Nosocomial Intravascular Catheter Infections with Extended‐spectrum Beta‐lactamase‐producing Escherichia coli in Calves after Strain Introduction from a Commercial Herd

An outbreak of intravascular catheter‐related infections by extended‐spectrum β‐lactamase (ESBL)‐producing Escherichia coli in calves in an animal teaching hospital is reported. Pulsed‐field gel electrophoresis was used for strain typing to determine the origin and dissemination of these strains. All 19 strains harboured the bla_{CTX‐M‐14,} and six strains also overexpressed their chromosomal AmpC gene. Evidence on the introduction of the strain from a beef herd, experiencing neonatal diarrhoea and increased mortality, to the clinic through admission of diarrhoeic calves was provided. Strains isolated from phlebitis cases from other herds up to 5 months later showed a high similarity with the initial strain, suggesting that the strain had become nosocomial. The catheter infections with ESBL/AmpC‐producing E. coli resulted in a prolonged hospitalization, increased anti‐microbial use and mortality. This report points towards the potential dangers of the emergence of ESBL/AmpC‐producing bacteria in susceptible food animals and warns farmers and veterinarians for the facility by which they are introduced into another environment.     

Clinico‐microbiological study of Pseudomonas aeruginosa in wound infections and the detection of metallo‐β‐lactamase production

Pseudomonas aeruginosa is a common opportunistic pathogen of humans among the Gram‐negative bacilli. Clinically, it is associated with nosocomial infections like burns and surgical‐site wound infections and remains a major health concern, especially among critically ill and immunocompromised patients. This is a prospective laboratory‐based 2 year study conducted to isolate P. aeruginosa from wound specimens and the antimicrobial susceptibility pattern with reference to metallo‐β‐lactamase (MBL) production. Two hundred and twenty‐four samples of P. aeruginosa isolated from wound specimens were included in the study. Antimicrobial susceptibility was done as per Clinical Laboratory Standard Institute (CLSI) guidelines. MBL‐producing P. aeruginosa was detected using the EDTA disk diffusion synergy test. Statistical analysis was done using the SPSS 11 package (SPSS Inc., Chicago, IL). Out of the 224 P. aeruginosa isolates, 100% were susceptible to polymyxin B and colistin, 92·8% were sensitive to imipenem, 38% showed resistance to gentamicin followed by ceftazidime (31·69%) and meropenem (33·03). Sixteen (7·14%) isolates showed MBL production. Infection caused by drug‐resistant P. aeruginosa is important to identify as it poses a therapeutic problem and is also a serious concern for infection control management. The acquired resistance genes can be horizontally transferred to other pathogens or commensals if aseptic procedures are not followed.     

International clones of extended‐spectrum β‐lactamase (CTX‐M)‐producing Escherichia coli in peri‐urban wild animals,Brazil

CTX‐M‐type extended‐spectrum β‐lactamase (ESBL)‐producing Escherichia coli clones have been increasingly reported worldwide. In this regard, although discussions of transmission routes of these bacteria are in evidence, molecular data are lacking to elucidate the epidemiological impacts of ESBL producers in wild animals. In this study, we have screened 90 wild animals living in a surrounding area of São Paulo, the largest metropolitan city in South America, to monitor the presence of multidrug‐resistant (MDR) Gram‐negative bacteria. Using a genomic approach, we have analysed eight ceftriaxone‐resistant E. coli. Resistome analyses revealed that all E. coli strains carried bla_CTX‐M‐type genes, prevalent in human infections, besides other clinically relevant resistance genes to aminoglycosides, β‐lactams, phenicols, tetracyclines, sulphonamides, trimethoprim, fosfomycin and quinolones. Additionally, E. coli strains belonged to international sequence types (STs) ST38, ST58, ST212, ST744, ST1158 and ST1251, and carried several virulence‐associated genes. Our findings suggest spread and adaptation of international clones of CTX‐M‐producing E. coli beyond urban settings, including wildlife from shared environments.     

Transplant tourism complicated by life‐threatening New Delhi metallo‐β‐lactamase‐1 infection

Transplant tourism, which is the practice of traveling to other countries for transplant, continues to be a major problem worldwide. We describe a patient who traveled to Pakistan and underwent commercial kidney transplant. He developed life‐threatening infections from New Delhi metallo‐β‐lactamase‐1–producing Enterobacter cloacae and Rhizopus oryzae, resulting in a necrotizing kidney allograft infection and subsequent external iliac artery rupture. He survived after a prolonged course of nonstandardized antimicrobial therapy, including a combination of aztreonam and ceftazidime‐avibactam, and aggressive surgical debridement with allograft nephrectomy. The early timing of infection with these unusual organisms localized to the allograft suggests contamination and substandard care at the time of transplant. This case highlights the challenges of caring for these infections and serves as a cautionary tale for the potential complications of commercial transplant tourism.     

Wild griffon vultures (Gyps fulvus) fed at supplementary feeding stations: Potential carriers of pig pathogens and pig‐derived antimicrobial resistance?

The carriage of two important pathogens of pigs, that is enterotoxigenic Escherichia coli (ETEC) and Clostridioides difficile, was investigated in 104 cloacal samples from wild griffon vultures (Gyps fulvus) fed on pig carcasses at supplementary feeding stations (SFS), along with their level of antimicrobial resistance (AMR). E. coli was isolated from 90 (86.5%) samples, but no ETEC was detected, likely because ETEC fimbriae confer the species specificity of the pathogen. Resistance to at least one antimicrobial agent was detected in 89.9% of E. coli isolates, with AMR levels being extremely high (>70%) for tetracycline and streptomycin and very high (>50%) for ampicillin and sulfamethoxazole–trimethoprim. Resistance to other critically important antimicrobials such as colistin and extended‐spectrum cephalosporins was 2.2% and 1.1%, respectively, and was encoded by the mcr‐1 and bla_SHV‐12 genes. Multidrug resistance was displayed by 80% of the resistant E. coli, and bla_SHV‐12 gene shared plasmid with other AMR genes. In general, resistance patterns in E. coli from vultures mirrored those found in pigs. Clostridioides difficile was detected in three samples (2.9%); two of them belonged to PCR ribotype 078 and one to PCR ribotype 126, both commonly found in pigs. All C. difficile isolates were characterized by a moderate‐to‐high level of resistance to fluoroquinolones and macrolides but susceptible to metronidazole or vancomycin, similar to what is usually found in C. difficile isolates from pigs. Thus, vultures may contribute somewhat to the environmental dissemination of some pig pathogens through their acquisition from pig carcasses and, more importantly, of AMR for antibiotics of critical importance for humans. However, the role of vultures would likely be much lesser than that of disposing pig carcasses at the SFS. The monitoring of AMR, and particularly of colistin‐resistant and ESBL‐producing E. coli, should be considered in pig farms used as sources of carcasses for SFS.     

The Distribution of Escherichia coli Serovars,Virulence Genes,Gene Association and Combinations and Virulence Genes Encoding Serotypes in Pathogenic E. coli Recovered from Diarrhoeic Calves,Sheep and Goat

Ruminants, especially cattle, have been implicated as a principal reservoir of one of the enterovirulent Escherichia coli pathotypes. The detection of the virulence genes in diarrhoeic calves and small ruminants has not been studied in Egypt. To determine the occurrence, serotypes and the virulence gene markers, stx1, stx2, hylA, Flic_h7, stb, F41, K99, sta, F17, LT‐I, LT‐II and eae, rectal swabs were taken from diarrhoeic calves, sheep and goats and subjected to bacterial culture and PCR. The E. coli prevalence rate in the diarrhoeic animals was 63.6% in calves, 27.3% in goat and 9.1% in sheep. The 102 E. coli strains isolated from the calves, goat and sheep were 100% haemolytic non‐verotoxic and fitted into the Eagg group. The isolates belonged to seven O serogroups (O25, O78, O86, O119, O158, O164 and O157). The eae gene was detected in six of the strains isolated from the calves. The 102 bovine, ovine and caprine E. coli strains isolated in this study were negative for stx1, stx2, F41, LT‐I and Flic_h7 genes. The highest gene combinations were found to occur in the form of 24/102 isolates (23.5%) that carried the F17 gene predominantly associated with eaeA, hylA, K99 and Stb genes in the calves, while the hylA, K99 and Sta were the only genes found to be in conjunction in both calves and goats (6/102; 5.9% each). Our data show that in Egypt, large and small ruminants could be a potential source of infection in humans.     

The influence of physical and mental training on plasma beta‐endorphin level and pain perception after intensive physical exercise

The intention of the study was to investigate a possible correlation between increase in circulating blood level of beta‐endorphin and decrease in pain perception after short‐term intensive physical exercise. In addition, we wanted to see if plasma beta‐endorphin level and pain perception were influenced by regular physical or mental training and if there was any difference in response between trained and untrained subjects. Twenty physically trained males were studied before and after a 6‐month intervention period while practising regular physical endurance training. Eleven of them were randomized to perform daily additional mental training (ACEM meditation). Nine untrained males served as control subjects and were investigated only at baseline. All participants were tested for maximum oxygen uptake (VO_2max) during treadmill exercise, and pain perception measured by an ischaemic pain test was performed just before and after VO_2max. Blood samples analysed for beta‐endorphin were drawn before and after the tests. There was a substantial decrease of 47 per cent (p < 0.005) in basal plasma beta‐endorphin level after the intervention. The plasma beta‐endorphin level increased two‐fold (p < 0.01) in response to the VO_2max test. The subjects experienced post‐exercise hypoalgesia (p < 0.001), but there was no correlation between the exercise‐associated opioid hyperendemia and the hypoalgesia. No difference was found between trained and untrained subjects regarding the circulating blood level of beta‐endorphin or the exercise‐induced hypoalgesia. Practising regular meditation had no influence on beta‐endorphin level or pain tolerance level. Peripheral beta‐endorphin level and pain perception are modulated by intensive physical exercise and by regular physical, but not by mental training. It could be speculated that the observed initial high basal level of beta‐endorphin is due to pre‐experimental stress and tension. Copyright © 2001 John Wiley & Sons, Ltd.     

Population structure and antimicrobial resistance traits of avian‐origin mcr‐1‐positive Escherichia coli in Eastern China, 2015 to 2017

Recent emergence of mcr‐1‐positive Escherichia coli (MCRPEC) is causing serious concern around the world. Due to poultry‐origin E. coli holding zoonotic potential, the improved understandings of MCRPEC population structure and antimicrobial resistance are critical to public health purposes. This study provided novel insights into the molecular epidemiology of avian‐origin MCRPEC. For the mcr genes prevalence study, we analysed 1,360 E. coli recovered from avian colibacillosis in eastern China from 2015 to 2017. The mcr‐1 was present in 172 (12.6%) E. coli isolates. For all of MCRPEC isolates, MICs of colistin were ≥4 mg/L. Avian‐origin MCRPEC was widely distributed throughout phylogroups A, B1, B2, D, and F. Moreover, those isolates were assigned to 52 unique STs, such as ST48, ST117, ST131, and ST648, suggesting substantial horizontal dissemination of mcr‐1 gene through avian‐origin E. coli populations. The susceptibility of MCRPEC isolates was tested with 26 antimicrobial agents from 16 antimicrobial categories. There were high resistance rates of MCRPEC isolates against the clinically used antibiotics. All MCRPEC isolates in this study presented the multidrug‐resistant (MDR) trait were even considered as extensively drug‐resistant (XDR) strains. Resistance genotypes and plasmid replicon profiling showed that a majority of MCRPEC isolates contained plasmid‐mediated resistance genes and exhibited the co‐existence of mcr‐1 with ESBLs and pAmpCs genes. Furthermore, the overlapped distribution of ST types and resistance gene contents was detected among MCRPEC isolates from humans and poultry. Besides mcr‐1, our findings highlighted a significant prevalence of plasmid‐mediated resistance genes among avian‐origin MCRPEC isolates.     

Metallo Beta Lactamase Producing <Emphasis Type="Italic">Pseudomonas Aeruginosa</Emphasis> and its Association with Diabetic Foot

Pseudomonas aeruginosa strains that produce metallo beta lactamases (MBLs) are becoming increasingly prevalent in wound infections. The aim of the present study is to determine the clinical features, incidence, and to find out the antimicrobial susceptibility pattern of Pseudomonas aeruginosa in diabetic foot infections. Pus samples for bacterial culture were collected from 310 patients admitted with diabetic foot infections. Antimicrobial sensitivity testing was performed by the Kirby-Bauer disc diffusion method. Carbapenem resistance screening and confirmation of MBL was done by the modified imipenem-ethylenediaminetetraacetic acid (EDTA) double disc synergy test. A total of 54 Pseudomonas aeruginosa was isolated from 310 diabetic foot cases. Males were affected more than females with an M:F ratio of 1.6:1. Most patients belonged to the fifth decade of life with a mean age of 49 ± 16.8 years. All the patients were previously diagnosed with diabetes mellitus with duration of the disease at 16 ± 10.2 years and 63% were prescribed oral hypoglycaemic agents. Wound characteristics were classified according to Wagner’s classification majority of Pseudomonas aeruginosa were isolated from Wagner’s II and III grade wound. A number of 26 (89.7%) patients underwent debridement, while 9 (31%) patients underwent toe disarticulation, and 7 (24.1%) patients underwent below-the-knee (BKA) amputation. Antibiotic sensitivity testing revealed 20.3% of Pseudomonas aeruginosa were resistance to carbapenem and 81.8% of these were MBL mediated resistance. Infection with multi drug resistance organisms (MDROs) is common in diabetic foot ulcers and is associated with inadequate glycemic control and increased requirement for surgical treatment. There is a need for continuous surveillance of resistant bacteria to provide the basis for empirical therapy and reduce the risk of complications.     

Klebsiella pneumoniae carrying blaNDM-1 gene in orthopedic practice

Emergence and spread of carbapenemases in Enterobacteriaceae is a cause of concern worldwide, the latest threat being New Delhi metallo-β-lactamase (NDM-1). This report is of an orthopedic case with fracture femur managed with internal fixation and bone grafting, who subsequently developed secondary infection with Klebsiella pneumoniae harboring bla_NDM-1 gene. Minimum inhibitory concentration (MIC) of imipenem was ≥8 μg/ml by E-test, suggestive of carbapenemase production. Phenotypic and further genotypic detection confirmed the presence of bla_NDM-1 gene. The isolate remained susceptible only to tigecycline, colistin, and polymyxin B.     

Comparison of exendin‐4 on beta‐cell replication in mouse and human islet grafts

Exendin‐4 can stimulate β‐cell replication in mice. Whether it can stimulate β‐cell replication in human islet grafts remains unknown. Therefore, we compared the effects of exendin‐4 on β‐cell replication in mouse and human islet grafts. Islets, isolated from mouse and human donors at different ages, were transplanted into diabetic mice and/or diabetic nude mice that were given bromodeoxyuridine (BrdU) with or without exendin‐4. At 4 weeks post‐transplantation, islet grafts were removed for insulin and BrdU staining and quantification of insulin⁺/BrdU⁺ cells. Although diabetes was reversed in all mice transplanting syngeneic mouse islets from young or old donors, normoglycemia was achieved significantly faster in exendin‐4 treated mice. Mouse islet grafts in exendin‐4 treated mice had significantly more insulin⁺/BrdU⁺β cells than in untreated mice (P < 0.01). Human islet grafts from ≤22‐year‐old donors had more insulin⁺/BrdU⁺β cells in exendin‐4 treated mice than that in untreated mice (P < 0.01). However, human islet grafts from ≥35‐year‐old donors contained few insulin⁺/BrdU⁺β cells in exendin‐4 treated or untreated mice. Our data demonstrated that the capacity for β‐cell replication in mouse and human islet grafts is different with and without exendin‐4 treatment and indicated that GLP‐1 agonists can stimulate β‐cell replication in human islets from young donors.     

Associations Between Anti‐Microbial Resistance Phenotypes,Anti‐Microbial Resistance Genotypes and Virulence Genes of Escherichia coli Isolates from Pakistan and China

The objective of this study was to determine the association between phenotypic resistance, genotypic resistance and virulence genes of Escherichia coli isolates in Jiangsu province, China and Punjab province Pakistan. A total of 62 E. coli isolates were characterized for phenotypic resistance, genotypic resistance and virulence factor genes. The anti‐microbial resistance phenotype and genotypes in relation to virulence factor genes were assessed by statistical analysis. Of 20 tested virulence genes, twelve were found and eight were not found in any isolates. sitA and TspE4C2 were the most prevalent virulence genes. Of the 13 anti‐microbial agents tested, resistance to ampicillin, sulphonamide and tetracycline was the most frequent. All isolates were multiresistant, and 74% were resistant to trimethoprim and sulphamethaxazole. Phenotypically, tetracycline‐, cefotaxime‐ and trimethoprim‐resistant isolates had increased virulence factors as compared with susceptible isolates. Genotypically, resistant genes Tem, ctx‐M, Tet, Sul 1, dhfr1, Cat2 and flo‐R showed the association with the virulence genes. Almost all classes of anti‐microbial‐resistant genes have a high association with virulence. Resistant isolates have more virulent genes than the susceptible isolates.     

Prevalence of fluoroquinolone‐resistant rectal flora in patients undergoing transrectal ultrasound‐guided prostate needle biopsy: A prospective multicenter study

Objectives

To estimate the prevalence of fluoroquinolone‐resistant rectal flora in patients undergoing transrectal ultrasound‐guided prostate needle biopsy and to identify the high‐risk groups.

Methods

From January 2015 to March 2016, rectal swabs of 557 men who underwent transrectal ultrasound‐guided prostate needle biopsy were obtained from five institutions. Clinical variables, including demographics, rectal swab culture results and infectious complications, were evaluated. Univariable and multivariable analyses were used to identify the risk factors for fluoroquinolone resistance of rectal flora and infectious complications.

Results

The incidence of fluoroquinolone‐resistant and extended‐spectrum beta‐lactamase production was 48.1 and 11.8%, respectively. The most common fluoroquinolone‐resistant bacteria was Escherichia coli (81% of total fluoroquinolone‐resistant bacteria, 39% of total rectal flora), and 16 (2.9%) patients had infectious complications. Univariable and multivariable analysis of clinical parameters affecting fluoroquinolone resistance showed no factor associated with fluoroquinolone resistance of rectal flora. The clinical parameter related to infectious complications after prostate biopsy was a history of operation within 6 months (relative risk 6.60; 95% confidence interval 1.99–21.8, P = 0.002).

Conclusions

These findings suggest that a risk‐based approach by history taking cannot predict antibiotic resistance of rectal flora, and physicians should consider targeted antibiotic prophylaxis or extended antibiotic prophylaxis for Korean patients undergoing transrectal ultrasound‐guided prostate biopsy because of high antibiotic resistance of rectal flora.     

G‐Protein‐Coupled Chemokine Receptor Gene in Lumpy Skin Disease Virus Isolates from Cattle and Water Buffalo (Bubalus bubalis) in Egypt

Lumpy skin disease virus (LSDV), sheep poxvirus (SPV) and goat poxvirus (GPV) are the most serious poxviruses of ruminants. In this study, we analysed the G‐protein‐coupled chemokine receptor (GPCR) genes of LSDV isolates from cattle and water buffalo (Bubalus bubalis) in Egypt during the summer of 2011. Multiple alignments of the nucleotide sequences revealed that the water buffalo LSDV isolate differed from the cattle isolate at four nucleotide positions, and both isolates had nine nucleotide mutations from the reference strain, Egyptian tissue culture‐adapted cattle LSDV/Ismailyia88 strain. Compared with the GPCR sequences of SPV and GPV strains, a 21 nucleotide insertion and a 12 nucleotide deletion were identified in the GPCR genes of our used isolates and other LSDVs. The amino acid sequences of GPCR genes of our isolates contained the unique signature of LSDV (A₁₁, T₁₂, T₃₄, S₉₉ and P₁₉₉). Phylogenetic analyses showed that the GPCR genes of cattle and water buffalo LSDVs were closest genetically, indicating a potential transmission of cattle LSDV to water buffalo.     

Phenotypic and genotypic analyses of antimicrobial resistant bacteria in livestock in Uganda

Antimicrobial resistant bacteria (ARB) in livestock are a global public health concern, not only because they prolong infectious diseases but also they can be transferred from animals to humans via the food chain. Here, we studied ARB in livestock at commercial and subsistence farms (n = 13) in Wakiso and Mpigi districts, Uganda. We enquired from the farmers about the type and the purpose of antimicrobial agents they have used to treat their livestock. After collecting faeces, we isolated antimicrobial resistant Escherichia coli from livestock faeces (n = 134) as an indicator bacterium. These strains showed resistance to ampicillin (44.8%), tetracycline (97.0%), and sulfamethoxazole‐trimethoprim (56.7%). The frequency of ampicillin‐resistance was significantly correlated with the usage of penicillins to livestock in the farms (p = 0.04). The metagenomics data detected 911 antimicrobial resistant genes that were classified into 16 categories. Genes for multidrug efflux pumps were the most prevalent category in all except in one sample. Interestingly, the genes encoding third‐generation cephalosporins (bla_CTX‐M), carbapenems (bla_ACT), and colistin (arnA) were detected by metagenomics analysis although these phenotypes were not detected in our E. coli strains. Our results suggest that the emergence and transmission of cephalosporin, carbapenem, and/or colistin‐resistant bacteria among livestock can occur in future if these antimicrobial agents are used.     

Molecular characterization of multidrug-resistant (MDR) Pseudomonas aeruginosa isolated in a burn center

Objective

The aim of this study was to characterize molecularly multidrug-resistant (MDR) Pseudomonas aeruginosa isolates collected from burn center (BC) patients and environment in a hospital localized in Rio de Janeiro city, RJ, Brazil.

Diversity of β-lactamases produced by imipenem resistant,Pseudomonas aeruginosa isolates from the bloodstream

IntroductionThe emergence of imipenem non-susceptible Pseudomonas aeruginosa isolates is a matter of great concern because these isolates can become resistant to all available antibiotics. This study conducted to characterize β-lactamase genes in imipenem resistant P. aeruginosa isolates from bloodstream.Methods56 non-duplicate clinical isolates of P. aeruginosa were collected in Tehran hospitals. Antibacterial susceptibility was determined by disk diffusion and MIC methods. ESBL and MBL production was confirmed by combined disk. β-Lactamase classes A, B and D genes were identified by PCR.ResultsSeventeen (30.3%) isolates were imipenem resistant for which 16 isolates simultaneously were resistant to all tested antibiotics. While among 39 imipenem susceptible isolates, only two isolates were resistant to all tested antibiotics. In imipenem resistant isolates, bla_TEM, bla_SHV and bla_OXA-10 were found in 41.1% of isolates and bla_VIM, bla_IMP and bla_PER were identified in 47%, 11.7% and 5.8% of isolates respectively, while in imipenem susceptible isolates, bla_TEM, bla_SHV and bla_OXA-10 were determined in 2.5%, 7.6% and 33.3% of isolates, respectively. The imipenem resistant isolates had been recovered mostly (67.7%) from patients in the Burn hospital.ConclusionThe result of this study indicated the emergence of multidrug resistant MBL and non-MBL producing P. aeruginosa, particularly in the Burn hospital and bla_VIM was dominant β-lactamase genes in imipenem resistant isolates. The isolation of carrier patients may lead to prevent a further dissemination.     

Free‐living Waterfowl as a Source of Zoonotic Bacteria in a Dense Wild Bird Population Area in Northeastern Spain

Salmonella spp. and Campylobacter spp. are zoonotic bacteria that represent an economic and public health concern worldwide. Due to the difficulty to collect samples from free‐living waterfowl, little is known on their importance as a reservoir of zoonotic agents. Thus, a study was conducted to determine the prevalence, genotypic diversity and antimicrobial susceptibility of Salmonella and Campylobacter from waterfowl in Ebro Delta (northeastern Spain), a geographical area with a dense wild bird population. Samples were collected from 318 adult waterfowl belonging to nine fowl species. All the samples were taken during the hunting season from 2008 to 2010. None of the birds were positive for Salmonella, while the overall Campylobacter prevalence was 12.58% (40/318). A much higher Campylobacter coli prevalence than Campylobacter jejuni was found (11.64% versus 0.94%). The species Fulica atra showed the highest Campylobacter prevalence (78.05%). ERIC‐PCR of the isolates showed a high diversity of strains. Antimicrobial susceptibility testing of Campylobacter isolates showed that all the isolates were susceptible to the seven antibiotics tested.     

The antimicrobial efficacy of silver on antibiotic-resistant bacteria isolated from burn wounds

The antibiotic‐resistant bacteria are a major concern to wound care because of their ability to resist many of the antibiotics used today to treat infections. Consequently, other antimicrobials, in particular ionic silver, are considered ideal topical agents for effectively helping to manage and prevent local infections. Little is known about the antimicrobial efficacy of ionic silver on antibiotic‐resistant bacteria at different pH values. Consequently, in this study our aim was to evaluate the effect of pH on the antimicrobial efficacy of a silver alginate (SA) and a silver carboxymethyl cellulose (SCMC) dressing on antibiotic‐resistant bacteria isolated from burn patients. Forty‐nine antibiotic‐resistant bacteria, including Vancomycin‐resistant Enterococcus faecium, meticillin‐resistant Staphylococcus aureus, multidrug‐resistant (MDR) Pseudomonas aeruginosa, MDR Vibrio sp, MDR Stenotrophomonas maltophilia, extended‐spectrum ß‐lactamase (ESBL) producing Salmonella sp, ESBL producing Klebsiella pneumoniae, ESBL producing Proteus mirabilis, ESBL producing Escherichia coli and MDR Acinetobacter baumannii, routinely isolated from burn wounds were used in the study and evaluated for their susceptibility to two silver containing wound dressings using a standardised antimicrobial efficacy screening assay [corrected zone of inhibition (CZOI)]. The mean overall CZOI for the Gram‐positive isolates at a pH of 5·5 were very similar for both dressings. A mean CZOI of 5 mm was recorded for the SCMC dressing, which was slightly higher, at 5·4 mm for the SA dressing. At a pH of 7·0 both dressings, in general, showed a similar activity. However, at a pH of 8·5 the mean CZOI of the SCMC dressing was found to be significantly (P < 0·05) higher than the SA dressing for a select number of isolates. The mean overall CZOI for the Gram‐negative bacteria followed a similar pattern as observed with the Gram‐positive bacteria. Susceptibility to silver ions did vary significantly between genera and species of bacteria. Interestingly, when pH was changed from 8·5 to 5·5 antimicrobial activity for both dressings in general increased significantly (P < 0·05). Overall, all forty‐nine antibiotic‐resistant bacteria isolated from burn wounds showed susceptibility to the antimicrobial activity of both silver containing wound dressings over all pH ranges. In addition, the study showed that the performance of both dressings apparently increased when pH became more acidic. The findings in this study may help to further enhance our knowledge of the role pH plays in affecting both bacterial susceptibility and antimicrobial activity of silver containing wound dressings.