Staphylococcus in sludge                                                MRSA articles

Ian Pepper who runs the Arizona Water Quality Center continues to claim that there is no evidence that s.
aureus can be found in land applied sewage sludges.  He claims (falsely) that S.aureus is only found in
sewage and untreated sludge.

For example, the 2002 NAS biosolids report included this sentence by Ian Pepper:

"There are no publications documenting S.aureus in biosolids."

In 2003,  Pepper and Gerba co-authored the Rusin paper claiming that S.aureus does not exist in biosolids.
Pepper's  insistence that S.aureus is not present in sludge is directly aimed at discrediting the  Lewis et al
research which found a higher proportion of S.aureus infections among sludge-exposed neighbors who
got ill or died.  Here is what I posted to a EPA docket on pathogen risks: Page 15: The exclusion of Staphylococcus aureus from consideration is not based on facts. It is
based on a paper by  Rusin et al  which ignores EPA’s own  fact sheets and other scientific information  
that indicate the presence of S.aureus in processed sludges.  It appears that the Rusin paper was
commissioned and cited  in an attempt to discredit David Lewis’ published  sludge exposure studies.   
Although Rusin’s reply to Lewis’s published comment is included in the referenced literature, Lewis’ and
Gattie’s  response, is not; so we include it here in its entirety:

   Comment on  “ Evidence for the Absence of Staphylococcus aureus in the Land Applied Biosolids.”
 Rusin  et al. (1 and in ref 2) dismissed processed sewage sludges as a source of Staphylococcus aureus
infections and inferred that we proposed that processed sewage sludges are a primary source of S.
aureus.  In our studies (3, 4), we concluded that chronic irritation of the eyes, skin, mucous membranes,
and respiratory system by irritant chemicals associated with sewage sludge (e.g., bacterial toxins, lime,
organic amines, ammonia) rendered residents prone to infections from all sources, community and
environmental.   Rusin et al. (1) therefore improperly concluded that they disproved our hypothesis by
showing that processes used to treat sewage sludge effectively eliminate S. aureus.
 While reporting that they could only recover 8.7% of the S. aureus added to sewage sludge samples,
Rusin, et a. (1) failed to recognize the significance of this finding.   They assumed that the 91% of
unrecoverable S. aureus cells were as susceptible to disinfection as the recovered cells.   In fact, most of
the S. aureus they added was unrecoverable because cells become embedded in organic matter, lipid
particles, and other components of the sludge from which they are difficult to recover.
 For the same reason most S. aureus cells cannot be recovered by standard isolation techniques, they are
also less exposed to chemical and physical disinfection processes.   We discussed this problem in Envir.
Sci. Technol. and elsewhere (4-7).   The authors, in other words, only tracked the easily extractable S.
aureus cells from the exposed surfaces of organic aggregates, which are most susceptible to
disinfection.   Like trichinae embedded in pork, it is oftentimes the difficult-to-extract pathogens associated
with organic matter taken into the body and released during digestion or other bodily processes that lead
to infection.
 Establishing the absence of an organism is difficult by any means.   Looking at the easily extractable
portion of a population in small volumes of sludges and extrapolating the results to millions of tons of the
material produced each year provides little, if any, insight.
 Finally, Rusin et al. (1) concluded that staphylococci found in processed sewage sludges by other
researchers were probably non-aureus.   They offered no explanation, however, as to why S. aureus, which
is adept at survival in the environment, should be more susceptible to disinfection than any other
Staphylococcus species when subjected to any of the very dissimilar processes used to treat sewage
For references see  pages 2-5.

In 2005  J.Ghosh in a very thorough study on  bioaerosols originating at a  site  where sludge was applied,
found S.aureus surviving longer than any other  other airborne bacteria:  

18. Ghosh Jaydeep.2005. Bioaerosols generated from biosolids applied farm fields in Wood County,


Removal of phosphate in a sequencing batch reactor by Staphylococcus auricularis


A sequencing batch reactor (SBR) was used to remove phosphate in biological wastewater treatment as an alternative
to the activated sludge process, in order to improve the low removal efficiency of phosphate and the operational
instability. After a cycle of 2 h anaerobic and 4 h aerobic conditions, phosphate removal was optimized. The removal
efficiencies of 5 and 50 mg phosphate l–1 by Staphylococcus auricularis under repeated anaerobic and aerobic
conditions were above 90%. These results showed that a long adaptation time, one of the major problems in biological
phosphate removal process, was overcome by SBR.
Biotechnology Letters,  Volume 22, Number 19 / October, 2000

Polyphosphate accumulation by bacteria isolated from activated sludge

Staphylococcus aureus
Staphylococcus spp.
Staphylococcus epidermidis

Lötter (1985) reported gram-negative organisms to be the dominant organisms in the activated sludge system. Results
illustrated in Fig. 2 indicate the predominance of gram-positives in the sludge, found to be 42% of the total poly-P
population. These results support work by Brodisch and Joyner (1983) who reported the predominance of gram-positive
organisms throughout their laboratory-scale activated sludge system. They reported the gram-positive population to be
34.5% in the aerobic zone. The figure also indicates that
Staphylococcus spp. were the predominant gram-positives,
forming 40% of the gram-positive population isolated from the sludge followed by Streptococcus spp. (30%),
Micrococcus spp. (20%) and Bacillus sp. (10%). Bacillus cereus, Micrococcus spp., Staphylococcus epidermidis and
Streptococcus spp. showed reasonably high phosphate-accumulating ability in consecutive descending order
respectively (Table 1). This suggests that gram-positive organisms can perform similarly (i.e. accumulate phosphate) to
gram-negatives if subjected to appropriate conditions

Water SA Vol. 25 No. 2 April 1999

Antibacterial Activity of Chitosan Solutions for Wound Dressing
Chitosan has found wide application in the biomedical field due to its interesting biological properties that include:
biocompatibility, biodegradability, hemostatic activity and bacteriostatic effect. In this present study, antibacterial activity
of chitosan solutions for wound dressing were investigated against
Staphylococcus aureus (isolated from an
activated sludge)
and Escherichia coli (ATCC 25922) that are potential wound pathogens. Moreover, the effects of
plasticizer addition and chitosan concentration on antibacterial activity of chitosan solutions were also evaluated.
According to the antibacterial activity study, chitosan solutions, plasticized or not, showed inhibitory activity against
Escherichia coli. However, they did not inhibit Staphylococcus aureus growth, possibly because this bacterium strain
would become resistant due to mutations caused by industrial effluent exposure.
Macromolecular Symposia, 7 Feb 2007, Volume 245-246, Issue 1 , Pages 515 - 518

Airborne coagulase negative staphylococci produced by a sewage treatment plant

Since some coagulase-negative staphylococci species are involved in clinical and environmental situations, the authors
carried out a study on the spread of these bacteria in the air of a sewage treatment plant. For these purposes a total of
196 samples were taken from 16 sampling stations, 11 during the day and 5 at night (only at 4 points), using the settle
plate technique. Altogether 13 species of
coagulase negative staphylococci were isolated: S. haemolyticus, S.
xylosus and S. cohnii were particularly common. Station no. 2 (an area almost always kept closed containing the fine
screens) was found to be the most contaminated. The presence of
coagulase negative staphylococci was favoured
by high temperatures and low humidity. No differences were found due to variations in wind speed and direction or
between day and night.
International Journal of Hygiene and Environmental Health, Volume 204, Issue 4, 2001, Pages 231-238

Microorganisms in the Air Over Wastewater Treatment Plants  

We present the results of investigations of microorganisms present in aerosol emitted by selected devices of two
mechanical-biological wastewater treatment plants (“Debogorze” and “Gdańsk-Wschód”). In 2002, 5 series of
measurements were conducted at each of the plants. The samples of air were collected by means of sedimentation
method (PN-89/Z-04008/08) and by means of filtration method, using an air sampler produced by Merck. Apart from
measurements of microbiological analyses, consisting of determinations of the total number of psychrophillic and
mezophillic bacteria,
manitol-positive and manitol-negative staphylococcus, hemolysing staphylococcus,
Pseudomonas fluorescens, coliform bacteria and the number of spores of phycomycetes, weather conditions were also
monitored. The most numerous microorganisms in the monitored air were psychrophillic bacteria and spores of
phycomycetes. The number of psychrophillic bacteria varied in the wide range from 14 to 5255 CFU/m3, the number of
mezophillic bacteria changed from 1 to 1324 CFU/m3, the number of
staphylococcus – from 1 to 150 CFU/m3, the
numbers of Pseudomonas fluorescens and the coliforms varied from a few to 50 CFU/m3 and the spores of
phycomycetes varied from a few to 5,250 CFU/m3 of air (collected by means of Merck air sampler). It was found out that
in both plants the main sources of microorganisms were sludge recirculation chambers and sand traps. The air around
aeration chambers of activated sludge contained similar numbers of microorganisms as the background. It was proved
that the sampling method is of critical effect on measurement results. The number of microorganisms detected in the
samples collected by means of sedimentation method was by one order of magnitude higher than in the samples
collected by means of filtration method (using air sampler), allowing for strict control of the filtered air volume.
Polish Journal of Environmental Studies Vol. 13, No. 5 (2004), 537-542

Studying the activated sludge of municipal and industrial wastewater, a great number of microorganisms has been
isolated and the genera found most frequently are as follow: Pseudomonas, Bacillus, Achromobacter, Enterococcus,
Acinetobacter, Aeromonas, Alcaligenes, Arthrobacter, Escherichia, Salmonella, Proteus, Streptococcus,
Staphylococcus, Micrococcus, Corynebacterium, Clostridium, Penicillium [1, 12, 13, 15, 16, 19, 20].

1.  Arhipchenko, I. A., 1980. Microbiologia, 49, (3), 531-533. (in Russian).
12. Mendes, B., M. Nascimento, 1991. Zentralbl. Hyg. Umweltmed., 190, (5-6), 471-473.
13. Mitchel, R., 1976. Microbiology of polluted water, Moskva: Medicina (in Russian).
15. Petrovic, O., M. Gantar, M. Bokorov, 1989. Biol. Waster., 30, (2), 81-88.  
16. Ponamareva, L. N., A. V. Nazarenko, T. A. Ivanova, V. P. Krunchak, 1994. Conference. "Introduction of    
Microorganisms in Environment.", Moskva, 81-83 (in Russian).
19.  Wilcox, D. P., E. Chang, K. L. Dickson, K. R. Johansson, 1983. Appl. Environ. Microbiol., 46, (2), 406-410.  
20. Zorenzana, Z. M., E. Becates, M. Z, Zopez, 1992. 6th International Symposium on Microbiology and
Ecology, 6-11         Sept., Barcelona, Spain, abstracts, 224.
Journal of Culture Collections, National Bank for Industrial Microorganisms and Cell Cultures,
Vol. 1, Num. 1, 1995, pp. 18-22

Investigation of the microbial contribution to nutrient removal in an activated sludge wastewater treatment
Report No 822/1/00


Biological nitrogen removal

Findings confirm the existence of a diverse community of heterotrophic bacteria involved in nitrogen removal during
wastewater treatment of which Pseudomonas spp. show significant involvement. Numerous heterotrophic bacteria were
found to be capable of nitrification.

heterotrophic isolates demonstrated direct oxidation of ammonium to nitrates with little or no nitrite accumulation;
different patterns of nitrification behaviour were noted amongst heterotrophic nitrifiers with some displaying potential
nitrification/denitrification behaviour;
Staphylococcus and Micrococcus spp. showed significant involvement in nitrification along with Streptococcus,
Pseudomonas and Bacillus spp.
Foundation for Water Research