Similar Resistance Patterns Research Articles

Suppression of ciprofloxacin-induced resistant Pseudomonas aeruginosa in a dynamic kill curve system

Current dosing approaches for treating microbial infections ignore resistant subpopulations. A clinical isolate of Pseudomonas aeruginosa was cultured in a dynamic in vitro kill curve system designed to simulate the half-lives of drugs in order to evaluate the drug–microbial response relationship. The first dose of ciprofloxacin (CIP) uses a concentration equivalent to the unbound fraction of a 200 mg clinical dose. A second dose of 200 mg or 600 mg CIP, or ceftriaxone (CFX) or gentamicin (GEN) was administered at 12 h. Dynamics of the minimum inhibitory concentration (MIC) were assessed using Etest strips before and throughout the CIP treatment period. In addition, the microbroth dilution method was used to evaluate drug susceptibility across a wide range of antibiotics using samples from before and after CIP exposure. A significant loss of CIP effects was observed at the second dose. Cross-resistance to many antibiotics (cefoxitin, cefuroxime, cefotetan, ampicillin and ertapenem) was observed. GEN, but not CFX or high-dose CIP, was sufficient to suppress the developed resistant subpopulation following the initial CIP exposure. The CIP MIC increased substantially from 0.13 μg/mL pre dose to 4 μg/mL at 12 h after a CIP dose. In addition, aztreonam induced a similar resistance pattern as CIP, indicating that induction of resistance was not limited to fluoroquinolones. In conclusion, the in vitro dynamic kill curve system revealed that aminoglycosides, more than other classes of antibiotics, were effective against the CIP-induced resistant subpopulations.

Variation in erythromycin and clindamycin resistance patterns between New Zealand and Australian group B streptococcus isolates

Intrapartum chemoprophylaxis for group B streptococcus (GBS) carriers reduces the risk of early-onset neonatal GBS infection. For women with β-lactam allergy, either erythromycin or clindamycin are administered. Recent reports worldwide suggest that GBS resistance to these antibiotics is increasing. To compare erythromycin and clindamycin resistance phenotypes in invasive neonatal GBS isolates across New Zealand and Australia over the past two decades and to determine whether regional variation in resistance patterns exist. Invasive neonatal GBS isolates were collected from laboratories across New Zealand (n=107) and Australia (n=74) over two time periods (1992-1994 and 2002-2004 in New Zealand; 1982-2001 and 2002-2006 in Australia) and subjected to standard antibiotic susceptibility testing. A nested sub-study in New Zealand examined antibiotic susceptibilities of 112 maternal colonising GBS isolates during 2003-2004. Erythromycin resistance among invasive neonatal GBS isolates increased across both countries over the past decade, with similar rates of resistance in New Zealand (9%) and Australia (6%) in recent years. New Zealand erythromycin-resistant GBS isolates commonly displayed cross-resistance to clindamycin. Also, there were significantly higher rates of isolated clindamycin resistance in GBS isolates from New Zealand than Australia (P=0.034). Maternal GBS isolates from New Zealand showed similar resistance patterns to neonatal isolates. Erythromycin and clindamycin resistance among invasive neonatal GBS isolates has emerged in both New Zealand and Australia over the past decade and is consistent with global trends in GBS resistance patterns. Although regional variations exist, these findings should be considered when implementing intrapartum GBS prevention strategies.

Pilot Study of Antimicrobial-Resistant Escherichia coli in Herring Gulls (Larus argentatus) and Wastewater in the Northeastern United States

Wildlife may be an important reservoir of antibiotic-resistant bacteria and resistance genes. In this pilot study, the prevalence and patterns of antimicrobial resistance in Escherichia coli cultured from wild herring gull (Larus argentatus) feces and human wastewater at Cape Cod, Massachusetts, USA, was compared. Antimicrobial susceptibility was tested using Kirby-Bauer disk diffusion with seven antimicrobial agents. A high proportion of antimicrobial agent-resistant E. coli isolates (59.2%) were detected in wastewater samples compared with a lower prevalence of 17.5% in gull feces. In addition, there was a large proportion of isolates with intermediate susceptibility (93.0%) in gull feces. Although similar resistance patterns and shared resistance genes suggest possible wastewater contamination of the local environment, the relatively low frequency of resistance and high prevalence of intermediate susceptibility detected in E. coli cultured from gull feces depict a complex model of antimicrobial resistance among E. coli strains of wildlife origin.

Antimicrobial Resistance of Enterococci Isolated from Mastitic Bovine Milk Samples in Korea

The aim of this study was to determine the antimicrobial resistance of various species of enterococci isolated from mastitic bovine milk samples. A total of 105 enterococci isolates were examined: Enterococcus faecalis (n = 47), Enterococcus faecium (n = 39), Enterococcus gallinarum (n = 6), Enterococcus avium (n = 6), Enterococcus hirae (n = 5) and Enterococcus durans (n = 2). All the isolates were susceptible to ampicillin, gentamicin and vancomycin, and only a single E. hirae isolate was resistant to ampicillin. In general, the most frequently observed resistance among the enterococcal isolates was to tetracycline (69.5%), followed by penicillin (64.7%), erythromycin (57.1%) and cephalothin (44.7%). A similar antimicrobial resistance pattern was observed among individual species except E. durans, which exhibited only tetracycline resistance. Resistance observed among isolates of E. hirae and E. gallinarum was almost as high as E. faecium and E. faecalis. Of 105 isolates, only six (5.7%) strains of E. faecium were susceptible to all the antimicrobials tested and about 52% (55/105) showed resistance to more than three antimicrobials. The most common multiple resistance pattern was penicillin, tetracycline and erythromycin, which was observed in 32 of 105 (30.4%) isolates. This study demonstrates that enterococcal isolates belonging to minor species showed antimicrobial resistance rates as high as those of E. faecium and E. faecalis, and that monitoring of antimicrobial resistance should not be restricted only to those two major species.

Prevalence of Antimicrobial Resistance Among Salmonella Isolates from Chicken in China

We evaluated the antimicrobial resistance of Salmonella isolated in 2008 from a chicken hatchery, chicken farms, and chicken slaughterhouses in China. A total of 311 Salmonella isolates were collected from the three sources, and two serogroups of Salmonella were detected, of which 133 (42.8%) consisted of Salmonella indiana and 178 (57.2%) of Salmonella enteritidis. The lowest percentage of S. indiana isolates was found in the chicken hatchery (4.2%), followed by the chicken farms (54.9%) and the slaughterhouses (71.4%). More than 80% of the S. indiana isolates were highly resistant to ampicillin (97.7%), amoxicillin/clavulanic acid (87.9%), cephalothin (87.9%), ceftiofur (85.7%), chloramphenicol (84.9%), florfenicol (90.9%), tetracycline (97.7%), doxycycline (98.5%), kanamycin (90.2%), and gentamicin (92.5%). About 60% of the S. indiana isolates were resistant to enrofloxacin (65.4%), norfloxacin (78.9%), and ciprofloxacin (59.4%). Of the S. indiana isolates, 4.5% were susceptible to amikacin and 5.3% to colistin. Of the S. enteritidis isolates, 73% were resistant to ampicillin, 33.1% to amoxicillin/clavulanic acid, 66.3% to tetracycline, and 65.3% to doxycycline, whereas all of these isolates were susceptible to the other drugs used in the study. The S. indiana isolates showed resistance to 16 antimicrobial agents. Strains of Salmonella (n = 108) carrying the resistance genes floR, aac(6')-Ib-cr, and bla(TEM) were most prevalent among the 133 isolates of S. indiana, at a frequency of 81.2%. The use of pulsed-field gel electrophoresis to analyze the S. indiana isolates that showed similar antimicrobial resistance patterns and carried resistance genes revealed six genotypes of these organisms. Most of these isolates had the common pulsed-field gel electrophoresis patterns found in the chicken hatchery, chicken farms, and slaughterhouses, suggesting that many multidrug-resistant isolates of S. indiana prevailed in the three sources. Some of these isolates were not derived from a specific clone, but represented a variety of genotypes of S. indiana.

872 Antimicrobial Resistance of Streptococcus Pneumoniae Isolated From Children with Nasopharyngeal Carriage and Infections During the 9-Year Period (1999-2007)

Aim: Streptococcus pneumoniae continues to be an important cause of community-acquired respiratory tract infections. Because of increase in its antimicrobial resistance, the surveillance of the local antimicrobial susceptibility of S.pneumoniae should be carried out regularly.Methods: Streptococcus pneumoniae strains were isolated from children on admission to The Children's Memorial Health Institute, Warsaw, Poland between Jan 1999 and Dec 2007. A total of 784 isolates of S.pneumoniae were collected. Susceptibility to antibiotics was analyzed in two periods: 1999-2002 and 2003-2007. All the strains (185) collected in the first period originated from children with pneumococcal diseases. Of the 599 strains obtained in the second period, 234 were isolated from children with S.pneumoniae infection and 365 from children with nasopharyngeal carriage.Results and Conclusions: Rate of resistance to penicillin was stable during the whole period of the study (3% vs. 4%). Higher resistance rates to erythromycin (19% vs. 29%), clindamycin (14% vs. 26%) and lower resistance rates to tetracycline (37% vs. 9%) and co-trimoxazole (47% vs. 41%) were observed among isolates obtained in the second period. S.pneumoniae strains isolated from infections and from carriage exhibited similar resistance patterns.

Antimicrobial Susceptibility of Coagulase-Negative Staphylococci Isolated from Bovine Mastitis Between 2003 and 2008 in Korea

A total of 1,444 coagulase-negative staphylococci (CNS) isolates from bovine mastitic milk samples collected during 2003-2008 in Korea were identified to the species level. Of 14 species identified, S. simulans, S. haemolyticus, and S. sciuri accounted for over 60% of the isolates. All the CNS isolates were tested for susceptibility to eight antimicrobials commonly used in dairy cattle. With a few exceptions, similar resistance patterns were observed among the CNS species: penicillin and ampicillin showed the lowest activity while amikacin, cephalothin, and gentamycin were highly effective. About 39% (557/1,444) of the CNS isolates were pan-susceptible, while 12% (175/1,444) showed resistance to four or more antimicrobials tested.

An outbreak of shigellosis due to Shigella flexneri serotype 3a in a prison in Iran.

On June 16 and 17, 2007, the medical clinic of a prison in Isfahan, Iran received multiple reports of gastrointestinal illness among prisoners. A cross-sectional study was therefore undertaken to determine the extent, causative agent and possible source of the outbreak. A case-patient was defined and patient information was collected with a standardized questionnaire. Stool samples were collected from the patients and restaurant employees, and analyzed for the presence of enteric bacteria by routine bacteriological methods. Shigella isolates were identified and serotyped by commercially available antisera. The relationship between the strains was determined using antimicrobial drug resistance pattern analysis and enterobacterial repetitive intergenic consensus polymerase chain reaction (ERIC-PCR). Seven hundred one inmates experienced gastrointestinal illness and severe diarrhea. The attack rate was 14.02%. Rectal swabs and stool cultures recovered from patients tested positive for Shigella flexneri serotype 3a. All tested isolates had a similar antibiotic resistance and ERIC-PCR pattern. Our findings demonstrated that raw vegetables were more likely to be the causative agent of this outbreak. The results indicated that a single clone of S. flexneri was responsible for this outbreak. Although we could not trace the exact origin of the organism, the consumption of raw vegetables one day prior to the onset of illness was strongly associated with an increased risk of S. flexneri infection. This study emphasizes the need for accurate monitoring and surveillance of food and vegetables consumed in prisons.

Comparison of phenotypic and genotypic antimicrobial profiles in Escherichia coli and Salmonella enterica from the same dairy cattle farms

Transmission of antimicrobial drug resistance from resistant bacteria to non-resistant strains is an important public health issue. In this study, we have examined the possibility of multiple resistance gene transfer between Escherichia coli and Salmonella in the natural setting. Bacteria isolated from calves concurrently shedding E. coli and Salmonella showed similar antimicrobial drug resistance patterns as measured by a broth dilution method. However, microarray analysis of the antibiotic resistance at the gene level revealed several differences in resistance gene profile. Resistance profiles of E. coli isolated from different farms were closer than the profile of E. coli and Salmonella isolated from the same farm. This shows that the chance of multiple resistance gene transfers between these species is unlikely.

RAHN-2, a chromosomal extended-spectrum class A -lactamase from Rahnella aquatilis

Rahnella aquatilis is an environmental enterobacterial species with a chromosomal bla(RAHN-1) gene encoding extended-spectrum class A beta-lactamase RAHN-1. We describe the diversity of bla(RAHN) genes from two groups of strains, G1 and G2, isolated from raw fruits and vegetables, and the new class A beta-lactamase RAHN-2. MICs were determined by Etest. bla(RAHN) genes were amplified by PCR, sequenced, and cloned to produce RAHN-1 and RAHN-2 proteins whose kinetic parameters were determined. All strains had similar beta-lactam resistance patterns. However, isolates of G1 were at least 2-fold more susceptible to piperacillin, amoxicillin, piperacillin/clavulanic acid, piperacillin/tazobactam and cefotaxime. Sequences of bla(RAHN) from G1 had <82.9% identity with that of bla(RAHN-1), whereas those of G2 were >92% identical. The RAHN-2 beta-lactamase was 89.8% identical to RAHN-1, 5-fold more efficient than RAHN-1 in hydrolysing ticarcillin and 2.5-fold more efficient in cefotaxime and cefuroxime hydrolysis. However, the specific activity of RAHN-1 was 2-fold higher than that of RAHN-2 suggesting that the bla(RAHN) genes are regulated differently. The new class A beta-lactamase RAHN-2 is phenotypically difficult to detect and requires MIC determination.

Genetic Similarity ofCampylobacterIsolates in Humans, Food, and Water Sources in Central Poland

Campylobacter spp. is an important cause of gastroenteritis in humans throughout the world. However, sources of these infections are often difficult to identify. Therefore, this study aimed at analyzing the genetic relatedness of Campylobacter isolates from environmental and food samples as well as stool specimens of diarrheal patients obtained in a single geographic region in Poland. Only a few Campylobacter jejuni isolates (4/18, 22%) could be assigned to one cluster, whereas the majority were unrelated. In contrast, the majority of Campylobacter coli strains (25/35, 71%) belonged to three pulsed-field gel electrophoresis (PFGE) clusters containing isolates of various origins (i.e., water samples, chicken carcasses, and humans). Isolates belonging to the clusters showed also similar antibiotic resistance patterns and similar genotypes with respect to the occurrence of the virB11 and iam genes. This suggests that Campylobacter strains may circulate between humans, poultry, and recreational water sources in the rural region in central Poland.

A Survey of Plasmid-Mediated Fluoroquinolone Resistance Genes from Escherichia coli Isolates and Their Dissemination in Shandong, China

Bacterial resistance to fluoroquinolones result from mutations in the quinolone resistance-determining regions of the drug targets, overexpression of efflux pumps, and/or the more recently identified plasmid-mediated low-level resistance mechanisms. We investigated the prevalence of and characterized plasmid-mediated fluoroquinolone resistance genes (qnrA, qnrB, qnrS, aac(6')-Ib-cr, and qepA) by polymerase chain reaction in fluoroquinolone-resistant Escherichia coli (n = 530) isolated from a chicken farm, a pig farm, and hospitalized patients in Shandong, China, in 2007. The aac(6')-Ib-cr gene was the most prevalent resistance gene that was detected in bacteria isolated from all sources. Next was the qnrS gene, which was predominantly present in isolates from the pig farm. Only eight (5.8%) isolates from hospital patients were found to possess the qepA gene, and these isolates were first reported in qepA-carrying E. coli from humans in China. The qnrA and qnrB genes were not detected in any of the isolates. Further, most of the isolates were also resistant to beta-lactams and aminoglycosides as determined by the broth microdilution method. Pulsed-field gel electrophoresis analysis of the E. coli isolates with similar resistance patterns that also carried resistance genes showed great genomic diversity among these bacteria, suggesting that the multiresistant E. coli isolates carrying the qnr, aac(6')-Ib-cr, or qepA genes were not derived from a specific clone, but represented a wide variety of different genotypes. The results of Southern hybridization revealed that qepA, qnrS, and parts of aac(6')-Ib-cr genes were localized on plasmids and/or chromosome. qepA and aac(6')-Ib-cr genes were colocalized with aac(6')-Ib-cr and qnrS genes, respectively, on the same plasmids. Our study demonstrated that two different genes (qepA and aac(6')-Ib-cr) were identified on the same plasmid in E. coli strains derived from patients and qnrS and aac(6')-lb-cr genes on the same plasmid in an E. coli strain of animal origin.

Antiviral Drugs for Treatment of Patients Infected with Pandemic (H1N1) 2009 Virus

To the Editor: The emergence of influenza A pandemic (H1N1) 2009 virus in North America and associated illness and death suggest that humanity faces a dangerous threat. Viruses isolated from a sample of patients with confirmed cases in early phases of the outbreak demonstrated resistance to amantadine and rimantadine. At present, circulating viruses appear to be largely susceptible to the neuraminidase inhibitors oseltamivir and zanamivir, although oseltamivir resistance has been observed in recent cases in Europe, Asia, and North America (1). More recently, pandemic (H1N1) 2009 virus resistance to oseltamivir emerged during treatment of 2 immunosuppressed patients in the United States. Such cases demonstrate that oseltamivir resistance can emerge in infected persons treated with oseltamivir. To date, all isolates tested have been susceptible to zanamivir. Vaccines are being deployed in some well-resourced countries but are generally not available to the public. It appears that little if any protection is offered from previous seasonal influenza vaccines. In the spring of 1918, epidemiologic observations indicated the likely emergence and spread of another influenza virus (H1N1) that caused few deaths. However, later that year, transmission resurged and was associated in 2 waves with increased illness and deaths. We cannot predict whether the 2009 pathogen will follow a similar temporal pattern and evolve toward increased virulence. Even if vaccine development and delivery could be achieved within 6 months, an aggressive schedule, large supplies of vaccine against pandemic (H1N1) 2009 may not be available until late 2009. Antiviral drugs are used to treat patients with strongly suspected or confirmed influenza. However, until a vaccine is available, specific protection by pharmaceutical products is limited to antiviral drugs. Nonpharmaceutical interventions are also available for prevention. Some governments and organizations are taking steps that would enable mass administration of these drugs (2). This administration may prove problematic. A recent study showed that schoolchildren may incompletely adhere to oseltamivir prophylaxis instructions (3). If other groups are given oseltamivir prophylaxis, they cannot necessarily be expected to follow administration guidelines; compliance with taking the recommended number of doses at appropriate times is difficult to enforce. Moreover, even when compliance is high, oseltamivir prophylaxis may fail (4). The first viable oseltamivir-resistant human influenza viruses (H1N1) emerged and became prevalent in the United States and Europe in the 2007–08 influenza season, and prevalence of such viruses has continued in 2009. The potential for overuse of antiviral drugs, especially oseltamivir, to select for existing antiviral drug-resistant strains is unknown. Ecologic studies suggest a lack of association between prevalence of oseltamivir use and prevalence of oseltamivir resistance (5). However, examination of seasonal influenza virus isolates obtained before introduction of oseltamivir showed an absence of resistance (6), leading some to conclude that antiviral monotherapy leads to selection pressure for resistance (7). Regardless of origin of resistance, recent seasonal influenza viruses (H1N1) of the A/Brisbane/57/2007 lineage from around the world display such resistance. A similar resistance pattern could occur with pandemic (H1N1) 2009 virus. Regardless of the mutational mechanism for antiviral drug resistance, mass use of antiviral drugs could potentially lead to selection pressure for drug-resistant viruses (7). Experience with seasonal influenza demonstrated the fitness of some oseltamivir-resistant strains (8). Moreover, modeling studies suggest that antiviral-resistant strains may spread rapidly and markedly affect pandemic outcomes (9). What are we to do? Until a vaccine is available, combination antiviral therapy and rapid diagnostic testing may be needed (7). Given the recently described low sensitivity of currently available rapid tests, applying such assays to all patients is problematic (10). If rapid testing has a role, it should be used in testing persons at highest risk for developing influenza complications. However, early empiric therapy based on clinical manifestations and knowledge of circulating strains is likely more appropriate than reliance on tests with low sensitivity. Updated guidelines recently issued by the World Health Organization (www.who.int/csr/resources/publications/swineflu/h1n1_guidelines_pharmaceutical_mngt.pdf) and the Centers for Disease Control and Prevention (www.cdc.gov/h1n1flu/recommendations.htm) for prophylaxis should be followed to keep resistance in check and save the lives of patients. A widely administered protective vaccine is needed to prevent transmission and infection and preserve the efficacy of antiviral agents. Indiscriminant administration of these agents could support proliferation of antiviral resistance in pandemic (H1N1) 2009 virus or an evolved variant. Appropriate use of antiviral chemotherapy is complex. Identifying the groups at high risk for serious illness for drug therapy and appropriate antiviral therapy in situations of co-circulation of seasonal and pandemic (H1N1) viruses with various susceptibility patterns needs elucidation. Without clear evidence-based guidance, a global public health disaster could occur if pandemic (H1N1) 2009 reemerges later this year with higher virulence or widespread antiviral drug resistance.

Antibiotic Resistant Salmonella And Escherichia Coli Isolated From Day-Old Chicks, Vom, Nigeria

Reports of large scale mortality of day-old-chicks were received at the National Veterinary Research Institute, Vom, Nigeria in 2007 to 2008. We investigated the cause of death using several virological and bacteriological techniques, isolated the pathogenic agents and carried out sensitivity tests. Our investigation revealed that Escherichia coli and Salmonella organisms were isolated in the outbreaks. A pattern of antibiotic resistance that seems to be increasing was also found. Considering the role of chickens and its products in the human food chain in Nigeria; and the close interaction between poultry and man, these resistant organisms may pose dangers to humans through the food chain or zoonotic infection and precipitate a similar pattern of resistance in man. We advocated for informed use of antibiotics in the food animals, especially poultry.

Escherichia coliandKlebsiella pneumoniaeCarbapenemase in Long-term Care Facility, Illinois, USA

To the Editor: Escherichia coli harboring Klebsiella pneumoniae carbapenemases (KPCs) are now rarely being reported. Worldwide, KPC-2 has been detected in Israel and the People’s Republic of China (1,2). Within the United States, carbapenem-resistant E. coli carrying blaKPC has been isolated in New Jersey (3) and Cleveland, Ohio (4), and 7 carbapenem-resistant E. coli isolates were obtained from 3 different hospitals in Brooklyn, New York (5). Urban et al. (6) recently reported 9 KPC-2 and KPC-3 carbapenemases in urinary E. coli isolates from 7 long-term care facilities. We report such an isolate from a resident of a long-term care facility. This case involved a 68-year-old female resident of a long-term care facility in Centralia, Illinois, who had multiple chronic medical problems, including cerebral palsy, a seizure disorder, and recurrent urinary tract infections. A urine culture grew >105 CFU/mL of E. coli susceptible to amikacin, gentamicin, tobramycin, piperacillin/tazobactam, trimethoprim/sulfamethoxazole, imipenem, and nitrofurantoin. Tigecycline susceptibility was not determined. Trimethoprim/sulfamethoxazole therapy was initiated. Follow-up urine culture almost 3 weeks later again grew >105 CFU/mL of E. coli, now susceptible to amikacin, gentamicin, tobramycin, nitrofurantoin, and tigecycline. The isolate was resistant to imipenem and meropenem. A modified Hodge test demonstrated production of a carbapenemase (7), and the blaKPC gene was detected by PCR at the Centers for Disease Control and Prevention (CDC). The patient was treated with a 10-day course of nitrofurantoin, 100 mg by gastrostomy tube 2× per day. Chart review indicated that contact precautions were instituted only after discovery of the second E. coli isolate. Seventeen days later, a repeat urine culture grew >105 CFU/mL of K. pneumoniae susceptible only to amikacin, gentamicin, tobramycin, and tigecycline. No treatment was given. Follow-up urine culture grew >105 CFU/mL of K. pneumoniae again with a similar resistance pattern. The modified Hodge test result was positive (7) and was confirmed as blaKPC positive by PCR at CDC. The resident was transferred to an acute care facility for further evaluation and was treated with amikacin. At completion of therapy, a repeat urine culture was negative for organisms. Our case, like that of Urban et al. (6), involved a urinary isolate from a resident of a long-term care facility. As increasing numbers of resistant gram-negative rods colonize such patients, the patients may acquire a bacterium carrying a KPC plasmid conferring broad-spectrum resistance as described in our patient. These plasmids may then be laterally transferred to other gram-negatives, which may have occurred in this case. Our case underscores the gravity of the evolutionary process of emergent, multidrug–resistant enterobacteriaceae. Even though E. coli strains that harbor carbapenemase genes are not ubiquitous, additional therapeutic interventions are needed to prevent the spread of these bacteria, which are likely to infect increasing numbers of patients.

In Vivo and In Vitro Efficacy of Amodiaquine againstPlasmodium falciparumin an Area of Continued Use of 4‐Aminoquinolines in East Africa

In light of reports of increasing resistance of parasites to amodiaquine in African countries in which Plasmodium falciparum is endemic as well as the paucity of recent in vitro sensitivity data, we assessed the in vivo and in vitro sensitivity to amodiaquine of P. falciparum isolates from 128 pediatric outpatients (0.5-10 years old) in Pingilikani, Kilifi District, Kenya, who were treated with amodiaquine (10 mg/kg/day for 3 days). The polymerase chain reaction-corrected parasitological cure rate on day 28 (by Kaplan-Meier analysis) was 82% (95% confidence interval [CI], 74%-88%). Twenty-six percent (17/66) of tested pretreatment P. falciparum field isolates had 50% in vitro growth inhibition at concentrations of N-desethyl-amodiaquine (DEAQ)-the major biologically active metabolite of amodiaquine-above the proposed resistance threshold of 60 nmol/L, but baseline median DEAQ 50% inhibitory concentration values were not associated with subsequent risk of asexual parasite recrudescence (29 nmol/L [95% CI, 23-170 nmol/L] and 34 nmol/L [95% CI, 30-46 nmol/L] for patients with and those without recrudescences, respectively). The median absolute neutrophil count dropped by 1.3 X 10(3) cells/microL (95% CI, -1.7 X 10(3) to -0.7 X 10(3) cells/microL) between days 0 and 28. The high prevalence of in vitro and in vivo resistance precludes the use of amodiaquine on its own as second-line treatment. These findings also suggest that the value of amodiaquine combinations as first- or second-line treatment in areas with similar patterns of 4-aminoquinoline resistance should be reassessed.

A survey of wild-type strains of Drosophila melanogaster for resistance to malathion and phenylthiocarbamide (PTC)1

A survey of 33 wild-type strains of D. melanogaster for resistance to PTC and malathion has revealed a tendency for strains to be resistant to one, the other, or neither of these compounds. Similar inverse relationships have been reported previously for PTC and DDT, BHC, parathion, and phenylurea. D. simulans may not exhibit similar inverse resistance patterns.

Resistance pattern of cytomegalovirus (CMV) after oral valganciclovir therapy in transplant recipients at high-risk for CMV infection

In transplant recipients, cytomegalovirus (CMV) resistance to antivirals causes an increasing problem. Here we report the clinical, therapeutic, and virological characteristics of 11 cases of CMV resistance among transplant recipients at high-risk for CMV infection and receiving valganciclovir as a prophylactic, preemptive or maintenance therapy. Active CMV infection was monitored by viral DNA quantification in whole blood, and CMV resistance was assessed by UL97 and UL54 viral gene sequencing. For 10 patients, ganciclovir resistance detected after valganciclovir therapy was associated with one mutation within UL97 phosphotransferase located at codons 460 and 592-603, which constitutes a similar pattern of resistance to what has been reported previously in AIDS patients treated with valganciclovir. For the last patient, two mutations in UL97 and UL54 genes were identified. The start of valganciclovir maintenance treatment after an intravenous curative treatment while CMV DNA is still detectable in peripheral blood might represent a risk factor for the emergence of CMV resistance. The possible emergence of CMV resistance in transplant recipients at high-risk for CMV infection who receive valganciclovir therapy should be taken into account. Among those patients, CMV infection has to be closely monitored in order to detect promptly the emergence of drug-resistance.

Antimicrobial resistance in selected bacteria from poultry

This paper reviews the present state of antimicrobial resistance (AMR) in the zoonotic bacteria Salmonella, Campylobacter jejuni and Campylobacter coli, and in Escherichia coli from chickens and turkeys. For Salmonella, the frequencies and patterns of AMR vary depending on time, region, serovar, the particular farm, layers versus broilers, and the antimicrobial agent. There is usually a higher frequency of AMR in Salmonella from turkeys compared with Salmonella from chickens. Clonal and horizontal transmission of AMR occur and there is concern about the spread of transmissible plasmids that encode extended spectrum cephalosporinases. Resistance to fluoroquinolones is generally low. For Campylobacter, resistance to tetracycline is usually at moderate to high frequency, resistance to quinolones/fluoroquinolones varies from low to high, and resistance to macrolides is usually low. There are high levels of fluoroquinolone resistance in some countries. Avian pathogenic E. coli are often highly resistant, especially to tetracycline, streptomycin, and sulfonamides. Plasmid-mediated resistance is common. High levels of resistance to ciprofloxacin have been reported from China. Commensal E. coli from poultry have similar patterns of resistance but at lower frequencies. Integron associated resistance occurs commonly in Salmonella and E. coli but has not been detected in Campylobacter.

Substitution of Four Residues Revealed by High-Throughput Screening of Human Factor VIII A2 Domain Generated a Recombinant Molecule That Escapes to Anti-Factor VIII Antibodies

Using Massive Mutagenesis technique® we performed a high-throughput alanine substitution of 206 residues between aminoacids 376 to 649 from factor VIII (FVIII) A2 domain. The pattern of activity and the levels of production of FVIII mutants were assessed following transient expression in COS-1 cells. FVIII mutants that kept at least 50% of wild-type activity were then screened in an inhibitor assay against total immunoglobulin G (IgG) fractions from patients with severe hemophilia A who had developed inhibitory antibodies (n=4; range 6–15 BU/mL) or a non immune IgG as control. In this assay, the cell culture supernatants containing FVIII were incubated in a volume of FVIII-depleted plasma for 1h30 in the presence of IgG. The residual activity was then measured in a chronometric assay. No single mutations were able to significantly allow FVIII to escape inhibitors. Four mutations (S409A, L462A, E507A, L629A) having a tendency to resist to inhibitors were selected and recombined two by two leading to a significant but insufficient resistance to anti-FVIII antibodies. The effect of the mutations was additive since a molecule (FVIII-4A2) combining the 4 substitutions significantly resisted to the inhibitory antibodies. Residual activity of FVIII-4A2 ranged from 8% to up to 82% of the initial activity depending on the inhibitor plasma whereas this residual activity never exceeded 30% for control wild-type FVIII. Following production by CHO cells, purified FVIII-4A2 demonstrated a similar pattern of resistance to the four IgG fractions already assayed. FVIII-4A2 was then assayed against 11 additional unrelated inhibitors (range 3–2662 BU/mL) and displayed also a resistance against 10 out of the 11 IgG fractions. The resistance was in all case only partial in relation with the likely presence of anti-C2 and/or anti-A3-C1 inhibitors within the IgG fractions. As detected in a solid-phase assay, the decrease in inhibitory effect was for some of the IgG fractions partly related to a decrease in their binding capacity. As a control experiment, FVIII-4A2 was poorly recognized by the monoclonal antibody GMA012 directed against the A2 domain. In contrast, the binding to ESH4, an anti-C2 monoclonal antibody was not affected. Such combination of mutations opened the perspective for the generation of a recombinant FVIII molecule that can be used as an effective substitutive FVIII therapy in patients with inhibitors.