Standard Disk Diffusion Method Research Articles

Antibacterial Activity of Novel Strains of Bacteriophages: An Experimental Approach.

The evolution of antibiotic resistance in bacteria has increased research in the development of alternative therapies to conventional drugs. In this study, isolated phages were characterized and antibacterial activity was determined by standard agar disc diffusion method. The phages showed maximum propagation at 37°C to 40°C and highest viability at pH 7. Sugars influenced the bacteriophage viability. Sodium chloride decreased the phage propagation. Calcium chloride and magnesium chloride increased the phage propagation up to a certain limit. SDS-PAGE analysis confirmed the presence of protein cover and showed the various bands ranging from 10 to 200 kDa. Nucleic acid analysis confirmed the presence of RNA with a size of approximately 20 kb. Transmission electron microscopy indicated that the phages belong to Siphoviridae, Leviviridae, and Podoviridae families.

Extended-Spectrum beta-lactamase production and antimicrobial susceptibility pattern of uropathogens in a Tertiary Hospital in Northwestern Nigeria

Background: Globally, there is a changing trend in the antibiotic susceptibility pattern of Gram-negative uropathogens to the conventional drugs used in the treatment of urinary tract infections due to the production of extended-spectrum beta-lactamases (ESBLs). Aim: This study aimed to determine ESBL production and antimicrobial susceptibility pattern in uropathogens. Materials and Methods: Five hundred urine samples submitted to the Medical Microbiology Department of Ahmadu Bello University Teaching Hospital from January to June 2012 were analyzed by conventional methods. Modified standardized Kirby-Bauer disc diffusion method was used for antimicrobial susceptibility testing. ESBL production by Escherichia coli and Klebsiella pneumoniae isolates was screened for using the Clinical and Laboratory Standards Institute guidelines 2012 and confirmed by the double-disc synergy tests. Results: Five hundred samples were analyzed. Of these, a total of 175 Gram-negative isolates were obtained. Isolation rates were E. coli – 56%, K. pneumoniae – 20%, Proteus mirabilis – 16%, and Pseudomonas aeruginosa – 4%. ESBL production was observed in 34.3% of all the isolates. Fifty percent (50%) of E. coli and 40% of K. pneumoniae were identified as ESBL producers and were found to be resistant to multiple antimicrobial agents. Imipenem and nitrofurantoin had sensitivity of 100% and 70%, respectively, while susceptibility to ciprofloxacin and gentamicin was low at 35% and 30%, respectively, although 96% sensitivity was observed with amikacin. ESBL producers and nonproducers showed a high level of resistance of over 95% to ampicillin, amoxycillin, and trimethoprim-sulfamethoxazole. Conclusion: This study found a high rate of ESBL production (34.4%) among uropathogens with multidrug resistance. Clinical microbiology laboratories should routinely incorporate ESBL detection methods in their laboratory procedures for continuous surveillance of multidrug-resistant isolates and antibiograms to guide empirical therapy.

Investigation of the Antidiarrheal and Antimicrobial Activities of 80% Methanolic Leaf Extract of Discopodium Penninervum (Hochst.).

Diarrhea is a major health problem throughout the world and it has become more problematic in developing countries like Ethiopia. People, in several parts of the world, use different traditional medicines for treating diarrhea and it has been reported that the roots, leaves, and flowers of various species are used for the same purpose. In Ethiopia, for instance, Discopodium Penninervum is used for the treatment of diarrhea and also to control infection. The aim of the present study was, therefore, to evaluate the in vivo antidiarrheal and in vitro antimicrobial effect of Discopodium Penninervum in mice. For the antimicrobial activity test, four standard bacteria and disc diffusion method were used, while for antidiarrheal experiment, animals had been used, which were divided into 5 groups. The first group served as negative control and was administered with vehicle (0.2-0.3ml of distilled water). Groups two (D100), three (D200), and four (D400) were administered 100, 200, and 400 mg/kg of the extract, respectively. Group five served as positive control group and was administered with either loperamide (3mg/kg) for castor oil induced diarrhea and castor oil induced enteropooling diarrhea models or atropine (1mg/kg) for charcoal meal test. Safety study was performed using a standard acute toxicity study procedure. The effect of the extract on castor oil induced diarrheal drops, onset of diarrhea, weight of faeces, small intestinal fluid accumulation, and intestinal motility was measured and analyzed using one-way ANOVA. Preliminary phytochemical screening of the leaves powder of the plant indicated the presence of various components. Inhibition of castor oil induced diarrhea was observed at all tested doses. It can be concluded that crude extracts of Discopodium Penninervum showed strong activities against diarrhea indicating that it contains some chemical constituents that possibly lead to antidiarrheal drug development.

Antimicrobial susceptibility of Neisseria gonorrhoeae isolates in Vientiane, Lao PDR.

The aim of this study was to determine the antimicrobial susceptibility of Neisseria gonorrhoeae isolates in the Lao People's Democratic Republic (Laos). A total of 165 gonococcal isolates (1.3%) were obtained from 12 281 genital samples routinely submitted to a diagnostic laboratory in Vientiane, Laos, between 2011 and 2015. Susceptibility to five antibiotics was determined by the standard disk diffusion method for 158 of the isolates. Rates of resistance to penicillin (by β-lactamase production), tetracycline and ciprofloxacin were 89.9%, 99.4% and 84.8%, respectively. All isolates were susceptible to ceftriaxone and spectinomycin. The situation in Laos is similar to that in neighbouring countries; this fortunately means that the latest Lao national guidelines for treating gonorrhoea should still be effective.

Antibiotic susceptibility of methicillin-resistant staphylococci (MRS) of food origin: A comparison of agar disc diffusion method and a commercially available miniaturized test

Methicillin-resistant staphylococci (MRS) are a major concern to public and animal health. Thirty MRS (Staphylococcus aureus, S. cohnii, S. epidermidis, S. haemolyticus, S. hominis, S. lentus, S. lugdunensis, S. sciuri, and S. xylosus) isolates from meat and poultry preparations were tested for antimicrobial susceptibility to 11 antimicrobials (belonging to seven different categories) of clinical significance using both the standard agar disc diffusion method and a commercially available miniaturized system (Sensi Test Gram-positive). It is worth stressing that 16 isolates (53.33%) exhibited an extensively drug-resistant phenotype (XDR). The average number of resistances per strain was 4.67. These results suggest that retail meat and poultry preparations are a likely vehicle for the transmission of multi-drug resistant MRS. Resistance to erythromycin was the commonest finding (76.67% of strains), followed by tobramycin, ceftazidime (66.67%), ciprofloxacin (56.67%) and fosfomycin (53.33%). An agreement (kappa coefficient) of 0.64 was found between the two testing methods. Using the agar disc diffusion as the reference method, the sensitivity, specificity and accuracy of the miniaturized test were 98.44%, 69.44% and 83.33%, respectively. Most discrepancies between the two methods were due to isolates that were susceptible according to the disc diffusion method but resistant according to the miniaturized test (false positives).

Prevalence and antibiotic resistance of Pseudomonas aeruginosa in water samples in central Italy and molecular characterization of oprD in imipenem resistant isolates.

ScopeThis study aimed to analyse the prevalence, antibiotic resistance and genetic relatedness of P. aeruginosa isolates obtained from potable and recreational water samples (n. 8,351) collected from different settings (swimming pools, n. 207; healthcare facilities, n 1,684; accommodation facilities, n. 1,518; municipal waterworks, n. 4,500; residential buildings, n. 235). Possible mechanisms underlying resistance to imipenem, with particular focus on those involving oprD-based uptake, were also explored.Methods and resultsIsolation and identification of Pseudomonas aeruginosa was performed according to the standardized procedure UNI EN ISO 16266:2008 followed by PCR confirmation. Antibiotic Susceptibility testing was conducted according to EUCAST standardized disk diffusion method. Genetic relatedness of strains was carried out by RAPD. The sequence of the oprD gene was analyzed by standard method. Fifty-three samples (0.63%) were positive for P. aeruginosa, of which 10/207 (4.83%) were from swimming pools. Five isolates (9.43%) were resistant to imipenem, one to Ticarcillin + Clavulanate, one to both Piperacillin and Ticarcillin + Clavulanate. The highest isolation rate of imipenem resistant P. aeruginosa was observed in swimming pool water. Identical RAPD profiles were found in isolates from the same location in the same year or even in different years.ConclusionsImipenem resistant strains were identified as carbapenemase-negative and resistance has been associated with inactivating mutations within the oprD gene, with a concomitant loss of porin. RAPD results proved that a water system can remain colonized by one strain for long periods and the contamination may be difficult to eradicate.This study has revealed the presence of P. aeruginosa in different water samples, including resistant strains, especially in swimming pools, and confirmed the role of porins as a contributing factor in carbapenem resistance in Gram-negative bacteria.

Urinary pathogenic bacterial profile, antibiogram of isolates and associated risk factors among pregnant women in Ambo town, Central Ethiopia: a cross-sectional study

BackgroundUrinary tract infection (UTI) is a well-known bacterial infection posing serious health problem in pregnant women. A study was conducted in pregnant women with the objectives of estimating prevalence of UTI, determining antibiogram of the bacterial isolates and assessment of the potential risk factors associated with UTI.MethodsA cross-sectional study design was used to collect 300 mid-stream urine samples from pregnant women from March 2016 to December, 2016. Samples were inoculated into Cysteine Lactose Electrolyte Deficient medium (CLED). Colonies from CLED were subcultured onto MacConkey and Blood agar plates. A standard agar disc diffusion method was used to determine antimicrobial susceptibility. Chi-square (X2) test & logistic regression were used to show associations between UTI and explanatory variables & identify the predictors of UTI, respectively.ResultsThe age of pregnant women enrolled in this study ranges from 16 to 46 years (mean ± standard deviation = 25 ± 4.7 years).The overall prevalence of UTI in pregnant women was 18.7% (95% confidence interval [CI]: 14.4–23.54%).The prevalence of symptomatic and asymptomatic UTI was 20.4% (95% CI: 13.09–29.46%) and 17.8% (95% CI: 12.70–23.83%) respectively. The predominant bacteria identified were E. coli (46.4%), S. aureus (14.3%), coagulase negative Staphylococci [CoNS] (14.3%) and Proteus species (10.6%). Majority of Gram-negative bacteria isolates were resistant to ampicillin (70%), ceftriaxon (66%), gentamicin (68%) and nitrofurantoin (64%) while 75–100% of the Gram positive isolates were resistance to ampicillin. Multiple drug resistance was observed in all of the isolates. Multivariable logistic regression revealed that the odds of acquiring UTI was 4.78 times higher in pregnant women earning monthly income of ≤500 Ethiopian Birr (21.18 USD) as compared to those earning monthly income >2001 Ethiopian Birr [84.79 USD] (P = 0.046). Similarly, the risk of UTI was higher in those who eat raw meat (OR = 2.04, 95% CI: 1.09, 3.83, P = 0.026) and had previous UTI history (OR = 2.29, 95% CI = 1.15–4.56, P = 0.019) as compared to those who eat cooked meat and had no previous history of UTI.ConclusionsThe prevalence & antimicrobial resistance of uropathogens was high. Health education, continuous surveillance of UTI and their antimicrobial resistance pattern are essential to reduce the consequence of symptomatic and asymptomatic bacteriuria and multi-drug resistant bacteria in pregnant women.

Prevalence of Antibiotic Resistance and Class 1 Integrons in Clinical and Environmental Isolates ofPseudomonas aeruginosa

Background: Many clinical isolates of Pseudomonas aeruginosa exhibit antibiotic-resistance and it is the main cause of hospital infections. Objectives: The current study aimed at evaluating the diversity of genes coding for antibiotic resistance in clinical and environmental isolates of P. aeruginosa in Hamadan, West of Iran. Methods: In the current cross sectional study, 100 clinical and 50 environmental isolates of P. aeruginosa were collected from October 2013 to May 2014. The standard disk diffusion method (SDD) was performed to test antibiotic susceptibility. All isolates were evaluated by the polymerase chain reaction (PCR) for the presence of class 1 integrons and genes encoding resistance to aminoglycoside antibiotics. The relationship between antibiotic resistance and integrons was tested by the 2-tailed chi-square (χ 2 ) or the Fisher exact tests. P values ≤ 0.05 were considered statistically significant. Results: The most common antibiotic resistance was to cotrimoxazole (61.3%). The least observed resistance was to meropenem (9.3%) and piperacillin /tazobactam (12%). The result of minimum inhibitory concentration (MIC) for amikacin showed that 20% of the strains were resistant, 15% had intermediate resistance, and 65% were sensitive. Class 1 integrons were found in 57% of the isolates. The aminoglycoside-resistance cassette included aadA (confers resistance to streptomycin and spectinomycin) and aphA1 (encoded aminoglycoside 3’-phosphotransferase) genes were the most prevalent in the isolates. Conclusions: Antibiotic resistance had a high prevalence in clinical isolates of P. aeruginosa and was commonly associated with class 1 integrons. The knowledge of drug resistance patterns helps to apply effective antibiotic treatments and appropriate infection control measures to prevent the spread of infection in hospitals.

Investigations of visible light driven Sn and Cu doped ZnO hybrid nanoparticles for photocatalytic performance and antibacterial activity

In the present work, demonstrate an effectual and facile synthesis of ZnO nanoparticles and investigations of structural, optical and photocatalytic performance are established with bi-metal (Sn and Cu) doped nanoparticles (Sn:Cu:ZnO NPs) have been successfully synthesized by microwave assisted ultra-sonicated precipitation process. The XRD pattern appearance of undoped and doped ZnO nanoparticles conserve in a hexagonal wurtzite structure. Highly efficient TEM and SAED were used to determine the particle size, shape with lattice imperfections, hence the particle size is observed as 38 nm. FTIR spectra agrees that analysis of presenting a functional group of synthesized samples. SEM images confirm that pure and Sn:Cu:ZnO NPs have a smooth surface in their morphologies and the presence of elements has been confirmed by EDX analysis. XPS analysis confirms that chemical composition of Sn:Cu:ZnO NPs. General, optical measurements of as grown Sn:Cu:ZnO NPs show the optical bandgap tunability of red shift from 3.22 eV to 2.68 eV as the Cu2+ and Sn2+ ion content have been enhancing the near-band-edge (NBE) of ZnO optical lattices. In order to understand the band structure of ZnO nanomaterials, the photoluminescence (PL) spectra at room temperature were studied and their bands appear around ∼590 nm, while this green-yellow emission suggests zinc vacancy, so it should valid for color LEDs. Chiefly, the Sn:Cu:ZnO nanoparticles has favourable photocatalyst activity in MB dye compared to pure ZnO. It completely degrades the dye after 180 min in the Sn:Cu:ZnO photocatalyst under visible-light-driven by interfacial of photo generated electron-hole pairs will enhances the charge transfer progression and its photo degradation rate is 2.6 times faster than that of undoped ZnO. Also, the photocurrent response has exposed to development of photocatalytic properties and more charge carrier ability. Further identifications of existing residues of photocatalytic process were analysed by mass spectroscopy. The antibacterial activity is well exposed towards inactivation of bacterial strain including pathogens which are S. aureus (G+) and E. coli (G−) bacteria by the standard disc diffusion method.

Characteristics of antibiotic sensitivity of Staphylococcus aureus isolated from dairy farms in Ukraine

Staphylococcus aureus is one of the most important microorganism in the process of raw milk production and has significance for people’s health as it causes dangerous microbial contamination of dairy production. Furthermore, raw milk and the environment of livestock farms may be potential vehicles for distribution of antibiotic-resistant strains of S. aureus. The aim of the present study was to establish antibiotic sensitivity profiles of S. aureus depending on its origin from dairy farms, with a special focus on methicillin-resistant isolates. A total of 165 samples were collected for investigation in the period 2014–2016 from 5 dairy farms in Ukraine. All samples were analyzed for the presence of S. aureus using the Baird Parker Agar with Egg Yolk Tellurite Emulsion. Typical staphylococcal colonies were examined morphologically and for presence of coagulase and hemolysin activities. From these, positive samples for S. aureus were 62 (37.6%): 4 (6.5%) raw milk, 17 (77.4%) swabs of udder skin, 18 (29.0%) milk from cows with subclinical mastitis and 21 (33.9%) environmental samples. The standard disk diffusion method was used to determine sensitivity of S. aureus isolates to 10 antibiotics. The antimicrobial sensitivity profiles of S. aureus isolates showed differences between them, which depends on the origin of the isolates. Our results demonstrated that most of S. aureus isolates were resistant to penicillin, oxacillin and vancomycin. Of the 62 S.aureus isolates, 20 (32.3%) and 5 (8.1%) were found to be multiresistant to 3 different antibiotics, 6 (9.8%) isolates to 4 antibiotics, 12 (19.4%) and 3 (4.8%) to 5 antibiotics (P10, OX1, VA5, L10, TE30 and P10, OX1, VA5, CIP10, TE30 respectively). All isolates resistant to penicillin and oxacillin were typed by mec A gene in PCR with two primers (MecA147-F and MecA147-R). The results show that 66.7% of these isolates yielded a mecA product. The information obtained from this study is useful for understanding the prevalence of S. aureus and its antibiotic sensitivity in dairy farms and can be useful for local and national monitoring or for designing specific control programs of methicillin- and multiresistance isolates present in the food chain of milk production.

Comparative In Vitro Activity of Ciprofloxacin and Sitafloxacin Against Neisseria gonorrheae

Background Most of Neisseria gonorrhoeae strains isolated from Thai patients are resistant to ciprofloxacin and ciprofloxacin is no longer recommended for therapy of gonococcal infection in Thailand. Sitafloxacin is a new generation of fluoroquinolones that contains in vitro activities against many bacteria that are resistant to ciprofloxacin. Sitafloxacin has a high concentration in urine. The objective of the study was to determine in vitro activity of sitafloxacin against ciprofloxacin-resistant N.gonorrheae.Methods Antimicrobial susceptibility tests for 52 strains of Neisseria gonorrhoeae isolated from patients attended Bangrak Hospital in Bangkok were performed. The tested antibiotics were ceftriaxone, cefixime, ciprofloxacin, and sitafloxacin. The minimum inhibitory concentrations (MICs) and inhibition zone diameters were determined by standard agar dilution and disk diffusion method, respectively, according to the Clinical and Laboratory Standards Institute (CLSI) 2013.ResultsAll 52 N.gonorrheae isolates were susceptible to ceftriaxone (MIC < 0.025 mg/l, zone diameter > 35mm) and cefixime (MIC < 0.025 mg/l, zone diameter > 31mm). All N. gonorrheae isolates were resistant to ciprofloxacin (MIC > 1 mg/l, zone diameter < 27 mm). The inhibition zone diameters of sitafloxacin (5 microgram disk) against 52 isolates of N. gonorrhoeae were > 41 mm in 35 isolates (67%) and between 28 and 40 mm in 17 isolates (33%). If the cut-off value of inhibition zone diameter of resistance to ciprofloxacin (<27 mm) is applied, no isolates of N. gonorrheae is considered to be resistant to sitafloxacin.Conclusion Sitafloxacin seems to be active against ciprofloxacin-resistant N. gonorrheae. A clinical study on therapy of gonococcal urethritis due to ciprofloxacin-resistant N. gonorrheae should be considered.Disclosures All authors: No reported disclosures.

Identification of Newer Antimicrobial Agents: A Study of Invitro Antibacterial and Antifungal Activities of Leaf extracts of Medicinal Plant &lt;i&gt;Aerva lanata&lt;/i&gt; (L.) Juss. ex Schult

In the era of presence and spread of infectious diseases caused by microorganisms demonstrating resistance against most antimicrobial agents routinely used in the treatment, there is a serious need of search for potential agents which can be used as antimicrobials. The plant extracts of Aerva lanata were collected and processed using standard procedures. Whatman filter papers were then impregnated with varied concentrations of plant extract and antimicrobial susceptibility testing was performed using Kirby-Bauer disk diffusion method for bacteria. The standard disk diffusion method was used to test antifungal drugs against yeasts, and non-dermatophyte filamentous fungal isolates.The ethanolic extract at a concentration of 600 µg/ mL and 900 µg/ mL showed increased antibacterial activities against Esherichia coli as compared to the standard drug tested at similar concentrations. The chloroform extracts and the ethanol extract revealed increased antibacterial activity against Klebsiella pneumoniae. The chloroform solvent extract showed similar antifungal activities as the standard drug against Candida albicans, and the H2O extract showed greater antifungal activity against Drechslera halodes as compared to the control drug tested. Antibacterial and antifungal properties of leaf extracts of Aerva lanata plant in comparison with the control drugs revealed either similar or increased activities signifying their potential for future candidates as antimicrobial agents.

Salmonella enterica subspecies enterica serovar Paratyphi B as a disease-causing agent in reptiles in the Czech Republic

The aim of this study was to describe two case studies of reptile disease, in which the primary pathogen was apparently Salmonella enterica subspecies enterica serovar Paratyphi B. Pathological examinations, sampling from different organs and cloacal swabs was performed on a dead savannah monitor (Varanus exanthematicus) and a sick green tree python (Chondropython viridis). This material was subjected to culture examination, including selective enrichment using standard methods. Typing was performed using MALDI-TOF and strains were also serologically typified. The utilisation of d-tartrate was confirmed biochemically and also using PCR. Antibiotic susceptibility was determined by the standard disc diffusion method using Mueller-Hinton agar without blood and antibiotic discs. In both cases the detected Salmonella enterica subspecies enterica serovar Paratyphi B was positive for d-tartrate and exquisitely susceptible to chloramphenicol, tetracycline, ampicillin, amoxycillin/clavulanic acid, gentamicin, ceftazidime, enrofloxacin and piperacillin.

Evaluation of direct antifungal susceptibility testing methods of Candida spp. from positive blood culture bottles.

Blood culture is the gold standard diagnostic method in candidemia in spite of long result time and low sensitivity rate. Early diagnosis is crucial for management of candidemia because a delay in treatment is related with increased mortality. We aimed to evaluate the direct applicability of antifungal susceptibility testing methods from positive blood culture bottles to save at least 24hours. Blood culture bottles were inoculated with 62 Candida isolates. Etest and broth microdilution (BMD) methods for six antifungals, disk diffusion (DD) method for two antifungals were performed, both directly from bottles and standardly. Essential agreements between direct and standard Etest methods were 87.1% for caspofungin and >90% for other antifungals, but the agreements of them with reference BMD were relatively low. Essential agreement between direct and standard BMD was >93%. Correlation between direct and standard DD methods was very high, negative correlations were observed between reference BMD and DD methods. BMD is a reference method to evaluate the antifungal susceptibility, direct application of BMD might provide reliable results at least 24hours earlier. Direct DD method may be a qualitative alternative. Direct susceptibility testing methods may be very useful to initiating the appropriate treatment on time.

Distribution of blaTEM, blaSHV, and blaCTX-M genes among ESBL-producing P. aeruginosa isolated from Qazvin and Tehran hospitals, Iran.

Pseudomonas aeruginosa is as an important opportunistic human pathogen, which is associated with several clinical infections that are usually difficult to treat because of resistance to multiple antimicrobials. The production of extendedspectrum ß-lactamases (ESBLs) is an important mechanism of ß-lactam resistance. The aims of this study were to determine the prevalence of ESBLs, antimicrobial susceptibility, and to detect the blaTEM, blaSHV, and blaCTX-M genes. In this study, carried out from March 2013 to December 2014, 266 P. aeruginosa isolates were collected from patients admitted to teaching hospitals of Qazvin and Tehran, Iran. All isolates were initially screened for ESBL production by disk diffusion method and were further confirmed using a combined disk method. Antimicrobial susceptibility of ESBL-producing isolates was determined by standard disk diffusion method. Polymerase Chain Reaction (PCR) and sequencing techniques were employed for detection of blaTEM, blaSHV, and blaCTX-M genes. In total, 262 (98.5%) P. aeruginosa isolates were nonsusceptible to the used extended spectrum cephalosporins, and, among these, 75 (28.6%) isolates were ESBL producers. Fifty-nine (78.7%) of ESBL-producing isolates showed multidrug-resistance pattern. Of 75 ESBL-positive isolates, the blaTEM-1 (26.7%) was the most common gene, followed by blaCTX-M-15 (17.3%), blaSHV-1 (6.7%), and blaSHV-12 (4%), either alone or in combination. The results of this study showed the notable prevalence of ESBLs among the clinical isolates of P. aeruginosa in Iran, indicating the urgency for the implementation of appropriate follow-up measures for infection control and proper administration of antimicrobial agents in our medical settings.

Utility of a novel chromogenic medium as a screening method in the detection of carbapenemase producing Enterobacteriaceae.

INTRODUCTION:With the emergence of multidrug resistant Gram-negative bugs, there is an urgent need for rapid detection of these resistant organisms.AIM:This study was performed to assess the utility of a novel chromogenic medium in the detection of carbapenemase producing Enterobacteriaceae from various clinical specimens.MATERIALS AND METHODS:A total of 202 isolates of Enterobacteriaceae, which were resistant to meropenem (10 μg) disc by standard disc diffusion method, were analyzed over a period of 6 months. These isolates were subjected to the modified Hodge test (MHT) and inoculated onto the chromogenic medium. Following which the results were analyzed.RESULTS:It was observed that 76.73% of the Enterobacteriaceae gave a positive result on the MHT, 18.31% were negative and 4.95% gave indeterminate result. While 88.11% produced growth on the chromogenic medium, 6.93% yielded no growth and 4.95% gave variable results. Concordance in the results of the two tests was found to be 65.34%.CONCLUSION:Enterobacteriaceae are emerging to be carbapenem resistant and are responsible for the soaring rates of Healthcare Associated Infections (HAIs), especially among critically ill patients. Hence, early detection of the same is important in controlling HAIs.

Identification of Carbapenemase-mediated Resistance among Enterobacteriaceae Bloodstream Isolates: A Molecular Study from India

Acquired resistance in carbapenem-resistant Enterobacteriaceae (CRE) conferred by carbapenemases is a major concern worldwide. Consecutive, non-duplicate isolates of Escherichia coli (EC) and Klebsiella pneumoniae from clinically diagnosed bloodstream infections were screened for the presence of carbapenem resistance by standard disk-diffusion method and minimum inhibitory concentration breakpoints using the Clinical and Laboratory Standards Institute guidelines. Carbapenemase-encoding genes were amplified by polymerase chain reaction. Of 387 isolates (214 K. pneumoniae, 173 EC) tested, 93 (24.03%) were found to be CRE. Of these, 71 (76.3%) were positive for at least one tested carbapenemase gene. The frequency of carbapenemase genes was New Delhi metallo-β-lactamse-1 (65.6%), oxacillinase (OXA)-48 (24.7%), OXA-181 (23.6%), Verona integron-encoded metallo-β-lactamase (6.4%) and K. pneumoniae carbapenemase (2.1%). Our study identified presence of carbapenemases in a large proportion of CRE isolates. Delineation of resistance mechanisms is important in view of future therapeutics concerned with the treatment of CRE and for aiding control efforts by surveillance and infection control interventions.

Molecular characterization of antibiotic-resistant Staphylococcus aureus from livestock (bovine and swine).

Aim:The aim of this study was to figure the prevalence, phenotypic and genotypic antibiotic resistance (AR) pattern of Staphylococcus aureus isolated from bovine and swine nares.Materials and Methods:Colonies with typical morphology on Baird-Parker agar supplemented with egg-yolk tellurite emulsion were selected and biochemically/genotypically identified as S. aureus. These strains were further subjected to epsilometer test for their sensitivity to various clinically important antibiotics and antibiotic susceptibility testing for amoxicillin/clavulanic acid, and double-disk diffusion testing was performed by the standard disc diffusion method following CLSI guidelines. S. aureus strains were also tested for the presence of AR genes, viz., blaZ, mecA, aacA-aphD, erm (ermA, ermB, ermC), tet (efflux genes tetK and tetL, tetM and tetO of the ribosomal protection family), and vanA.Results:The nasal cavities of 17 out of 47 randomly selected bovine and 20 out of 28 randomly selected swine were positive for S. aureus, representing the prevalence of 36.2% (95% confidence interval [CI]: 22.5-49.9) and 71.4% (95% CI: 54.7-88.1), respectively. Most of the S. aureus strains showed higher resistance to penicillin (94.6%, minimal inhibitory concentration [MIC] ≥1.5 µg/ml) followed by ciprofloxacin (56.7%, MIC ≥32 µg/ml) and tetracycline (18.9%, MIC ≥32 µg/ml). About 10-15% of the strains were resistant to gentamicin (MIC 16 µg/ml) and oxacillin (MIC 6-8 µg/ml). None of the strains were resistant to vancomycin (MIC 0.25-1.5 µg/ml). In this study, 32.4% strains were resistant to three or more than three antibiotics and prevalence of this multi-drug resistant S. aureus was 45% (95%CI: 26.6-63.4) and 17.6% (95%CI: 6.7-28.5) in swine and bovine nasal samples, respectively. Four strains from pigs were borderline oxacillin-resistant S. aureus MIC 6-8 µg/ml, but none were mecA positive. Two of these strains were β-lactamase hyperproducers. Among the resistance genes blaZ, tetK, tetL, tetM, ermB, and aacA-aphD were found.Conclusion:Our results demonstrated the absence of mecA and pvl gene, but the presence of multi-drug resistant S. aureus in the nares of healthy animals which has a potential to spread in a community.

Prevalence, antimicrobial susceptibility and multiplex PCR-serotyping of Listeria monocytogenes isolated from humans, foods and livestock in Iran.

Listeria monocytogenes is a foodborne pathogen causing listeriosis, which potentially affects all individuals, especially pregnant women and immunocompromised persons. The present study investigated the prevalence, antimicrobial susceptibility and serotypes distribution of the isolated L.monocytogenes from Iran. Twenty two (4.97%) of 442 human, food and livestock samples were found to be positive for L.monocytogenes. L.monocytogenes was identified in 8.8% of 125 human samples, 2.99% of 267 food and 6% of 50 livestock samples. The standard disk diffusion method and minimum inhibitory concentration (MIC) assay were used for antimicrobial susceptibility testing and multiplex PCR for serotyping. Among the 22 isolates tested, 6 (27.2%) displayed resistance to penicillin G, with all of the isolates and 2 (9%) of them showing intermediate susceptibility to clindamycin and rifampicin, respectively. According to the MIC assay, the rate of resistance to penicillin G was the same as that of disk diffusion method, but 16 (72.7%) of isolates showed intermediate susceptibility to clindamycin using E-test. In the multiplex PCR, 19 (86.4%) of isolates belonged to serotype 1/2c or 3c and the remaining 3 isolates were identified as (4b, 4d or 4e) and (1/2a or 3a), respectively. The occurrence of resistance to penicillin G, which can be used in the treatment of listeriosis, is very alarming and more prevalence of 1/2c serotype, in comparison to 3 other important ones (1/2a, 1/2b and 4b), in Iran has been reported for the first time. To the best of our knowledge, this is the first study showing the distribution of various serogroups of L.monocytogenes from human and livestock in Iran.

Urinary Tract Infections in Patients with Type 1 and Type 2 Diabetes: Etiology, Resistance to Antibacterial Chemicals and Virulence Features

One of the most frequent chronic complications occurred in diabetes patients are the urinary tract infections (UTIs). This study aimed to investigate the incidence of UTIs in a cohort of 93 (47 males: 46 females) diabetic patients, the prevalence of different microbial species involved and their virulence and antibiotic resistance profiles. The identification of the uropathogenic strains in the positive urine samples was performed using conventional methods and API tests. After identification, the antibiotic susceptibility profiles were established by the standardized disk diffusion method and double disk diffusion test was performed for the confirmation of ESBL and inducible AmpC b �lactamase phenotypes. The isolated strains were tested for the production of different cell associated and soluble virulence factors, i.e.: bacterial adherence to cellular substrata (HeLa cells), hemolysins (hemolysis spot, CAMP-like), amylase, caseinase, aesculin hydrolysis, DNA-ase, lipase and lecithinase. In the analyzed group, the total prevalence of UTIs was of 46%, a higher incidence being observed in the female patients (64%). Similar to other studies, the etiology of UTI in the investigated diabetes patients was dominated by E. coli, followed by Klebsiella sp. strains. The isolated strains preserved good susceptibility rates to quinolones and aminoglycosides and revealed important virulence features, related to their capacity to colonize the cellular substratum and to produce soluble virulence factors involved in persistence, colonization and progression of the infectious process. The high percentage of beta-lactam resistant strains (including carbapenem-resistant ones) requires careful surveillance of the dynamics of susceptibility profiles for limiting the emergence of these strains in community.