Low-Level Antibiotic Resistance among Staphylococcus aureus and Gram-Negative Pathogens from Infected Skin and Soft Tissues in Rural Kenya

Introduction: Bacterial skin and soft tissue infections (SSTIs) are a cause of frequent inpatient and outpatient care visits whose causative agents are associated with a high antimicrobial resistance burden. For insights on antimicrobial susceptibilities in a rural setting, we examined specimens from suspected SSTIs from two public health facilities in Kenya. We additionally assessed antibiotic use, appropriateness of empiric therapy and risk factors for SSTI. Methodology: Between 2021 and 2023, 265 patients at Kisii and Nyamira County Referral hospitals were enrolled. Wound swabs/aspirates were collected and processed following standard microbiological procedures. Identification and antimicrobial susceptibility were performed using the VITEK 2 Compact platform. Demographic, clinical, and microbiological data were analyzed with R Statistical software. Results: S. aureus was isolated in 16.2% (43/265) of patients with a methicillin resistance (MRSA) proportion of 14% (6/43). While 13/15 drugs elicited susceptibilities ranging from 84% - 100%, penicillin (16%) and trimethoprim-sulfamethoxazole [TMP-SXT] (23%) yielded the lowest susceptibilities. Escherichia coli (n = 33), Klebsiella pneumoniae (n = 8), Pseudomonas aeruginosa (n = 8), and Citrobacter species (n = 4) were the most commonly isolated gram-negative species. Gram-negative strains showed high susceptibilities to most of the tested drugs (71% - 100%) with the exception of ampicillin (18%), TMP-SXT (33%), and first and second generation cephalosporins. Conclusions: The low MRSA prevalence and generally high antibiotic susceptibilities for S. aureus and gram-negative bacteria present opportunities for antibiotic stewardship in the study setting. Diminished susceptibilities against penicillin/ampicillin and TMP-SXT accord with prevailing local data and add a layer of evidence for their cautious empiric use.

Phenotypic and Molecular Characterization of Staphylococcaceae and Enterobacteriaceae Species Isolated from Smoked, Dried, and Braised Fish Marketed in Ouagadougou

Background: To preserve its nutritional properties, fish must have good sanitary quality. The objective of this study was to investigate some pathogens contaminating smoked, dried, and braised fish marketed in Ouagadougou. Methodology: Potential pathogens of Enterobacteriaceae and Staphylococcus were screened in eight (8) species of processed fish. The investigation of the germs was carried out following the normative methods of microbiology. The identities of the strains were determined by API 20 E (BioMerieux S.A., France) and API STAPH (BioMerieux S.A., France) kits for Enterobacteriaceae and Staphylococcus species respectively. The uidA gene profile in Escherichia coli isolates was determined by simplex PCR. The identity of Staphylococcus aureus was confirmed by amplification of specific 23S rDNA regions and nuc gene profile with PCR. Results: A total of 235 fish samples were analyzed. A diversity of Enterobacteriaceae and Staphylococcus was detected. Twenty species of Enterobacteriaceae were identified among which, the most frequent were Escherichia coli, Salmonella sp, Raoultella ornithinolytica and Serratia odorifera, respectively in 22.6%, 4.3%, 28.9%, 17.4% of the samples analyzed. However, eleven species of Staphylococcus were identified among which, Staphylococcus xylosus, Staphylococcus aureus, Staphylococcus lugdunensis, and Staphylococcus sciuri were the most frequent with respective percentages of 47.7%, 23.4%, 12.8% and 10.6% of samples. For all the samples, the species frequently isolated were: Raoultella ornithinolytica, Escherichia coli, Serratia odorifera, Staphylococcus aureus, Staphylococcus xylosus, and Staphylococcus lugdunensis. The uidA gene specific to Escherichia coli was detected in 82.85% of strains (29/35). Amplification of the specific 23S rDNA region using staur primers was observed in 98% (49/50) of the isolated Staphylococcus aureus strains and the nuc gene was detected in 86% of Staphylococcus aureus strains. Conclusion: The isolated bacteria are potential pathogens involved in foodborne illnesses and intoxications. Effective sanitary safety systems must be implemented to guarantee the sanitary quality of fish supplied to consumers.

Phenotypic Characterization of Carbapenemase-Producing Enterobacteriaceae Strains in a Referral Teaching Hospital in Yaoundé, Cameroon

Background: Carbapenemase-producing Enterobacteriaceae (CPE) are an important and increasing threat to global health. They are nowadays more encountered routinely in hospitals and cause high morbidity and mortality due to limited therapeutic alternatives. This study sought to determine the prevalence of CPE in Yaoundé teaching hospital, Cameroon, and the associated risk factors. Materials and Method: To achieve this goal, a descriptive cross-sectional study coupled to an analytical component with consecutive collection of Enterobacteria strains was carried out during a three-month period (from 27th July to 24th October 2018) in the University Teaching Hospital of Yaoundé, Cameroon. The oxidase and biochemical identification tests using a miniaturized Api 20 E system were performed on colonies grown on Eosin Methylene Blue (EMB) medium and subcultured on nutrient agar. Drug susceptibility testing was carried out according to the Antibiogram Committee of the French Society of Microbiology (CA-SFM 2018.V.2.0). The detection of carbapenemase production was performed by the CA-SFM 2018 algorithm for the screening of carbapenemase-producing enterobacteriaceae and its classification by inhibitory synergy tests. Results: Out of the 104 isolates, Escherichia coli (50%) was the most prevalent species, followed by Klebsiella pneumoniae (37.5%) and Citrobacter frendii (12.5%). Drugs susceptibility patterns showed a high resistance to penicillins group (97.4% to amoxicillin), cephalosporins (68.4% to cefotaxim, 58.1% to cefixim, 60.7% to ceftazidim, 57.1% of cefoxitin) and aztreonam (55.7%). However, 11.9% carbapenems related resistance was noticed: 14.4% to imipenem, 13.8% to ertapenem and 7.5% to meropenem. Numerous co-resistance to quinolones (65.8%), fluoroquinolones (49.6%), aminoglycosides (49.6%) and cotrimoxazole (71.8%) were also observed. From 104 isolates, AmpC production represented 23.08% (25/104) and 36.54% (38/104) were ESBL-isolates. The overall prevalence of CPE was 25% (26/104) with K.pneumoniae predominant (61.53%). Besides, Class A and class B carbapenemase were mainly produced with respectively 20% (21/104) and 5% (5/104). Univariate analysis revealed a significant association of carbapenemase production to Klebsiella pneumoniae (p = 0.01), ESBL and AmpC production ((P = 0.01 and P = 0.001 respectively) while that association was only significant to Klebsiella spp (p = 0.04) and AmpC production (p = 0.02) in multivariate analysis. Conclusion: The multi-resistance of Enterobacteriaceae to antibiotics in Cameroon has considerably increased. More attention should be paid to those bacteria to stall antimicrobial resistance spread.

Bacteriophage therapy against Enterobacteriaceae

The Enterobacteriaceae are a class of gram-negative facultative anaerobic rods, which can cause a variety of diseases, such as bacteremia, septic arthritis, endocarditis, osteomyelitis, lower respiratory tract infections, skin and soft-tissue infections, urinary tract infections, intra-abdominal infections and ophthalmic infections, in humans, poultry, animals and fish. Disease caused by Enterobacteriaceae cause the deaths of millions of people every year, resulting in enormous economic loss. Drug treatment is a useful and efficient way to control Enterobacteriaceae infections. However, with the abuse of antibiotics, drug resistance has been found in growing number of Enterobacteriaceae infections and, as such, there is an urgent need to find new methods of control. Bacteriophage therapy is an efficient alternative to antibiotics as it employs a different antibacterial mechanism. This paper summarizes the history of bacteriophage therapy, its bacteriallytic mechanisms, and the studies that have focused on Enterobacteriaceae and bacteriophage therapy.

Treatment of sepsis: What is the antibiotic choice in bacteremia due to carbapenem resistant Enterobacteriaceae?

Sepsis is one of the major challenges of today. Although gram-positive bacteria related infections are more prevalent in hospital setting, the highest mortality rate is associated with gram-negative microorganisms especially Enterobacteriaceae. Enterobacteriaceae, including Escherichia coli, Klebsiella spp., Proteus spp., Enterobacter spp. and Serratia spp. Resistance to β-lactams in Enterobacteriaceae is primarily attributed to the production of B-lactamase enzymes with subsequent antibiotic hydrolysis and to a lesser extent by alteration of efflux pump or porins expression. Carbapenem resistant Enterobacteriaceae(CRE) and Acinetobacter baumannii are the most notorious pathogens due to the high incidence of morbidity and mortality especially in the immunocompromised patients in the intensive care unit. The most appropriate antimicrobial therapy to treat CRE is still controversial. Combination therapy is preferred over monotherapy due to its broad-spectrum coverage of micro-organisms, due to its synergetic effect and to prevent development of further resistance. Current suggested therapies for CRE resistance as well as promising antibiotics that are currently under investigation for winning the war against the emerging CRE resistance are reviewed and discussed.

Risk of transmission of carbapenem-resistant Enterobacteriaceae and related “superbugs” during gastrointestinal endoscopy

To evaluate the risk of transmission of carbapenem-resistant Enterobacteriaceae(CRE) and their related superbugs during gastrointestinal(GI) endoscopy. Reports of outbreaks linked to GI endoscopes contami-nated with different types of infectious agents, includ-ing CRE and their related superbugs, were reviewed. Published during the past 30 years, both prior to and since CRE's emergence, these reports were obtained by searching the peer-reviewed medical literature(via the United States National Library of Medicine's "MEDLINE" database); the Food and Drug Administration's Manu-facturer and User Facility Device Experience database, or "MAUDE"; and the Internet(via Google's search engine). This review focused on an outbreak of CRE in 2013 following the GI endoscopic procedure known as endoscopic retrograde cholangiopancreatography, or ERCP, performed at "Hospital X" located in the sub-urbs of Chicago(IL; United States). Part of the largest outbreak of CRE in United States history, the infection and colonization of 10 and 28 of this hospital's patients, respectively, received considerable media attention and was also investigated by the Centers for Disease Con-trol and Prevention(CDC), which published a report about this outbreak in Morbidity and Mortality WeeklyReport(MMWR), in 2014. This report, along with the results of an independent inspection of Hospital X's in-fection control practices following this CRE outbreak, were also reviewed. While this article focuses primar-ily on the prevention of transmissions of CRE and their related superbugs in the GI endoscopic setting, some of its discussion and recommendations may also apply to other healthcare settings, to other types of flexible endoscopes, and to other types of transmissible infec-tious agents. This review found that GI endoscopy is an important risk factor for the transmission of CRE and their related superbugs, having been recently as-sociated with patient morbidity and mortality following ERCP. The CDC reported in MMWR that the type of GI endoscope, known as an ERCP endoscope, that Hospi-tal X used to perform ERCP in 2013 on the 38 patients who became infected or colonized with CRE might be particularly challenging to clean and disinfect, because of the complexity of its physical design. If performed in strict accordance with the endoscope manufacturer's labeling, supplemented as needed with professional organizations' published guidelines, however, current practices for reprocessing GI endoscopes, which include high-level disinfection, are reportedly adequate for the prevention of transmission of CRE and their related superbugs. Several recommendations are provided to prevent CRE transmissions in the healthcare setting. CRE transmissions are not limited to contaminated GI endoscopes and also have been linked to other reusable flexible endoscopic instrumentation, including broncho-scopes and cystoscopes. In conclusion, contaminated GI endoscopes, particularly those used during ERCP, have been causally linked to outbreaks of CRE and their related superbugs, with associated patient morbidity and mortality. Thorough reprocessing of these complex reusable instruments is necessary to prevent disease transmission and ensure patient safety during GI endos-copy. Enhanced training and monitoring of reprocessing staffers to verify the proper cleaning and brushing of GI endoscopes, especially the area around, behind andnear the forceps elevator located at the distal end othe ERCP endoscope, are recommended. If the ERCPendoscope features a narrow and exposed channel thathouses a wire connecting the GI endoscope's controhead to this forceps elevator, then this channel's com-plete reprocessing, including its flushing with a deter-gent using a procedure validated for effectiveness, is also emphasized.

bla_(CTX-M),bla_(TEM),and bla_(SHV) in Enterobacteriaceae from North-Indian tertiary hospital:high occurrence of combination genes

Objective:To delineate the frequency of occurrence of blaCTX-M,blaTEM,and blaSHV in Enterobacteriaceae from North-Indian tertiary hospital.Methods:A random collection of a subset of 45 Escherichia coli（E.coli） and 28 Klebsiella pneumoniae（K.pneumoniae） that was resistant to a third generation cephalosporin and obtained during 2007-2008 was selected for detailed screening for blaCTX-M,blaTEM,and blaSHV by monoplex PCRs.The isolates demonstrating the presence of blaCTX-M alleles were characterized for the specific CTX-M-genogroup by using a multiplex PCR.Results:Resistance to cefoperazone,ceftazidime,ceftriaxone,cefotaxime, cefoxitin and piperacillin was 100%each in K.pneumoniae isolates,whereas these resistancerates for E.coli isolates were 93.1%,83.8%,91.9%,93.6%,97.3%and 97.1%,respectively. Concomitant resistance to aminoglycosides,quinolones and aztreonam was also noticed.Presence of any of the bla genes(blaCTX-M,blaTEM,and blaSHV) was noticed in a total of 28（38.4%） isolates of the 73 isolates studied.Many isolates demonstrated occurrence of these genes in various combinations.blaCTX-M,blaTEM,and blaSHV were noticed in 28.8%,10.9%and 13.7%isolates, respectively.Multiplex PCR in blaCTX-M harboring isolates demonstrated the presence of CTX-MGenogroup -1 and sequencing for the specific CTX-M-type revealed presence of CTX-M-15 type. RAPD typing showed wide diversity in isolates.Conclusions:This is amongst the premier report describing the simultaneous occurrence of bloTEM,blaSHV,and blaampC in Indian Enterobacteriaceae and that wider dissemination of these genes,as demonstrated by diversity of isolates,raises concern and emphasizes a need for extensive search for the presence of these gene pools in Indian subcontinent.

Increasing secondary bacterial infections with Enterobacteriaceae harboring bla_(CTX-M-15) and bla_(CMY-6) in patients with bronchogenic carcinoma:an emerging point of concern

Objective:To look for secondary bacterial infections in bronchogenic carcinoma（BCA） with resistant organisms harboring bla genes considering the paucity of relevant studies.Methods: A total of 137 confirmed cases of BCA and 34 healthy volunteers were studied for the occurrence and prevalence of blaCTX-M and and blaAmpC harboring-enterobacteriaceae.A subset of these patients（n=69） was previously reported for the secondary infection with the Aspergillus species. Bronchoalveolar lavages（BAL） were subjected for bacterial and fungal cultures and the bacterial isolates were screened by multiplex PCRs for the presence of blaCTX-M and blaAmpC.The isolates were also screened for the association of insertion sequence（IS26） by PCR and characterized by RAPD for any clonal relatedness.Results:A total of 143 bacterial isolates were obtained from 137 BAL specimens of BC,patients.The Enterobacteriaceae-isolates were multidrug-resistant showing concomitant resistance to fluoroquinolones and aminoglycosides.Both blaCTX-M and blaAmpC of CIT family were detected in 77.4%and 27.4%isolates,respectively.Sequencing revealed the presence of blaCTX-M-15 and blaCMY-6.Twenty one percent of the isolates were simultaneously harboring blaampC and blaCTX-M-15.IS26 PCR and RAPD typing revealed the presence of diverse bacterial population but no predominant clone was identified.The present study also suggests strong association of aspergillosis with lung cancer and further strengthens the potential use of non-validated serological tests suggested earlier.Conclusions:We emphasize that all patients of bronchogenic carcinoma should also be screened for secondary bacterial infections,along with secondary fungal infections,so as to introduce early and specific antimicrobial therapy and to prevent unwanted deaths.

High mortality associated with gram-negative bacterial bloodstream infection in liver transplant recipients undergoing immunosuppression reduction

BACKGROUND Immunosuppression is an important factor in the incidence of infections in transplant recipient.Few studies are available on the management of immunosuppression(IS)treatment in the liver transplant(LT)recipients complicated with infection.The aim of this study is to describe our experience in the management of IS treatment during bacterial bloodstream infection(BSI)in LT recipients and assess the effect of temporary IS withdrawal on 30 d mortality of recipients presenting with severe infection.AIM To assess the effect of temporary IS withdrawal on 30 d mortality of LT recipients presenting with severe infection.METHODS A retrospective study was conducted with patients diagnosed with BSI after LT in the Department of Liver Surgery,Renji Hospital from January 1,2016 through December 31,2017.All recipients diagnosed with BSI after LT were included.Univariate and multivariate Cox regression analysis of risk factors for 30 d mortality was conducted in the LT recipients with Gram-negative bacterial(GNB)infection.RESULTS Seventy-four episodes of BSI were identified in 70 LT recipients,including 45 episodes of Gram-positive bacterial(GPB)infections in 42 patients and 29 episodes of GNB infections in 28 patients.Overall,IS reduction(at least 50%dose reduction or cessation of one or more immunosuppressive agent)was made in 28(41.2%)cases,specifically,in 5(11.9%)cases with GPB infections and 23(82.1%)cases with GNB infections.The 180 d all-cause mortality rate was 18.5%(13/70).The mortality rate in GNB group(39.3%,11/28)was significantly higher than that in GPB group(4.8%,2/42)(P=0.001).All the deaths in GNB group were attributed to worsening infection secondary to IS withdrawal,but the deaths in GPB group were all due to graft-versus-host disease.GNB group was associated with significantly higher incidence of intra-abdominal infection,IS reduction,and complete IS withdrawal than GPB group(P<0.05).Cox regression showed that rejection(adjusted hazard ratio 7.021,P=0.001)and complete IS withdrawal(adjusted hazard ratio 12.65,P=0.019)were independent risk factors for 30 d mortality in patients with GNB infections after LT.CONCLUSION IS reduction is more frequently associated with GNB infection than GPB infection in LT recipients.Complete IS withdrawal should be cautious due to increased risk of mortality in LT recipients complicated with BSI.

Characterization of NDM-5-producing Enterobacteriaceae isolates from retail grass carp(Ctenopharyngodon idella) and evidence of blaNDM-5-bearing IncHI2 plasmid transfer between ducks and fish

We aimed to characterize NDM-5-producing Enterobacteriaceae from aquatic products in Guangzhou,China.A total of 196 intestinal samples of grass carp collected in 2019 were screened for carbapenemase genes.Characterization of bla_(NDM-5) positive isolates and plasmids was determined by antimicrobial susceptibility testing,conjugation experiments,Illumina HiSeq,and Nanopore sequencing.One Citrobacter freundii and six Escherichia coli strains recovered from seven intestinal samples were verified as bla_(NDM-5) carriers(3.57%,7/196).The bla_(NDM-5) genes were located on the lncX3(n=5),lncHI2(n=1),or lncHI2-lncF(n=1)plasmids.All bla_(NDM-5)-bearing plasmids were transferred by conjugation at frequencies of~10^(-4)-10^(-6).Based on sequence analysis,the lncHI2 plasmid pHNBYF33-1 was similar to other bla_(NDM-5)-carrying lncHI2 plasmids deposited in GenBank from Guangdong ducks.In all lncHI2 plasmids,bla_(NDM-5)was embedded in a novel transposon,Tn7057(IS3000-△ISAba125-IS5-△ISAba125-bla_(NDM-5)-bleMBL-trpF-tat-△dct-IS26-△umuD-△ISKox3-IS3000),which was identical to the genetic structure surrounding bla_(NDM-5)found in some IncX3 plasmids.The lncHI2-lncF hybrid plasmid pHNTH9F11-1 was formed by homologous recombination of the bla_(NDM-5)-carrying lncHI2 plasmid and a heavy-metal-resistant IncF plasmid through△Tn1721 To the best of our knowledge,this is the first report on the characterization of bla_(NDM-5)-bearing plasmids in fish in China.The lncHI2 plasmid pHNBYF33-1 may be transmitted from ducks,considering the common duck-fish freshwater aquaculture system in Guangdong.Tn7051 is likely responsible for the transfer of bla_(NDM-5) from lncX3 to lncHI2 plasmids in Enterobacteriaceae,resulting in the expansion of transmission vectors of bla_(NDM-5).

Genomic and Phenotypic Diversity of Carbapenemase-Producing Enterobacteriaceae Isolates from Bacteremia in China: A Multicenter Epidemiological, Microbiological, and Genetic Study

Carbapenemase-producing Enterobacteriaceae(CPE) isolates are recognized as one of the most severe threats to public health. However, the population structure and genetic characteristics of CPE isolates among bloodstream infections(BSIs) are largely unknown. To address this knowledge gap, in this study,we included patients with clinically significant BSIs due to Enterobacterales isolates, recruited from 26 sentinel hospitals in China(2014–2015). CPE isolates were microbiologically and genomically characterized,including their susceptibility profiles, molecular typing, phylogenetic features, and genetic context analysis of carbapenemase-encoding genes. Of the 2569 BSI Enterobacterales isolates enrolled, 42(1.6%) were carbapenemase-positive. Moreover, among the 2242 investigated isolates, 1111(49.6%) extendedspectrum β-lactamase(ESBL)-producing isolates were identified in Escherichia coli(E. coli), Klebsiella pneumoniae(K. pneumoniae), Proteus mirabilis(P. mirabilis), and Klebsiella oxytoca. Whole genome sequencing analysis showed the clonal spread of K. pneumoniae carbapenemase(KPC)-2-producing K. pneumoniae sequence type(ST) 11 and New Delhi metallo-β-lactamase(NDM)-5-producing E. coli ST167 in our collection. Plasmid analysis revealed that carbapenemase-encoding genes were located on multiple plasmids. A high prevalence of biofilm-encoding type 3 fimbriae clusters and yesiniabactin-associated genes was observed in K. pneumoniae isolates. This work demonstrates the high prevalence of ESBLs and the wide dissemination of CPE among BSI isolates in China, which represent real clinical threats. Moreover, our findings first illustrate a more comprehensive genome scenario of CPE isolates among BSIs. The clonal spread of KPC-2-producing K. pneumoniae ST11 and NDM-5-producing E. coli ST167 needs to be closely monitored.

Isolation, Characterization and Antimicrobial Resistance Patterns of Lactose-Fermenter Enterobacteriaceae Isolates from Clinical and Environmental Samples

The lactose-fermenter Enterobacteriaceae are the most frequent cause of clinical infection in our country. The objective of this study was to isolate and identify the most common lactose-fermenter Enterobacteriaceae from clinical samples, including urine, blood, wounds, and sputum, obtained from the local hospital and from environmental samples from a chicken farm, agriculture soil, and water from the Tigris River in Baghdad City. The study also aimed at establishing the antibiotic resistance patterns of the isolated bacteria. A total of 155 bacterial isolates were identified from 10 genera according to the Vitek 2 system. The most common bacterial isolates from the clinical and environmental samples were Escherichia coli and Klebsiella pneumoniae, respectively. The antibiotic resistance patterns showed that all clinical and environmental isolates were multidrug resistant to β-lactam (except carbapenems) drug and aminoglycosides and more sensitive to carbapenems.

Association between infections caused by multidrug-resistant gram-negative bacteria and mortality in critically ill patients

The incidence of gram-negative multidrug-resistant(MDR) bacterial pathogens is increasing in hospitals and particularly in the intensive care unit(ICU) setting. The clinical consequences of infections caused by MDR pathogens remain controversial. The purpose of this review is to summarize the available data concerning the impact of these infections on mortality in ICU patients. Twenty-four studies, conducted exclusively in ICU patients, were identified through Pub Med search over the years 2000-2015. Bloodstream infection was the only infection examined in eight studies, respiratory infections in four and variable infections in others. Comparative data on the appropriateness of empirical antibiotic treatment were provided by only seven studies. In ten studies the presence of antimicrobial resistance was not associated with increased mortality; on the contrary, in other studies a significant impact of antibiotic resistance on mortality was found, though, sometimes, mediated by inappropriate antimicrobial treatment. Therefore, a direct association between infections due to gram-negative MDR bacteria and mortality in ICU patients cannot be confirmed. Sample size, presence of multiple confounders and other methodological issues may influence the results. These data support the need for further studies to elucidate the real impact of infections caused by resistant bacteria in ICU patients.

Seafood as a Reservoir of Gram-negative Bacteria Carrying Integrons and Antimicrobial Resistance Genes in Japan

PCR and DNA sequencing were used to screen and characterize integrons and resistance genes in Gram-negative bacteria isolated from seafood products in Japan.A total of 215 Gram-negative bacteria were isolated from local and imported seafood samples collected from retail markets in Hiroshima Prefecture.Class 1 integrons containing gene cassettes encoding resistance to trimethoprim

Impact of Polymyxin Resistance on Virulence and Fitness among Clinically Important Gram-Negative Bacteria

Humanity is facing an enormous and growing worldwide threat from the emergence of multi-drug-resistant(MDR)Gram-negative bacteria such as Escherichia coli,Klebsiella pneumoniae,and Acinetobacter baumannii.Polymyxin B and E(colistin)constitute the last-line therapies for treating MDR Gram-negative bacteria.Polymyxin is a cationic antibacterial peptide that can destroy the outer membrane of Gram-negative bacteria.With the increasing clinical application of polymyxin,however,there have been many reports of the occurrence of polymyxin-resistant Gram-negative bacteria.This resistance is mainly mediated by the modification or complete loss of lipopolysaccharide(LPS).LPS is also a virulence factor of Gram-negative bacteria,and alterations of LPS may correlate with virulence.Although it is generally believed that the biological costs associated with drug resistance may enable benign susceptible bacteria to overcome resistant bacteria when antibiotic pressure is reduced,some studies have shown that polymyxin-resistant bacteria are associated with higher virulence and greater fitness compared with their susceptible counterparts.To predict the development of polymyxin resis-tance and evaluate interventions for its mitigation,it is important to understand the relative biological cost of polymyxin resistance compared with susceptibility.The impact of polymyxin resistance mecha-nisms on the virulence and fitness of these three Gram-negative bacteria are summarized in this review.

Antimicrobial Resistance among Enterobacteriaceae Found in Chicken and Cow Droppings and Their Public Health Importance

Introduction: The recent surge in the number of antimicrobial resistant cases from hospitals and communities has created a need to study the points and sources of exposure to certain bacteria and determine their susceptibility to commonly used antibiotics. This study aimed at identifying and screening for drug-resistant Enterobacteriaceae isolated from chicken droppings and cow dungs in Onitsha, Anambra state, in the South-Eastern part of Nigeria. Methods: This is a cross-sectional descriptive study which included 50 chickens and 50 cow dung samples collected from five poultry houses and cow ranches respectively using sterile swab sticks. The samples were transported to the laboratory and processed following standard microbiological protocols. Isolates in the samples were recovered using MacConkey Agar, Eosin Methylene Blue Agar and Salmonella-Shigella Agar following standard microbiological procedures and then identified/characterized biochemically using commercial API 20E identification kits following the standard manufacturer’s protocol. Isolates were subjected to antibiotic susceptibility testing on Muller Hinton Agar using Kirby Bauer double-disc diffusion technique. The multiple antibiotics resistance index was determined as well. Isolates with reduced susceptibility to Ceftazidime were screened for extended spectrum beta-lactamase, AmpC- and metallo-beta-lactamase-production using Rosco Diagnostic kit. Results: Sixty-two (100%) Gram-negative bacteria were isolated from a total of 100 samples collected from both sites, out of which 43 (69.4%) are Enterobacteriaceae. A total of 30/43 (69.8%) Enterobacteriaceae including K. pneumoniae, S. enteritica, S. odorifera, E. coli, K. intermediate, P. stuartii, E. aerogenes, P. penneri, P. mirabilis and C. braakii were recovered from chicken droppings, whereas 13/43 (30.2%) Enterobacteriaceae including K. pneumoniae, S. enteritica, S. odorifera, E. coli, K. intermediate, P. stuartii, E. aerogenes, P. penneri, P. mirabilis and C. braakii were recovered from cow dungs. Two (12.5%) different isolates demonstrated metallo-beta-lactamase and cephalosporinase (AmpC) production. The isolates were susceptible to six antibiotics tested except Augmentin and Nitrofurantoin where the resistance is 100% and 85% respectively while Ceftriaxone and Ofloxacin had the best antibacterial activity against the isolates from both sites. Conclusion: The bacteria of public health importance isolated from these sites and their antibiogram profile have shown the need for proper monitoring and management of animal wastes in order to mitigate the threat to human health in the spirit of One Health as well as contribute to the fight against antibiotic resistance.

An Improved Approach for Rapidly Identifying Different Types of Gram-Negative Bacterial Secreted Proteins

Protein secretion plays an important role in bacterial lifestyles. In Gram-negative bacteria, a wide range of proteins are secreted to modulate the interactions of bacteria with their environments and other bacteria via various secretion systems. These proteins are essential for the virulence of bacteria, so it is crucial to study them for the pathogenesis of diseases and the development of drugs. Using amino acid composition (AAC), position-specific scoring matrix (PSSM) and N-terminal signal peptides, two different substitution models are firstly constructed to transform protein sequences into numerical vectors. Then, based on support vector machine (SVM) and the “one to one”?algorithm, a hybrid multi-classifier named SecretP v.2.2 is proposed to rapidly and accurately?distinguish different types of Gram-negative?bacterial secreted proteins. When performed on the same test set for a comparison with other methods, SecretP v.2.2 gets the highest total sensitivity of 93.60%. A public independent dataset is used to further test the power of SecretP v.2.2 for predicting NCSPs, it also yields satisfactory results.

Spontaneous bacterial peritonitis due to carbapenemase-producing Enterobacteriaceae:Etiology and antibiotic treatment

Carbapenem antibiotics were first introduced in the 1980s and have long been considered the most active agents for the treatment of multidrug-resistant gramnegative bacteria.Over the last decade,carbapenem-resistant Enterobacteriaceae(CRE)have emerged as organisms causing spontaneous bacterial peritonitis.Infections caused by CRE have shown a higher mortality rate than those caused by bacteria sensitive to carbapenem antibiotics.Current antibiotic guidelines for the treatment of spontaneous bacterial peritonitis are insufficient,and rapid deescalation of empiric antibiotic treatment is not widely recognized.This review summarizes the molecular characteristics,epidemiology and possible treatment of spontaneous bacterial peritonitis caused by CRE.

Abundance of Enterobacteriaceae in the colon mucosa in diverticular disease

AIM To compare gut bacterial diversity and amount of Enterobacteriaceae in colonic mucosa between patients with and without diverticular disease(DD).METHODS Patients in a stable clinical condition with planned elective colonoscopy were included. Blood samples and colon mucosa biopsies were collected at the colonoscopy. Study questionnaires including questions about gastrointestinal symptoms were completed by the patients and physicians. DNA from mucosa samples was isolated and the amount of Enterobacteriaceae was estimated using PCR assay. Terminal restriction frag mentlength polymorphism was applied to assess microbial diversity. Diversity was estimated by calculations of richness(number of terminal restriction fragments) and Shannon-Wiener and Simpson's indices. RESULTS A total of 51 patients were included, 16 patients with DD [68(62-76) years] and 35 controls [62(40-74) years] without any diverticula. Patients with DD had significantly higher levels of Enterobacteriaceae than those without DD(P = 0.043), and there was an inverse relationship between the amount of Enterobacteriaceae and the Simpson's index(rs =-0.361, P = 0.033) and the Shannon-Wiener index(rs =-0.299, P = 0.081). The Simpson's index(P = 0.383), Shannon-Wiener index(P = 0.401) or number of restrictions fragments(P = 0.776) did not differ between DD and controls. The majority of patients experienced gastrointestinal symptoms, and 22 patients(43.1%) fulfilled the criteria for irritable bowel syndrome, with no difference between the groups(P = 0.212). Demography, socioeconomic status, lifestyle habits, inflammatory biomarkers, or symptoms were not related to the amount of Enterobacteriaceae or bacterial diversity. CONCLUSION Patients with DD had higher amount of Enterobacteriaceae in the colon mucosa compared to patients without diverticula.

Comparative study on occurrence of class A and class Cβ-lactamase genes and their co-occurrence in Indian Enterobacteriaceae during years 2009 and 2010

Objective:To determine the occurrence of class A and class Cβ-Iactamase genes and their cooccurrence in Indian Enterobacteriaceae.Methods:52 third generation cephalosporin resistant isolates were phenotypically detected by combination disk method and screened by PCR to identify class A and class C typeβ-lactamase genes.Results:Of the 52 isolates,94.2%（49） were found harboring any of the bla?,blaCTX-M,blaSHV and blaTEM were present in 82.6%（43/52）, 59.6%（31/52）,and 42.3%（22/52） isolates,respectively.Of the 49 ESBL positive isolates 57.1% （28/49） showed co-occurrence of blaampCwith bla?.On the contrary,the collection from 2009 showed their co-occurrence in 81.4%isolates.Conclusions:The comparative study shows a downward trend for co-existence of bla? with blaampC from 2009 to 2010.Further large scale studies are needed to address the co-occurrence of class A and class Cβ-lactamases in India and the resistance trend occurring over a period of time.