Antibiotic Susceptibility Test Results Research Articles

Prevalence and antibiotic resistance pattern of urinary tract bacterial infections in Dessie area, North-East Ethiopia.

BackgroundDifferent studies have indicated that urinary tract infections frequently occur in both community and hospital environments and are of the most common bacterial infections in humans. the outcomes of urinary tract infections are increased hospitalization, increased direct patient costs and mortality. In Dessie, the prevalence of the commmon pathogens and antibiotic susceptibility pattern is not well studied sofar. Thus, the aim of this study is to address these gaps in the study area.MethodsRetrospective study was conducted in Dessie regional health reseacrh laboratory from January 1-March 31, 2012. All culture and antibiotic susceptibility test results of patients’ diagnosed with UTI from September 2002 to September 2011 G.C were included in the study. Data were abstracted using structured questionnaires and finally, entered into SPSS Windows version 16.0, and descriptive statistics was generated to meet the study objective.ResultsDuring the last ten years 680 (27.35%) bacteria were isolated in the regional laboratory. The most commonly isolated were E. coli 410 (60.29%), Pseudomonas species 59 (8.68%), Proteus species 53 (7.79%), S. aurous 50 (7.35%) and Klebsiella species 40 (5.88%). The E.coli were susceptible to Nitrofurantoin 43 (89.6%), furantoin 124 (87.3%), Nalidixic acid 91 (86.7%), kanamycin 116 (80%) & ciprofloxacin 66 (71.7%) but were almost resistant to Ampicillin, tetracycline, & trimethoprim-sulfamethoxazole. Similarly Pseudomonas and proteus species were resistant to almost all antibiotics except Gentamycin.ConclusionThe E.coli, pseudomonas and proteus species were the commonly isolated bacteria in the regional health research laboratory. A majority of isolated bacterial microbes were resistant to antibiotics commonly used in clinical practices and generally available in the local economy without prescription. Culture results are necessary before initiating antibiotics.

PO-0799 Bacteria Isolated From The Urine Samples Of Children And Their Antibiotic Susceptibilities

The aim of this study was to identify the bacteria isolated from urine samples and to investigate their antibiotic suscep-tibilities in children aged 0–14 years. Urine samples of 1820 patients who referred to our hospital and had urinary tract infection symptoms were studied in order to evaluate culture and antibiotic susceptibility testing results. All urine samples were inoculated on eosin methylene blue (EMB) and 5% blood agars. Bacterial isolates were identified by conventional met-hods. Antibiotic susceptibility testing was performed by disk diffusion method. The bacteria were isolated in 198 (9.2%) of 1820 urine samples. The most frequently isolated bacteria (69.4%) were Escherichia coli. Enterococcus spp. (12.7%), Proteus spp. (6.1%), Klebsiella spp. (4.3%), Enterobacter spp. (5.9%) and coagulase-negative staphylococci (CNS) (1.5%) followed respectively. While all E.coli, Proteus spp., Klebsiella spp., and Enterobacter spp. isolates were susceptible to amikacin, gentamicin, and imipenem, sensitivity of the ampicillin (68.5%), and the trimethoprim/sulfa-methoxazole (77.6%) were the lowest. All Enterococcus spp. isolates were susceptible to linezolid and vancomycin, resistan-ce ratios aganist nitrofurantoin, penicillin, and erythromycin were 5.6%, 19.0%, and 27.3% respectively. Although antibiotic susceptibility rates among our hospital’s patient population were higher than other studies, it should be remembered that culture and antimicrobial susceptibility testing may be beneficial to help choosing narrow-spectrum antibiotics and to prevent development of resistance.

PO-0800 Bacteria Isolated From The Urine Samples Of Children And Their Antibiotic Susceptibilities

The aim of this study was to identify the bacteria isolated from urine samples and to investigate their antibiotic suscep-tibilities in children aged 0–14 years. Urine samples of 1820 patients who referred to our hospital and had urinary tract infection symptoms were studied in order to evaluate culture and antibiotic susceptibility testing results. All urine samples were inoculated on eosin methylene blue (EMB) and 5% blood agars. Bacterial isolates were identified by conventional met-hods. Antibiotic susceptibility testing was performed by disk diffusion method. The bacteria were isolated in 198 (9.2%) of 1820 urine samples. The most frequently isolated bacteria (69.4%) were Escherichia coli. Enterococcus spp. (12.7%), Proteus spp. (6.1%), Klebsiella spp. (4.3%), Enterobacter spp. (5.9%) and coagulase-negative staphylococci (CNS) (1.5%) followed respectively. While all E.coli, Proteus spp., Klebsiella spp., and Enterobacter spp. isolates were susceptible to amikacin, gentamicin, and imipenem, sensitivity of the ampicillin (68.5%), and the trimethoprim/sulfa-methoxazole (77.6%) were the lowest. All Enterococcus spp. isolates were susceptible to linezolid and vancomycin, resistan-ce ratios aganist nitrofurantoin, penicillin, and erythromycin were 5.6%, 19.0%, and 27.3% respectively. Although antibiotic susceptibility rates among our hospital’s patient population were higher than other studies, it should be remembered that culture and antimicrobial susceptibility testing may be beneficial to help choosing narrow-spectrum antibiotics and to prevent development of resistance.

Évolution des méningites bactériennes de l’enfant en France sous l’effet des vaccinations

For the past 20 years, three vaccines against the three main bacterial species implicated in meningitis in children have been included in the French vaccine calendar: Haemophilus influenzae b in 1993, 7-valent pneumococcal conjugate vaccine (PCV7) in 2003 (replaced by 13-valent in 2010) and Neisseria meningitidis C in 2009. The French active surveillance network from the GPIP/ACTIV monitors the change in the epidemiological, clinical, and biological features of bacterial meningitis due to vaccine use. Over a 12-year period, 233 pediatric wards working with 168 microbiology departments throughout France were asked to report all cases of bacterial meningitis. From January 2001 to December 2012, 4808 bacterial meningitis cases were reported. Between 2001 and 2012, the number of pneumococcal meningitis (PM) cases decreased by 23.4%, and by 32.2% for children less than 2 years old. During this period, the proportion of cases attributable to PCV7 and six additional PCV13 types decreased from 63.3% to 8.1% and 83.7% to 32.4%, respectively. In 2012, the main vaccine types (accounting for 25.8% of cases) were 7F (12.2%), 19A (6.8%), and 19F (6.8%), and the most frequent non-vaccine types were 12F (14.9%), 24F (14.9%), 15B/C (6.8%), 22F (6.8%), and 10A (5.4%). In 2012, the rate of strains with decreased susceptibility to cefotaxime/ceftriaxone (MIC>0.5 μg/mL) represented less than 3% of cases, with no identified resistant strain since 2010 (MIC>2 μg/mL). Between 2001 (n=67) and 2012 (n=9), the number of NmC meningitis cases decreased by 87%. With more than 4800 bacterial meningitis cases reported in 12 years, this nationwide survey provides essential information on the microbiological and clinical characteristics of bacterial meningitis (epidemiology or resistance data). These results could lead to changing antibiotic treatment of pneumococcal meningitis before the results of antibiotic susceptibility tests.

Plasmodium falciparum and Salmonella Typhi Co-Infection: A Case Report

Malaria and salmonella infections are endemic especially in developing countries, however malaria and salmonella co-infection is a rare entity with high mortality. The basic mechanism in developing salmonella co-infection is the impaired mobilization of granulocytes through heme and heme oxygenase which are released from haemoglobin due to the breakdown of erythrocytes during malaria infection. Thus, a malaria infected person becomes more susceptible to develop infection with Salmonella spp. In this report a case with Plasmodium falciparum and Salmonella Typhi co-infection was presented. A 23-year-old male patient was admitted to hospital with the complaints of diarrhea, nausea, vomiting, abdominal pain, fatigue and fever. Laboratory findings yielded decreased number of platelets and increased ALT, AST and CRP levels. Since he had a history of working in Pakistan, malaria infection was considered in differential diagnosis, and the diagnosis was confirmed by the detection of P.falciparum trophozoites in the thick and thin blood smears. As he came from a region with chloroquine-resistant Plasmodium, quinine (3 x 650 mg) and doxycycline (2 x 100 mg/day) were started for the treatment. No erythrocytes, parasite eggs or fungal elements were seen at the stool microscopy of the patient who had diarrhoea during admission. No pathogenic microorganism growth was detected in his stool culture. The patient's blood cultures were also taken in febrile periods starting from the time of his hospitalization. A bacterial growth was observed in his blood cultures, and the isolate was identified as S. Typhi. Thus, the patient was diagnosed with P.falciparum and Salmonella Typhi coinfection. Ceftriaxone (1 x 2 g/day, 14 days) was added to the therapy according to the results of antibiotic susceptibility test. With the combined therapy (quinine, doxycycline, ceftriaxone) the fever was taken under control, his general condition improved and laboratory findings turned to normal values. However, on the fifth day of his anti-malaria therapy sudden bilateral hearing loss developed due to quinine use. Thus, the treatment was replaced with an artemisinin-based (arthemeter/lumefantrine) combination therapy. No adverse effects were detected due to artemisinin-based therapy, and the patient completely recovered. In conclusion, if a patient is diagnosed with malaria, he/she should be closely monitored in terms of having co-infections and appropriate diagnostic methods including blood cultures taken in febrile episodes should be performed.

Serotypes and antibiotic resistance of non-invasive Streptococcus pneumoniae circulating in pediatric hospitals in Moscow, Russia

Pneumococcal infections remain a major medical problem associated with high morbidity and mortality. Moreover, the resistance of Streptococcus pneumoniae to conventional antibiotics is constantly growing. The implementation of pneumococcal conjugate vaccines (PCVs) in the last decade has dramatically reduced the incidence of the vaccine type-associated invasive pneumococcal diseases in many countries. However, information on the seroepidemiology of S. pneumoniae in Russia is limited. We report the results of serotyping and antibiotic susceptibility testing performed on 863 non-invasive pneumococcal isolates collected prospectively in 2009-2013 from children (median age 3.5 years) who sought medical care at five pediatric hospitals in Moscow. The isolates were recovered from the nasopharynx (71.2%), middle ear fluid (14.3%), and lower respiratory tract specimens (13.6%). In total, we identified 45 different serotypes. The six leading serotypes (prevalence >5%) included 19F (21.7%), 6B (12.8%), 23F (10.1%), 14 (9.0%), 6A (8.4%), and 3 (7.5%). Serotype 19A isolates had a prevalence of 2.3%. The proportion of PCV-13 serotypes was 78%; the coverage by PCV-7 was 58.2% and was similar to that of PCV-10 (59.8%). The rate of multidrug-resistant pneumococci (i.e., resistant to ≥3 antimicrobials) was 22%. The majority of the multidrug-resistant isolates were serotype 6B, 14, 19A, and 19F. Penicillin non-susceptibility was displayed by 28% of the isolates. The resistance rate to erythromycin was 26%. Among the examined erythromycin-resistant strains, 54% had the erm(B) gene and 13% had the mef gene as a single resistance determinant, whereas both determinants were found in 31% of these strains. Our data predict a good coverage of the circulating S. pneumoniae by the PCVs and could be useful for evaluating the serotype distribution in support of the introduction of PCV in Russia. In addition, the antimicrobial resistance rate of S. pneumoniae in Russia is substantial, and the emergence of pneumococcal strains with a dual macrolide resistance mechanism is alarming.

Antimicrobial resistance pattern and RAPD profile of Salmonella Ohio isolated from broiler farms in Al-Najaf and Al-Muthana provinces

The present study aimed to investigate the molecular epidemiology and resistance patterns of S. Ohio isolates. All the Ohio isolates were resistant to more than three of the antibiotics, upto 10 antimicrobial agents. Overall, the highest proportions were found for resistance to the following agents: Tetracycline (100%), Nalidixic acid (94.7%), Doxycycline (94.7%), low level resistance to Ciprofloxacin (89.4%),Kanamycin (84.2%), Sulphafurazole (78.9%), and Co-Trimoxazole(52.6%).A total of 11 (DI = 0.958) antimicrobial resistance patterns were observed among 19 isolates of S. Ohio, with a MAR index value ranged between 0.2 to 0.43. The frequency of resistance to Te/Cip/Na/Dox was found in 17 (90%) of the 19 MDR S. Ohio isolates. Genotyping of S. Ohio isolates using 10-mer arbitrary primer, p1254 revealed five RAPD types, denoted by English letters from A to E yielding DI of 0.53, whereas RAPD analysis with primer OPA-4 discriminated only four patterns which assigned F to I (figure), yielding DI of 0.44. When the results of RAPD (with two primers) and antibiotic susceptibility tests are combined, 19 isolates of S. Ohio could be divided into 12 different profiles (DI=0.97). The finding of this study indicated that the broiler chicken can serve as a zoonotic reservoir of MDR bacteria which can be transmitted to human. This is an important implication for human health, because infections with MDR bacteria are difficult to treat and often requires expensive and long term therapy. The RAPD technique can be a useful tool for the analysis of S. Ohio strains. The method might be used as easy, faster, and cost-effective tool for molecular epidemiology research in each laboratory.

A Case Report of Cerebellar Abscess Caused by <i>Bacteroides </i><i>f</i><i>ragilis</i>

50 year old female patient who has headache, dizziness, and nausea-vomiting was admitted to neurosurgery clinic, and an image that was suggestive of an abscess was detected in the cerebellum by means of MRI (Magnetic resonance imaging). This cerebellar abscess was resected together with capsule by right paramedian suboccipital craniotomy, and ceftriaxone and metronidazole treatment was ordered empirically. In the microbiological examination by Gram stain, no micro-organisms were seen. Microorganism was detected on the anaerobic culture and was identified as <i>B</i>. <i>fragilis</i>. Metronidazole was susceptible according to the antibiotic susceptibility test results, so this treatment was continued. The patient was discharged by healing. In diagnosis and treatment of these kinds of patients, it should be considered that <i>B</i>. <i>fragilis</i> can be cause of abscess in the brain.

Prevalence ofTETgenes mediating tetracycline resistance inEscherichia coliclinical isolates in Osun State, Nigeria

The occurrence of tetracycline resistance determinants in 203 Escherichia coli isolates recovered from clinical samples at three different hospitals in Nigeria between June 2009 and May 2010 was investigated. The isolates were subjected to standard procedures. Antibiotic susceptibility to a panel of eight antibiotics was also performed, and resistance genes were detected with the polymerase chain reaction (PCR) technique. One hundred and six E. coli isolates (52.2%) were obtained at LAUTECH Teaching Hospital Osogbo, 85 (41.9%) from OAUTHC Ile Ife and 12 (5.9%) from Osun State Hospital Asubiaro Osogbo. Result of the disk diffusion antibiotic susceptibility test showed 96.1% isolates to be resistant to ampicillin, 77.8% to tetracycline, 37.9% to cotrimoxazole, 38.4% to nalidixic acid, 20.7% to ofloxacin, 17.7% to ceftriaxone, 11.8% to gentamycin, and 2% to nitrofurantoin. One hundred and sixty two (79.9%) isolates had minimum inhibitory concentration (MIC) of tetracycline ≥ 128 μg/ml. The polymerase chain reaction (PCR) detected tetA gene in 89 (43.8%) isolates, tetB gene in 65 (32.0%), and both tetA and tetB genes in 9 (4.4%) isolates. The study demonstrated a relatively high level of gene mediated antibiotic resistance to tetracycline and other antibiotics in E. coli clinical isolates in Southwest region of Nigeria.

Clinical characteristics and antibiotic susceptibility of viridans streptococcal bacteremia in children with febrile neutropenia

This retrospective study was performed in order to investigate the clinical characteristics and antibiotic susceptibility of viridans streptococcal bacteremia (VSB) in febrile neutropenic children in the context of the increase in incidence and antibiotic resistance of VSB. We conducted this study among neutropenic children with underlying hematology/oncology diseases who were diagnosed with VSB at a single institution from April 2009 to June 2012. Clinical and laboratory characteristics of the children as well as antibiotic susceptibility of the causative viridans streptococci were evaluated. Fifty-seven episodes of VSB were diagnosed in 50 children. Severe complications occurred in four children (7.0%), and a death of one child (1.8%) was attributable to VSB. Acute myeloid leukemia was the most common underlying disease (70.2% of all cases), and 71.9% of all cases received chemotherapy including high-dose cytarabine. VSB occurred at a median of 13 days (range 8-21 days) after the beginning of chemotherapy, and fever lasted for a median of 4 days (range 1-21 days). The C-reactive protein level significantly increased within a week after the occurrence of VSB (p < 0.001) and the maximum C-reactive protein level showed a positive correlation with fever duration (r = 0.362, p = 0.007). Second blood cultures were done before the use of glycopeptides in 33 children, and negative results were observed in 30 children (90.9%). Susceptibilities to cefotaxime, cefepime, and vancomycin were 58.9, 69.1, and 100%, respectively. Severe complications of VSB in neutropenic febrile children were rare. We suggest glycopeptide use according to the results of blood culture and antibiotic susceptibility tests based on the susceptibility to cefepime and the microbiologic response to empirical antibiotic treatment not including glycopeptides in this study.

Investigation of the Presence of New Delhi Metallo-Beta-Lactamase-1 (NDM-1) by PCR in Carbapenem-Resistant Gram-Negative Isolates

Bacteria producing New Delhi metallo-beta-lactamase-1 (NDM-1) exhibit high level resistance to beta-lactams including carbapenems. This broad-spectrum resistance limits treatment options for infections caused by NDM-1 producers. NDM-1 was first isolated from an Indian patient in Sweden; since then, NDM-1 producing isolates have been identified in many countries including Turkey. In this study, we investigated the presence of NDM-1 by PCR method in various gram-negative isolates recovered from clinical specimens in tertiary care hospitals in Samsun, Turkey. A total of 210 carbapenem-resistant gram-negative isolates (132 Acinetobacter baumannii, 54 Pseudomonas aeruginosa, 5 Pseudomonas putida, 8 Enterobacter cloacae, 3 Enterobacter aerogenes, 3 Klebsiella pneumoniae, 2 Providencia rettgeri, 2 Escherichia coli and 1 Citrobacter freundii) were included in the study. Identification and antibiotic susceptibility testing of the isolates were performed by using Vitek-2 Compact (bioMerieux, France) and BD Phoenix (BD Diagnostic Systems, MD) automated systems. The results of antibiotic susceptibility testing were interpreted according to the CLSI recommendations. In our study, NDM-1 gene was not detected in any of the clinical isolates by PCR. There was only one case study that reported the presence of NDM-1 in clinical isolates from Turkey [Poirel L et al. Antimicrob Agents Chemother 2012;56:2784]. Our data, together with the others, indicated that the existence of NDM-1 in clinical isolates is not common in Turkey. However, since NDM-1 is a plasmid-encoded enzyme, there is always a risk of spread of this resistance through the bacterial strains in our country. Therefore, continuous surveillance and investigation of carbapenem-resistant isolates with resistance patterns suggestive of NDM-1 may enable to identify NDM-1 producing isolates. Meanwhile special care should be given on rational antibiotic use and establishment of appropriate infection control policies to prevent the spread of NDM-1 producers and other potential resistant strains.

Extended spectrum beta-lactamase (ESBL) production and antibiotic resistances of Escherichia coli and Klebsiella spp. strains isolated from urine cultures

Objective: It was aimed to determine extended spectrum beta-lactamase (ESBL) production and antibiotic resis­tance rates of Escherichia coli and Klebsiella spp. strains isolated from urine cultures of patients admitted to vari­ous outpatient clinics and inpatient clinics of our hospital between December 2011 and August 2012. Methods: E.coli and Klebsiella spp. strains isolated from urine cultures were identified by conventional methods. Antibiotic susceptibilities were determined by using Kirby- Bauer’s disk diffusion method according to Clinical and Laboratory Standards Institute (CLSI) recommendations. Extended spectrum beta-lactamase (ESBL) producing E.coli and Klebsiella spp. strains were detected by using “double disk sinergy method”. Results: During the study period, 308 E.coli and 54 Kleb­siella spp. strains were isolated from urine cultures. ESBL production was detected in 64 (20.8%) of E.coli strains and 21 (38.9%) of Klebsiella spp. strains. ESBL positivity was encountered the most frequently in urine samples of patients who were from outpatient clinics of pediatrics and urology, it was followed by internal clinics and intensive care units. Imipenem resistance was found to be 4.7% and amikacin resistance was 7.8% in ESBL-positive E.coli strains. There was no resistance to carbapenems in ESBL-positive Klebsiella spp. strains, but their amika­cin resistance was 4.8%. Piperacillin tazobactam resis­tance rate in ESBL-positive E.coli and Klebsiella spp. was 17.2% and 14.3%, respectively. Conclusion: Selection of antibiotics should be made by considering results of antibiotic susceptibility tests for treatment of urinary tract infections. Also, determination of ESBL production and reporting it with antibiotic suscep­tibility tests will enhance the success of treatment.

Hierarchical clustering as a rapid tool for surveillance of emerging antibiotic-resistance phenotypes in Klebsiella pneumoniae strains

Antimicrobial resistance is on the rise, and its early detection and surveillance are critical to implement effective control measures. The aim of this study was to develop a rapid hierarchical clustering bioinformatic tool for application on antibiotic susceptibility testing (AST) results (resistant, intermediate, sensitive) of a series of Klebsiella pneumoniae clinical isolates from Algeria and from France for surveillance of antibiotic-resistance phenotypes. A total of 1011 K. pneumoniae strains were collected from August 2008 to December 2012: 221 clinical isolates from western Algeria and 790 clinical isolates from Marseille, France. AST against a panel of 16 antibiotics was done for all isolates. Results of AST were introduced into MultiExperiment Viewer (MeV) software to perform hierarchical clustering, with resistant, intermediate and sensitive being translated to 1, 0 and -1 values, respectively. Hierarchical clustering results were compared to standard resistance phenotypes to evaluate the accuracy of the method. Based on the AST results, the 221 K. pneumoniae strains from Algeria could be separated into six phenotype groups as regards their resistance to β-lactam compounds: extended spectrum β-lactamase (ESBL) (68.3 %), ESBL associated with cephalosporinase (13.1 %), cephalosporinase (0.9 %), penicillinase (3.6 %) and wild-type (14.0 %). Hierarchical clustering by the MeV software applied to the AST results for all 1011 isolates generated clusters that were significantly representative of phenotypic classification and geographical origin, in less than 1 min. Moreover, adding to the dataset the AST results of a K. pneumoniae NDM-1 positive strain, the only strain resistant to imipenem in the series, immediately generated a new branch in the dendrogram. We have developed a rapid and simple hierarchical clustering tool for application on AST results that was able to survey qualitatively and quantitatively the prevalence of known and unknown phenotypes. This tool could be easily implemented in routine clinical microbiology laboratories.

Risk factors influencing mortality related to Stenotrophomonas maltophilia infection in hematology–oncology patients

Stenotrophomonas maltophilia infection is of concern in patients with cancer. Antibiotics active against S. maltophilia are rarely used in the treatment of febrile neutropenia, making it important to identify the factors influencing mortality in cancer patients with S. maltophilia infection. The objective of this study was to analyze the clinical characteristics and outcomes of cancer and hemopathic patients with S. maltophilia infection and assess the factors influencing the mortality. The microbiology laboratory records of Erciyes University, Faculty of Medicine Hospital were reviewed to retrospectively identify patients with S. maltophilia infection between January 2007 and June 2011. A total of 38 patients (25 male, 13 female) were eligible for the study. The median age of the patients was 53 years. The underlying disease was hematological malignancy and disorders in 76.3 % (29 cases), solid tumors in 15.8 % (six cases), aplastic anemia in 7.9 % (three cases), while 18.4 % (seven cases) were hematopoietic stem cell transplantation (HSCT) recipients. An indwelling central venous catheter was used in 32 cases (84.2 %). Twenty-seven patients (71.1 %) were neutropenic at the onset of infection. Nine patients (23.7 %) were receiving corticosteroid therapy. The overall 14-day mortality rate was 50 %. Three of the patients received empirical antibacterial treatment, and three HSCT recipients received trimethoprim-sulfamethoxazole prophylaxis, which is active against S. maltophilia. Severe sepsis (OR 13.24, 95 % confidence interval (CI) 1.62-108.57) and the duration of the treatment (OR 0.73, 95 % CI 0.60-0.90) were related to death based on logistic regression analysis findings. In immunocompromised hematology-oncology patients with severe sepsis, S. maltophilia should be considered as a possible cause of infection, and should be given effective empirical antibiotic treatment immediately; the antimicrobial spectrum may be narrowed according to results of antibiotic susceptibility test.

Nosocomial Infections and Drug Susceptibility Patterns in Methicillin Sensitive and Methicillin Resistant Staphylococcus aureus

Staphylococcus aureus is one of the leading causes of nosocomial infections and is known for its ability to develop resistance to antibiotics. The drug susceptibility pattern of Methicillin Sensitive S. aureus (MSSA) and Methicillin Resistant S. aureus (MRSA) may vary. AIMs and Objectives: This study was carried out to determine and compare the drug susceptibility patterns in nosocomial MSSA and MRSA. The study was conducted between September 2009 and August 2011. Standard conventional methods were used for the isolation and identification of S. aureus. MRSA was identified by the cefoxitin (30 μg) disk method. Antibiotic susceptibility test was done using Kirby-Bauer disk diffusion method and the interpretation of the results was done using CLSI guidelines. Out of 685 strains of S. aureus studied, 173(25.25%) were MRSA and 512 (74.25%) were MSSA. Out of 173 MRSA strains, 114(65.89%) were isolated from pus, 22(12.71%) from vaginal swab, 18(10.40%) from central catheter tip and the remaining from other specimens. All isolates were susceptible to vancomycin and least number of isolates were susceptible to penicillin. MRSA displayed significantly higher resistance to other antibiotics. 45.7% of MRSA strains were resistant to clindamycin, 64.7% to ciprofloxacin, 87.3% to cotrimoxazole, 54.3% to erythromycin, 17.3% to gentamicin, 16.8% to netilmycin, and 58.38% to tetracycline. Inducible clindamycin resistance was detected in 37 (21.38%) strains of MRSA. Nosocomial infections caused by MRSA is a significant problem. MRSA and MSSA differ with their susceptibility to antibiotics. All MRSA isolates in our hospitals were susceptible to vancomycin. Proper selection of the antibiotics based on antibiotic susceptibility test results is needed for effective treatment and prevention of emergence of resistance in MRSA and MSSA.

Profile and multidrug resistance determinants of Chryseobacterium indologenes from seawater and marine fauna

The aim of this study was to investigate the prevalence and genetic basis of multidrug resistance in Chryseobacterium indologenes from seawater and marine invertebrates used for human consumption, in Kaštela Bay, Adriatic Sea, Croatia. Out of 16 samples of seawater, Mediterranean mussel (Mytilus galloprovincialis Lam.), Rayed Mediterranean limpets (Patella caerulea L.) and Purple sea urchins (Paracentrotus lividus Lam.) collected, 15 were positive for C. indologenes. In total, 41 isolates were randomly selected and tested for antibiotic susceptibility by disc-diffusion and broth microdilution methods. PCR was used to detect alleles encoding extended-spectrum (ESBLs) and metallo-β-lactamases (MBLs). The clonality of β-lactamase-producing strains was evaluated by random amplified polymorphic DNA (RAPD) analysis. All C. indologenes isolates showed multiple resistance to at least 9 out of 16 antibiotics tested. Lowest resistance rates were found for piperacillin (9.7 %) and ciprofloxacin (24.4 %), whereas only piperacillin/tazobactam and trimethoprim/sulfamethoxazole showed 100 % activity. More than half of isolates carried bla (IND)-type gene, including 2 isolates carrying bla (IND-2) and 21 carrying bla (IND-7), that was identified as a major MBL genotype in isolates from Adriatic Sea. RAPD typing of IND-producing isolates revealed 6 major groups with no predominant clone in population. The presence of multidrug resistant and IND-producing C. indologenes in marine environment, including marine fauna, pose a risk for transmitting this opportunistic pathogen to humans through recreation or consummation of seafood. In addition, the antibiotic susceptibility test results have practical relevance for empirical treatment of C. indologenes infections.

Drug resistance and molecular epidemiology of Shigella isolated from children with diarrhea

To investigate the prevalence and antibiotic resistance of Shigella isolated from children with diarrhea for the guidance of clinical treatment and prevention and control of bacillary dysentery. A total of 156 strains of Shigella were isolated from feces of children with diarrhea in Zhejiang Xiaoshan Hospital from January 2008 to December 2010. The antimicrobial resistance of the strains was detected by disk diffusion method and the extended-spectrum beta-lactamases (ESBLs) in these isolates were determined using phenotypic confirmatory test; the isolates of ESBLs producing Shigella sonnei were analyzed by REP-PCR. Among 156 strains of Shigella isolated, the most common groups were Shigella sonnei (130 strains, accounting for 83.3%) and Shigella fleaneri (26 strains, accounting for 16.7%), and 81 (51.9%) strains were identified as ESBLs producers, and the positive rates in 2008, 2009 and 2010 were 32.0%, 41.4% and 59.8%, respectively. The results of antibiotic susceptibility test displayed that the resistance rates of ESBLs producing Shigella to ampicillin, cotrimoxazole, cefotaxime, piperacillin were higher than 90%. However, the resistance rates to cefepime, ceftazidime, levofloxacin and ciprofloxacin were low; The resistance of ESBLs producing strains to piperacillin (100% vs. 77.3%), cefotaxime (100% vs. 0), ceftazidime (14.8% vs. 0), cefepime (28.4% vs. 0), cotrimoxazole (95.1% vs. 86.7%) was significantly higher than that of non-ESBLs producing strains (χ(2) = 20.605, 156.000, 12.037, 24.979, 45.040, respectively; P < 0.05). No isolate was resistant to piperacillin/tazobactam and imipenem. There were 7 genotypes among 74 ESBLs producing Shigella sonnei, respectively type A (50), type B (12), type C (8), type D (1), type E (1), type F (1), and type G (1). The isolation rate of ESBLs-producing isolate was high in Shigella from pediatric patients with diarrhea, and the number is going up year by year, and these ESBLs producing Shigella sonnei strains in genotype A are dominant in recent years, Piperacillin/tazobactam is the drug of choice for children with ESBLs producing Shigella infection.

One-day Workflow Scheme for Bacterial Pathogen Detection and Antimicrobial Resistance Testing from Blood Cultures

Bloodstream infections are associated with high mortality rates because of the probable manifestation of sepsis, severe sepsis and septic shock1. Therefore, rapid administration of adequate antibiotic therapy is of foremost importance in the treatment of bloodstream infections. The critical element in this process is timing, heavily dependent on the results of bacterial identification and antibiotic susceptibility testing. Both of these parameters are routinely obtained by culture-based testing, which is time-consuming and takes on average 24-48 hours2, 4. The aim of the study was to develop DNA-based assays for rapid identification of bloodstream infections, as well as rapid antimicrobial susceptibility testing. The first assay is a eubacterial 16S rDNA-based real-time PCR assay complemented with species- or genus-specific probes5. Using these probes, Gram-negative bacteria including Pseudomonas spp., Pseudomonas aeruginosa and Escherichia coli as well as Gram-positive bacteria including Staphylococcus spp., Staphylococcus aureus, Enterococcus spp., Streptococcus spp., and Streptococcus pneumoniae could be distinguished. Using this multiprobe assay, a first identification of the causative micro-organism was given after 2 h. Secondly, we developed a semi-molecular assay for antibiotic susceptibility testing of S. aureus, Enterococcus spp. and (facultative) aerobe Gram-negative rods6. This assay was based on a study in which PCR was used to measure the growth of bacteria7. Bacteria harvested directly from blood cultures are incubated for 6 h with a selection of antibiotics, and following a Sybr Green-based real-time PCR assay determines inhibition of growth. The combination of these two methods could direct the choice of a suitable antibiotic therapy on the same day (Figure 1). In conclusion, molecular analysis of both identification and antibiotic susceptibility offers a faster alternative for pathogen detection and could improve the diagnosis of bloodstream infections.

One-day Workflow Scheme for Bacterial Pathogen Detection and Antimicrobial Resistance Testing from Blood Cultures

Bloodstream infections are associated with high mortality rates because of the probable manifestation of sepsis, severe sepsis and septic shock1. Therefore, rapid administration of adequate antibiotic therapy is of foremost importance in the treatment of bloodstream infections. The critical element in this process is timing, heavily dependent on the results of bacterial identification and antibiotic susceptibility testing. Both of these parameters are routinely obtained by culture-based testing, which is time-consuming and takes on average 24-48 hours2, 4. The aim of the study was to develop DNA-based assays for rapid identification of bloodstream infections, as well as rapid antimicrobial susceptibility testing. The first assay is a eubacterial 16S rDNA-based real-time PCR assay complemented with species- or genus-specific probes5. Using these probes, Gram-negative bacteria including Pseudomonas spp., Pseudomonas aeruginosa and Escherichia coli as well as Gram-positive bacteria including Staphylococcus spp., Staphylococcus aureus, Enterococcus spp., Streptococcus spp., and Streptococcus pneumoniae could be distinguished. Using this multiprobe assay, a first identification of the causative micro-organism was given after 2 h.Secondly, we developed a semi-molecular assay for antibiotic susceptibility testing of S. aureus, Enterococcus spp. and (facultative) aerobe Gram-negative rods6. This assay was based on a study in which PCR was used to measure the growth of bacteria7. Bacteria harvested directly from blood cultures are incubated for 6 h with a selection of antibiotics, and following a Sybr Green-based real-time PCR assay determines inhibition of growth. The combination of these two methods could direct the choice of a suitable antibiotic therapy on the same day (Figure 1). In conclusion, molecular analysis of both identification and antibiotic susceptibility offers a faster alternative for pathogen detection and could improve the diagnosis of bloodstream infections.

Frequent major errors in antimicrobial susceptibility testing of bacterial strains distributed under the Deutsches Krebsforschungszentrum Quality Assurance Program

The Quality Assurance Program (QAP) of the Deutsches Krebsforschungszentrum (DKFZ) was a proficiency testing system developed to service the laboratory animal discipline. The QAP comprised the distribution of bacterial strains from various species of animals for identification to species level and antibiotic susceptibility testing (AST). Identification capabilities were below acceptable standards. This study evaluated AST results using the DKFZ compilations of test results for all bacterial strains showing the number of participants reporting the strain as resistant (R), sensitive (S) or intermediate susceptible (I) to each antibiotic substance used. Due to lack of information about methods used, it was assumed that what the majority of the participants reported (R or S) was the correct test result and that an opposite result was a major error (ME). MEs occurred in 1375 of 14,258 (9.7%) of test results and ME% ranged from 0% to 23.2% per bacterial group-agent group combination. Considerable variation in MEs was found within groups of bacteria and within groups of agents. In addition to poor performance in proper species classification, the quality of AST in laboratory animal diagnostic laboratories seems far below standards considered acceptable in human diagnostic microbiology.