Journal Club

In this feature, a panel of IDSA members identifies and critiques important new studies in the current literature that have a significant impact on the practice of infectious diseases medicine.

• Septic Shock Caused by Multidrug-Resistant A. baumannii Versus Carbapenemase-Producing K. pneumoniae
• A Bacterial Cancer Clue: Blood Culture Isolates Associated with Colorectal Cancer

Click here for the previous edition of Journal Club. For a review of other recent research in the infectious diseases literature, see “In the Literature,”  by Stanley Deresinski, MD, FIDSA, in each issue of Clinical Infectious Diseases.

Septic Shock Caused by Multidrug-Resistant A. baumanniiVersus Carbapenemase-Producing K. pneumoniae

Reviewed by Zeina Kanafani, MD, MS

Infections caused by multidrug-resistant Acinetobacter baumannii (MDR-AB) and Klebsiella pneumoniae carbapenemase-producing K. pneumoniae (KPC-Kp) are often difficult to diagnose and to treat and are therefore associated with a poor outcome. In a recent study in Antimicrobial Agents and Chemotherapy, investigators from Italy sought to discern characteristics specific to each of these organisms.

Clinical data pertaining to patients with septic shock due to documented MDR-AB (n = 92) or KPC-Kp (n = 128) infection between 2010 and 2015 were retrospectively analyzed. A large proportion of KPC-Kp isolates were resistant to colistin (44.5 percent) compared to only 1.1 percent of the MDR-AB isolates (p < 0.001).

On logistic regression, patients in the KPC-Kp arm were more likely to have been hospitalized within 90 days (odds ratio [OR] 5.01; 95 percent confidence interval [CI] 2.15-11.6; p < 0.001) and to have been colonized at the time of ICU admission (OR 13.8; 95 percent CI 4.3-44.7; p < 0.001), whereas patients in the MDR-AB arm were more likely to have received steroids during their ICU stay (OR 0.1; 95 percent CI 0.04-0.25; p < 0.001). In addition, there was a significant association of KPC-Kp with primary bacteremia (OR 2.3; 95 percent CI 1.1-5.5; p = 0.04). On the other hand, pneumonia as a source of infection was more frequently encountered with MDR-AB (OR 0.4; 95 percent CI 0.18-0.96; p = 0.04).

Concerning patient outcomes, septic shock due to MDR-AB infection was associated with higher mortality compared to KPC-Kp (84.8 percent vs. 44.5 percent; p < 0.001). Independent predictors of 30-day mortality with KPC-Kp were isolation of a colistin-resistant strain (OR 25.1; 95 percent CI 4.9-127.8; p < 0.001), whereas improved survival at 30 days was associated with the use of two or more active drugs for initial (OR 0.19; 95 percent CI 0.04-0.85; p = 0.03) or definitive therapy (OR 0.02; 95 percent CI 0.004-0.14; p < 0.001). In the MDR-AB group, 30-day mortality was associated with age > 60 years (OR 1.01; 95 percent CI 1.001-1.03; p = 0.04) and a simplified acute physiology score (SAPS II) > 45 points (OR 1.02; 95 percent CI 1.003-1.04; p = 0.02).

This study confirms previous reports of high mortality with MDR-AB and illustrates peculiar characteristics of septic shock due to MDR-AB and KPC-Kp, thereby aiding in the management of these challenging infections.

(Russo et al. Antimicrob Agents Chemother. 2018;62(6):e02562-17.)

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A Bacterial Cancer Clue: Blood Culture Isolates Associated with Colorectal Cancer

Reviewed by Manie Beheshti, MD

Bacteremia with certain microbes (e.g., Streptococcus gallolyticus, formerly Streptococcus bovis) has long been associated with colorectal cancer (CRC), the world’s third commonest malignancy. The identification of other pathogens with a similar association could provide useful information for clinicians. 

Using a large population clinical database of 41 public hospitals, which provide over 90 percent of Hong Kong’s inpatient care, researchers recently conducted a 10-year retrospective analysis to evaluate the association between microbes recovered from blood cultures and CRC. Published in Gastroenterology, this study included 13,096 patients with positive blood cultures with propensity score matched cases based on age, sex, and comorbidities. Subsequent diagnoses of biopsy-proven CRC were recorded and hazard ratios (HRs) were calculated. Those less than 18 years of age or those with a prior diagnosis of cancer were excluded.

CRC was significantly associated with bacteremia due to Streptococcus gallolyticus (HR = 5.73), Bacteroides fragilis (HR = 3.85), Fusobacterium nucleatum (HR = 6.89), and Clostridium septicum (HR = 17.1). The authors reported novel associations with Clostridium perfringens (HR = 2.29) and Gemella morbillorum (HR = 15.2). Perhaps of equal interest are the bacterial species with no significant association to colorectal cancer, such as S. intermedius, S. agalactiae, S. dysgalactiae, S. mitis, and S. pyogenes (see supplementary table 2 in the article). While S. bovis bacteremia was associated with early-stage CRC, no other significant associations with tumor stage and location were found. 

This study provides clinicians with useful data adding to the information gleaned from a positive blood culture. Specific organisms can help identify those patients who may need CRC screening.

(Kwong et al. Gastroenterology. Published online: 2 May 2018.)

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