Elsevier

Anaerobe

Volume 59, October 2019, Pages 49-53
Anaerobe

Antimicrobial susceptibility of anaerobic bacteria
Antimicrobial susceptibility and clinical findings of significant anaerobic bacteria in southern Spain

https://doi.org/10.1016/j.anaerobe.2019.05.007Get rights and content

Highlights

  • Metronidazole was not universally active against all anaerobes.

  • Resistance rates to carbapenems and amoxicillin-clavulanate were very low.

  • Resistance rates of almost all genera to clindamycin were very high.

  • Routine antimicrobial susceptibility testing is highly recommended.

Abstract

The objectives of this study were to report on the antimicrobial susceptibility of 276 clinically significant anaerobic bacteria belonging to the major genera isolated between May 2017 and November 2018 in a tertiary hospital in Granada (Spain) and to describe key clinical features of the patients. Species identification was performed by MALDI-TOF MS. Antimicrobial susceptibility tests were performed against penicillin, amoxicillin-clavulanic, imipenem, meropenem, moxifloxacin, clindamycin, metronidazole, vancomycin, and piperacillin-tazobactam using the gradient diffusion technique and EUCAST breakpoints (except for moxifloxacin). The most frequent anaerobes were Bacteroides (29.7%; n = 82), Clostridioides difficile (15.9%, n = 44), Prevotella (10.8%, n = 30), and Propionibacterium (10.7%, n = 25). Metronidazole was not universally active against all genera tested, and some isolates showed resistance to this drug. Almost all tested anaerobes were susceptible to carbapenems and amoxicillin-clavulanate except for Clostridioides difficile (resistance rate of 94%) and Bacteroides (19%), respectively. High overall resistance rates to clindamycin were observed, especially for genera Finegoldia (54%), Bacteroides (49%), and Prevotella (40%). Resistance rates to carbapenems and amoxicillin-clavulanate were very low for the majority of tested genera but were high for Clostridioides difficile and Bacteroides spp., respectively. Resistance to clindamycin was very high, especially for Bacteroides, Finegoldia magna, Prevotella and Peptoniphilus. Routine antimicrobial susceptibility testing for anaerobes contributes information on the global situation and allows empirical therapies to be selected in accordance with local data on resistant strains.

Introduction

Anaerobic bacteria are common pathogens in humans. Although most clinically significant anaerobes are involved in mixed infections alongside aerobic bacteria, they can be responsible for severe disease in certain circumstances, such as in blood infections or when present in normally sterile body sites. Infections due to anaerobic isolates may sometimes be missed because of the special measures required for their transportation. Other critical factors for the successful isolation of these microorganisms in the microbiology laboratory include incubation in anaerobic atmosphere, the use of specialized culture media, and prolonged culture [1].

Antimicrobial susceptibility testing of anaerobic bacteria is performed by a minority of laboratories, including only 21% of laboratories in the USA [2,3], while only 19% of laboratories in Scotland routinely carry out anaerobe identification or antimicrobial susceptibility [4]. Current recommendations emphasize that antimicrobial susceptibility testing of anaerobic isolates is only needed for severe infections or for epidemiological studies [5,6], although a rise in the resistance of anaerobes to some antimicrobial agents may indicate a greater need for this testing [5].

Few data are available on the resistance of anaerobes worldwide, and the objective of this study was to report the percentage resistance of clinically significant anaerobes in a tertiary hospital in Southern Spain and the key clinical characteristics of these patients.

Section snippets

Clinical features

This was a prospective study of microbiological data that were recorded in a file after obtaining the results, while the patient data were obtained from our Laboratory Information System (LIS).

Data were gathered on: age and sex, infection site, infection type (polymicrobial vs. monomicrobial), risk factors, underlying diseases, clinical manifestations, laboratory findings, treatment, and outcome. For Clostridioides difficile infection, information was also recorded on recurrence, ribotype,

Clinical characteristics of patients

The study included 243 patients, 51% (n = 124) males, with a mean age of 54.3 years (1-94). Table 1, Table 2 exhibit their clinical characteristics. Samples were from abdominal abscesses (32%, n = 78), stool samples (C. difficile) (18.1%; n = 44), skin and soft tissues (17.6%, n = 43), and urogenital sites (10.6%, n = 26), among others (Table 3).

Isolated bacteria

The study included 276 non-repetitive clinically relevant anaerobic strains: 53.8% (n = 125) were Gram-negative bacilli, with 29.7% (n = 82) being

Discussion

This surveillance study established the antimicrobial susceptibility of 276 clinically relevant anaerobic bacteria isolated in the routine testing of samples from patients in a tertiary-care hospital in Southeast Spain. The bacteria belonged to all major genera of anaerobes isolated from patients with different types of infection, localized in the abdomen in the majority of cases and accompanied by pain and fever. Blood test markers, especially C-reactive protein levels, were elevated in 136

Conflict of interest

Authors declare no conflict of interest.

Funding

None.

References (28)

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