High-level Drug Resistance Research Articles

Spectrum and Drug Susceptibility Profile of Bacteria Recovered from Patients with Wound Infection Referred to Arsho Advanced Medical Laboratory

Wound infection still remains a significant cause of morbidly and mortality. Hence, studying the spectrum of bacterial etiological agents and their drug susceptibility profile is critical. A prospective study was conducted at Arsho Advanced Medical Laboratory from June 2016 to July 2017. Wound specimens were collected from 366 patients following standard procedures. Specimens were plated and incubated at 37°C for 48 hours. Identification and drug susceptibility testing of cultures were carried out by using the VITEK 2 compact system. Among 366 wound samples cultured, bacteria grew in 271(74%) samples. The highest (81.9%) wound infections were documented among patients with an age group of 15-64 years. Two hundred twenty one bacterial isolates were recovered of which 43.2% were Gram-negative while, 56.8% were Gram-positive. Staphylococcus aureus and Coagulase-Negative Staphylococci were major Gram-positive bacteria while Escherichia coli and Pseudomonas spp. were the commonest Gram-negative bacteria. Gram-negative bacteria had the highest overall drug resistance rate against ampicillin. Tobramycin and piperacillin/tazobactam combination were effective antimicrobial agents against Gram-negative bacteria. The highest overall resistance rate to Gram-positive bacteria was observed against erythromycin. Vancomycin and linezolid were the most active antimicrobial agents against Gram-positive bacteria. High culture positivity rate of wound infections reported in the present study initiates many similar studies to be conducted on wound in the country. High level of drug resistance to the commonly prescribed drugs dictates a search for better choices.

Drug Resistance After Failure of WHO Recommended First-Line Antiretroviral Regimen for Adult HIV-1 Infection in South Africa: A Modeling Analysis

BackgroundAntiretroviral therapy (ART) is critical for ending the HIV epidemic. Tenofovir-containing ART is the first-line regimen in many countries including South Africa, with limited access to second-line ART. High levels of drug resistance have been reported among patients after virologic failure on tenofovir-containing first-line regimens (TenoRes Study, Lancet Infect Dis 2016). We assessed drug resistance at the population level using mathematical modeling.MethodsWe developed a stochastic individual-based model of the heterosexual HIV epidemic in KwaZulu-Natal South Africa, and compared drug resistance from scenarios of tenofovir-containing ART scale-up, either CD4-based (threshold < 500 cells/mL) or Fast-track (80% coverage by 2020). The model represents details of HIV transmission and disease progression, demography, sexual behavior, condom use, circumcision, treatment interventions and drug resistance dynamics including key mutations (M184V, K65R and non-nucleoside reverse transcriptase inhibitor (NNRTI)). Using an initial population of 2.5 million, we performed 100 simulations from 1978 to 2030. We examined the prevalence of (majority) transmitted and acquired resistance by 2030.ResultsThe total resistance (proportion of HIV-infected persons with drug resistance) reached 34% from CD4-based ART by 2030, with 30% relative contribution from transmitted resistance and 70% from acquired resistance. In contrast, Fast-track ART reduced the total resistance to 22%; though, there was an increased relative contribution from transmitted resistance (~ 50%). In both scenarios, NNRTI mutations were the most prevalent, followed by M184V and K65R mutations. About 48% of persons with acquired drug- resistance harbored dual drug mutations, 44.7% had triple mutations and 7.3% just single mutations, from CD4-based ART. The respective estimates from Fast-track ART were similar; 49% for dual, 44.1% for triple and 6.9% for single mutations. In both scenarios, NNRTI mutations comprised about 80% of prevalent transmitted resistance.ConclusionCurrent WHO-recommended first-line ART could lead to substantial drug resistance. Effective surveillance for resistance transmission and access to second-line regimens would be crucial.Disclosures All authors: No reported disclosures.

Species distribution and antibiotic susceptibility profile of bacterial uropathogens among patients complaining urinary tract infections

BackgroundUrinary tract infection is the second most common type of infection and the problem is further compounded by the emergence of drug resistance in bacterial uropathogens. The aim of this study was to determine the spectrum of bacterial uropathogens and their drug resistant pattern.MethodsA single institutional cross-sectional study was carried out at Arsho Advanced Medical laboratory from September 2015 to May 2016. A total of 712 urine samples were collected, inoculated onto primary isolation culture media, incubated at 37 °C for 18–24 h, and significant bacteriuria was determined. Identification and the antimicrobial susceptibility testing of bacteria were determined by using the automated VITEK 2 compact system.ResultsOut of 712 urine samples processed, 256 (36%) yielded significant bacteriuria of which 208 (81.25%) were obtained from female and 48 (18.75%) from male patients. Age group of 25–44 were more affected with the infection. Of 256 bacterial isolates recovered, Escherichia coli, was the dominant bacterium. Ampicillin and trimethoprim/sulfamethoxazole were the least effective drugs while piperacillin/tazobactam was the most effective drug against Gram-negative bacteria. Erythromycin was the least effective drug while vancomycin was the most active drug against Gram-positive bacteria.ConclusionsObservation of many bacterial species causing UTI in this study warrants, a continuous epidemiological survey of UTI in health institutions across the country. High level of drug resistance to the commonly prescribed drugs necessitates a search for other options.

Socio-demographic Profile and Drug Sensitivity Pattern of Suspected Drug Resistant Tuberculosis among Patients in Regional Tuberculosis Reference Laboratory (R.T.R.L) of a Tertiary Hospital

Background: Drug resistant tuberculosis has been reported in all regions of the world. In this study we address the socio-demographic profile and drug sensitivity pattern as well as prevalence of drug resistance tuberculosis in a tertiary center (regional TB reference laboratory) in Bangladesh.Method: This Study was carried out in R.T.R.L. (Regional TB Reference Laboratory) in 250 bedded Chittagong General Hospital. Patients who were referred to R.T.R.L during the period July 2012 to July 2013 were included in the study. Total 100 patients with suspected drug resistant tuberculosis (TB) who had any one of 9 criteria of NTP (National Tuberculosis Control Programme) were selected consecutively. Gene xpert MTB/RIF (Rifampicin resistance) test for all sputum positive cases were performed. Sputum sample of Patients with positive microscopy for AFB or positive Xpert/MTB was sent for culture. The samples with positive sputum culture were sent for drug sensitivity test for 1st line anti- tubercular drug.Result: Among 100 patients 78 were male and 22 were female, majority of the patients (64) were between 15-45 years with poor socio economic condition (73%) and primarily educated. Analysis of our Study result showed that 18% of patients were mono-drug resistant. Among them 13% showed resistance to isoniazid (INH), 4% to streptomycin and only 2% to rifampicin. No patient was found resistant to pyrazinamide (PNZ) and 38% of patient with suspected drug – resistant TB was found to have no drug resistance. 18% of patient had multidrug resistant tuberculosis (MDR-TB) among which 56% were relapse cases (48% after cat -I, 8% after cat II), 24% were non – converter of cat –I, 12% belonged to failure of cat –I, 3% failure of cat –II, 2% return after default and others. 1% of patient had history of contact with MDR –TB patient.Conclusion: Drug-resistance tuberculosis especially MDR-TB, was higher in patients with previously incomplete anti-tuberculosis treatment. A high level of drug resistance among the re-treatment TB patients poses a threat of transmission of resistant strains to susceptible persons in the community. For this reason proper counseling of patients and attention towards the completion of the anti-TB treatment are needed.J MEDICINE July 2017; 18 (2) : 62-67

High burden of antimicrobial resistance among gram negative bacteria causing healthcare associated infections in a critical care unit of Nepal

BackgroundHealthcare associated infections (HCAI) and antimicrobial resistance are principal threats to the patients of intensive care units and are the major determining factors for patient outcome. They are associated with increased morbidity, mortality, excess hospitalization and financial costs. The present study is an attempt to investigate the spectrum and antimicrobial resistance of bacterial isolates involved in healthcare associated infections (HCAI) in the patients of a critical care unit at a tertiary care university hospital in Kathmandu, Nepal.MethodsA laboratory based study was conducted over the period of 15 months (January 2014 to March 2015) among the patients of intensive care unit of Tribhuvan University Teaching Hospital, Kathmandu, Nepal. Clinical specimens from patients with suspected healthcare-associated infection were processed and bacterial isolates were identified with standard microbiological methods. Antimicrobial susceptibilities of the isolated strains were determined according to the CLSI guidelines and β-lactamases (ESBL, AmpC, MBL and KPC) were detected by various phenotypic tests.ResultsOne hundred and forty nine clinical specimens received from 135 patients suspected of HCAI (out of 491 patients) were found with significant bacterial growth. Specimens were from patients suspected of hospital-acquired pneumonia (16%, 79/491), bloodstream infections (5.7%, 28/491), surgical site infections (4.7%, 23/491), and urinary tract infections (3.9%, 19/491). Acinetobacter spp., Klebsiella spp., Escherichia coli and Burkholderia cepacia were the leading bacterial pathogens. Extremely high level of drug resistance (95.8%) along with the production of β-lactamases (ESBL; 43.7%, AmpC; 27.5%), MBL; 50.2% and KPC; 4.2%) was observed among Gram negative bacterial isolates.ConclusionHealthcare associated infections are very common in our ICU. Gram negative bacterial pathogens are major culprits associated with these infections and there is alarming state of drug resistance among these isolates. Continuous surveillance and establishment of preventive and control measures of healthcare associated infections are urgently needed in our setting.

Travel and the emergence of high-level drug resistance in Plasmodium falciparum in southwest Uganda: results from a population-based study

BackgroundThe I164L mutation on the dhfr gene confers high level resistance to sulfadoxine–pyrimethamine (SP) but it is rare in Africa except in a cluster of reports where prevalence >10% in highland areas of southwest Uganda and eastern Rwanda. The occurrence of the dhfr I164L mutation was investigated in community surveys in this area and examined the relationship to migration.MethodsA cross-sectional prevalence survey was undertaken in among villages within the catchment areas of two health facilities in a highland site (Kabale) and a highland fringe site (Rukungiri) in 2007. Sociodemographic details, including recent migration, were collected for each person included in the study. A total of 206 Plasmodium falciparum positive subjects were detected by rapid diagnostic test; 203 in Rukungiri and 3 in Kabale. Bloodspot samples were taken and were screened for dhfr I164L.ResultsSequence analysis confirmed the presence of the I164L mutations in twelve P. falciparum positive samples giving an estimated prevalence of 8.6% in Rukungiri. Of the three parasite positive samples in Kabale, none had I164L mutations. Among the twelve I164L positives three were male, ages ranged from 5 to 90 years of age. None of those with the I164L mutation had travelled in the 8 weeks prior to the survey, although three were from households from which at least one household member had travelled during that period. Haplotypes were determined in non-mixed infections and showed the dhfr I164L mutation occurs in both as a N51I + S108N + I164L haplotype (n = 2) and N51I + C59R + S108N + I164L haplotype (n = 5). Genotyping of flanking microsatellite markers showed that the I164L occurred independently on the triple mutant (N51I, C59R + S108N) and double mutant (N51I + S108N) background.ConclusionsThere is sustained local transmission of parasites with the dhfr I164L mutation in Rukungiri and no evidence to indicate its occurrence is associated with recent travel to highly resistant neighbouring areas. The emergence of a regional cluster of I164L in SW Uganda and Rwanda indicates that transmission of I164L is facilitated by strong drug pressure in low transmission areas potentially catalysed in those areas by travel and the importation of parasites from relatively higher transmission settings.

High Burden of Antimicrobial Resistance among Bacteria Causing Pyogenic Wound Infections at a Tertiary Care Hospital in Kathmandu, Nepal.

Pyogenic wound infections are one of the most common clinical entities caused and aggravated by the invasion of pathogenic organisms. Prompt and aggressive antimicrobial therapy is needed to reduce the burden and complications associated with these infections. In this study, we intended to investigate the common pathogens and their antimicrobial susceptibility patterns from the pyogenic wound infections at a tertiary care hospital in Kathmandu, Nepal. A laboratory based cross-sectional study was carried out among the pyogenic clinical specimens of the patients visiting Manmohan Memorial Teaching Hospital, Kathmandu, Nepal. Processing of clinical specimens and isolation and identification of bacterial pathogens were carried out using standard microbiological methods. Antimicrobial susceptibilities and resistant profiles were determined by following the standard guidelines of Clinical and Laboratory Standards Institute (CLSI). About 65% of the clinical specimens were positive for the bacterial growth and Gram positive bacteria (57.4%) were the leading pathogens among pyogenic wound infections. Staphylococcus aureus (412, 49.28%), Escherichia coli (136, 16.27%), Klebsiella spp. (88, 10.53%), and Pseudomonas spp. (44, 5.26%) were the common pathogens isolated. High level of drug resistance was observed among both Gram positive bacteria (51.9%) and Gram negative bacteria (48.7%). Gram positive isolates were resistant to ampicillin, ciprofloxacin, cotrimoxazole, erythromycin, and cloxacillin. Gram negative isolates were resistant to cephalosporins but were well susceptible to amikacin and imipenem. Pyogenic wound infections are common in our hospital and majority of them were associated with multidrug resistant bacteria. The detailed workup of the prevalent pathogens present in infected wounds and their resistance pattern is clearly pertinent to choosing the adequate treatment.

The Bacteriological Quality, Safety, and Antibiogram of Salmonella Isolates from Fresh Meat in Retail Shops of Bahir Dar City, Ethiopia.

The habit of raw meat consumption in addition to the poor hygienic standards and lack of knowledge contribute to food-borne diseases outbreaks. The objective of this research was to assess the bacterial quality and safety of fresh meat from retail Bahir Dar City, Ethiopia. A total of 30 fresh meat samples were collected from butcher shops. Standard bacteriological methods were used to isolate and enumerate bacteria. Kirby-Bauer disk diffusion method was used for antimicrobial susceptibility testing of Salmonella isolates. The mean counts of AMB, TC, and S. aureus were log104.53, 3.97, and 3.88 log10cfu/g, respectively. Salmonella was isolated from 21 (70%) of the samples. Salmonella isolates in this study were highly susceptible to ciprofloxacin, gentamycin, and norfloxacin while they were resistant to erythromycin and tetracycline. High rate of multiple drug resistance was also noticed in Salmonella isolates. The microbial loads of meat were above the recommended microbial safety limits. Besides this, the isolation rate of Salmonella was high and high levels of drug resistance were documented for Salmonella isolates. Measures on handling and appropriate personal hygiene practices of workers in the retail shops are recommended to reduce the change of forborne disease outbreaks.

Additional Drug Resistance Patterns among Multidrug-Resistant Tuberculosis Patients in Korea: Implications for Regimen Design.

Detailed information on additional drug resistance patterns of multidrug-resistant tuberculosis (MDR-TB) is essential to build an effective treatment regimen; however, such data are scarce in Korea. We retrospectively analyzed the results of phenotypic drug susceptibility testing (DST) of culture confirmed-TB patients from January 2010 to December 2014 in 7 university hospitals in Korea. MDR-TB was identified among 6.8% (n = 378) of 5,599 isolates. A total of 57.1% (n = 216) of the MDR-TB patients had never been treated for TB. Strains from MDR-TB patients showed additional resistance to pyrazinamide (PZA) (35.7%), any second-line injectable drug (19.3%), and any fluoroquinolone (26.2%). Extensively drug resistant TB comprised 12.4% (n = 47) of the MDR-TB patients. Of 378 MDR-TB patients, 50.3% (n = 190) were eligible for the shorter MDR-TB regimen, and 50.0% (n = 189) were fully susceptible to the 5 drugs comprising the standard conventional regimen (PZA, kanamycin, ofloxoacin, prothionamide, and cycloserine). In conclusion, the proportion of new patients and the levels of additional drug resistance were high in MDR-TB patients. Considering the high levels of drug resistance, the shorter MDR-TB treatment regimen may not be feasible; instead, an individually tailored regimen based on the results of molecular and phenotypic DST may be more appropriate in MDR-TB patients in Korea.

Prevalence and Antimicrobial Resistance of Salmonella enterica Serovar Indiana in China (1984-2016).

Salmonella enterica serovar Indiana, first described in 1955, is generally regarded as having a low frequency worldwide with outbreaks of gastroenteritis and abortions described in North America and Europe. In China, S. Indiana was first reported in 1984 and in the subsequent 71 surveys in 35 cities/municipalities from 18 provinces, 70% of which were after 2012, S. Indiana has been shown to have become widely prevalent in people, animals, food and the environment around abattoirs and meat processing facilities. The organism is now one of the most common serovars found in livestock and raw meat in China with S. Indiana isolates having high levels of drug resistance, especially against tetracyclines, quinolones, folate pathway inhibitors, phenicols, penicillins, monobactams and nitrofurans. Further, S. Indiana isolates that are concurrently resistant to ciprofloxacin and ceftriaxone/cefotaxime have emerged. Studies have suggested the high levels of multidrug resistance of S. Indiana might be associated with the presence of class 1 integrons and plasmids. Unfortunately, information on the high prevalence of S. Indiana and its extensive drug resistance in China has largely escaped international recognition as it largely appears in local reports written in Chinese. To address this situation, we reviewed all the available local Chinese and international publications on the organism in China and report our findings in this review.

Bacterial blood stream infections and antibiogram among febrile patients at Bahir Dar Regional Health Research Laboratory Center, Ethiopia

Bacterial blood stream infections (BSIs) are a common cause of morbidity and mortality. Prevailing data on bacterial species causing BSI and their antibiogram are essential for proper management of patients. A retrospective study was conducted on blood culture results that had been processed from March 2013 to January 2015 at Bahir Dar Regional Health Research Laboratory Center. In January 2015, data on age, sex of patients and bacterial isolates with antibiogram were extracted from registration log book. Blood stream causing bacteria were identified according to standard operational procedure for blood culture. Antimicrobial susceptibility tests were performed according to Kirby-Bauer disc diffusion methods. A total of 561 blood specimens were requested for blood culture. Of these, 220 (39.2%, 95% CI: 35.3-43.4%) blood cultures had aerobic bacterial growth. Gram negative bacterial isolates constituted 115 (52.3%) of the isolated bacteria. Staphylococcus aureus 50 (22.7%), coagulase negative staphylococci 35(15.9%), Klebsiella pneumoniae 35 (15.9%), Escherichia coli 19 (8.6%), Pseudomonas aeruginosa 15 (6.8%) and Acinetobacter species 13(5.9%) were the most dominant isolates. Overall, drug resistance for gram positive bacteria were 7 to 61% and for gram negatives 6.9 to 82.6%. Among the gram positive bacteria, high resistance levels were observed against penicillin (61%) and oxacillin (52.9%). The gram negative bacterial isolates showed 66 to 82.6% resistance to ampicillin, ceftriaxone and trimethoprim-sulfamethoxazole. The present study revealed that bacterial blood stream infections linked with high levels of drug resistance would pose a challenge in treatment of patients with BSIs. Hence, blood culture with antibiotic susceptibility tests could play key role for appropriate treatment of patients with bacterial blood stream infection. Key words : Blood culture, Bloodstream infection, antibiogram, Ethiopia

First Line Anti-Tubercular Drug Resistance Pattern of Mycobacterium Tuberculosis Isolated From Specialized Hospitals of Dhaka City

The present study was undertaken to determine the drug resistance pattern of M. tuberculosis isolated from 225 pulmonary and 45 extrapulmonary tuberculosis cases. The samples were cultured on Lowenstein Jensen (L-J) media for isolation of M. tuberculosis. Drug resistance to first line anti tubercular drugsnamely isoniazid (INH), rifampicin (RIF), Ethambutol (ETH) and streptomycin (SM) were determined by indirect proportion method. The overall drug resistance of M. tuberculosis was 53.6% to any of the first line anti tubercular drugs. Rate of multi drug resistant tuberculosis (MDR-TB) among the untreated cases was 4.2%, while it was 36.0% in previously treated cases. It was found that 83.3% rifampicin resistant M. tuberculosis was cross resistant to one or more of other first line anti-tubercular drugs, while cross resistance of INH, ETH and SM resistant isolates was much low. The present study revealed that high level of drug resistance exists to individual anti tubercular drugs and MDR-TB is an emerging problem, particularly in treated cases. Rifampicin resistance could be used as a surrogate marker for drug resistance to other first line anti tubercular drugs.Ibrahim Med. Coll. J. 2014; 8(2): 41-46

Isolation and identification of Ralstonia mannitolilytica strains from a patient with septicaemia and analysis of their drug resistance genes

Objective To isolate and identify the pathogenic bacteria from peripheral blood of a patient with septicemia of unknown etiology and to analyze their drug resistance genes. Methods Two peripheral blood samples were collected from the patient after having fever. Several assays including culturing bacteria on blood agar plates by using streaking technique, Gram-staining of bacterial colonies and microscopic observation, VITEK 2-compact automatic bacterium detection and analysis system as well as a sequencing analysis of the 16s rRNA gene were performed to identify the bacterial pathogens in blood samples. Microdilution test was performed to detect the drug susceptibilities of isolated bacteria to antibiotics. Confirmatory tests were performed to detect the production of β-lactamase and extended spectrum β-lactamase by the isolated strains and the phenotypes of AmpC enzyme and carbapenemase. PCR was used to identify the β-lactamase-encoding genes in the isolated strains by using the primers of 19 common β-lactamase-, AmpC enzyme- and carbapenemase-encoding genes in Enterobacteriaceae strains and the primers of 21 annotated gene sequences encoding the β-lactamase of a Ralstonia mannitolilytica strain. The PCR products were sequenced and analyzed after T-A cloning. Results Ralstonia mannitolilytica strains were isolated from the two peripheral blood samples. The isolated strains were sensitive to ceftriaxone, cefepime, ciprofloxacin, ofloxacin, tigecycline and compound sulfamethoxazole (SMZ-TMP), but resistant to the other 11 tested antibiotics. Results of PCR amplification by using the primers of common genes encoding β-lactamase of Enterobacteriaceae strains were all negative. Fragments of genes encoding the β-lactamase of the isolated Ralstonia mannitolilytica strain were successfully amplified, which were TK49_09850, TK49_12955, TK49_14470, TK49_14495 and TK49_18990. The sequences of the amplified gene fragments were not similar to those of the common β-lactamase-encoding genes in Enterobacteriaceae strains. Conclusion The patient was infected with Ralstonia mannitolilytica. The isolated Ralstonia mannitolilytica strain showed a high-level drug resistance with a noticeable diversity against different β-lactam antibiotics. The genes encoding β-lactamase of the isolated Ralstonia mannitolilytica strain were completely different to those of Enterobacteriaceae strains. Key words: Ralstonia mannitolilytica; Septicaemia; Isolation and identification; Drug resistance; β-lactamase-encoding gene

Drug resistance mechanisms and their regulation in non-albicans Candida species.

Fungal pathogens use various mechanisms to survive exposure to drugs. Prolonged treatment very often leads to the stepwise acquisition of resistance. The limited number of antifungal therapeutics and their mostly fungistatic rather than fungicidal character facilitates selection of resistant strains. These are able to cope with cytotoxic molecules by acquisition of appropriate mutations, re-wiring gene expression and metabolic adjustments. Recent evidence points to the paramount importance of the permeability barrier and cell wall integrity in the process of adaptation to high drug concentrations. Molecular details of basal and acquired drug resistance are best characterized in the most frequent human fungal pathogen, Candida albicans Effector genes directly related to the acquisition of elevated tolerance of this species to azole and echinocandin drugs are well described. The emergence of high-level drug resistance against intrinsically lower susceptibility to azoles in yeast species other than C. albicans is, however, of particular concern. This is due to their steadily increasing contribution to high mortality rates associated with disseminated infections. Recent findings concerning underlying mechanisms associated with elevated drug resistance suggest a link to cell wall and plasma membrane metabolism in non-albicans Candida species.

Emerging Perils of Extended Spectrum β-Lactamase Producing Enterobacteriaceae Clinical Isolates in a Teaching Hospital of Nepal.

Introduction. Infections due to extended spectrum β-lactamase producing Enterobacteriaceae are on the rise. They pose serious public health problems due to their resistance to large number of antibiotics. However, little is known about the genotypes of ESBL from Nepal. Therefore, the study presents results of phenotypic and molecular characterization of ESBL producing Escherichia coli and Klebsiella spp. isolated from various clinical specimens in a tertiary care teaching hospital of Nepal. Methods. A total of 172 Enterobacteriaceae clinical isolates recovered from various clinical specimens were analyzed for their antibiotic susceptibility test. Detection of ESBLs was carried out using combination disk test and multiplex PCR for their genotypes (CTX-M, SHV, and TEM). Results. Out of 172 clinical isolates, 70 (40.6%) of them were found ESBL producers. The major source of ESBL producers was urinary tract samples and the highest ESBL production was observed in Escherichia coli (46.5%). Among ESBL genotypes, CTX-M (91.4%) was most predominant, followed by TEM (65.7%) and SHV (11.4%) in both of the isolates. Conclusions. High level of drug resistance and ESBL production was observed among the clinical isolates. There is a need for longitudinal and nationwide surveillance for drug resistance in clinical isolates and antimicrobial stewardship is necessary to guide the appropriate and judicious antibiotic use.

The detection and antimicrobial susceptibility profile of Shigella isolates from meat and swab samples at butchers' shops in Gondar town, Northwest Ethiopia.

Food borne pathogens are major causes of deaths, illnesses and billions of dollars of expenses. The burden of food borne illness is worsened by the ever increasing rate of antimicrobial resistance microbes. Shigella, a bacterial pathogen associated with food, is reported to account for higher prevalence rates of food borne illness in different settings. A cross-sectional study was conducted from February 10 to June 30, 2013, at the butcher houses of Gondar town in the Northwest of Ethiopia to assess the prevalence and antimicrobial susceptibility pattern of Shigella. Cattle raw meat and swab samples from selected critical control points, including knives, chopping boards, and the hands and noses of butchers, were collected and analyzed. The identification of Shigella was carried out using colony characteristics, the Gram reaction, and biochemical tests. Antimicrobial susceptibility testing was performed using the Kirby-Bauer disc diffusion method. The overall hygienic status of the butcher shops was also assessed using a checklist. An observational analysis revealed that the sanitary condition of the butcher shops and their premises was poor. Of 306 samples screened, 10.5% were positive for Shigella. Approximately 7.4% of meat samples and 10.2% of swab samples were contaminated with Shigella. Out of the total Shigella isolates, 90.6%, 46.9%, 18.8% and 9.4% were resistant to ampicillin, amoxicillin, ceftriaxone and tetracycline, respectively. A multidrug resistance pattern was recorded in 27.8% of the isolates. In conclusion, the safety of meat sold at Gondar butchers houses was poor. The identified Shigella isolates showed high levels of drug resistance and multidrug resistance patterns for commonly used antimicrobials in veterinary and human medicine. Practicing wise use of antimicrobials and strict sanitary interventions at different critical control points is strongly recommended, in addition to further in-depth studies to prevent unprecedented consequences from shigellosis.

The Distribution of Fitness Costs of Resistance-Conferring Mutations Is a Key Determinant for the Future Burden of Drug-Resistant Tuberculosis: A Model-Based Analysis.

Drug resistance poses a serious challenge for the control of tuberculosis in many settings. It is well established that the expected future trend in resistance depends on the reproductive fitness of drug-resistant Mycobacterium tuberculosis. However, the variability in fitness between strains with different resistance-conferring mutations has been largely ignored when making these predictions. We developed a novel approach for incorporating the variable fitness costs of drug resistance-conferring mutations and for tracking this distribution of fitness costs over time within a transmission model. We used this approach to describe the effects of realistic fitness cost distributions on the future prevalence of drug-resistant tuberculosis. The shape of the distribution of fitness costs was a strong predictor of the long-term prevalence of resistance. While, as expected, lower average fitness costs of drug resistance-conferring mutations were associated with more severe epidemics of drug-resistant tuberculosis, fitness distributions with greater variance also led to higher levels of drug resistance. For example, compared to simulations in which the fitness cost of resistance was fixed, introducing a realistic amount of variance resulted in a 40% increase in prevalence of drug-resistant tuberculosis after 20 years. The differences in the fitness costs associated with drug resistance-conferring mutations are a key determinant of the future burden of drug-resistant tuberculosis. Future studies that can better establish the range of fitness costs associated with drug resistance-conferring mutations will improve projections and thus facilitate better public health planning efforts.

Conformational variation of an extreme drug resistant mutant of HIV protease

Molecular mechanisms leading to high level drug resistance have been analyzed for the clinical variant of HIV-1 protease bearing 20 mutations (PR20); which has several orders of magnitude worse affinity for tested drugs. Two crystal structures of ligand-free PR20 with the D25N mutation of the catalytic aspartate (PR20D25N) revealed three dimers with different flap conformations. The diverse conformations of PR20D25N included a dimer with one flap in a unique “tucked” conformation; directed into the active site. Analysis of molecular dynamics (MD) simulations of the ligand-free PR20 and wild-type enzymes showed that the mutations in PR20 alter the correlated interactions between two monomers in the dimer. The two flaps tend to fluctuate more independently in PR20 than in the wild type enzyme. Combining the results of structural analysis by X-ray crystallography and MD simulations; unusual flap conformations and weakly correlated inter-subunit motions may contribute to the high level resistance of PR20.

The Combination of the R263K and T66I Resistance Substitutions in HIV-1 Integrase Is Incompatible with High-Level Viral Replication and the Development of High-Level Drug Resistance.

The R263K substitution in integrase has been selected in tissue culture with dolutegravir (DTG) and has been reported for several treatment-experienced individuals receiving DTG as part of salvage therapy. The R263K substitution seems to be incompatible with the presence of common resistance mutations associated with raltegravir (RAL), a different integrase strand transfer inhibitor (INSTI). T66I is a substitution that is common in individuals who have developed resistance against a different INSTI termed elvitegravir (EVG), but it is not known whether these two mutations might be compatible in the context of resistance against DTG or what impact the combination of these substitutions might have on resistance against INSTIs. E138K is a common secondary substitution observed with various primary resistance substitutions in RAL- and EVG-treated individuals. Viral infectivity, replicative capacity, and resistance against INSTIs were measured in cell-based assays. Strand transfer and 3' processing activities were measured biochemically. The combination of the R263K and T66I substitutions decreased HIV-1 infectivity, replicative capacity, and strand transfer activity. The addition of the E138K substitution partially compensated for these deficits and resulted in high levels of resistance against EVG but not against DTG or RAL. These findings suggest that the presence of the T66I substitution will not compromise the activity of DTG and may also help to prevent the additional generation of the R263K mutation. Our observations support the use of DTG in second-line therapy for individuals who experience treatment failure with EVG due to the T66I substitution. The integrase strand transfer inhibitors (INSTIs) elvitegravir and dolutegravir are newly developed inhibitors against human immunodeficiency virus type 1 (HIV-1). HIV drug-resistant mutations in integrase that can arise in individuals treated with elvitegravir commonly include the T66I substitution, whereas R263K is a signature resistance substitution against dolutegravir. In order to determine how different combinations of integrase resistance mutations can influence the outcome of therapy, we report here the effects of the T66I, E138K, and R263K substitutions, alone and in combination, on viral replicative capacity and resistance to integrase inhibitors. Our results show that the addition of R263K to the T66I substitution diminishes viral replicative capacity and strand transfer activity while not compromising susceptibility to dolutegravir. This supports the use of dolutegravir in second-line therapy for patients failing elvitegravir therapy who harbor the T66I resistance substitution.

Pseudomembranous Candidiasis Indicates High Level Drug Resistance among Patients on Antiretroviral Treatment in Nairobi East District, Kenya

Objectives: The aim of this study was to determine antiretroviral drug resistance patterns in Results: Out of (n=45) patients with OPC, (n=28; 62%) had high HIV-RNA levels. The (n=28) patients who mostly presented with pseudomembraneuos candidiasis (n=26; p<.0001), had significantly more previous episodes of OPC (55% versus 18%; P<0.0373) lower median CD4 cell counts (74 versus 521; P<.0001) and higher HIV-RNA median plasma levels (111,191 copies/ml versus <20; P<.0001). The sensitivity (0.96) and specificity (0.87) of pseudomebraneous candidiasis to predict virological failure was high.