Etiology of bacteremia

Antimicrobial susceptibility testing of anaerobic bacteria causing bacteremia: A 13-year (2010-2022) retrospective study in a tertiary hospital

Infections from anaerobic microorganisms result from breached mucosal barriers, posing a significant mortality risk. A retrospective study at Hospital Universitario La Paz (Madrid) from 2010 to 2022 analyzed 491 (6.17 %) anaerobic bacteremia cases out of 7956 significant bacteremia cases among 171,833 blood culture requests. Bacteroides fragilis was the most frequently isolated species (28.3 %), followed by Clostridium perfringens (13.6 %). B. fragilis showed good susceptibility to amoxicillin/ clavulanic acid (86 %), piperacillin/tazobactam (86 %), and metronidazole (87.7 %). In general, non-fragilis Bacteroides species showed low susceptibility to penicillin (7 %), amoxicillin (17.5 %), and clindamycin (64.9 %). Of our 13 non-perfringens Clostridium isolates, four exhibited resistance to penicillin and four showed resistance to clindamycin. Lactobacillus species were highly susceptible to antibiotics tested. Prevotella spp. showed low susceptibility to penicillin (20 %), amoxicillin (20 %), and clindamycin (40 %). The study contributes valuable data for monitoring and improving anaerobic bacteremia treatment.

Yield of Anaerobic Blood Cultures in Pediatric Emergency Department Patients

BACKGROUND

Anaerobic bacteremia is rare in children and current recommendations advocate against the routine use of anaerobic cultures in children. However, the incidence of anaerobic bacteremia and the utility of anaerobic blood cultures in children have not been assessed in recent years. Our pediatric emergency department (PED) policy still supports the use of both aerobic and anaerobic blood cultures in all cases of suspected bacteremia. This allowed us to re-evaluate the yield of anaerobic cultures in PED settings.

METHODS

Retrospective data of all blood cultures taken in the PED in a single tertiary center from 2002 to 2016 were collected. The incidence and characteristics of children with positive anaerobic blood cultures were assessed. Risk factors for anaerobic bacteremia were defined.

RESULTS

Of the 68,304 blood culture sets taken during the study period, 971 (1.42%) clinically significant positive cultures were found. Pathogenic obligatory anaerobic bacteria were isolated in 33 (0.05%) cultures. The leading risk factors for anaerobic bacteremia were head and neck abscess and intra-abdominal infection. Of all the true positive cultures, 187 (22%) were only detected in the anaerobic culture and would have otherwise been missed.

CONCLUSIONS

True anaerobic bacteremia is extremely rare in children admitted to the PED. Nevertheless, using anaerobic cultures may increase the overall yield of blood cultures.

Tracking laboratory contamination by using a Bacillus cereus pseudoepidemic as an example

From 1 March to 31 May 1990, Bacillus cereus was recovered from 24 of 5,534 (0.49%) blood cultures and 22 of 1,088 (2.02%) other body fluid cultures. The rarity of this organism as a pathogen and comparison with previous baseline rates led to the conclusion that it was a pseudoepidemic involving some form of culture contamination. Generalized precautions taken without specific knowledge of the contaminant source reduced the recovery rate of the organism. Recovery rates for the organism returned to normal baseline prevalence after environmental cultures and epidemiological analysis led to the sterilization of a contaminated water bath used for boiling thioglycollate media. The problems encountered in this investigation are examined, and a systematic approach to clinical laboratory epidemiology is outlined.

Bacteraemia in man and animals: an overview

Bacteraemia signifies invasion of the bloodstream by bacteria. In most systemic infections in man and animals, bacteria enter the blood at some stage during the infection and are rapidly distributed throughout the body. A wide variety of organisms have been associated with bacteraemia. Prompt detection of the aetiological agents of bacteraemia is of prime importance in clinical microbiology. There are no defined recommendations for blood cultures in animals but both conventional and improved methods are available for detection of bacteraemia in man. The consequences of bacteraemia are as diverse as the potential aetiological agents. Monoclonal antibodies to the core glycolipid (lipid A) seems very promising for the treatment of bacteraemia and septic shock caused by Gram-negative bacteria in man and animals.

Frequency of R factor-mediated multiple drug resistance in Klebsiella and Aerobacter

A comparative study was done on the transfer frequency of R factors from 90 strains of multiple drug-resistant Aerobacter and 81 strains of Klebsiella to Escherichia coli CSH-2 (F(-), met(-), pro(-), Nal-r). The most common resistance patterns for the Aerobacter isolants were ampicillin streptomycin chloramphenicol tetracycline and ampicillin streptomycin chloramphenicol tetracycline kanamycin neomycin; for the Klebsiella isolants, the most common resistance pattern was ampicillin kanamycin streptomycin tetracycline chloramphenicol neomycin. R factors were isolated from 14.1% of the Aerobacter strains; 61.5% of these R factors harbored R determinants for ampicillin streptomycin tetracycline. R factors were isolated from 79.1% of the Klebsiella strains; four R factors were isolated with significant frequency; streptomycin chloramphenicol kanamycin neomycin, 37.5%; ampicillin streptomycin tetracycline kanamycin neomycin, 14.1%; ampicillin streptomycin tetracycline, 12.5%; and streptomycin chloramphenicol tetracycline, 12.5%.Chloramphenicol, kanamycin, and neomycin resistance was rarely transferred from the Aerobacter strains, although over 50% of the clinical isolants possessed resistance to these antibiotics. In contrast, over 75% of the Klebsiella strains transferred resistance to chloramphenicol, kanamycin, neomycin. Highest frequency of transferred resistance to individual drugs in the Aerobacter strains was to streptomycin (14.8%), whereas in the Klebsiella group resistance to four drugs was transferred at a very high frequency: streptomycin (80.8%), chloramphenicol (78.5%), kanamycin (76.4%), and neomycin (75.9%).