Culturing and Maintaining Clostridium difficile in an Anaerobic Environment

Summary

Clostridium difficile is a pathogenic bacterium that is a strict anaerobe and causes antibiotic associated diarrhea (AAD). Here, methods for isolating, culturing and maintaining C. difficile vegetative cells and spores are described. These techniques necessitate an anaerobic chamber, which requires regular maintenance to ensure proper conditions for optimal C. difficile cultivation.

Abstract

Clostridium difficile is a Gram-positive, anaerobic, sporogenic bacterium that is primarily responsible for antibiotic associated diarrhea (AAD) and is a significant nosocomial pathogen. C. difficile is notoriously difficult to isolate and cultivate and is extremely sensitive to even low levels of oxygen in the environment. Here, methods for isolating C. difficile from fecal samples and subsequently culturing C. difficile for preparation of glycerol stocks for long-term storage are presented. Techniques for preparing and enumerating spore stocks in the laboratory for a variety of downstream applications including microscopy and animal studies are also described. These techniques necessitate an anaerobic chamber, which maintains a consistent anaerobic environment to ensure proper conditions for optimal C. difficile growth. We provide protocols for transferring materials in and out of the chamber without causing significant oxygen contamination along with suggestions for regular maintenance required to sustain the appropriate anaerobic environment for efficient and consistent C. difficile cultivation.

Introduction

Clostridium difficile is a Gram-positive, spore-forming bacterium that is an obligate anaerobe and a potentially fatal gastrointestinal pathogen of humans and animals. Initially described in 1935 as a commensal organism found in fecal samples from newborns¹, C. difficile was later demonstrated to be the causative agent of pseudomembranous colitis associated with antibiotic treatment². C. difficile infections (CDI) are typically preceded by antibiotic treatment which results in the disruption of the normal colonic flora, creating a niche for C. difficile to thrive². C. difficile is tra....

Protocol

Note: C. difficile is a human and animal pathogen that can cause gastrointestinal disease. Experiments involving C. difficile must be performed with appropriate biosafety precautions (BSL-2).

1. Anaerobic Chamber Use and Maintenance

C. difficile is a strict anaerobe and is extremely sensitive to even low concentrations of oxygen in the atmosphere. Therefore, a controlled, anaerobic environment is needed for its successful manipulation. The use of an anaerobic chamber (Figure 1A) provides the most stable environment and the ideal conditions for effective cultivation of

Results

An example of C. difficile grown on BHIS and Columbia anaerobic sheep blood agar media can be seen in Figure 2. C. difficile forms irregular colonies that are flat and possess a ground-glass appearance which is evident on both media. Here, an erythromycin-sensitive clinical isolate of C. difficile, 630E³⁰, is grown on BHIS agar, an enriched, non-selective medium, for 24 hr at 37 °C (Figure 2A). Colonies on Columbia anaerobic sheep blood agar appear s.......

Discussion

The methods described here allow for simple and quick recovery of C. difficile from a variety of fecal samples, including humans, mice and hamsters, as well as the long-term storage of C. difficile as glycerol or spore stocks. C. difficile can be a difficult organism to cultivate, but careful maintenance of an anaerobic environment and the application of aseptic techniques can provide for robust growth and a reduction in contamination.

Anaerobic chambers: Considerations.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Proteose Peptone no. 2	BD	212120
Na2HPO4	Fisher	S373
KH2PO4	Fisher	BP362
NaCl	Fisher	S27
MgSO4 (anhydrous)	Fisher	M65
á´…-Fructose	Fisher	L96
Sodium taurocholate	Sigma	T4009
á´…-cycloserine	Sigma	C6880
Cefoxitin	Fluka	C4786
Brain heart infusion medium	BD	237300
Proteose Peptone	BD	211684
(NH4)2SO4	Sigma	A5132
Tris base	Fisher	BP152
Agar	BD	214010
L-cysteine	Sigma	C7755
BactoPeptone	BD	211684
Columbian sheep blood agar	Fisher	L21928
NaCl	Fisher	S27
KCl	Fisher	P217
Glycerol	Fisher	BP2291
Sterile inoculating loops	Fisher	22363596
Sterile swabs	Fisher	1495990
Coy Vinyl Anaerobic Chamber and Accessories	Coy Laboratory Products, Inc	Customer Specified	These items are custom ordered per laboratory needs
Materials
TCCFA agar Proteose peptone no. 2 (Difco) 40 g Na2HPO4 5 g KH2PO4 1 g NaCl 2 g MgSO4 (anhydrous) 0.1 g Fructose 6 g Agar 20 g Bring to 1 L with deionized water and autoclave at 121 °C for 20 min to sterilize. After autoclaving, add: 10 ml of 10% (w/v) sodium taurocholate, filter-sterilized (dissolve in water; final concentration, 0.1%) 25 ml of 10 mg/ml á´…-cycloserine, filter-sterilized (dissolve in water; final concentration, 250 μg/ml) 1.6 ml of 10 mg/ml cefoxitin, filter-sterilized (dissolve in water; final concentration, 16 μg/ml) BHIS Medium Brain heart infusion 37 g Yeast extract 5 g For plates, add 15 g agar. Bring to 1 L with deionized water and autoclave at 121 °C for 20 min to sterilize. Optional (add after autoclaving): 3 ml of 10% (w/v) L-cysteine (dissolve in water; final concentration, 0.03%) 10 ml of 10% (w/v) sodium taurocholate (dissolve in water; final concentration, 0.1%) SMC Sporulation Medium BactoPeptone 90 g Protease peptone 5 g (NH4)2SO4 1 g Tris base 1.5 g Agar 15 g Bring to 1 L with deionized water and autoclave at 121 °C for 20 min to sterilize. Optional (add after autoclaving): 3 ml of 10% (w/v) L-cysteine (dissolve in water; final concentration, 0.03%) 70:30 Medium BactoPeptone 63 g Protease peptone 3.5 g Brain heart infusion 11.1 g Yeast extract 1.5 g (NH4)2SO4 0.7 g Tris base 1.06 g For plates, add 15 g agar. Bring to 1 L with deionized water and autoclave at 121 °C for 20 min to sterilize. After autoclaving, add 3 ml of 10% (w/v) L-cysteine (final concentration, 0.03%). Blood agar The use of premade Columbia anaerobic sheep blood agar plates (Fisher Scientific, L21928)35 is recommended. 1X Phosphate buffered saline (PBS) NaCl 8.01 g KCl 0.2 g Na2HPO4 1.44 g KH2PO4 0.27 g Bring to 1 L with deionized water and adjust pH to 7.4 with HCl. Filter sterilize before use.