Antibiotic Susceptibility Test Results Research Articles

All-electrical antibiotic susceptibility testing within 30 min using silicon nano transistors

Rapid and reliable antibiotic susceptibility testing (AST) platform is highly desired to select the right antibiotics to treat infectious disease at early stage. Here, we demonstrate rapid ASTs using nanoscale silicon ion-selective field-effect transistor sensors. Our sensors profile bacterial metabolic kinetics by monitoring the metabolism induced acidification in the growth media with the absence and the presence of different antibiotics. Rapid AST results could be determined from the metabolic profiles with a total assay time less than 30 min for different bacterial strains. In addition, the sensors could also distinguish the bactericidal mechanisms for antibiotics with different modes of actions. Furthermore, the initial bacterial concentration in an unknown sample, a key parameter to determine its clinic relevance, could be estimated based on the metabolic profiles. Our demonstrated AST method is all-electrical, label-free and silicon technology compatible, and holds great promise for the development of a high-throughput and low-cost point-of-care device.

Genotyping of methicillin-resistant Staphylococcus aureus isolates causing invasive infections using spa typing and their correlation with antimicrobial susceptibility

Correlation of antimicrobial susceptibility patterns with particular spa types could help physicians select appropriate antibiotics for the treatment of invasive methicillin-resistant Staphylococcus aureus (MRSA) infections. The aim of this study was to investigate invasive MRSA isolates through delineating the molecular typing results and correlating them with antibiotic susceptibility testing results. A total of 670 non-duplicate mecA-positive MRSA isolates from patients with invasive infections were collected from a 5-year nationwide antimicrobial surveillance programme [Tigecycline In vitro Surveillance in Taiwan (TIST)] and 58 spa types were identified among 639 isolates (95.4%) by determining the allelic profile of the spa gene using PCR and nucleotide sequencing. Six major spa types, including spa t002 (n=103; 15.4%) and t037 (n=253, 37.8%), were classified as healthcare-associated MRSA (HA-MRSA; 53.1%), while t437 (n=151; 22.5%), t441 (n=13; 1.9%), t1081 (n=19; 2.8%) and t3525 (n=14; 2.1%) were classified as community-associated MRSA (CA-MRSA; 29.4%). Antimicrobial susceptibility was determined by agar dilution or broth microdilution for various antibiotics, and Etest was also used both for daptomycin and vancomycin. The declining trend in vancomycin minimum inhibitory concentration (MIC) was in parallel with an increasing frequency of CA-MRSA. Antibiotic susceptibility patterns were correlated with particular spa types and this correlation could help physicians select appropriate antibiotics for the treatment of invasive MRSA infections.

Fast antibiotic susceptibility testing of urine microflora using a microbiological analyzer based on coherent fluctuation nephelometry.

Traditional culture-based microbiological methods remain the most used for defining the etiology of urinary tract infections and antibiotic susceptibility testing (AST) of isolated uropathogens. They are time-consuming and lead to delays of several days when obtaining the final results of microbiological tests. In this study, we validate the possibility of using a microbiological CFN analyzer combined with MALDI-TOF mass spectrometry (MS) for fast conclusive urine testing (1day) without obtaining pure cultures. The study included three stages: detection of urine microflora growth using the CFN analyzer to separate positive and negative samples within 2-4h; fast MS identification of positive samples without isolating uropathogens; fast AST using CFN analyzer within 3-6h. In parallel, all urine samples were tested by traditional culture-based microbiological methods. In total, 194 urine samples were tested, and 22 urine cultures were identified by MS, among them, 20 monocultures with bacterial counts ≥ 105 and 2 mixed cultures. The AST of these 22 urine cultures and additional 88 pure clinical cultures was performed using eight antibiotics. Overall, 276 tests were performed. The results of AST obtained using the CFN analyzer and traditional methods were in good agreement (98.2%). Although two mixed cultures were falsely identified as monocultures, their susceptibility determined by the CFN analyzer was correct. The CFN analyzer is promising and effective for fast AST. Combined with MS identification, it allows to perform full urine analysis in 1day without the lengthy isolation of pure cultures.

Prevalence of Diarrheagenic Bacteria in Stool Samples of Adult Patients Attending Dutsin-Ma General Hospital, Katsina State, Northwestern Nigeria

Enteric infections and diarrheal diseases (EIDD) pose serious threats to human health globally, closely associated with poor environmental sanitation, poor water supply and unhygienic nature of individuals, which are common in developing countries. Viruses and Parasites are the major microbial agents known to cause Diarrhea and Bacteria especially Escherichia coli, Salmonella Spp. and Shigella Spp. This study was carried out to investigate the prevalence of Escherichia coli and Salmonella species among adults attending Dutsin-Ma General Hospital, Katsina State, and to determine the antimicrobial susceptibility profile of the bacterial isolates to commonly prescribed antibiotics against them. A total of 30 fresh diarrheic samples were collected from the study participants, 17 samples from male and 13 from female participants in sterile sample containers between May and July, 2021. The samples were put in ice packed container and then transported to the laboratory of the Microbiology Department, Federal University, Dutsin-Ma for processing and analyses. Out of the 30 samples examined, 29 (96.67%) were found to be positive, 16(53.33%) E. coli and 13(43.33%) Salmonella species, respectively. The result of antibiotic susceptibility test showed that both E. coli and Salmonella species had highest resistance to ampicillin but were found to be sensitive to chloramphenicol, hence, it could be used as a best drug of choice for the treatment of diarrhoea caused by the pathogens.

Withdrawal: “Evaluation of microbial agents and their antibiotic susceptibility profiles in patients with chronic suppurative otitis media” Ali Ozturk, İsmail Cetintas, Mehmet Bayraktar, İsmail İynen

This article was published whilst it was still in peer review due to a technical error at the publisher and has been temporarily removed.

Enigma of Respiratory Carriage of Kingella kingae and Neisseria meningitides in Young Jordanian Children

Background: 
 Kingella kingae and Neisseria meningitides are gram-negative bacteria, causing several life-threatening diseases and considered as opportunistic pathogens in the upper respiratory tract of healthy carriers. The detection of these both bacteria species is difficult in routine culture methods.
 Objective:
 This study aimed to find the occurrence rate of K. kingae and N. meningitides colonizing upper respiratory tract of young Jordanian children, and to determine the antimicrobial susceptibility profile of the isolates.
 Methods: 
 A total of 300 samples of throat and nasal swabs were collected from out- patients Jordanian children aged between 6 months and 5 years, who were admitted to Pediatrics' clinics department at the Jordan University Hospital and Al-Bashir Hospital over the period October 2018 through January 2019. Samples were cultured for detection K. kingae and Neisseria species including specially N. meningitides. Their suspected growth was identified and tested using microbiology culture methods and polymerase chain reaction (PCR) method. Additionally, DNA was extracted directly from one 100 samples and was investigated only for K. kingae using real- time PCR assay. 
 Results: 
 This study showed the absence of K. kingae in all cultured samples, while Neisseriaspecies was detected in 21 (7 %)including one N. meningitides isolate(0.3%). The results of antibiotic susceptibility testing indicated presence of few percentage of Neisseria species isolates resistant 100 % to clindamycin, oxacillin and vancomycin, whereas all were susceptible for chloramphenicol (100%)levofloxacin and gentamycin , and less to ampicillin(90.6%) and erytromycin ( 85.7%), respectively.
 Conclusion: This study shows the absence of K. kingae and the rare occurrence of N. meningitides colonizing the upper respiratory tract of young Jordanian children over the 4-month period of study.

Phenotypic Detection of Hemin-Inducible Trimethoprim-Sulfamethoxazole Heteroresistance in Staphylococcus aureus.

ABSTRACTTrimethoprim-sulfamethoxazole (SXT) is a valuable second-line antimicrobial agent to treat methicillin-resistant Staphylococcus aureus infections. Discrepancies between various antibiotic susceptibility testing (AST) methods for SXT susceptibility in S. aureus have been described. Here, we describe a hemin-inducible heteroresistance phenotype in S. aureus. We compared the results of the Vitek 2 AST on a set of 95 S. aureus clinical isolates with broth microdilution, disk diffusion using standard Mueller-Hinton agar, and disk diffusion using Mueller-Hinton agar supplemented with 5% horse blood (MHF). To investigate the potential clinical relevance of SXT heteroresistance, an in vivo Galleria mellonella infection assay was performed. All Vitek 2 SXT-susceptible (n = 17) isolates were concordant with AST results by other methods applied in this study. In 32/78 (41%) of Vitek 2 SXT-resistant isolates, we observed a heteroresistant growth phenotype on MHF. The heteroresistance phenotype was associated with the presence of dfr genes, encoding trimethoprim resistance. The addition of a hemin-impregnated disk in a double disk diffusion method on standard Mueller-Hinton agar was able to induce growth in the SXT zone of inhibition. An in vivo infection assay with G. mellonella suggested that the SXT heteroresistance phenotype resulted in lethality similar to that of the SXT-resistant phenotype. In this study, we describe a novel hemin-inducible heteroresistance phenotype in S. aureus. This heteroresistance phenotype may be missed by standard AST methods but can be detected by performing disk diffusion using Mueller-Hinton agar supplemented with 5% horse blood, commonly used for AST of fastidious organisms. This phenomenon may partly explain the discrepancies of AST methods in determining SXT resistance in S. aureus.IMPORTANCE Staphylococcus aureus is one of most important pathogens in clinical medicine. Besides its virulence, the acquisition or emergence of resistance toward antibiotic agents, in particular to beta-lactam antibiotics (methicillin-resistant S. aureus [MRSA]), poses a major therapeutic challenge. Trimethoprim-sulfamethoxazole (SXT) is one of the effective antimicrobial agents of last resort to treat MRSA infections. Here, we report the detection of a SXT-heteroresistant phenotype which is inducible by hemin and can be detected using Mueller-Hinton agar supplemented with horse blood. Heteroresistance describes the presence or emergence of resistant subpopulations, which may potentially lead to inaccurate antibiotic susceptibility testing results and influence the success of antibiotic therapy.

Wide spread and diversity of mutation in the gyrA gene of quinolone-resistant Corynebacterium striatum strains isolated from three tertiary hospitals in China

BackgroundCorynebacterium striatum was confirmed to be an important opportunistic pathogen, which could lead to multiple-site infections and presented high prevalence of multidrug resistance, particularly to quinolone antibiotics. This study aimed to investigate the mechanism underlying resistance to quinolones and the epidemiological features of 410 quinolone-resistant C. striatum clinical strains isolated from three tertiary hospitals in China.MethodsA total of 410 C. striatum clinical strains were isolated from different clinical samples of patients admitted to three tertiary teaching hospitals in China. Antibiotic susceptibility testing was performed using the microdilution broth method and pulsed-field gel electrophoresis (PFGE) was used for genotyping. Gene sequencing was used to identify possible mutations in the quinolone resistance-determining regions (QRDRs) of gyrA.ResultsIn total, 410 C. striatum isolates were sensitive to vancomycin, linezolid, and daptomycin but resistant to ciprofloxacin. Depending on the antibiotic susceptibility testing results of 12 antimicrobial agents, the 410 C. striatum strains were classified into 12 resistant biotypes; of these, the three biotypes R1, R2, and R3 were dominant and accounted for 47.3% (194/410), 21.0% (86/410), and 23.2% (95/410) of the resistant biotypes, respectively. Mutations in the QRDRs ofgyrA were detected in all quinolone-resistant C. striatum isolates, and 97.3% of the isolates (399/410) showed double mutations in codons 87 and 91 of the QRDRs of gyrA. Ser-87 to Phe-87 and Asp-91 to Ala-91 double mutation in C. striatum was the most prevalent and accounted for 72.2% (296/410) of all mutations. Four new mutations in gyrA were identified in this study; these included Ser-87 to Tyr-87 and Asp-91 to Ala-91 (double mutation, 101 isolates); Ser-87 to Val-87 and Asp-91 toGly-91 (double mutation, one isolate); Ser-87 to Val-87 and Asp-91 to Ala-91 (double mutation, one isolate); and Ser-87 to Ile-87 (single mutation, one isolate). The minimum inhibitory concentration of ciprofloxacin for isolates with double (96.5%; 385/399) and single (72.7%; 8/11) mutations was high (≥ 32 µg/mL). Based on the PFGE typing results, 101 randomly selected C. striatum strains were classified into 50 genotypes (T01-T50), including the three multidrug-resistant epidemic clones T02, T06, and T28; these accounted for 14.9% (15/101), 5.9% (6/101), and 11.9% (12/101) of all genotypes, respectively. The multidrug-resistant T02 clone was identified in hospitals A and C and persisted from 2016 to 2018. Three outbreaks resulting from the T02, T06, and T28 clones were observed among intensive care unit (ICU) patients in hospital C between April and May 2019.ConclusionsQuinolone-resistant C. striatum isolates showed a high prevalence of multidrug resistance. Point mutations in the QRDRs of gyrA conferred quinolone resistance to C. striatum, and several mutations in gyrA were newly found in this study. The great clonal diversity, high-level quinolone resistance and increased prevalence among patients susceptible to C. striatum isolates deserve more attention in the future. Moreover, more thorough investigation of the relationship between quinolone exposure and resistance evolution in C. striatum is necessary.

Epidemiology and antibiotic susceptibility in anaerobic bacteraemia: a 15-year retrospective study in South-Eastern Hungary

Introduction Bloodstream infections are considered as important factors of morbidity and represent a remarkable number of death, especially in developed countries. Methods In a 15-year retrospective study in the South-Eastern region of Hungary, the microbiological results of anaerobic blood culture (BC) bottles were analysed. The incubation of BCs was performed in the automated incubation system, and the isolates were cultured in an anaerobic chamber. The identification of the isolates was based on their biochemical profile (2004–2012) and mass spectrometry analyses (2013–2018). Antibiotic susceptibility testing was performed with minimal inhibitory concentration gradient diffusion method. Results The majority of the samples were submitted by the Department of Internal Medicine (37.7%), Intensive Care Unit (31.6%) and the Emergency Department (16.4%), and the number of strict anaerobic isolates per year showed an increasing tendency throughout the study. More than half of the isolates were Cutibacterium acnes (54.4%), but this bacterium was considered as a contaminant. The most frequent species upon Cutibacterium acnes were Bacteroides fragilis (9.2%), Clostridium perfringens (6.4%), other Clostridium species (4.8%), other Cutibacterium species (3.5%) and other Bacteroides species (2.5%). Penicillin, amoxicillin/clavulanic acid, imipenem, clindamycin, metronidazole and tigecyclin were very effective against Bacteroides fragilis, Clostridium perfringens, Fusobacterium nucleatum, Gemella morbillorum, Parvimonas micra and Eggerthella lenta strains. Conclusion We performed a 15-year period, retrospective investigation in South-Eastern Hungary with the participation of more than 1000 patients. The results of antibiotic susceptibility tests are in line with previous reports in the literature, and the results from the different geographical regions of the world suggest similar resistance mechanisms.

BactoSpin: Novel Technology for Rapid Bacteria Detection and Antibiotic Susceptibility Testing.

Inappropriate use of antibiotics is one of the leading causes of the increasing numbers of resistant bacteria strains, resulting in 700,000 deaths worldwide each year. Reducing unnecessary use of antibiotics and choosing the most effective antibiotics instead of broad-spectrum drugs will slow the arms race between germs and humans. Urinary tract infections (UTIs) are among the most common bacterial infections. Currently, accurate diagnosis of UTI requires approximately 48 h from the time of urine sample collection until antibiotic susceptibility test (AST) results. This work presents a rapid bacterial detection device that integrates a centrifuge, microscope, and incubator. Two disposable microfluidic chips were developed. The first chip was designed for bacteria concentration, detection, and medium exchange. A second multi-channel chip was developed for AST. This chip contains superhydrophobic and hydrophilic coatings to ensure liquid separation between the channels without the need for valves. The designed chips supported the detection of E. coli at a concentration as low as 5 × 103 cells/mL within 5 min and AST in under 2 h. AST was also successfully performed with Klebsiella pneumonia isolated from a human urine sample. In addition, machine-learning-based image recognition was shown to reduce the required time for AST and to provide results within 1 h for E. coli cells. Thus, the BactoSpin device can serve as an efficient and rapid platform for UTI diagnostics and AST.

Occurrence of Multiple, Extensive and Pan Drug-Resistant Pseudomonas aeruginosa and Carbapenemase Production from Presumptive Isolates Stored in a Biobank at Ethiopian Public Health Institute.

PurposePseudomonas aeruginosa is a common cause of nosocomial infections with associated morbidity and mortality because the organism is unresponsive to commonly available antimicrobials. This study was undertaken to determine the multiple drug-resistant (MDR), extensive drug-resistant (XDR) and pan drug-resistant (PDR) phenotype of P. aeruginosa and its carbapenemase production rate from presumptive isolates stored in the biobank at the Ethiopian Public Health Institute (EPHI).MethodsA cross-sectional study was conducted at the EPHI laboratory, Addis Ababa, Ethiopia from March to June 2021. Stored isolates of Pseudomonas spp. which had been characterized by manual identification methods were further processed for species-level identification (ID) and antimicrobial susceptibility testing (AST) using a Becton Dickinson (BD) Phoenix automated system. The isolates were analyzed for carbapenemase enzyme production using the modified Carbapenem Inactivation Method (mCIM). The data analysis was done using SPSS version 20 software.ResultsIn this study, 110 presumptive Pseudomonas isolates from a biobank were re-analyzed, 100 of them were found to be Pseudomonas and among these P. aeruginosa accounted for 98% and P. putida accounted for 2%. The majority of isolates were recovered from wound (46%) specimens followed by ear swabs (18%). The highest level of resistance was observed against ceftazidime (35%) and the lowest level of resistance was observed against amikacin (2%). Twenty-seven isolates were identified as candidates for carbapenemase enzyme production testing, of which only 3/27 (11%) isolates were detected as carbapenemase enzyme producers.ConclusionThis study shows an increasing rate of MDR and XDR isolates and the appearance of PDR in P. aeruginosa strains; this is a serious problem in Ethiopia. The lack of newer anti-pseudomonal antibiotics adds to the problem. In order to alleviate this, infection prevention activities should be promoted, and treatment of bacterial infections should be guided by antibiotic susceptibility test results.

Results of urinary bacterial cultures and antibiotic susceptibility testing of dogs and cats in the UK.

ObjectivesBacterial urinary tract infections are a common diagnosis in small animal practice and antibiotics are often administered empirically. The aim of this study was to investigate the aetiology and antibiotic resistance of uropathogens in dogs and cats in the UK.Materials and MethodsRetrospective study of uroculture and antibiotic susceptibility testing results (n=808) by disk diffusion processed at a veterinary pathology laboratory between 2011 and 2012.ResultsSignificant bacteriuria was detected in 18.4% of samples from dogs and 10.0% from cats, most of which (>90%) yielded a single organism. Escherichia coli was the most prevalent bacterial species (54.7% and 55.6% of feline and canine isolates, respectively) followed by Proteus mirabilis in dog samples (22.7%) and Enterococcus spp. in cat samples (23.2%). Approximately a third of E. coli isolates were resistant to ampicillin but resistance was much lower among Enterococcus spp. and P. mirabilis. Resistance to amoxicillin‐clavulanic acid also seemed to be emerging, particularly in E. coli (almost 20% resistant). In contrast, resistance to trimethoprim‐sulfamethoxazole for uropathogens remained <13% except for P. mirabilis (19.4%). Overall, fluoroquinolones showed the best in vitro activity (resistance mostly below 10% for enrofloxacin and marbofloxacin).Clinical SignificanceOur results provide evidence of the emergence of resistance to antibiotics commonly used to treat bacterial urinary tract infections. Continued monitoring of the patterns of antibiotic resistance in uropathogens is needed to assess the adequacy of recommendations on the empiric therapy of these infections.

A live attenuated strain of HY9901ΔvscB provides protection against Vibrio alginolyticus in pearl gentian grouper (♀Epinephelus fuscoguttatus × ♂Epinephelus lanceolatu)

Vibrio alginolyticus, a bacterial pathogen in fish and humans, expresses a type III secretion system (T3SS) that is critical for pathogen virulence and disease development. In this study, the T3SS chaperone protein gene vscB was cloned from V. alginolyticus wild-type strain HY9901and the vscB gene has a length of 429 bp and encodes 142 amino acids. The amino acid sequence homology comparison results showed that VscB had the highest similarity with that of Vibrio parahaemolyticus VscB, reaching 91%. The mutant strain HY9901ΔvscB was constructed by the in-frame deletion method. The HY9901ΔvscB showed an attenuated swarming phenotype and a 23-fold decrease in virulence to pearl gentian grouper (♀Epinephelus fuscoguttatus × ♂Epinephelus lanceolatu). However, the HY9901ΔvscB showed no difference in morphology, growth, biofilm formation and extracellular protease (ECPase) activity. The results of antibiotic susceptibility testing showed that the wild-type HY9901 is more sensitive to Doxycycline, Minocyline and Kanamycin than in the HY9901ΔvscB. A total of 95 differentially expressed genes were screened by transcriptome sequencing analysis of HY9901 and strain ΔvscB, revealing 57 genes up-regulated and 38 genes were down-regulated in the ΔvscB compared to HY9901. qRT-PCR was employed to analyze the transcription levels of T3SS-related genes showing that ΔvscB had decreased expression of vopN and vscO and increased expression of hop, vscN, vscK, vscL and vopS compared to HY9901. Finally, grouper vaccinated via intraperitoneal (IP) injection with HY9901ΔvscB had a relative percent survival (RPS) of 77.6% following challenge with HY9901. Real-time qPCR assays showed that vaccination with HY9901ΔvscB enhanced the expression of immune-related genes, including MHC-I, IgM, and CD8α both in the liver and spleen, indicating that HY9901ΔvscB is able to induce humoral and cell-mediated immune responses in pearl gentian grouper. These results demonstrate that the HY9901ΔvscB mutant could be used as an effective live attenuated vaccine to combat V. alginolyticus infection in pearl gentian grouper.

Pneumonia caused by Pseudomonas fluorescens: a case report

BackgroundPseudomonas fluorescens (P. fluorescens) has been detected in respiratory samples from patients. However, no previous reports have been published about these P. fluorescens cultures from lung tissues.Case presentationHere, we report a case of pneumonia caused by P. fluorescens. P. fluorescens was identified from lung biopsy specimens for the first time in this case. According to the antibiotic susceptibility testing (AST) of P. fluorescens, the patient was given ciprofloxacin treatment. The temperature of the patient then returned to normal. Chest CT examination revealed improvements in pulmonary inflammation.ConclusionsThese findings suggest that the patients with pneumonia caused by P. fluorescens should be treated in a timely manner according to the AST results.

Antibiotic Susceptibility and Biofilm Formation of Bacterial Isolates Derived from Pediatric Patients with Cystic Fibrosis from Tehran, Iran.

Cystic fibrosis (CF) is a genetic disease with a high rate of morbidity and mortality. Children with CF commonly suffer from recurrent and persistent pulmonary tract infections caused by diverse bacterial pathogens. This study aimed to investigate the prevalence, antimicrobial susceptibility, and biofilm formation of bacterial isolates in pediatric patients with CF. The study population of this cross-sectional study included 8,908 children suspected to have CF by clinical manifestations from March 2015 to August 2017 who were referred to the Tehran Pediatric Central Hospital, Iran. The tests carried out for each participant included screening sweat test, sputum culture, antibiotic susceptibility test using Kirby-Bauer disk diffusion method, and biofilm formation in microtiter plates method. Based onclinical examination and screening sweat test, 183 (2.05 %( out of 8,908 children, were positive for CF. The mean age of children was estimated at 2.93 years, and the majority of them were male (n=103, 56.2%). No gender-specific difference was observed in CF disease in this study (P&amp;gt;0.05). In addition, the results of sputum culture showed that 153 (83.6%) microorganisms (bacteria and fungi) were collected from CF patients. Normal flora was isolated in 30 (16.4%) patients and more than one bacterial species were isolated in 7.2% of patients. The obtained results indicated that Pseudomonas aeruginosa was the most prevalent isolated bacteria followed by Staphylococcus aureus, and Klebsiella pneumoniae. Based on the antibiotic susceptibility test results, P. aeruginosa and piperacillin/tazobactam had the highest (11.7%) and the lowest (2.3%) resistance rate against gentamicin, respectively. However, all K. pneumoniae isolates were resistant to Cefotaxime. Among S. aureus isolates, 83.4% and 16.6% were methicillin-susceptible Staphylococcus aureus and Methicillin-resistant Staphylococcus aureus respectively. Concerning biofilm formation, 76%, 67%, and 72.5% of P. aeruginosa, S. aureus, and K. pneumoniae isolates were biofilm producers, respectively. Based on the study results, P. aeruginosa was the dominant pathogen in pediatric patients with CF from Tehran, Iran, and most of the pathogens were biofilm producers. No severe antibiotic resistance was observed in the isolates; however, the anti-microbial resistance profile should be carefully checked in CF patients on a regular basis.

A Study on the Prevalence and Source of Staphylococci and Methicillin-resistant Staphylococcus aureus Causing Superficial Incisional Surgical Site Infection

Staphylococcus aureus and coagulase-negative staphylococci (CoNS) are common causatives of superficial incisional surgical site infection (SSI). The source of the pathogens is still not fully diagnosed whether it is endogenous or exogenous particularly with regard to the extent of its resistance to antibiotics. Therefore, this study is designed to determine the rate of infection, the source of pathogens, and the extent of their resistance to antibiotics. For this purpose, pre-, intra- and post-operative swabs from the nasal and skin of patients undergoing surgeries and samples from the hospital environment have been collected and processed for isolation and identification of staphylococci. Bacterial analysis and antibiotic susceptibility profiles of the isolates are assessed by unweighted pair group method with arithmetic mean (UPGMA) analysis based on random amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR) and disc diffusion test for antibiotics susceptibility profile. The microbiological and PCR results indicate that SSIs are found in 113/512 (22.07%), Staphylococcus spp. rated 67/512 (13.09%) of infections. Further analysis indicates that S. aureus, CoNS, and both of them were causes SSI with different rates 41/67 (61.2%), 23/67 (34.3%), and 3/67 (4.5%), respectively. Results of RAPD-PCR for 70 isolates reveal that 52/70 (74.28%) of SSIs are from endogenous source, followed by 10/70 (14.29%) and 8/70 (11.43%) from hospitals acquired and undetermined sources, respectively. Moreover, results of antibiotic susceptibility test reveal that 24/44 (54.5%) of isolates belong to methicillin-resistant Staphylococcus aureus; from both endogenous and exogenous sources with 13/24 (54.17%) and 11/24 (45.83%), respectively.

Evaluation of the performance of rapid antibiotic susceptibility test results using the disk diffusion directly from the positive blood culture bottles

PurposeIn this study, we aimed to evaluate the compliance of rapid antibiotic susceptibility test (RAST) and conventional laboratory procedures. MethodsThe RAST was performed directly from the blood cultures of 71 Gram negative bacilli (GNB) and 38 Gram positive cocci (GPC) isolates. The results were evaluated at fourth, sixth and eighth hour. Categorical agreement (CA), very major error (VME), major error (ME) and minor error (mE) were calculated and compared with the results of conventional Vitek-2 system. ResultsCategorical agreement was detected ≥90 in cefotaxime and meropenem at fourth hour in Escherichia coli isolates. An encourage positive CA results were obtained from meropenem, ceftazidime and ciprofloxacin at the fourth hour in Klebsiella pneumoniae isolates. CA was compatible in imipenem, ciprofloxacin, gentamicin, and tobramycin for Pseudomonas aeruginosa at sixth hour. CA was low (<90%) in piperacillin-tazobactam for E. coli and K. pneumoniae, and meropenem in P. aeruginosa isolates. A good CA (≥90) with all tested antibiotics were found at all hours for Acinetobacter baumannii and also very high CA (100%) was detected at sixth and eighth hour in Staphylococcus aureus isolates. CA remained below the standard criteria at fourth hour in vancomycin and high level gentamicin, in addition to imipenem at sixth hours in enterococci isolates. VME and ME were not detected and mE was 12.7% in GNB and 50% in GPC at eighth hour. ConclusionsEUCAST RAST at eighth hour will be beneficial in urgent patients due to their high CA rate, easy preparation, inexpensive, and could be performed with the available equipment and personnel.

Effect of blue laser on viability of Proteus mirabilis

The usage of blue laser has been considered as a therapeutic approach to prohibit the viability of bacterial species, but there is no agreement about optimum parameters to be used. The aim of this project is to study the influence of blue laser (450 nm) on the viability of the gram-negative bacteria Proteus mirabilis isolated from burn wounds, using different exposure times (i.e. doses) in vitro. Seventy swab samples were collected from burn wounds of patients admitted to the burns unit in AL-Yarmouk teaching hospital in Baghdad, during the period from June to August 2019. The Bacteria were isolated and identified depending on their culture characteristics, biochemical tests, gram staining, and morphology, being finally confirmed by API 20E Test System. By using the disk diffusion method, susceptibility of the isolates to 12 different antibiotics was examined. One isolate of P. mirabilis was elected according to susceptibility to all antibiotics used. To prepare bacterial solution, P. mirabilis was mixed with normal saline solution. Dilution of 10-6 cell/ml for p. mirabilis was selected from other serial dilutions. A number of colonies and colony forming units (CFUs/ml) were achieved and correlated to controls. P. mirabilis was irradiated by blue diode laser (450 nm, 500mw) and exposed to different doses (24, 48, 72, 96, 120J/cm2) corresponding to respective exposure times (4, 8,12,16,20 minutes). The results of antibiotic susceptibility test indicate that the entire isolates of P. mirabilis were multidrug resistant. With the increase in laser dose (exposure times), the number of colonies and CFUs/ml were reduced, reaching a highest inhibition in CFU/ml at exposure time of 20 minutes, i.e. a dose of 120J/cm2 , with irradiance of 0.1 watt/ cm2. No significant reduction was recorded in CFU/ml at exposure time of 4 min (a dose of 24J/cm2). As a conclusion, the blue laser irradiation at wavelength of 450 nm and 500mw had antibacterial effects on P. mirabilis isolated from burn wounds with irradiance of 0.1watt/cm2 in vitro, as evidenced by the effective reduction in the viability of bacteria at a dose of 120J/cm2 corresponding to exposure time of 20 minutes.

Desirability of Outcome Ranking for the Management of Antimicrobial Therapy (DOOR MAT) Reveals Improvements in the Treatment of Bloodstream Infections Caused by Escherichia coli and Klebsiella pneumoniae in Patients from the Veterans Health Administration.

Reductions in the use of broad-spectrum antibiotics is a cornerstone of antimicrobial stewardship. We aim to demonstrate use of the Desirability of Outcome Ranking Approach for the Management of Antimicrobial Therapy (DOOR MAT) to evaluate the treatment of Escherichia coli and Klebsiella pneumoniae bloodstream infections in patients from the Veterans Health Administration (VHA) across a decade. Using electronic records, we determined empiric and definitive antibiotic treatments, clinical characteristics, and 30-day mortality of patients with monomicrobial E. coli and K. pneumoniae bloodstream infections hospitalized in VHA medical centers from 2009 to 2018. Focusing on patients treated with parenteral β-lactams and with available antibiotic susceptibility testing results, we applied a range of DOOR MAT scores that reflect the desirability of antibiotic choices according to spectrum and activity against individual isolates. We report trends in resistance and desirability of empiric and definitive antibiotic treatments. During the 10-year period analyzed, resistance to expanded-spectrum cephalosporins and fluoroquinolones increased in E. coli but not in K. pneumoniae, while resistance to carbapenems and piperacillin-tazobactam remained unchanged. In 6451 cases analyzed, we observed improvements in DOOR MAT scores consistent with deescalation. Improvement in desirability of definitive treatment compared with empiric treatment occurred in 26% of cases, increasing from 16% in 2009 to 34% in 2018. Reductions in overtreatment were sustained and without negative impact on survival. DOOR MAT provides a framework to assess antibiotic treatment of E. coli and K. pneumoniae bloodstream infections and can be a useful metric in antimicrobial stewardship.

High Prevalence of Methicillin-Resistant Staphylococcus aureus among Healthcare Facilities and Its Related Factors in Myanmar (2018-2019).

Background: Antimicrobial resistance (AMR) is a growing global health problem. Staphylococcus aureus (SA) is a common bacterium associated with a variety of community and hospital infections. Methicillin-resistant Staphylococcus aureus (MRSA) accounts for most SA related morbidity and mortality. In this study, we determined the prevalence and factors associated with SA and MRSA in Myanmar. Methods: We collected the data retrospectively by reviewing an electronic register containing the results of bacterial culture and antibiotic susceptibility testing of biological specimens received from healthcare facilities during 2018–2019. Results: Of the 37,798 biological specimens with bacterial culture growth, 22% (8244) were Gram-positive. Among the Gram-positive bacteria, 42% (2801) were SA, of which 48% (1331) were judged as MRSA by phenotypic methods. The prevalence of MRSA was higher in the older age groups, in female patients, in urine specimens and specimens received from the intensive care unit and dermatology departments. One site (Site F) had the highest MRSA prevalence of the seven AMR sentinel sites. Most SA isolates were sensitive to vancomycin (90%) by phenotypic methods. Conclusions: The high prevalence of MRSA indicates a major public health threat. There is an urgent need to strengthen the AMR surveillance and hospital infection control program in Myanmar.