Do antimicrobial susceptibility patterns of colonic isolates of Bacteroides species change after antibiotic prophylaxis with cefoxitine during elective abdominal surgery?

Gastrointestinal surgery and the gut microbiome: a systematic literature review

BACKGROUND/OBJECTIVES

The impact of gastrointestinal surgery on the profile of the human gut microbiome is not fully understood. This review aimed to identify whether there is a change to the profile of the gut microbiome as a result of gastrointestinal surgery.

SUBJECTS/METHODS

In August 2018, a systematic literature search was conducted in Medline, PreMedline, Embase, CINAHL and The Cochrane Register of Clinical Trials, identifying and critically appraising studies which investigated changes to gut microbiome pre- and post-gastrointestinal surgery.

RESULTS

Of 2512 results, 14 studies were included for analysis. All studies reported post-surgical change to the microbiome. In 9 of the 14 studies, prevalence of specific bacteria had significantly changed after surgery. Improved outcome was associated with higher levels of beneficial bacteria and greater microbiome diversity post-surgery.

CONCLUSION

There were methodological limitations in the included studies leading to uncertainty regarding the impact of gastrointestinal surgery alone on the microbiome profile. An ideal future model for research should encompass case-controlled or cohort design with longer term follow-up in a homogeneous patient group. Future research should seek to clarify the gold standard testing method and standardised timing for post-surgical microbiome sample collection. It is imperative that controls for confounders be put in place to attempt to identify the true association between gastrointestinal surgery and changes to gut microbiome.

Antimicrobial resistance in the Bacteroides fragilis group in faecal samples from patients receiving broad-spectrum antibiotics

Members of the Bacteroides fragilis group are opportunistic pathogens and cause severe infections including bacteraemia. As increased levels of antimicrobial resistance in B. fragilis group bacteria can be detected years after administration of specific antibiotics, monitoring antimicrobial susceptibility in the gut microbiota could be important. The objectives of this study were to 1) investigate the distribution of species and the occurrence of reduced antimicrobial susceptibility in the B. fragilis group from patients treated at departments with a high level of antibiotic use, 2) to determine the prevalence of the carbapenem resistance gene cfiA in B. fragilis in this patient group, and 3) to determine the association between previous antibiotic treatment and reduced susceptibility to clindamycin, meropenem, metronidazole, and piperacillin-tazobactam. Consecutive faecal samples (n = 197) were collected from patients at the departments of haematology, oncology, and infectious diseases at Odense University Hospital, Denmark. Three colonies from each sample were identified by Matrix Assisted Lazer Desorption Ionization Time of Flight Mass Spectrometry and isolates were screened for resistance to clindamycin, meropenem, metronidazole, and piperacillin-tazobactam. B. fragilis isolates were tested for the cfiA metallo-beta-lactamase gene. Fisher's Exact test was used to test for correlation between antimicrobial exposure and reduced susceptibility. A total of 359 isolates were tested for reduced susceptibility. Of these 28%, 5%, <1%, and 11% were intermediate susceptible or resistant to clindamycin, meropenem, metronidazole, and piperacillin-tazobactam respectively. Three metronidazole resistant Bacteroides spp. were isolated. The proportion of B. fragilis belonging to division II (cfiA+) was 5.3%. Previous exposure to meropenem was associated with reduced susceptibility to meropenem (p= 0.001). In conclusion, antimicrobial resistance is prevalent and the distribution of species appears to be affected in the B. fragilis group from patients receiving broad-spectrum antibiotics, with meropenem exposure being associated with meropenem resistance.

Fecal carriage of extended-spectrum and AmpC β-lactamase-producing Enterobacteriaceae in surgical patients before and after antibiotic prophylaxis

The impact of antibiotic prophylaxis on fecal carriage of ESBL-/AmpC-/carbapenemase-producing Enterobacteriaceae (CPE) was investigated. Patients admitted for elective surgery or diagnostic procedure in a Department of Surgical Gastroenterology (SG) (n= 450) and Orthopedic Surgery (OS) (n= 300) provided a fecal swab at admission and responded to a questionnaire on possible exposures. SG patients received gentamicin/penicillin G (±metronidazole); OS patients received cefuroxime. Two days after surgery a second swab was taken. From SG patients, 6% of first swabs and 9% of second swabs were positive for ESBL-/AmpC-producers. A similar carriage rate was observed in OS patients (6% and 8%, respectively). No CPE were detected. Escherichia coli was the predominant species and blaCTX-M-15 (29% and 22%) and blaCTX-M-14 (11% and 17%) were the most prevalent ESBL genotypes among SG and OS patients. Two different prophylactic antibiotic regimens had no impact on carriage rates. Previous hospitalization and antimicrobial treatment were associated with carriage for SG patients.

[Perioperative antibiotic prophylaxis]

In times of growing bacterial resistance against antimicrobiotic drugs the broad prescription of antibiotics in human medicine must be carefully considered. The perioperative antibiotic treatment is in the center of that conflict. On the one hand an efficient pathogen reduction for the preemptive treatment of infectious complications is desired but on the other hand it is suspected that this promotes the selection of multiresistant pathogens which could lead to an increase of more complicated nosocomial infections. The aim of this article is a critical appraisal of this subject on the basis of the 2012 guidelines of the German working group of Hygiene in Hospital and Practice (AWMF) and the 2010 recommendations of the Paul-Ehrlich-Gesellschaft.

Antimicrobial resistance and prevalence of resistance genes in intestinal Bacteroidales strains

OBJECTIVE

This study examined the antimicrobial resistance profile and the prevalence of resistance genes in Bacteroides spp. and Parabacteroides distasonis strains isolated from children's intestinal microbiota.

METHODS

The susceptibility of these bacteria to 10 antimicrobials was determined using an agar dilution method. β-lactamase activity was assessed by hydrolysis of the chromogenic cephalosporin of 114 Bacteriodales strains isolated from the fecal samples of 39 children, and the presence of resistance genes was tested using a PCR assay.

RESULTS

All strains were susceptible to imipenem and metronidazole. The following resistance rates were observed: amoxicillin (93%), amoxicillin/clavulanic acid (47.3%), ampicillin (96.4%), cephalexin (99%), cefoxitin (23%), penicillin (99%), clindamycin (34.2%) and tetracycline (53.5%). P-lactamase production was verified in 92% of the evaluated strains. The presence of the cfiA, cepA, ermF, tetQ and nim genes was observed in 62.3%, 76.3%, 27%, 79.8% and 7.8% of the strains, respectively.

CONCLUSIONS

Our results indicate an increase in the resistance to several antibiotics in intestinal Bacteroides spp. and Parabacteroides distasonis and demonstrate that these microorganisms harbor antimicrobial resistance genes that may be transferred to other susceptible intestinal strains.

Pancreaticoduodenectomy for periampullary malignancies: the effect of bile colonization on the postoperative outcome

OBJECTIVES

The presence of bacteria in the bile of patients undergoing biliary tract surgery has been proposed as associated to an increased incidence of postoperative complications. The present study was designed to determine whether colonization of the bile has an adverse effect in terms of postoperative infectious or noninfectious complications and mortality in a homogenous population of patients suffering from periampullary region malignancies, who all underwent resectional (curative) procedures.

MATERIALS AND METHODS

Between January 1997 and December 2002, 115 patients (n = 115) suffering from periampullary region malignancies underwent resectional procedures. Fifty-two of the above patients were referred having undergone preoperative internal biliary drainage. During the operation, bile was routinely isolated from the common bile duct and was sent for culture and sensitivity. Based on the bile culture results, the patients were divided in sterile and colonized group and were retrospectively compared in terms of postoperative outcome and mortality.

RESULTS

Of the 115 bile cultures, 67 were colonized with bacteria and 48 were sterile. Postoperatively, 40 patients developed 35 noninfectious and 21 infectious complications. Univariate analysis did not disclose statistically significant differences in overall, noninfectious or infectious morbidity and mortality between the two groups of patients. Although not statistically significant, a higher incidence (22 vs 10%) of postoperative leaks in the colonized group of patients was noticed. Multiple regression analysis disclosed that colonized bile was independently related to the advanced age, preoperative biliary drainage presence, elevated preoperative serum bilirubin levels and low preoperative serum albumin levels but did not predispose to an increased postoperative morbidity, mortality, or reoperation rate.

CONCLUSION

The present study did not conclude in any statistically significant differences in the postoperative infectious and noninfectious morbidity as well as mortality, between colonized and sterile groups of patients who underwent resectional procedures for malignancies of the periampullary region. Although internal biliary drainage introduces microorganisms into the biliary tree, this colonization does not increase the risk of either infectious or noninfectious complications or postoperative death. Thus, the likelihood of bacterobilia should not contraindicate the procedure in selected cases.