Antibiotic Susceptibility of Staphylococcus Aureus with VanA and MecA Genes.

BACKGROUND: Staphylococcus aureus (S.aureus) is an emerging antibiotic resistant bacterium responsible for various infections in human. Resistance to methicillin and vancomycin are of prime concern in S. aureus. The study aims to determine the minimum inhibitory concentration (MIC) of Vancomycin and evaluate the existence of mecA and vanA genes, associated with antibiotic resistance. METHODS: Clinical specimens from three Kathmandu hospitals were processed and S. aureus was identified using conventional microbiological procedures. MRSA was phenotypically identified with cefoxitin (30µg) disc diffusion, while vancomycin susceptibility was assessed using the Ezy MICTM stripes. The mecA and vanA genes were detected by polymerase chain reaction (PCR). RESULTS: Out of 266 S. aureus samples from various clinical specimen subjected for analysis, 77 (28.9%) were found methicillin-resistant (MRSA) and 10 (3.8%) were observed vancomycin-resistant (VRSA). Vancomycin resistant isolates showed a significant correlation between resistance to ampicillin, chloramphenicol, and cefoxitin. The mecA gene was found in 39 of the MRSA isolates, having 50.64% of MRSA cases, while the vanA gene was detected in 4 of the VRSA cases, constituting 40% of VRSA occurrences. CONCLUSIONS: The strains with higher vancomycin minimum inhibitory concentration values (≥ 1.5 µg/ml) displayed increased resistance rates to various antibiotics compared to strains with lower minimum inhibitory concentration values (< 1.5 µg/ml). The presence of vanA genes was strongly associated (100%) with vancomycin resistance, while the 10.3% mecA gene was identified from MRSA having resistance towards vancomycin also.

Characterization of polymerized impurities in cefoxitin sodium for injection by two-dimensional chromatography coupled with time-of-flight mass spectrometry.

Polymerized impurities in ß-lactam antibiotics can induce allergic reactions, which seriously threaten the health of patients. In order to study the polymerized impurities in cefoxitin sodium for injection, a novel approach based on the use of two-dimensional liquid chromatography coupled with time-of-flight mass spectrometry (2D-LC-TOF MS) was applied. In the 1st dimension, high performance size exclusion chromatography (HPSEC) with a TSK-G2000SWxl column was employed. Column switching was applied for the desalination of the mobile phase used to separate polymerized impurities in the 1st dimension before they were transferred to the 2nd dimension which utilized reversed phase liquid chromatography (RP-LC) and TOF MS for further structural characterization. The structures of four polymerized impurities (which were all previously unknown) in cefoxitin sodium for injection were deduced based on the MS2 data. One novel polymerized impurity (PI-I), with 2H less than the molecular weight of two molecules of cefoxitin (Mr. 852.09), was found to be the most abundant (>50 %) in almost all the samples examined and could be regarded as the marker polymer of cefoxitin sodium for injection. This work also showed the great potential of the 2D-LC-TOF MS approach in structural characterization of unknown impurities separated with a mobile phase containing non-volatile phosphate in the 1st dimension.

GlnR activated transcription of nitrogen metabolic pathway genes facilitates biofilm formation by mycobacterium abscessus.

OBJECTIVES: Nitrogen is indispensable for the synthesis of biomacromolecules. The correlation between nitrogen metabolism and Mycobacterium abscessus (M. abscessus) biofilm formation is unclear. This study constructed global nitrogen regulator gene GlnR (Mab_0744) knockout (ΔglnR) and complementation (ΔglnR::glnR) M. abscessus strains. METHODS: Global nitrogen regulator gene glnR (Mab_0744) knockout (ΔglnR) and complementation (ΔglnR::glnR) M. abscessus strains were constructed. Sauton's medium was used to culture M. abscessus pellicle biofilm. To test the antibiotic susceptibility of pellicle biofilm, clarithromycin, amikacin, cefoxitin or imipenem was added to the medium under biofilms after 14 days of incubation. RT-qPCR and ChIP-qPCR were performed to analyse the transcriptional regulatory function of GlnR. RESULTS: GlnR knockout decreased the growth rate of planktonic cells, reduced biofilm mass and wrinkle formation, and diminished the resistance of biofilms to antibiotics. However, the susceptibility of planktonic cells to antibiotics was not changed by glnR knockout. The growth rate of planktonic ΔglnR cells was accelerated by adding nitrogen sources to the medium; the addition of glutamine or sodium glutamate rescued ΔglnR biofilm morphology and resistance to amikacin, cefoxitin, clarithromycin and imipenem. GlnR bound the promoter region and activated the transcription of eight nitrogen metabolic pathway genes (i.e. glnA, amt, ansP, nirB, nirD, glnD, glnK and narK3), which are closely related to glutamine/glutamate biosynthesis and, thus, regulate biofilm formation. CONCLUSION: This study provides insights into the mechanisms of M. abscessus biofilm formation and its resistance to antibiotics.

Role of antibiotics in Milligan-Morgan hemorrhoidectomy for Grade III to IV Hemorrhoids: A randomized clinical trial.

PURPOSE: This study was mainly to compare the safety and long-term clinical efficacy of using intravenous antibiotics in Milligan Morgan hemorrhoidectomy for Grade III to IV Prolapsing Hemorrhoids. METHODS: This was a parallel group, 3-arm, randomized clinical trial to evaluate the efficacy of intravenous prophylactic antibiotics. A total of 150 consecutive patients undergoing Milligan Morgan hemorrhoidectomy (MMH) in a tertiary hospital for grade III/IV hemorrhoids from January 2020 to August 2022 were enrolled. Patients were randomly assigned to three groups using a computer-generated table. Group A did not receive any prophylactic antibiotic, group B received 2 g I/V Cefoxitin Sodium before the induction of anesthesia, and group C received 2 g I/V Cefoxitin Sodium before the induction of anesthesia and 6 h after operation. RESULTS: There was no significant difference in measured VAS values on the 1st day,3rd day and 7th day after surgery (p> 0.05). Compared with VAS values on the 1st day postoperatively, these values got decreased on the 3rd day and 7th day after surgery (p< 0.05). In addition, there was no significant difference among the first defecation time, wound edema, bleeding, urinary retention after surgery (p> 0.05). There was no significant difference in the outcome comparison between all 3 groups' basal and the 3rd day postoperatively no matter in WBC, NUET% or CRP (p> 0.05). However, compared with basal, the WBC, NUET%,CRP(p< 0.05) of group A and group B on the 3rd day postoperatively got rised, the rate of recurrence of hemorrhoids follow-up for 1 year was 1.4%. CONCLUSIONS: Our results suggest that there is no efficacy on intravenous prophylactic antibiotics in Milligan Morgan hemorrhoidectomy.

Association Between Common Empiric Antibiotic Regimens and Clostridioides Difficile Infection in Pediatric Appendicitis.

BACKGROUND: Clostridioides Difficile Infection (CDI) is a serious antibiotic related complication that has been reported among children undergoing treatment of appendicitis. CDI likelihood amongst different empiric antibiotic regimens for appendicitis remains unclear but likely has important implications for antibiotic stewardship. METHODS: A retrospective cohort study of the Pediatric Health Information System was used to examine patients ages 1 through 18 who received operative management of acute appendicitis. Common empiric antibiotic regimens 1) Ceftriaxone & Metronidazole (CM) 2) Piperacillin & Tazobactam (PT) and 3) Cefoxitin were compared. Study outcomes were CDI within 28 days post-appendectomy and 30-day post-appendectomy percutaneous drainage procedures. Subset analyses were repeated to only include hospitals that standardized empiric antibiotic choice. RESULTS: Of 105,911 patients, 220 (0.21 %) developed CDI. CDI was more common in patients that received CM (CM 0.29 % vs PT 0.15 % vs Cefoxitin 0.18 %; P < 0.01). On adjusted analysis, PT was associated with a lower likelihood of CDI (OR, 0.48; 95%CI, 0.31-0.74) compared to CM which was consistent in hospitals with standardized antibiotic choice. Exposure to more unique antibiotic regimens (OR, 1.70; 95 % CI, 1.50-1.93) and higher total antibiotic days (OR, 1.17; 95 % CI 1.13-1.21) were associated with an increased likelihood of CDI. There was no significant difference in the likelihood of post-appendectomy percutaneous drainage between antibiotic regimens. CONCLUSIONS: CDI is rare following appendectomy for pediatric appendicitis. While PT was associated with statistically lower rates of CDI compared to CM, antibiotic stewardship efforts to avoid mixed regimens and decrease overall antibiotic exposure warrant exploration. LEVEL OF EVIDENCE: Level III.

Cefoxitin versus carbapenems as definitive treatment for extended-spectrum ß-lactamase-producing Klebsiella pneumoniae bacteremia in intensive care unit: a propensity-matched retrospective analysis.

BACKGROUND: Despite cefoxitin's in vitro resistance to hydrolysis by extended-spectrum beta-lactamases (ESBL), treatment of ESBL-producing Klebsiella pneumoniae (KP) infections with cefoxitin remains controversial. The aim of our study was to compare the clinical efficacy of cefoxitin as definitive antibiotic therapy for patients with ESBL-KP bacteremia in intensive care unit, versus carbapenem therapy. METHODS: This retrospective study included all patients with monomicrobial bacteremia hospitalized in intensive care unit between January 2013 and January 2023 at the University Hospital of Guadeloupe. The primary outcome was the 30-day clinical success defined as a composite endpoint: 30-day survival, absence of relapse and no change of antibiotic therapy. Cox regression including a propensity score (PS) and PS-based matched analysis were performed for endpoint analysis. RESULTS: A total of 110 patients with bloodstream infections were enrolled. Sixty-three patients (57%) received definitive antibiotic therapy with cefoxitin, while forty-seven (43%) were treated with carbapenems. 30-day clinical success was not significantly different between patients treated with cefoxitin (57%) and carbapenems (53%, p = 0.823). PS-adjusted and PS-matched analysis confirmed these findings. Change of definitive antibiotic therapy was more frequent in the cefoxitin group (17% vs. 0%, p = 0.002). No significant differences were observed for the other secondary endpoints. The acquisition of carbapenem-resistant Pseudomonas aeruginosa was significantly higher in patients receiving carbapenem therapy (5% vs. 23%, p = 0.007). CONCLUSIONS: Our results suggest that cefoxitin as definitive antibiotic therapy could be a therapeutic option for some ESBL-KP bacteremia, sparing carbapenems and reducing the selection of carbapenem-resistant Pseudomonas aeruginosa strains.

Prevalence and antibacterial resistance patterns of uropathogenic staphylococci in Casablanca, Morocco.

INTRODUCTION: The purpose of this research is to evaluate the resistance profile of uropathogenic staphylococci bacteria in Casablanca, Morocco. METHODOLOGY: In this retrospective cross-sectional research carried out from January 2017 to December 2020, isolation and identification were carried out according to the usual techniques in medical microbiology. Staphylococcus aureus isolates were confirmed by polymerase chain reaction (PCR) amplification of the nuc gene, and the antibiogram was performed according to the guidelines of the Antibiogram Committee of the French Society of Microbiology (CA-SFM 2021). The susceptibility of uropathogenic staphylococci to vancomycin was determined with broth microdilution following the recommendations of the Clinical and Laboratory Standards Institute. The mecA gene was tested on phenotypically cefoxitin-resistant S. aureus isolates by PCR. RESULTS: The prevalence of urinary tract infections (UTIs) was 18% (772/4374). UTIs were more common in females (n = 483, 63%) than males (n = 289, 37%). Among the Gram-positive bacteria isolated (198, 25.65%), the prevalence of staphylococci was (130/198, 65.66%). Among staphylococcal species identified, coagulase-negative staphylococci (CoNS) were more prevalent (112/130, 86.15%), and Staphylococcus saprophyticus was the most frequently isolated CoNS (46/112, 41.07%). Additionally, there were several S. aureus strains (18/130, 13.85%). Forty-four percent of S. aureus isolates (n = 8) were resistant to cefoxitin and also harboured the mecA gene. All S. aureus isolates were susceptible to linezolid, cotrimoxazole and vancomycin. CONCLUSIONS: The prevalence and antibacterial resistance patterns of uropathogenic staphylococci in this study, with a high percentage of methicillin resistance, require careful consideration of antimicrobial therapy for staphylococcal UTIs.

Impact of Prophylactic Antibiotic Selection on the Prevention and Bacterial Flora of Surgical Site Infections After Colorectal Surgery.

Background: Deep incisional and organ/space surgical site infections (SSIs) after colorectal surgery are associated with adverse outcomes. Multiple antibiotic regimens are recommended for peri-operative prophylaxis, with no particular regimen preferred over another. We compared the prophylaxis regimens used in patients with and without SSIs, and the impact of regimens on the flora involved in SSIs. Patients and Methods: Information was extracted from the National Healthcare Safety Network databank of patients undergoing colorectal surgery from 2015 to 2022 in a large public healthcare system in New York City. Patients with SSIs were identified, and controlling for nine variables, propensity score matching was used to create a matched control group without SSIs. Prophylactic regimens were compared between the matched groups with and without SSIs. Also, for the patients with SSIs, the impact of the prophylactic regimen on the subsequent pathogens involved the infection was examined. Results: A total of 275 patients with SSIs were compared to a matched cohort without SSIs. The prophylactic regimens were extremely similar between the SSI and control groups. Among the patients who developed SSIs, more patients who received cefoxitin had emergence of select cephalosporin-resistant Enterobacterales and Bacteroides spp. when compared with those who received ß-lactam-ß-lactamase inhibitors. Conclusions: The distribution of surgical prophylaxis regimens was remarkably similar between patients developing serious SSIs and a closely matched cohort that did not develop an SSI. However, given the downstream effects of more resistant and anaerobic flora should an infection develop, use of cefoxitin should be re-evaluated as a prophylactic agent.

Screening the NCI diversity set V for anti-MRSA activity: cefoxitin synergy and LC-MS/MS confirmation of folate/thymidine biosynthesis inhibition.

IMPORTANCE: New antibacterial agents are urgently needed to counter increasingly resistant bacteria. One approach to this problem is library screening for new antibacterial agents. Library screening efforts can be improved by increasing the information content of the screening effort. In this study, we screened the National Cancer Institute diversity set V against methicillin-resistant Staphylococcus aureus (MRSA) with several enhancements. One of these is to screen the library before and after microsomal metabolism as means to identify potential active metabolites. A second enhancement is to screen the library in the absence and presence of sub-minimum inhibitory concentration levels of another antibiotic, such as cefoxitin in this study. This identified four agents with synergistic activity with cefoxitin out of 16 agents with good MRSA activity alone. Finally, active agents from this effort were counter-screened in the presence of thymidine, which quickly identified three folate/thymidine biosynthesis inhibitors, and also screened for bactericidal vs bacteriostatic activity.

Antibiotic Resistance Profiles and Molecular Characteristics of blaCMY-2-Carrying Salmonella enterica Serovar Albany Isolated from Chickens During 2013-2020 in South Korea.

The production of ß-lactamase by nontyphoidal Salmonella has become a public health issue throughout the world. In this study, we aimed to investigate the antimicrobial resistance profiles and molecular characteristics of ß-lactamase-producing Salmonella enterica serovar Albany isolates. A total of 434 Salmonella Albany were obtained from feces and carcasses of healthy and diseased food-producing animals [cattle (n = 2), pigs (n = 3), chickens (n = 391), and ducks (n = 38)] during 2013-2020. Among the 434 Salmonella Albany isolates, 3.7% showed resistance to cefoxitin, and all the cefoxitin-resistant isolates were obtained from chickens. Moreover, Salmonella Albany isolates demonstrated high resistance to nalidixic acid (99.3%), trimethoprim/sulfamethoxazole (97.9%), ampicillin (86.6%), chloramphenicol (86.6%), and tetracycline (85.7%), as well as higher rates of multidrug resistance were detected in cefoxitin-resistant isolates compared to cefoxitin-susceptible isolates. All cefoxitin-resistant isolates harbored CMY-2-type ß-lactamase and belonged to seven different pulsotypes, with type IV-b (43.75%) and IV-a (25%) making up the majority. In addition, genes encoding cefoxitin resistant of all blaCMY-2-harboring Salmonella Albany isolates were horizontally transmitted to a recipient Escherichia coli J53 by conjugation. Furthermore, 93.75% (15/16) of conjugative plasmids harboring blaCMY-2 genes belong to ST12/CC12-IncI1. Genetic characteristics of transmitted blaCMY-2 genes were associated with ISEcp1, which can play an essential role in the effective mobilization and expression of these genes. Salmonella Albany containing blaCMY-2 in chickens can potentially be transferred to humans. Therefore, it is necessary to restrict antibiotic use and conduct continuous monitoring and analysis of resistant bacteria in the poultry industry.

Remarkable antibiofilm activity of ciprofloxacin, cefoxitin, and tobramycin, by themselves or in combination, against enteroaggregative Escherichia coli in vitro.

Enteroaggregative Escherichia coli (EAEC), a biofilm forming pathogen, causes acute and persistent diarrhea worldwide, requiring antimicrobial therapy in severe or persistent cases. To determine the susceptibility of EAEC biofilm to antimicrobials, as single-agent or combined therapy, biofilm formation was investigated using EAEC clinical strains via peg lid. Of the 78 initially analyzed strains, 35 could form biofilms, 15 (42.9%; 15/35) were resistant to at least 1 tested antimicrobial and 20 (57.1%) were susceptible to all of them in the planktonic form. The biofilms of these susceptible strains were challenged against chosen antimicrobials, and displayed resistance to tetracycline, trimethoprim-sulfamethoxazole, chloramphenicol, ampicillin, cefotaxime, ceftriaxone (85%-100%), tobramycin (25%), cefoxitin (20%), and ciprofloxacin (5%). Moreover, ciprofloxacin combined with ampicillin, and tobramycin eradicated the biofilm of 2 of the 4 tested strains. Ciprofloxacin, cefoxitin, and tobramycin maintained their activity well against EAEC biofilm, suggesting their possible effectiveness to treat diarrhea caused by biofilm-forming EAEC strains.

In vitro efficacy of humanized regimen of flomoxef against extended-spectrum ß-lactamase-producing Escherichia coli and Klebsiella pneumoniae.

This study compared the efficacy of flomoxef with other ß-lactam antibiotics against extended-spectrum ß-lactamases (ESBL)-producing bacteria of clinical relevance. First, the prevalence and ß-lactamase genotypes of ESBL-producing strains among Escherichia coli and Klebsiella pneumoniae isolates collected in Japan from 2004 to 2018 were investigated. High MIC90 values (>64 µg/mL) of ceftriaxone, cefepime, and ceftazidime and low MIC90 values (≤0.06-2 µg/mL) of flomoxef, cefmetazole, and meropenem against both species were observed. Second, a chemostat model was used to analyze the efficacy of humanized regimens of three oxacephem/cephamycin antibiotics (flomoxef, cefmetazole, cefoxitin) and two other antibiotics (meropenem and piperacillin/tazobactam) in suppressing the growth of five ESBL-producing E. coli and two K. pneumoniae strains. Flomoxef, piperacillin/tazobactam, and meropenem showed good bactericidal effects with >4 log10 CFU/mL reduction without bacterial regrowth at 24 h even when the MIC of test isolates was >MIC90. Cefmetazole and cefoxitin resulted in regrowth of test isolates with MIC ≥MIC90 at 24 h. Cefmetazole, cefoxitin, flomoxef, and meropenem showed increased MICs for regrown samples. A clear relationship between the proportion of time that the free drug concentration exceeded the MIC (%fT>MIC) and antibiotic efficacy was found for flomoxef, cefoxitin, and cefmetazole, and flomoxef had the highest %fT>MIC, whereas discrepancies between Clinical and Laboratory Standards Institute breakpoint and bactericidal activity were observed for cefmetazole. Flomoxef was effective in preventing the growth of all ESBL-producing strains, even those with an MIC eight times the MIC90. Thus, flomoxef may be a good alternative to meropenem in context of carbapenems sparing stewardship.

Profiling of antibiotic resistance among uropathogens isolated from patients attending Kericho County Referral Hospital.

Introduction: urinary tract infection (UTI) comes second after respiratory infections in most communities and hospital settings, affecting people of all ages. Frequent use of antibiotics to manage UTI has resulted in development of resistance, calling upon policymakers to fast-track and enforce policies that guide the use of antibiotics in the country. This study intended to determine the current antibiotic resistance to uropathogens among patients attending Kericho County Referral Hospital. Methods: three hundred urine samples from eligible participants were cultured and bacteria colonies identified using biochemical tests. Antibiotic sensitivity was done using Kirby Bauer disk diffusion method on Mueller Hinton Agar. Results: the aetiological agents of UTI were Staphylococcus aureus, Enterococci faecalis, E. coli, Proteus spp and Klebsiella pneumonia. Antibiotic resistance was observed among these uropathogens to commonly used antibiotics namely; ampicillin (84.3%), azithromycin (71.9%) and augmentin (69.8%). However, there were some bacteria that were susceptible to all or some commonly used antibiotics. There was moderate resistance to norfloxacin (43%) except in Staphylococcus aureus which showed 64% resistance. The isolates showed less resistance to cefoxitine (13.2%), gentamycin (11.6%) and ciprofloxacin (10%). While most bacteria showed multiple resistance to 3 drugs, some showed resistance to at most 5 drugs tested in the study. Conclusion: this study found Staphylococcus aureus to be the predominant aetiological agent of UTI. Cefoxitine, gentamycin and ciprofloxacin are good therapeutic choices for confirmed recurrent UTI when culture results are unavailable. There is need to have regular screening of aetiological agents of UTI and their resistance to antimicrobials.

Pathogenic bacteria recovered from Gene X-pert tuberculosis-negative adult patients in Gondar, Northwest Ethiopia.

INTRODUCTION: Lower respiratory tract infections (LRTIs) caused by drug-resistant pathogenic bacteria is a major problem in developing countries including Ethiopia. Therefore, this study aimed to determine the pathogenic bacteria and their antimicrobial susceptibility patterns among Gene X-pert tuberculosis-negative adult patients with clinically suspected LRTIs at the University of Gondar Comprehensive Specialized Referral Hospital, Gondar, Northwest Ethiopia. METHODS: This institutional-based cross-sectional study was conducted from February 01 to March 15, 2020. Socio-demographic data were collected by using a structured questionnaire. A total of 254 sputum specimens were collected from Gene X-pert tuberculosis-negative patients. Bacterial recovery was performed using blood, chocolate, and MacConkey agar plates. Bacterial isolates were identified based on Gram staining, colony characteristics, and biochemical reactions. Antimicrobial susceptibility testing was performed using the Kirby-Bauer disk diffusion method. Methicillin resistance of S. aureus was confirmed using cefoxitin (30 µg). Descriptive statistics were calculated for each variable and results are shown in tables and figures. RESULTS: In this study, the overall sputum culture positivity rate was 145/254 (57.1%). Gram-negative bacteria 111 (64.9%) were predominant compared to Gram-positive bacteria 60 (35.1%). Of the 145 culture-positive cases, 26 (14.8%) had poly-bacterial infections. S. aureus 40 (66.7%) was the predominant Gram-positive bacterium whereas K. pneumoniae 33 (29.7%), was the most isolated Gram-negative bacterium. Bacterial species, such as S. aureus were sensitive to ciprofloxacin 38/40 (95.0%), gentamicin 37/40 (92.5%), cefoxitin 36/40 (90.0%), and clindamycin 34/40 (85.0%). The proportion of Methicillin-resistant S. aureus was low, 4(10.0%). S. pneumoniae was sensitive to chloramphenicol 8/9 (88.9%) and resistant to ciprofloxacin 6/9 (66.7%). K pneumoniae, P. aeruginosa, E. coli, Serratia species, and H. influenzae also demonstrated high levels of resistance to ampicillin at rates of 21/33 (63.6%), 8/8 (100.0%), 15/17 (88.2%), 7/10 (70.0%), and 6/6 (100.0%), respectively. CONCLUSION: This study revealed a higher burden of Gram-negative and Gram-positive pathogenic bacterial agents, which is responsible for LRTs. Therefore, routine sputum culture identification and antibiotic susceptibility testing should be performed in Gene X-pert tuberculosis-negative patients.

Association Between Biliary Pathogens, Surgical Site Infection, and Pancreatic Fistula: Results of a Randomized Trial of Perioperative Antibiotic Prophylaxis in Patients Undergoing Pancreatoduodenectomy.

OBJECTIVE: To establish the association between bactibilia and postoperative complications when stratified by perioperative antibiotic prophylaxis. BACKGROUND: Patients undergoing pancreatoduodenectomy experience high rates of surgical site infection (SSI) and clinically relevant postoperative pancreatic fistula (CR-POPF). Contaminated bile is known to be associated with SSI, but the role of antibiotic prophylaxis in mitigation of infectious risks is ill-defined. METHODS: Intraoperative bile cultures (IOBCs) were collected as an adjunct to a randomized phase 3 clinical trial comparing piperacillin-tazobactam with cefoxitin as perioperative prophylaxis in patients undergoing pancreatoduodenectomy. After compilation of IOBC data, associations between culture results, SSI, and CR-POPF were assessed using logistic regression stratified by the presence of a preoperative biliary stent. RESULTS: Of 778 participants in the clinical trial, IOBC were available for 247 participants. Overall, 68 (27.5%) grew no organisms, 37 (15.0%) grew 1 organism, and 142 (57.5%) were polymicrobial. Organisms resistant to cefoxitin but not piperacillin-tazobactam were present in 95 patients (45.2%). The presence of cefoxitin-resistant organisms, 92.6% of which contained either Enterobacter spp. or Enterococcus spp., was associated with the development of SSI in participants treated with cefoxitin [53.5% vs 25.0%; odds ratio (OR)=3.44, 95% CI: 1.50-7.91; P =0.004] but not those treated with piperacillin-tazobactam (13.5% vs 27.0%; OR=0.42, 95% CI: 0.14-1.29; P =0.128). Similarly, cefoxitin-resistant organisms were associated with CR-POPF in participants treated with cefoxitin (24.1% vs 5.8%; OR=3.45, 95% CI: 1.22-9.74; P =0.017) but not those treated with piperacillin-tazobactam (5.4% vs 4.8%; OR=0.92, 95% CI: 0.30-2.80; P =0.888). CONCLUSIONS: Previously observed reductions in SSI and CR-POPF in patients that received piperacillin-tazobactam antibiotic prophylaxis are potentially mediated by biliary pathogens that are cefoxitin resistant, specifically Enterobacter spp. and Enterococcus spp.

Subspecies Distribution and Antimicrobial Susceptibility Testing of Mycobacterium abscessus Clinical Isolates in Madrid, Spain: a Retrospective Multicenter Study.

Mycobacterium abscessus (MABS) is the most pathogenic and drug-resistant rapidly growing mycobacteria. However, studies on MABS epidemiology, especially those focusing on subspecies level, are scarce. We aimed to determine MABS subspecies distribution and its correlation with phenotypic and genotypic antibiotic profiles. A retrospective multicenter study of 96 clinical MABS isolates in Madrid between 2016 to 2021 was conducted. Identification at the subspecies level and resistance to macrolides and aminoglycosides were performed by the GenoType NTM-DR assay. The MICs of 11 antimicrobials tested against MABS isolates were determined using the broth microdilution method (RAPMYCOI Sensititer titration plates). Clinical isolates included 50 (52.1%) MABS subsp. abscessus; 33 (34.4%) MABS subsp. massiliense; and 13 (13.5%) MABS subsp. bolletii. The lowest resistance rates corresponded to amikacin (2.1%), linezolid (6.3%), cefoxitin (7.3%), and imipenem (14.6%), and the highest to doxycycline (100.0%), ciprofloxacin (89.6%), moxifloxacin (82.3%), cotrimoxazole (82.3%), tobramycin (81.3%), and clarithromycin (50.0% at day 14 of incubation). Regarding tigecycline, although there are no susceptibility breakpoints, all strains but one showed MICs ≤ 1 µg/mL. Four isolates harbored mutations at positions 2058/9 of the rrl gene, one strain harbored a mutation at position 1408 of the rrl gene, and 18/50 harbored the T28C substitution at erm(41) gene. Agreement of the GenoType results with clarithromycin and amikacin susceptibility testing was 99.0% (95/96). The rate of MABS isolates showed an upward trend during the study period, being M. abscessus subsp. abscessus the most frequently isolated subspecies. Amikacin, cefoxitin, linezolid, and imipenem showed great in vitro activity. The GenoType NTM-DR assay provides a reliable and complementary tool to broth microdilution for drug resistance detection. IMPORTANCE Infections caused by Mycobacterium abscessus (MABS) are increasingly being reported worldwide. Identifying MABS subspecies and assessing their phenotypic resistance profiles are crucial for optimal management and better patient outcomes. M. abscessus subspecies differ in erm(41) gene functionality, which is a critical determinant of macrolide resistance. Additionally, resistance profiles of MABS and the subspecies distribution can vary geographically, highlighting the importance of understanding local epidemiology and resistance patterns. This study provides valuable insights into the epidemiology and resistance patterns of MABS and its subspecies in Madrid. Elevated resistance rates were observed for several recommended antimicrobials, emphasizing the need for cautious drug use. Furthermore, we assessed the GenoType NTM-DR assay, which examines principal mutations in macrolides and aminoglycosides resistance-related genes. We observed a high level of agreement between the GenoType NTM-DR assay and the microdilution method, indicating its usefulness as an initial tool for early initiation of appropriate therapy.