Responsible Reporting in Microbiology

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Responsible Reporting in Microbiology

Improving quality of care through better communication

One of the most important functions that a microbiologist performs

is to decide what is clinically relevant regarding specimen work-up,

what organisms to look for and report, what organisms are

pathogenic, and what constitutes normal flora. The microbiologist

should make every effort to make a positive contribution to patient

management by providing straightforward, uncluttered, and easy-to-

understand reports. '

Communication between clinician and microbiologist is the most

effective means of preventing inappropriate use of microbiology

information. Addressing common communication errors between the

medical staff and the microbiology laboratory and suggesting

improvements in reporting practices is the focus of this article.

Inadequate reporting may lead to unnecessary action: Case study 1

A 30-month-okl infant was U-bagged for a urine culture. No

urinalysis was ordered or performed. Culture results were reported

out as 2,000 col/mL (two colonies grew out on blood agar plate) of

Pseudomonas aeruginosa. The clinician admitted the patient to

pediatrics and started her on IV ceftazidime. When the clinician

called the microbiology lab requesting susceptibilities, the urine

sample was retrieved and urinalysis performed with normal results,

even though urinalysis had not been ordered. How could communication

between microbiology and the clinician have been improved? Perhaps

by adding a comment to the culture results:

* " No urinalysis requested. Unable to determine significance of this

isolate. "

or

* " U-bag urine samples are unacceptable specimens for culture due to

contamination from fecal and/or skin flora. "

Reporting without a comment may lead to inappropriate antimicrobial

therapy: Case study 2

Candida glabrata was identified and reported from two sets of blood

cultures from a patient with systemic candidiasis. The patient was

administered fluconazole for 10 days at which time the patient

expired. Subsequently, the isolate was forwarded to a reference lab

for antifungal minimum inhibitory concentrations (MICs), which

confirmed that the isolate was resistant to fluconazole. How could

communication between the microbiology laboratory and the clinician

have been improved?

* By adding a comment to the report:

* " Candida glabrata recovered. (Most C glabrata isolates are

resistant to fluconazole therapy. Fungal susceptibilities available

on request.) " 2

The Gram-stain interpretation

The medical staff needs the laboratorian's help; make the Gram stain

report useful. It is important to convey to the clinician what, if

any, potential pathogen is present to provide an early indication of

the cause of infection for administration of appropriate

antibiotics. The presumptive interpretation of a microorganism is

more useful than a description of the morphology, such as Gram-

negative pleoinorphic coccobacilli. Adding the comment " presumptive

Haemophilus influenzas " is much more helpful.

* Do not report Gram-positive cocci in pairs and lancets from a

sputum Gram stain. Report out Gram-positive cocci (e.g., " suspect

Streptococcus pneumoniae " ). If it looks like S pneumoniae on the

slide, say it. S pneumoniae is extremely fastidious and may be seen

on the Gram smear but may not always grow. So, if it is seen on the

slide hut the culture is negative, make note of it.3

* When interpreting a sputum Gram stain, place importance only on

the predominant organism associated with polymorphonuclear (PMN)

leukocytes.

* Bacteria seen in a Gram stain should be reported presumptively on

the basis of microscopic morphology, e.g.:

* " Gram-positive cocci resembling Streptococcus pneumoniae from

sputum " ;

* " Gram-positive cocci in clusters (presumptive Staphylococcus) " ;

* " Gram-positive cocci in chains (presumptive Streptococcus) " ;

* " Small Gram-negative coccobacilli in sputum (presumptive

Haemophilus) " ; or

* " Mixed flora. "

Sputum cultures - lower respiratory tract

The culture of lower respiratory tract specimens may result in more

unnecessary microbiologie effort than any other type of specimen.4

The goal of clinical laboratories is to eliminate sputum cultures as

much as possible because they typically are not useful. Only accept

for culture those specimens with less than 10 squamous epithelial

cells /LPF.5 If the specimen is rejected, cancel the culture and

bill for the Gram stain. Do not request another specimen, because it

will probably be unacceptable as well.

* Sputum with <25 squamous epithelial cells/low power field (SEC/

LPF) had cultures that correlated with transtracheal aspiration

cultures 79% of the time, whereas a potential pathogen isolated from

sputa with <10 SEC/LPF was 94% predictive ot growth in the

corresponding transtracheal aspirate.6 Importantly, Gram-stained

smears meeting the <10 SEC/LPF acceptance criteria can predict the

etiological agent in pneumonias - documented by recovery from

positive blood cultures.7,8

* Do not work up yeast from a sputum culture. Candida pneumonia is

extremely rare and diagnosis should be made by histopathological

invasion and/or positive blood cultures.9 Play down its importance

in the culture work-up by calling it " yeast " rather than giving it a

specific identification. An exception may be to perform a rapid

urease to rule out Cryptococcus ssp.10

* Use comments when reporting unusual pathogens (e.g., sputum

culture results: " Many Corynebacterium striatum recovered -

predominant organism. " This organism has been increasingly reported

as the etiologic agent of various human infections, including

bacteremic and fatal pleuropulmonary infections.)11

Female genital cultures

* The flora of the female genital tract varies with pH and estrogen

concentration of the mucosa, which depend on the host's age. Work-up

and reporting of organisms indigenous to the female genital tract

(e.g., Enterobacteriacea, group B streptococci in nonpregnancy, non-

group A beta streptococci) may suggest to the physician that the

organism is causing an infection because the laboratory provided an

identification and susceptibility-test result. Moreover, antibiotic

treatment of any component of the normal vaginal flora may actually

lead to overgrowth of Candida species and candidat vulvovaginitis.12

* Do not rely on culture for Gardnerella to diagnose bacterial

vaginosis (BV). Reporting all isolates of Gardnerella from vaginal

cultures is misleading since 50% to 90% of sexually active,

asymptomatic women are colonized with this organism. A properly

examined Gram smear should strongly suggest (or rule out) the

diagnosis of BV.13

Informational fliers featuring new procedures or unusual

microorganisms are an excellent form of communication between the

medical staff and the microbiology lab.

* About 3% to 10% of premenopnusal females are vaginally colonized

with Staphylococcus aureus. If S aureus is reported out from a

genital culture, include the comment: " Patients colonized with this

organism are at greater risk of developing toxic shock syndrome if

they are tampon users. " 14 Do not perform susceptibilities. The

organism is colonizing the genital tract, not invading healthy

tissue.

Throat cultures

* The majority (80%) of cases of pharyngitis are caused by viruses,

whereas 15% to 20% are caused by group A streptococci

(Streptococcuspyogenes), the only cause of pharyngitis for which

antimicrobial therapy is clearly indicated.15

* Except for the well-documented historic role of H influenzae as a

cause of epiglottitis, there is no scientific evidence that H

influenzae, S pneumonias, or S aureus causes sore throat. Moreover,

colonization of the pharynx with S aureus and enteric bacilli

increases after antibiotic therapy.16

* Do not perform routine throat cultures. Perform organism- specific

testing (e.g., throat culture for Neisseria gonorrhoeae, throat

culture for yeast, or throat culture for Arcanobacterium

haemolyticum). If a throat culture is ordered specifically (a

written request for full throat culture), report the presence or

absence of group A streptococci and A haemolyticum.

Throat cultures - First, do no harm

* If methicillin-resistant S aureas (MRSA) is reported out, other

than a screen for carriage, the patient will be prescribed IV

vancomycin.

* If Neisseria meningitidis is reported out, it is likely that the

clinician will perform a lumbar puncture.

* If H influenzae is reported out, it is likely that the patient

will be prescribed amoxacillin/clavulanate.17

* Recovery of S aureus, H influenzae, enterics, S pneumoniae, and

other bacteria in cases of acute pharyngitis most likely means there

is an underlying viral infection.

Busy sputum Gram-stain report:

More user-friendly report:

Nasopharyngeal (NP) cultures -Why do them?

* As many as 75% of healthy individuals harbor S pneumoniae and H

influenzae in the upper respiratory tract.

* As many as 50% of healthy individuals harbor Moraxella catarrhalis

in the upper respiratory tract.

* As many as 90% of healthy individuals harbor S aureus in the upper

respiratory tract.

* When NP cultures from patients <12 years old grow S pneumoniae, H

influenzae, or M catarrhalis, add the following

comment: " Nasopharyngeal culture should not be used for the

microbiological diagnosis of otitis media because of the high

prevalence of asymptomatic carriage of this organism.

Tympaiiocentesis is the recommended procedure for collecting

specimens that will yield reliable microbiological results to guide

\therapy in otitis media. " 18

* NP cultures for Nmeningitidis: " Prophylaxis should be based on

recent epidemiological exposure, not NP culture. "

Blood cultures

* The use of antibiotic removal devices only adds confusion. If a

patient has been started on antibiotics and follow-up blood cultures

are drawn with antibiotic removal devices (resin), they may become

positive - which the clinicians may interpret as meaning that the

antibiotic the patient is on is not working. In addition, more

coagulase-negative staphylococcal contaminants may be detected in

media containing resins and activated charcoal than in media without

these additives.19

* Add a comment to a presumptive contaminant to eliminate

unnecessary antimicrobial therapy and lengthened hospital

stays: " Susceptibilities will not be performed because the clinical

significance of coagulase-negative staphylococci (or Bacillus ssp.,

diphtheroids, Corynebacterium, Propionibacterium ssp.) isolated from

a single blood culture is undetermined. Please consult microbiology

if further work-up is needed. "

Stool cultures

* The cost of performing a stool examination on every patient for

all potential pathogens is prohibitive. It is particularly important

to quickly identify those cases of diarrheal disease caused by

agents that require prompt therapy, other than oral rehydration, in

order to be effective.

* As a general rule, primary culture media should provide for

adequate recovery of Salmonella, Shigella, Campylobacter ssp., and

Escherichia coli 0157:H7. The media selected should also be adequate

to recover less-common enteric pathogens, such as Yersinia

enterocolitica, Plesiomonas shigelloides, and Aeromonas species

(e.g., blood agar).

* It is incorrect to issue a report " no enteric pathogens isolated " ;

rather, the report should state " culture negative for Salmonella,

Shigella, Campylobacter, and E.coli 0157:H7, " if these are the

agents that are routinely looked for in a stool specimen. Also

provide comments when reporting out uncommon agents of diarrheal

illness: e.g., " Plesiomonas shigelloides isolated - this organism is

associated with diarrheal illness that is usually self- limiting.

Antimicrobial therapy may be indicated in severe or prolonged

gastroenteritis. Contact microbiology if susceptibility studies are

needed. " 20

Comment for E coli 0157:H7

Antimicrobial agents should not routinely be used to treat

gastroenteritis due to E.coli 0157:H7 because they may increase the

risk of hemolytic uremic syndrome. Antimicrobial agents do not

accelerate recovery.21

Urine cultures

Urinary tract infection is one of the most commonly encountered

acute infectious diseases and accounts for the majority of the

workload in clinical microbiology laboratories. Because of the large

workload, aggressive and unnecessary work-up of what often are

insignificant organisms can waste laboratory resources, confound the

physician, and ultimately result in unnecessary antimicrobial

therapy, which leads to resistance.

Rule 1: Routine handling of a urine specimen for culture should

include determination of the presence or absence of pyuria by the

leukocyte esterasc (LE) test or microscopic urinalysis. Since

urinary tract infections (UTIs) are very rare in the absence of

pyuria, urine cultures can be restricted to specimens that are LE-

positive or show >5 white blood cells on urinalysis.22 With the

advent of computer-generated laboratory reports, instant

availability of the urinalysis result can provide useful information

to guide accurate culture work-up and appropriate antimicrobial-

susceptibility testing.

Rule 2: Add comments to unusual microorganisms: e.g., " >100,000

col/mL Corynebacterium urealyticum. (This organism is an etiologic

agent involved in alkaline-encrusted cystitis, a severe UTI that is

difficult to treat. Because the organism is highly resistant to most

antimicrobial agents, vancomycin is recommended. See patient's urine

pH = 8.5.) " 23

Take an active role; make a difference

A microbiologist's role is significant because he produces so much

of the information that is used to make medical decisions. It is,

therefore, important that his reports are readable, accurate, and

credible. He is the expert, and both physicians and patients rely on

him.

Reports generated by the microbiology lab should not confuse the

clinician, but instead should include useful, uncluttered, and

informative information.

Urinary tract infection is one of the most commonly encountered

acute infectious diseases and accounts for the majority of the

workload in clinical microbiology laboratories.

How to confuse a physician:

* Make lab reports hard to follow.

* Report an MIC on an organism, even if it is not necessary.

* Report everything that grows.

* Do identification and MICs on all anaerobes as if it really

matters.

* Give bacteria a new name every year.

* Do susceptibility testing on blood-culture contaminants.

* Report dangerous organisms without a comment.

* Suggest to a physician that an old procedure is being dropped.

Errors regularly committed by laboratories

1. Lack of knowledge of what to look for (e.g., neglecting to look

for acid-fast bacteria in a specimen from an infected breast

prosthesis).

2. Too rigid an adherence to routine without taking note of

individual circumstances.

3. Reporting everything that grows, and leaving it up to the

clinician to decide on the significance.

4. Ignoring all isolates except those commonly considered important

to disease.

Do not perform routine throat cultures; perform organism- specific

testing.

References

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2. Nguyen MH, Peacock JE Jr, AJ, et al. The changing face of

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3. Bartlett RC, Mazens-Sullivan MF, Lerer TJ. Differentiation of

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5. Sharp SE, ed. Cumitech 7B - Lower Respiratory Tract Infections.

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2214.

By Colleen K. Gannon, MT(AMT), HEW

For 20 years, Colleen K. Gannon, MT(AMT), HEW, has been the section

head of the microbiology department of MidMichigan Medical Center,

which services the 308-bed nonprofit hospital, in addition to two

other area hospitals, several nursing homes, satellite laboratories,

and clinics.

Copyright Publishing Dec 2004

Source: Medical Laboratory Observer; MLO