the major compounds in C. mangga oil; and 2,6,9,9-tetramethyl-2,6,10-cycloundecatrien-1-one (60.77%) and α-caryophyllene (23.92%) were abundant in Z. cassumunar oil. The essential oils displayed varying degrees of antimicrobial activity against all tested microorganisms. C. mangga oil had the highest and most broad-spectrum activity by inhibiting all microorganisms tested, with C. neoformans being the most sensitive microorganism by having the lowest minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) values of 0.1μL/mL. C. aeruginosa oil showed mild antimicrobial activity, whereas Z. cassumunar had very low or weak activity against the tested microorganisms.ConclusionsThe preliminary results suggest promising antimicrobial properties of C. mangga and C. aeruginosa, which may be useful for food preservation, pharmaceutical treatment and natural therapies.     

Antimicrobial activity of mangrove plant (Lumnitzera littorea)

ObjectiveTo investigate the antimicrobial activities of n-hexane, ethyl acetate and methanol extracts of the leaves of Lumnitzera littorea (L. littorea) against six human pathogenic microbes.MethodsThe antimicrobial activity was evaluated using disc diffusion and microdilution methods.ResultsThe antimicrobial activities of the crude extracts were increased with increasing the concentration. It is clear that n-hexane extract was the most effective extract. Additionally, Gram positive Bacillus cereus (B. cereus) appear to be the most sensitive strain while Pseudomonas aeruginosa (P. aeruginosa) and the yeast strains (Candida albicans (C. albicans) and Cryptococcus neoformans (C. neoformans)) appear to be resistance to the tested concentrations since no inhibition zone was observed. The inhibition of microbial growth at concentration as low as 0.04 mg/mL indicated the potent antimicrobial activity of L. littorea extracts.ConclusionsThe obtained results are considered sufficient for further study to isolate the compounds responsible for the activity and suggesting the possibility of finding potent antibacterial agents from L. littorea extracts.     

L-asparaginase production by mangrove derived Bacillus cereus MAB5: Optimization by response surface methodology

ObjectiveTo isolate marine bacteria, statistically optimize them for maximum asparaginase production.MethodsIn the present study, statistically based experimental designs were applied to maximize the production of L-asparaginase from bacterial strain of Bacillus cereus (B. cereus) MAB5 (HQ675025) isolated and identified by 16S rDNA sequencing from mangroves rhizosphere sediment.ResultsPlackett-Barman design was used to identify the interactive effect of the eight variables viz. yeast extract, soyabean meal, glucose, magnesium sulphate, KH₂PO₄, wood chips, aspargine and sodium chloride. All the variables are denoted as numerical factors and investigated at two widely spaced intervals designated as ?1 (low level) and +1 (high level). The effect of individual parameters on L-asparaginase production was calculated. Soyabean meal, aspargine, wood chips and sodium chloride were found to be the significant among eight variables. The maximum amount of L-asparaginase produced (51.54 IU/mL) from the optimized medium containing soyabean meal (6.282 8 g/L), aspargine (5.5 g/L), wood chips (1.383 8 g/L) and NaCl (4.535 4 g/L).ConclusionsThe study revealed that, it is useful to produce the maximum amount of L-asparaginase from B. cereus MAB5 for the treatment of various infections and diseases.     

Active immunization with Pseudomonas aeruginosa vaccine protects mice from secondary Pseudomonas aeruginosa challenge post-influenza virus infection

BackgroundInfluenza virus infection complicated by secondary bacterial pneumonia contributes significantly to death during seasonal or pandemic influenza. Secondary infection of Pseudomonas aeruginosa (P. aeruginosa) in influenza virus-infected patients contributes to morbidity and mortality.MethodsMice were first infected with PR8 influenza virus, followed by a secondary infection of P. aeruginosa. Body weights and survival rate of mice was monitored daily over 20 days. Bronchoalveolar lavage fluids (BALFs) and lung homogenates were harvested for measuring bacterial titers. Lung tissue section slides were stained with hematoxylin and eosin for microscopic observation. After vaccination with inactivated P. aeruginosa cells or recombinant PcrV protein, the mice were subjected to PR8 influenza virus infection followed by a secondary infection of a P. aeruginosa. The inhibition against P. aeruginosa of serum was evaluated by detecting the growth of P. aeruginosa in broth containing diluted sera.ResultsThe prior influenza infection greatly enhanced the susceptibility to secondary infection of P. aeruginosa and increased morbidity and mortality in mice. Active immunization with inactivated P. aeruginosa cells could protect mice from secondary P. aeruginosa challenge in influenza virus infected mice.ConclusionsTo develop an effective P. aeruginosa vaccine might be a promising strategy to decrease the threat of secondary P. aeruginosa infection in influenza patients.     

Metallo- β - lactamase producing nonfermentative gram-negative bacteria: an increasing clinical threat among hospitalized patients

ObjectiveTo detect and evaluate the various methods for metallo- β -lactamases (MBL) production in Pseudomonas aeruginosa (P. aeruginosa) and Acinetobacter species.MethodsA total of 109 P. aeruginosa and 85 Acinetobacter species were screened for imipenem resistance by Kirby-Bauer disc diffusion methods. Detection of MBL production was done by imipenem-EDTA combined disc test, double disc synerygy test (DDST) and imipenem-EDTA MBL E test.ResultsA total of 63 (57.8%) strains of P. aeruginosa and 46 (54.1%) strains of Acinetobacter spp. were found to be resistant to imipenem. Of the 63 imipenem resistant P. aeruginosa tested for MBL production, 44 (69.8%) were found to be positive and among 46 imipenem resistant Acinetobacter, 19 (41.3%) were shown to be the MBL producers.ConclusionsImipenem-EDTA combined disc test and MBL E test are equally effective for MBL detection in both P. aeruginosa and Acinetobacter spp., but given the cost-constraints, combined disc can be used as a convenient screening method in the clinical microbiology laboratory.     

Bioprospecting of marine Streptomycetes sp. for its antagonistic activity on MDR Pseudomonas aeruginosa and Acinetobacter baumannii isolates

ObjectiveTo assess the antimicrobial activity of the Actinobacteria bioactive secondary metabolite and characterize the drug resistance mechanisms of Pseudomonas aeruginosa (P. aeruginosa) and Acinetobacter baumannii (A. baumannii).MethodsPotential marine Actinobacteria were isolated and the crude extract was purified using thin layer chromatography, the fractions were tested for antimicrobial activity and phylogeny of the selected strain was analyzed. Isolated pathogenic strains were screened for extended spectrum beta-lactamase, mannan-binding lectin, AmpC production, efflux mechanism and polymerase chain reaction. The cephalosporin and carbapenem antibiotics were synergistically tested along with Streptomyces sp. PM49 fraction by combination disc test and double-disc synergy test. Heterogeneous susceptibility assay, minimum inhibitory concentration and expression of DnaK (Hsp70) were determined.ResultsStreptomyces sp. PM49 active fraction of R_f value 0.69 showed antimicrobial activity and an inhibitory zone of 15 to 7 mm obtained. About 34.1% of P. aeruginosa and 4.8% of A. baumannii were multiple drug resistant. AmpC β-lactamase was found in 12% of A. baumannii, efflux mechanism was putatively positive in 8/23 of P. aeruginosa and 3/20 of A. baumannii. Combination disc test and double-disc synergy test with both PM49 compound and antibiotics showed an increase in the inhibitory zone of <3 mm to 4 mm, three P. aeruginosa isolates expressed bla_IMP. Heteroresistant subcolonies grew at a frequency of 3×10⁻⁵ to 1×10⁻⁵. Stress induction analysis showed increase of DnaK during heat shock at 52 °C, the levels of protein doubled after exposure to the antibiotics.ConclusionsNovel unexplored Streptomyces spp. antimicrobial constituents can be developed as an inhibitor and can be substituted along with the available antibiotics to combat the drug resistant pathogens.     

Effect of nalidixic acid on the morphology and protein expression of Pseudomonas aeruginosa

ObjectiveTo determine the effect of nalidixic acid on the morphology and protein expression of Pseudomonas aeruginosa (P. aeruginosa).MethodsNalidixic acid solution of 1 600 μg/mL was prepared. The minimum inhibitory concentration (MIC) for P. aeruginosa was determined with tube dilution test. The effect of nalidixic acid on the morphology of P. aeruginosa was studied using light microscope and scanning electron microscope. Changes in protein profile were studied using SDS-PAGE.ResultsThe MIC of nalidixic acid was 700 μg/mL against P. aeruginosa. The exposure of P. aeruginosa to different concentrations of nalidixic acid resulted in deformation of most of the growing cells. At the concentration of 600 μg/mL most of the cells turned into elongated and adhere to each other while some of the cells were bulged. The intensity of protein bands were changed when they exposed to nalidixic acid.ConclusionsThe present findings suggest that the morphology and protein expression of P. aeruginosa is greatly affected by nalidixic acid.     

Epidemiology and in vitro activity of ceftazidime-avibactam and comparator agents against multidrug-resistant isolates of Enterobacterales and Pseudomonas aeruginosa collected in Latin America as part of the ATLAS surveillance program in 2015‒2020

IntroductionThe incidence of antimicrobial resistance is increasing in many parts of the world. The focus of this report is to examine changes in antimicrobial resistance epidemiology among clinical isolates of Enterobacterales and Pseudomonas aeruginosa collected in six Latin American countries as part of the Antimicrobial Testing Leadership and Surveillance (ATLAS) program from 2015 to 2020, with a focus on the in vitro activity of ceftazidime-avibactam against Multidrug-Resistant (MDR) isolates.MethodsNon-duplicate, clinical isolates of Enterobacterales (n = 15,215) and P. aeruginosa (n = 4,614) collected by 40 laboratories in Argentina, Brazil, Chile, Colombia, Mexico, and Venezuela, from 2015 to 2020, underwent centralized Clinical Lab Standards Institute (CLSI) broth microdilution susceptibility testing. Minimum Inhibitory Concentration (MIC) values were interpreted using 2022 CLSI breakpoints. An MDR phenotype was defined by resistance to ≥ 3 of seven sentinel agents.ResultsIn total, 23.3% of Enterobacterales and 25.1% of P. aeruginosa isolates were MDR. Annual percent MDR values for Enterobacterales were stable from 2015 to 2018 (21.3% to 23.7% year) but markedly increased in 2019 (31.5%) and 2020 (32.4%). Annual percent MDR values for P. aeruginosa were stable from 2015 to 2020 (23.0% to 27.6% year). Isolates were divided into two 3-year time-periods, 2015‒2017 and 2018‒2020, for additional analyses. For Enterobacterales, 99.3% of all isolates and 97.1% of MDR isolates from 2015‒2017 were ceftazidime-avibactam-susceptible compared to 97.2% and 89.3% of isolates, respectively, from 2018‒2020. For P. aeruginosa, 86.6% of all isolates and 53.9% of MDR isolates from 2015‒2017 were ceftazidime-avibactam-susceptible compared to 85.3% and 45.3% of isolates, respectively, from 2018‒2020. Among individual countries, Enterobacterales and P. aeruginosa collected in Venezuela showed the greatest reductions in ceftazidime-avibactam susceptibility over time.ConclusionMDR Enterobacterales increased in Latin America from 22% in 2015 to 32% in 2020 while MDR P. aeruginosa remained constant at 25%. Ceftazidime-avibactam remains highly active against all clinical isolates of both Enterobacterales (97.2% susceptible, 2018‒2020) and P. aeruginosa (85.3%), and inhibited more MDR isolates (Enterobacterales, 89.3% susceptible, 2018‒2020; P. aeruginosa, 45.3%) than carbapenems, fluoroquinolones, and aminoglycosides.     

Antibacterial activity of honey alone and in combination with Nigella sativa seeds against Pseudomonas aeruginosa infection

ObjectiveTo evaluate the in vitro activities, of three honeys sample, and Nigella sativa (N. sativa) against Pseudomonas aeruginosa (P. aeruginosa) alone and in combination.MethodsThe antibacterial test and minimum inhibition concentration (MIC) was determined by using agar well diffusion and dilution methods respectively against P. aeruginosa.ResultsThe MIC for the three varieties of honey without N. sativa against P. aeruginosa ranged between 46% and 50% (v/v). Addition of N. sativa (8%) resulted in synergistic bactericidal activity. An MIC drop was noticed with each variety and it ranged between 77.77% and 84.21%.ConclusionsThese antibacterial properties would warrant further studies on the clinical applications of N. sativa and honey against P. aeruginosa.     

Evaluation of antibacterial activity of selected medicinal plant extracts from south India against human pathogens

ObjectiveThe present study was to evaluate the antibacterial properties of 21 crude extracts from leaf and flower of Aristolochia indica (A. indica), Cassia angustifolia (C. angustifolia), leaf of Catharanthus roseus (C. roseus), Diospyros melanoxylon (D. melanoxylon), Dolichos biflorus (D. biflorus), Gymnema sylvestre (G. sylvestre) and Justicia procumbens (J. procumbens).MethodsThe ethyl acetate, acetone and methanol extract of medicinal plants were evaluated against Gram-positive Bacillus cereus (B. cereus) and Gram-negative bacteria Aeromonas hydrophila (A. hydrophila), Enterobacter aerogenes (E. aerogenes), Escherichia coli (E. coli) and Klebsiella pneumoniae (K. pneumoniae) by using well diffusion assay and minimum inhibitory concentration (MIC).ResultsThe crude plant extracts demonstrated broad spectrum activity against all bacteria. The highest inhibitory zone was observed in leaf methanol extract of A. indica against E. aerogenes (25 mm), and E. coli (20 mm), flower methanol extract of C. angustifolia against B. cereus (22 mm) and leaf acetone extract of G. sylvestre against B. cereus (22mm). The MIC values of leaf methanol extract of A. indica against K. pneumonia (22.6μg/ml), and flower extract showed against E. coli (MIC: 24.2μg/ml), leaf ethyl acetate extract of C. angustifolia against K. pneumoniae (MIC: 28.4μg/ml). Acetone ethyl acetate and methanol extracts of D. melanoxylon and D. biflorus showed the lowest MIC activity value of >30 μg/ml against all tested pathogens.ConclusionThe antibacterial activity could be confirmed in most species used in traditional medicine in South India. Nevertheless, traditional knowledge might provide some leads to elucidate potential candidates for future development of new antibiotic agents.     

Elevated exoenzyme expression by Pseudomonas aeruginosa is correlated with exacerbations of lung disease in cystic fibrosis.

Two studies were conducted to determine whether Pseudomonas aeruginosa exoenzyme expression was increased during pulmonary exacerbations of cystic fibrosis (CF) and if it was reduced by antibiotic therapy. The first study was retrospective comparing in vitro exoenzyme levels expressed by P. aeruginosa sputum isolates from seriously ill, hospitalized patients with CF to those from P. aeruginosa strains isolated from CF clinic patients who were in relatively better health. Exoenzyme values were significantly greater in P. aeruginosa strains isolated from ill, hospitalized patients than in clinic patients (P = 0.0001). In the prospective study, in vitro exoenzyme levels were measured from sputum p. aeruginosa isolates of 9 hospitalized patients with CF. Exoenzyme values were greatest in nonmucoid strains on admission (P < 0.0025), and P. aeruginosa exoenzyme expression decreased significantly during hospitalization (P < 0.0025). Deterioration in CF lung disease was accompanied by increased P. aeruginosa exoenzyme production, especially by nonmucoid strains. Antibiotic treatment during hospitalization resulted in mean improvement of % predicted forced expiratory volume in 1 sec (FEV₁) from 39 to 53% (P = 0.002). Thus, antibiotics may improve pulmonary function in patients with CF by decreasing P. aeruginosa exoenzyme expression. © 1993 Wiley-Liss, Inc.     

Activity of ceftolozane-tazobactam and comparators against gram-negative bacilli: Results from the study for monitoring antimicrobial resistance trends (SMART – Brazil; 2016–2017)

Multi-drug resistant Gram-negative bacilli (GNB) have been reported as cause of serious hospital-acquired infections worldwide. The aim of this study was to investigate the in vitro activity of ceftolozane-tazobactam compared to other agents against GNB isolated from patients admitted to Brazilian medical centers between the years 2016 and 2017. Presence of β-lactamase encoding genes was also evaluated.MethodsAntimicrobial susceptibility testing of GNB isolated from intra-abdominal (IAI), respiratory (RTI), and urinary tract infections (UTI) was performed according to ISO 227-1 guidelines and interpreted following CLSI and BrCAST/EUCAST guidelines. Qualifying Enterobacteriaceae isolates were screened for the presence of β-lactamase genes by PCR followed by DNA sequencing.Results1748 GNB collected from UTI (45.2%), IAI (25.7%) and RTI (29.1%) were evaluated. Ceftolozane-tazobactam remained highly active (94.7%) against E. coli isolates. Among K. pneumoniae, susceptibility rates were 85.9% and 85.4% for amikacin and colistin, whereas ceftolozane-tazobactam (44.1% susceptible) and carbapenems (55.2-62.2% susceptible) showed poor activity due to bla_KPC-2. Against E. cloacae amikacin, imipenem, and meropenem retained good activity (>90%). Ceftolozane-tazobactam was the most potent β-lactam agent tested against P. aeruginosa (90.9% susceptible), including ceftazidime and imipenem resistant isolates. β-lactamase encoding genes testing was carried out in 433 isolates. bla_CTX-M variants were predominant in E. coli, P. mirabilis and E. cloacae. Among the K. pneumoniae molecularly tested, most carried bla_KPC (68.5%), with all harboring bla_KPC-2, except two isolates carrying bla_KPC-3 or bla_KPC-30. ESBL encoding genes, mainly CTX-M family, were frequently detected in K. pneumoniae, plasmid-mediated AmpC were rare. A variety of PDC encoding genes were detected in P. aeruginosa isolates with five isolates harboring MBL and one KPC encoding genes.ConclusionCeftolozane-tazobactam was very active against E. coli, P. mirabilis and P. aeruginosa isolates and could constitute an excellent therapeutic option including for those isolates resistant to extended-spectrum cephalosporins and carbapenems but not producers of carbapenemases.     

Pharmacodynamic profiling of antimicrobials against Gram-negative respiratory isolates from Canadian hospitals

BACKGROUND:

With diminishing antimicrobial potency, the choice of effective empirical therapy has become more challenging. Thus, the pharmacodynamic evaluation of potential therapies is essential to identify optimal agents, doses and administration strategies.

METHODS:

Monte Carlo simulation was conducted for standard and/or prolonged infusion regimens of cefepime, ceftazidime, ceftriaxone, ciprofloxacin, doripenem, ertapenem, meropenem and piperacillin/tazobactam. Minimum inhibitory concentrations were obtained for Escherichia coli (n=64 respiratory isolates), Enterobacter cloacae (n=53), Klebsiella pneumoniae (n=75) and Pseudomonas aeruginosa (n=273) throughout Canada. The cumulative fraction of response (CFR) was calculated using bactericidal targets for each regimen against each species. A CFR ≥90% was defined as optimal.

RESULTS:

All cefepime, doripenem, ertapenem and meropenem regimens achieved optimal exposures against Enterobacteriaceae, whereas target attainment was organism and dose dependent for the other agents. Prolonged infusion doripenem and meropenem 1 g and 2 g every 8 h, along with standard infusion doripenem and meropenem 2 g every 8 h, were the only regimens to attain optimal exposures against P aeruginosa. Ciprofloxacin had the lowest CFR against P aeruginosa, followed by cefepime. Among the P aeruginosa isolates collected in the intensive care unit (ICU) compared with the wards, differences of 0.5% to 10% were noted in favour of non-ICU isolates for all agents; however, marked differences (10% to 15%) in CFR were observed for ciprofloxacin in favour of ICU isolates.

CONCLUSION:

Standard dosing of cefepime, doripenem, ertapenem and meropenem has a high likelihood of obtaining optimal pharmacodynamic indexes against these Enterobacteriaceae. For P aeruginosa, aggressive treatment with high-dose and/or prolonged infusion regimens are likely required to address the elevated resistance rates of respiratory isolates from Canada.     

Characterization of AmpC β-lactamase mutations of extensively drug-resistant Pseudomonas aeruginosa isolates that develop resistance to ceftolozane/tazobactam during therapy

IntroductionWe characterized AmpC β-lactamase mutations that resulted in ceftolozane/tazobactam resistance in extensively drug-resistant (XDR) Pseudomonas aeruginosa isolates recovered from patients treated with this agent from June 2016 to December 2018.MethodsFive pairs of ceftolozane/tazobactam susceptible/resistant P. aeruginosa XDR isolates were included among a total of 49 patients treated. Clonal relationship among isolates was first evaluated by pulsed-field gel electrophoresis (PFGE). Multilocus sequence typing (MLST) was further performed. AmpC mutations were investigated by PCR amplification of the blaPDC gene followed by sequencing.ResultsThe ST175 high-risk clone was detected in four of the pairs of isolates and the ST1182 in the remaining one. All resistant isolates showed a mutation in AmpC: T96I in two of the isolates, and E247K, G183V, and a deletion of 19 amino acids (G229–E247) in the other three. The G183V mutation had not been described before. The five isolates resistant to ceftolozane/tazobactam showed cross-resistance to ceftazidime/avibactam and lower MICs of imipenem and piperacillin/tazobactam than the susceptible isolates.ConclusionsCeftolozane/tazobactam resistance was associated in all of the cases with AmpC mutations, including a novel mutation (G183V) not previously described. There is a vital need for surveillance and characterization of emerging ceftolozane/tazobactam resistance, in order to preserve this valuable antipseudomonal agent.